Mcat Biology 4

Front 1

exocrine glands

Back 1

- release enzymes to external environment through ducts
- sudoriferous (sweat) glands
- sebaceous (oil) glands
- mucous glands
- digestive glands
- e.g. pancreas releases digestive enzymes through pancreatic duct

Front 2

endocrine glands

Back 2

- release hormones directly into bodily fluids
- e.g. pancreas releases insulin & glucagon directly into blood

Front 3

How long can it take endocrine glands to produce their effects?

Back 3

anywhere from seconds to days

Front 4

What are the general effects of the endocrine system?

Back 4

(1) alter metabolic activities
(2) regulate growth & development
(3) guide reproduction

Front 5

What are the 3 basic types of hormones?

Back 5

(1) peptide
(2) steroid
(3) tyrosine derivatives

Front 6

peptide hormones (general characteristics)

Back 6

- derived from peptides
- large or small
- often include carbohydrate portions
- cannot diffuse through membrane (b/c they are proteins), so they bind to membrane receptors & act through a second messenger
- water-soluble, move freely through blood

Front 7

How are peptide hormones manufactured?

Back 7

- manufactured in rough ER, usually as preprohormone
- preprohormone cleaved in ER lumen to prohormone & transported to Golgi
- prohormone cleaved & sommetimes modified with carbohydrates in Golgi
- final hormone packaged by Golgi into secretory vesicle and released via exocytosis upon stimulation by another hormone or nervous signal

Front 8

In what ways can a membrane-bound receptor react to a peptide hormone binding?

Back 8

- act as ion channel & increase membrane permeability to specific ion
- activate or deactivate other intrinsic membrane proteins acting as ion channels
- activate intracellular second messenger (cAMP, CGMP, calmodulin) to activate/deactivate enzymes and/or ion channels and create cascade of chemical reactions to amplify effect of hormone

Front 9

list of peptide hormones & sources

Back 9

(1) anterior pituitary hormones
- FSH - LH - ACTH - hGH
- TSH - prolactin
(2) posterior pituitary hormones
- ADH - oxytocin
(3) parathyroid hormone
- PTH
(4) pancreatic hormones
- glucagon - insulin

Front 10

steroid hormones (general characteristics)

Back 10

- derived from/chemically similar to cholersterol
- formed from series of steps in smooth ER & mitochondria
- lipids, so require protein transport molecule to dissolve into bloodstream
- diffuse through cell membrane (lipid-soluble)
- combine with a receptor in cytosol of cell, which transports steroid to nucleus where it acts at transcription level
- typically increases certain membrane or cellular proteins w/in effector

Front 11

list of steroid hormones & sources

Back 11

(1) glucocorticoids & mineral corticoids of adrenal cortex
- cortisol - aldosterone
(2) gonadal hormones
- estrogen* - progesterone* - testosterone

*estrogen & progesterone also produced by placenta

Front 12

tyrosine derivatives (general characteristics)

Back 12

- formed by enzymes in cytosol or on rough ER
- lipid soluble & carried in blood by plasma protein carriers
- bind to receptors in nucleus
- high affinity to binding proteins in plasma/nucleus causes latent period in response & increases duration of effect
- increase transcription of many genes in almost all cells
- epinephrine/norepinephrine are water-soluble & dissolve in blood; bind to receptors on target tissue & act mainly through second messenger cAMP

Front 13

list of tyrosine derivatives & sources

Back 13

(1) thyroid hormones
- T3 (triiodothyronine, 3 iodine atoms)
- T4 (thyroxine, 4 iodine atoms)
(2) catecholamines from adrenal medulla
- epinephrine - norepinephrine

Front 14

negative feedback

Back 14

control point is conduct of effector, NOT concentration of hormone itself - so answer questions with how hormone RESPONDS!!!

[e.g. ADH holds water and increases blood pressure, so a question asking if a person with high blood pressure has high or low ADH should be answered with LOW ADH, since we are looking at how ADH output would respond to the body]

Front 15

hypothalamus

Back 15

controls release of anterior pituitary hormones with releasing & inhibitory hormones (controlled by nervous signals) carried to capillary bed of anterior pituitary by small blood vessels

Front 16

Where is the anterior pituitary located?

Back 16

in brain, beneath the hypothalamus; releases peptide hormones

Front 17

What are the 6 major hormones released by the anterior pituitary?

Back 17

[all peptide hormones]
(1) human growth hormone (hGH)
(2) adrenocorticotropin (ACTH)
(3) thyroid stimulating hormone (TSH)
(4) follicle-stimulating hormone (FSH)
(5) leutinizing hormone (LH)
(6) prolactin

Front 18

hGH

Back 18

- human growth hormone (somatotropin)
- peptide
- stimulates growth in almost all cells of the body
- increases mitotic episodes, cell size, protein synthesis, & use of fatty acids for energy
- mobilizes fat stores
- decreases use of glucose
- affects proteins by increasing amino acid transport across cell membrane, increasing translation & transcription & decreasing breakdown of proteins & amino acids

Front 19

ACTH

Back 19

- adrenocorticotropic hormone
- peptide
- stimulates adrenal cortex to release glucocorticoids via second messenger system using cAMP
- release stimulated by many types of stress

Front 20

glucocorticoids

Back 20

stress hormones

Front 21

TSH

Back 21

- thyroid-stimulating hormone (thyrotropin)
- peptide
- stimulates thyroid to release T3 and T4 via second messenger system using cAMP
- increases thyroid cell size, number & rate of T3/T4 secretion
- T3/T4 have negative feedback effect on TSH release at anterior pituitary & hypothalamus

Front 22

prolactin

Back 22

- peptide
- promotes lactation
- progesterone & estrogen inhibit milk production before birth
- hypothalamus mainly inhibits prolactin release, but suckling stimulates hypothalamus to stimulate anterior pituitary to release prolactin, which inhibits menstrual cycle

Front 23

posterior pituitary

Back 23

- "neurophypophysis"
- composed mainly of support tissue for nerve endings extending from hypothalamus
- releases oxytocin & ADH

Front 24

Where are oxytocin and ADH synthesized?

Back 24

neural cell bodies of hypothalamus (transported to posterior pituitary down axons)

Front 25

oxytocin

Back 25

- peptide hormone (small polypeptide)
- increases uterine contractions during pregnancy
- causes milk to be ejected from the breasts

Front 26

ADH

Back 26

- antidiuretic hormone (vasopressin)
- peptide hormone (small polypeptide)
- causes collecting ducts of kidney to become permeable to water, reducing amount of/concentrating urine
- increases blood pressure since fluid is reabsorbed
- coffee/alcohol block ADH & therefore increase urine volume

Front 27

adrenal glands

Back 27

- located on top of kidneys
- separated into adrenal cortex & adrenal medulla

Front 28

adrenal cortex

Back 28

- outside portion of adrenal gland
- only secretes steroid hormones (mineral corticoids & glucocorticoids)

***also secretes small amount of sex hormones, only significant in females***

Front 29

mineral corticoids

Back 29

- affect electrolyte balance in blood stream
- aldosterone is major mineral corticoid

Front 30

glucocorticoids

Back 30

- increase blood glucose concentration
- have greater effect on fat & protein metabolism
- cortisol is major glucocorticoid

Front 31

aldosterone

Back 31

- steroid hormone
- mineral corticoid
- acts in distal convoluted tubule & collecting duct
- increases Na+ & Cl- reabsorption
- increases K+ & H+ secretion
- creates net gain in plasma particles, increasing BP
- same effect (to lesser extent) on sweat glands, salivary glands & intestines

Front 32

cortisol

Back 32

- steroid hormone
- glucocorticoid
- increases blood glucose by stimulating gluconeogenesis in liver
- degrades adipose tissue to fatty acids for cellular energy
- causes moderate decreases in glucose use by cells
- causes degradation of nonhepatic proteins, decreases of nonhepatic amino acids & increases liver/plasma proteins & amino acids
- stress hormone (anti-inflammatory properties, diminishes immune system capacity)

Front 33

gluconeogenesis

Back 33

creation of glucose & glycogen, mainly in liver, from amino acids, glycerol, and/or lactic acid

Front 34

catecholamines

Back 34

- tyrosine derivatives synthesized in adrenal medulla
- epinephrine & norepinephrine = vasoconstrictors of internal organs/skin, but vasodilators of skeletal muscle
- effects on target tissues last longer than effects in sympathetic NS
- stress hormones

Front 35

thyroid

Back 35

located along trachea in front of larynx; hormones include T3, T4 & calcitonin

Front 36

T3 & T4

Back 36

- T3 = triiodothyronine
- T4 = thyroxine
- lipid soluble tyrosine derivatives that diffuse through lipid bilayer
- act in nucleus of effector cells
- increase basal metabolic rate
- secretion regulated by TSH

Front 37

calcitonin

Back 37

- large peptide hormone released by thyroid gland
- slightly decreases blood calcium by decreasing osteoclast activity & number
- can still control calcium levels without it in humans

Front 38

pancreas

Back 38

- acts as both and endocrine & exocrine gland
- Islets of Langerhans
- releases peptide hormones insulin & glucagon into blood
- delta-cells release somatostatin

Front 39

somatostatin

Back 39

- released by delta-cells of pancreas
- inhibits both insulin & glucagon
- function may be to extend period of time over which nutrients are absorbed

Front 40

insulin

Back 40

- peptide hormone
- released by beta-cells of pancreas
- released during high blood levels of carbs/proteins
- affects carb, fat & protein metabolism
- causes carbs to be stored as glycogen in liver & muscles, fat to be stored in adipose tissue & amino acids to be taken up by cells and made into proteins
- binds to membrane receptor & starts reaction cascade, causing cells t o become highly permeable to glucose (except for neurons in brain & a few other cells)
- insulin receptor not a glucose carrier itself
- also increases membrane permeability to amino acids
- activates intracellular metabolic enzymes
- affects transcription & translation rates
- NET EFFECT: lower blood glucose levels

Front 41

glucagon

Back 41

- peptide hormone
- released by alpha-cells of pancreas
- essentially opposite effects to insulin
- stimulates glycogenolysis & gluconeogensis in liver
- acts via second messenger system of cAMP
- breaks down adipose tissue in higher concentrations (increases fatty acid level in blood)
- NET EFFECT: raise blood glucose levels

Front 42

parathyroid glands

Back 42

- four small glands attached to back of thyroid
- release parathyroid hormone

Front 43

PTH

Back 43

- parathyroid hormone
- peptide hormone
- increases blood calcium
- increases osteocyte absorption of calcium & phosphate from the bone
- stimulates osteoclast proliferation
- increases renal calcium reabsorption & renal phosphate excretion
- increases calcium phosphate uptake from gut by increasing renal production of a steroid derived from vitamin D
- secretion regulated by calcium ion plasma concentration (parathyroid glands shrink/grow accordingly)