10th Class Chapter 3 Biology Long Questions

Nerve:

A nerve mean the union of several axon that are enveloped by a covering made of lipid bared on the property of axon the nerve.

Classified into three types:

Sensory Nerves:

Contains the axon of sensory neurons only

Motor nerves:

Contain the axon of motor neurons only

Mixed nerves:

Contain the axons of both i.e sensory and motor neurons.

Hind brain:

Hind brain consists of three major parts.

Medulla oblongata:

Lies on the top of spinal cord it controls breathing, heart rate and blood pressure. It also controls many reflexes such as vomiting, coughing, sneezing etc.Information that passes between spinal cord and the rest of brain pass through medulla.

Cerebellum:

Cerebellum is behind medulla. It coordinates muscle movements.

Pons:

Pons is present on top of medulla it assists medulla in controlling breathing. it also serves as a connection between cerebellum and spinal cord.

Adrenal glands:

Two adrenal glands are situated above kidneys Each adrenal glands consists of two parts the outer parts is cortex and the inner part is medulla. Adrenal medulla secretes a hormone called epinephrine or adrenaline is response to stress. It prepares our body to overcome emergency situations.Therefore adrenaline is also termed as emergency hormone.The adrenal cortex secretes many hormons called corticosteroids which maintain the balance of salts and water in blood.

"When a person experiences fear anger or anxiety of heartbeat increase blood pressure increase blood flow to the limbs increase blood flow to the elemantory and skin is reduced.Such changes prepare the body to face any emergency situation".

Forebrain:

Forebrain is the largest area of brain.It is most highly developed in humans.Following are the important parts of this region.

Thalamus:

Thalamus lies just below cerebrum.It serves as a relay centre between various parts of brain and spinal cord .It also receives and modifies sensory impulses before thay travel to cerebrum.Thalamus is also involved in pain perception and consciousness.

Hypothalamus:

Hypothalamus lies above midbrain and just below thalamus in human. It is roughly the size of an almond. One of the most important functions of hypothalamus is to link nervous system and endocrine system. It controls the secretions of pituitary gland. It also controls feelings such as rage, pleasure and sorrow.

Cerebrum:

Cerebrum is the largest part of forebran.It controls skeletal muscles,thinking, intelligence and emotions it is divided into cerebral hemispheres.The anterior parts of cerebral hemisphere are called olfactory bulbs which receive impulses from olfactory nerves and create the sensation of smell.The upper layer of cerebral hemisphere i.e cerebral cortex consists of grey matter.The grey matter of nervous system consists of cell bodies and non-myelinated axons.

Lobe Function:

Frontal

Controls motor functions, permits conscious control of skeletal muscles and coordinates movements involved in speech.

Parietal:

Contains sensory areas that receive impulses from skin

Occipital:

Receives and analyzes visual information.

Temporal:

Concerned with hearing and smell.

Spinal cord:

The spinal cord is tubular bundle of nerves. It starts from brain stem and extends to lower back. Like brain, spinal cord is also covered by meninges.The vertebral column surrounds and protects spinal cord.

The outer region of spinal cord is made of white matter the central region i butterfly shaped that surrounds the central canal. It is made grey matter.31 pairs of spinal nerves arise along cord These are mixed nerves because each contains axons of both sensory and motor neurons at the point where a spinal nerve arises from spinal cord, there are two roots of spinal nerve. Both roots unite and form one mixed spinal nerve.

The dorsal roots contains sensory axons and region where cell bodies are located.

The ventral root contains axons of motor neurons.

Spinal cord performs two main functions:

It serves as a link between body parts and brain. Spinal cord transmits nerve impulses from body parts to brain and from brain to body parts.

Spinal cord also act as a coordinator, responsible for some simple reflexes.

( Make diagram)

Parathyroid gland:

These are four glands situated on the posterior side of thyroid gland. They produce a hormone known as parathormone.It increase the level of calcium ions in blood. when there is increased production of parathormone, more than normal calcium salts are absorbed from the bones and added to blood.

Consequently the bones become brittle if there is deficiency in the production of parathormone, blood calcium level falls. It leads to tetany, which affects the functioning of muscles.

These are the organ that receive information from receptors and send message to particular organ for praper action brain and spinal cord are coordination they cord are coordination they are two types of coordination in organ’sms nervous coordination brought about by nervous system chemical coordination brought about by endocrine system.

The involuntary and immediate response to a stimulus.

Reflex are:

The nerve pathway over which the nerve impulse travel in a reflex action.

Neuron are specialized cells that are able to conduct nerve impulse from receptor to coordination and from coordination to effectors.

The part of the nerve cell that contain nucleus .

Genetic disorder in which person fails to recognize the basic colour.

The middle layer is called choroid it contain blood versels and gives the inner eye a dark colour.

The poor of the coordination system that respond when stimulated by nerve impulses or hormones.

The part of the hind brain and controls muscles movement .

Cerebrum:

The largest part of the forebrain controls many sensory and motor function.

Tympanic membrane a membrane stretched across the inner end of the auditory canal of the ear.

A gland that discharges its recretion into a duct.

The harmone product by the islets of larger hans lowers the blood glucose level.

Nerve cell the unit of the nervous system able to conduct nerve impulses.

Complete loss of function by one or more muscle group due to damage in the nervous system.

The endocrine gland attached to the hypothalamus that controls many other endocrine glands in the body.

The organ tissues or cells which deteet particular type to stimuli.

The inner most and the sensitive layer in the eye.

The nerve which contain only the axons of sensory neurons.

Thyroid:

The endocrine gland located in front of the trachea secretes harmones thyroxin and calcitonin.

A condition that is due to low blood calcium and is characterized by spasms of the hand and feet tetany is generally considered to result from very low calcium level in blood.

The endocrine system chemically controls the various function of cells tissues and organs through the secretion of harmone the endocrine system imclude the adrenal gland parathyroid gland pituitary gland and thyroid gland as well as ovaries pancreas and testes.

Body synthesizes rhodospin from vitamin A and that is why the deficiency of vitamin A cause poor night vision this problem is called night blindness.

The part of the forebrain below the thalamus control body temperature blood pressure and emotion.

Blind spot a point on the retina of the eye where the optic nerve enters the retina no photosensitive cell exit at this point.