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Chapter 11 - Endocrine Glands
Fox, Chapter 11
60
Physiology
Professional
04/15/2012

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Term
endocrine glands (characteristics)
Definition
1. ductless
2. secrete hormones into the blood
3. organs secrete hormones too
Term
4 chemical classifications of hormones
Definition
1. amines
2. polypeptides and proteins
3. glycoproteins
4. steroids
Term
polypeptides and proteins
Definition
1. hormone
examples: antidiuretic hormone, insulin, growth hormone
Term
amines
Definition
1. derived from tryosine and tryptophan
examples: hormones from the adrenal medulla, thyroid and pineal glands
Term
glycoproteins
Definition
1. long polypeptides bound to a carbohydrate
examples: follicle-stimulating and luteinizing hormones
Term
steroids
Definition
1. lipids derived from cholesterol
2. secreted by adrenal cortex and gonads
examples: testosterone, estradiol, progresterone, cortisol
Term
2 hormone classifications
Definition
1. polar hormones
2. nonpolar hormones
Term
polar hormones
Definition
1. water soluble
2. cannot pass through plasma membranes
3. injected if used as a drug
Term
nonpolar hormones
Definition
1. insoluble in water
2. can enter target cells directly
3. often called lipophilic hormones
4. include steroids and thyroid hormone
5. can be taken orally in pill form
Term
prohormones
Definition
1. made before the hormone
2. inactive hormones that must be cut and spliced together to be active
Term
prehormones
Definition
1. made before the hormone
2. inactive hormones that must be modified within their target cells
Term
hormones vs. neurotransmitters
Definition
1. both interact with specific receptors
2. binding to a receptor causes a change within a cell
Term
hormone interactions (3 aspects)
Definition
1. a target cell is responsive to several different hormones
2. hormones may be antagonistic, synergistic or permissive
3. how a cell responds depends on the amount of hormone and the combination of all hormones
Term
synergistic effects
Definition
1. two or more hormones work together to produce a particular effect
2. can be "additive" or "complementary"
Term
permissive effects
Definition
1. one hormone makes the target cell more responsive to a second hormone
(estrogen and progresterone in the uterus)
Term
antagonistic effects
Definition
1. hormones work in opposite directions
(insulin stimulates fat storage; glucagon stimulates fat breakdown)
Term
hormone half-life
Definition
1. ranges from minutes to hours
2. removed from the blood by the liver
(thyroid hormone circulates for several days)
Term
up-regulation of hormones
(priming effects)
Definition
1. target cells increase the number of receptors it has for a hormone
2. makes it more sensitive to subsequent hormone release
Term
down-regulation of hormones
(desensitization)
Definition
1. prolonged exposure to high concentrations of hormone may result in decreased number of receptors for that hormone
2. many hormones are released in spurts to avoid desensitization = called PULSATILE SECRETION
Term
hormones and receptors
Definition
1. bind to receptors ON or IN target cells
2. highly specific binding
3. hormones bind to receptors with a high affinity
4. hormones bind to receptors with a low capacity
Term
steroid hormone action
Definition
1. activate genetic transcription by serving as transcription factors
2. produce new proteins (enzymes) that change the metabolism inside the cell
3. after binding, they translocate to the nucleus and bind to DNA
Term
thyroid hormone action
Definition
1. thyroxine travels to target cells on thyroxine-binding globulin (TBG)
2. inside the target cell, it's converted to T3
3. receptor proteins are located inside the nucleus bound to DNA
Term
coactivators and corepressors
Definition
1. molecules are needed in addition to the steroid hormone
2. they bind to the nuclear receptor proteins at specific regions
3. this changes the effect of a given hormone in different cells
Term
hormones that use 2nd messengers
Definition
1. can't cross the plasma membrane, so they bind to receptors on the cell surface
(epinephrine, norepinephrine, insulin)
Term
2nd messenger: Adenylate Cyclase/cAMP
Definition
1. used by epinephrine and norepinephrine
Term
2nd messenger: Phospholipase C
Definition
1. used by epinephrine
Term
2nd messenger: Tyrosine Kinase
Definition
1. used by insulin
2. the receptor is also the enzyme tyrosine kinase (ligand-binding site on cell)
3. enzyme activated by phosphorylation
Term
pituitary gland
Definition
1. attached to the hypothalamus
2. divided into anterior and posterior lobe
Term
pituitary hormones
Definition
1. secreted by anterior lobe
2. trophic hormones stimulate hormone secretion in other glands
Term
hormones in other glands affected by pituitary hormone secretion
Definition
1. growth hormone (GH)
2. thyroid-stimulating hormone (TSH)
3. adenocorticotropic hormone (ACTH)
4. follicile-stimulating hormone (FSH)
5. lutenizing hormone (LH)
6. prolactin (PRL)
Term
posterior pituitary
Definition
1. stores and releases two hormones:
ADH - promotes water retention in kidneys
Oxytocin - stimulates contractions in childbirth
Term
adrenal glands
Definition
1. atop the kidneys
2. outer adrenal cortex and inner adrenal medulla
Term
adrenal medulla
Definition
1. secretes epinephrine and norepinephrine in response to neural stimulation from hypothalamus
Term
adrenal cortex
Definition
1. secretes steroid hormones in response to ACTH
Term
corticosteroids
Definition
1. made from cholesterol
2. three categories: mineralocorticoids, glucocorticoids, sex steroids
Term
mineralocorticoids
Definition
regulate Na+ and K+ balance
Term
glucocorticoids
Definition
regulate glucose metabolism (cortisol)
Term
sex steroids
Definition
weak androgens that supplement those made in the gonads
Term
stress and the adrenal gland
Definition
1. stress increases secretion of ACTH, which results in increased glucocorticoid release
2. "general adaptation syndrome"
Term
cortisol
Definition
1. helps inhibit the immune system so that it does not overrespond
2. acts on higher brain regions; contributes to depression and anxiety
Term
general adaptation syndrome
Definition
3 stages: alarm, resistance, exhaustion
Term
thyroid gland
Definition
1. cube shaped, one layer
Term
thyroid hormone production
Definition
1. thyroglobulin is made by follicular cells
Term
thyroid hormone function
Definition
1. stimulates protein synthesis
2. promotes maturation of the nervous system
3. increases rates of cellular respiration
4. elevates basal metabolic rate
Term
calcitonin
Definition
1. made by parafollicular cells
2. inhibits dissolution of bone calcium
3. stimulates calcium excretion in the kidneys to lower blood calcium levels
Term
hypothyroidism
Definition
1. low metabolic rates
2. weight gain and lethargy
3. poor adaptation to cold stress
4. myxedema (fluid accumulation)
Term
iodine deficiency
Definition
1. overstimulation of thyroid gland
2. goiter
Term
thyroid vs. parathyroid
Definition
thyroid: decreases calcium
parathyroid: increases calcium
Term
pancreas
Definition
1. endocrine and exocrine gland
2. endocrine cells are in Islets of Langerhans
3. exocrine glands deal with digestion
Term
pancreas/endocrine cells
Definition
1. alpha cells: glucagon
2. beta cells: insulin
Term
insulin
Definition
1. takes glucose out of the blood
2. purpose is to lower blood glucose levels to the normal range
3. secreted by beta cells when glucose levels rise after sugary meals
Term
insulin action
Definition
1. binds to receptors on target cells
2. indirectly stimulates the enzyme glycogen synthase in the liver and skeletal muscles to promote sugar storage
3. stimulates adipose tissue to store fat
Term
glucagon
Definition
1. antagonistic to insulin
2. secreted by alpha cells when glucose is low
3. raises blood glucose levels to normal
Term
glucagon action
Definition
1. stimulates gluconeogenesis (noncarbs to glucose)
2. stimuluates lipolysis in adipose tissue (fat is released and used instead of glucose)
3. stimulates liver to hydrolyze glucagon into glucose and release it into the blood
Term
pineal gland
Definition
1. located on roof of third ventricle in the brain
2. secretes the hormone melatonin (circadian rhythms)
3. regulated by the hypothalamus (stimulates melatonin production when it gets dark)
Term
autocrine vs. paracrine signals
Definition
1. both involved in short-range signaling between neighboring cells within an organ
Term
autocrine signals
Definition
1. sender and receiver are the same cell type
2. regulatory molecules are called CYTOKINES or growth factors
3. most control gene expression in the target cell
Term
paracrine signals
Definition
1. sender and receiver are different cell types/tissues
Term
prostoglandins
Definition
1. group of autocrine regulators
2. made from arachidonic acid released from phospholipids in the plasma membrane
3. released from almost every cell
4. wide range of function
Term
prostoglandin functions
Definition
1. immune system: promote inflammation
2. reproductive system: aid ovulation
3. digestive system: inhibit secretion, stimulate absorption
4. respiratory system: aid bronchoconstriction and dilation
5. circulation: vasoconstriction, dialation, blood clotting
6. urinary system: increase blood flow to the kidneys
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