Biology Class 10 Notes Chapter 12 Coordination and control Short Questions
Q.1) How do reflex action work in human beings?
Answer:
Reflex action:
It can be defined as an automatic, immediate, quick involuntary, fixed response to an environmental change (stimulus). Generally, the brain is not involved in reflex actions. We can say these are the involuntary responses of the body on which we do not have any control.
Q.2) What are the causes of epilepsy and paralysis?
Answer:
Causes of Epilepsy:
It may be caused by changes in the brain due to genetic reasons. Severe head injuries, stroke, brain infections, and drug abuse may also cause epilepsy.
Causes of Paralysis:
It occurs when either a blood clot is struck in the fine blood vessels of the brain or due to rupturing of blood vessels in the brain due to high blood pressure. read more:
Q.3) What happens if Islet of Langerhans secrete insulin but not glucagon?
Answer:
Glucagon works opposite to insulin and increases blood glucose levels. For this purpose it promotes the breakdown of glycogen to glucose in the liver and muscles. It also increases the release of glucose from the liver to the blood.
Q.4) Why is the pituitary gland known as the master gland?
Answer:
Pituitary gland is an oval structure attched to the hypothalamus of the brain. It is about the size of a pea seed and weighs about 0.5 gm in adults. It is generally termed as “the master gland” of the body. It has two main lobes i.e. anterior and posterior.
Q.5) Differentiate between the two types of coordination system.
Answer:
Nervous Co-ordination:
It is performed by the nervous system.
Chemical Co-ordination:
It takes place through certain chemicals called hormones.
Q.6) What is the role of insulin and glucagon?
Answer:
Role of Insulin:
Insulin controls the level of glucose in the blood by excreting the excess amount of glucose from the blood through urine.
Role of Glucagon:
Glucagon works opposite to insulin and increases blood glucose levels. For this purpose, it promotes the breakdown of glycogen to glucose in the liver and muscles. It also increases the release of glucose from the liver to the blood.
Q.7) What characters are controlled by the ovarian hormones?
Answer:
- The secondary sexual characters in the female
- It prepares the female body for maintaining the state of pregnancy
Q.8) State the hormones of the pituitary and thyroid glands and write their functions.
Answer:
Hormones of Pituitary:
i. Growth Hormone: Increases the cell division of somatic cells and promotes the growth of the body.
ii. Thyroid Stimulating Hormone: This hormone controls the development and secretion of the thyroid hormone.
iii. Adreno-Cortico-Trophic Hormone (ACTH): It acts on the cortex part of the adrenal gland to release the adrenal hormone.
iv. Luteinising Hormone: It is needed for the release of egg cells from the ovary in the female.
v. Antidiuretic Hormone or Vasopressin: This hormone affects the renal tubules to reabsorb large quantities of water from the glomerular filter.
vi. Oxytocin: Its main function is to contract the uterus muscles during childbirth.
Hormones of Thyroid Glands:
i. Thyroxine: Increases the metabolism of the body and produces heat in the body.
ii. Calcitonin: It stimulates the transfer of calcium io from blood to the bone.
Biology 10th Notes Long Questions Chapter 12
Q.1) Explain the different types of receptors in human beings.
Answer:
We know that the organs or parts which are specifically built to detect particular type of stimuli are called sense organs or receptors. Main receptors in man are eyes, ears, nose, taste buds, receptors of touch, heat and cold etc.
1. Photoreceptor: Eye:
These are also known as visual receptors. Eye is an organ used as a photoreceptor in the human body. A pair of eyes is present in human beings which are present in the orbits on the face. The eye is a very complex structure. The structure of eye can be divided into three main layers.
i. Outer most lyer:
The outer layer of eyeball consists of sclera and cornea. Sclera gives eye most of its white colour. It consists of dense connective tissue and protects the inner components of eye and maintains its shape. In the front, sclera forms the transparent cornea. Cornea admits light to the interior of eye and bends light rays so that they can be brought to a focus.
ii. The middle layer:
The middle layer is called choroid. It contains blood vessels and gives the inner eye a dark colour. The dark colour prevents disruptive reflections within eye. Behind cornea, choroid bends to form a muscular ring, called iris. There is round hole, called pupil, in the centre of iris. After striking the cornea, light passes through the pupil. The size of pupil is adjusted by the muscles of iris. Pupil constricts in bright light when the circular muscles of iris contract. Similarly, pupil dilates in dim light when the radial muscles of iris contract.
Behind iris, there is a convex lens, which focuses light on retina. Lens is attached to ciliary muscles of eye via a ring of suspensory ligament. To clearly see an object far away, ciliary muscles are relaxed and lens becomes less convex. When ciliary muscles contract, lens becomes more convex and round.
iii. The inner layer:
The inner layer is sensory and is called as retina. It contains the photosensitive cells called rods and cones and associated neurons.
Rods are sensitive to dim light while cones are sensitive to bright light and so distinguish different colours. Retina has two points i.e. fovea and optic disc. Fovea is a dip in retina, directly opposite to lens and is densely packed with cone cells. It is largely responsible for colour vision and sharpness. Optic disc is a point on retina where the optic nerve enters retina. There are no rods and cones at this point, that is why it is also referred to as the blind spot
2. Sono-receptor – Ear:
Sound waves are perceived by sono-receptors. In human beings and other vertebrates a pair of ears is used to receive sound waves, Human ear can be divided into three ports, external ear, middle ear and internal ear
i. External Ear:
It is consits of the pinna, auditory canal and ear drum (tympanum). The pinna and the earlop is the external cartilaginous structure which collects sound waves. Sound waves then travel through the auditory canal which ends at the eardrum. It is a membrane which separates the outer ear from the middle ear.
ii. Middle Ear:
Middle ear consists of a set of three small bones called ossicles i e. malleus, incus and stapes. These bones are the smallest bones of the body. These ossicles are attached to one another in a chain-like fashion, The malleus is attached to the eardrum and the stapes is attached to the oval window of the cochlea The oval window separates the middle ear from the inner ear. A Eustachian tube connects the middle ear cavity with the pharynx. The Eustachian tube helps in equalising the pressure between the middle ear and the environment
iii. Internal Ear:
Internal ear is a fluid filled chamber after the oval window. It contains two important structures i e a coiled tubule called the cochlea and a set of three semicircular canals. The middle chamber of the cochlea has the hearing apparatus, called the organ of Corti. Special hair cells are present in the organ organ of Corti, which are the receptor cells for sound. The semicircular canals help in maintaining the balance of the body.
Q.2) Describe the structure of the human brain.
Answer:
Brain:
In animals, all life activities are under the control of the brain, Inside the cranium, the brain is covered by three layers of membranes, collectively called meninges. Their function is to protect the brain from harmful substances The brain contains fluid-filled ventricles. The ventricles of the brain ore continuous with the central canal of the spinal cord. The fluid within the ventricles and the central canal of the spinal cord is called the cerebrospinal fluid (CSF). It bathes the neurons of the brain and the spinal cord and cushions against physical and mechanical stresses.
Human brain can be divided into three ports; forebroin, midbrain and hindbrain.
a) Forebrain:
This is the largest area of the brain It is most highly developed in humans. The following most important parts of this region.
(i). Cerebrum:
This is the largest port of the broin. It is divided into two halves, called cerebral cerebral hemisphere. These halves communicate with each other by means of a large bond, called the corpus callosum. The outer region of the cerebrum called the cerebral cortex. It has many folds and convolutions, which increase its surface area. It is made of grey matter (containing cell bodies and non-myelinated axons). The material beneath the cortex is white matter (containing myelinated axons).
The cerebrum is the most important part of the brain. It receives sensory information, processes it, stores some in memory for future use, directs voluntary movements, and is responsible for intelligence, thinking, reasoning and decision making. The speech centre is also present in the cerebrum which is unique to human beings.
(ii). Thalamus:
This is wrapped by the cerebrum. It carries sensory information especially from the eyes and ears and generally from the skin and other internal organs of the body to the limbic system and cerebrum.
(iii). Limbic system:
It is located in an arc between the thalamus and cerebrum. This system processes responses like hunger, thirst, fear, anger, tranquillity, pleasure and sexual responses. A portion of the limbic system is also important in the formation of memories. Hypothalamus is a part of the limbic system. It lies below the thalamus.
b). Midbrain:
The midbrain is reduced in human beings and is present under the cerebral hemisphere. It controls reflex movements of the eyes and hearing reflexes. The midbrain is a relay centre that connects the forebrain with the hindbrain.
c). Hindbrain:
Hindbrain consists of the cerebellum, pons, and medulla oblongata.
(i). Cerebellum:
It controls the balance of the body and coordinates the voluntary movements of the body as well. We can pick up a book from a table or touch our foot without mistake because of a healthy cerebellum, It is also involved in the learning and memory storage for showing different behaviours.
(ii). Pons:
Pons is located above the medulla, It controls transitions between sleep and wakefulness, and the rate and pattern of breathing.
(iii). Medulla Oblongata:
The medulla oblongata is the posterior part of the brain. it controls automatic functions like breathing, heart rate, circulation of blood, blood pressure, swallowing and vomiting
Q.3) Write a comprehensive note on chemical coordination in human beings.
Answer:
Chemical Coordination in Human Beings:
Chemical coordination is done through special chemicals called hormones, in animals, hormones are synthesized in endocrine glands which are also called ductless glands. This is because these glands do not have any duct or tube to release their secretion at the site of action or targeted site. They release their secretion in the blood which takes it to the tissues or organs where it is required.
Hormones are organic compounds produced in the endocrine glands, poured directly into the blood and are transported to respective target tissues where they affect. Hormones do not initiate new biochemical reactions but produce their effects by regulating the reactions. They may either stimulate or inhibit a function. Hormones also control some long term changes in the body such as the rate of metabolic activity, rate of growth, and sexual maturity. Most hormones are chemically proteins but some are derivatives of fatty acids i.e. steroids.
Human Endocrine Glands:
The human endocrine system consists of about 20 endocrine glands found in different parts of the body. Here you will study some important glands and their hormones.
1. The Pituitary Gland:
This is an oval structure attached to the hypothalamus of the brain. It is about the size of a pea seed and weighs about 0.5 gm in adults. It is generally termed as “the master gland” of the body. It has two main lobes i.e. anterior and posterior.
A. Anterior Lobe of Pituitary Gland:
It secretes the following hormones.
i. Growth Hormones:
This hormone increases the cell division of somatic cells and promotes the growth of the body. It is secreted more in childhood but in adults the secretion becomes normal. If it is secreted in excess during early life it results in a disorder called gigantism. Its under-secretion in early life causes dwarfism in which the body of the child does not grow.
ii. Thyroid Stimulating Hormone (TSH):
This hormone controls the development and secretion of the thyroid hormone (thyroxin).
iii. Adreno-Cortico-Trophic Hormone (ACTH):
It acts on the cortex part of the adrenal gland to release the adrenal hormone.
iv. Luteinising Hormone (LH):
It is needed for the release of egg cells from the ovary (ovulation) in females. In males, it stimulates the testes to produce sex hormones.
B. The Posterior lobe of Pituitary Gland:
It secretes the following hormones;
i. Antidiuretic Hormone (ADH) or Vasopressin:
This hormone affects the renal tubules to reabsorb large quantities of water from the glomerular filtrate.
ii. Oxytocin:
Its main function is to contract the uterus muscles during childbirth. It also stimulates the flow of milk from the breasts during lactation.
2. Thyroid Gland:
The thyroid gland is situated above the larynx. It consists of two lobes; one on each side of the larynx. It secretes two hormones.
i. Thyroxine:
This hormone increases the metabolism of the body and produces heat in the body. It promotes growth, hence it is secreted more at a young age. Thyroxine is an iodine-containing compound.
If thyroxine is produced less than the required amount, cellular metabolism slows. It results in lethargy, weight gain, and low heart rate and body temperature.
If thyroxine is produced more than required, cellular metabolism becomes faster than normal. It results in weight loss; and high blood pressure, heart rate, and body temperature.
ii. Calcitonin:
It stimulates the transfer of calcium ions from the blood to bone, where the calcium ions can be used to generate bone tissue. In this way, calcitonin maintains blood calcium levels.
3. Pancreas:
The pancreas has both exocrine and endocrine activity. As.an exocrine gland, it is part of the digestive system and produces pancreatic juice which helps in digestion of food.
As an endocrine gland, it secretes two hormones insulin and glucagon. The endocrine function is performed by the special cells present in the pancreas called islets of Langerhans.
4. Adrenal Gland:
A pair of the adrenal gland is present, one on top of each kidney. The outer layer of this gland is called the adrenal cortex and the inner layer as the adrenal medulla.
i. Hormones of the Adrenal Cortex:
The adrenal cortex works under the action of ACTH from the anterior pituitary.
It secretes many steroid hormones collectively called corticosteroids. These hormones control the metabolism of minerals and glucose.
ii. Hormones of the Adrena Medulla:
The adrenal medulla produces two hormones called adrenaline and noradrenaline.
These hormones are also called epinephrine and norepinephrine respectively
Adrenaline and Noradrenaline Hormones:
These hormones are secreted in stressful situations. Adrenaline essentially dilates blood vessels in certain parts of the body such as the skeletal muscles and increases the heart’s output. It is secreted in emotions and anger, hence the face becomes red.
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Noradrenaline constricts blood vessels in certain areas of the body such as the gut and face. This is why in fear the face becomes pale or white and a person feels hollow in the gut.
5. Gonads:
Gonads are the reproductive organs, which produce gametes. The male gonads are called testes and the female gonads are called ovaries, both produce many important hormones.
Hormones of the Ovary:
(i). Oestrogens:
It brings about the development of the secondary sexual characters in the female (e.g. development of breast).
(ii). Progesterone:
It prepares the female body for maintaining the state for pregnancy.
Hormones of the Testes:
The testes produce a hormone called testosterone. It brings about the development of the male secondary sexual characteristics like the growth of hair on the face, thickening of voice, etc.
Q.4) Discuss any two disorders of the human eye.
Answer:
Short Sightedness:
Short sightedness or near sightedness, is an eye disorder in which a person can see closer objects clearly, but distant objects are not clearly visible.Technically this disorder is known as myopia. It is caused by a usually long eyeball. IN short sightedness, light rays do not focus on the surface of the retina. Rather, the rays focus in front of the retina. Since the light is focused too early, a blurred image is left on the retina.
This problem can be rectified by using concave lenses in glasses or contact lenses. Concave lens ensures that light is focused onto the retina of the eye, so that distant objects do not appear blurry. Short-sightedness can also be cured with laser eye surgery. In laser eye surgery a laser is used to reshape the cornea to correct its curve. Therefore, light is better focused on the retina.
Long Sightedness:
Long sightedness or farsightedness, is a disorder in which a person can see distant objects clearly, but the close objects are not clearly visible. The disorder is caused when the eyeball is too short or the shape of the lens is not round. Technically this disorder is known as hypermetropia. In long-sightedness, light rays do not focus on the surface of retina. Rather the rays focus behind the retina. Since the light is focussed behind the retina, a blurred image is left on the retina.
Long-sightedness is rectified by using a convex lens in glasses or contact lenses. Convex lens ensures that light is focussed onto the retina of eye, so that close objects do not appear blurry. Long-sightedness can also be cured with laser eye surgery. In laser eye surgery a laser is used to reshape the cornea and improve the curve. Therefore, light is better focussed on the retina.
Q.5) Describe the causes, symptoms and treatment of paralysis.
Answer:
Paralysis:
Paralysis is a vascular disorder of the brain. It occurs when either a blood clot is struck in the fine blood vessels of the brain or due to the rupturing of blood vessels in the brain due high blood pressure. This causes damage to that part of the brain. This damage may be permanent or temporary. As a result; the part of the body controlled by the affected part of the brain stops functioning.
The patient of paralysis is unable to move the muscles of one side of their body or both sides. Paralysis may also affect the arms or the legs, and sometimes the whole body.
There is currently no cure for paralysis. The existing treatments only help a person to adapt to this way of life by making them independent. Patients are given physiotherapy to improve their muscle weakness. Mobility aids such as wheelchairs and orthoses (braces designed to improve the function of a limb) are also used for patients of paralysis.
Q.6) Describe the causes, symptoms and treatment of epilepsy.
Answer:
Epilepsy (fits or “mirgi”):
This is a type of functional disorder of the nervous system in which suddenly excessive discharge of nerve impulses takes place from the brain. The abnormal bursts of impulses from neurons which cause the body to behave strangely are called seizures. People generally call it fits.
Some epilepsy patients simply experience an odd feeling. Others may have convulsions (shaking of the body) or may lose consciousness. The body becomes rigid and stiff. The patient’s hands are clenched and they frequently bites their tongue.
Epilepsy may be caused by changes in the brain due to genetic reasons. Severe head injuries, stroke, brain infections and drug abuse may also cause epilepsy. In the treatment for epilepsy, seizures are controlled. Anti-epileptic drugs (AEDS) are used for the treatment of epilepsy. AEDS do not cure epilepsy but can prevent seizures from occurring.
Q.7) Explain the mechanism of vision by the eyes.
Answer:
Mechanism of Vision:
The light rays coming through the cornea and lens make an image on the retina. The photoreceptor cells i.e. rods and cones of the retina produce nerve impulses in the neurons present in the retina. The axons of these neurons are part of the optic nerve. The optic nerve carries information in the form of nerve impulses from the retina to the cerebrum of the brain. Here, the impulses are processed to produce a meaningful sensation of shape and color.
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