BIO 2640 - CH 18 pt 1

What is the main diff between nervous-system and endocrine system responses?

Nervous = fast, brief, specific responses

Endocrine = slower, longer-lasting, broader responses

What is a hormone?

a mediator molecule released in one part of the body that regulates cells in other parts

What is the difference between exocrine and endocrine glands?

Exocrine = ducted

Endocrine = ductless and secretes into blood

What are the major endocrine glands?

Pituitary, thyroid, parathyroid, adrenal, and pineal

Which organs have endocrine functions but are NOT exclusively endocrine glands

Thymus, pancreas, ovaries, and testes

Do hormones affect every cell they encounter?

No. they affect specific target tissues that have the correct receptors.

What is down-regulation?

Decrease in receptors when too much hormone is present → prevents overreaction

What is up-regulation?

Increase in receptors when hormone levels are low → makes the target cell more sensitive.

What are circulating hormones?

Hormones that circulate throughout the body in the blood

What are local hormones?

Hormones that act close to where they were secreted

Paracrine vs autocrine?

Paracrine = neighboring cells

Autocrine = same cell that secreted it

What are the lipid soluble hormones?

Steroid and thyroid hormones, and nitric oxide (NO)

How do lipid-soluble hormones travel through blood?

With transporter proteins

What are the water-soluble hormone types?

Amine + peptide/protein/glycoprotein

How do water-soluble hormones circulate?

In free form

Where do-lipid soluble hormones bind their receptors?

Inside the target-cell

Where do water-soluble hormones bind their receptors?

On the plasma membrane

What do water-soluble hormones activate after binding to the membrane?

A second-messenger system

What 3 things determine how responsive a target cell is to a hormone?

• Hormone concentration

• Number of receptors

• Influence of other hormones

What is a permissive hormone effect?

One hormone allows another hormone to exert its full effect

(Ex. cortisol + glucagon)

What is a synergistic hormone effect?

2 hormones work together to produce a greater effect

(Ex. ADH + aldosterone)

What is an antagonistic hormone effect?

2 hormones have opposite effects

(ex. PTH + calcitonin)

What is the FIRST messenger in the water-soluble hormone pathway?

The hormone

What happens first when a water-soluble hormone reaches its target?

Hormone binds its receptor on the plasma membrane.

What does the hormone-receptor complex activate?

G-protein.

What does activated G-protein activate?

Adenylate cyclase.

What does adenylate cyclase do?

Converts ATP → cAMP

What is the SECOND messenger in the water-soluble hormone pathway?

cAMP

What does cAMP activate?

Protein kinase, which triggers responses in the target cell

What links the first messenger to the second messenger?

G-protein

Water-Soluble Hormone Pathway

Hormone → receptor → G-protein → adenylate cyclase → ATP becomes cAMP → protein kinase → cellular response.

What structure is the major link between the nervous and endocrine systems?

Hypothalamus

What connects the pituitary gland to the hypothalamus?

Infundibulum

What are the two lobes of the pituitary?

• Anterior = adenohypophysis

• Posterior = neurohypophysis

What connects the anterior and posterior pituitary lobes?

Pars intermedia.

How is the anterior pituitary controlled?

Chemically by hypothalamic releasing and inhibiting hormones.

What cells make hypothalamic hormones?

Neurosecretory cells.

What are tropic hormones?

Anterior pituitary hormones that act on other endocrine systems/glands.

What does human growth hormone (hGH) do?

Stimulates IGFs → growth + protein synthesis.

What does TSH do?

Stimulates the thyroid gland to secrete thyroid hormones and take up iodine.

What does FSH do in females?

Initiates oocyte development + estrogen secretion.

What does FSH do in males?

Stimulates sperm production.

What does LH do in females?

Stimulates ovulation + estrogen/progesterone secretion.

What does LH do in males?

Stimulates testosterone production.

What does prolactin (PRL) do?

Promotes milk secretion by mammary glands.

What does ACTH do?

Stimulates glucocorticoid secretion from the adrenal cortex

What does MSH do?

unknown

Does the posterior pituitary synthesize hormones?

NO

What does the posterior pituitary do instead?

Stores and releases hormones made by the hypothalamus.

How are hypothalamic hormones transported to the posterior pituitary?

Along the hypothalamohypophyseal tract.

is posterior pituitary control chemical or electrical?

Electrical control from the hypothalamus.

What 2 hormones are released from the posterior pituitary?

• Oxytocin (OT)

• ADH/vasopressin.

What does oxytocin do to the uterus?

Enhances smooth-muscle contractions during delivery.

What does oxytocin do to the breasts?

Stimulates milk ejection.

What stimulates oxytocin-mediated milk ejection?

Infant suckling.

What is the primary effect of ADH?

Decreases urine production by causing kidneys to return more water to the blood

ADH = more or less water reabsorption?

MORE water reabsorption.

What additional effects does ADH have?

decreases water loss through sweating + arteriole constriction → increases blood pressure.