Physiology Revision - Endocrine System

Question 1

What are the 4 functions of hormones?

Answer 1

1. Regulate chemical composition and volume of internal environment
2. Control growth and development
3. Regulate Operation and Reproductive System
4. Help establish circadian rhythm

Question 2

What are the 3 major structural classes of hormones?

Answer 2

1. Amines - ex. thyroid hormones, dopamine, catecholamines (epinephrine/norepinephrine)
2. Peptides and Proteins - the majority of hormones ex. insulin
3. Steroids - ex. aldosterone, cortisol, androgens, estrogens

Question 3

How are hormones transported in the blood?

Answer 3

Circulate in dissolved in plasma

• ex. peptides and catecholamines are water soluble, some peptides bind to plasma proteins instead

Bind to plasma proteins

• ex. steroid and thyroid hormones

Question 4

What is hormone secretion controlled by?

Answer 4

1) Ion or nutrient concentration ex. blood glucose C

2) Neural input to the endocrine cells (neurotransmitters)

• Neural input from the autonomic NS (hypothalamus) controls the secretion of many hormones

3) Other hormones

• a hormone that stimulates the secretion of another hormone is often referred to as a tropic hormone

Question 5

Describe the process of testosterone production.

Answer 5

1. Hypothalamus secretes Gonadotropin hormone-releasing hormone (GnRH)
2. Anterior Pituitary gland secretes FSH and LH
3. Testosterone is produced by the interstitial cells in the testes

Testosterone produces muscle growth and development of sex characteristics

Question 6

Describe the process of thyroxine production. What does thyroxine do?

Answer 6

1. Hypothalamus secretes thyrotropin-releasing hormone (TRH)
2. Anterior pituitary gland secretes thyroid stimulating hormone (TSH)
3. Thyroid gland produces thyroxine (T4 and T3)

Thyroxine is associated with higher metabolic rates(T3 and T4) and the development of the NS (T3)

Question 7

Describe the process of cortisol production. What does cortisol do?

Answer 7

1. Hypothalamus secretes corticotrophin releasing-hormone (CRH)
2. Anterior Pituitary gland secretes Adrenocorticotropic hormone (ACTH)
3. ACTH acts on the adrenal glands and they produce cortisol

Cortisol acts to:

• maintain blood pressure through affecting responsiveness of smooth muscle to epinephrine and norepinephrine
• Cortisol has anti-inflammatory and anti-immune functions
• During stressful situations acts to stimulate metabolism through protein and triglyceride catabolism (breakdown)
• During stress, synergistically with epinephrine

Question 8

What is the infundibulum?

Answer 8

A pituitary stalk, containing axons from neurons in the hypothalamus and small blood vessels. Connects the hypothalamus to the pituitary

Question 9

How does breast development and milk production occur in women?

Answer 9

1. Hypothalamus secretes dopamine (DA)
2. Dopamine acts on the Anterior pituitary gland to secrete prolactin

Question 10

What does IGF-1 do? How is it produced?

Answer 10

IGF-1 is a hormone secreted by the liver and other cells that acts to stimulate cell division

1. Hypothalamus secretes GnRH (Gonadotropin-releasing hormone)
2. GnRH acts on the Anterior pituitary gland which then releases Growth Hormone. The growth hormone is inhibited by somatostatin (SST).
3. The growth hormone acts on the liver and other cells to secrete IGF-1

Question 11

What is DHEA?

Answer 11

DHEA is a hormone produced by the adrenal cortex. It is a precursor for sex hormones and is purported to be anti-aging

Question 12

What hormones influence growth?

Answer 12

• Growth hormone
• T3
• Insulin (mainly during fetal life)
• Testosterone and estradiol/estrogen