Nakamura Human Physiology Lecture 9

Question 1

Chemical classification of hormones

Answer 1

Polypeptides
•Glycoproteins
•Amines
•Steroids

Question 2

Polypeptides

Answer 2

-ADH (Antidiuretic Hormone; Vasopressin) released from posterior pituitary. Causes vessel constriction, less urine.
–Insulin (decrease glucose) and glucagon (increase glucose) from pancreas

Question 3

Glycoproteins

Answer 3

-FSH (follicle stimulating hormone)
-LH (luteinizing hormone)
Gonadotropic hormones from anterior pituitary gland
Related to female menstrual cycle
Sex hormones

Question 4

Amines

Answer 4

.Hormones derived from tyrosine and tryptophan
–Includes hormones secreted by adrenal medulla, thyroid (T3 and T4) and pineal gland
-melatonin: secreted by pineal gland, regulate sleep wake cycles (circadian rhythm)

Question 5

Steroids

Answer 5

.Lipids derived from cholesterol
–Hydrophobic hormones
    •Testosterone (secreted by testes)
    •Estradiol (secreted by ovaries)
    •Cortisol (secreted by adrenal cortex)
    •Progesterone (secreted by ovaries)

Question 6

Testosterone

Answer 6

• is primarily secreted in the testes of males and the ovaries of females,
• small amounts are also secreted by the adrenal glands.
• It is the principal male sex hormone and a behavioral hormone in female.
• during menopause, male hormone increase and female drop

Question 7

Progesterone

Answer 7

-involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species.

Question 8

Estradiol

Answer 8

• is the predominant sex hormone present in females
• it also is present in males, although at lower levels. (Liver makes sure of this)
• It represents the major estrogen in humans. (Precursor)
• Estradiol has not only a critical impact on reproductive and sexual functioning, but also affects other organs including the bones.

Question 9

Hormonal interactions

Answer 9

Synergism
Permissive effect
Antagonism

Question 10

Synergism

Answer 10

The sum of the effects of two hormones secreted at the same time is greater than the individual effects of the two hormones added together.
Example: growth hormone (GH) testosterone

Question 11

Permissive effect

Answer 11

-Enhancement of a target organ to the action of a second hormone.
-enhanced in presence of another hormone
Examples: Thyroid hormone increases the number of receptors available for epinephrine at the target cell. Cortisol exerts a permissive effect on growth hormone (makes it more effective)

Question 12

Antagonism

Answer 12

• Actions of one hormone are opposite to the actions of another hormone.
• Example: Parathyroid hormone (PTH) by increasing Ca2+ & Calcitonin (CT) (decreases calcium) works against eachother

Question 13

Mechanisms of hormone action

Answer 13

Target cell receptors
-nuclear receptors (hydrophobic)
-cell membrane receptors (hydrophilic, second messenger system)
Hydrophilic: can’t go directly in through cell membrane since the cell membrane is lipid
Hydrophobic: can go directly since cell membrane is a phospholipid bilayer

Question 14

Nuclear receptors

Answer 14

-Hydrophobic steroid and thyroid hormones are transported in the blood by carrier proteins
•Receptors for hydrophobic hormones may be in the cytoplasm or in the nucleus
•Receptor (with hormone) directs the synthesis of mRNA and thus protein synthesis (transcription DNA to RNA, translation RNA to new protein)
Carrier protein to receptor protein then translocation to nucleus. mRNA to protein synthesis to steroid hormone response

Question 15

Cell membrane receptors

Answer 15

Hydrophilic hormones cannot pass through plasma membrane
•Catecholamines, polypeptides, and glycoproteins bind to receptor proteins on the target cell membrane
•Binding of hormone (1st messenger) to cell membrane receptor activates a 2nd messenger system inside the cell
•Three major 2nd messenger systems
–Adenylate cyclase and cAMP
–Phospholipase C and Ca++
–Tyrosine kinase

Question 16

Adenylate cyclase-cAMP

Answer 16

.Hormone binds to receptor protein
•Dissociation of a G-protein subunit
•alpha G-protein activates adenylate cyclase, catalyzes cyclic AMP from ATP
•cAMP attaches to inhibitory subunit of Protein Kinase A
•Protein Kinase A phosphorylates enzymes within the cell to produce hormone’s effects (activates and inactivates specific enzymes)
•cAMP inactivated by phosphodiesterase (enzyme)
–Hydrolyzes cAMP to inactive fragments

Question 17

Phospholipase C- CA2+ second messenger system

Answer 17

.•Binding of hormone to cell membrane receptor activates a G-protein, which then activates the membrane enzyme Phospholipase C (PLC)
•Phospholipase C splits PIP2 (phosphoatidylinositol 4,5 -bisphosphate) into IP3 and DAG (diacylglycerol)
•IP3 (inositol trisphosphate) diffuses through cytoplasm to ER. (2nd messenger)
•IP3 binds to a receptor on the surface of the ER and causes Ca2+ channels to open and release Ca2+ into the cytoplasm (3rd messenger)
•Ca2+ binds to calmodulin and the activated calmodulin complex activates specific protein kinase and other basic cellular functions.

Question 18

Tyrosine kinase

Answer 18

-Receptor protein on cell membrane is tyrosine kinase
•Insulin receptor consists of 2 units that dimerize when they bind with insulin
•Insulin binds to ligand–binding site, activating enzymatic site
•Autophosphorylation occurs, increasing tyrosine kinase activity
•Activates signaling molecules, altering the metabolism of the cell

Question 19

Receptor for insulin

Answer 19

• Tyrosine kinase
• 2 ends, one inside, one on surface
• 2alpha subunits extracellular, 2 beta chain in cytoplasm (why it’s called second messenger)
• Related to glucose
• Insulin binding to receptor proteins, dimerization, phosphorylation of receptor (ATP becomes ADP), phosphorylation of signal molecules, cascade of effects, glucose uptake and anabolic reactions

Question 20

Posterior pituitary gland hormones

Answer 20

Antidiuretic hormone (ADH or vasopressin): increases H2O retention in kidney
Oxytocin: promotes strong smooth muscle contractions in the uterus and milk letdown
-manufactured in hypothalamus
-stored and released in posterior pituitary

Question 21

Hypothalamic control of posterior pituitary

Answer 21

.Hypothalamus produces:
–ADH: supraoptic nucleus
–Oxytocin: paraventricular nucleus
-unmyelinated neurosecretory neurons synthesize ADH
-Within hypothalamic neurons, the hormone is packaged in secretory vesicles in the ADH-secreting neurons
•Hormones transported along the axons of hypothalamic hypophyseal tract
•Hormones stored in presynaptic terminals
•Release controlled by neuroendocrine reflexes

Question 22

Posterior pituitary hormone release regulation

Answer 22

Stimulates release Inhibits release
ADH: ⬆️in blood osmolarity. Norm blood osmolarity
And pressure
blood hypovolemia
Blood hypotension

Oxytocin: Near term pregnancy
             increases the responsiveness
             of the utereus to oxytocin;
             parturition increases the
             responsiveness of the
             mammary glands to oxytocin
             resulting in milk letdown

Question 23

Anterior pituitary effects

Answer 23

.Trophic effects: (tissue growth, mature, increase in size)
–Health of the target glands depends upon stimulation by anterior pituitary for growth
–High plasma hormone concentration causes target organ to hypertrophy (oversize, too much)
–Low plasma hormone concentration causes target organ to atrophy (undersize, weaker, smaller)

Question 24

Anterior pituitary hormones

Answer 24

Manufactured and released here
Growth hormone (somatropin): regulates growth and development of muscle, organs, etc.
Prolactin: Stim. milk production in mammary glands
TSH: Stim. production and release of thyroxin from (thyrotropin) thyroid gland(male and female metabolism)
FSH: Stim. spermatogenesis and early development of ovarian follicle
LH: Stim. testosterone synthesis and induces ovulation
ACTH(adrenocorticotropic hormone): Stim. steroid synthesis and release from adrenal cortex

Question 25

Hormones secreted by anterior pituitary and target organs

Answer 25

``` Prolactin to mammary gland Growth hormone to bone, muscle, adipose Gonadotropins (FSH and LH) to ovary and testes ACTH to adrenal cortex TSH to thyroid ```

Question 26

Hypothalamic control of the anterior pituitary

Answer 26

-Pituitary hormone release controlled by releasing hormones and release inhibiting hormones from hypothalamus •Hypothalamic hormones are transported to axon endings and released onto primary capillary bed •Hormones are transported to a secondary capillary bed in the anterior pituitary -inhibitory or stimulating -Hormones secreted into the hypothalamic hypophyseal portal system regulate the secretions of the anterior pituitary

Question 27

Feedback control of the anterior pituitary

Answer 27

.if too much hormone Negative feedback at 2 levels: –The target gland hormone can act on the hypothalamus and inhibit secretion of releasing hormones. –The target gland hormone can act on the anterior pituitary and inhibit response to the releasing hormone.

Question 27

Levels of hormone regulation for anterior pituitary

Answer 27

``` Hypothalamus (Releasing hormone) Anterior pituitary (Trophic hormone) Target organ (local level) (Target organ hormone, which can send negative or positive feedback to the AH or hypothalamus) ```

Question 27

Hypothalamus pituitary gonad axis (control system)

Answer 27

Hypothalamus ➡️ gonadotropin releasing hormone (GnRH) ➡️anterior pituitary ➡️ gonadotropins (FSH and LH)➡️ Gonads➡️sex steroid hormones (estrogens and androgens) Negative feed back can be sent from end to hypothalamus and anterior pituitary, inhibiting secretion of GnRH and inhibiting responsiveness to GnRH

Question 28

Growth hormone secretion

Answer 28

* GH (somatotropin) stimulates growth and has several metabolic effects on target organs. (Adipose tissue lipolysis release of fatty acids, most tissues decreased glucose utilization) * GH secretion stimulates the liver to release insulinlike growth factor (IGF-1), which stimulates growth of cartilage, bone, muscle, and other organs.

Question 29

Antidiuretic hormone

Answer 29

.-Decrease in blood volume or salt ingestion stimulate osmoreceptors in the hypothalamus (because increase in blood osmolarity) •As part of a reflex arc, the posterior pituitary secretes ADH, ( and the body makes you thirsty so you drink more) •ADH secretion causes water to be retained in the kidney (no salts are transported) -both these cause an increase in blood volume and decrease in blood osmolarity (Posterior pituitary regulated by osmolarity)

Question 30

Adrenal glands

Answer 30

.Each gland consists of an outer cortex and inner medulla. •Adrenal medulla: –Secretes: epinephrine (and some norepinephrine) •Innervated by sympathetic nerve fibers – increase respiratory rate – increase heart rate, cardiac output, and vasoconstriction –Stimulate glycogenolysis and lipolysis

Question 31

Adrenal cortex

Answer 31

``` .Adrenal cortex: –Stimulated by ACTH secretion from anterior pituitary (which is in turn regulated by the hypothalamus) –Consists of 3 zones •Zona glomerulosa •Zona fasciculata: •Zona reticularis: ```

Question 32

Pathway for synthesis of steroid hormones in the zone glomerulosa of the adrenal cortex

Answer 32

Cholesterol to pregnolone to progesterone to deoxycorticosterone to corticosterone to aldosterone (related to sodium retention, potassium secretion -called mineralocorticoids

Question 33

Pathway for synthesis of steroid hormones in the zone fasciculata and zona reticularis of the adrenal cortex

Answer 33

Cholesterol to pregnenolone to progesterone to deoxycorticosterone to corticosterone 17-hydroxy-pregnenolone to 17-hydroxy-progesterone to deoxycortisol to cortisol Glucocorticoids

Question 34

Pathway for synthesis of steroid hormones in the zone fasciculata and zona reticularis of the adrenal cortex (2nd one)

Answer 34

.17-hydroxy-pregnenolone to dehydroesplandrosterone (DHEA) 17-hydroxy-progesterone to androstenedione dehydroesplandrosterone (DHEA) to androstenedione to other androgens Sex steroids Made at gonads mostly but also adrenal cortex

Question 35

Glucocorticoid secretion from the adrenal cortex

Answer 35

.Release stimulated by release of ACTH •Promotes lipolysis and ketogenesis •Promotes liberation of amino acids in muscle •Promotes liver gluconeogenesis (using non glucose components to make glucose, example when undergoing starvation)

Question 36

Glucocorticoid secretion from the adrenal cortex diagram

Answer 36

.

Question 37

Cortisol secretion in response to stress

Answer 37

.•Stress stimulates pituitary-adrenal axis •Prolonged elevation of cortisol and other glucocorticoid levels reduces the ability of the immune system to fight infection -cortisol anti itch and anti inflammatory. Suppresses immune system Nonspecific stress, higher brain centers, hypothalamus, increase CRH, anterior pituitary, increase ACTH, adrenal cortex, increase cortisol, sends negative feedback back to AH and hypothalamus