Important questions topics for class 10 science chapter 7 – Control and Coordination are:
- Nervous system
- Reflex action
- Voluntary action
- Involuntary action
- The human brain
- Hormones in animals
- The feedback mechanism
- Electrical impulses
Below are some of the important questions for class 10 science chapter 7 – Control and Coordination from an examination point of view.
Class 10 Science Important Questions Chapter 7 – Control and Coordination
Q1. Write the main functions of the following :
(a) sensory neuron
(c) vertebral column
(d) motor neuron.
(a) Sensory neuron occur in sense organs and receive stimuli through their dendrites. The sensory neurons transmit impulses towards the central nervous system (brain and spinal cord) with the help of their axons.
(b) Cranium : The bones of cranium or brain box protect the brain from mechanical injury.
(c) Vertebral column : Major function of the vertebral column is protection of the spinal cord and carries the weight of the upper body.
(d) Motor neuron: The dendrites of these neurons synapse with axons of interneurons in central nervous system. They transmit impulses from central nervous system towards effectors (muscles or glands). The latter respond to stimuli.
Q2. (a) Define reflex arc.
(b) Trace the sequence of events which occur in our body when a bright light is focussed on your eyes.
(a) The pathway taken by the nerve impulses in a reflex action, from receptor organ to spinal cord and back to effector organ of reflex action is called reflex arc. Receptor organ could be a sense organ such as eyes, skin, etc., and effector organ could be muscles, glands, etc.
(b) When a bright light is focussed on eye, receptor cell receives the stimulus and an impulse is generated. This impulse is passed on to sensory neuron, then it goes to brain, brain sends the impulse to the motor neuron which contracts the pupil. Sequence of events can be summarised as : Photoreceptors in eye → Sensory (Receptor) neuron → Brain → Motor (Effector) neuron → Eye muscle → Constriction of pupils
Q3. Mention three major regions of brain. Write one function of each.
Brain is divided into three main regions forebrain, midbrain and hindbrain.
(i) Forebrain consists of cerebrum, olfactory lobes and diencephalon. Its main function is thinking and controlling various activities such as touch, smell, hearing, speech and sight.
(ii) Midbrain controls reflex movements of the head, neck and trunk in response to visual and auditory stimuli.
(iii) Hindbrain has three centres called pons, cerebellum and medulla. This part is responsible for regulating respiration, maintaining posture and balance of body and controlling involuntary actions such as heartbeat, breathing, swallowing, coughing, sneezing, vomiting, etc.
Q4. State the two types of movements seen in plants. Give one example of each type.
Two types of movements seen in plants are:
(i) Nastic movements are movements independent of growth that are non-directional and occur due to turgor changes, e.g., closing of leaves in response to touch stimulus in ‘touch me not’ plant.
(ii) Tropic movements or tropism are movements due to growth, that are directional and very slow, e.g., movement of a part of the plant in response to light.
Q5. What are plant hormones? Name the plant hormones responsible for the following :
(i) Growth of stem
(ii) Promotion of cell division
(iii) Inhibition of growth
(iv) Elongation of cells
Plant hormones or phytohormones are chemical substances produced naturally in plants and capable of translocation and regulating one or more physiological processes when present in low concentration. These are also known as plant growth substances or plant growth regulators.
The plant hormones responsible for different functions are as follows:
(i) Growth of stem : Gibberellins (Gibberellic acid) promote growth in stems.
(ii) Promotion of cell division : Cytokinins promote cell division in plants.
(iii) Inhibition of growth : ABA (Abscisic acid) promotes dormancy in seeds as well as in buds and thus inhibits growth.
(iv) Elongation of cells : Auxin and cytokinin both cause cell elongation.
Q6. Define phototropism. Name the plant hormone which is responsible for phototropism.
Phototropism is the movement of a part of the plant in response to light. Shoots generally grow towards light and are said to be positively phototropic, while roots grow away from light and are said to be negatively phototropic.
The growth movement of the plant part (stem) is caused by the action of auxin hormone. Auxin causes cell elongation. Thus, causing growth of stem towards the light stimulus.
Q7. (a) How does chemical coordination take place in animals?
(b) It is advised to use iodised salt. Give reason.
(a) The endocrine system consists of specialised glands (endocrine glands) which brings about control by sending chemical messengers termed hormones. These glands secrete hormones directly into the blood. Hormones reach the target organs via blood and regulate the activities of these organs, thus coordinating the functioning of living organisms and also their growth.
(b) Iodine is necessary for the making of thyroxine hormone by thyroid gland. Therefore, deficiency of iodine in the diet can cause deficiency of thyroxine hormone in the body.
Q8. Name the hormone required for the following. Also mention the name of endocrine gland from which that hormone is secreted:
(a) Lowering of blood glucose.
(b) Development of moustache and beard in human males.
(c) Metabolism of carbohydrates, fats and proteins.
(a) The hormone that lowers blood sugar level is insulin. The function of insulin hormone is to lower the blood sugar level (or blood glucose level, i.e., it controls the metabolism of sugar. It is secreted by the endocrine part of pancreas called islets of Langerhans.
(b) Testes secretes the male sex hormone called testosterone, which is responsible for development of male sex organs and male features such as deeper voice, moustache, beard and body hair.
(c) Thyroxine hormone is synthesized by thyroid gland. Thyroxine controls the rate of metabolism of carbohydrates, fats and proteins.
Q9. (a) Name one organ each where growth hormone is synthesized in man and plant.
(b) List the sequence of events that occur when a plant is exposed to unidirectional light, leading to bending of a growing shoot. Also name the hormone and the type of movement.
(a) In man, growth hormone is synthesized by pituitary gland which is present below the brain. Growth hormone controls the growth of human body.
In plants, auxins promote the plant growth. Auxins are produced by growing apices of the stems and roots. They migrate to the regions of their action, and initiate cell division and cell elongation.
(b) (i) When a plant is exposed to unidirectional light, the shoot tips synthesize phytohormone called auxin.
(ii) Auxins slowly diffuse towards the shady side.
(iii) As auxins help the plant to grow, cells on the shady side grow longer than the ones which are exposed to light.
(iv) Hence, causing the plant to bend towards light. This type of movement caused due to hormone auxin is called phototropism.
Shoots generally grow towards the light hence show positive phototropism and roots grow away from light and show negative phototropism.
Q10. (a) Name the hormone which is released into the blood when its sugar level rises. Explain the need of Chemical communication in multicellular organisms the organ which produces this hormone and its effect on blood sugar level. Also mention the digestive enzymes secreted by this organ with one function of each.
(b) Explain the need of Chemical communication in multicellular organisms.
(a) Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level. Insulin is a hormone produced by the a-cells that regulates glucose levels in the blood.
In order for multicellular organisms to function properly, their cells must communicate. For instance, your muscles must contract when your brain sends a message to contract.
Pancreas produces insulin and p-cells which increase glucose in blood. It also – produces digestive enzyme (pancreatic amylase).
(b) Cell-to-cell signaling is a critical component of coordinating cellular activities. Through this communication, messages are carried from signaling cells to receiving cells, also known as target cells. This signaling occurs with proteins and other types of signaling molecules. Other things which happens in our body due to cell communication are – growth and development, cellular reproduction, tissue repair, sensing pain, etc.