A&P2 Exam TWO (Endocrine)

What is a major function of the endocrine system?

Regulates cells by producing and secreting hormones.

What are endocrine glands?

Ductless glands that secrete hormones into interstitial fluid or for transport by the bloodstream.

Primary VS Secondary Organs

-Primary Organs: Apart of the endocrine system and screte hormones

-Secondary Organs: Secrete hormones but are not apart of the endocrine system

What are the three types of stimuli that regulate hormone release?

Hormonal, humoral, and neural stimuli.

What is hormonal stimulus?

Hormone secretion changes in response to other hormones.

What is humoral stimulus?

Hormone release triggered by a change in the level of an ion or other substance in the blood or extracellular fluid.

What is neural stimulus?

Hormone secretion responds to signals from the nervous system.

What is endocrine signaling?

Secreted into the bloodstream and affect distant target cells.

What is paracrine signaling?

Secreted into extracellular fluid and affect nearby cells.

What is autocrine signaling?

Secreted into extracellular fluid and affect the same cell that secreted them.

What are receptors?

Proteins that hormones bind to on target cells.

Where can hormone receptors be located?

In the plasma membrane, cytosol, or nucleus.

What determines whether a cell responds to a hormone?

The cell must have the appropriate receptor for that hormone.

What is up-regulation?

A decrease in hormone levels causes an increase in receptors which causes an increase in cell sensitivity to hormones.

What is down-regulation?

An increase in hormone levels causes a decrease in receptors, which causes a decrease in cell sensitivity to hormones.

What are the three major hormone classes?

Amino acid-based hormones, peptide/protein hormones, and steroid hormones.

Are amino acid-based hormones hydrophilic or hydrophobic?

Hydrophilic (except for the thyroid hormone which is lipophilic and amino acid-based)

Are peptide/protein hormones hydrophilic or hydrophobic?

Hydrophilic.

Are steroid hormones hydrophilic or hydrophobic?

Hydrophobic (lipid-soluble).

How do free amino acid-based and peptide/protein hormones travel in the blood?

They travel freely through plasma and can diffuse out of the blood.

How do free hormones work?

→ Travel freely in the blood

→ Bind to receptors on the cell membrane

→ Use a second messenger inside the cell

→ Activate proteins that change cell activity

How do bound hormones travel in the blood?

They travel through the blood via protein carriers.

How do bound hormones work?

→ Travel bound to transport proteins in the blood

→ Detach from the protein

→ Diffuse through the cell membrane

→ Bind to receptors in the cytoplasm or nucleus

→ Alter cell activity

What is negative feedback?

A hormone's actions lead to a reduction in the original stimulus and stabilize conditions back toward a set point.

What is positive feedback?

A hormone's actions lead to amplification and increased production.

What happens during negative feedback when hormone levels increase?

Secretion from the hypothalamus and anterior pituitary decreases.

What are the three tiers of endocrine control?

Hypothalamus, anterior pituitary, and target organs.

What happens in first-tier control?

The hypothalamus releases hormones.

What happens in second-tier control?

The anterior pituitary releases hormones.

What happens in third-tier control?

Target organs release hormones.

What are some major hypothalamic hormones? (5)

TRH, CRH, GnRH, GHRH, and somatostatin.

What are some major anterior pituitary hormones? (6)

Prolactin, TSH, ACTH, LH, FSH, and GH.

What does TRH stand for?

Thyrotropin-releasing hormone.

What does CRH stand for?

Corticotropin-releasing hormone.

What does GnRH stand for?

Gonadotropin-releasing hormone.

What does GHRH stand for?

Growth hormone-releasing hormone.

What does TSH stand for?

Thyroid-stimulating hormone.

What does ACTH stand for?

Adrenocorticotropic hormone.

What does LH stand for?

Luteinizing hormone.

What does FSH stand for?

Follicle-stimulating hormone.

What does GH stand for?

Growth hormone.

What does ADH stand for?

Antidiuretic hormone.

What are the two hypothalamic-hypophyseal systems?

The hypothalamic-hypophyseal tract and the hypothalamic-hypophyseal portal system.

What happens in the hypothalamic-hypophyseal tract?

Nerve fibers transport hormones synthesized by the hypothalamus to the posterior pituitary, where they are stored and released.

What happens in the hypothalamic-hypophyseal portal system?

Specialized capillaries connect the hypothalamus and anterior pituitary through portal veins.

What is oxytocin?

A posterior pituitary hormone involved in milk ejection, uterine contractions, attachment, and bonding.

What stimulates oxytocin release?

Uterus and cervix stretching during labor, suckling, social bonding, and sexual activity.

What are the main effects of oxytocin?

Milk ejection, uterine wall contractions, and attachment/bonding.

What type of feedback loop is associated with oxytocin?

Positive feedback.

What is ADH?

Antidiuretic hormone, which promotes water retention by the kidneys.

What stimulates ADH release?

An increase in blood solute concentration.

What are the main effects of ADH?

-Increased water retention

-Increased blood volume

-Decreased urine production.

What is diabetes insipidus?

A condition caused by deficient ADH or resistance to ADH.

What are symptoms of diabetes insipidus?

-Thirst

-Dehydration

-Increased solute concentration in blood

-Increased urination

-Dilute urine.

What is prolactin?

An anterior pituitary hormone that promotes mammary gland development and milk production.

What stimulates prolactin release?

-TRH

-Elevated estrogen during pregnancy

-Suckling during lactation and decreased dopamine.

What is dopamine's role in prolactin release?

Dopamine acts as a prolactin-inhibiting factor.

What is TSH and what does it do?

Thyroid-stimulating hormone; it promotes thyroid gland growth and development and regulates thyroid hormone production.

What stimulates TSH release and what inhibits it?

TRH stimulates TSH release; somatostatin inhibits it.

What is LH and what stimulates its release?

Luteinizing hormone; it is stimulated by GnRH (one of the two Gonadotropin hormones)

What does LH do?

-Development of gonads

-Stimulates the production of testosterone in the testes

-Stimulates ovaries to produce androgens

-Triggers ovulation

-Role in progesterone production

What is FSH and what stimulates its release?

Follicle-stimulating hormone; it is stimulated by GnRH. (The second gonad hormone)

What does FSH do?

-Triggers production of factors that bind and concentrate testosterone

-Stimulates androgens to be converted into estrogens maturation of ovarian follicles.

What is ACTH and what stimulates its release?

Adrenocorticotropic hormone; it is stimulated by CRH and stress

What does ACTH do?

It promotes growth and development of the adrenal cortex and the release of adrenal gland hormones.

What stimulates growth hormone release?

GHRH, stress, exercise, fasting, and protein ingestion.

What are the short-term effects of GH?

Increased blood glucose, increased glucose production, and increased fat breakdown.

What are the long-term effects of GH?

Increased cell division, decreased blood glucose, and increased protein synthesis.

What inhibits growth hormone release?

Somatostatin.

What is IGF?

Insulin-like growth factor, associated with the effects of growth hormone.

What are the major thyroid hormones?

Triiodothyronine (T3) and thyroxine (T4).

What stimulates T3 and T4 production?

TSH.

What are the major effects of T3 and T4?

Basal metabolic rate, thermoregulation, growth, and development.

Which thyroid hormone is produced in greater amounts and which is more active?

T4 is produced in greater amounts; T3 is more active.

What are the approximate half-lives of T3 and T4?

T3 is about 24 hours; T4 is about 7 days.

Can most tissues convert T4 to T3?

Yes.

What happens to T3 and T4 in hyperthyroidism described in the notes?

-Immune system produces abnormal proteins

that mimic TSH

T3 and T4 increase while TSH and TRH decrease.

What are symptoms of hyperthyroidism listed in the notes?

Increased metabolic rate, decreased weight, increased heat production, and increased blood pressure.

What happens in the autoimmune hypothyroidism described in the notes?

The thyroid gland is attacked, causing T3 and T4 to decrease while TSH and TRH increase.

What are symptoms of hypothyroidism listed in the notes?

Decreased metabolic rate, increased weight, decreased heat production, decreased heart rate, and decreased blood pressure.

What is calcitonin and what stimulates its release?

Calcitonin is a thyroid hormone involved in calcium regulation; it is stimulated by an increase in Ca2+ blood levels.

What are the effects of calcitonin?

It inhibits osteoclasts, stimulates osteoblasts, and decreases Ca2+ reabsorption in the kidneys and intestines.

What stimulates parathyroid hormone release?

Decrease in Ca2+ blood levels

What are the main effects of parathyroid hormone?

It increases Ca2+ reabsorption in the kidneys and small intestine and increases osteoclast activity.

What hormones are produced by the adrenal cortex?

Aldosterone, cortisol, and androgens.

What hormones are produced by the adrenal medulla?

Epinephrine and norepinephrine.

What is aldosterone?

A mineralocorticoid produced by the adrenal cortex.

What stimulates aldosterone release?

-Decrease in blood pressure and blood volume

-Increase in K+ levels and H+ levels.

What are the major effects of aldosterone?

Increased Na+ retention

-Increased water absorption

-Maintenance of ECF and blood volume, which affects blood pressure

-An increase in K+ and H+ ion loss in urine.

How does aldosterone affect blood pressure and blood pH?

By maintaining ECF and blood volume, it affects blood pressure; H+ ion loss helps regulate blood pH.

What is the HPA axis?

The hypothalamic-pituitary-adrenal axis involved in the body's response to stress.

What are the steps of the HPA axis?

1. The sympathetic nervous system

triggers the hypothalamus to release

corticotropin-releasing hormone (CRH)

2. CRH stimulates anterior pituitary to

release Adrenocorticotropic hormone

(ACTH)

3. ACTH stimulates adrenal glands to

release Cortisol

4. Cortisol inhibits release of CRH from

hypothalamus, ending stress response

How does the HPA axis end the stress response?

Cortisol inhibits CRH release from the hypothalamus.

What is cortisol?

A glucocorticoid produced by the adrenal cortex.

What are the major effects of cortisol?

-Increase in glycogen breakdown into glucose=increase in blood glucose

-Increase in protein breakdown in muscle

-Increase of release of fatty acids from adipose tissue

-Inhibits the inflammatory response.

What are adrenal androgens and what stimulates them?

Weak precursor sex hormones synthesized in small amounts by the adrenal cortex.

Stimulated by ACTH

What can adrenal androgens be converted into?

Stronger androgens and estrogen.

What role do adrenal androgens have?

They support puberty.

What stimulates epinephrine and norepinephrine

The sympathetic nervous system and ACTH

What are the major effects of epinephrine and norepinephrine?

• Increase in heart rate and contraction force

• Dilates bronchioles = increase airflow

• Constricts blood vessels in skin, digestive and urinary organs

• Decreases digestion and urinary functions

• Dilates blood vessels supply skeletal muscles, pupils