Answer

(b) Neurotransmitters are involved in the transmission of impulses at the chemical synapses. They are present in the synaptic vesicles at axon terminals.

Whereas, hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.

Cerebrospinal fluid is present in subarachnoid space. It provides shock resistance to brain

Lymph is a colourless fluid containing specialised lymphocytes which are responsible for the immune responses of the body. It is important carrier for nutrients, hormones, etc. Fats are absorbed through lacteals (lymph vessels) present in microvilli of intestine.

Thinking Process

Neurons are called excitable cells because their membranes are in a polarised state, Different types of ion channels are present on the neural membrane. These ion channels are selectively permeable to different ions.

Answer

(a) The ion gated channels on the neurolemma control the movement of $\mathrm{Na}^{+}$and $\mathrm{K}^{+}$ions on both inner and outer side of nerve cell.

$\mathrm{Ca}^{2+}, \mathrm{CO}_{3}^{2-}, \mathrm{Mg}^{2+}$ and $\mathrm{Ca}^{4+}$ ions are not related with nerve excitation rather are involved in other biological functions. $\mathrm{Ca}^{+2}$ ions are related to muscle metabolism where $\mathrm{Mg}^{2+}$ ions act as a cofactor in some reactions.

$\mathrm{Cl}^{-}$ion channels are important for setting cell resting membrane potential, transepithelial salt transport, and the acidification of internal and extracellular compartments.

Thinking Process

The electrical potential difference across the resting plasma membrane is called as the resting potential.

Answer

(c) The ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pumps (or ion pumps) which transport 3 $\mathrm{Na}^{+}$outward for every $2 \mathrm{~K}^{+}$into the cell.

Answer

(b) Sympathetic and parasympathetic neural system control all the visceral organs of the body. Whereas, somatic neural system is a part of peripheral nervous system and is not related to regulation of visceral org

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Answer

Similarly CNS is not concerned with it.

5. Which of the following is not involved in knee-jerk reflex?

(a) Muscle spindle

(b) Motor neuron

(c) Brain

(d) Inter neurons

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Thinking Process

Reflex action is a form of animal behaviour in which the stimulation of a sensory organ results in the activity of some organs without the intervention of will.

Answer

(c) Brain is not involved in any reflex action (e.g., knee-jerk reflex) while the muscle spindle, inter neuron and motor neuron are the part of reflex arch.

6. An area in the brain which is associated with strong emotions is

(a) cerebral cortex

(b) cerebellum

(c) limbic system

(d) medulla

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Answer

(c) The limbic lobe or limbic system, along with the hypothalamus, is involved in the regulation of emotions (e.g., excitement, pleasure rage and fear) and motivation.

7. Mark the vitamin present in rhodopsin

(a) vit-A

(b) vit-B

(c) vit-C

(d) vit-D

8. Human eyeball consists of three layers and it encloses

(a) lens, iris, optic nerve

(b) lens, aqueous humor and vitreous humor

(c) cornea, lens, iris

(d) cornea, lens, optic nerve

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Answer

(b) Human eye ball consist of three, i.e., layers sclera, choroid and retina and these layer enclose lens, aqueous humor and vitreous humor.

9. Wax gland present in the ear canal is called

(a) sweat gland

(b) prostate gland

(c) Cowper’s gland

(d) sebaceous gland/ceruminous gland

10. The part of internal ear responsible for hearing is

(a) cochlea

(b) semicircular canal

(c) utriculus

(d) sacculus

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Answer

(a) Cochlea is the part of internal ear responsible for hearing. It is connected with saccule and is a spirally coiled structure that resembles a snail shell in appearance.

Semicircular canal are membranous canal suspended in the perilymph of the bony canals and are the structures of equilibrium (balancing). Whereas, utriculus and sacculus are the parts of the balancing apparatus located within the vestibule of the bony labyrinth.

These have small stones and a viscous fluid to stimulate hair cells to detect motion and orientation.

11. The organ of corti is a structure present in

(a) external ear

(b) middle ear

(c) semi circular canal

(d) cochlea

Very Short Answer Type Questions

1. Rearrange the following in the correct order of involvement in electrical impulse movement.

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Thinking Process

Neurons are exitable cells because their membranes are in a polarised state.

Answer

The correct order of involvement in electrical impulse movement.

(i) Dendrites

(ii) Cell body

(iii) Axon

(iv) Axon terminal

(v) Synaptic knob

2. Comment upon the role of ear in maintaining the balance of the body and posture.

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Answer

The vestibular system is the sensory apparatus of the inner ear that helps the body maintain its postural equilibrium.

There are two sets of organs in inner ear, or labyrinth—The semicircular canals which respond to rotational movements; and the utricle and saccule within the vestibule, which respond to changes in the position of the head with respect to gravity.

Each semicircular canal contains hair cells. Rotation of the head causes a flow of fluid, which in turn causes displacement of the top portion of hair cells embedded in jelly-like capula. Utricle and saccule called otolithic organs contain hair cells blanketed with ting stones called otoconia.

When the head is tilted or body position is changed the displacement of stones causes the hair cells to bend.

3. Which cells of the retina enable us to see coloured objects around us?

4. Arrange the following in the order of reception and transmission of sound wave from the ear drum.Cochlear nerve, external auditory canal, ear drum, stapes, incus, malleus, cochlea.

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Answer

External Auditory canal $\rightarrow$ Eardrum $\rightarrow \quad$ Malleus $\rightarrow$ The reception and transmis sion of sound wares occurs in following order-

Incus $\rightarrow$ Stapes $\rightarrow$ Cochlea $\rightarrow$ Cochlear nerve

5. During resting potential, the axonal membrane is polarised, indicate the movement of $+v e$ and $\rightarrow$ ve ions leading to polarisation diagrammatically.

Ans.

Answer

The following structures are involved in the protection of brain in animals

(i) Cranium There are 8 cranial bones which form the hard protective outer covering cranium for the brain.

(ii) Meninges The brain is covered with three membranes called meninges.

(a) Piamater Inner most membrane very thin, delicate and vascular and invests the brain closely.

(b) Arachnoid membrane It is like spider we in structure from which its gets its name.

(c) Duramater It is outer most, thick, tough fibrous membrane adhering closely to the inside of the skull.

(iii) Cerebrospinal fluid The cerebrospinal is present in the spaces between the meninges, i.e., arachnoid and duramater, which functions as a pad, absorbing shocks.

Answer

The inner part of cerebral hemispheres and a group of associated deep structures called limbic lobe or limbic system along with hypothalamus are involved in the above said functions, i.e., aggressive behaviour, use or abusive words, restlessness, etc.

Answer

Grey matter is a major component of CNS consisting of neuronal cell bodies, dendrite, unmyelinatedaxous, glial cells and capillaries.

White matter is also a component of CNS and consists mostly of glial cell and myelinated axons.

Answer

Hypothalamus contains many centres which control urge for eating and drinking.

Answer

The symptoms of dizziness and vomiting, faced by a person travelling at higher altitude is because of the following resaons

(i) The function of Eustachian tube is to equalise the pressure on either sides of the ear drum; sudden elevation in height causes disturbance in maintaining pressure by this area of ear.

(ii) The semicircular ducts, the anterior, posterior and lateral semicircular ducts, are enlarged at one end to give rise to ampulla. Each ampulla contains sensory path of hairs, the cristae, which is concerned with the balancing of the body, Change in altitude brings changes in the reorientation and adjustments in these structures of internal ear causing the above said symptoms.

Answer

A. $\rightarrow$ (3) B. $\rightarrow$ (4) C. $\rightarrow(2)$ D. $\rightarrow(1)$

Answer

The major parts of the human neural system is filled in the boxes with appropriate words

Answer

Differences between electrical transmission and chemical transmission are as given below

| Electrical Transmission | Chemical Transmission | | :— | :— | | It occurs at electric synapse. | It occurs at chemical synapse. | | Synaptic cleft may or may not be present. | Synaptic cleft is present. | | At electrical synapses, electrical current can flow directly from one neuron into the other across these synapses. | At chemical synapse, neurotransmitter from pre-synaptic neurons transfer to post-synaptic neurons leading to transmission of impulse. | | Impulse transmission across an electrical transmission is always faster. | Chemical transmission is slower. |

Answer

The sensory neurons present in various organs sense the environment and extend the message to the brain. So, it is equivalent to input device of computers.

Brain acts as CPU, i.e., Central Processing Unit. The information gathered by sensory neurons is processed by brain and it gives command to the concerned organ to act accordingly. This message is taken or conveyed by motor neurons which act as output devices.

Thinking Process

The central nervous system, that includes brain and spinal cord, is are the actual command centre for entire body and any damage, or abnormality in these can lead to non-functioning of body parts and organs.

Answer

If a person receives a blow on the back, then it will lead in an impairment of cognitive abilities or physical functioning. It can also result in the disturbance of behavioural or emotional functioning. Cervical injuries often lead to quadriplegia (tetraplegia).

Answer

The eustachian tube connects the middle ear cavity with the pharynx. It helps in equalising the pressures on either sides of the ear drum. At the pharyngeal opening of the Eustachian tube, is a valve which normally remains closed.

The valve opens during yawning, swallowing and during an abrupt change in altitude, when air enters or leaves the tympanic cavity to equalise the pressure of air on the two sides of the tympanic membrane.

Answer

Representation of the following parts of eye

Answer

A neuron has three main parts

(i) Cell body

(ii) Axon

(iii) Dendrites

Any stimulus/nerve impulse passes from one neuron to another via axon. This nerve impulse is wave of bioelectric/electrochemical disturbance that passes along neuron during conduction of an excitation.

Transport and release of a neurotransmitter occurs within a synapse. At a chemical synapse, the membranes of the pre- and post-synaptic neurons are separated by a fluid-filled space called synaptic cleft. Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses. The axon terminals contain vesicles filled with these neurotransmitters.

When an impulse (action potential) arrives at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane, where they fuse with the plasma membrane and release their neurotransmitters in the synaptic cleft.

The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new action potential in the post-synaptic neuron.

Thinking Process

The brain is the central information processing organ of our body and act as the ‘command and control system’.

Answer

The forebrain is the largest part of the brain most of which is cerebrum. Other important structures include the thalamus, hypothalamus and the limbic system.

The cerebrum is divided into two cerebral hemisphere connected here by a mass of white matter known is corpus callosum. Each hemispere is split into four lobes. The surface of each hemisphere is made up of grey matter known as the cerebral cortex that is folded to increase the surface area. Various structures of forebrain are given below

| Brain Region | Structure | Function | | :— | :— | :— | | Diencephalon | Thalamus | Organising sensory information | | Diencephalon | Hypothalamus | Endocrine system,
thermoregulation | | Diencephalon | Pituitary | Endocrine system | | Telencephalon | Cerebral cortex | Consciousness, language, etc | | Telencephalon | Limbic system | Memory, motivation, emotions | | Telencephalon | Olfactory bulb /lobes | Smell |

Thalamus

The thalamus has many functions including processing and relaying sensory information selectively to various parts of the cerebral cortex, translating signals to the cerebral cortex and also regulating states of sleep and wakefulness. The thalamus plays a major role in regulating arousal levels of consciousness and levels of activity.

Hypothalamus

The function of the hypothalamus is mainly related to the overall regulation of the endocrine system and closely related to the pituitary gland.

Pituitary

The function of the pituitary is mainly related to the production of hormones as part of the endocrine system.

Cerebral Cortex

The cerebral cortex is essential for memory, attention, awareness, thought, language and consciousness. The cerebral cortex is connected to structures such as the thalamus and the basal ganglia, sending information to them along efferent connections and receiving information form them via afferent connections.

Motor Cortex

The motor cortex areas of the brain are located in both hemispheres of the cortex are related to controlling voluntary movements, especially fine movements.

Sensory Areas

The sensory areas are the areas theat receive and process information from the senses. inputs form the thalamus are called primary sensory areas, where vision, hearing and touch are processed. The two hemispheres of the cerebral cortex receive information form the opposite (contra lateral) side of the body.

The association areas of the brain function to produce a perception of the world enabling an animal to interact with their environment effectively. The frontal lobe or prefrontal association complex is involved in planning actions and movement.

Limbic System

The limbic system is principally responsible for emotions and the various types of emotion can affect the activity of the Autonomic Nervous System (ANS) facilitated by the hypothalamus.

Olfactory Bulb

The olfactory bulb is responsible for olfaction concerned with sense of small plays.

Answer

Ears are a pair of statoacoustic organ meant for both balancing and hearing. In most mammals, the external ear is a leap of tissue also called pinna. It is a part of auditory system. The human ear consists of three main parts external ear, middle, ear and internal ear.

Structure of Middle Ear

The middle ear contains three bones or ossicles-the malleus (hammer), incus (anvil) and stapes (stirr-up). These bones are attached to one another in a chain-like fashion. The malleus is attached to the tympanic membrane and the stapes is attached to the oval window (a membrane beneath the stapes) of cochlea. These three ossicles increase the efficiency of transmission of sound waves to the inner ear.

The middle ear also opens into the Eustachian tube, which connects with the pharynx and maintains the pressure between the middle ear and the outside atmosphere,

Structure of Internal Ear

The inner ear consists of a labyrinth of fluid-filled chambers within temporal bone of the skull. The labyrinth consists of two parts, i.e., the bony and membranous labyrinth. The bony labyrinth is a series of channels.

Inside these channels, membranous labyrinth lies, which is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called cochlea.

The cochlea has two large canals-an upper vestibular canal (scala vestibuli) and a lower tympanic canal (scala typmani)-separated by a small cochlear duct (scala media). The vestibular and tympanic canals contain perilymph and the cochlear duct is filled with endolymph.

At the base of scale vestibuli, the wall of membranous labyrinth comes in contact with the fenestra ovalis, while at the lower end of scala tympani lies the fenestra rotunda.