Chapter 18: Neural Control and Coordination Case Study Questions | biology Class 11 CBSE

ByteNotes

Chapter 18: Neural Control and Coordination Case Study Questions | biology Class 11 CBSE | ByteNotes.in

Case Study

Passage with linked questions

Case Set

Case Set 1

Case Analysis

Passage

Riya is a Class 11 student studying how neurons work. Her teacher explains that a neuron at rest maintains a specific electrical state across its membrane. The axoplasm inside the axon contains high concentrations of potassium ions and negatively charged proteins, while the fluid outside the axon is rich in sodium ions. The teacher further explains that this unequal distribution is not accidental — it is actively maintained by a specific pump that uses energy. The outer surface of the membrane is positively charged and the inner surface is negatively charged. Riya is asked to explain what happens to this state when the neuron receives a stimulus strong enough to trigger a response.

Question 1: What is the term given to the electrical potential difference across the resting plasma membrane of a neuron?

The electrical potential difference across the resting plasma membrane is called the resting potential.
In this state, the outer surface of the axonal membrane is positively charged and the inner surface is negatively charged.
This polarised state is maintained because the axonal membrane is more permeable to K+ and nearly impermeable to Na+ and negatively charged intracellular proteins.

Question 2: Name the pump responsible for maintaining ionic gradients across the resting membrane and describe its mode of action.

The sodium-potassium pump maintains the ionic gradients across the resting axonal membrane.
It actively transports 3 Na+ outward and 2 K+ into the cell, making it an electrogenic pump that uses energy.
This active transport keeps Na+ concentrated outside and K+ concentrated inside, sustaining the resting potential.

Question 3: When a stimulus is applied to the polarised membrane at point A, describe the sequence of ionic events that generate an action potential and explain how the resting potential is subsequently restored.

When a stimulus is applied, the membrane at site A becomes freely permeable to Na+, causing a rapid influx of Na+ into the axoplasm.
This Na+ influx causes depolarisation: the outer surface becomes negatively charged and the inner surface becomes positively charged; the resulting electrical potential difference is called the action potential or nerve impulse.
The rise in Na+ permeability is extremely short-lived and is quickly followed by an increase in permeability to K+; K+ diffuses outward within a fraction of a second, restoring the positive charge on the outer surface and re-establishing the resting potential (repolarisation), making the fibre responsive again.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 2

Case Analysis

Passage

During a neuroscience demonstration, a teacher uses a model synapse to show students how impulses travel between neurons. She explains that the space between the two neurons is filled with fluid and that the neuron sending the signal stores chemicals in tiny vesicles at its terminal end. When the signal arrives, these vesicles move toward the membrane and release their contents into the gap. The receiving neuron has special proteins embedded in its membrane that recognise and bind these released chemicals, after which new signals can be generated. A student notices the teacher mentions that there are actually two kinds of junctions between neurons and asks about the differences.

Question 1: Name the fluid-filled gap between the pre-synaptic and post-synaptic neurons at a chemical synapse.

The fluid-filled gap between the pre-synaptic and post-synaptic neurons at a chemical synapse is called the synaptic cleft.
The synaptic cleft separates the two neuronal membranes and is the space across which neurotransmitters must diffuse.
At electrical synapses, no such gap exists because the two membranes are in very close proximity.

Question 2: Describe the sequence of events at a chemical synapse from the arrival of the action potential to the generation of a new potential in the post-synaptic neuron.

When an action potential arrives at the axon terminal, it stimulates the movement of synaptic vesicles towards the pre-synaptic membrane, where they fuse and release neurotransmitters into the synaptic cleft.
The released neurotransmitters bind to their specific receptors present on the post-synaptic membrane, causing ion channels to open.
Entry of ions through these channels generates a new potential in the post-synaptic neuron that may be either excitatory or inhibitory.

Question 3: Compare electrical and chemical synapses in terms of structural arrangement, mechanism of impulse transmission, and speed. Why are electrical synapses considered rare in the human neural system?

At electrical synapses, the pre- and post-synaptic membranes are in very close proximity with no significant gap, allowing electrical current to flow directly from one neuron to the other, analogous to impulse conduction along a single axon.
At chemical synapses, the membranes are separated by a fluid-filled synaptic cleft; transmission depends on release, diffusion, and receptor binding of neurotransmitters, making it inherently slower.
Transmission across an electrical synapse is always faster than across a chemical synapse; electrical synapses are rare in the human system, likely because chemical synapses provide greater flexibility through excitatory and inhibitory modulation essential for complex neural integration.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 3

Case Analysis

Passage

A neurologist is examining a patient who shows symptoms of poor balance, inability to coordinate hand movements, and difficulty walking in a straight line. Brain imaging reveals a lesion in a specific part of the hindbrain. The neurologist explains to the medical students that this region has a highly folded surface in order to accommodate a large number of neurons in the available space, which allows it to integrate multiple streams of sensory information simultaneously. She notes that another region of the hindbrain — a small structure of fibre tracts — helps connect different brain regions, while a third structure controls automatic life-sustaining functions.

Question 1: Identify the three components of the hindbrain as described in the passage.

The three components of the hindbrain are cerebellum, pons, and medulla oblongata.
The cerebellum has a very convoluted surface to accommodate many more neurons and is the site damaged in the patient described.
Pons consists of fibre tracts that interconnect different regions of the brain, and the medulla contains centres controlling respiration, cardiovascular reflexes, and gastric secretions.

Question 2: Explain why the cerebellum has a highly convoluted surface and relate this structural feature to its functional capacity.

The cerebellum has a very convoluted (folded) surface in order to provide additional space for many more neurons within its limited skull volume.
A larger surface area accommodates more neurons, enabling the cerebellum to receive and integrate complex sensory information from the semicircular canals of the ear and the auditory system.
This increased neuronal capacity allows the cerebellum to precisely coordinate voluntary movements and maintain body balance, which are disrupted when the cerebellum is damaged.

Question 3: The medulla oblongata is described as containing centres that control vital automatic functions. If the medulla were severely damaged, analyse the physiological consequences for the patient, justifying each prediction based on the chapter.

The medulla contains centres that control respiration; damage would impair the automatic regulation of breathing, potentially causing respiratory failure and death if untreated.
Cardiovascular reflex centres in the medulla regulate heart rate and blood pressure; damage would lead to dangerous fluctuations in these parameters, risking cardiac arrest.
The medulla also controls gastric secretions; damage could disrupt digestion and gastrointestinal function. Additionally, since the medulla connects the brain to the spinal cord and forms part of the brain stem, its damage would also sever communication pathways between the brain and spinal cord, with wide-ranging effects on reflex and voluntary functions.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 4

Case Analysis

Passage

A biology teacher describes the human brain to her students using an analogy. She says the brain is like a three-storey building: the top floor handles all the thinking, memory, and decision-making; the middle floor receives and integrates special senses; and the ground floor keeps the body alive by running automatic systems. She then describes how the top floor is the largest and most developed, divided into two wings connected by a bridge of fibres. Each wing has an outer grey layer full of neuron cell bodies and an inner white layer made of insulated fibre tracts. She emphasises that a small region at the base of the top floor acts as both a homeostatic controller and a hormonal regulator.

Question 1: Identify the three major parts of the human brain that correspond to the teacher's analogy of a three-storey building.

The top floor corresponds to the forebrain, which is the largest and most developed region responsible for thinking, memory, and decision-making.
The middle floor corresponds to the midbrain, which receives and integrates visual, tactile, and auditory inputs.
The ground floor corresponds to the hindbrain (pons, cerebellum, medulla), which controls automatic life-sustaining functions such as respiration and cardiovascular reflexes.

Question 2: Explain the structural features of the cerebrum that correspond to the teacher's description of the 'two wings connected by a bridge' and the grey and white layers.

The cerebrum is longitudinally divided into the left and right cerebral hemispheres (the two wings), which are connected by a tract of nerve fibres called the corpus callosum (the bridge).
The outer grey layer is the cerebral cortex, which appears grey because neuron cell bodies are concentrated there; it contains motor areas, sensory areas, and association areas.
The inner white layer is the white matter, formed by myelinated fibre tracts that give an opaque white appearance and connect different brain regions.

Question 3: Identify the 'small region at the base of the top floor' described by the teacher. Analyse all its functions as stated in the chapter and explain how it links the neural and endocrine systems.

The small region at the base of the forebrain is the hypothalamus, which lies at the base of the thalamus.
The hypothalamus contains centres that control body temperature, urge for eating, and urge for drinking, directly contributing to homeostasis.
It contains several groups of neurosecretory cells that secrete hypothalamic hormones, thereby linking the neural system to the endocrine system; along with the limbic system, it also regulates sexual behaviour, expression of emotional reactions such as excitement, pleasure, rage and fear, and motivation.

ByteNotes

Case Study

Passage with linked questions

Case Set

Case Set 5

Case Analysis

Passage

A pharmacology researcher is testing a new compound that selectively inhibits the sodium-potassium pump in neurons. In preliminary trials, neurons exposed to the compound gradually lose their ability to generate action potentials over time. The researcher notes that the compound does not directly block ion channels but affects the active transport mechanism that neurons use to maintain their ionic gradients. The team observes that within minutes of applying the compound, the membrane potential begins to drift toward zero. They also note that neurons with higher baseline activity are affected more quickly. The findings are to be published as evidence that active transport is indispensable for sustained neural function.

Question 1: What ionic gradients does the sodium-potassium pump normally maintain, and what ratio of ions does it transport?

The sodium-potassium pump transports 3 Na+ outward and 2 K+ into the cell in each cycle.
This active transport maintains a high concentration of K+ and negatively charged proteins inside the axon, and a high concentration of Na+ outside.
These ionic gradients are essential for keeping the outer membrane surface positively charged and the inner surface negatively charged, establishing the resting potential.

Question 2: Explain why inhibiting the sodium-potassium pump causes the membrane potential to drift toward zero over time.

Without the pump, Na+ can no longer be actively transported outward; it gradually leaks into the axon along its concentration gradient since the membrane allows some Na+ permeability.
Similarly, K+ leaks out of the axon, reducing the internal K+ concentration that contributes to the negative inner charge.
As both ionic gradients dissipate, the charge difference across the membrane decreases and the membrane potential approaches zero, abolishing the resting potential.

Question 3: Why would neurons with higher baseline activity be affected more quickly by the pump inhibitor? Relate your answer to the role of Na+ in generating each action potential and the pump's function in restoring the resting state.

Each action potential involves a rapid influx of Na+ into the axon during depolarisation; after each impulse, the pump must transport the entered Na+ back out to restore the ionic gradient.
Neurons with higher baseline activity generate action potentials more frequently, meaning they accumulate Na+ inside and lose K+ outside at a faster rate.
When the pump is inhibited, highly active neurons cannot reverse this ion accumulation rapidly enough, so their ionic gradients dissipate more quickly; once the resting potential is lost, the membrane can no longer be depolarised by a stimulus and action potential generation fails, explaining why highly active neurons are affected first.

ByteNotes

Premium Access

Unlock all Case Study sets

You are viewing 5 free case study sets from this chapter. Upgrade to Premium to unlock the remaining 10 sets.

Upgrade to Premium10 questions locked

Chapter sections

Chapter 18: Neural Control and Coordination | Case Study Questions

Passage

Question 1: What is the term given to the electrical potential difference across the resting plasma membrane of a neuron?

Question 2: Name the pump responsible for maintaining ionic gradients across the resting membrane and describe its mode of action.

Question 3: When a stimulus is applied to the polarised membrane at point A, describe the sequence of ionic events that generate an action potential and explain how the resting potential is subsequently restored.

Passage

Question 1: Name the fluid-filled gap between the pre-synaptic and post-synaptic neurons at a chemical synapse.

Question 2: Describe the sequence of events at a chemical synapse from the arrival of the action potential to the generation of a new potential in the post-synaptic neuron.

Question 3: Compare electrical and chemical synapses in terms of structural arrangement, mechanism of impulse transmission, and speed. Why are electrical synapses considered rare in the human neural system?

Passage

Question 1: Identify the three components of the hindbrain as described in the passage.

Question 2: Explain why the cerebellum has a highly convoluted surface and relate this structural feature to its functional capacity.

Question 3: The medulla oblongata is described as containing centres that control vital automatic functions. If the medulla were severely damaged, analyse the physiological consequences for the patient, justifying each prediction based on the chapter.

Passage

Question 1: Identify the three major parts of the human brain that correspond to the teacher's analogy of a three-storey building.

Question 2: Explain the structural features of the cerebrum that correspond to the teacher's description of the 'two wings connected by a bridge' and the grey and white layers.

Question 3: Identify the 'small region at the base of the top floor' described by the teacher. Analyse all its functions as stated in the chapter and explain how it links the neural and endocrine systems.

Passage

Question 1: What ionic gradients does the sodium-potassium pump normally maintain, and what ratio of ions does it transport?

Question 2: Explain why inhibiting the sodium-potassium pump causes the membrane potential to drift toward zero over time.

Question 3: Why would neurons with higher baseline activity be affected more quickly by the pump inhibitor? Relate your answer to the role of Na+ in generating each action potential and the pump's function in restoring the resting state.

Unlock all Case Study sets