Previous year questions: Neural Control and Coordination
Neural Control and Coordination36 min readLesson 5 of 5
These ten questions come from the NCERT Exemplar chapter on neural control and coordination, the only official previous year source available for Class 11 Biology. The rationalised textbook keeps the neural system, the neuron, the impulse, the synapse and the brain, so the set is drawn from those sections. Marks follow the book convention: 1 mark MCQ, 2 marks very short answer, 3 marks short answer and 5 marks long answer. Each heading quotes the Exemplar chapter and question number.
Q1 (NCERT Exemplar, 1 mark; Chapter 21, Multiple Choice 1)
Chemicals which are released at the synaptic junction are called what?
Answer: The chemicals released at the synaptic junction are called neurotransmitters. They are stored in the synaptic vesicles of the presynaptic knob, are released into the synaptic cleft when the impulse arrives, and then bind to receptors on the post-synaptic membrane to start a new electrical change.
Q2 (NCERT Exemplar, 1 mark; Chapter 21, Multiple Choice 3)
The resting membrane potential is maintained by what?
Answer: The resting membrane potential is maintained by the sodium-potassium pump. The pump uses ATP to move three sodium ions out of the axon and two potassium ions into it, so the ion distribution stays unequal and the inside of the membrane remains negative with respect to the outside. The unequal permeability of the membrane to the two ions works together with this pump. If the pump stops working, the gradients run down and the neuron can no longer maintain its resting potential.
Q3 (NCERT Exemplar, 1 mark; Chapter 21, Multiple Choice 4)
The function of our visceral organs is controlled by which system?
Answer: The function of the visceral organs is controlled by the autonomic neural system. It carries impulses to smooth muscles, the heart and the glands, works without conscious control, and its sympathetic and parasympathetic divisions have opposite effects that keep the internal organs working steadily.
Q4 (NCERT Exemplar, 1 mark; Chapter 21, Multiple Choice 6)
Which area of the brain is associated with strong emotions?
Answer: The limbic system is associated with strong emotions. It is a ring of structures around the thalamus and hypothalamus and it is linked with fear, anger, pleasure, sexual behaviour and motivation. The cerebrum handles thinking and memory, but the emotional colour of an experience comes from the limbic system. A smell that brings back a strong memory is a simple example of the two systems acting together.
Q5 (NCERT Exemplar, 2 marks; Chapter 21, Very Short Answer 5)
During resting potential the axonal membrane is polarised. What does this mean?
Answer: A polarised membrane means that the two surfaces of the axonal membrane carry opposite charges, with the outer surface positive and the inner surface negative. The difference in charge across the membrane is the resting potential, and it exists because the membrane is more permeable to potassium ions than to sodium ions and because the sodium-potassium pump keeps the ions unequally distributed.
Q6 (NCERT Exemplar, 2 marks; Chapter 21, Very Short Answer 6)
Name the structures involved in the protection of the brain.
Answer: The brain is protected by the skull and by the three cranial meninges: the dura mater, the arachnoid and the pia mater. The cerebrospinal fluid between the membranes cushions the brain and absorbs shocks, and it also carries nutrients and removes wastes from the nervous tissue. It fills the ventricles inside the brain and the central canal of the spinal cord as well.
Q7 (NCERT Exemplar, 2 marks; Chapter 21, Very Short Answer 8)
What do the grey and white matter in the brain represent?
Answer: The grey matter of the brain is the outer layer of the cerebrum and it contains mainly the cell bodies of neurons, so it looks grey. The white matter lies inside and consists mainly of the myelinated axons that connect different regions of the brain. In the spinal cord the arrangement is reversed, with the grey matter inside and the white matter outside.
Q8 (NCERT Exemplar, 2 marks; Chapter 21, Very Short Answer 9)
Where is the hunger centre located in the human brain?
Answer: The hunger centre is located in the hypothalamus. The hypothalamus is a small region below the thalamus and it controls a group of basic drives, including hunger, thirst and body temperature, and it also influences the pituitary gland. Because it links the nervous system with the endocrine system, it is often called the bridge between the two.
Q9 (NCERT Exemplar, 3 marks; Chapter 21, Short Answer 4)
If someone receives a blow on the back of the neck, what would be the effect?
Answer: A blow on the back of the neck can injure the medulla oblongata, which lies at the base of the brain and joins the spinal cord. The medulla contains the centres that control respiration, the cardiovascular reflexes and gastric secretions, so a severe injury can stop breathing or disturb the heartbeat and the blood pressure. Such an injury is therefore extremely dangerous and may be fatal. The neck must be supported after such a blow, because movement can worsen the damage to the brain stem.
Q10 (NCERT Exemplar, 5 marks; Chapter 21, Long Answer 2)
Name the parts of the human forebrain and indicate their functions.
Answer: The forebrain consists of the cerebrum, the thalamus and the hypothalamus, and it also includes the limbic system. The cerebrum is the largest part and is divided into two hemispheres joined by the corpus callosum. Its outer grey cortex is folded into ridges and grooves and it is the seat of the higher functions: thinking, memory, reasoning, the planning of voluntary movement and the interpretation of the senses. Different areas of the cortex serve different functions, and the two hemispheres specialise to some extent in different tasks.
The thalamus is the chief relay station for sensory impulses. Almost all the sensations coming from the body pass through the thalamus before they reach the cortex, and the thalamus sorts them and directs them to the appropriate area. The hypothalamus is much smaller and lies below the thalamus. It is the control centre for body temperature, hunger, thirst and several other involuntary drives, and it also controls the pituitary gland, which lies just below it and releases hormones that regulate other glands. The limbic system is a ring of structures around the thalamus and hypothalamus, and it is concerned with emotion, motivation, sexual behaviour and memory. Injury to the limbic system can change a person's emotional responses without affecting the ability to think, which shows that feeling and reasoning depend on different but connected parts of the forebrain. The cerebrum, the thalamus, the hypothalamus and the limbic system therefore work as a team, with each part contributing its own share to the final behaviour.
Answer habits for this set
The neural questions reward exact terms more than long answers. Always name the structure and the ion together, for example sodium entering during depolarisation and potassium leaving during repolarisation. Always give the direction of a signal, because dendrites carry it towards the cell body and axons carry it away, and a reflex arc has a fixed order of receptor, afferent neuron, interneuron, efferent neuron and effector. When a brain part is asked, attach one function to it rather than listing its neighbours. When a synapse is asked, do not stop at the word neurotransmitter; add the calcium entry, the vesicles, the cleft, the receptors on the post-synaptic membrane and the removal of the transmitter. These five marks worth of detail are what separate a complete answer from a sketch.
The ten facts to revise last
Before the exam, run through this list. One, the central neural system is the brain plus the spinal cord. Two, the autonomic division supplies smooth muscle, heart and glands, and its two halves oppose each other. Three, dendrites bring signals in and the axon carries them out. Four, myelin is made by Schwann cells, and the gaps are the nodes of Ranvier. Five, the resting membrane is polarised with the outside positive. Six, the sodium-potassium pump moves three sodium ions out for two potassium ions in. Seven, sodium entering the axon causes depolarisation and the action potential. Eight, saltatory conduction jumps between nodes and is faster. Nine, a chemical synapse uses calcium entry, vesicles, the cleft and receptors. Ten, the medulla oblongata controls respiration and the cardiovascular reflexes. These ten statements cover most of the one and two mark questions from this chapter, and each of them can be expanded into a longer answer when the marks are higher.