NCERT Solutions for Class 10 Science Chapter 7 - Control And Coordination

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Answer:

Gustatory receptors are present on the tongue and it detects taste. Olfactory receptors are located in the mucosa of the nasal cavity which detects the smell. Auditory receptors are present in the inner ear which detects sound.

Hence, the correct answer is option A.

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 Dendrites of one neuron receive an electrical impulse from axonal end of another neuron. After that, the impulse travels through the cell body to axon to axonal end.

Hence, the correct answer is option C.

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Chemical signals (neurotransmitter) are transmitted from axonal end of one neuron to dendrite of another neuron through a gap called synapse.

Hence, the correct answer is option D.

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Electrical impulse release some chemical called neurotransmitters at the axonal end. This chemical excites the dendrite of another neuron to transmit the signal.

Hence, the correct answer is option B.

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Sensory neuron collect signal from the receptor in a reflex arc. This signal moves forward to spinal cord and then through the motor neuron, it reaches to muscles.

 Hence, the correct answer is option D.



 

Answer:

Reflex action is involuntary and immediate movement in response to stimulus and the path followed by a reflex action is called reflex arc.

 Hence, the correct answer is option C.

Answer:

 The forebrain is the main thinking part of the brain. Separate areas for hearing, smell, sight are located in the forebrain. Many of the involuntary action including salivation, vomiting, blood pressure is controlled by medulla in the hindbrain.

Hence, the correct answer is option C.

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The cerebellum is a part of hindbrain which coordinates the voluntary movements of skeletal muscles such as posture, balance and equilibrium.
 
Hence, the correct answer is option B.

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Spinal cord originates from the medulla. It is the pathway for messages sent by the brain to the body and from the body to the brain.

 Hence, the correct answer is option B.

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 The term "Photo" means light and "tropism" means directional movement. Shoot responds to light by growing towards the direction of the source of light. This is termed phototropism.

Hence, the correct answer is option D.

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Abscisic acid is a growth-inhibiting hormone. It promotes dormancy in seed and bud, wilting of leaves and closing of stomata.

 Hence, the correct answer is option C.

Answer:

Abscisic acid is a growth-inhibiting hormone. It promotes dormancy in seed and bud, wilting of leaves and closing of stomata.

 Hence, the correct answer is option D.

Answer:

Iodine is necessary for the thyroid gland to make "Thyroxine". Thyroxine promotes metabolism in all the cells and tissue in the body. Excessive secretion of thyroxine result in the body is called as hyperthyroidism, and less secretion is called hypothyroidism.

Hence, the correct answer is option B.

Answer:

Insulin has no role in the growth and development of the body. It is a hormone produced by the pancreas. It regulates blood sugar levels. Thus, less secretion of this hormone will cause diabetes.

 Hence, the correct answer is option B.

Answer:

 Growth hormone is one of the hormones secreted by the pituitary. The pituitary gland is referred to as the "master gland" since it affects many activities of other glands. On the other hand, adrenaline is secreted by the adrenal gland.

Hence, the correct answer is option A.

Answer:

 Excess water makes the guard cell turgid and lack of water makes the guard cell flaccid. When the guard cell is turgid stomata open. When it is flaccid, stomata closed.

Hence, the correct answer is option C.

Answer:

Thigmotropism is a type of directional growth movement in response to touch. Cells away from the support showed rapid cell divisions and twine around it.

Hence, the correct answer is option C.

Answer:

The stigma of the flower releases a chemical which guides the pollen tube through style towards the ovule. Here the movement occurs in response to a chemical. Such a type of movement is called chemotropism.

Hence, the correct answer is option B.

Answer:

A tropism is the growth of a plant as a response to a stimulus, and phototropism occurs when a plant responds to light by bending in the direction of the light. So the movement of sunflower in accordance with the path of the sun is due to phototropism.

Hence, the correct answer is option A.

Answer:

Abscisic acid is a growth-inhibiting hormone and its effect include wilting of leaves. 

Hence, the correct answer is option C.

Answer:

Axonal end contains vesicle filled with a chemical called "neurotransmitter" which cross the gap or synapse and generate electrical impulse at the dendrite of another neuron.

Hence, the correct answer is option B.

Answer:

The hind brain contains three parts, cerebellum, pons and medulla oblongata. Medulla in the hind brain contains centers for respiration, cardiovascular reflex and gastric secretions. Many of the involuntary action including salivation, vomiting, blood pressure is controlled by it. 

Hence, the correct answer is option C.

Answer:

Involuntary action is the actions which are happening "without" the conscious choice of the organism. So chewing which is under conscious control is a voluntary action.

Hence, the correct answer is option D.

Answer:

Olfactory receptors are located in the mucosa of the nasal cavity which detects the smell. Severe cold blocks olfactory receptors due to this sense of smell being reduced.

Hence, the correct answer is option B.

Answer:

The impulse travels from dendrites to the cell body and then the axon to the axon terminal. Electrical impulse releases some chemicals called neurotransmitters at the axonal terminal. This chemical excites the dendrite of another neuron to transmit the signal.

Hence, the correct answer is option C.

Answer:

Answer:

The growth hormone is secreted by the pituitary gland and it regulates the growth and development of the body. If there is a deficiency of this hormone in childhood, it leads to dwarfism.

Hence, the correct answer is option B.

Answer:

The dramatic changes in the body features (secondary sexual characteristics) associated with puberty are mainly due to the secretion of testosterone from the testes (in males) and estrogen from the ovary (in females).

Hence, the correct answer is option C.

Answer:

Insulin is produced by the pancreas. Insulin controls the sugar level in the bloodstream. Hence, the doctor advised him to take an injection of insulin to bring his sugar level to normal.

Hence, the correct answer is option D.

Answer:

The male sex hormone is testosterone. It is produced by the testes at the onset of puberty. It plays an important role in the development of the male sex organ and also in developing secondary sexual characters in males.

Hence, the correct answer is option B.

Answer:

The pituitary gland is a small, unpaired endocrine gland that is present on the floor of the cranium of the brain. It controls the secretion of several important hormones.

Hence, the correct answer is option C.

Answer:

Synapse is a small gap between the axon of one neuron and the dendrite of the next neuron. The signals from one neuron are transmitted through chemicals (neurotransmitters) through this synapse to the next neuron. 

Hence, the correct answer is option D.

Answer:

Answer:

a) Sensory neuron
b) Spinal cord  
c) Motor neuron
d) Muscle (Effector)

The direction of the flow of electrical signals:
$\mathrm{Receptor} \mathrm{in} \mathrm{hand}\to \mathrm{Sensory} \mathrm{neuron}\to \mathrm{Spinal} \mathrm{cord}\to \mathrm{Motor} \mathrm{neuron}\to \mathrm{Muscles} \mathrm{in} \mathrm{arm}.$ 

Answer:

(a) elongation of cells: Auxin.
(b) growth of stem: Gibberellins.
(c) promotion of cell division: Cytokinin.
(d) falling of senescent leaves: Abscisic acid.



 

Answer:

(a) Pineal gland
(b) Pituitary gland
(c) Thyroid gland
(d) Thymus.

Answer:

Figure (a) appears more accurate as roots are showing positive geotropism and negative phototropism and moving towards the earth and away from the light. While the shoot is showing negative geotropism and positive phototropism moving away from the earth and towards the light source.

Answer:

(a) Dendrite
(b) Cell-body
(c) Schwann cell
(d) Axon-terminal

Answer:

Answer:

Tropic movement is the response towards or away from the stimuli that come from one direction. It is a directional movement. If the movement of the plant part is towards the stimulus, then it is known as positive tropism. If the movement of the plant part is away from the stimulus, then it is known as negative tropism. For example phototropism, chemotropism, geotropism, hydrotropism etc.

Answer:

The thyroid gland secretes the hormone thyroxine which controls the rate of metabolism of carbohydrates, fats, and proteins in the body. Iodine is required for the release of thyroxin from the thyroid gland. If iodine is deficient, thyroxine hormone will be deficient in the body and will cause goitre. The neck appears to be swollen due to enlargement of the thyroid gland.
 

Answer:

• Axon terminals have vesicles filled with chemicals (neurotransmitters).
• When a stimulus reaches the axon terminal, these fluid-filled vesicles fuse with the presynaptic membrane and pour their contents or neurotransmitters into the synaptic cleft.
• The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane.
• This binding opens ion channels allowing the entry of ions which can generate a new potential in the post-synaptic neuron. 
• In this way, the impulse is conducted or transmitted from one neuron to another.

Answer:

(a) Estrogen is responsible for the development of secondary sexual characteristics in females during puberty.
(b) Deficiency of the growth hormone results in dwarfism.
(c) Insulin regulates the blood sugar level. The deficiency of insulin causes diabetes.
(d) Iodine is necessary for the synthesis of the thyroxine hormone from the thyroid gland.

Answer:

(a) Pituitary gland is located inside the brain.
(b) Pancreas being a mixed gland secretes digestive enzymes as well as hormones.
(c) Adrenal gland is situated at the top of each kidney.
(d) Testis acts as an endocrine gland that is present in males but not in females.

Answer:

Structure of neuron-



The neuron is the structural and functional unit of the nervous system. The main function of neurons is to transmit signals to and from the brain.
Neurons are arranged end to end, forming a chain. This helps in the continuous transmission of impulses. Each neuron receives an impulse through its dendrite and transmits it to the next neuron in a sequence through its axon. 
 

Answer:

The human brain is the main coordinating center of the body. It is a part of the central nervous system and receives information from the other parts of the body and interprets them. The human brain can be divided into three distinct regions.

(i) Forebrain: It consists of the cerebrum, thalamus, and hypothalamus. The forebrain is the main site of learning, intelligence, and thinking. It also has sensory and motor sites which control all the voluntary movements. Hypothalamus is concerned with things like body temperature, urge to eat, drink, etc.

(ii) Midbrain: It consists of regions concerned with the sense of sight, hearing, etc. It also transmits motor impulses to the limbs.

(iii) Hindbrain: It consists of the cerebellum, pons, and medulla oblongata. It controls most of the involuntary actions like heartbeat, blood pressure, etc. Cerebellum maintains the posture and equilibrium of the body.

Answer:

The central nervous system consists of the brain and spinal cord while the peripheral nervous system consists of all the nerves that branch out from the brain (cranial nerves) and the spinal cord (spinal nerves).
 
The brain sits inside a bony box called a skull (or cranium). Inside the skull, there is a fluid-filled membrane. The fluid is called cerebrospinal fluid that acts as a shock absorber. The spinal cord is well protected by the vertebral column or backbone.
 

Answer:

(a) Thyroxin- It regulates carbohydrate, fat, and protein metabolism in our body. It indirectly affects the growth of the body by promoting the growth and differentiation of tissues.

(b) Insulin- ​It regulates the blood sugar level in the human body. It increases the permeability of the cell membrane for glucose and accelerates the passage of glucose into the cells from the bloodstream.

(c) Adrenaline- In case of danger, emergency, or stress, adrenaline is secreted in large quantities to prepare the body to face the situation. For this reason, it is also known as the ‘emergency hormone’. This hormone is secreted even in normal situations but in small quantities. 

(d) Growth hormone- It is involved in the growth and development of the human body. 

(e) Testosterone- It is responsible for the growth and development of male secondary sexual characters. It also helps in sperm production.
 

Answer:

There are five major types of plant hormones: auxins, gibberellins, cytokinins, abscisic acid, and ethylene. 

Auxins- When the growing parts of a phototropic plant detect sunlight, auxins (synthesized at the shoot tips) help the cells grow longer. When light falls on one side of the plant, the auxins generally diffuse towards the shaded side of the shoot. They also helps in root formation, apical dominance, inhibition of abscission and fruit growth.

Gibberellins-They are produced in the roots of a plant. They promote stem elongation by promoting cell division in the inter-nodal region.

Cytokinins-They promotes cell division. Therefore, they are present in greater concentration in those areas of the plants where rapid cell division occurs. For example, the tip of the shoot.

Abscisic acid- It promotes seed dormancy by inhibiting cell growth. It is involved in the opening and closing of stomata. It is also responsible for the shedding of leaves.

Ethylene- It regulates fruit ripening. It is produced during the ripening of fruits.

Answer:

Reflex action is a sudden, spontaneous, automatic, involuntary response to the stimulus. It is an involuntary response as it is carried out without any conscious effort by the brain. The path along which the action is carried out is called the reflex arc.
Examples- (1) Sudden withdrawal of hand while it comes in contact with a hot object. 
(2) Narrowing of the pupil on exposure to bright light. 

Reflex arc- The pathway of the nerve impulses involved during a reflex action constitutes the reflex arc. When there is a stimulus, it is first perceived by receptors present on the skin that send the stimulus in the form of an impulse, from the sensory neuron to the spinal cord. The spinal cord interprets the stimulus and sends the impulse to the motor neurons. The motor neurons in turn stimulate the effectors or muscles to respond to the stimulus.


                                                    A schematic diagram of the reflex arc

 

Answer:

In human beings, control and coordination are brought about by both the nervous system and endocrine system. The nervous system works by the generation and transmission of electrical impulses while the endocrine system works by secreting chemical messengers called hormones. These systems complement the action of each other to control and coordinate different functions in our body. For example, when an emergency stimulus is detected by the nervous system, the stimulus is received and analyzed by the central nervous system that sends messages to effectors to provide a proper response. At the same time, the sympathetic nervous system activates the adrenal gland to release adrenaline that prepares the body by increasing heart rate, blood pressure, respiration and dilates the pupil, etc. Thus, both these systems interact and work together to produce an effective response.  

Answer:

In animals, chemical coordination is coordinated by hormones. The organ system responsible for the synthesis and regulation of these hormones is known as the endocrine system. Hormones are secreted in very less amount by the endocrine glands. These glands being ductless, the secretions directly mix into the bloodstream. From there it moves to specific target organs where it shows its effects. For example, growth hormone is synthesized by the pituitary gland which mainly acts on the bones of a developing child and increases the height of the child.

Answer:

The dendrites contain the receptors for the neurotransmitters while the axon terminals have synaptic vesicles that are filled with the neurotransmitters. So, when the impulse is generated, the synaptic vesicles fuse with the membranes of the synaptic knobs of the axon terminal and the neurotransmitters are released in the synaptic cleft. These are then sensed by the receptors present on the dendrites of the postsynaptic neuron. As dendrites do not release the neurotransmitters, the impulse cannot travel from the dendrites of one neuron to the axonal end of the other neuron. It is always unidirectional, that is, from the axonal end of the pre-synaptic neuron to the dendrites of the post-synaptic neurons.

                                   Diagram of the synapase