Question 1

Briefly describe the structure of the Brain

Accepted Answer

The brain is the central organ of the nervous system and is composed of three main parts: forebrain, midbrain, and hindbrain. It is protected by the skull and covered by three meninges. The brain consists of grey matter (neuronal cell bodies) on the surface and white matter (myelinated axons) inside. The forebrain includes the cerebrum and diencephalon, the midbrain connects the forebrain and hindbrain, and the hindbrain includes the cerebellum, pons, and medulla oblongata. — The brain's structure is organized into distinct regions with specific functions. The cerebrum controls voluntary actions and intelligence, the diencephalon regulates sensory input and autonomic functions, the midbrain acts as a relay center, and the hindbrain controls balance, coordination, and vital functions.

Question 2

Compare the following:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
(b) Resting potential and action potential

Accepted Answer

(a) CNS vs PNS:
- CNS consists of brain and spinal cord, while PNS consists of all nerves outside CNS.
- CNS processes information; PNS transmits signals to and from CNS.
- CNS is protected by skull and vertebral column; PNS is not.

(b) Resting potential vs Action potential:
- Resting potential is the electrical potential difference across the membrane of a neuron at rest (~ -70 mV).
- Action potential is a rapid, temporary change in membrane potential that propagates along the neuron.
- Resting potential is maintained by Na+/K+ pump; action potential involves depolarization and repolarization due to ion movements. — The CNS and PNS differ in structure and function, with CNS being the control center and PNS the communication network. Resting potential is the baseline electrical state, while action potential is the signal transmitted along neurons.

Question 3

Explain the following processes:
(a) Polarisation of the membrane of a nerve fibre
(b) Depolarisation of the membrane of a nerve fibre
(c) Transmission of a nerve impulse across a chemical synapse

Accepted Answer

(a) Polarisation:
At rest, the nerve fibre membrane is polarised due to unequal distribution of ions. The inside is negatively charged relative to the outside (~ -70 mV). This is maintained by the Na+/K+ pump which pumps 3 Na+ out and 2 K+ in, and by the selective permeability of the membrane.

(b) Depolarisation:
When a stimulus is applied, voltage-gated Na+ channels open, allowing Na+ to enter the neuron, making the inside positive relative to outside. This reversal of polarity is called depolarisation and initiates the action potential.

(c) Transmission across chemical synapse:
The nerve impulse reaches the synaptic terminal, causing Ca2+ channels to open. Ca2+ influx triggers synaptic vesicles to release neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic membrane, causing ion channels to open and generating a new impulse in the postsynaptic neuron. — Polarisation is the resting state with negative inside membrane potential. Depolarisation is the reversal of this potential due to Na+ influx. Synaptic transmission involves chemical messengers (neurotransmitters) crossing the synapse to propagate the signal.

Question 4

Draw labelled diagrams of the following:
(a) Neuron
(b) Brain

Accepted Answer

(a) Neuron:
A neuron consists of the cell body (soma) containing the nucleus, dendrites which receive signals, and a long axon which transmits impulses. The axon may be covered by myelin sheath with nodes of Ranvier.

(b) Brain:
The brain diagram should show the forebrain (cerebrum and diencephalon), midbrain, and hindbrain (cerebellum, pons, medulla). Label parts like cerebrum, cerebellum, medulla oblongata, spinal cord, etc. — Diagrams should clearly label all parts as per the textbook, showing the structure and organization of neurons and brain regions.

Question 5

Write short notes on the following:
(a) Neural coordination
(b) Forebrain
(c) Midbrain
(d) Hindbrain
(e) Synapse

Accepted Answer

(a) Neural coordination:
It is the process by which the nervous system controls and integrates the activities of different parts of the body through nerve impulses.

(b) Forebrain:
The forebrain includes the cerebrum and diencephalon; it controls voluntary actions, sensory perception, and higher mental functions.

(c) Midbrain:
Acts as a relay center for auditory and visual information between forebrain and hindbrain.

(d) Hindbrain:
Includes cerebellum, pons, and medulla oblongata; controls balance, coordination, and vital functions like breathing.

(e) Synapse:
A junction between two neurons where nerve impulses are transmitted chemically via neurotransmitters. — Each note briefly explains the structure and function of the given term as per the textbook.

Question 6

Give a brief account of Mechanism of synaptic transmission.

Accepted Answer

Synaptic transmission is the process by which a nerve impulse is transmitted across a synapse from one neuron to another. When an action potential reaches the synaptic terminal, voltage-gated Ca2+ channels open, allowing Ca2+ ions to enter. This causes synaptic vesicles containing neurotransmitters to fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic membrane, causing ion channels to open and generating a new action potential in the postsynaptic neuron. The neurotransmitter is then degraded or reabsorbed to terminate the signal. — The mechanism involves electrical to chemical signal conversion and back to electrical, ensuring unidirectional transmission of impulses.

Question 7

Explain the role of  $Na^{+}$  in the generation of action potential.

Accepted Answer

Sodium ions (Na+) play a crucial role in the generation of action potential. When a neuron is stimulated, voltage-gated Na+ channels open, allowing Na+ to rush into the neuron due to the electrochemical gradient. This influx of Na+ causes depolarisation of the membrane, reversing the membrane potential from negative to positive inside. This change initiates the action potential which propagates along the neuron. Subsequently, Na+ channels close and K+ channels open to repolarise the membrane. — Na+ influx is responsible for the rising phase of the action potential, making the inside of the neuron positive and enabling signal transmission.

Question 8

Differentiate between:
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Thalamus and Hypothalamus
(d) Cerebrum and Cerebellum

Accepted Answer

(a) Myelinated vs Non-myelinated axons:
- Myelinated axons have a myelin sheath that insulates and speeds up impulse conduction via saltatory conduction.
- Non-myelinated axons lack myelin sheath and conduct impulses more slowly.

(b) Dendrites vs Axons:
- Dendrites receive signals and are short, branched.
- Axons transmit signals away from the cell body and are long.

(c) Thalamus vs Hypothalamus:
- Thalamus acts as a relay station for sensory impulses.
- Hypothalamus controls autonomic functions, temperature, hunger, and endocrine system.

(d) Cerebrum vs Cerebellum:
- Cerebrum controls voluntary actions, intelligence, memory.
- Cerebellum controls balance and coordination. — Each pair is contrasted based on structure and function as per the textbook.

Question 9

Answer the following:
(a) Which part of the human brain is the most developed?
(b) Which part of our central neural system acts as a master clock?

Accepted Answer

(a) The cerebrum is the most developed part of the human brain.
(b) The hypothalamus acts as the master clock of our central nervous system, regulating circadian rhythms. — The cerebrum is responsible for higher mental functions and is largest in humans. The hypothalamus controls biological rhythms and endocrine functions.

Question 10

Distinguish between:
(a) afferent neurons and efferent neurons
(b) impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre
(f) cranial nerves and spinal nerves.

Accepted Answer

(a) Afferent vs Efferent neurons:
- Afferent neurons carry impulses from sensory receptors to CNS.
- Efferent neurons carry impulses from CNS to effectors.

(b) Impulse conduction in myelinated vs unmyelinated nerve fibres:
- Myelinated fibres conduct impulses faster via saltatory conduction jumping between nodes of Ranvier.
- Unmyelinated fibres conduct impulses slower by continuous conduction.

(f) Cranial nerves vs Spinal nerves:
- Cranial nerves emerge from the brain and mainly serve head and neck.
- Spinal nerves emerge from spinal cord and serve the rest of the body. — Differences are based on direction of impulse, speed of conduction, and anatomical origin and function.

Question 11

Which of the following best describes the primary function of the neural system in animals?

Accepted Answer

To detect, receive and transmit different kinds of stimuli for coordination — The neural system is composed of specialized cells called neurons that detect, receive, and transmit stimuli. It provides an organized network for rapid coordination among organs, essential for maintaining homeostasis.

Question 12

During physical exercise, which of the following organ systems work together to meet the increased energy demand?

Accepted Answer

Muscles, lungs, heart, blood vessels, and kidneys — During physical exercise, muscles require more energy, increasing oxygen demand. Lungs increase respiration rate, heart beats faster, blood vessels increase flow, and kidneys adjust filtration. These organs coordinate to maintain homeostasis.

Question 13

The human neural system is divided into which two main parts?

Accepted Answer

Central neural system and peripheral neural system — The human neural system is primarily divided into the central neural system (CNS), consisting of brain and spinal cord, and the peripheral neural system (PNS), which includes all nerves associated with CNS.

Question 14

Which type of nerve fibers in the peripheral neural system transmit impulses from tissues and organs to the central neural system?

Accepted Answer

Afferent fibers — Afferent nerve fibers carry sensory impulses from peripheral tissues and organs towards the CNS, enabling the brain and spinal cord to process sensory information.

Question 15

The autonomic neural system is subdivided into which two systems that generally have opposing effects?

Accepted Answer

Sympathetic and parasympathetic neural systems — The autonomic neural system is divided into sympathetic and parasympathetic systems, which generally have antagonistic effects to maintain balance in involuntary body functions.

Neural Control and Coordination

Neural Control and Coordination — Study Notes

18.1 Neural System

18.2 Human Neural System

18.3 Neuron as Structural and Functional Unit of Neural System

Practice Questions — Neural Control and Coordination

All 19 Chapters in Biology