Endocrine System II

two types of feedback control

1. negative

2. positive

positive feedback control

response to stimulus amplifies the stimulus

negative feedback control

response to stimulus reduces the stimulus

endocrine signaling

a cell targets a distant cell through the bloodstream

neuroendocrine signaling

neurosecretory cell produces neurohormones that go to the bloodstream and then in everywhere in the body

two kinds of hormonal effects

1. tropic

2. non-tropic

tropic effect

act on another endocrine gland to stimulate the release of other hormones

non-tropic effect

act directly on target tissue

hyposecretion of hormones

hormone production too low

hypersecretion of hormones

hormone production too high

hypothalamus

• in brain

• neuroendocrine

• controls most hormone activity

two modes of action for the hypothalamus

1. produces & releases releasing hormones (RH) and inhibiting hormones (IH)

2. produces antidiuretic hormone (ADH) and oxytocin (OT)

SEQ hypothalamus production and release of RH and IH

• RH & IH

• into pituitary portal veins

• anterior pituitary (target tissue)

SEQ hypothalamus production of antidiuretic hormone (ADH) and oxytocin

• ADH & OT produced in cell bodies

• axons extend into posterior pituitary

• stored in vesicles in axon terminals until neuron is stimulated

• released by posterior pituitary

Posterior pituitary involves which hormones?

antidiuretic hormone (ADH) and oxytocin (OT)

ADH stimulus

dehydration

ADH target tissue

kidneys;

returns more water to blood → less urine produced

oxytocin target tissues

• uterine → contractions

• mammary glands → milk

• brain → behavior (maternal care, pair bonding)

Anterior pituitary involves the ____ gland.

endocrine

Endocrine gland produces hormones into…

bloodstream

Every anterior pituitary hormone is controlled by at least one…

releasing hormone (RH)

GnRH (Gonadotropin RH) → LH → (target) → (effects)

target = reproductive system

effects = stimulates production of sex hormones by gonads

GnRH (Gonadotropin RH) → FSH → (target) → (effects)

target = reproductive system

effects = stimulates production of sperm and eggs

TRH (Thyrotropin RH) → TSH (thyroid stimulating hormone) → (target) → (effects)

target = thyroid gland

effects = stimulates the release of thyroid hormone (TH), which regulates metabolism

GHRH (growth hormone RH) → GH → (target) → (effects)

target = liver, bone, muscles

effects = induces targets to produce insulin-like growth factors (IGF), which stimulate body growth & a higher metabolic rate

CRH (Corticotropin RH) → ACTH (adrenocorticotropic hormone) → (target) → (effects)

target = adrenal cortex

effects = induces targets to produce glucocorticoids which regulate metabolism and the stress response

thyroid gland

2 lobes on the surface of the trachea

What are the two hormones produced by the thyroid gland?

T3 & T4

thyroid hormone (TH)

• T3 & T4

• target cells throughout the body

T3 & T4

derived from tyrosine (amino acid) & iodine

What does the thyroid gland do?

• stimulates metabolism

• maintains normal BP, HR, muscle tone

• regulates digestive & reproductive functions

SEQ regulation of thyroid hormone secretion

1. hypothalamus secretes thyrotropin RH (TRH)

2. anterior pituitary secretes thyroid stimulating hormone (TSH) into blood

3. thyroid gland (tropic effect)

4. T3 & T4

5. cells throughout the body

6. response

draw the regulation of thyroid hormone secretion

hypothyroidism

• decreased metabolic rate = weight gain & lethargy

• goiter

goiter

enlarged thyroid gland

• caused by iodine deficiency

• hyposecretion → anterior pituitary increased TSH → thyroid gland enlarged

hyperthyroidism

• high body temp & sweating → weight loss & high BP

• Grave’s disease

Grave’s disease

autoimmune disease;

abnormal antibodies bind to & stimulate TSH receptors → hypersecretion of hormone

Thyroid detects if blood Ca²⁺ levels are too high and secretes _____.

calcitonin

calcitonin target tissues

bone → inhibits Ca²⁺ removal

kidneys → increases Ca²⁺ removal

What is the major target of the growth hormone?

liver

What is the response when growth hormones reach the liver?

release of insulin-like growth factors (IGFs), which stimulates bone & cartilage growth

If growth hormone levels in the blood are high, the hypothalamus secretes…

growth hormone inhibitor hormone (GHIH)

→ anterior pituitary releases less GH

If growth hormone levels in the blood are low, the hypothalamus secretes…

growth hormone releasing hormone (GHRH)

→ anterior pituitary releases more GH

Hyposecretion of growth hormones in childhood leads to…

pituitary dwarfism

pituitary dwarfism

small, correct proportions

treatment for pituitary dwarfism

before puberty;

human GH from cadavers;

recombinant DNA tech hGH gene inserted into bacteria

Hypersecretion of growth hormones during childhood leads to…

gigantism; normal proportions

Hypersecretion of growth hormones during adulthood leads to…

acromegaly;

not taller;

abnormal bone growth in hands, feet, and head

Where are the adrenal glands?

on top of each kidney

What are the two parts of the adrenal glands?

1. adrenal cortex (outer)

2. adrenal medulla (middle)

Adrenal cortex responds to _____ signals.

endocrine

Adrenal medulla responds to _____ signals.

nervous

Adrenal cortex is used during ____ stress.

chronic

Adrenal medulla is used during ____ stress.

acute

What happens in the adrenal cortex during chronic stress?

• hypothalamus secretes corticotropin RH (CRH)

• anterior pituitary releases ACTH

• adrenal cortex produces corticosteroids

corticosteroids

synthesized from cholesterol

What are the two main types of corticosteroids?

1. glucocorticoids

2. mineralocorticoids

Glucocorticoids regulate…

glucose metabolism

Mineralocorticoids regulate…

mineral metabolism

How do glucocorticoids regulate glucose metabolism?

• breaks down muscle proteins

• liver converts amino acids into glucose

• glucose is released into blood

How do mineralocorticoids regulate mineral metabolism?

aldosterone regulates water/sodium balance in blood

alarm reaction

fight or flight response

What are the two hormones involved with the adrenal medulla?

1. epinephrine (Epi) = adrenaline

2. norepinephrine (NE)

What happens in the adrenal medulla during acute stress?

• sudden stimulus

• hypothalamus

• activates adrenal medulla via nerve impulses

• Epi & NE released

What is the response when epi and NE are released?

• increased blood to brain, muscles, heart

• breakdown of glycogen

• increased metabolic rate

• increased oxygen delivery by:

  • increased heart rate and stroke volume

  • increased breathing rate

How many glands are in the tissue surrounding the thyroid (parathyroid glands)?

4

What do the parathyroid glands do?

detect blood Ca²⁺ levels

What do the parathyroid glands do when Ca²⁺ levels are too low?

releases parathyroid hormone (PTH)

What are the direct effects of releasing the parathyroid hormone (PTH)?

• bone releases Ca²⁺

• kidneys don’t release Ca²⁺ in urine

What are the indirect effects of releasing the parathyroid hormone (PTH)?

• kidneys are stimulated to activate vitamin D

• vitamin D acts on intestine

• intestines increase uptake of Ca²⁺ from blood

draw the effect of the parathyroid glands on low blood Ca²⁺ levels

PTH and calcitonin are…

antagonistic

Pancreas maintains…

glucose homeostasis

draw the pancreas and how it works