Medulla oblongata controls
- Smelling
- Beating of heart and respiratory movement
- Intelligence and will power
- Balancing of the body
Answer
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.
Balance of body is controlled by
- Spinal cord
- Cerebellum
- Cerebrum
- Medulla
Answer
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.
The smell of good food causes watering of your mouth. It is
- Natural reflex
- Acquired reflex
- Inborn reflex
- Ordinary reflex
Answer
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.
The structural and functional unit of nervous system is
- Axon
- Nephron
- Neuron
- Dendron
Answer
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.
Peripheral nervous system consists of different types of nerves which connect the central nervous system to all parts of the body. Cranial nerves, spinal nerves, sympathetic and parasympathetic nerves are all connected to different parts of the body. Which of the following does not belong to cranial nerves ?
- Olfactory nerves
- Auditory nerves
- Optic nerves
- Sympathetic nerves
Answer
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.
Ayush, a student of class 8 was preparing for his biology annual exam but could not understand the terms Receptor, Effector, Stimulus and Response. Which of the following statements explains 'receptor' ?
P. Receptors are sense organs.
Q. Receptors send impulses to CNS through sensory nerves.
R. Receptors receive messages from the central nervous system.
- Only R
- Only Q
- Only P and R
- Only P and Q
Answer
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.
Assertion (A): Neurons are the basic structural unit of nervous system, located in the brain and spinal cord only.
Reason (R): Brain and spinal cord are the parts of the central nervous system which coordinate all external and internal activities of the human body.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
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.
Assertion (A): Synapse is the junction between two neurons which communicates impulses/ messages.
Reason (R): Neurons must be connected with each other through some means in order to transmit the unidirectional flow of impulses.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
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.
Assertion (A): The glands and muscles are considered as effector organs.
Reason (R): Muscles and glands are highly affected by the impulses carried through the sensory nerves from sense organs to the central nervous system (brain/ spinal cord).
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
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.
Assertion (A): The sympathetic and parasympathetic nervous systems are antagonistic (opposite) in their actions.
Reason (R): Both systems are part of the autonomic nervous system that function without conscious control.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
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.
Assertion (A): The arrangement of white and grey matter is reversed in spinal cord from that in the brain.
Reason (R): In brain, the outer portion is white and the inner portion is grey. In spinal cord, the outer portion consists of cytons of neurons whereas the inner portion contains the axons of neurons.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
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.
Name:
(a) The long, extended process of a neuron.
(b) The point of contact between two neurons.
(c) The kind of nerve which carries both sensory and motor neurons.
(d) The nerve which connects the eyes to the brain.
(e) The nerve which connects the nose to the brain.
(f) The nerve which connects the ears to the brain.
(g) Two sub-divisions of the peripheral nervous system.
(h) Two parts of the autonomic nervous system.
Answer
(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
You are driving your bicycle at a fast speed. Suddenly, a small boy comes in front of your cycle and without wasting any time in thinking, you immediately apply the brakes and the accident is avoided. What name is given to such an action ?
Answer
This is a Conditioned or Acquired Reflex action. This reflex is one which is developed during the lifetime due to experience or learning.
Name the three kinds of neurons
Answer
Three kinds of neurons:
- Sensory Neurons
- Motor Neurons
- Association Neurons
Name the three kinds of nerves
Answer
Three kinds of nerves:
- Sensory Nerves
- Motor Nerves
- Mixed Nerves
Name the three main parts of the brain
Answer
Three main parts of the brain:
- Cerebrum
- Cerebellum
- Medulla Oblongata
Name the two types of reflexes
Answer
Two types of reflexes:
- Natural reflexes
- Conditioned reflexes
Name the two types of effectors
Answer
Two types of effectors:
- Muscle
- Gland
Define Coordination.
Answer
The interlinking of various activities and organs of a living being as per the needs of the body internally or externally is called coordination.
Define Synapse.
Answer
A synapse is a small junction used for communication between two neurons.
Define Impulse.
Answer
An impulse is a wave of electrical disturbance that runs through the nerves.
Define Reflex action.
Answer
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.
Define Reflex arc.
Answer
The shortest pathway of the nerve impulse from a receptor to the effector which makes a reflex action possible is called a reflex arc.
Write one important role of Cerebrum.
Answer
Intelligence and memory.
Write one important role of Cerebellum.
Answer
Muscular Coordination.
Write one important role of Medulla oblongata.
Answer
Breathing and digestion.
Write one important role of Receptors.
Answer
Receive the stimulus.
Write one important role of Spinal cord.
Answer
Controls reflexes below the neck.
Write the specific terms/structures for the ‘pathway of a reflex arc’ in a proper logical sequence, starting with stimulus and ending with response/reflex action.
Answer
'Pathway of a reflex arc' is shown below:
Differentiate between the following pairs of terms on the basis of what is indicated within the brackets :
Stimulus and response (definition)
Answer
Difference between Stimulus and Response on the basis of definition:
| Stimulus | Response |
|---|---|
| Any change in the environment that usually results in change in the activity of the body. | The activity of the body due to the stimulus. |
Differentiate between the following pairs of terms on the basis of what is indicated within the brackets :
Receptor and Effector (examples)
Answer
Difference between Receptor and Effector on the basis of examples:
| Receptor | Effector |
|---|---|
| The nerve cells in the skin that receive the stimulus are receptors. Other examples are eyes, ears and nose. | Muscles and glands are effectors. For example, the muscle of the hand receiving the command from the brain is an effector. |
Differentiate between the following pairs of terms on the basis of what is indicated within the brackets :
Motor nerve and Sensory nerve (function)
Answer
Difference between Motor nerve and Sensory nerve on the basis of their function:
| Motor Nerve | Sensory Nerve |
|---|---|
| Motor nerve carries impulses from the brain and spinal cord to the muscles and glands. | Sensory nerve carries impulses from the sense organs to the spinal cord or brain. |
Differentiate between the following pairs of terms on the basis of what is indicated within the brackets :
Cranial and Spinal nerves (number in pairs)
Answer
Difference between Cranial and Spinal nerves on the basis of their number in pairs:
| Cranial Nerves | Spinal Nerves |
|---|---|
| There are 12 pairs of cranial nerves. | There are 31 pairs of spinal nerves. |
Differentiate between the following pairs of terms on the basis of what is indicated within the brackets :
Cerebrum and Medulla oblongata (function)
Answer
Difference between Cerebrum and Medulla oblongata on the basis of their function:
| Cerebrum | Medulla oblongata |
|---|---|
| The cerebrum is the seat of intelligence, consciousness and will power. It controls all the voluntary activities. | Medulla oblongata controls the activities of the internal organs. |
Differentiate between the following pairs of terms on the basis of what is indicated within the brackets :
Cerebrum and Spinal cord (arrangement of white and grey matter)
Answer
Difference between Cerebrum and Spinal cord on the basis of arrangement of white and grey matter:
| Cerebrum | Spinal cord |
|---|---|
| In Cerebrum, the outer portion contains grey matter and inner portion contains white matter. | In Spinal cord, the inner part contains grey matter and the outer part contains white matter. |
Draw a neat and labeled diagram of a neuron and answer the following questions :
(a) What are the two main parts of a neuron?
(b) Is this structure unicellular or multicellular?
(c) Which part of the neuron contains nucleus?
(d) Name the two parts of the human body where neurons are found abundantly.
(e) How are neurons significant to us?
Answer
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.
With the help of a suitable example, describe reflex action.
Answer
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.
Briefly differentiate between the following by giving examples:
Voluntary and involuntary action.
Answer
Difference between Voluntary and involuntary action is given below:
| Voluntary Action | Involuntary Action |
|---|---|
| Voluntary actions occur knowingly. | Involuntary actions occur unknowingly. |
| Cerebrum controls voluntary actions. | Medulla oblongata and spinal cord control involuntary actions. |
| Eating apple, watching TV are examples of voluntary actions. | Breathing, beating of heart are examples of involuntary actions. |
Briefly differentiate between the following by giving examples:
Inborn and acquired reflexes.
Answer
Difference between Inborn and acquired reflexes is given below:
| Inborn Reflexes | Acquired Reflexes |
|---|---|
| No previous experience or learning is required for inborn reflexes. | Acquired reflexes develop with experience and learning during the lifetime. |
| Blinking, coughing, sneezing, vomiting are examples of inborn reflexes. | Typing on the keyboard, playing a musical instrument are examples of acquired reflexes. |
Christopher was cycling downhill at a good speed when a cat suddenly came in front of him out of nowhere. Before he could even think, he hit the brake and stopped just in time. No harm was done to the cat. Later he wondered how his body reacted so quickly even though he didn't make a conscious decision.
(a) What is the term used for such an immediate, automatic action?
(b) Which part of the central nervous system controls this action?
(c) Which major organ of the nervous system is not involved in such actions?
(d) Enlist the correct pathway of the action through which Christopher's body responded so quickly.
Answer
(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