Nervous System

Beating of heart and respiratory movement

Reason — Medulla oblongata controls breathing, heart function, blood vessel function, digestion, sneezing, and peristalsis of the alimentary canal, etc.
Smelling is controlled by the olfactory region of the forebrain. Intelligence and will power is controlled by the cerebrum. Balancing of the body is controlled by the cerebellum.

Cerebellum

Reason — Body balance and muscular coordination is controlled by the cerebellum of the brain.
Spinal cord controls reflex actions and carries messages between the brain and body. Cerebrum controls thinking, memory, intelligence, emotions, will power, and voluntary actions. Medulla oblongata controls involuntary activities such as heartbeat, breathing, swallowing, and blood pressure.

Acquired reflex

Reason — Salivation on smelling good food is an acquired reflex that occurs because our brain remembers the taste of the food due to a previous experience.
Smelling food and salivation is not purely natural because it develops strongly through experience and association. Good food smell is not present by birth.

Neuron

Reason — Neurons are the structural and functional unit of the nervous system.
The axon is a long fibre-like part of a neuron. Nephron is the structural and functional unit of the kidney. Dendrons are branched extensions of a neuron.

Sympathetic nerves

Reason — Cranial nerves emerge from the brain. Some of the cranial nerves are — the olfactory (for nose), optic (for eyes) and auditory (for ears). While cranial nerves are a part of Somatic nervous system, Sympathetic nerves are a part of Autonomic nervous system.

Only P and Q

Reason — Receptors are the sense organs that receive the stimulus. They send impulses to CNS through sensory nerves. For example, eyes, ears, skin, etc.
Receiving messages from the CNS is the work of effectors (muscles and glands), not receptors.

A is false but R is true.

Explanation — A is false because though neurons are the basic structural and functional units of the nervous system, but neurons are not found only in the brain and spinal cord.
R is true as the brain and spinal cord together form the central nervous system (CNS). They control and coordinate body activities.

Therefore, A is false but R is true is the correct option.

Both A and R are true and R is the correct explanation of A.

Explanation — A is true because at synapse, the message is transmitted from the axon of one neuron to the dendrites of the next neuron.
R is true as messages relayed in this manner from one neuron to the next allow the unidirectional flow of impulses.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

A is true and R is false.

Explanation — A is true as muscles and glands are called effector organs because they carry out the response when they receive signals from the nervous system.
R is false as muscles and glands respond to impulses sent from the CNS via motor nerves, not sensory nerves.

Therefore, A is true and R is false is the correct option.

Both A and R are true but R is not the correct explanation of A.

Explanation — A is true because the sympathetic and parasympathetic nervous systems work opposite to each other. For example, the sympathetic nervous system dilates the pupil and accelerates the heart rate, whereas the parasympathetic nervous system constricts the pupil and slows down the heart rate.
R is true because both systems are parts of the autonomic nervous system (ANS) and function without conscious control. However, this does not explain why they are antagonistic in action.

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

A is true and R is false.

Explanation — A is true because in the cerebrum of the brain, the outer portion contains grey matter and the inner portion contains white matter, whereas in the spinal cord this arrangement is reversed.
R is false because it states the arrangement incorrectly. In the brain, the outer portion is grey matter and the inner portion is white matter. In the spinal cord, the inner part is grey matter made up of cytons of neurons, while the outer part is white matter made up of axons.

Therefore, A is true and R is false is the correct option.

(a) Axon

(b) Synapse

(c) Mixed nerve

(d) The Optic nerve

(e) Olfactory nerve

(f) Auditory nerve

(g) Somatic nervous system and Autonomic nervous system.

(h) Sympathetic and Parasympathetic systems

This is a Conditioned or Acquired Reflex action. This reflex is one which is developed during the lifetime due to experience or learning.

Three kinds of neurons:

1. Sensory Neurons
2. Motor Neurons
3. Association Neurons

Three kinds of nerves:

1. Sensory Nerves
2. Motor Nerves
3. Mixed Nerves

Three main parts of the brain:

1. Cerebrum
2. Cerebellum
3. Medulla Oblongata

Two types of reflexes:

1. Natural reflexes
2. Conditioned reflexes

Two types of effectors:

1. Muscle
2. Gland

The interlinking of various activities and organs of a living being as per the needs of the body internally or externally is called coordination.

A synapse is a small junction used for communication between two neurons.

An impulse is a wave of electrical disturbance that runs through the nerves.

Reflex action is the quick, immediate and automatic response to a stimulus without the involvement of the brain. It is usually controlled by the spinal cord.

The shortest pathway of the nerve impulse from a receptor to the effector which makes a reflex action possible is called a reflex arc.

Intelligence and memory.

Muscular Coordination.

Breathing and digestion.

Receive the stimulus.

Controls reflexes below the neck.

'Pathway of a reflex arc' is shown below:

Difference between Stimulus and Response on the basis of definition:

Difference between Receptor and Effector on the basis of examples:

Difference between Motor nerve and Sensory nerve on the basis of their function:

Difference between Cranial and Spinal nerves on the basis of their number in pairs:

Difference between Cerebrum and Medulla oblongata on the basis of their function:

Difference between Cerebrum and Spinal cord on the basis of arrangement of white and grey matter:

Labeled diagram of a neuron is shown below:

(a) Axon and Cyton

(b) Unicellular

(c) Cyton

(d) Brain and Spinal cord

(e) Neurons are significant to us as they are the fundamental building blocks of the nervous system. Neurons carry impulses between sense organs and brain or spinal cord as well as between themselves. They keep us informed about the outside world and bring about control and coordination in our body. They also help in regulating our involuntary activities.

The peripheral nervous system and spinal cord together control certain actions where the brain is not involved, e.g. when we touch a hot object or get pricked by a pointed object, we instantly remove our hand, without thinking about it. Such an action is called a reflex action.

Difference between Voluntary and involuntary action is given below:

Difference between Inborn and acquired reflexes is given below:

(a) The immediate and automatic action is called a reflex action.

(b) This action is mainly controlled by the spinal cord.

(c) The brain (especially cerebrum) is not directly involved in controlling reflex actions.

(d) The correct pathway of the action through which Christopher's body responded so quickly is :

Stimulus → Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector → Response