CBSE Class 10 Answered

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Asked by priyadarshini_selvam | 24 Mar, 2010, 03:17: PM

Expert Answer

1) Ganglia is a mass of nerve tissue or a group of nerve cell bodies. They are collections of nerve cells forming a nerve center, especially one located outside the brain or spinal cord. ganglia are given specific names which indicate their function or location, such as acoustic, cardiac, carotid, jugular, etc.

The brain is made of three main parts: the forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus. The midbrain consists of the tectum and tegmentum. The hindbrain is made of the cerebellum, pons and medulla.

The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four lobes: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.

Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving
Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli
Occipital Lobe- associated with visual processing
Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech.

Thalamus has sensory and motor functions. Almost all sensory information enters this structure where neurons send that information to the overlying cortex. Axons from every sensory system (except olfaction) synapse here as the last relay site before the information reaches the cerebral cortex.

Hypothalamus is involved in functions of homeostasis, emotion, thirst, hunger, circadian rhythms, and control of the autonomic nervous system. In addition, it controls the pituitary.

Midbrain - It is involved in functions such as vision, hearing, eye movement, and body movement. The anterior part has the cerebral peduncle, important for voluntary motor function.

Hindbrain-

The cerebellum is associated with regulation and coordination of movement, posture, and balance.

Pons is involved in motor control and sensory analysis. It has parts that are important for the level of consciousness and for sleep. Some structures within the pons are linked to the cerebellum, thus are involved in movement and posture.

Medulla Oblongata is responsible for maintaining vital body functions, such as breathing and heart rate.

1) Pituitary Gland -

i) Growth hormone (GH) - Stimulates growth of all body tissues but especially skeletal muscle and bone.

ii) Thyroid-stimulating hormone (TSH) promotes normal development and activity of the thyroid gland.

iii) Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to release corticosteroids.

iv) Gonadotropins—follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regulate the functions of the gonads in both sexes. FSH stimulates sex cell production; LH stimulates gonadal hormone production.

v) Prolactin (PRL) promotes milk production in humans.

vi) The neurohypophysis stores and releases two hypothalamic hormones:

Oxytocin stimulates powerful uterine contractions, which trigger labor and delivery of an infant, and milk ejection in nursing women.
Antidiuretic hormone (ADH) stimulates the kidney tubules to reabsorb and conserve water, resulting in small volumes of highly concentrated urine and decreased plasma osmolality.

2) Thyroid gland -

Thyroxine (T4) and triiodothyronine (T3), which increase the rate of cellular metabolism.

3) Parathyroid gland -

Parathyroid hormone (PTH), which causes an increase in blood calcium levels by targeting bone, the intestine, and the kidneys.

4) Adrenal Glands -

Hormones of adrenal cortex -

Mineralocorticoids (primarily aldosterone) regulate sodium ion reabsorption and potassium ion excretion by the kidneys. Sodium ion reabsorption leads to water reabsorption, and increases in blood volume and blood pressure.
Glucocorticoids (primarily cortisol) are important metabolic hormones that help the body resist stress by increasing blood glucose, fatty acid and amino acid levels, and blood pressure.
Gonadocorticoids (mainly androgens) are produced in small amounts throughout life.

The adrenal medulla produces catecholamines (epinephrine and norepinephrine). The catecholamines enhance and prolong the fight-or-flight response to short-term stressors.

5) Pancreas

The endocrine portion (pancreatic islets) of pancreas releases insulin, glucagon, somatostatin and pancreatic polypeptide.

Glucagon - when blood levels of glucose are low, it stimulates the liver to release glucose to the blood.

Insulin - is released when blood levels of glucose rise. It increases the rate of glucose uptake and metabolism by most body cells.

6) Ovaries -

Estrogens - Stimulate maturation of the female reproductive system and development of the secondary sex characteristics.

Progesterone - It works with estrogens in establishing the menstrual cycle.

7) Testes -

Testosterone - It promotes maturation of the male reproductive organs, development of secondary sex characteristics, and production of sperm by the testes.

8) Pineal gland -

Melatonin - It which influences daily rhythms and may have an antigonadotropic effect in humans.

9) Thymus gland -

thymosin and thymopoietins are important to the normal development of the immune response.

Answered by | 24 Mar, 2010, 05:46: PM