2Exam Flashcards
The endocrine has a major influence on maintaining homeostatsis by modifying metabolic activity through:
- reproduction
- growth and dev.
- electrolyte, water, nutrient balance
- regulation of cellular metabolism and energy balance
- mobilization of body defenses
endocrine organs
- thyroid gland
- parathyroid gland
- thymus gland
- pancreas
- ovaries
- testes
define hormone:
carried by bloodstream*
chemical compound secreated by endocrine glands through blood, broadcast to diverse cells and tissues
gland classification
- endocrine gland: release hormones into blood
- exocrine gland: releases compounds (not hormones) into ducts.
biogenic hormone
water soluble (except thyroid)
derived from amino acid that is modified
made in advance
ex. norepinephrine
Protein Hormone
water soluble, consists of amino acid chains, made in advance
ex. parathyroid hormone
three subgroups of protein hormone
- polypeptides
- olgiopeptides
- glycoproteins
steriod hormone
lipid soluble
formed from cholesterol
produced by gonads and adrenal cortex,
synthesized on demand
ex. cortisol
agonist
a chemical that binds a receptor and initiates a biological response
antagonist
a chemical that binds a receptor and inhibits a biological response
affinity
how tightly a ligand (hormone) binds to a protein (receptor)
efficacy
the relative ability of a drug-receptor complex to produce a functional response
Half life
the time it takes for a chemical to be removed or deactivated by the body
hormone receptors are either bound to ____ or ____
- plasma membrane bound receptors
- intracellular receptors
plasma membrane receptors
g protein coupled receptors (GPCRs)
receptors:
tyrosine kinases
cytokine
intracellular receptors
steroid like receptors
g-protein coupled receptor (GPCR’s)
bound to plasma membrane and allow for signal amplification
signal amplification: allow a small signal to have a large effect
Cyclic AMP (cAMP):
the most common G-protein- mediated signaling cascade-
Steps: hormone (1st messenger) binds to receptor, receptor activates G protein, g protein activates adenylate cyclase, adenylate cyclase converts ATP to cAMP (2nd messenger), cAMP activates protein kinases.
stimulation of a single receptor can lead to formation of millions of response molecules
amplification in G-protein/ cyclic AMP signaling
g-proteins can activate different signaling mechanisms, activating or inhibiting cellular activity. steps:
- signal molecule binds to G protein-coupled receptor (GPCR) which activates G protein
- g protein turns to adenylyl cyclase (amplifier enzyme)
- adenlyly cyclae converts ATP to cyclic AMP
- cAMP activates protein kinase A
- protein kinase A phosphorylates other proteins, leading ultimately to a cellular response.
many types of g-proteins can bind to receptors and initiate different signaling cascades
different signaling cascades utilize different second messengers
this is BIOGENIC AMINES and PEPTIDE HORMONES
hydrophobic hormone
act via intracellular receptors and direct gene activation
acts a transcription factor.
1. steps diffuses through the plasma membrane and binds to intracellular receptor
2. receptor-hormone complex enters the nucleus
3. the receptor hormone complex binds a specific DNA region
4. binding initiates transcription of the gene to mRNA
5. mRNA directs protein synthesis
(structural and exported proteins)
three types of stimuli can cause hormone secretion
- humoral
- neural
- hormonal
Humoral Stimulus
hormone release caused by altered levels of certain critical ions or nutrients
stimulus: low concentration of CA2+ in capillary bed
response: parathyroid glands secrete parathyroid hormone (PTH) which increases blood CA2+
neural stimulus
hormone released by neural imput
stimulus: action potentia pregang. symp- adrenal med.
response: adrenal medulla cells secret epinephrine and norepinephrine
hormonal stimulus
hormone release caused by another hormone (tropic hormone)
stimulus: hormones from hypothalamus
response: anterior pituitary secrets hormones- other endocrine organs release more hormones.
paraventricular nucleus (PVN)
one of most important for autonomic control
supraoptic nucleus
the peptide hormone vasopressin, also known as antidiuretic hormone (ADH) and oxytocin
infundibulum
pituitary stalk: connects hypothalamus and pituitary gland
anterior pituitary cells
endocrine gland cells
Adenohypophysis
posterior pituitary cells
mostly axons/terminals
neurohypophysis
how the hypathamus controls release of hormones from posterior pituitary gland
neuroendocrine cells:
1. hyp. neurons sythesize oxytocin or antidiuretic hormone (ADH)
2. oxytocin and ADH are transported down the axons of the hypthalamic-hypophyseal tract of posterior pituitary gland
3. oxytocin and ADH are stored in axon terminals in the posterior pituitary
4.** when associated hypothalamic neurons fire action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.**
how the hyp. controls hormone realease from anterior pituitary gland:
hypthalamic-hypophyseal portal system
1. hyp neurons secrete releasing and inhibit hormones into capillary bed
2. hormones travel through portal veins in the infundibulum
3. hyp. hormones exit that anterior pituitary capillary bed to bind into receptors on anterior pituitary cells
5. hyp hormones stimulate or inhibit secretion of hormones from the anterior pituitary cells.
Hormones released by hypathalmus
- hypothalamus
releasing hormones TRH, PRH, gnRH, CRH, GHRH
inhibiting hormone: PIH, GIH - posterior pitu: vasopressin, oxytocin
- anterior pituitary - - TSH Thyroid stimulating hormone
- PRL Prolactin: mammary gland
- FSH & LH follicle stimulating hormone & leutinizingL gonazed and testes to spark gamete growth
- GH growth hormone: muscle tissue
5.ACTH Adrenocorticotropic hormone: adrenal gland (cortisol release)
target gland
hormone production activated by pitu.
hormones from target gland regulate target tissue and provide feedback to pitu &/or hypo.
chain of command
hypo (master CNS/setpoint) - pitu. - (master gland) - target gland - target cell
ultrashort feedback loop
hypothalamus- hypathalamus
ex. somatostatin release (stop GH)
short feedback loop
- pitu gland- hypo.
- target gland- pitu.
long feedback loop
target gland - hypo.
negative feedback loop
inhibits hypo and pitu - decreasing further release.
other feedback loops not involving hypo.
calcium metabolism
glucose metabolism
Compare and contrast hormones and neurotransmitters:
Both: signaling molecules that can be released by specific cells to influence the behavior of other cells.
Major difference: how they are released.
Hormones: released from endocrine glands directly into the systemic circulation
Neurotransmitters: only released by neurons at a synapse.
Different signaling influences how they affect target cells
Hormones: can effect any cell in the body that has a receptor to recognize that hormone
Global influence over cellular behavior
Neurotransmitters: can only bind and effect receptors that are located on the postsynaptic cell- limiting their effect to one cell.
Both needed for homeostasis.
What are the 3 major classes of hormones and what are their defining features?
Biogenic amines: water-soluble (cannot pass plasma membrane), amino acid derivatives, made in advance by cells that secrete them.
Ex. norepinephrine and thryoxin
Protein hormones: water-soluble, composed of amino acid chains, made in advance by cells that secrete them.
Size varies depending on length of chain.
Ex. parathyroid, insulin, glucagon
Steriod hormones:lipid soluble (can cross plasma membrane) cholesterol derivatives that are synthsized on demand
only adrenal cortex (cortisol, aldosterone) and gonads produce steriod hormone.
When a hormone is released how does it know what cells to interact with?
Hormones: released in blood supply and carried all over the body (endocrine fashion).
Hormones will only affect cells that express receptors for that hormone.
- Describe how second messengers life cAMP are able to amplify the cellular response to stimulation by a hormone
Water soluble hormones bind to the cell surface receptors, many coupled to G-proteins on the cytoplasmic side of membrane.
Activations of intermediary proteins can activate a cellular cascade: forming second messengers: activates or inhibits cellular activity.
One hormone activates its receptor, which activates a g protein.
G protein activates multiple adenylate cyclase enzymes which forms second messengers called AMP.
Can lead to the formation of a thousand cAMP messengers- alter activity of multiple enzymes in the cell- amplification at every stage of the process.
What are 3 types of stimuli for hormone secretion. Give examples of hormone that uses each stimulation
Three types of stimuli for hormonal secretion:
Humoral stimuli
Neuronal stimuli
Hormonal stimuli
Examples
Humoral stimuli: hormone release caused by a detected change in blood levels of ions or nutrients.
parathyroid hormone secretion in response to low calcium
Insulin release in response to high blood glucose levels
Aldosterone release in response to changing potassium levels
Neuronal stimuli: hormone is released in response to neuronal input.
Release of norepinephrine and epinephrine from the adrenal medulla during times of stress.
Hormonal stimulus: hormone release is triggered by the release of another hormone.
How many endocrine organs release their hormones
Trophic (releasing or inhibiting) hormones from hypothalamus which regulate secretion of anterior pituitary hormones.
Compare and contrast the long, short, and ultrashort feedback loops of the hypothalamus and pituitary gland?
Hypothalamus- pituitary axis (HPA axis) feedback loops are different from other loops: signal regulating the loop is the concentration of secreted hormone, not its effect on the target cells.
Negative feedback loops.
Long feedback: most common. Concentration or hormone release from the target tissue feeds back to they hypothalamus resulting in the decrease of hypothalic hormone released.
ex. Increased levels of t4- decreases release of thryrotropin releasing hormone (TRH) from hypo.
Short feedback loop: concentration of pituitary gland hormone feeds back to the hypothalamus, decreasing the release of hypothalamic hormone.
ex. Release of ACTH from the anterior pituitary inhibits the release of coricotrphin releasing hormone (CRH) from the hypathalmus
Ultra short feedback look: The concentration of the hypthalamic hormone inhibits its won further release in autocrine fashion:
ex. The release of growth hormone GHRH releasing it own release into the hypothalamus
. Describe the mechanism of hormonal release in the posterior and anterior pituitary gland.
The posterior pituitary gland neurophypophsis : tissue neuronal in origin.
Uses neuronal mechanisms
2 hypothalamic nuclei:
Paraventricular
Supraoptic nuclei
Send axons out of they hypothalamus and through the indundibulum. These neurons terminate in the posterior pituitary at a capillary bed. When paravtricular or spuroptic neurons fire an action potential, hormones that reside in synaptic vesicles in the axonal terminals are released into the capillary and out into systemic circulation
Which of the following is not an endocrine organ?
a. Anterior pituitary gland
b. Thyroid gland
c. Pancreas
d. Posterior pituitary gland
d. posterior pitu. gland
A hormone that bound to a G-protein coupled receptor and initiated a biological response would be classified an
a. Antagonist
b. Synergist
c. Agonist
d. Inverse agonist
c. agonist
The release of ACTH (adernocorticotropic hormone) from the anterior pituitary can inhibit the release of CRH (cortiotropic releasing hormone) from the hypathalamus. This is an example of what kind of feedback loop?
a. Positive feedback loop
b. Long feedback loop
c. Short feedback loop
d. Ultrashort feedback loop
c. short feedback loop
immediately after consuming a very salty meal you might expect to see an increase in what pitu. hormone?
a. oxytocin
b. antidiuretic hormone
c. thyroid releasing hormone
d. ACTH
b. Antidiuretic hormone
oxytocin stimulates activity in which cell type?
a. skeletal muscle cells
b. hepatocytes
c. smooth muscle cells
d. lactotrophs
c. smooth muscle cells
Which of the anterior pituitary cell hormone pair is correct?
a. gonadotroph: GnRH
b. Gonadotroph: LH/FSH
c. Somatotroph: Somatostatin
d. somatotroph: GRHR
b. gonadotroph: LH/FSH
what are the major triggers for ADH (antidiuretic)
3 major triggers:
1. low blood pressure
2. low blood volume
2. dehydration (high blood osmolarity)
main effect of ADH
within kidney collecting ducts
increase blood volume
increasing concentration of the urine
what are the main physiological effects of oxytocin?
activation of smooth muscle cells in mammory glands and uterus
(G-protein coupled)
regulation of growth hormone in the body
regulated by 2 hypo hormones:
1. GHRH : growth hormone releasing
hormone
2. GHIH: growth hormone inhibiting hormone
growth hormone is regulated by ___ negative feedback loops?
3 negative feedback loops:
1. long feedback loop: inibits GH secretion when the blood levels of insulin are increased.
2. short feedback: inhibits GH secretion when circulating levels of GH feedback to they hypothalamaus and increase release of GHIH
3. ultrashort: GH secretion when GHRH inhibits its own release
what are & are responsible for the indirect effects of growth hormone?
result of IGF firing (Insulin-like growth factors)
w/o gf you would not see igf. but effects of igf different from gh.
effects:
increased organ size and function
overall somatic cell growth
increased linear bone growth
increased lean muscle mass
what are the direct effects of growth hormone?
those mediated by growth hormone directly binding to target cell.
effects:
lipolysis
decreased glucose uptake
increased guluconeogenesis
increased IGF production
amino acide uptake
increased protein synthesisf
gigantism vs. acromegaly
both : from hypersecretion of growth hormone
difference: when they occur in development
gigantism: before epiphyseal plate close
acromegaly: after plates close (face, hands, feet)
major effects of prolactin, follicle stimulating hormone and LHS is males and females
prolactin: females: milk production
FSH is a gonadotrophin. females: ovarain follicle maturation. males: spermatogenesis. both develop gamete.
LH: gonadotrophin. females: promote maturation, triggers ovulation, and release of est. and progest. males: stimulate testosterone production
The hypo. acts as a master regulator defining many of the set points for homeostasis. where does it send / receive signals from?
receives from:
1. frontal lobe
2. limbic system
3. circulating hormones and signals
4. neural signals from sensory pathways
sends to:
1. pitu. gland (endocrine output)
2. brainstem and spinal cord centers
a. neural: automatic
b. neural: somatic
most organs are regulated by
the autonomic nervous system
autonomic pathways are part of the
motor system
how do the sympathetic and parasympathetic divisions of the ANS work together
- many organs receive both sympathetic and parasympathetic innervation: one turns up and one turns down : opposing functions.
- they work together to regu. organ function with the needs of the body: balance is what determines function
- together they maintain homeostasis.
preganglionic neuron
cell body in the CNS
it’s axon reaches from CNS to autonomic ganglion
connects to postganglionic neuron
postganglionic neuron
cell body in an autonomic ganglion
axon reaches through the body to a target organ
synapses on: smooth muscle, cardiac muscle, gland cells in the target organ
dual innervation:
most organs receive sympathetic and parasympathetic control.
smooth muscle, cardiac muscle, or gland cell in target organ
cells have different receptors for sympathetic and parasympathetic
smooth muscle, cardiac muscle, gland cell in target organ.
Parasympathetic nervous system
anatomically : craniosacral system
functionally: rest and digest system
(stores energy reserves, slows heart rate, housekeeping: empty bowel and bladder,
protection narrowing pupil and airways
neurochemistry of parasympathetic system:
an acetylcholine-based system (ACTH)
acetylcholine: neurotransmitter.
which neurons release?
pre and post ganglionic neurons of the parasymp.
cholinergic receptor
binds to a receptor for acetylcholine
types of acetylcholine receptors:
- nicotinic receptos: binds to nicotine
- muscarinic receptor
sympathetic nervous system:
anatomy: throacolumbar
functionally: fight or flight
(release of energy reserves
speeding heart rate
increasing strength of contraction
increase blood pressure
increase air flow to lungs
bronchodiliation
dilation of pupil
regulation of blood flow
Neurochemistry of the sympathetic system.
Acetylcholine and norepinephrine
1. pregang. neuron in symp. system releases acetylcholine
2. Ach binds to nictonic receptor
3. postgang releases norepinephrine
4. binds to adrenergic receptor
5. reaches target tissue
adrenegic receptors bind
both epinephrine and norepinephrene but have afffinities for the 2 (preferences)
fight of flight response from epinepherine:
epinepherine : hormone travels in blood, activates all sympathetic targets at once. adrenergic hormones are stimulated from this.
subtypes of adrenergic receptors:
- alpha 1: contraction of smooth muscle
- alpha 2: found on varicosities of sympathetic postganglionic neurons // negative feedback to inhibit further norepineph. release
- beta 1: found on cardiac muscle cells: S/A and AV nodes: contractile cells
- beta 2: usually causes relaxation of smooth muscle
sympathetic nervous system pathway
- Ach or nicotine stimulate nictonic type acetylcholine receptors at this synapse
- epinephrine / norepinephrine stimulate alpha or beta type adrenergic receptors on the target cell membrane.
parasympathetic nervous system pathway:
- Ach / nicotine stimulate nictonic acetycholine receptors
- bind to target cell with same receptors
if a cell receives both sympathetic and parasympathetic innervation (dual innervation)
what receptor must it have
must have receptors for both adrenergic and chollinergic receptors.
Agonist drug
binds to a receptor and creates the same response in the cell as the binding transmitter
antagonist drug (blocker)
binds to a receptor but does not create a response in the cell, blocks the action of transmitter by occupying the binding site.
drugs that affect ach pathways
- nicotine
- muscarine
- acetycholinesterase inhibitors
nicotine: agonist to nic. type. ach recep
stimulates both sympathetic and parasymp. pathways
activates skeletal muscles as well
muscarine: agonist at muscarinic type ach. recep
found in certain mushrooms
stimulates all muscarinic receptros at target ogans (all parasymp pathways plus sweat glands)
poisoning can be life threatening
effects:
exess. salivation
lacrimation
urination
sweating
intestinal
constricted pupil
slow heart rate
bronchoconstriction
Acetylcholinesterase inhibitors
any drug that inactivates acetylcholinesterase.
Ach stays active at the synapse longer
prolongs stimulation at both nictonic and muscarinic receptors
prolonged stimulation of skeletal muscle
clinical use: Alzheimer, parkinsons, neuromuscular
weaponized: pesticide, nerve gasses
drugs that affect adrenergic pathways
- epinephrine
- alpha and agonist and antagonists
- beta agonists and antagonists
epinephrine family clinical drug use
- epineph
- psudoeph.
- ephedrine
stimulate adrenegic receptors
effects: increased heart rate, increase b.p., relaxed airways, dialated pupils, release of energy reserves.
sympath. vaso.constric. a result of activating..
alpha 1 in blood vessels
alpha 1 agonist:
increase vasoconstriction and increase b.p.:
treat hypotension
alpha 1 antagonist:
smooth muscle in blood vessel wall
reduce vasoconstriction and reduce blood pressure
treat hypertension
alpha 2 receptors:
blood vessel walls
autoreceptors
decrease NE release from terminals
Alpha 2 agonists:
sympathetic terminal
decrease NE release at sympathetic terminals. decrease sympathetic activity.
used to decrease heart work and decrease blood pressure.
beta 1 agonist
sympathetic nervous system normally causes increase in heart rate and contractility by activating beta 1 receptors at heart
beta 1 antagonist
eart sa/av nodes and ventricle wall
beta 1 antogonist reduce heart rate and contractility to decrease heart work.
beta 2 agonist
smooth muscle in bronchioles
sympathetic nervous system usually relaxes smooth muscle airway.
used to treat asthma and other resp. cond.
