RBSE Class 12 Biology Chapter 26- Nervous system of Humans provides complete information related to important terminologies, including the central nervous system (CNS), peripheral nervous system (PNS), autonomus nervous system (ANS), its different parts, location in the human body along with their functions. This chapter also provides in-depth explanations related to the reflex organs, types of reflex organs, spinal cord, functions of the spinal cord, spinal nerves, cranial nerves, structure and functions of the human brain and much more.
These important questions help students to ace their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and perform their best in the examinations.
The Rajasthan Board Class 12 Solutions are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help students to be well prepared for their upcoming examinations.
RBSE Class 12 Biology Chapter 26 Important Questions
RBSE Biology Chapter 26: MCQ Type Questions
Q.1. What is the unit of the nervous system?
(c) Spinal cord
Sol: (b) Neuron.
Q.2. Temperature controlling centre in the brain of man is _________.
(a) Pituitary gland
(d) All of the above
Sol: (c) Hypothalamus.
Q.3. A function of the parasympathetic nervous system is _________.
(a) Dilation of pupils
(b) Secretion of sugar in the liver
(c) Increase heartbeat
(d) Stimulate secretion of saliva
Sol: (d) Stimulate secretion of saliva.
Q.4.The scientist who worked on conditioned reflex action is _________.
(d) Evan Wilmut
Sol: (b) Pavlov.
Q.5. Number of cranial nerves present in humans are _________.
(a) 10 pairs
Sol: (b) 12pairs.
Q.6. _________ function is to control reflex action.
(a) Spinal cord
Sol: (a) Spinal cord.
Q.7. Number of spinal nerves present in humans are _________.
Sol: (a) 21pairs.
Q.8. Sympathetic and parasympathetic are parts of _________.
(a) Autonomous Nervous system
(b) Peripheral Nervous system
(c) Central nervous system
(d) None of the above
Sol: (a) Autonomous Nervous system.
Q.9. _________ is the longest cell.
(a) Nerve cell
(b) Sensory cell
(c) Ependymal cells
(d) None of the above
Sol: (a) Nerve cell.
Q.10. Which part of the brain is the centre for breathing and swallowing?.
(c) Medulla oblongata
Sol: (c) Medulla oblongata.
RBSE Biology Chapter 26: Short Answer Type Questions.
Q.1. Which are the two parts of the autonomous nervous system?
Sol: The two main parts of the autonomous nervous system are:
- Sympathetic Autonomous Nervous System.
- Parasympathetic Autonomous Nervous System.
Q.2. Write the functions of Cerebrum, Cerebellum, Medulla oblongata and Hypothalamus.
Cerebrum– It controls thinking, argument, planning, memory, etc.
Cerebellum–It controls body balance and muscle coordination.
Medulla oblongata– It controls most of the involuntary activities of the body such as heartbeats, breathing, blood pressure, etc.
Hypothalamus– It is the centre for hunger, thirst and eroticism.
Q.3. What are the main parts of the human brain?
Sol: The main parts of the human brain are:
- Forebrain: It is mainly formed by two parts- Cerebrum and Diencephalon.
- Midbrain: It has two main parts – Corpora Quadrigemina and Cerebral peduncle.
- Hindbrain: It mainly consists of three parts: Cerebellum, Pons VArolli and Medulla Oblongata.
Q.4. Where is the Brain located?
Sol: The brain is enclosed within the skull, which consists of 22 bones. Anatomically, the brain is contained within the cranium and is surrounded by the cerebrospinal fluid, which protects the brain from minor mechanical shocks, jolts and provides the necessary nutrients required by the brain.
Q.5. What is Cerebrospinal Fluid?
Sol: The Cerebrospinal Fluid (CSF) is a fluid that circulates within the skull and spinal cord, filling up hollow spaces on the surface of the brain. Every day around 500ml of cerebrospinal fluid is produced by the specialised ependymal cells.
Q.6. Which are the smallest part and the central region of the brain?
Sol: The midbrain, which consists of tectum and tegmentum is considered the smallest part of the brain. The hindbrain, which is composed of cerebellum, medulla and pons are considered the central region of the human brain.
Q.7. What is Grey and White matter of the human brain?
Sol: A human brain is composed of two types of tissues, which are called the grey matter and white matter. Grey matter consists of various types of cells, which make up the bulk of the brain. White matter is primarily composed of axons, which connect various grey matter areas of the brain with each other.
Q.8. What is the Central Nervous System?
Sol: The central nervous system (CNS) primarily consists of the brain and the spinal cord. This system coordinates and controls various aspects of life. It is one of the primary parts of the nervous system.
Q.9. What is Peripheral Nervous System
Sol: The peripheral nervous system (PNS) primarily consists of the cranial nerves and ganglia present originating from the brain and spinal nerves of the spinal cord. The primary role of the PNS is to connect the central nervous system to the rest of the body, such as the limbs, skin.
Q.10. What is the Nervous System?
Sol: The nervous system or the neural system is a complex network of neurons, which are specialized to carry messages and receive stimulus by the respective organs. The different activities of the living system are controlled and coordinated by the nervous system.
Q.11. What is Midbrain?
Sol: The midbrain is the smallest region of the brain, found at the centre of the brain, beneath the cerebral cortex and above the hindbrain. It is also called the Mesencephalon and is mainly composed of the tectum, cerebral peduncle, tegmentum, cerebral aqueduct, cerebral peduncle, substantia nigra, several nuclei and fasciculi.
Q.12. What are the functions of the parasympathetic autonomous nervous system?
Sol: The functions of the parasympathetic autonomous nervous system are:
- Relaxation of muscles.
- Maintaining homeostasis.
- Activates the “rest and digest” response.
- Involved in the contraction of pupils.
- Controlling the actions of salivation, urination, lacrimation, defecation and digestion.
Q.13. What is an Autonomic Nervous System?
Sol: The autonomous nervous system provides nerves to the involuntary muscles and glands. This nervous system is mainly composed of ganglions and the chains of nerves located on both the lateral sides of the spinal cord. It is further divided into two parts –
- Sympathetic Nervous System.
- Parasympathetic Nervous System.
Q.14.What is a reflex action?
Sol: Automatic, rapid and involuntary response caused by any stimulus in the body is called the reflex action.
For example, Withdrawal of your hands quickly by touching hot objects.
Secretion of saliva from the mouth by sensing the smell of any tasty food.
There are two types of reflexes:
- Simple or Unconditional reflex action.
- Acquired or Conditional reflex action.
Q.15. What is Somatic Neural System?
Sol: The neural system that controls the voluntary actions in the body by transmitting impulses from the central nervous system (CNS) to skeletal muscle cells is called the Somatic neural system (SNS). It consists of a group of somatic nerves.
RBSE Biology Class 12: Long Answer Type Questions
Q.1. What are the differences between a sympathetic and parasympathetic nervous system?
Sol: Differences between a sympathetic and parasympathetic nervous system are :
|Sympathetic Nervous System||Parasympathetic Nervous System|
|Involved in the fight or flight response.||Involved in maintaining homeostasis and also, permits the rest and digest response.|
|The sympathetic system prepares the body for any potential danger.||The parasympathetic system aims to bring the body to a state of calm.|
|Sympathetic system has shorter neuron pathways, hence a faster response time.||Has comparatively longer neuron pathways, hence a slower response time.|
|Increases heartbeat, muscles tense up.||Reduces heartbeat, muscles relax.|
|The pupil dilates to let in more light.||The pupil contracts.|
|Saliva secretion is inhibited.||Saliva secretion increases, digestion increases.|
Q.2. List out the effects of a sympathetic autonomic nervous system.
Sol: The sympathetic nervous system consists of nerves arising from the spinal cord between the neck and waist region. It prepares the body for violent actions against abnormal conditions and is generally stimulated by adrenaline.
Listed below are the effects of a sympathetic autonomic nervous system
- Pupil dilates.
- Increased heartbeat.
- Relaxes urinary bladder.
- Increases blood pressure.
- Excites arrector pili muscle.
- Increases secretion of sweat.
- Increases sugar level in blood.
- Contracts sphincter of the anus.
- Decreases secretion of salivary glands.
- Increases secretion of lacrimal glands.
- Increases secretion of the adrenal gland.
- Decreases secretion of digestive glands.
- Decreases peristalsis of the alimentary canal.
- Constrict peripheral blood vessels but dilates those blood vessels supplying blood to organs connected to an emergency like heart, lungs, brain, etc.
Q.3. Brief out the spinal nerves of the peripheral nervous system?
Sol: The nerves arising from the spinal cord are known as the spinal nerves.
- In humans, there are 31 pairs of spinal nerves.
- These nerves extend from the back portion of medulla oblongata to lumbar regions.
- All spinal nerves are of mixed type as they contain both sensory and motor neurons.
- Every spinal nerve passes out through every two vertebrae of the vertebral column through an intervertebral foramen.
- On the basis of their origin, the spinal nerves are named as listed below in the tabular column.
Description of the human spinal nerves.
|Cervical spinal nerves||8 Pairs||1st vertebrae to below the cervical vertebrae.|
|Thoracic spinal nerves||12 Pairs||Below each thoracic vertebrae on both the sides.|
|Lumbar spinal nerves||5 Pairs||Below each lumbar vertebrae on both the sides.|
|Sacral spinal nerves||5 Pairs||Near the second cervical level of the spinal cord.|
|Coccygeal spinal nerves||1 Pair||In the lower part of the sacral plexus.|
Q.4. Explain in detail about the Reflex action.
Sol: The reflex action is a rapid automatic response to a stimulus without the conscious thought in the body. This response is instantaneous and involuntary.
The reflex action has no control in the brain.
A person withdraws his hand instantly on touching a pointed pin or a hot utensil.
Salivation in the mouth on the smell or thought of the good or any favourite dishes.
There are two different types of reflex actions:
1) Simple or Unconditional reflex action.
They are innate or natural of congenital reflex action, which does not require any learning or any previous information and is not controlled by the brain. This type of reflex action is called the Simple or Unconditional reflex action.
Examples of Simple or Unconditional reflex action are:
- Contraction of a pupil in strong light.
- Closing of eyelids when any object comes closer.
- Instantly coughing when any food particles or any liquid enters into the trachea.
2) Acquired or Conditional reflex action.
This reflex action needs learning training or experience.
Russian scientist of physiology Evan Pavlov explained it by his experiment on a dog.
Evan Pavlov experimented on a dog.
As Evan Pavlov starts ringing a bell just before the food is given to the dog. Later on, he observed that there was salivation in the dog’s mouth on ringing a bell even without giving the food.
Examples of acquired or conditional reflex action are:
- Tying shoelaces even though we are talking to somebody else.
- Students stand up by seeing their class teacher entering the classroom.
- While riding or driving a vehicle, we instantly apply the brake when an object comes in front of a vehicle all of a sudden.
Q.5. What is Spinal Reflex Arc?
Sol: A reflex arc is a pathway that controls a reflex. It can also be defined as the pathway taken by impulse generated at the time of reflex action by neurons.
The main organs of this pathway are:
- Sensory organ: The receptors found on the body, which are stimulated by receiving stimulations from an external or internal stimulus. It includes five receptors- eye, nose, ear, skin and the tongue.
- Sensory cell: This cell carries impulses from the sensory organs to the spinal cord.
- The nerve centre of the spinal cords: It is the centre of actions. It is also called the Interneurons centre of the action
- Motor nerve: It is involved in the transmission and carrying of impulse away towards the spinal cord.
- Effector organs: These organs complete their actions with a response to impulse received through the motor nerve.
Q.6. What are the cranial nerves? Explain in detail with the labelled diagram.
Sol: Nerves that extend throughout the body on both sides emerging directly from the brain and brain stem are called cranial nerves.
There are 12 cranial nerves in the human body. These nerves arise from the brain. The types of cranial nerves are different due to their functions. i.e. these nerves are sensory, motor and mixed.
The below table provides the complete details regarding the different types of cranial nerves along with its origin and functions.
|Optic foramen Cranial Nerves|
|Sensory Type Cranial Nerves|
|Olfactory (I)||Cribriform plate||Smell|
|Vestibulocochlear nerve (VIII)||Internal auditory canal||Hearing and balance|
|Vagus (X)||Jugular foramen||Vagus nerve|
|Mixed Type Cranial Nerves|
|Trigeminal (V)||Superior orbital fissure||Facial sensation|
|Facial (VII)||Internal auditory canal||Facial expression|
|Glossopharyngeal (XI)||Jugular foramen||Oral sensation and taste|
|Motor Type Cranial Nerves|
|Oculomotor (III)||Superior orbital fissure||Eye movement|
|Trochlear (IV)||Superior orbital fissure||Eye movement|
|Abducens (VI)||Superior orbital fissure||Eye movement|
|Accessory (XI)||Jugular foramen||Shoulder elevation and head-turning|
|Hypoglossal (XII)||Hypoglossal||Tongue movement|
Q.7. What is the Nervous System?
Sol: The human nervous system is a complex network comprising the brain, nerves and the spinal cord, which control both voluntary and involuntary actions of the human body. The nervous system transmits messages in the form of electrical impulses through neurons and conveys to our sense organs.
Functions of the Nervous System
- It coordinates and controls different activities of various organs of the body.
- It also controls voluntary muscular activities like running, speaking, etc.
- It provides information to humans about the external environment through the sensory organs.
- It regulates various involuntary activities like heartbeat, breathing, movement of food into the alimentary canal, etc.
Parts of the Nervous System
Nervous System consists of three main types:
- Central nervous system.
This nervous system includes the brain and the spinal cord.
- Peripheral nervous system.
This nervous system includes cranial nerves originating from the brain and the spinal nerves from the spinal cord.
- Autonomous nervous system.
This nervous system comprises – the sympathetic and parasympathetic nervous system.
Q.8. List out the effects of the parasympathetic autonomic nervous system.
Sol: The parasympathetic nervous system is located anterior in the head and neck and posterior in the sacral region. It is mainly involved in re-establishment of normal conditions when violent action is over.
Listed below are the effects of a parasympathetic autonomic nervous system.
- Decreased heartbeat.
- Constriction of pupils.
- Relaxes sphincter of anus.
- Decreases blood pressure.
- Contracts urinary bladder.
- Relaxes arrector pili muscles.
- Decreases secretion of sweat.
- Decreases sugar level in blood.
- Decreased secretion of adrenal glands.
- Increases secretion of salivary glands.
- Decreases secretion of lacrimal glands.
- Increases secretion of digestive glands.
- Increases peristalsis of the alimentary canal.
- Dilates peripheral blood vessels but constricts other blood vessels to reduce blood supply.
Q.9. What is a Peripheral Nervous System?
Sol: Peripheral nervous system involves the parts of the nervous system outside the brain and the spinal cord.
The peripheral nervous system (PNS) is the lateral part of the nervous system that develops from the central nervous system, which connects different parts of the body with the central nervous system (CNS). The peripheral nervous system includes all those nerves arising from the brain and spinal cord.
The primary role of the PNS is to connect the central nervous system to the rest of the body, such as the limbs, skin.
The peripheral nervous system is divided into two parts:
1) Somatic Nervous System
The main function of the somatic nervous system is to transfer impulses from the central nervous system (CNS) to skeletal muscles. It consists of:
- Cranial Nerves
Nerves that extend throughout the body on both sides emerging directly from the brain and brain stem are called cranial nerves. There are 12 cranial nerves in the human body. These nerves arise from the brain. The types of cranial nerves are different due to their functions.
- Spinal Nerves
Nerves arising from the spinal cord are known as the spinal nerves. In humans, there are 31 pairs of spinal nerves, which extend from the back portion of medulla oblongata to lumbar regions. All spinal nerves are of mixed type as they contain both sensory and motor neurons.
2) Autonomic Nervous System
The autonomous nervous system provides nerves to the involuntary muscles and glands. This nervous system is mainly composed of ganglions and the chains of nerves located on both the lateral sides of the spinal cord. It is further divided into two parts –
- Sympathetic Nervous System
- Parasympathetic Nervous System
Q.10. Explain the mechanism of reflex action.
Sol: Reflex action is a sudden and involuntary response to stimuli. It helps organisms to quickly adapt to an adverse circumstance that could have the potential to cause bodily harm or even death. Pulling our hands away immediately after touching a hot or cold object is a classic example of a reflex action.
Mechanism of Reflex Action.
- Fibres of the spinal cord and the motor fibre of the ventral root play a special role in the reflex action.
- For example, Pricking with the pin on the skin stimulates sensations, which stimulates the dendrites of the somatic sensory fibres. These fibres transmit stimuli to the neuron in the dorsal ganglia of the spinal nerve.
- The terminal nodes of these cells send stimulus to the dendrites of the motor nerves, where the sensory induction becomes a motor stimulus.
- The axons of the motor cells are fibres of the ventral root and they carry stimulus up to the legs, where there is a contraction in the muscles and produce movement of the legs.
- These actions are very fast and in total it is called the reflex action.
Q.11. Draw the structure of the Sympathetic and Parasympathetic Nervous System.
Sol: Structure of the Sympathetic and Parasympathetic Nervous System.
Q.12. What is cerebrospinal fluid?
Sol: It is lymph like fluid secreted by the choroid plexus. This fluid mainly comprises protein, glucose, urea, chloride, sulphate, phosphates, potassium, sodium, calcium, uric acid, etc.
A healthy person has about 150 ml of cerebrospinal fluid, which flows from an anterior to posterior side and travels through the arachnoid cavity and finally enters back into the blood through blood vessels of the dura mater.
Functions of cerebrospinal fluid:
- It provides moisture for the brain and the spinal cord.
- It protects the brain and the spinal cord from the external shocks.
- It provides a medium for the exchange of different nutrients between the brain and the blood cells.
- It also provided a medium for the exchange of gases like oxygen and carbon dioxide between the brain and the blood cells.
- It protects the brain and the spinal cord from harmful pathogens and also helps in diagnosing various diseases related to the brain.
Q.13. Brief out the structure and functions of the spinal cord?
Sol: The spinal cord is a part of the central nervous system. It is a long pipe-like structure arising from the medulla oblongata part of the brain consisting of a collection of nerve fibres, running through the vertebral column of the backbone. It is segmented with a pair of roots (dorsal and ventral roots) consisting of nerve fibres joining to form the spinal nerves. It is usually 40 cm long and 2cm wide. It forms a vital link between the brain and the body.
Structure of the spinal cord
The spinal cord is divided into five different parts.
- Sacral cord
- Lumbar cord
- Thoracic cord
- Cervical cord
Function Of Spinal Cord
It is involved in:
- It facilitates flexible movements.
- It acts as a centre of spinal reflex.
- It helps in all functions of the brain.
- It carries reflexes downward the neck.
- It controls and coordinates all the involuntary activities.
- It carries sensory impulses from skin and muscles to the brain.
- It carries responses from the brain to other parts of the body – hands and legs.
- Forms a connecting link between the brain and the peripheral nervous system.
- It maintains the proper pressure on the brain and the movement of different substances.
- The cerebrospinal fluid present in it, functions by protecting the spinal cord from the external shocks.
Q.14. Describe the structure of the human brain with a neat labelled diagram.
Sol: Structure of the human brain.
The human brain is divided into three main parts.
The forebrain is also called Prosencephalon. It is the largest and the anterior part of the brain. It is an important part of the human brain, which occupies about two-thirds of the total brain.
The forebrain parts include:
The cerebrum is the largest part of the brain. It consists of the cerebral cortex and other subcortical structures. It is composed of two cerebral hemispheres that are joined together by heavy, dense bands of fibre called the corpus callosum.
The cerebrum looks like an oval-shaped structure from the upper side.
Its outer area (cerebral cortex) has a cyton of nerve cells and due to its grey colour, it is called grey matter. The grey matter mainly consists of various types of cells, which make up the bulk of the brain. The inner area is composed of white axon fibres, therefore it is called white matter. The white matter is primarily involved in connecting various grey matter areas of the brain with each other.
The cerebrum is further divided into four lobes or sections:
- Frontal lobe: It is involved with parts of speech, planning, reasoning, problem-solving and movements.
- Parietal lobe: Help in movements, the perception of stimuli and orientation.
- Occipital lobe: It is related to visual processing.
Functions of Cerebrum.
- It initiates the contraction of voluntary muscles and controls them.
- It receives and analyses information from sense organs and interprets touch, hearing and vision.
- It performs mental work, including :
It is the posterior part of the forebrain, which comprises the thalamus, epithalamus, ventral thalamus, hypothalamus and the third ventricle. It is located behind and below the cerebrum and in between the cerebral hemisphere and mesencephalon.
It is extremely sensitive and comprises two main parts:
It is a small structure, located right above the brainstem responsible for relaying sensory information from the sense organs. It is also responsible for transmitting motor information for movement and coordination. Thalamus is found in the limbic system within the cerebrum.
It is a small and essential part of the brain, located precisely below the thalamus. It is considered the primary region of the brain, as it is involved in :
- Receives impulses.
- Regulates body temperature.
- Controls the mood and emotions.
- Controls the sense of taste and smell.
- Synthesises the body’s essential hormones.
The midbrain is also called as Mesencephalon. The midbrain is the smallest region of the brain, found at the centre of the brain, beneath the cerebral cortex, and above the hindbrain. The two main parts of the midbrain are:
Two inferior and two superior optic lobes are found in the midbrain of humans. These are attached by the tectum on the dorsal surface of the midbrain. These are collectively known as Corpora Quadrigemina. This functions by receiving stimuli related to vision and hearing.
These are found in front of the midbrain. These are also known as crura cerebri. It is a bundle made up of fibres, which joins the cerebral cortex with the spinal cord and other parts of the brain.
The hindbrain is also called the Rhombencephalon. The hindbrain is the posterior or the last part of the brain, located at the lower back part of the brain. It is mainly composed of three main parts:
It is the second-largest part of the brain, located in the posterior portion of the medulla and pons. The cerebellum and cerebrum are separated by tentorium cerebelli and transverse fissure.
The outer surface of the cerebellum is called the cortex, it consists of parallel ridges called foila.
Functions of Cerebellum.
The cerebellum is mainly responsible for coordinating and maintaining the body balance during walking, running, riding, swimming, and precision control of the voluntary movements. The main functions of the cerebellum include:
- It senses equilibrium.
- Transfers information.
- Coordinates eye movement.
- It enables precision control of the voluntary body movements.
- Predicts the future position of the body during a particular movement.
- Both anterior and posterior lobes are concerned with the skeletal movements.
- The cerebellum is also essential for making fine adjustments to motor actions.
- Coordinates and maintains body balance and posture during walking, running, riding, swimming.
The pons is the primary structure of the brain stem present between the midbrain and medulla oblongata. It serves as a relay signal between the lower cerebellum, spinal cord, the midbrain, cerebrum and other higher parts of the brain. The main functions of the pons include:
- Controlling sleep cycles.
- Regulating the magnitude and frequency of the respiration.
- Transfers information between the cerebellum and motor cortex.
- Pons is also involved in sensations, such as the sense of taste, hearing and balance.
The medulla oblongata is a small structure present in the lowest region of the brain. It mainly controls the body’s autonomic functions such as heartbeat, breathing, and digestion. It plays a primary role in connecting the spinal cord, pons and the cerebral cortex. Also, it helps us in maintaining our posture and controlling our reflexes.
Q.15. What is Reflex Arc? Draw a labelled diagram of the reflex arc.
Sol: A reflex arc is a pathway that controls a reflex. It can also be defined as the pathway taken by impulse generated at the time of reflex action by neurons.
Structure of Reflex Arc
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