Mechanism Of Action

Question 1

What are the mechanism of hydrophilic hormones with receptors in target cells?

Answer 1

1. Hormone(first messenger) interacts with the receptor on the cell membrane, forming the hormone-receptor complex
2. Hormone receptor complex causes conformational change in membrane proteins
3. Results in the production within the cell of a “second messenger e.g Cyclic-AMP or Cyclic-GMP.
4. Increase in the cell of the second messenger leads to a rapid alteration in cellular function.e.g. Action of glucagon on glycogen metabolism.

Question 2

Properties of hydrophilic hormones?

Answer 2

1.They are large, integral, transmembrane protein with specificity and high affinity for a given hormone.
2. Binding btw two hormones is reversible
3. Action of hormones depends on the plasma level of hormone.
4. Hydrophilic hormone initiate a response without entering the cell
5. Action of hydrophilic hormone can last second to hours.

Question 3

Mechanism of action of lipid hormones?

Answer 3

1. They cross cell membranes to bind with intracellular receptors forming HRC
2. HRC binds to specific sequence of nucleotides DNA bases called “Hormone response element (HRE)
3. Binding of HRE results in the synthesis of MRNA required for the synthesis of specific proteins.
4. Lipophilic hormones are slower to act and have longer duration of action than hydrophilic hormones. Their duration may range from hours to days.

Question 4

What is negative feedback loop?

Answer 4

It occurs when the original effect of the stimulus is reduced by the output. e.g. The thyroid gland is regulated by a negative feedback.

Question 5

What are the factors controlling hormones?

Answer 5

Stimulating and inhibiting agent e.g hypothalamic peptides or neurotransmitters.

Other hormones: Gonadotropin releasing hormone are released in a pulsatile function.

Some hormones exhibit cycardian rhythm

Stress can increase hormone synthesis and release

Hormones synthesized by target cells may regulate release by negative feedback loop.

Question 6

Examples of hormones with cicardian
rythym?

Answer 6

ACTH(Adrenocorticotropic hormone
Cortisol
Prolactin, TSH, GH and PTH

Question 7

What is insulin?

Answer 7

Insulin is a protein hormone secreted by the beta cells in islet of Langerhans in pancreas.

Question 8

What are the metabolic function affected by insulin

Answer 8

1. Uptake of K+ and P+
2. Glucose uptake into muscle and adipose tissue
3. Glycogenesis
4. Glycogenolysis
5. Muscle protein synthesis
6. Stimulates biosynthesis of glycogen fat and proteins. It inhibits degradation of glycogen fat and proteins.

Question 9

Insulin affect uptake of glucose into
M.A.C.W. What does M.A.C.W mean?

Answer 9

M- muscle
A- Adipose tissue
C- Connective tissue
W- White blood cells

Question 10

Insulin does not affect glucose uptake into B.L.K. What does B.L.K mean

Answer 10

B- Brain
L- Liver
K- Kidney

Question 11

What are insulin counter regulatory hormones?

Answer 11

They are hormones that oppose the action of insulin.

Question 12

Get Every Good Girl Home
means?

Answer 12

Glucagon
Epinephrine
Glucocorticoids
Growth Hormone

Question 13

What is glucagon?

Answer 13

Glucagon are hormones produced by alpha cells of the pancreas.

Question 14

What is the function of insulin?

Answer 14

They increase blood glucose level from low to normal

Question 15

What leads to the production of glucagon?

Answer 15

Hypoglycemia
Increased absorption of amino acids in the blood.
Prolonged fasting, exercise and protein rich meal.

Question 16

T4 and T3 circulate in blood plasma bound to specific binding proteins. They are:

Answer 16

Thyroxine binding protein
Transethyretin

Question 17

Secretion of throid hormone is regulated by negative-feedback loop; it occurs via HPT-axis.

Answer 17

Thyrotropin releasing hormone (TRH) secreted by hypothalamus

TRH then stimulates the anterior pituitary to produce thyroid stimulating hormone (TSH)

TSH stimulates the thyroid glands to produce thyroid hormones.

Excess amount of thyroid hormones will then feedback inhibit the anterior pituitary and hypothalamus(long-loop feedback)

In addition, excess amount of TSH will feedback inhibit the hypothalamus to stop production of TRH (short-loop feedback).

Question 18

Actions of thyroid hormones?

Answer 18

Increased basal metabolic rate(BMR)
Increase oxygen consumption
Increased thermogenesis
Activate Na+ , K+ -ATPase in cells
Increased glycolysis, glycogenolysis and gluconeogenesis.