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Flashcards in Endocrine System Deck (57)
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1
Q

Polypeptide Hormones

A

made in secretory pathway (by ribosomes on the rough ER and modified in Golgi), stored in secretory vesicles, released by exocytosis in response to specific signals (cleaved to activate) release is Ca2+ dependent and based on SNARE complex
ex: glucagon and insulin

2
Q

Steroid Hormones

A

derived from cholesterol, products of gonads, adrenal cortex and placenta, lipid soluble not water soluble, reversibly associated with carrier proteins to travel in the blood stream, diffuse directly out of the cell where they are synthesized instead of being stored (can diffuse across membrane because they are lipid soluble)

3
Q

Adrenal Cortex Hormones

A

all hormones produced are modified cholesterol
5 different hormones: dehydroepiandrostrone, androstenedione, cortisol, corticosterone, aldosterone
adrenal hormone production controlled by the anterior pituitary
hormone intermediates shuttled between mitochondria and smooth ER (can’t store steroids)

4
Q

Gonad Hormones

A

testosterone and estradiol, cholesterol is precursor, requires activity of aromatase for synthesis of estrogens

5
Q

Estrogens

A

have an aromatic ring, all female sex hormones, aromatase makes aromatic ring

6
Q

Aromatase Inhibitors

A

used to treat estrogen-dependent ovarian and breast cancers especially if cancer is estrogen responsive, letrozole

7
Q

Endocrine Disrupters

A

have aromatic rings, are usually pollutants that mimic estrogen and bind and activate the estrogen receptor which causes cancer, tumors and development issues
Estradiol, Diethylstilbestrol, DDT, PCB, BPA (in plastic baby bottles), Nonylphenol

8
Q

Serum Binding Proteins

A

act as reversible carriers for steroid in the blood, allowing the amount carried by the blood to be higher than it otherwise would, these proteins have a pocket where the hormone sits with the polar part of the steroid facing outwards, only free form of steroid can diffuse out of the blood capillaries and into the target cell so must unbind to the protein, only free steroids are active

9
Q

Anabolic-androgenic steroids

A
anabolic=build up
androgenic=masculine
mimic testosterone (synthetic testosterone agonists) and increase lean muscle mass with exercise and good diet
10
Q

Amine Hormones

A

Derived from tyrosine
Thyroid Hormones: Thyroxine (T4), T3, water insoluble and bind to nuclear receptors, only molecules in the body that contain Iodine
Catecholamines: Norepinephrine, epinephrine (also function as neurotransmitters), dopamine, water soluble and bind cell surface receptors, released by sympathetic neurons

11
Q

Hormone Receptors

A

all receptors are large protein molecules
polypeptide and catecholamine hormones bind to cell surface receptors
hormones change the properties of cells by acting to modify functional proteins like metabolic enzymes
some hormones directly modify existing functional proteins (act on preexisting cell materials and machinery, turn them on/off) which has a quick response ex: glucagon and insulin
some hormones stimulate new functional proteins to be synthesized which has a slower response (hormone enters the cell to activate synthesis, receptor is inside cell)

12
Q

Properties a Hormone/ Cell Interaction Must Have

A

High affinity: hormone concentrations are low so receptor must have a high affinity for it (physiological hormone concentrations are around 50% receptors bound) small change in hormone concentration results in a big change in receptor occupancy
High Specificity: Receptors are able to distinguish between hormones that are chemically similar since they were synthesized from the same molecule

13
Q

Cell Surface Receptors

A

Water soluble hormones bind, hormones are only switches to turn on pre-programmed responses within target cells
cell surface receptors generate a seconds messenger that acts in the cytoplasm of the responding cell, signal from hormone can be amplified due to this messaging system (chain of activation makes signal stronger, activation of one receptor can activate many more molecules
ex: fast hormonal response of glucagon
glucagon acts through a g-protein coupled receptor to activate adenylyl cyclase

14
Q

Protein Kinase A

A

acts to phosphorylate a number of enzymes in liver cells to activate (glycogen phosphorylase and glycogen synthase)

15
Q

Insulin Signaling

A

Insulin binds to receptor (Tyrosine kinase that starts a phosphorylation cascade) to cause cells to take up glucose from the blood, increase glucose uptake by moving Glut transporters to the surface
Glut 4: cause intracellular vesicles to fuse with the plasma membrane so the Glut4 is on the membrane and glucose can diffuse into the cell

16
Q

Nuclear Receptors

A

Steroid Hormones activate: slow hormonal response
stimulate new transcription
ex: egg production

17
Q

Egg production

A

estrogen (only in females) regulates ovalbumin
estrogen diffuses into nucleus of oviduct cell to activate estrogen receptor that sits on promotor of a gene so that RNA polymerase can transcribe the ovalbumin gene
if there is no estrogen present (in males) then no transcription occurs

18
Q

Clearing of Hormones in the ECF

A

hormones can not build up in the ECF
excreted in urine or feces (liver, kidneys)
inactivated by metabolism/enzymes

19
Q

Insulin

A

half life is about 4 mins in blood
must be degraded so that blood glucose levels don’t drop too low (can cause coma)
won’t be degraded as long as it’s bound to a carrier protein in the blood (inactive) and can remain inactive in blood for hours/days

20
Q

Pituitary Gland

A

Hypothalamus stimulates with hormones (anterior pituitary) or with direct neuronal stimulation (posterior pituitary)
two components: posterior (extension of the hypothalamus, contains terminals of neurosecretory neurons) and anterior (not neural tissue, collection of endocrine cells that are regulated by the hypothalamus)

21
Q

Hypothalamus

A

most important brain center for regulating homeostasis, has about 12 different nuclei with distinct functions (anterior hypothalamic nucleus - thermoregulation, lateral nucleus - thirst and hunger)
out put can be neural or hormonal
receives photoperiod, olfactory, heart, stomach, reproductive tract and hormonal stimulation
controls hunger, body temp, thirst, osmolarity, reproduction, lactation, metabolic rates, circadian cycles, fatigue, and anger
connected to the pituitary by the infundibulum

22
Q

Anterior Pituitary

A

stimulated by hypothalamic hormones, hypophysiotropic hormone causes anterior pituitary to release pituitary hormone
FSH, LH(gonadotrophs distinct cell types within the ant. pit. make the different hormones), Growth hormone(somatotrophs), TSH(Thyrotrophs), Prolactin(lactotrophs), ACTH(corticotrophs)
*tropic hormones: stimulate other tissues/endocrine glands to make other hormones
all polypeptide hormones

23
Q

Posterior Pituitary

A
extension of hypothalamus
releases vasopressin (supraoptic nucleus, antidiuretic hormone)  and oxytocin (paraventricular nucleus) products of neurosecretory cells
24
Q

Vasopressin

A

Antidiuretic Hormone ADH
9 amino acids
regulates contraction of blood vessels through their associated smooth muscle to control blood pressure, acts on kidney to regulate water retention by changing water permeability - aquaporins, this regulates ECF colume and composition

25
Q

Oxytocin

A

9 amino acid (only 2 aa difference from vasopressin)
targets mammary gland: acts on smooth muscle to cause milk ejection (myoepithelial sacks contract to squeeze milk out of ducts), suckling causes post pit. stimulation to release oxytocin (let down reflex)
targets uterus: causes uterine contraction during birth (increase stretching of uterus increases oxytocin release which causes a contraction that stretches the uterus)
oxytocin secreting neurons can synapse on other neurons in the brain to act on behavior (evokes maternal behavior, social bonding, feelings of calm and contentment with mate, MDMA “ecstasy” causes a robust increase of oxytocin and causes prosocial feelings)

26
Q

Pituitary Disorders

A

pituitary tumors: most are benign but can produce excessive amounts of a specific pituitary hormone or compress surrounding tissues and crowd out the production of other hormones, pressure can cause headaches and visual disturbances
Growth Hormone Deficiency: delayed growth, short
Hypopituitarism: general decrease in pituitary hormone production
Hyperprolactinemia: tumor stimulating/preventing prolactin production, causes galactorrhea, amenorrhea and decrease sex drive in men
Empty Sella Syndrome: sella surrounds pituitary, can increase in size and put pressure on pituitary sometimes leading to hypopituitarism

27
Q

Thyroid

A

bilobe structure in neck
absence of thyroid hormones is not lethal but has consequenses
regulates BMR (basal metabolic rate: at rest with no energy used for digestion)
all cells of the body are targets for thyroid hormones (T3 and T4: steroid hormones so need carrier protein for transport in blood)

28
Q

Metabolism

A

in most tissues TH increases metabolic rate, due to increased o2 consumption and ATP hydrolysis, stimulates activity of ATPase, decreases ATP concentration which stimulates glycolysis and creates heat

29
Q

Lipid Metabolism

A

T3 and T4 stimulate fat mobilization, increase fatty acid concentration in blood and activate their oxidation in many tissues

30
Q

Carbohydrate Metabolism

A

stimulate all aspects, enhance insulin dependent entry of glucose entry into the cell and gluconeogenesis (make new) and glycogen breakdown to increase blood glucose concentrations, provides energy to maintain a high metabolic rate

31
Q

ATP generation: Carbs

A

carbs stored as glycogen (liver and muscles)which can be broken down into glucose and used for glycolysis to make 2 pyruvate to make AcetylCoA which can then go into the Kreb cycle. Produce mostly NADH and FADH2. oxidative phosphorylation creates ATP from these. need oxygen
stimulated by TH

32
Q

ATP generation: protein

A

proteins into amino acids, the ammonia group is removed and secreted as urea, the carbon skeleton can be converted into pyruvate or a kreb cycle intermediate depending on the amino acid

33
Q

ATP generation: Fat

A

stored as triglycerides, broken down into glycerol and free fatty acids. glycerol goes into glycolysis and the fatty acids are broken down into AcetylCoA
stimulated by TH

34
Q

Growth

A

TH necessary for growth and development
when tadpoles do not have TH they do not turn into frogs
important in mammals for fetal and neonatal brain, formation of axon terminals, etc

35
Q

Other Effects of TH

A

cardiovascular system: increase heart rate
CNS: alterations in mental state
too little: mentally sluggish
too much: anxious

36
Q

TH Regulation

A

hypothalamus (receives signal: genetic set point for how much TH should be in the body) stress (body temperature) can cause changes in these levels. Releases thyrotropin into the portal blood vessel into the ant pit to stimulates to release TSH (thyroid stimulating hormone) which is circulated in the body and activates the thyroid gland to produce T3 and T4 which then circulate in the blood stream.
T3 and T4 have negative feedback on ant pit and hypothalamus causes them to stop secreting hormone

37
Q

TSH (Thyroid stimulating hormone)

A

stimulates T3 and T4 production and release from the thyroid and stimulate iodide uptake and growth of the thyroid (increase DNA replication, and cell division) results in hypertrophy (goiters)

38
Q

T4: Thyroxine

A

amine hormones from tyrosine, 4 iodine molecules

90% of circulating TH

39
Q

T3: Tri-iodothyronine

A

only 10% of TH but more biologically active, receptors have a higher affinity for this hormone than T4, deiodinase converts T4 into T3, cells control exposure to T3 through this enzyme

40
Q

TH synthesis

A

follicles filled with colloid in lumen acts as reservoir for TH, surrounded by follicle cells involved in almost all phases of TH production and secretion
colloid stores iodinated thyroglobulin and provide for synthesis for weeks

41
Q

Thyroglobulin

A

produced in follicle cells and has many tyrosine residues which are the starting materials for T3 and T4, one can giver rise to 4-6 T4 molecules, thyroidperoxidase enzyme oxidized iodide and stick it onto the tyrosine molecules (mono or di-iodotyrosine) cleave off and stick it onto a DIT (2 DIT= T4, 1MIT and 1DIT= T3) thyroglobulin is degraded when signaled so that they can be released, enzyme is endocytosed into the follicle cell and fuses with a lysosome to cleave off all the T3 and T4

42
Q

Iodide

A

uses secondary active transport with Na to go into the colloid, both flow into the cell and then Na is actively transported out

43
Q

Hypothyroidism

A

lethargic, weight gain (not hydrolyzing ATP), mentally slow and cold
if young causes cretinism (low mental development)
caused by low iodine intake (rare in US because salt is iodized) treat with iodine or T4, autoimmune attack on follicle cells so cant produce TH, elevated TSH levels to compensate which stimulates thyroid cell and increases thyroid growth (goiters)
pituitary dysfunction (no TSH production to stimulate thyroid)

44
Q

Hyperthyroidism

A

elevated BMR, body temp, anxious, bulging eye
caused by thyroid/pituitary tumors and graves disease (antibody binds to TSH receptor and stimulates thyroid, can cause a goiter)

45
Q

Adrenal Gland

A

responses to stress, regulated by nervous and endocrine system, stress: homeostasis is upset, on top of kidneys one is triangular one is semi-lunar
outer part is cortex (3 layers: zona glomerulaosa: produces aldosterone, fasciculate: cortisol, and reticularis) and the inner part is the medulla (chromaphine cells release (nor)epinephrine)

46
Q

Sympathetic NS

A

(nor)epinephrine produced by the adrenal medulla (part of sympathetic NS, modified sympathetic ganglion, has a cell body but no axon), catecholamines water soluble, rapid response to stress

47
Q

Cortisol

A

steroid produced by adrenal cortex, long term response to stress

48
Q

Adrenal Medulla

A

part of sympathetic NS, autonomic NS pathway has a series of nerves, the first nerve is in the CNS(preganglionic nerve) to the postganglionic nerve (usually very close to spinal cord in the sympathetic NS) in sympathetic the ganglion are very close to the target organ
when stimulated releases NT to the target cell

49
Q

somatic vs autonomic NS

A

somatic: one long cell from CNS to target, NT is always acetylcholine and receptor is a nicotinic receptor, always excitatory
autonomic: pre/post ganglionic and they synapse at the ganglion, ganglion are close to target cells (smooth, cardiac muscles, gland cells and GI tract) NT is acetylcholine with a nicotinic receptor, but at the effector the receptor is muscarinic (regulated by G proteins), sympathetic NT is (nor)epinephrine with adrenergic receptors (direct innovation of organs and release of hormones from adrenal)

50
Q

Receptors of Autonomic NS

A

parasympathetic: muscarinic
sympathetic: adrenergic receptors (alpha and beta two types of each)
alpha has greater affinity for norepinephrine, 1:on most sympathetic targets, 2: in GI tract
beta has greater affinity for epinephrine, 1: heart, kindney 2: some blood vessels and smooth muscle

51
Q

Stress response (short term)

A

sympathetic response: directly innovates heart (increase heart rate) and adrenal medulla (synapse on chromaphin cells to secrete hormones) and heart is also bathed in hormones to increase rate, duel response for quick response, breathing quickens to increase blood to heart, less blood to skin and digestive organs

52
Q

(nor)epinephrine

A

make resources available for physical exersion, fight or flight, chromaphin cells release, heart rate increases, blood flow increases to heart and skeletal muscle, liver skin GI and kidneys get less blood, free up stored energy resources: release glucagon to increase blood glucose levels not for fat storage but for muscles, glycogen broken down (produces lactate and broken down in liver)

53
Q

Cortisol

A

slow response to stress, produced by adrenal cortex, very little short term change, controls metabolism (creates fuel for glyconeogenesis, maintains glycogen levels in body) and immune system (anti-inflammatory and anti-immune responses) (produced all the time because it has other functions)
other hormones function based on cortisol (insulin, glucagon and epinephrine) need presence of cortisol to have full effect (act permissively), prevents immune system from acting too strongly (helps prevent auto immune attack) too little=auto immune attack. too much=low immune response
regulates both catabolism (break down of molecules to make glucose) and anabolism (synthesis of complex molecules: glycogen) balances them, changes in stress level increases cortisol levels, regulated by the ant pit, hypothalamus secretes corticotrophin releasing hormone CRH, into portal blood vessels, into ant pit which releases adrenal corticotrophic hormone ACTH, to stimulate adrenal cortex to release cortisol, cortisol negatively inhibits hypo and ant pit
mobilizes energy resources, helps you survive during fasting period, increases amino acids in blood stream for tissue repair, highest levels in the morning and lowest at night (3-5hrs after going to sleep) diurnal cycle

54
Q

Insufficient Cortisol Levels

A

cortisol is essential for life, complete absence causes inability to regulate homeostasis
adrenal insufficiency main causes: primary something wrong with adrenal cortex (disease), secondary due to pituitary dysfunction (not enough ATCH)
adisons disease: hypoglycemia (not enough glucose in blood), poor resistance to stress

55
Q

Excessive Cortisol Levels

A
Cushing's disease
pituitary tumor (too much ACTH) or adrenal cortex tumor
cause too much break down of bones muscle and skin, hyperglycemia, poor immune function, fat redistribution to trunk face and neck
56
Q

Growth Hormone

A

linear growth controlled by ant pit, main target: bone growth
first 2 years and puberty are fastest growth period
(pituitary GH, thyroid, testosterone/estrogen, insulin-like growth factors 1 and 2, and insulin also affect growth)
191 amino acids

57
Q

Bones

A

are alive, ends: epiphysis, shaft, epiphyseal plates (growth restricted here, turned into bone in adults so cant grow any more)
chondrocytes make cartilage which can be turned into bone by depositing Ca phosphate into collagen matrix
osteoblasts convert cartilage into bone, once plates fuse growth stops