Chapter 17: Hormones - Hypothalamus and Pituitary Flashcards Preview

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Flashcards in Chapter 17: Hormones - Hypothalamus and Pituitary Deck (16):
1

Adenohypophysis

anterior pituitary gland

2

Neurohypophysis

posterior pituitary gland

3

Growth Hormone from Pituitary

Somatotrophs (cells) of adenohypophysis synthesize and release Growth Hormone (GH)

Release is stimulated by hormone from hypothalamus (peptide), Growth Hormone Releasing Hormone (GHRH) from the hypothalamus

Growth hormone works through:
Also known as somatotropin (STH),
Second messenger mechanism,

4

Regulation and Effects of Growth Hormone

Stimulus for Release (what causes its release into blood):
Deep sleep
↓ decreased [glucose] in blood (called hypoglycemia)
↑ increased secretion of Growth Hormone Releasing Hormone (from hypothalamus)
↓ decreased Growth Hormone Inhibiting Hormone
↓ deceased IGFs (Insulin Growth Factors)

Effects immediate and long-term:
↑ increased [glucose] in blood (can cause hyperglycemia)
↑ increased fat catabolism (breakdown of fats from adipose tissue)
Stimulates tissue growth longitudinal (before puberty) and horizontal (after puberty – increased bone density)
Antagonistic to insulin in reference to blood glucose concentration

5

Acromegaly

Age-progression of a woman with hypersecretion of GH characterized by large and coarse jaw and abnormal enlargement of bones. Enlargement of vertebrae may result in hump.

6

Tetraiodothyronine (T4), or thyroxine:

4 iodine atoms,
~20 times more abundant than T3,
It is the precursor for T3

T3 and T4 are attached to globulin molecules and transported in blood plasma.

7

Triiodothyronine (T3):

3 iodine atoms,
Principal thyroid hormone,
Binds efficiently to nuclear receptors in target cells.

8

Endemic Goiter

Due to low iodine in diet is common in underdeveloped countries

Iodine supplements will restore normal T3/T4 levels in most cases

9

Negative Feedback of Thyroid Gland

Its stimulated by Thyroid Stimulating Hormone (TSH) from adenohypophysis,

TSH is synthesized by thyrotrophs (cells) found in adenohypophysis,

TSH is stimulated by another hormone – Thyroid Releasing Hormone TRH (from hypothalamus).

10

Regulation and Effects of Thyroid Hormone

Stimulus for Release (what causes its release into blood):
↓ decreased [glucose] in blood (called hypoglycemia)
↑ increased secretion of Thyroid Stimulating Hormone (from adenohypophisis)
↑ increased secretion of Thyroid Releasing Hormone (from hypothalamus)

Effects immediate and long-term:
↑ increased [glucose] in blood (can cause hyperglycemia)
Acts on pituitary to secrete Growth hormone
↑ Increases catabolism and fat breakdown
↑ Increases activity, and temperature
Regulated by negative feed-back loop
Antagonistic to insulin in reference to blood glucose

11

What do the levels of TRH, TSH and TH tell you as to where a tumor may be found?

Tumor on Adenohypophysis = Decreased TRH, Increased TSH and T3/T4

12

Adrenocorticotropic Hormone (ACTH) from pituitary

Stimulates adrenal cortex

Corticotrophs (cells) of adenohypophysis synthesize and release a large protein that is ‘cut’ into Adrenocorticotropic hormone (ACTH) and Melanocyte-Stimulating Hormone (MSH)

Release is stimulated by hormone from hypothalamus (peptide), Corticotropic Releasing Hormone (CRH) from the hypothalamus,

Growth hormone works through:
Also known as somatotropin (STH),
Second messenger mechanism,

13

Release of hormones from adrenal cortex:

Glucocorticoids from zona fasciculata primarily Cortisol (a hyperglycemic hormone)

Mineralcorticoids from zona reticularis primarily Aldosterone (conserves Na+ and water in body)

Androgens: Sex hormones such as testosterone and estrogen (in small quantities) from zona glomerulusa

14

Mineralcorticoids – Aldosterone from Adrenal Cortex

Stimulus for Release (what causes its release into blood):
Increased ACTH secretion,
Increased K+ in blood
Decreased pH

Effects:
Increases Na+ reabsorption by the kidneys (sodium conservation),
Because Na+ is retained it Increases water retention
Promotes loss of K+ and H+ by he body (excreted in urine) to regulate pH and K+

15

Glucocorticoids – Cortisol from adrenal Cortex

Stimulus for Release (what causes its release into blood):
Decreased glucose concentration in blood,
Increased ACTH secretion

Effects:
Increases glucose in blood (hyperglycemic hormone),
Decreases immune response,
Acts with epinephrine in the recovery from injury produced by inflammatory agents,
Secretion increases response to stress (and stress increases secretion – positive feedback loop).

16

Gonadocorticoids

Stimulus for Release (what causes its release into blood):
Increased ACTH,

Effects:
Development of fetal testes (testosterone in man)
Development of secondary sexual characteristics,
Deepening of voice (male)
Facial and pubic hair (male)
Maintenance of estrogen effects after menopause.