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Students can Download Chapter 9 Locomotion and Movement Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 9 Locomotion and Movement

What is locomotion?
The movements result in a change of place or location. Such voluntary movements are called locomotion. Walking, running, climbing, flying, swimming are all some forms of locomotory movements.

Locomotory Movements In Lower Organisms

1. Paramoecium, cilia helps in the movement of food through cytopharynx and locomotion.
2. Hydra use its tentacles for capturing its prey and also use them for locomotion.

All locomotions are movements but all movements are not locomotions.

Types Of Movement
The three main types of movements of cells of the human body are

• Amoeboid
• Ciliary
• Muscular.

Muscle
About 40-50 perent of the body weight of a human adult is contributed by muscles. Muscles are classified based on their location, three types of muscles are identified.

1. Skeletal
2. Visceral
3. Cardiac.

1. Skeletal muscles:
They have a striped appearance and called as striated muscles. They are voluntary muscles because their activities are under the voluntary control of the nervous system. They are involved in locomotory actions and changes of body postures.

2. Visceral muscles:

• They are located in the innerwalls alimentary canal, reproductive tract, etc. They are called smooth muscles (non striated muscle).
• Their activities are not underthe voluntary controlcalled as involuntary muscles.
• They helps in transportation of food through the digestive tract and gametes through the genital tract.

3. Cardiac muscles:

• They are found in the muscles of heart. Based on appearance, cardiac muscles are striated and involuntary.
• Skeletal muscle is made of a number of muscle bundles or fascicles held together by a common collagenous connective tissue layer called fascia
• Each muscle bundle contains a number of muscle fibres. Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm.
• Muscle fibre is a syncitium because it contains many nuclei.
• The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the store house of calcium ions.

Structure of Contractile Proteins
Each actin filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.

Acomplex protein Troponin is distributed at regular intervals on the tropomyosin. In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments.

Monomeric proteins called Meromyosins forms one thick filament. Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.

Mechanism of Muscle Contraction
The sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.

1. In the junction, the neurotransmitter (Acetyl choline) is released which generates an action potential in the sarcolemma. This spreads and release of calcium ions into the sarcoplasm.
2. Increase in Ca⁺⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.
3. The energy from ATP hydrolysis is used to bind the myosin head with exposed active sites on actin to form a cross bridge.
4. This pulls the attached actin filaments towards the centre of ‘A’ band. The Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e. contraction.
5. During shortening of the muscle the T bands get reduced, whereas the ‘A’ bands retain the length The myosin, releasing the ADP and P1 goes back to its relaxed state.
6. The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding.
7. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic cisternae resulting in the masking of actin filaments.

This causes the return of ‘Z’ lines back to their original position, i.e., relaxation.

What is muscle fatigue?
Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen causing fatigue. Muscle contains a red coloured oxygen storing pigment called myoglobin. These muscles contain plenty of mitochondria which helps in ATP production.

Hence they are called aerobic muscles. Some of the muscles possess very less quantity of myoglobin and gives whitish appearance . These are the White fibres. Number of mitochondria are also few in them. They depend on anaerobic process for energy.

Seletal System
1. Skeletal system consists of a framework of bones and a few cartilages.

2. Bone and cartilage are specialised connective tissues.

3. The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts. In human beings, this system is made up of 206 bones and a few cartilages. It is grouped into two divisions.

Axial skeleton:

1. It comprises 80 bones distributed along the main axis of the body.
2. The skull, vertebral column, sternum and ribs constitute axial skeleton.

The skull is composed of two sets of bones – Cranial bones are 8 in number. The facial region is made up of 14 skeletal elements which form the front part of the skull.

Diagrammatic view of human skull:
A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.

What is ear ossicles ?
Each middle ear contains three tiny bones – Malleus, Incus and Stapes, collectively called Ear Ossicles.

Vertebral column:
It is formed by 26 serially arranged units called vertebrae and is dorsally placed. Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes. First vertebra is the atlas and it articulates with the occipital condyles. The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused)and coccygeal (1-fused) regions starting from the skull.

Vertebral column (right lateral view) Ribs and rib cage. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.

Sternum:
It is a flat bone on the ventral midline of thorax.
There are 12 pairs of ribs.
1. First seven pairs of ribs are called true ribs. Dorsaily, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.

2. The 8^th, 9^th and 10^th pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral (false) ribs.

3. Last 2 pairs (11^th and 12^th) of ribs are not connected ventrally and are called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage.

Appendicular skeleton:
It includes bones of the limbs alongwith their girdles Each limb is made of 30 bones. The bones of the hand (fore limb) are humerus, radius and ulna, carpals (wrist bones-8 in number), metacarpals (palm bones – 5 in number) and phalanges (digits – 14 in number) Femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – 7 in number), metatarsals (5 in number) and phalanges (digits -14 in number) are the bones of the legs (hind limb).

A cup shaped bone called patella cover the knee ventrally (knee cap). Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton.

Each half of pectoral girdle consists of a clavicle and a scapula. Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs. The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.

Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint. Each clavicle is a long slender bone with two curvatures. This bone is commonly called the collar bone. Pelvic girdle consists of two coxal bones Each coxal bone is formed by the fusion of three bones

1. ilium
2. ischium
3. pubis.

Joints
Joints are points of contact between bones, or between bones and cartilages. The movability of joints vary depending on different factors.
Joints are classified into three,

Disorders Of Muscular And Skeletal System
Myasthenia gravis:
Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Muscular dystrophy:
Progressive degeneration of skeletal muscle mostly due to genetic disorder.

Tetany:
Rapid spasms (wild contractions) in muscle due to low Ca⁺⁺ in body fluid.

Arthritis:
Inflammation of joints.

Osteoporosis:
Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.

Gout:
Inflammation of joints due to accumulation of uric acid crystals.

NCERT SUPPLEMENTARY SYLLABUS
Types of movements: Flagellar movement
The three main types of movements shown by the cells of the human body are amoeboid, ciliary and muscular. Human sperms shows type of movement called the flagellar movement. The flagellum is the propulsion equipment (due to whip like movement of the tail and the middle piece of the sperm) forthe movement of sperm towards the ovum.

Students can Download Chapter 6 Depreciation, Provisions and Reserves Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 6 Depreciation, Provisions and Reserves

Summary:
Meaning of depreciation:
Depreciation is decline in the value of a tangible fixed asset. In accounting depreciation is the process of allocating depreciable cost over useful life of a fixed asset.

Depreciation and similar terms:
Depreciation term is used in the context of tangible fixed assets. Depletion (in the context of extractive industries), and amortisation (in the context of intangible assets) are other related terms.

Factors Affecting Depreciation:

• Wear and Tear due to use and/or passage of time
• Expiration of Legal Rights
• Obsolescence

Importance of depreciation:

• Depreciation must be charged to ascertain true and fair profit or loss.
• Depreciation is a non-cash operating expense.

Methods of charging depreciation:
Depreciation amount can be calculated using:

• Straight line method, or
• Written down value method

Methods of recording depreciation:
In the books of account there are two types of arrangements for recording depreciation on fixed assets.

• Charging depreciation to asset account or
• Creating provision for depreciation/ accumulated depreciation account.

Charging depreciation to asset account:
According to this arrangement depreciation is deducted from the depreciable cost of the asset (credited to the asset account) and charged (or debited) to profit and loss account. Journal entries under this recording method are as follows:

2. Following two entries are recorded at the end of every year.
(a) For deducting depreciation amount from the cost of the asset.

(b) For charging depreciation to profit and loss account

3. Balance Sheet Treatment
When this method is used, the fixed asset appears at its net book value (ie. cost less depreciation charged till date) on the asset side of the balance sheet and not at its original cost (also known as historical cost).

Creating Provision for depreciation account/ Accumulated depreciation Account:
This method is designed to accumulate the depreciation provided on an asset in a separate account generally called “Provision for Depreciation” or “Accumulated Depreciation” account.

The following journal entries are recorded under this method:

2. The following two journal entries are recorded at the end of each year
(a) For crediting depreciation amount to provision for depreciation account.

(b) For charging depreciation to profit and loss account

3. Balance Sheet treatment
In the balance sheet the fixed asset continues to appear at its original cost on the asset side. The depreciation charged till that date appears in the provision for depreciation account, which is shown either on the “liabilities side” of the balance sheet or by way of deduction from the original cost of the asset concerned on the asset side of the balance sheet.

Disposal of Asset:
Disposal of asset can take place either

• At the end of its useful life or
• During the useful life (due to absolescence or any other abnormal factors). In this case the following journal entries are recorded.

1. For the sale of asset as scrap

2. For transfer of balance in asset account

In case, however “the provision for depreciation account” has been in use for recording the depreciation, then before passing the above entries transfer the balance of the provision for depreciation account to the asset account by recording the following journal entry.

Factors affecting the amount of depreciation:

• Depreciation amount is determined by Original cost
• Salvage value, and
• Useful life of the asset

Provisions and Reserves:
A provision is a charge against profit. It is created for a known current liability the amount of which is uncertain. Reserve on the other hand, is an appropriation of profit. It is created to strengthen the financial position of the business.

Types of Reserves:
Reserves may be:

• General reserve and specific reserve;
• Revenue reserve and capital reserve.

Secret Reserve:
When the total depreciation charged is higher than the total depreciable cost, the Secret reserve is created. The secret reserve is not explicitly shown in the balance sheet.

Students can Download Chapter 5 Trial Balance and Rectification of Errors Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 5 Trial Balance and Rectification of Errors

Summary:
Meaning of trial balance:
A statement showing the abstract of the balance (debit/credit) of various accounts in the ledger.

Objectives of trial balance:
The main objectives of preparing the trial balance are:

• To ascertain the arithmetical accuracy of the ledger accounts;
• To help in locating errors; and
• To help in the preparation of the final accounts.

Preparation of trial balance by the balance method:
In this method, the trial balance has three columns. The first column is for the head of the account, the second column for writing the debit balance and the third for the credit balance of each account in the ledger.

Format of a Trial balance
Trial Balance of ………………… as on March 31.2005

It is normally prepared at the end of an accounting year. However, an organisation may prepare a trial balance at the end of any chosen period, which may be monthly, quarterly, half yearly or annually depending upon its requirements.
In order to prepare a trial balance following steps are taken:

• Ascertain the balances of each account in the ledger.
• List each account and place its balance in the debit or credit column as the case may be. (If an account has a zero balance, it may be included in the trial balance with zero in the column for its normal balance).
• Compute the total of debit balances column.
• Compute the total of the credit balances column.
• Verify that the sum of the debit balances equal the sum of credit balances. If they do not tally, it indicates that there are some errors. So one must check the correctness of the balances of all accounts.

It may be noted that all assets expenses and receivables account shall have debit balances whereas all liabilities, revenues and payables accounts shall have credit balances.

Illustrative Trial Balance

Various types of errors:
1. Errors of commission:
Errors caused due to wrong recording of a transaction, wrong totalling, wrong casting, wrong balancing, etc.

2. Errors of omission:
Errors caused due to omission of recording a transaction entirely or partly in the books of account.

3. Errors of principle:
Errors arising due to wrong classification of receipts and payments between revenue and capital receipts and revenue and capital expenditure.

4. Compensating errors:
Two or more errors committed in such a way that they nullify the effect of each other on the debits and credits.

Rectification of errors:
Errors affecting only one account can be rectified by giving an explanatory note or by passing a journal entry. Errors which affect two or more accounts are rectified by passing a journal entry.

Meaning and utility of suspense account:
An account in which the difference in the trial balance is put till such time that errors are located and rectified. It facilitates the preparation of financial statements even when the trial balance does not tally.

Disposal of suspense account:
When all the errors are located and rectified the suspense account stands disposed off.

Students can Download Chapter 4 Bank Reconciliation Statement Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 4 Bank Reconciliation Statement

Summary
Bank Reconciliation Satement
A statement prepared to reconcile the bank balance as per cash book with the balance as per passbook or bank statement, by showing the items of difference between the two accounts.

Causes of difference
Timing of recording the transaction Errors made by business or by the bank.

Need for Reconciliation
It is generally experienced that when a comparison is made between the bank balance as shown in the firm’s cash book, the two balances do not tally. Hence, we have to first ascertain the causes of difference thereof and then reflect them in a statement called Bank Reconciliation Statement to reconcile (tally) the two balances.

In order to prepare a bank reconciliation statement we need to have a bank balance as per the cash book and a bank statement as on a particular day along with details of both the books.

If the two balances differ, the entries in both the books are compared and the items on account of which the difference has arisen are ascertained with the respective amounts involved so that the bank reconciliation statement may be prepared.

Proforma of bank reconciliation statement

It can also be prepared with two amount columns one showing additions (+ column) and another showing deduction (- column).

Proforma of bank reconciliation statement (table form)

Correct cash balance
It may happens that some of the receipts or payments are missing from either of the books and errors, if any, need to be rectified. This arises the need to look at the entries/errors recorded in both statements and other information available and compute the correct cash balance before reconciling the statements.

Students can Download Chapter 2 Theory Base of Accounting Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 2 Theory Base of Accounting

Summary:
Generally accepted Accounting Principles (GAAP):
GAAP refers to the rules or guidelines adopted for recording and reporting to business transactions in order to bring uniformity in the preparation and presentation of financial statements. These principles are also referred to as concepts and conventions.

From the practicality viewpoint, the various terms such as principles, conventions, modifying principles, assumptions, etc., have been used interchangeably and are referred to as basic accounting concepts.

Systems of Accounting:
There are two systems of recording business transactions, i.e., double entry system and single entry system.

Basis of Accounting:
There are two broad approach of accounting are cash basis and accural basis. Under cash basis transactions are recorded only when cash are received or paid, where as under accural basis, revenue or costs are recognises when they Occur rather than when they are paid.

Accounting Standards:
Accounting standards are written statement of uniform accounting rules and guidelines in practice for preparing the uniform and consistent financial statements.

Students can Download Chapter 1 Introduction to Accounting Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 1 Introduction to Accounting

Summary
Meaning of Accounting:
Accounting is a process of identifying, measuring, recording the business transactions and communicating thereof the required information to the interested users.

Accounting as a source of information:
Accounting as a source of information system is the process of identifying, measuring, recording and communicating the economic events of an organization to interested users of the information.

Users of accounting information:
Accounting plays a significant role in society by providing information to management at all levels and to those having a direct financial interest in the enterprise, such as present and potential investors and creditors.

Accounting information is also important to those having an indirect financial interests, such as regulatory agencies, tax authorities, customers, labour unions, trade associations, stock exchanges, and others.

Qualitative characteristics of Accounting:
To make accounting information decision-useful, it should possess the following qualitative characteristics.

• Reliability
• Understandability
• Relevance
• Comparability

The objective of accounting:
The primary objectives of accounting are to:

• Maintain records of business;
• Calculate profit or loss;
• Depict the financial position: and
• Make information available to various groups and users.

Role of accounting:
Accounting is not an end in itself. It is a means to an end. It plays the role of a:

• Language of a business
• Historical record
• Current economic reality
• Information system
• Service to users

Students can Download Chapter 8 Excretory Products and their Elimination Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 8 Excretory Products and their Elimination

What is excretion?
Excretion is the elimination common nitrogenous wastes. Ammonia, urea and uric acid are the major forms of nitrogenous wastes excreted by the animals.

Ammonotelic.ureotelic and urecotelic animals and their excretion:
1. The process of excreting ammonia is Ammonotelism. eg: Many bony fishes, aquatic amphibians and aquatic insects are ammonotelic.

2. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals.

3. Reptiles, birds, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.

Where is urea produced?
Ammonia produced by metabolism is converted into urea in the liver and released into the blood which is filtered and excreted out by the kidneys.

Excretion in lower organisms:

Human Excretory System
In humans, the excretory system consists of

1. A pair of kidneys
2. One pair of ureters
3. A urinary bladder
4. A urethra.

Each kidney of an adult human measures 10 – 12 cm in length, 5 – 7 cm in width, 2 – 3 cm in thickness with an average weight of 120 – 170 g.

1. Centre of the inner concave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter.

2. Innerto the hilum is a broad funnel shaped space called the renal pelvis with projections called calyces.

3. Inside the kidney, there are two zones, an outer cortex and an inner medulla.

4. The medulla is divided medullary pyramids projecting into the calyces.

5. The cortex extends in between the medullary pyramids as renal columns called Columns of Bertini.

6. Each kidney has nearly one million complex tubular structures called nephrons, which are the functional units. A diagrammatic representation of a nephron showing blood vessels, duct and tubule Each nephron has two parts -1 The glomerulus & 2 Renal tubule.

7. Glomerulus is a tuft of capillaries formed by the afferent arteriole – a fine branch of renal artery.

8. Blood from the glomerulus is carried away by an efferent arteriole.

9. The renal tubule begins with a double walled cup-like structure calle Bowman’s capsule, which encloses the glomerulus.

10. Glomerulus alongwith Bowman’s capsule, is called the malpighian body or renal corpuscle

11. The tubule continues further to form a highly coiled network proximal convoluted tubule (PCT).

12. A hairpin shaped Henle’s loop is the next part of the tubule which has a descending and an ascending limb.

13. The ascending limb continues as another highly coiled tubular region called distal convoluted tubule (DCT).

14. The DCTs open into a straight tube called collecting duct, many of which open into the renal pelvis through medullary pyramids in the calyces.

15. The Malpighian corpuscle, PCT and DCT of the nephron are situated in the cortical region of the kidney whereas the loop of Henle dips into the medulla.

Types of Nephrons:
1. In majority of nephrons, the loop of Henle is too short and extends only very little into the medulla. Such nephrons are called cortical nephrons.

2. In some of the nephrons, the loop of Henle is very long and runs deep into the medulla.These nephrons are called juxta medullary nephrons. A minute vessel of capillary network runs parallel to the Henle’s loop forming a ‘LT shaped vasa recta. Vasa recta is absent or highly reduced in cortical nephrons.

Urine Formation
1. It involves three main processes namely, glomerular filtration, reabsorption and secretion

2. The first step in urine formation is the filtration of blood, which is carried out by the glomerulus and is called glomerular filtration.

3. 1100 – 1200 ml of blood is filtered by the kidneys per minute. The glomerular capillary blood pressure causes filtration of blood through 3 layers,

4. The epithelial cells of Bowman’s capsule called podocytes which possess minute spaces called filtration slits.

5. Blood is filtered through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule. It is the process of ultra filtration.

6. The kidneys have efficient mechanism for the regulation of glomerular filtration rate. It is carried out by juxta glomerular apparatus (JGA).JGA is found in the distal convoluted tubule .

7. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal.

8. Nearly 99 percent of the filtrate is reabsorbed by the renal tubules. This process is called reabsorption.

9. For example, substances like glucose, amino acids, Na⁺, etc., in the filtrate are reabsorbed actively whereas the nitrogenous wastes and water are absorbed by passive transport.

10. During urine formation, the tubular cells secrete substances like H⁺, K⁺ and ammonia into the filtrate.

11. Tubular secretion is helpful in the maintenance of ionic and acid-base balance of body fluids.

Function Of The Tubules
Proximal Convoluted Ttubule (PCT):
1. PCT consists of simple cuboidal brush border epithelium which increases the surface area for reabsorption.

2. All essential nutrients, and 70 – 80 per cent of electrolytes and water are reabsorbed by this segment.

3. PCT also helps to maintain the pH and ionic balance of the body fluids. It occurs through selective secretion of hydrogen ions, ammonia and potassium ions into the filtrate and by absorption of HCO₃^– from it.

Henle’s Loop
Function:
It helps to maintain high osmolarity of medullary interstitial fluid. The descending limb of loop of Henle is permeable to water but impermeable to electrolytes. This concentrates the filtrate as it moves down.

The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Therefore, as the concentrated filtrate pass upward, it gets diluted due to the passage of electrolytes to the medullary fluid.

Distal Convoluted Tubule (DCT):
The reabsorption of Na⁺, HCO₃^– and water takes place in this segment. In this segment selective secretion of hydrogen and potassium ions and NH₃ to maintain the pH and sodium-potassium balance in blood.

Collecting Duct:
It extends from the cortex of the kidney to the inner parts of the medulla. Large amounts of water is reabsorbed from this region to produce a concentrated urine. This part maintains pH and ionic balance of blood by the selective secretion of H⁺ and K⁺ ions.

Mechanism Of Concentration Of The Filtrate
The flow of filtrate in the two limbs of Henle’s loop is in opposite directions and thus forms a counter current. The flow of blood through the two limbs of vasa recta is also in a counter current pattern.

The proximity between the Henle’s loop and vasa recta, as well as the counter current in them help in maintaining an increasing osmolarity towards the inner medullary interstitium, i.e. from 300 mOsmolL^-1 in the cortex to about 1200 mOsmolL^-1 in the inner medulla. This gradient is mainly caused by NaCl and urea.

NaCl is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of vasa recta. NaCl is returned to the interstitium by the ascending portion of vasa recta. Similarly, small amounts of urea enterthe thin segment of the ascending limb of Henle’s loop which is transported back to the interstitium by the collecting tubule.

This transport is facilitated by the counter current mechanism This mechanism helps to maintain a concentration gradient in the medullary interstitium. Presence of such interstitial gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine).

Regulation Of Kidney Function
The functioning of the kidneys is influenced by hypothalamus, JGA and to a certain extent, the heart in the body are activated by changes in blood volume.

How can diuresis is prevented in body?
The decrease of fluid from the body can activate these Osmoreceptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption Hence it prevents diuresis.

An increase in body fluid volume switch off the osmoreceptors and suppress the ADH release. ADH can also affect the kidney function by its constrictory effects on blood vessels. This causes an increase in blood pressure. An increase in blood pressure increase the glomerular blood flow and the GFR.

Micturition
It is the voluntary signal from the central nervous system (CNS). This signal is initiated by the stretching of the urinary bladder in response to the stretch receptors on the walls of the bladder.

The urine is slightly acidic (pH – 6.0) and has a characterestic odour. 25 – 30 gm of urea is excreted out per day. Analysis of urine helps to know malfunctioning of the kidney.

Role Of Other Organs In Excretion
Lungs remove large amounts of CO₂ (18 litres/day) and water every day. Liver secretes bile-containing substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs.

The sweat and sebaceous glands in the skin eliminates watery fluid containing NaCl, small amounts of urea, lactic acid, etc. Sebaceous glands eliminates sterols, hydrocarbons and waxes through sebum. This secretion provides a protective oily covering for the skin.

Disorders Of The Excretory System
Uemia:
It leads to the accumulation of urea in blood. It lead to kidney failure. In such patients, urea can be removed by a process called hemodialysis.

Procedure of Dialysis:
Blood drained from a artery is pumped into a dialysing unit after adding an anticoagulant like heparin.The unit contains a coiled cellophane tube surrounded by a fluid (dialysing fluid).

The porous cellophane membrance allows the passage of molecules based on concentration gradient.
As nitrogenous wastes are absent in the dialysing fluid, the cleared blood is pumped back to the body through a vein after adding anti-heparin to it.

Remedy for kidney damage:
Kidney transplantation is the ultimate method in the correction of acute renal failures (kidney failure). A functioning kidney is used in transplantation from a donor to minimise its chances of rejection by the immune system of the host.

Renal calculi:
Stone or insoluble mass of crystallised salts (oxalates, etc.) formed within the kidney.

Glomerulonephritis:
Inflammation of glomeruli of kidney

NCERT SUPPLEMENTARY SYLLABUS
Diabetes Insipidus:
Antidiuretic hormone (ADH) is released from the posterior pituitary, prevents dehydration. It helps in the reabsorption of water by the distal parts of the kidney tubules and prevents diuresis. Deficiency of ADH leads to diabetes insipedus, that means huge amounts of dilute urine is formed followed by intense thirst.

The name itself (diabetes = overflow; insipidus = tasteless) distinguishes it from diabetes .mellitus (mel = honey), in which insulin deficiency causes large amounts of blood sugar to be lost in the urine

Artificial kidney:
Hemodialysis machine is known as the artificial kidney. Hemodialysis is an artificial process of removing toxic substances from the blood in patients of kidney failure.

Students can Download Chapter 14 Oscillations Notes, Plus One Physics Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Physics Notes Chapter 14 Oscillations

Introduction
In this chapter, we study oscillatory motion. The description of an oscillatory motion requires some fundamental concept like period, frequency, displacement, amplitude and phase.

Periodic And Oscillatory Motions
Periodic Motion:
A motion that repeats itself at regular intervals of time is called periodic motion.
Example:

• The orbital motion of planets in the solar system.
• The piston in a steam engine going back and forth

Oscillations or Vibrations:
A body executes to and fro motion at regular intervals of time is called oscillatory (or) vibratory motion.

Note:
(1) When the frequency is small, we call it oscillation. When the frequency is high, we call it vibration.
Period and frequency:
Period (T):
Time taken to complete one oscillation is called period

Frequency (n):
The number of oscillations per second is called frequency.
frequency v = \(\frac{1}{T}\)Hz

Displacement:
Displacement of oscillation means the change of any physical property with time under consideration.

Explanation:
For example, consider the oscillation of block attached to a spring. In this case the displacement of block with time is referred to as displacement.

In the case if oscillation of simple pendulum, the angle from the vertical as a function of time may be regarded as a displacement variable. The voltage across a capacitor, changing with time in an a.c. circuit is also a displacement variable

Note:
The displacement variable may take both positive and negative values.

Mathematical expression for displacement:
The displacement of a periodic function can be written as

Simple Harmonic Motion (S.H.M.)
Simple harmonic motion is the simplest form of oscillatory motion.

The oscillatory motion is said to be simple harmonic motion if the displacement ‘x’ of the particle from the origin varies with time as

Where
x(t) = displacement x as a function of time t
A = amplitude
ω = angular frequency
(ω t+ Φ) = phase (time-dependent)
Φ = phase constant or initial phase

Graphical Variation of S.H.M.

The above graph shows the graphical representation of x(t) = A coswt with time.
(Initial phase Φ = 0)

Amplitude of S.H.M.
The maximum displacement of S.H.M. from mean position is called the amplitude of S.H.M.
Note:
1.

Two simple harmonic motions having, same w and Φ but different amplitudes A and B as shown in the above figure.

2.

Two simple harmonic motions having the same A and w but different phase angle Φ as shown in the above figure.

Simple Harmonic Motion And Uniform Circular Motion

Question 1.
Show that the projection of uniform circular motion on any diameter of the circle is S.H.M.

Answer:
Consider a particle moving along the circumference of a circle of radius ‘a’ and centre O, with uniform angular velocity w. AB and CD are two mutually perpendicular diameters along X and Y axis. At time t = 0. let the particle be at P₀ so that ∠P₀OB = Φ.

After time Y second, let the particle reach P so that ∠POP₀ = ωt. N is the foot of the perpendicular drawn from P on the diameter CD.

Similarly M is the foot of the perpendicular drawn from P to the diameter AB. When the particle moves along the circumference of the circle, the foot of the perpendicular executes to and fro motion along the diameter CD or AB with O as the mean position. From the right angle triangle O MP, we get
cos (ωt + Φ) = \(\frac{\mathrm{OM}}{\mathrm{OP}}\)
∴ OM = OP cos (ωt + Φ)
X = a cos (ωt + Φ) ………………. (1)
Similarly, we get
sin (ωt + Φ) = \(\frac{y}{a}\) (or)
Y = a sin (ωt + Φ) ……………… (2)
Equation (1) and (2) are similar to equations of S.H.M. The equation(1) and (2) shows that the projection of uniform circular motion on any diameter is S.H.M.
At t = 0, if the particle is at B, then Φ = 0. Then equations (1) and (2) reduce to
x = a cos ωt ………………….. (3)
y = a sin ωt …………………….(4)

Velocity And Acceleration In Simple Harmonic Motion B
Velocity Of S.H.M.
The y displacement of S.H.M. is given by
y = a sin ω t
∴ velocity in y direction

Case – 1
At the mean position y=0, therefore velocity is maximum. The maximum velocity is given by

Case – 2
At the extreme position, y = a
∴ V_minimum = \(\sqrt{a^{2}-a^{2}}\) = 0
So the velocity of a S.H.M. varies between o and wa

Acceleration of S.H.M
We know y = a sin ω t
Velocity v = \(\frac{d y}{d t}\) = a ω cos ω t
Acceleration a = \(\frac{d^{2} y}{d t^{2}}\) = -aω² sin ωt
a = -aω² sin ωt

This equation shows that acceleration of a SHM is directly proportional to the displacement and opposite to the displacement.

Variation of displacement Y with time t:

Variation of velocity (v) with time:

Variation of acceleration with time:

Force Law For Simple Harmonic Motion
According to Newton’s second law of motion F = ma
But a = -ω²y(t)
ie. force acting on the S.H.M. in Y direction
F = -mω²y(t)
(or) F = -ky(t)
Where k= mω²
From the above equation (1), we can take an alternative definition of simple harmonic motion.

Statement:
Simple harmonic motion is the motion executed by a particle subject to a force, which is proportional to the displacement of the particle and is directed towards the mean position.

Energy In Simple Harmonic Motion
A simple harmonically moving particle possesses both potential energy and kinetic energy. Potential energy is due to its displacement against restoring force. Kinetic energy is due to its motion.

Total energy of the S.H.M. is the sum of the kinetic energy and potential energy. Total energy remains a constant throughout its motion.

Expression for Kinetic energy:
Let m be the mass of the particle executing SHM. Let V be the velocity at any instant,

Expression for potential energy:
Potential energy is work required to take the particle against the restoring force.

Work done to displace the particle through a small distance dy, dw = force × displacement
= mω²y × dy [force = ω²y ]. Therefore total work done to take the particle from o to y.


This work done is stored in the particle as its potential energy.

At extreme position y = a

At equilibrium position y = 0
∴ PE = 0
Total energy of a S.H.M.
Total energy = PE + kE

∴ Total energy = maximum KE = maximum PE

Graphical variation of PE, KE and TE of S.H.M.

Some Systems Executing Simple Harmonic Motion
Oscillations due to a spring Hooks Law:
The force acting simple harmonic motion is proportional to the displacement and is always directed towards the centre of motion.
F α – x (or) F= kx
where k is called spring constant

Period of oscillation of a spring:

Consider a body of mass m attached to a massless spring of spring constant K. The other end of spring is connected to a rigid support as shown in figure. The body is placed on a frictionless horizontal surface.

If the body be displaced towards right through a small distance ‘x’, a restoring force will be developed.

The Simple Pendulum:

Consider a mass m suspended from one end of a string of length L fixed at the other end as shown in figure. Suppose P is the instantaneous position of the pendulum. At this instant its string makes an angle θ with the vertical.

The forces acting on the bob are (1) weight of bob F_g (mg) acting vertically downward. (2) Tension T in the string.

The gravitational force F_g can be divided into a radial component F_gCos θ and tangential component F_gSin θ. The radial component is cancelled by the – tension T. But the tangential component F_gSin θ produces a restoring torque.

Restoring torque τ = – F_g sin θ . L.
τ = -mg sin θ.L …………….. (1)
-ve sign shown that the torque and angular displacement θ are oppositely directed. For rotational motion of bob,.
τ = Iα …………. (2).
Where I is a moment of inertia about the point of suspension and α is angular acceleration. From eq (1) and eq (2).
Iα = -mg sin θ.L
If we assume that the displacement θ is small, sin θ ≈ θ.
∴ Iα = -mg θ.L
Iα + mg θ.L = 0

Damped Simple Harmonic Motion
Periodic oscillations of decreasing amplitude due to the presence of resistive forces of the medium are called damped oscillations.

Question 2.
Derive a differential equation for a damped simple harmonic oscillation.

Answer:
Consider a block of mass ‘m’ connected to one end of a massless spring of spring constant K. The other end of spring is connected to rigid support. The block is connected to a vane through a rod (The vane and rod are massless). The vane is submerged in a liquid.

Let the equilibrium position of block be ‘O’. If this block is moved along downward direction through a distance x, a damping force will be developed on vane due to liquid. This damping force is proportional to velocity of vane ie; damping force F_d α – v (or) F_d = -bv

where b is called damping constant. The value of b depends on the characteristics of the liquid and the vane.

The restoring force on the block due to spring. F_s = -kx. where x is the displacement of the mass from its equilibrium position.
∴ Total force on the block, F = -bv + -kx
ma = -bv + -kx
ma + bv + kx = 0
\(m \frac{d^{2} x}{d t^{2}}+b \frac{d x}{d t}+k x=0\)
This is the differential equation of S.H.M.

The motion of damped harmonic oscillator:
The solution of the above differential equation of damped harmonic oscillator is

Case – 1
b = 0 (There is no damping force). In this case, we get

The above result shows that, if there is no damping force (b = 0). The oscillator behaves like a undamped oscillator.

Case – 2
If b is small, the amplitude of the oscillator decreases continuously with time. The motion is approximately a periodic. The Variation of displacement x (t) with time T is shown below.

Case – 3
If damping constant b is large, the amplitude of the oscillator decreases to zero very quickly. The motion is not a periodic motion. The variation of displacement x (t) with time T is shown below.

The Energy variation of damped oscillator:
The energy of an undamped oscillator, E = \(\frac{1}{2}\)kA².
where A is the amplitude of an undamped oscillator. But for the damped oscillator, amplitude = Ae^-bt/2m.

The above equation shows that the energy of a damped oscillator decreases exponentially with time, which is shown below

Note:
Small damping means that the dimensionless ratio
\((b / \sqrt{k m})\) is much less than 1.

Forced oscillations and resonance
Free oscillation:
When a body oscillates in the absence of external forces (eg. friction etc.) the oscillations are said to be free oscillations.

Forced oscillation:
When an external periodic force is applied to a damped harmonic oscillator, the oscillator will vibrate with a constant amplitude and frequency of vibration will be that of the applied periodic force. This type of oscillation is called forced oscillation.

The differential equation of forced oscillator:
Let F(t) = F₀ cosω_dt is an external force applied to a damped oscillator.

The total force acting on the damped oscillator,
F = – bv – kx + F₀ cosω_dt
where -bv is the damping force and -kx is the linear restoring force.
F + bv + kx = F₀ cosω_dt
\(m \frac{d^{2} x}{d t^{2}}+b \frac{d x}{d t}+k x=F_{0} \cos \omega_{d} t\)
This is the differential equation of an oscillator of mass m on which a periodic force of (angular) frequency ω_d is applied. The oscillator initially oscillates with its natural frequency w. When we apply the external periodic force, the oscillation with the natural frequency die out, and the body oscillates with the (angular) frequency of the external periodic force.

The motion of forced oscillator:
The solution (displacement) of the above differential equation of forced oscillator can be written as
x(t) = Acos(ω_dt + Φ)

where m is the mass of the particle v₀ and x₀ are the velocity and the displacement of the particle at time t = 0, (which is the moment when we apply the periodic force)

Case -1
When b = 0 (damping force = 0) and ω = ω_d,
we get A = \(\frac{F_{0}}{0}\)
A = ∞
This is an ideal case. This case never arises in a real situation as the damping is never perfectly zero.

Case – 2
(Small damping, driving frequency far from natural frequency).
In this ω_db << m(ω² – ω_d²). Hence we can neglect ω_db. Hence amplitude of oscillation can be written as.

Case – 3
(Small damping, driving frequency close to natural frequency).
In this case m(ω² – ω_a²) << ω_db. Hence we can neglect m (ω² – ω_a²). Hence amplitude of oscillation can be written as

This equation shows that the maximum amplitude fora given driving frequency is governed by the driving frequency and damping constant.

Resonant Oscillation
When the frequency of the external periodic force is varied, it is found that the amplitude of the forced vibration increases and reaches a maximum value and then decreases.

The amplitude will be maximum when the frequency of the applied periodic force is equal to the natural frequency of the vibration. Such oscillations are called resonant oscillations and the phenomenon is called resonance.

Graphical variation amplitude with driving frequency:

Examples of resonance:
All mechanical structures have one or more natural frequencies, and if a structure is subjected to a strong external periodic driving force that matches one of these frequencies, the resulting oscillations of the structure may rupture it.

The Tacoma Narrows Bridge at Puget Sound, Washington, USA was opened on July 1, 1940. Four months later winds produced a pulsating resultant force in resonance with the natural frequency of the structure.

This caused a steady increase in the amplitude of oscillations until the bridge collapsed. It is for the same reason the marching soldiers break steps while crossing a bridge. Aircraft designers make sure that none of the natural frequencies at which a wing can oscillate match the frequency of the engines in flight! Earthquakes cause vast devastation.

In an earthquake, short and tall structures remain unaffected while the medium height structures fall down. This happens because the natural frequencies of the short structures happen to be higher and those of taller structures lower than the frequency of the seismic waves.