Chapter 11 Flashcards
What do endocrine glands do?
secrete hormones into the bloodstream
- ductless
Where do hormones go?
target cells that contain receptor proteins
What are neurohormones?
hormones secreted into the blood by specialized neurons
What do hormones affect?
metabolism of targets
What are amino hormones derived from? Give examples.
derived from tyrosine or tryptophan
- Norepinephrine
- Epinephrine
- Thyroxine
- Melatonin
What are polypeptide/protein hormones? Give examples.
chains of amino acids
- anti-diuretic hormone
- growth hormone
- insulin
- oxytocin
- glucagon
- ACTH
- PTH
What are examples of glycoproteins?
LH, FSH, TSH
What are steroids? Give examples.
lipids derived from cholesterol
- testosterone
- estrogen
- progesterone
- cortisol
What are steroid and thyroid hormones?
lipids
What are the 2 major thyroid hormones?
Thyroxine (T4)
Triiodothyronine (T3)
What are examples of long range reflexes?
1) hormone-secreting gland cell -> hormone -> blood vessel -> target cell
2) nerve cell -> nerve impulse -> neurotransmitter
-> neuron or effector cell
3) nerve cell -> nerve impulse -> neuro hormone into blood vessel -> target cell
What are examples of short range local control?
1) Local cell -> paracrine agent -> target cell
2) local cell -> autocrine agent -> local cell
What is the main difference between neurotransmitters and hormones?
hormones transport in blood and have more diversity of effects in hormone targets
Can chemicals be both hormones and neurotransmitters?
yes
What does it mean for hormones to be synergistic?
they work together to produce an effect
Why are synergistic hormones beneficial?
produces a larger effect together than individual effects added together
What does it mean for a hormone to have permissive effect?
enhances responsiveness of a target organ to second hormone
What does it mean for a hormone to have antagonistic effect?
action of 1 hormone inhibits effect of another
How do target cell receptors pick a hormone?
- specificity
- high affinity
- low capacity
Where are the receptors for lipophilic hormones?
in the target’s cytoplasm and/or nucleus (affect tarnscription)
- can diffuse through plasma membrane
What is genomic action? How long does it take?
takes at least 30 minutes
- when lipophilic hormones target the nucleus and affects transcription
What is nongenomic action?
receptors for water-soluble are on surface of target cell
- act through 2nd messengers
What are nuclear hormone receptors?
receptors that bind to lipid hormones attached to carrier proteins and dissociate from carriers to pass through plasma membrane of targets
What is the function of nuclear hormone receptors?
transcription factors when bound to hormone ligands
- activates transcription factors
- constitutes a superfamily composed of steroid family and thyroid hormone family
What domains do nuclear hormone receptors have?
ligand (hormone) binding: binds hormone and translocate to nucleus
DNA-binding: binds to hormone-response element (HRE) on DNA located adjacent to target gene
What is the HRE made of?
2 half-sites
- 2 ligand bound receptors can bind to each HRE (dimerization) to stimulate transcription of target gene
What does the thyroid secrete?
90% T4 (thyroxine) and 10% T3
What can T4 change to?
- bind to carrier protein to become thyroid binding globulin (TBG)
- converts to T3 inside cell that can bind to receptor protein in nucleus
How is HRE activated?
- T3 and receptor bind to 1 half site
- retinoic acid binds other half-site
- both work together to activate HRE
- stimulates transcription of target gene
What hormones use 2nd messengers? Why?
water soluble hormones use cell surface receptors
- can’t pass through plasma membrane
- actions mediated by 2nd messengers
- hormone = extracellular signal
What do 2nd messengers do?
carries signal from receptor to inside of cell
What does cAMP do?
mediates effects of many polypeptide and glycoprotein hormones
How is cAMP made?
1) hormone binds to receptor causing dissociation of a g-protein subunit
2) g-protein subunit binds to and activates adenylate cyclase
3) adenylate cyclase converts ATP into cAMP
Where does cAMP attach?
inhibitory subunit of protein kinase
How is cAMP inactivated?
by phosphodiesterase
How is cAMP used?
inhibitory subunit dissociates to activate protein kinase
- phosphorylates enzymes that produce hormone’s effects
What is the function for phospholipase-C-Ca++?
2nd messenger system for some hormones
How is phospholipase C activated?
hormone binds to surface receptor
- activates G-protein
- activates phospholipase C
How does phospholipase C work?
splits membrane phospholipid into 2nd messengers IP3 and DAG
What does IP3 do and what does it lead to?
IP3 diffuses through cytoplasm to ER
- causes Ca++ channels to open
What happens after Ca++ diffuses into the cytoplasm?
binds to and activates calmodulin
What does Ca++-calmodulin do?
activates protein kinases to phosphorylate enzymes that produce hormone’s effects
Where does epinephrine activation occur?
liver cell
What is tyrosine kinase used for?
insulin and many growth factors to cause cellular effects
What is tyrosine kinase made of?
2 units that form active dimer when insulin binds
What can an activated tyrosine kinase do?
phosphorylates signaling molecules that induce hormone/growth factor effects
What does insulin stimulate?
glucose uptake by GLUT4 carrier proteins
How does GLUT4 carrier protein work?
2nd messengers cause vesicles containing GLUT4 transporters to be inserted into plasma membranes
How is the pituitary gland split?
anterior and posterior lobes
Where is the pituitary gland?
hangs below hypothalamus by infundibulum
What is the anterior pituitary gland controlled by?
hypothalamus
What does the posterior pituitary gland do?
stores and releases hormones made in hypothalamus
- Anti-diuretic hormone (vasopressin)
- oxytocin
What is antidiuretic hormone?
promotes H2O conservation by kidneys
What does oxytocin do?
stimulates contractions of uterus during parturition and contractions of mammary gland alveoli for milk-ejection reflex
What produces ADH?
supraoptic nuclei of hypothalamus
What produces oxytocin?
paraventricular nuclei
How is ADH and oxytocin sent to the posterior pituitary gland?
through the hypothalamohypophyseal tract
What is the release of ADH and oxytocin controlled by?
neuroendocrine reflexes
What does the anterior pituitary gland do?
secretes 6 trophic hormones that main size of targets
- high blood levels cause target to hypertrophy
- low blood levels cause atrophy
What are the 6 hormones released by the anterior pituitary? What are their functions?
1) growth hormone (GH): promotes growth, protein synthesis, and movement of amino acids into cells
2) thyroid stimulating hormone (TSH): stimulates thyroid to produce and secrete T4 and T3
3) adrenocorticotropic hormone (ACTH): stimulates adrenal cortex to secrete cortisol and aldosterone
4) follicle stimulating hormone (FSH): stimulates growth of ovarian follicles and sperm production
5) luteinizing hormone (LH): causes ovulation and secretion of testosterone in testes
6) Prolactin (PRL): stimulates milk production by mammary glands
What is the release of the anterior pituitary hormones controlled by?
hypothalamic releasing and inhibiting factors
- feedback from levels of target gland hormones
What is the path of movement for releasing and inhibiting hormones of the anterior pituitary?
- axon endings into capillary bed in median eminence
- carried by hypothalamohypophyseal portal system to another capillary bed
- diffuses into anterior pituitary and regulate secretion of its hormones
What is the feedback control of anterior pituitary?
- short feedback loop so retrograde flow of blood and hormones from anterior pituitary to hypothalamus inhibits secretion of releasing hormone
- negative feedback of target gland hormones
What hormone works during mentrual cycle?
estrogen stimulates LH surge by positive feedback
Where does the hypothalamus receive input from?
higher brain centers that can affect anterior pituitary secretion
Where are the adrenal glands?
on top of the kidneys
What are the components of the adrenal glands?
outer cortex and inner medulla
What does the adrenal medulla make? What is it controlled by?
makes and secretes 80% epinephrine and 20% norepinephrine
- controlled by sympathetic nervous system
Which hormonal effects last longer?
epinephrine
What is the adrenal medulla innervated by? When is it activated?
innervated by preganglionic sympathetic fibers
- activated during fight or flight response
What does the adrenal medulla cause?
- increased respiratory rate
- increased HR and cardiac output
- general vasoconstriction to increase venous return
- glycogenolysis and lipolysis
What is secreted by the zona glomerulosa?
mineralocorticoids
What is secreted by the zona fasciculata?
glucocorticoids
What is secreted by the zone reticularis?
sex steroids
What is controlled by ACTH?
adrenal cortex
What does the adrenal cortex secrete? What does each do?
- cortisol: inhibits glucose utilization and stimulates gluconeogenesis
- aldosterone: stimulates kidneys to reabsorb Na+ and secrete K+
- sex steroids for supplement
Where is the thyroid gland?
below the larynx
What does the thyroid gland secrete?
T4 and T3
What does the thyroid gland consist of?
thyroid follicles
- outer layer: follicle cells that synthesize T4
- interior: colloid (protein-rich fluid)
What is the role of iodide (I-) in the blood?
transported into follicles and secreted into colloid
- then oxidized to iodine (I2) and attached to tyrosine of thyroglobulin
What is thyroglobulin?
large storage molecule for T4 and T3
What does TSH stimulate?
hydrolysis of T4 and T4 from thyroglobulin and then secretion
How does goiter occur?
absence of sufficient dietary iodide = T4 and T3 can’t be made and levels are low
- low T4 and T3 don’t provide negative feedback and TSH levels go out
- causes thyroid gland to grow (goiter)
What does parathyroid hormone act on? What effect does that have? What is release of the hormone stimulated by?
acts on bones, kidney, intestines to increase blood Ca++ levels
- release stimulated by decreased blood Ca++
What are the islets of langerhans? What does it contain?
scattered clusters of endocrine cells in pancreas
- alpha and beta cells
What do the alpha cells secrete? Why?
glucagon in response to low blood glucose
- stimulates glycogenolysis and lipolysis
- increases blood glucose
What do the beta cells secrete? Why?
insulin in response to high blood glucose
- promotes entry of glucose into cells
- conversion of glucose into glycogen and fat
- decreases blood glucose
