Odisha State Board CHSE Odisha Class 11 Biology Solutions Chapter 21 Neural Control and Coordination Textbook Questions and Answers.
CHSE Odisha 11th Class Biology Chapter 21 Question Answer Neural Control and Coordination
Neural Control and Coordination Class 11 Questions and Answers CHSE Odisha
Very Short Answer Type Questions
Choose the correct option
Question 1.
The myelin sheath around a nerve fibres in the peripheral nervous system is form by
(a) Oligodendrocytes
(b) Microglial cells
(c) Schwann cells
(d) Astrocytes
Answer:
(c) Schwann cells
Question 2.
The somatic sensory neuron conducts nerve impulse
(a) From a somatic receptor to the central nervous system.
(b) From central nervous system to the skeletal muscle.
(c) From the central nervous system to the smooth muscle and or glands.
(d) From a visceral receptor to the central nervous system.
Answer:
(a) From a somatic receptor to the central nervous system.
Question 3.
The cerebrospinal fluid is present
(a) In the subdural space only
(b) In the subarachnoid space only
(d) Both (b) and (c)
(e) Both (a) and (b)
Answer:
(e) Both (a) and (b)
Question 4.
The brain stem consists of
(a) Diencephalon, midbrain and pons
(b) Diencephalon, midbrain and medulla oblongata
(c) Midbrain, cerebellum and medulla oblongata
(d) Midbrain, pons and medulla oblongata
Answer:
(d) Midbrain, pons and medulla oblongata
Question 5.
Emotional states are regulated by
(a) Corpora quadrigemina
(b) Limbic system
(c) Basal nuclei
(d) Corpus callosum
Answer:
(b) Limbic system
Question 6.
Hypothalamus is a part of
(a) Telencephalon
(b) Metencephalon
(c) Diencephalon
(d) Mesencephalon
Answer:
(c) Diencephalon
Question 7.
Memory is regulated by
(a) Hypothalamus
(b) Hippocampus only
(c) Amygdala only
(d) Both (b) and (c)
Answer:
(d) Both (b) and (c)
Question 8.
The superior colliculi of corpora quadrigemina are involved in
(a) Auditory reflexes
(b) Visual reflexes
(c) Beleasing pituitary hormones
(d) Relaying of cutaneous information
Answer:
(b) Visual reflexes
Question 9.
In most people, the right side of the hemisphere controls the movements of
(a) the right side of the body primarily
(b) the left side of the body primarily
(c) both the right and left sides of the body equally
(d) head and neck only
Answer:
(b) the left side of the body primarily
Question 10.
In control of emotion and motivation, the limbic system works together with:
(a) pons
(b) thalamus
(c) hypothalamus
(d) cerebellum
Answer:
(c) hypothalamus
Question 11.
Lateral geniculate nuclei relay
(a) Auditory information
(b) Olfactory information
(c) Visual information
(d) Gustatory information
Answer:
(c) Visual information
Question 12.
Temperature regulation of the body is done by
(a) thalamus
(b) cerebellum
(c) hypothalamus
(d) medulla oblongata
Answer:
(c) hypothalamus
Question 13.
Respiratory and cardiovascular function are controlled by
(a) medulla oblongata
(b) cerebellum
(c) diencephalon
(d) telencephalon
Answer:
(a) medulla oblongata
Question 14.
Autonomic nervous system consists of nerves with:
(a) One neuron with one synapse
(b) Two neuron with two synapse
(c) One neuron with two synapse
(d) Two neuron with one synapse
Answer:
(d) Two neuron with one synapse
Question 15.
Parasympathetic ganglia are located
(a) in a chain parallel to the spinal cord
(b) in the dorsal roots of the spinal nerves
(c) next to or within the organs innervated
(d) in the brain
Answer:
(c) next to or within the organs innervated
Question 16.
The neurotransmitter of preganglionic sympathetic fibres is
(a) Norepinephrine
(b) Epinephrine
(c) Acetylcholine
(d) Dopamine
Answer:
(c) Acetylcholine
Question 17.
Depolarisation is characterised by
(a) Influx of sodium ions
(b) Efflux of potassium ions
(c) Influx of potassium ions
(d) Efflux of sodium ions
Answer:
(a) Influx of sodium ions
Question 18.
Gustation is related to
(a) sense of smell
(b) sense of taste
(c) sense of vision
(d) sense of hearing
Answer:
(b) sense of taste
Question 19.
Balance and equilibrium of the body is maintained by
(a) Semicircular canals only
(b) Saccule only
(c) Utricle only
(d) All of the above
Answer:
(d) All of the above
Question 20.
The retina consists of
(a) unipolar neurons
(b) bipolar neurons
(c) multipolsr neurons
(d) pseudounipolar neurons
Answer:
(b) bipolar neurons
Express the following in one word
Question 1.
The singular long process of a multipolar neuron.
Answer:
Axon
Question 2.
The functional junction between two neurons.
Answer:
Synapses
Question 3.
The nervous system constituted by cranial and spinal nerves.
Answer:
Peripheral nervous system
Question 4.
The cell that forms myelin sheaths around nerve fibres of the peripheral nervous system.
Answer:
Schwann cell
Question 5.
The neuron possessing one each of an axon and a dendron.
Answer:
Bipolar
Question 6.
The nerve fiber that carries neural motor nerves information from the central nervous system to the receptors.
Answer:
Efferent/motor nerves
Question 7.
A collective name for the connective tissue coverings of the brain and spinal cord.
Answer:
Meninges
Question 8.
The fluid that is present in the subarachnoid space, ventricles and central canal.
Answer:
Cerebrospinal fluid
Question 9.
Metencephalon and myelencephalon together constitute a part of the brain.
Answer:
Hindbrain
Question 10.
Midbrain, pons and medulla oblogata together constitute a part of the brain.
Answer:
Mid and hindbrain.
Question 11.
The fiber tract connecting the two cerebral hemispheres.
Answer:
Corpus callosum.
Question 12.
Corpus striatum is a perdominant part of the subcortical nuclei. Name the nuclei.
Answer:
Caudate and lentiform nuclei
Question 13.
The system and hypothalamus that regulate the emotional states of a person. Name the system.
Answer:
Limbic system
Question 14.
The vascular tissue that secretes the cerebrospinal fluid.
Answer:
Anterior choroid plexus and posterior choroid plexus.
Question 15.
The thalamic nuclei that relay visual information to the occipital lobe.
Answer:
Lateral geniculate nucleus
Question 16.
The inferior colliculi are the relay centres of a neural information. Name the neural information.
Answer:
auditory
Question 17.
The regulatory centres of the respiratory system and cardiovascular system lie in a part of the brain. Name it
Answer:
Medulla oblongata
Question 18.
Coordination of movements is executed by a part of the brain. Name it.
Answer:
Cerebellum
Question 19.
The communication between the third and fourth ventricles of the brain.
Answer:
Cerebral aqueduct
Question 20.
A fine connective tissue filament attached to th conus medullaris of the spinal cord.
Answer:
Filum terminale
Question 21.
The chemical substance that is secreted into th synaptic cleft by the presynaptic neuron.
Answer:
Acetylcholine (Neurotransmitters)
Question 22.
The Unconscious motor response to a sensory stimulus.
Answer:
Reflex arc.
Question 23.
The influx of sodium ions changes the polarity of distribution of electrical charges across the membrane of a nerve fiber. Name the process.
Answer:
Depolarisation
Question 24.
The conduction of nerve impulse along a myelinated nerve fiber.
Answer:
Saltatory conductions
Question 25.
Equilibrium or orientation with respect to gravity is controlled by an apparatus.
Answer:
Eustachian tube
Question 26.
The part of the membranous labyrinth connected with hearing.
Answer:
Organ of corti.
Question 27.
The tubular connection between the middle eai and pharynx.
Answer:
Eustachian tube
Question 28.
The part of the retinal that doesn’t contain any photoreceptor cell.
Answer:
Blind spot
Question 29.
The part of the retina, where an image is forme with highest resolution.
Answer:
fovea
Question 30.
Phtoreceptor cells of the retina that perceive colour.
Answer:
Cones
Question 31.
The fluid present in the membranous labyrinth.
Answer:
Perilymph
Question 32.
The fluid present in the bony labyrinth.
Answer:
Endolymph
Correct the sentences, if incorrect, without changing the words underlined
Question 1.
Somatic motor neurons conduct nerve impulse from the sensory receptors to the central nervous system.
Answer:
True
Question 2.
The central nervous system is constituted by the cranial and spinal nerves.
Answer:
The peripheral nervous system is constituted by the cranial and spinal nerves.
Question 3.
The autonomic motor neurons with their control centres constitute the somatic division of the peripheral nervous system.
Answer:
The autonomic motor neurons with their control centres constitute the autonomic nervous system.
Question 4.
The functional junction between a neuron and an effector cell is known as a synapse.
Answer:
True
Question 5.
In human, all synapses electrical.
Answer:
In human, all synapses are chemical.
Question 6.
The sequence of the menings from outer to inner is piameter, arachnoid mater and duramater.
Answer:
The sequence of the menings from outer to inner is duramater, arachnoid and piamater.
Question 7.
Cerebrospinal fluid is secreted by the meninges.
Answer:
Cerebrospinal fluid is secreted by anterior and posterior choroid plexus.
Question 8.
The functional junction between the two cerebral himispheres is known as corpus striatum.
Answer:
The functional junction between the two cerebral himispheres is known as corpus callosum.
Question 9.
Pineal gland arises from a part of the diencephalon, known as hypothalamus.
Answer:
Pineal gland arises from a part of the diencephalon, known as epithalaums.
Question 10.
The mass of cell bodies and axons running through the brain stem is known as corpus callosum.
Answer:
The mass of cell bodies and axons running through the brain stem is known as reticular formation.
Question 11.
Superior colliculi relay auditory information to the occipital lobe of the cerebrum.
Answer:
Superior colliculi relay visual information to the midbrain.
Question 12.
Medulla oblongata coordinates movement and equilibrium.
Answer:
Cerebellum coordinates movement and equilibrium.
Question 13.
Foramen of monro connects the third ventricle with the fourth ventricle.
Answer:
Cerebral aqueduct connects the third ventricle with the fourth ventricle.
Question 14.
In the spinal cord, the outer part is made by white matter, while the inner by gray matter.
Answer:
True
Question 15.
The gray matter consists of medullated nerve fibers.
Answer:
The gray matter consists of neural cell bodies and unmyelinated axons.
Question 16.
The somatic nervous system is constituted by nerves with two types of neurons and a synapse in a ganglion.
Answer:
Autonomic nervous system is constituted by nerves with two types of neurons and a synapse in a ganglion.
Question 17.
Acetylcholine is secreted as the neurotransmitter between pre and postganglionic fibers in both the sympathetic and parasympathetic divisions.
Answer:
True
Question 18.
In somatic motor reflex, the motor transmission is executed by one each of preganglionic and postaganglionic nerous with a synapse in a sympathetic ganglion.
Answer:
In somatic motor reflex, a somatic neuron conducts the impulse along a single axon from the spinal cord to the neuromuscular junction of a skeletal muscle.
Question 19.
Efflux of sodium ions and influx of potassium ions during nerve impulse conduction have been characterised as repolarisation.
Answer:
True
Question 20.
The correct order of the ear ossicles from outer to inner is incus, malleus and stapes.
Answer:
The correct order of the ear ossicles from outer to inner is malleus, incus and stapes.
Question 21.
Stapes is in contact with a round window.
Answer:
Stapes is in contact with a oval window.
Fill in the blanks
Question 1.
The central nervous system is constituted by …………… and …………….. .
Answer:
brain and spinal cord
Question 2.
The structural and function unit of the nervous system is known as ………………… .
Answer:
neuron
Question 3.
The basophilic granular material present in the neuron cytoplsam is known as ………………… .
Answer:
Nissel body
Question 4.
The axons of some neurons are encapsulated by an insulating lipid material, known as ………………… .
Answer:
myelin sheath
Question 5.
The myelin sheaths around the nerve fibers in the central nervous system is formed by ………………… cells.
Answer:
schwann
Question 6.
The efferent motor neurons that conduct impulse from the central nervous system to the visceral effectors are known as ………………… .
Answer:
visceral effector neuron
Question 7.
The functional junction between two neurons is known as ………………… .
Answer:
synapse
Question 8.
The junction between a neuron and effector is known as ………………… .
Answer:
myoneural junction
Question 9.
The impulse transmission across a synapse is carried out by a chemical substance, known as a ………………… .
Answer:
acetylcholine
Question 10.
The middle mening of the brain is known as ………………… .
Answer:
arachnoid
Question 11.
The brain is covered by a delicate connective tissue layer called ………………… .
Answer:
piameter
Question 12.
The dense fibrous connective tissue layer that forms a lining of the cranium is known as ………………… .
Answer:
durameter
Question 13.
The subarachnoid space is filled with a fluid called ………………… .
Answer:
cerebrospinal fluid
Question 14.
The cerebrospinal fluid is secreted by ………………… .
Answer:
choroid plexus
Question 15.
The brain stem is constituted by midbrain, ………………… and medulla oblongata.
Answer:
pons
Question 16.
Two cerebral hemispheres are connected by a fibrous tract, known as ………………… .
Answer:
corpus callosum
Question 17.
The cerebrum surface is marked by the presence of elevations and depressions, known as …………….. and …………….. respectively.
Answer:
gyri and sulci
Question 18.
The mass of cell bodies and axons that run through the brain stem constitutes ………………… .
Answer:
reticular formation
Question 19.
Corpora striata are integral parts of the predominant subcortical nuclei called ………………… nuclei or ganglia.
Answer:
caudate
Question 20.
Lateral geniculate nucleus relays ……………… information to …………….. lobe of the cerebrum.
Answer:
visual and optic
Question 21.
Medial geniculate nucleus relay ………………. information to ……………… lobe of the cerebrum.
Answer:
auditory and temporal
Question 22.
Superior colliculi and inferior colliculi are concerned with …………….. and ……………. functions, respectively.
Answer:
vision and hearing
Question 23.
The degeneration in the caudate nucleus causes a dominant genetic disorder, known as ………………. .
Answer:
Huntington’s diseases
Question 24.
The respiratory centres are situated in …………….. and …………….. of the brain.
Answer:
medulla oblongate and pons
Question 25.
Coordination in speech and movement are controlled by ………………. of the brain.
Answer:
cerebellum
Question 26.
Two lateral ventricles communication with each other and with the third ventricle through ………………. .
Answer:
foramen of monro
Question 27.
The ventricular communication between the third and fourth ventricles is known as ……………… .
Answer:
cerebral aqueduct
Question 28.
There are ……………. pairs of cranial and …………….. pairs of spinal nerves in human.
Answer:
10,31
Question 29.
The bunch of spinal nerves at the posterior end to the spinal cord, resembling a horse tail is known as ………………… .
Answer:
cauda equina
Question 30.
An autonomic nerve consists of ……………. number of neurons and …………….. number of synapses.
Answer:
two and one
Question 31.
The nerve fibers of the afferent (sensory) division convey information from the receptors to the central nervous system. Such fibers are classed as ……………..neurons in respect of the number of processes.
Answer:
pseudounipolar
Question 32.
Two neurons of an autonomic nerve fiber are termed as ……………. and ……………. .
Answer:
preganglionic nerve fibre, postganglionic nerve
Question 33.
The autonomic nervous system consists of two divisions, namely …………….. and ……………. .
Answer:
sympathetic and para sympathetic
Question 34.
The conduction of a nerve impulse along a myelinated nerve fiber is known as ……………… conduction.
Answer:
saltatory
Question 35.
The vestibular apparatus is constituted by the utricle, the saccule and ……………… .
Answer:
semicircular canals
Question 36.
Changes in linear acceleration, i.e. in velocity are regulated by ………….. and ………….. While changes in angular velocity are regulated by ……………. .
Answer:
utricle and saccule; crista ampullaris
Question 37.
The spirally coiled structure attached to the membranous labyrinth, which serves as the organ of hearing is known as ………………… .
Answer:
cochlea
Question 38.
The sensory part of the cochlea is known as ………………… .
Answer:
organ of corti
Question 39.
The innermost layer of the eye ball that contains the sensory cells is known as ………………… .
Answer:
retina
Question 40.
The visual sensory cells are of two types, namely …………… and …………. .
Answer:
rods and cones
Short Answer Type Questions
Question 1.
What is the function of myelin sheath?
Answer:
The myelin sheath is a protective covering that surrounds fibres called axons. The main function of myelin is to protect and insulate these axons and enhance the transmission of electrical impulses.
Question 2.
Why are gray matter and white matter named so?
Answer:
The type of fat in myelin makes it look white, so myelin-dense white matter takes on a white colour as well. In contrast grey matter is mostly neuron cell bodies which provide it grey colour.
Question 3.
Is there any difference between an efferent neuron and motor neuron?
Answer:
There is no difference between efferent and motor neuron, as they both carry nerve impulses from cental nervous system to the effector organs.
Question 4.
What is the role of limbic system?
Answer:
Limbic system include amygadala, hippocampus, thalamus, hypothalamus, basal ganglia and cingulate gyrus.
The limbic system supports a variety of functions including emotion, behaviour, motivation, long-term memory and olfaction.
Question 5.
Which parts of the brain regulate memory?
Answer:
Forebrain regulates memory. It is divided into two regions telencephalon constituted by two cerebral hemispheres (cerebrum) and diencephalon.
Question 6.
What is a chemical synapse?
Answer:
In a chemical synapse, the plasma membranes of pre and post synaptic neurons are separated by a fluid-filled space called synaptic cleft. The terminal part of pre synaptic neuron has endings called terminal boutons. These endings store a chemical substance known as neurotransmitter in synaptic vesicle. These neurotransmitters bring about depolarisation.
Question 7.
Cerebrospinal fluid is being secreted continuously by the choroid plexus. How is this volume kept constant?
Answer:
The volume of cerebrospinal fluid is kept constant, as after its production, it is absorbed and drained into the venous blood by arachnoid villi.
Question 8.
What do you understand by cerebral lateralisation?
Answer:
Cerebral lateralised refer to the fact that the two halves of the human brain are not exactly alike. Each hemisphere has functional specialisation. For example left hemisphere is specialised for language and speech abilities.
Question 9.
How is the day night cycle regulated by melatonin?
Answer:
Melatonin is involved in regulation of day-night cycles. The duration of melatonin secretion each day is directly proportional to the length of night. It is because the melatonin synthesising enzyme is low during daylight and peaks during dark phase.
Question 10.
What is a spinal nerve? Where does it originate from?
Answer:
The spinal nerve tracts are divisible into two, ascending (conducting sensory impulses towards brain) and descending (conducting motor impulses from brain).
Question 11.
Describe a pseudounipolar neuron.
Answer:
Pseudo Unipolar neurons These neurons have cell body with one axon only. These are found usually in the embryonic stage.
Question 12.
What are preganglionic nerve fibers? These are characteristic feature of which section of the nervous system?
Answer:
The fibres extending from CNS to the ganglion are know as preganglionic nerve fibres, whereas those extending from ganglion to the effector organ are called postganglionic fibers. These are characteristic features of autonomic nervous system.
Question 13.
What is sympathetic trunk? Describe about what it is made up of.
Answer:
Sympathetic trunk refers to a paired bundle of nerve fibres that run from the base of the skull to coccyx. The trunk represents 3 ganglia in the cervical part (superior, middle, inferior), 11 ganglia in the thoracic part, 4 lumbar and 4 sacral ganglia.
Question 14.
What is a reflex arc?
Answer:
The entire process of response to a peripheral nervous stimulation, that occurs involuntarily, i.e., without conscious effort or thought, requires the involvement of a part of the central nervous system is called a reflex action. .
The nervous pathway taken by nerve impulses in* a reflex action is called reflex arc.
Question 15.
What is an action potential? How does it help in the conduction of nerve impulse?
Answer:
When a stimulus of adequate strength (threshold stimulus) is applied to a polarised membrane, the permeability of the membrane to Na+ ions is greatly increased at the point of stimulation (site A).
(i) This leads to a rapid influx of Na+ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged. The polarity of the membrane at the site A is thus, reversed and neuron at that point is said to be depolarised.
(ii) The electrical potential difference across the plasma membrane at the site A is called the action potential, (another name of nerve impulse).
Question 16.
What is synaptic transmission?
Answer:
A brief description of the mechanism of synaptic transmission is given below
(i) When an impulse (action potential) arrives at a presynaptic knob, calcium ions from the synaptic cleft enter the cytoplasm of the presynaptic knob.
(ii) The calcium ions cause the movement of the syfiaptic vesicles to the surface of the knob.
The synaptic vesicles are fused with the presynaptic plasma membrane and get ruptured (exocytosis) to discharge their contents (neurotransmitter) into the synaptic cleft.
(iii) The neurotransmitter of the synaptic cleft binds with specific protein receptor molecules, present on the postsynaptic membrane.
(iv) This binding action changes the membrane potential of the postsynaptic membrane, opening channels in the neurolemma and sodium ions to enter the cell. This causes the depolarisation and generation of action potential in the postsynaptic membrane. Thus, the ‘ impulse is transferred to the next neuron.
(v) The new potential developed may be either excitatory or inhibitory.
Question 17.
Are there different regions in the tongue for different tastes? Yes or No. Justify.
Answer:
No,
Tongue is the organ for the sense of taste or gustation. It possess various taste buds located on it. These taste buds are called chemoreceptors or gustatoreceptors. There are three types of papillae present on the tongue.
1. Filiform papillae
2. Fungiform papillae
3. Circumvallate papillae or vallate papillae
In humans, there are approx 10,000 taste buds present on the tongue with each about 60-80 flm in diameter consisting of gustatory cells and supporting cells.
Question 18.
What is vestibular apparatus? How does it help maintain balance and equilibrium with respect to gravity?
Answer:
(i) The inner ear also contains a complex system called vestibular apparatus (located above the cochlea). It is composed of three semicircular canals and the otolith organ consisting of the saccule and utricle.
(ii) Each semicircular canal lies in a different plane at right angles to each other. The membranous canals are suspended in the perilymph of the bony canals. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris, which contains sensory hair cells.
(iii) The saccule and utricle contain a projecting ridge called macula. The crista and macula are the specific receptors of the vestibular apparatus responsible for the maintenance of balance of the body and posture.
Question 19.
What is the role of fovea centralis in the image formation by the eye.
Answer:
The fovea centralis is responsible for sharp central vision, which is necessary in humans for activities where visual – detail is required like reading and driving.
Differentiate between
Question 1.
Axon and Dendron
Answer:
Difference between Dendron and Axons are as follows
| Dendron | Axon |
| These are short fibres which branch repeatedly and project out of the cell body and also contain Nissel’s granules. | The axon is a long branched fibre, which terminates as a bulb-like structure called synaptic knob. It possesses synaptic vesicles containing chemicals called neurotransmitters. |
| These fibres transmit impulses towards the cell body. | The axons transmit nerve impulses away from the cell body to a synapse. |
| Its branches terminate into bulb-like synaptic knobs. | Their branches do not have synaptic knobs. |
Question 2.
Schwann cell and Oligodendrocyte
Answer:
Schwawnn cells and Oligodendrocytes
| Schwawnn cells | Oligodendrocytes |
| Perform a similar function in the Peripheral Nervous System. | Main function is to insulate the axons, almost exclusively in the central nervous system in the higher vertebrates. |
| Can wrap around only one axon. | The multiple layers of warpping of oligodenrocytes around the axons forms the mylein sheath. |
| There are two types myelinating and non-myelinating | The ’feet’ of a single oligodendrocyte can extend its processes to 50 axons, wrapping approximately 1 μm of myelin sheath around each axon. |
Question 3.
Somatic nervous system and Visceral nervous system
Answer:
Somatic nervous system and Visceral nervous system
| Somatic nervous system | Visceral nervous system |
| Somatic neurons are responsible for interactions with the outside world and voluntary movements. This includes touch, feeling pain, ticklish, etc. They are a part of peripheral nervous system. | Visceral neuron are part of the autonomic nervous system. They control involuntary movements of internal organs. An example of this is your heart that beats involuntarily. |
Question 4.
Bipolar and Multipolar neurons
Answer:
Bipolar and Multipolar neurons
| Bipolar Neurons | Multipolar Neurons |
| 1. Bipolar neurons have two processes separated by the cell body. | 1. Multipolar neurons have more than two process; there is a single axon and multiple dendrites. |
| 2. Carry impulses from skin receptors to spinal cord. | 2. It carry impulses from CNS to skeletal muscles. |
Question 5.
Afferent neurons and Efferent neurons
Answer:
| Afferent neurons | Efferent neurons |
| Afferent neurons are responsible for receiving and transmitting messages to the central nervous system from all parts of the body. | Efferent neurons are responsible for receiving and transmitting the message from the central nervous system to all parts of the body. |
| Afferent neurons make up sensory nerves. | Efferent neurons make up motor nerves. |
| Afferent neurons have a single long dendrite and a short axon. | Efferent neurons have a single long axon and several dendrites. |
| Afferent neurons are located just outside the central nervous system. | Efferent neurons are located inside the central nervous system. |
Question 6.
Chemical synapse and Electrical synapse
Answer:
| Chemical Synapse | Electrical Synapse |
| In chemical synapse, signal chemical molecules are neurotransmitters. | In electrical synapse, signal transmission happens in the form of electrical signals without the use of molecules. |
| Signals are modified during the transmission. | Signals are not modified during the transmission. |
| Neurotransmitters are released by exocytosis and diffused in the synaptic cleft and then are bound to receptors. | Electric signals pass via gap junctions. |
| Space between the pre and post synaptic ends is larger. | Space between the pre and post synaptic ends is very small. |
| Signal transmission happens only into one direction. | Signal transmission can happen in both directions. |
| Signal transmission requires energy. So its an active process. | Signal transmission happens without utilizing energy. So, its a passive process. |
| Single transmission happens at a moderate speed. | Signal transmission is extremely fast. |
Question 7.
Corpus callosum and Corpus striatum.
Answer:
| Corpus callosum | Corpus striatum |
| It is an arched mass of white matter in the depths of the longitudinal fissure, made up of transverse fibres connecting the cerebral hemispheres. | It is a subcortical mass of grey matter and white matter in front of and lateral to the thalamus “in each cerebral” hemisphere. |
Question 8.
Medullated and Non-medullated nerve fibers.
Answer:
| Medullated Nerve | Non-medullated Nerve |
| The axon is surrounded by a layer of fatty proteinaceous materials called myelin sheath. | Myelin sheaths are absent. |
| The myelin sheath provides white colour to the nerve fibre. | It appears grey in colour due to absence of myelin sheath. |
| Presence of nodes of Ranvier. | Nodes of Ranvier are absent. |
| The conduction of nerve impulse is faster | The conduction of nerve impulse is slower. |
| They are found in brain and spinal chord. | These are found in sympathetic and para-sympathetic nerves. |
Question 9.
Sympathetic system and Parasympathetic system.
Answer:
| Sympathetic system | Parasympathetic system |
| It consists of axons of neurons arising from the thoracic and lumber region of the spinal cord. Hence, this system is referred to as thoraco-lumber outflow. | It consists of axons of neurons arising from the cranial and sacral region of the spinal cord. Hence, this system is also referred to as cranio-sacral outflow. |
| It consists of short preganglionic and long postganglionic nerve fibres. | It consists of long preganglionic and short postganglionic nerve fibres |
| Its preganglionic fibres emerge with spinal nerves only. | Its preganglionic fibres emerge with cranial as well as spinal nerves. |
| It is very near to the spinal cord. | It is present nearer to the visceral organs. |
| It prepares the body to meet the emergency condition. | It relaxes the activities of body by restoring normal activities after stress. |
| Postganglionic fibres are numerous and are mostly adrenergic. | Postganglionic fibres are fewer and are cholinergic. |
Question 10.
Somatic motor reflex and Autonomic motor reflex.
Answer:
| Autonomic reflex | Somatic reflex |
| An autonomic reflex is one that involves the response of an organ, such as the peristaltic contraction of the smooth muscle of the intestine, that is not controlled consciously. | Somatic reflexes involves a response that involves a skeletal muscle contraction in response to a stimuli. Sensory nerves send signals through an afferent pathway to the central nervous system for processing. |
| The autonomic reflex is associated with one branch of the peripheral nervous system that regulates the sympathetic and parasympathetic nervous system. | A somatic reflex is a part of the other branch of the peripheral nervous system that controls skeletal muscle movements, including knee jerk reflex etc. |
Question 11.
Depolarisation and Repoalarisation.
Answer:
| Depolarisation | Repolarisation |
| It is the state in which the cell membrane change from positive to negative charged outside the cell and from negative to positive charge inside the cell. | It is the state in which the cell membrane change back its resting state, mean from negative to positive charge outside the cell and from positive to negative charge inside the cell. |
Question 12.
Aqueous humor and vitreous humor.
Answer:
| Aqueous humor | Vitreous humor |
| It occurs in aqueous chamber. | It occurs in vitreous chamber. |
| It is a watery fluid. | It is a jelly-like substance. |
| It is secreted by ciliary process. | It is apparently secreted by retina during the development of an eye. |
| It is continuously absorbed into the blood and replaced. | It is neither absorbed nor replaced. |
Question 13.
Endolymph and Perilymph.
Answer:
| Endolymph | Perilymph |
| In scala media. | In scala tympani and scala vestibuli |
| Extracellular fluid. | Ionic composition similar to CSF or plasma |
| Ionic composition similar to intracellular fluid. High K+, low Na+ | Rich in Na+ and low in K+ |
Question 14.
Rod cells and Cone cells.
Answer:
| Rods | Cones |
| The twilight vision is the function of rods. | The daylight vision and the colour vision are functions of cones. |
| The rods contain a purplish-red protein called the rhodopsin or visual purple, which contains a derivative of vitamin-A. | In the human eye, there are three types of cones which possess their own characteristic photopigments that respond to red, green and blue lights. |
Long Answer Type Questions
Question 1.
Describe the structure of human brain and enumerate important function of each part of it.
Answer:
Brain:
The brain is the central information processing organ of our body and acts as the ‘command and control system of all body activities.
Diagram showing sagital section of the human brain
Brain controls the following activities
(i) The voluntary movements and balance of the body.
(ii) Functioning of vital involuntary organs, e.g., lungs, heart, kidneys, etc.
(iii) Thermoregulation, hunger and thirst.
(iv) Circardian (24 hrs) rhythms of our body.
(v) Activities of several endocrine glands and human behaviour.
(vi) It is also the site for processing of vision, hearing, speech, memory, intelligence, emotions and thoughts.
Location:
The brain is the anterior most part of the central neural system, which is located in the cranium (cranial cavity) of the skull.
Protective Coverings of the Brain:
It is covered by three membranes or meninges (cranial meninges)
(i) The outermost membrane, is duramater which is the tough fibrous membrane adhering close to the inner side of the skull.
(ii) The middle membrane, is very thin layer called arachnoid membrane (arachnoid mater).
(iii) The innermost membrane, the piamater is thin and very delicate, which is in contact with the brain tissue.
Knowledge Plus:
The human brain weighs from 1200-1400 g. Brain alone has about 2 billion neurons and trillions of interneuron connections.
Structure:
The human brain is divisible into three main parts
(i) Forebrain
(ii) Midbrain
(iii) Hindbrain
(i) Forebrain
The forebrain consists of
1. Olfactory lobes The anterior part of the brain is formed by a pair of short club-shaped structures, the olfactory lobes. These are concerned with the sense of smell.
2. Cerebrum It is the largest and most complex of all the parts of the human brain. A deep cleft divides the cerebrum longitudinally into two equal halves. These are termed as the left and right cerebral hemispheres. These hemispheres are connected by a large band of myelinated fibres the corpus callosum.
The outer cover of cerebral hemisphere is called cerebral cortex. The cerebral cortex is referred to as the grey matter due to its greyish appearance (as neuron cell bodies are concentrated here).
Lateral view of the brain showing the lobes of cerebral cortex, (a) Lateral view, (b) Drosal view.
The cerebral cortex is greatly folded. The upward folds, gyri, alternate with the downward grooves or sulci. Beneath the grey matter, there are millions of myelinated nerve fibers, which constitute the inner part of the cerebral hemisphere. The large concentration of medullated nerve fibres gives this tissue an opaque white appearance. Hence, it is called the white matter.
Lobes A very deep and a longitudinal fissure, separates the two cerebral hemispheres. Each cerebral hemisphere of the cerebrum is divided into four lobes, i.e., frontal, parietal, temporal and occipital lobes.
In each cerebral hemisphere, there are three types of functional areas
• Sensory areas It receives impulses from the receptors. Motor areas transmit impulses to the effectors.
• Association areas These are large regions that are neither clearly sensory nor motor in junction. They interpret the input, store the input and initiate a response in light of similar past experience. Thus, these areas are responsible for complex functions like memory, learning, • reasoning and other intersensory associations.
3. Diencephalon is the posterio-ventral part of the forebrain.
Its main parts are as follows
• Epithalamus is a thin membrane of non-nervous
tissue. It is the posterior segment of the diencephalon.
• The cerebrum wraps around a structure called thalamus, which is a major coordinating centre for sensory and motor signalling.
The hypothalamus, that lies at the base of thalamus contains a number of centres, which – control body temperature, urge for eating and drinking. It also contains several groups of neurosecretory cells, which secrete hormones called hypothalamic hormones.
The inner parts of cerebral hemispheres and a group of deeply associated structures like amygdala, hippocampus, etc., form a complex structure called limbic lobe or limbic system that is involved in the regulation of sexual behaviour, expression of emotional reactions, e.g., excitement, pleasure, rage and fear and motivation.
(ii) Midbrain
The midbrain is located between the thalamus hypothalamus of the forebrain and pons of the hindbrain. A canal called the cerebral aqueduct passes through the midbrain.
The dorsal portion of the midbrain mainly consists of two pairs (i.e., four) of rounded swellings (lobes) called corpora quadrigemina.
(iii) Hindbrain
The hindbrain consists of
(a) Cerebellum It is also called small brain and consists of three lobes, a central vermis and two lateral cerebellar hemispheres. The central core of each cerebellar hemisphere is formed by white matter and the arrangement of grey matter and white matter in the inner side have a characteristic tree like appearance called Arbor Vitae or tree of life.
(b) Pons Varolii It forms the floor of brain stem and serves as neuronal link between cerebral cortex and cerebellum. It consist of pontine nuclei, pneumotaxic area and apneustic area. Pontine nuclei are sites at which signals for voluntary movements are relayed into cerebellum. Both pneumotaxic and apneustic area control respiration.
(c) Medulla Oblongata It is the triangular part of brain whose roof is associated with overlying piamater to form the posterior choroid plexus. It contains cardiac centres (control rate and force heartbeat), vasomotor centres (control blood pressure by adjusting blood vessel diameter) and two respiratory centres (control rate and depth of breathing).
Ventricles of Brain:
The four cavities within brain are called cerebral ventricles.
These are given below
Cerebral ventricle and their location
Ventricle I, II and III are connected by foramen of monro, while ventricle III and IV are connected by cerebral aqueduct. Roof of ventricle IV contains a pair of lateral apertures foramina of luschka and a median aperture foramen of magendie.
The entire venticular system is lined the ependymal cells.
(a) Longitudinal frontal section of the brain and (b) Longitudinal sagittal section showing ventricles
Question 2.
Give an account of the mechanism of generation and propagation of a nerve impulse.
Or
Describe the mechanism of conduction of nerve impulse.
Answer:
Nerve impulse is a wave of bioelectric/electrochemical disturbance that passes along a neuron during conduction of an excitation.
Impulse conduction depends upon
(i) Permeability of axon membrane (axolemma).
(ii) Osmotic equilibrium (electrical equivalence) between the axoplasm and Extracellular Fluid (ECF) present outside the axon.
The generation of a nerve impulse is the temporary reversal of the resting potential in the neuron.
It occurs in following three steps
Resting Membrane Potential or Polarisation:
In a resting nerve fibre (a nerve fibre that is not conducting an impulse), the axoplasm (neuroplasm of axon) inside the axon contains high concentration of K and negatively charged proteins and low concentration of Na+.
(i) In contrast, the fluid outside axon contains a low concentration of K+ and a high concentration of Na+ and thus, forms a concentration gradient.
(ii) These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump, which transports 3Na+ outwards and 2K+ inwards (into the cell).
(iii) As a result, the outer surface of the axonal membrane possesses a positive charge, while its inner surface becomes negatively charged and therefore, is polarised.
(iv) The electrical potential difference across the resting plasma membrane is called as the resting potential. The state of the resting membrane is called polarised state.
Action Potential or Depolarisation:
When a stimulus of adequate strength (threshold stimulus) is applied to a polarised membrane, the permeability of the membrane to Na+ ions is greatly increased at the point of stimulation (site A).
1. This leads to a rapid influx of Na+ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged. The polarity of the membrane at the site A is thus, reversed and neuron at that point is said to be depolarised.
2. The electrical potential difference across the plasma membrane at the site A is called the action potential, (another name of nerve impulse).
3. At adjacent sites, e.g., site B, the membrane (axon) has positive charge (still polarised) on the outer surface and a negative charge on its inner surface.
4. The stimulated negatively charged point on the outside of the membrane sends out an electrical current to the positive point next to it. As a result, a current flows on the outer surface from site B to site A, while on the inner surface current flows from site A to site B.
This process (reversal) repeats itself over and over again and a nerve impulse is conducted throughout the length of the neuron.
Diagrammatic representation of impulse conduction through an axon
Repolarisation:
(i) The rise in the stimulus-induced permeability to, Na+ is extremely short lived. It is quickly followed by a rise in membrane permeability to K+.
(ii) Within a fraction of a second, Na+ influx stops andK+ outflow begins until the original resting state of ionic concentration is achieved. Thus, resting potential is restored at the site of excitation, which is called repolarisation of the membrane. This makes the fibre once more responsive to further stimulation.
(iii) In fact, until repolarisation occurs, neuron cannot conduct another impulse. The time taken for this restoration is called refractory period.
Reorientation:
Following repolarisation the membrane potential is restored at resting potential state, i.e. at 70 mV and the orientation of ions is also brought to normal. This is achieved by a process called reorientation. At the end of reorientation, normal polarity in respect of ionic distribution is reached.
Types of conduction:
Mechanism of conduction are different in myelinated and non-myelinated fiber. These are as follows
(a) Conduction along myelinated fiber
When an impulse travels along a myelinated neuron, depolarisation occurs only at the nodes of Ranvier. It leaps over the myelin sheath from one node to the next. This process, is called saltatory conduction.
This process accounts for the greater speed of an impulse travelling along a myelinated neuron than along a non-myelinated one. It is upto 50 times faster than the non-myelinated nerve fibre.
(b) Conduction along unmyelinated fiber
An action potential is generated is the membrane at the site of stimulation. The membrane undergoes depolarization by a rapid inflax of Na+ and then repolarization by an efflux of k+. Like this there is a wave of depolarization and repolarization in a forward direction in an electrifying speed.