Important Questions Class 11 Biology Chapter 21

Class 11 Biology Chapter 21 Important Questions – Neural Control and Coordination

Class 11 Biology Chapter 21 is about Neural Control and Coordination. This is a vast chapter and one of the most important topics of human physiology. In this chapter students will learn about the entire neural system of human beings and other animals and how this system coordinates with other parts of the body. 

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The Important Questions Class 11 Biology Chapter 21 covers all the vital points for students to get clear-cut insights over all the topics and sub-topics listed in the chapter. Solving questions would help students improve their performance, boost their confidence and score well in examinations.

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Class 11 Biology Chapter 21 Neural Control and Coordination Important Questions with Solutions

Biology chapters have to be studied well and understood fully. Frequent reading and practice of the Important Questions Class 11 Biology Chapter 21 will help students with that. The questions are carefully collated from various sources and cover the chapter fully. Each question comes with a detailed step-by-step solution that helps students to understand the concepts used in the question.

Below are a few questions and their answers from our question bank of Class 11 Biology Chapter 21 Important Questions.

Question 1. Write a note on neural coordination.

Answer 1: The neural system provides neural coordination to coordinate the organised network of point-to-point connections quickly. The mechanism involving neural coordination is given below:

• Nerve impulse transmission.
• Impulse coordination across a synapse.
• Reflex action physiology.

Question 2. Draw a well-labelled diagram of the neuron.

Answer 2:

Question 3. Explain the role of sodium in the generation of the action potential.

Answer 3: The nerve membrane becomes freely permeable to sodium ions on stimulation.

Following stimulation, there is a rapid influx of sodium ions followed by polarity reversal. This means that the membrane’s outer surface becomes negatively charged, and the inner side becomes positively charged.

The difference in electrical potential across the membrane is known as the action potential. This is also called the nerve impulse. The sodium ions play an important role in generating the action potential.

Question 4. Difference between the dendrites and the axon.

Answer 4: 

Question 5. Difference between myelinated and non-myelinated axons.

Answer 5:

Question 6. What is the significance of saltatory conduction?

Answer 6: In myelinated nerve fibre, action potential jumps from one node to the other node of Ranvier. There is a greater speed of nerve impulse conduction across a myelinated nerve fibre. The speed is 50 times faster than the non-myelinated nerve fibre. This is the significance of saltatory conduction.

Question 7. What is the difference between resting and action potential?

Answer 7: 

Question 8. During resting potential, the axonal membrane is polarised. Explain the movement of positive and negative ions leading to polarisation.

Answer 8: When a nerve is not conducting an impulse, the axoplasm contains a high concentration of potassium ions and a low concentration of sodium ions.

The fluid outside the axon has a low concentration of potassium ions and a higher concentration of sodium ions. In this way, a concentration gradient is established.

The potential difference is maintained with the help of the Na+-K+ pump. The ionic gradients across the resting membrane are supported by the sodium-potassium pump, which transports three sodium ions outwards and two potassium ions inwards to the cell.

The membrane is said to be polarised when the outer surface is a positive charge, and the inner is negatively charged.

The electrical potential difference across the resting membrane is called resting potential, and the state of the resting membrane is called polarised.

Question 9. What do grey and white matter in the brain represent?

Answer 9: Grey matter forms the outer layer of the brain and an inner layer of the spinal cord. It is grey and made up of non-myelinated nerve fibres—the nerve impulse transmission is slow.

White matter forms the brain’s inner part and the spinal cord’s outer part. It is white and made up of myelinated nerve fibres. The nerve impulse transmission is very fast. 

Question 10. Nervous systems and computers share certain common features. Comment in 5 lines.

Answer 10: The nervous system and computers have many common features. This is because the sensory neurons in various organs sense the environment and extend the message to the brain.

The brain acts as the Central Processing Unit (CPU). The information is gathered by the sensory neurons, which are processed by the brain. The brain commands the concerned organs to function accordingly. The message is taken and conveyed by the motor neurons, and the output devices take and get the message.

Question 11. What would affect the person’s CNS if someone received a blow on the back of the neck?

Answer 11: Cervical injuries result in quadriplegia or tetraplegia. When someone gets a blow on the back of the neck, there is an impairment in physical functioning and cognitive abilities. This injury also results in behavioural disturbances and emotional dysfunction.

Question 12. Compare cranial nerves and spinal nerves.

Answer 12:

Question 13. Differentiate between the thalamus and the hypothalamus.

Answer 13:

Question 14. Multiple choice questions:

• Chemicals which are released at the synaptic junction are called

• Hormones

• Neurotransmitters

• Cerebrospinal fluid

• Lymph

Answer 1: (b) Neurotransmitters

Explanation:

The neurotransmitters are released at the synaptic junction, and transmit impulses from one neuron to the next.

• Resting membrane potential is maintained by

• Hormones

• Neurotransmitters

• Ion pump

• None of the above

Answer: ( c) ion pump

Explanation:

The sodium-potassium pump is responsible for transporting sodium and potassium ions.

• The function of our visceral organs is controlled by

• Sympathetic and somatic neural system

• Sympathetic and parasympathetic neural system

• Central and somatic nervous system

• None of the above

Answer: (b) sympathetic and parasympathetic neural system.

Explanation:

There is impulse transmission to the involuntary organs from the central nervous system.

• Which of the following will not be involved in the knee-jerk reflex?

• Muscle spindle

• Motor neuron

• Brain

• Interneurons 

Answer: (c)

Explanation:

The Brain is not involved in the reflection action like the knee jerk reflex.

• An area in the brain which is associated with strong emotion is

• the Cerebral cortex

• Cerebellum

• Limbic system

• the Medulla

Answer  c) the limbic system

Explanation:

The Limbic system is responsible for excitement, fear and pleasure.

• Mark the vitamin present in Rhodopsin

• Vit A

• Vit B

• Vit C

• Vit D

Answer  (a) vitamin A

Explanation:

Rhodopsin is the visual pigment, and it is a derivative of vitamin A.

Question 15. Write a note on Brain

Answer 15: The brain controls all the activities of our body. It has the following functions:

• Responsible for functioning all vital organs of the body like lungs, heart and kidneys.
• Thermoregulation
• Regulates thirst and hunger.
• Regulation of various endocrine glands.
• Process vision, hearing, speech, memory, thoughts, emotions and intelligence.

The brain is located in the cranium. It has three membranes: Dura mater, Arachnoid and Pia mater. The brain is divided into the forebrain, midbrain and hindbrain.

The forebrain consists of the cerebrum, olfactory lobes and diencephalon.

The cerebrum has two cerebral hemispheres, and each hemisphere is differentiated into four lobes. They are the frontal, parietal, temporal and occipital. Gyri and sulci are present to increase the surface area for accommodating more neurons. The functions of the cerebrum are as follows:

• The frontal lobe has a prefrontal area, premotor area and motor area. Broca’s area is the motor centre for speech. This area initiates the movement of lips, tongue and larynx to produce speech.
• The parietal lobe has somatosensory areas. Brodmann’s area regulates speech. This area also precepts touch, pain, temperature, pressure and taste.
• The temporal lobe has an olfactory area and an auditory area. So it is responsible for smell and hearing.
• Wernicke’s area is for understanding speech.
• The occipital lobe is for vision.

The postero-lateral part of the forebrain is known as Diencephalon. Its main parts are:

• Epithalamus
• Thalamus
• Base of the thalamus is the hypothalamus.

The midbrain has four lobes. The two anterior lobes are called Superior Colliculi, responsible for visual reflexes. The posterior lobes are called Inferior Colliculi and are responsible for the auditory reflex.

The hindbrain has cerebellum, pons and medulla oblongata.

• Cerebellum has three areas, namely superior, median and inferior peduncle. It coordinates the locomotion and balance of the body.
• Pons Varolii is present in mammals only, and it controls breathing.
• Medulla oblongata controls involuntary activities, namely, breathing, heartbeat, peristalsis and vasomotor activity. It also controls coughing, sneezing, vomiting and hiccupping.

Question 16. Answer the following questions:

• Which part of the ear determines the pitch of the sound?

• Which is the most developed part of the brain?

• Which part of the central nervous system is called the master clock?

Answer:

1. Cochlea determines the pitch of the sound.
2. The largest and most developed part of the brain is the forebrain.
3. Hypothalamus is the master clock of the body.

Question 17. Write short notes on

• Neuronal coordination

• Retina

• Ear ossicles

• Synapse

• Organs of Corti

• Cochlea

Answer 17.

1. Neuronal coordination means a process by which various organs of the body interact with each other and complement each other function. In humans, two systems are developed for control, coordination and integration. They are the nervous system and the endocrine system. The nervous system is an organised network of neurons which carry out neuronal coordination.
2. Retina is the sensory coating of the eye. It has four layers: 

• Pigmented epithelium which absorbs oblique light rays.
• Sensory layer has two types of cells: rods and cones.
• Bipolar neuron layer contains amacrine and horizontal cells to sharpen the contrast.
• Ganglionic layer with Optic nerve fibres.

In dim light, the rods are sensitive to vision and contain a pigment called Rhodopsin. The vision is called Scotopic vision. 

The cones are sensitive to bright light and contain photopsin pigment. The vision is called Photopic vision. The point from where the optic nerve arises is called the blind spot.                     

(c) Ear ossicles:

The tympanic cavity contains three ear ossicles which are small bones. The sequence of these bones from the tympanum to the oval window is given below

• Malleus which is hammer-shaped.
• Anvil-shaped incus.
• Stirrup-shaped stapes.

Malleus, Incus and Stapes are the three ear ossicles that conduct sound vibrations and amplify. Stapes are the smallest human body bone and fit into the oval window.

A hinge joint is present between the malleus and incus. The ball and socket type of joint is between the incus and stapes.

(d) Synapse: 

The junction between the two neurons is called the synapse. They are of two types:

• Electrical
• Chemical

In an electrical synapse, the synaptic cleft is 0.2 nm and has conduction similar to the axon.

In a chemical synapse, the synaptic cleft is 20 nm, and a neurotransmitter like acetylcholine is required for transmission. The synaptic knobs contain synaptic vesicles filled with a neurotransmitter. There is the presence of Ligand-gated channels. The postsynaptic membrane has receptors where the acetylcholine binds to open channels. When the impulse reaches the terminal button of the axon, calcium influx occurs via the opening of calcium gates. This activates synaptic vesicles, which get ruptured after coming in contact with the presynaptic membrane. By the process of exocytosis, acetylcholine is released into the synaptic cleft. This released neurotransmitter binds with the receptor of the postsynaptic membrane, and sodium gates open. There is sodium influx which generates depolarisation or the impulse wave.

(e) Organs of Corti:

The organ of Corti forms the sensory part of the hearing. The hair cells are attached to the basilar membrane. These cells are supported by the Dieter cells. The group of the hair cell is covered by a tectorial membrane which embeds the processes of hair cells. This membrane helps hair cells of organs on Corti to generate impulses. The organ of Corti is present in a frog’s ear.

(f) Cochlea:

It is the coiled structure for hearing. It has 2 34 coils in humans. It has three canals in cross-section:

• Vestibular canal or Scala Vestibule.
• Cochlear canal or Scala Media
• Tympanic canal or Scala Tympani.

The vestibular canal and tympanic canal are filled with perilymph. The Cochlear canal is filled with Endolymph

Question 18. Fill in the blanks:

• Krause end bulbs are sensory for ________

• __________nourishes the lens and cornea.

• _______ contains only cones.

• ___________is present in semicircular canals.

• Tapedum lucidum is present behind retina and contains ________

• ___________ is the thinnest branch of spinal nerve.

• Hypothalamus part of Diencephalon regulates _________

• Stapes is homologous to _________

• ____________ produce oily secretion for lubrication.

• Spinal nerves are _______ in number and are _______

• __________is the last cranial nerve

• Thalamus is the part of _________
• The nervous part of the spinal cord is called ____________

Answer 18:

1. Krause end bulbs are sensory for cold
2. Aqueous humour nourishes the lens and cornea.
3. Yellow spot contains only cones.
4. Cupula is present in semicircular canals.
5. Tapedum lucidum is present behind the retina and contains guanin crystals.
6. Ramus Communicans is the thinnest branch of the spinal nerve.
7. Hypothalamus part of the Diencephalon regulates osmotic concentration.
8. Stapes is homologous to Columella auris.
9. Meibomian glands produce oily secretion for lubrication.
10. Spinal nerves are 31 in number and are mixed.
11. Hypoglossal is the last cranial nerve
12. Thalamus is the part of the forebrain.
13. The nervous part of the spinal cord is called cauda equina

Question 19. What are the receptors present on the skin?

Answer 19: The receptors are:

• Meissner’s corpuscles for touch.
• Krause’s End bulbs for cold
• Ruffini end bulb for hot
• Paccinian’s corpuscles for pressure
• Free nerve endings for pain.

Question 20. Mention some sensory organs.

Answer 20: The sensory organs are:

• Lateral line organ
• Jacobson organ
• Johnston’s organ
• Loreal pit
• Ampullae of Lorenzini.

Question 21. Draw the diagram of olfactory epithelium

Answer 21:

Question 22. What do you mean by Schneiderian membrane?

Answer 22: The olfactory lining is called the Schneiderian membrane and it is sensory for the smell.

It has three types of cells:

• Receptor cells
• Supporting cells
• Glandular cells of Bowman’s gland

The strength of the smell depends on the number of receptors stimulated.

Question 23. Enumerate eye disorders.

Answer 23: The eye disorder is:

• Night blindness
• Myopia
• hypermetropia
• Colour blindness
• Conjunctivitis
• Strabismus 
• Cataract
• Glaucoma
• Presbiopia
• Astigmatism 

Question 24. What is glaucoma?

Answer 24: In glaucoma, the aqueous humour pressure rises which causes damage to the retina and may even lead to blindness.

Question 25. Explain briefly:

• Parkinson’s disease

• Multiple sclerosis

• Huntington’s Chorea

Answer 25:

1. Parkinson’s disease is due to the deficiency of the neurotransmitter Dopamine. This is also called Shaking Palsy as it produces muscle tremors. There is a lack of control and coordination of movements. Other features include an expressionless face, stooping posture and physical disability.
2. In multiple sclerosis, there is demyelination of white matter in the brain and spinal cord. This can be autoimmune or genetic. The features include abnormal sensation, muscle weakness and lack of coordination.
3. Huntington’s chorea is a genetic disorder with the age of onset after 30 years. There is the development of neurotransmitter deficiency GABA which causes involuntary, rapid and uncoordinated movements. There is progressive dementia followed by death.

Question 26. Explain the types of reflexes

Answer 26: The two types of reflexes are simple or unconditioned and conditioned reflexes.

Simple reflexes are controlled by the spinal cord and not by the brain. An example would be an  increase in a heartbeat after hearing a louder sound. Other examples include sneezing, coughing, vomiting and swallowing.

Conditioned reflexes involve the brain, and this is through the cerebrum. An example includes swimming, dancing, driving, cycling, etc.

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