Question

DQ3. Indicate the results of-sympathetic activation of the following structures: sweat gland, eye pupil, adrenal medulla, heart, liver ,bronchioles, blood vessels of GI, and Salivary glands?

Answer 1

The effect of sympathetic stimulation is mediated by the release of noradrenaline from the sympathetic nerve ending and adrenaline from the adrenal medulla.

Sympathetic activation:

Sweat glands:

The sympathetic stimulation of the sweat gland causes the secretion of watery fluid, and evaporation of body heat. Cutaneous vasoconstriction with sweat gland activation causes cold, clammy skin of a frightened individual.

Eye pupil:

There is a dilation of the pupil. It occurs due to the contraction of dilator pupillae muscle of the eye. It enhances the visual acuity and perception.

Adrenal medulla:

There is an increase in the secretion of epinephrine and norepinephrine (Epinephrine and norepinephrine are called emergency hormones).

Heart:

Sympathetic stimulation of the cardiovascular system increases blood pressure due to increase the cardiac output and vasoconstriction. There is a redistribution of blood flow to the skeletal muscles and heart from the splanchnic and cutaneous circulation to enhance the performance. There is an increase in heart rate, increase in conductivity in the AV node and conduction paths, increase in the contractility of the atria and ventricles.

Liver:

In the liver, there is glycogenolysis and gluconeogenesis. The supply of metabolic substrates increases due to sympathetic stimulation. The demand an for increased supply of substrate is met by the action of circulating epinephrine on hepatocytes and adipocytes. Glycogenolysis increases plasma glucose concentration. Lipolysis promo a tes increase in plasma free fatty acid level.

Bronchioles:

In the lungs, there is an increased exchange of blood gases due to the stimulation of the respiratory rate and dilation of the bronchial tree. This increases the supply of oxygen to the tissues.

Blood vessels of GI:

There is vasoconstriction of blood vessels of the gastrointestinal tract due to the sympathetic stimulation. The redistribution of blood occurs to the skeletal muscles and heart from the splanchnic and continuous circulation.

Salivary glands:

Sympathetic stimulation to the salivary gland decreases the salivary secretion. The secretion of mucus increases proportionately, permitting the lubrication of mouth despite increase ventilation and reduced salivation