Question

The hypothalamus and the primary motor cortex are the two parts of the brain that have the most direct influence over the body. Compare the ways in which each creates changes in the body and the types of function they are involved in.

Answer 1

Ans:-Hypothalmus function:-It regulates many vital functions of the body like endocrine functions, visceral functions, metabolic activities, hunger, thirst, sleep, wakefulness, emotion, sexual functions.

1.SECRETION OF POSTERIOR PITUITARY HORMONES Hypothalamus is the site of secretion for the posterior pituitary hormones. Antidiuretic hormone (ADH) and oxytocin are secreted by supraoptic and paraventricular nuclei

2.2. CONTROL OF ANTERIOR PITUITARY Hypothalamus controls the secretions of anterior pituitary gland by secreting releasing hormones and inhibitory hormones. It secretes seven hormones. i. (GHRH)

ii. Growth hormone-releasing polypeptide (GHRP) iii. Growth hormone-inhibiting hormone (GHIH) or somatostatin

iv. (TRH)

v. (CRH)

vi. (GnRH)

vii. Prolactin-inhibiting hormone (PIH)

3.REGULATION OF HEART RATE :-Hypothalamus regulates heart rate through vasomotor center in the medulla oblongata. Stimulation of posterior and lateral nuclei of hypothalamus increases the heart rate. Stimulation of preoptic and anterior nuclei decreases the heart rate.

4.REGULATION OF BODY TEMPERATURE :-Body temperature is regulated by hypothalamus, which sets the normal range of body temperature.Hypothalamus has two centers which regulate the body temperature:

i. Heat loss center that is present in preoptic nucleus of anterior hypothalamus

ii. Heat gain center that is situated in posterior hypothalamic nucleus.

5.REGULATION OF HUNGER AND FOOD INTAKE:-

Food intake is regulated by two centers present in hypothalamus:-

i. Feeding center

ii. Satiety center.

6.REGULATION OF WATER BALANCE :-Hypothalamus regulates water content of the body by two mechanisms:-

i. Thirst mechanism

ii. Antidiuretic hormone (ADH) mechanism.

7.REGULATION OF SLEEP AND WAKEFULNESS:-

Mamillary body in the posterior hypothalamus is considered as the wakefulness center. Stimulation of mamillary body causes wakefulness and its lesion leads to sleep. Stimulation of anterior hypothalamus also leads to sleep.

8.RO IN BEHAVIOR AND EMOTIONAL CHANGES:-

The behavior of human beings is mostly affected by two responding systems in hypothalamus and other structures of limbic system. These two systems act opposite to one another.

9.REGULATION OF SEXUAL FUNCTION:-

hypothalamus plays an important role in maintaining the sexual functions, especially in females. In human beings also, hypothalamus regulates the sexual functions by secreting gonadotropin releasing hormone.

10.ROLE IN CIRCADIAN RHYTHM:-

Circadian rhythm is the regular recurrence of physiological processes or activities, which occur in cycles of 24 hours.Circadian rhythm develops in response to recurring daylight and darkness. The cyclic changes taking place in various physiological processes are set by means of a hypothetical internal clock that is often called biological clock.

PRIMARY MOTOR CORTEX:-Primary motor area extends throughout the precentral gyrus and the adjoining lip of central sulcus.

Primary motor area is concerned with initiation of voluntary movements and speech.

The center for movement, as it sends all efferent (corticospinal) fibers of primary motor area. Through the fibers of corticospinal tracts, this area activates the lower motor neurons in the spinal cord. It activates both α-motor neurons and γ-motor neurons simultaneously by the process called coactivation.