Class 10 Biology Chapter 2 - Control and Coordination Important Questions

Class 10 Biology Chapter 2 - Control and Coordination

Most Important Questions :-

 Question 1.

Which is the largest and most prominent part of the brain? 

Answer:

Cerebrum is the largest and most prominent part of the brain.

Question 2

Write the main functions of the following :

(a) sensory neuron

(b) cranium

(c) vertebral column

(d) motor neuron. 

Answer:

(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.

Question 3.

Why does the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron take place but not in the reverse direction? Explain. 

Answer:

At the synapse, (functional junction between neurons) axon terminal comes in close proximity to the dendron terminal of next neuron. Axon terminal is expanded to form pre-synaptic knob and the other dendrite terminal forms post- synaptic depression.

In between the two, lies a narrow fluid filled space called synaptic cleft. As the nerve impulse reaches the pre-synaptic knob, the synaptic vesicles get stimulated to release neurotransmitter in the synaptic cleft. The neurotransmitter molecules diffuse across the gap to come in contact with post-synaptic membrane. In this way, nerve impulse passes across the minute gap to stimulate dendron of other neuron. The synapse acts as a one-way valve to conduct impulse in one direction only. This is so because chemical substance called neurotransmitter is secreted only on one side of the gap, i.e., on axon’s side. It carries impulse across the synapse and passes it to the dendron of the other neuron. In this way, impulses travel across the neurons only in one direction, i.e., from axon of one neuron to dendron of other neuron through a synapse.

Question 4.

(a) Define reflex arc.

(b) Trace the sequence of events which occur in our body when a bright light is focussed on your eyes. 

Answer:

(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.

Question 5.

Mentioh three major regions of brain. Write one function of each. 

Answer:

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.

Question 6.

State one example of chemotropism. 

Answer:

Growth of pollen tube towards the ovule due to chemical stimulus during the process of fertilisation in a flower is an example of chemotropism.

Question 7.

What is meant by tropic movements? 

Answer:

Directional movements or orientations of specific part of a plant in response to external stimuli are called tropisms or tropic movements.

Question 8

What is a plant hormone ? Name four plant hormones. State one function of each.

Answer:

The hormones that control and coordinate the activities in plants are called plant hormones. The four types of plant hormones are: i  Auxins – It promotes cell enlargement and cell differentiation in plants. ii Gibberellines – It helps in breaking the dormancy in seeds and buds. iii Cytokinins – It promotes cell division in plants. iv Abscisic acid – It promotes the dormancy in seeds and buds.