Question

1. Which of the following statements about the physiological signals is CORRECT?

a. The nervous system provides both electrical and chemical signals.

b. Chemical signals are the most physiological type of communication within the body.

c. Electrical signals are due to Na+, Cl-, K+, and Ca2+ within a cell.

d. Chemical signals are secreted by cells into the extracellular fluid.

e. Target cells are cells that respond to specific signals.

f. All of the above

2. What is TRUE about the hypothalamus? There may be more than one answer.  

a. Detects plasma osmolarity

b. Osmoreceptor

c. Produces and secretes anti-diuretic hormone (ADH)

d. Produces atrial natriuretic peptide (ANP)

e. Produces renin (enzyme)

3. What are the characteristics of the tubular reabsorption? There may be more than one answer.

a. The proximal convoluted tubule is the initial site of tubular reabsorption, where 100% of the filtrate is reabsorbed and the process is unregulated.

b. Atrial natriuretic peptide targets the principal cells of the distal convoluted tubule and collecting duct to increase the tubular reabsorption of water.

c. The descending limb of the loop of Henle only causes the reabsorption of water back into the blood of the peritubular
capillary.

d. The ascending limb of the loop of Henle causes the reabsorption of Na⁺, K^+, Cl^-, Mg²⁺, and Ca²⁺ but not the reabsorption of water due to high level of cholesterol within the membrane.

e. More than 80% of the tubular reabsorption is regulated at the distal convoluted tubule and collecting duct in the presence of aldosterone, anti-diuretic hormone, and atrial natriuretic peptide.

Answer 1

1. All of the above stands CORRECT (Option f).

The nervous system provides electrical signals although neurons are not good conductors to transmit information where as chemical signals transmitted information through the release of neurotransmitters.

Chemical signals are the most physiological type of communication within the body which occurs due to release of neurotransmitters.

Electrical signals are due to opening of channels and movement of Ions like K⁺, Cl^-, Na⁺ and Ca⁺² within the cell across cell membrane.

Chemical signals are secreted by the cells into extracellular fluid especially blood to carry the substances to the target cells. Hormones are usually secreted in this way.

Target cells are the cells that respond to specific chemical signals depending on the type of the organ and its function.

2. Option a, b, c are TRUE about hypothalamus.

Hypothalamus consists of osmoreceptors which detect change in plasma osmolarity and thus affects the synthesis and secretion of antidiuretic hormone from the supraoptic and paraventricular nuclei. Antidiuretic hormone is released into posterior pituitary through hypothalamo-hypophyseal tract.

Atrial natriuretic peptide is secreted from the cardiac muscle cells especially from the right Atrium which sensors increase in blood pressure and regulate it by causing natriuresis.

Renin is a hormone secreted by juxtaglomerular cells of kidney in response to a fall in blood pressure.

3. Option c, d, e are the characteristics of tubular reabsorption.

Proximal convoluted tubule which is the initial site of tubular reabsorption, 70% of the total filtrate is reabsorbed and the process is hormone independent and is un-regulated.

Atrial natriuretic peptide target principal cells of distal convoluted tubule and collecting duct to decrease the tubular reabsorption of sodium, thereby decreasing water reabsorption causing natriuresis.

The descending limb of loop of henle only causes reabsorption of water back into the blood of peritubular capillaries as it is only permeable to the water.

Ascending limb of loop of henle causes reabsorption of Na⁺, K⁺, Cl^-, Mg⁺² and Ca⁺² via paracellular pathway but not the reabsorption of water due to high level of cholesterol within the membrane resulting in the thick segment.

Nearly 85% of tubular reabsorption is regulated at distal convoluted tubule and collecting duct in the presence of hormones aldosterone, antidiuretic hormone and atrial natriuretic peptide regulating water and sodium reabsorption.