Unit 2 part 1

Comprehensive practice flashcards covering the Endocrine System overview, communication types, major glands, hormone classifications, and specific hormonal actions based on the lecture transcript.

How is paracrine communication defined in the endocrine system?

Hormones diffuse into local extracellular fluid to alter the function of neighboring cells.

What is autocrine communication?

Hormones diffuse into local extracellular fluid and alter the function of the cell that released it.

Compare the effector cells of the endocrine system versus the nervous system.

The endocrine system targets cells throughout the body, while the nervous system targets postsynaptic cells in muscle and glandular tissue only.

How do the regulatory effects of the endocrine and nervous systems differ in timing?

Endocrine effects are slow to appear and long-lasting, whereas nervous system effects appear rapidly and are short-lived.

Define receptor, specificity, and affinity in the context of hormones.

A receptor is a membrane-bound or intracellular protein with a specific shape to bind a hormone; specificity means only specific hormones bind to specific receptors; and affinity is the bond strength between the hormone and receptor.

What are the three types of hormone release stimuli?

Hormonal (hormone stimulates/inhibits another), Neural (nervous system structure stimulates release), and Humoral (dissolved substances in the blood, other than hormones, stimulate release).

What are the characteristics of steroid hormones?

They are hydrophobic, require chaperone molecules for blood transport, enter cells to use intracellular receptors, are long-lasting, and are degraded by intracellular enzymes.

What are the characteristics of amino acid based hormones?

They are hydrophilic, can dissolve in blood, cannot enter a cell (requiring a membrane-bound receptor), have a short duration, and are degraded by the liver or kidneys.

Describe the steps of the cAMP second messenger pathway for amino acid based hormones.

1. Hormone binds to a receptor; 2. G-protein is activated; 3. Adenylate cyclase converts $ATP$ into $cAMP$; 4. $cAMP$ activates protein kinase; 5. Phosphorylated proteins initiate or inhibit cellular processes.

What is the hypophyseal portal tract?

A shared capillary bed between the hypothalamus and the anterior pituitary through which the hypothalamus secretes releasing hormones.

What is the action of Growth Hormone (GH) and what stimulates its release?

It is stimulated by $GHRH$ from the hypothalamus and acts on all cells of the body to stimulate mitosis (cell division/growth).

What is the target organ and action of Thyroid Stimulating Hormone (TSH)?

The target organ is the thyroid, and its action is to stimulate thyroxine release.

How do LH and FSH differ in their actions on the gonads?

Luteinizing Hormone ($LH$) stimulates sex steroid release, while Follicle Stimulating Hormone ($FSH$) stimulates sex cell development (egg and sperm).

What is the relationship between PIH and prolactin?

$PIH$ (Prolactin Inhibiting Hormone) is normally released to prevent prolactin; the hypothalamus must stop $PIH$ release for milk production to occur.

What are the two hormones released by the posterior pituitary and their functions?

Oxytocin (stimulates milk ejection and maternal behavior) and Antidiuretic Hormone ($ADH$ or vasopressin, stimulates water retention).

What is the role of melatonin and what stimulates its release?

Released by the pineal gland, it is stimulated by neurons of the visual cortex perceiving darkness and acts on the brain to stimulate sleep.

What is the function of thymosine?

Released by the thymus, it stimulates $T$-cell production and cell-mediated immunity.

What is the 'calorigenic effect' associated with thyroxine ($T_3$ & $T_4$)?

The regulation of the rate of metabolism in all cells of the body.

Contrast the effects of calcitonin and parathyroid hormone (PTH) on blood calcium.

Calcitonin (from the thyroid) decreases blood calcium by stimulating bone deposit; $PTH$ (from the parathyroid) increases blood calcium by stimulating bone resorption.

How do insulin and glucagon regulate blood sugar?

Insulin (from the pancreas) aids glucose entry into cells to decrease blood sugar; Glucagon increases glucose manufacture and release from the liver to increase blood sugar.

What are the hormones of the adrenal medulla and what stimulates them?

Epinephrine and norepinephrine, which are stimulated by the sympathetic nervous system for acute stress responses.

What is the action of aldosterone and where is it released?

Released from the adrenal cortex, it stimulates sodium and water reabsorption in the kidneys and potassium excretion.

What is the action of cortisol?

It increases glucose production and metabolism and suppresses the immune response as part of the chronic stress response.

Define the three hormone relationships: synergism, antagonism, and permissiveness.

Synergism: two hormones have an additive effect; Antagonism: two hormones perform opposite functions; Permissiveness: one hormone gives another permission to operate.