Hormones 1 & 2 Flashcards
what are peptide, steroid and amine hormones used for
synthesis, storage, release, signal transduction
function of the endocrine system
to allow for communication of systems at local and DISTANT levels to maintaining homeostasis
how does endocrine communication system
direct release into blood stream and transported to (distant) target e.g. insulin
define endocrinology
the study of the structure/function of endocrine glands and their secretions (hormones) in regulating the physiology of the organism
1. Endocrine glands/tissues/cells
2. Hormones
define endocrine glands
organs or groups of cells which synthesise
and secrete hormones and pass them directly
into the blood
endocrine glands are ductless
compare the endocrine and exocrine glands
ducts?
secreted into ?
methods of delivery ?
distance?
e.g.?
Endo:
ductless
secrete into bloodstream
use blood as vehicle
short or long distance
e.g. thyroid gland
Exo:
contain ducts
secrete into duct
specific delivery to target
generally short distance
e.g. salivary glands
is the pineal gland/hypothalamus a gland/cell
PG: gland
H: cluster of neurons
is the posterior/anterior pituitary a gland/cell
PP: extensions of hypothalamic neurons
AP: gland
is the thyroid/parathyroid/heart/liver a gland/cell
T: gland
L: cell
H: cell
P:gland
is the thymus/ stomach and small intestine/pancreas a gland/cell
T: gland
S: cells
P: gland
is the adrenal cortex/medulla/kidney a gland/cell
AC: gland
AM: gland
K: cells
is the skin/testes/ovaries a gland/cell
S: cells
T: glands
O: glands
is the adipose tissue/placenta a gland/cell
AT: cells
P: gland
define a hormone
a chemical secreted from an endocrine gland (or
cell) and travels in the blood to its target organ and
mediates a specific effect
* specificity conferred by target cell receptor
expression
key features of hormones
synthesis/storage prior to release
where are hormones secreted from and into
from designated endocrine cells/tissues and into the bloodstream
what is the mode of action for hormones
receptor-mediated- confers target selectivity
what is a key function of hormones
serve homeostatic function- require on/ off activity
describe insulin action in bloodstream
increased glucose, increased insulin release
pathway 1
- glucose uptake, storage + utilisation
pathway 2
-insulin effects ‘switched off/limited by several limiting methods
pathway 3 : unchecked insulin activity, no insulin limitation
- excessive depletion of blood glucose levels
- loss of nervous system function, potentially fatal
what are the limitation measure to terminate activity of hormones
release limited/tightly controlled
- degradation in blood mainly by liver/kidney enzymes
- metabolites excreted in urine/bile
- bound to receptors
which hormones get terminates when bound to intracellular receptors
steroid: degraded by intracellular enzymes
which hormones get terminates when bound to cell surface receptors
peptide: degraded by extracellular enzymes internalised and degraded inside cell
how is the hormone balance measured
through its half-life - time needed to concentration/2
what are pattern productions during hormone production
different hormones have different pattern of productions depending on their role of hormones
what does the chronic/ constitutive pattern of production for hormones look like and what is its function, provide an example
constant low amplitude wave
- maintains constant concentration in the blood
e.g. thyroid hormones
what does the acute/stimulated pattern of production for hormones look like and what do the peaks correspond with, provide an example
*episodic release when required
*tightly controlled by stimulus and feedback
e.g. insulin
what does the cyclic/pulsatile pattern of production for hormones look like and what do the peaks correspond to, provide an example
*show regular rhythm of production
*peaks correspond to physiologically relevant times for hormone action e.g. growth, development
*linked to pineal gland, melatonin and circadian rhythm
e.g. growth hormone
name the 3 types of hormones chemical classification
peptide, steroid, amine hormones
give examples for the peptide hormones
peptide, protein, glycoprotein
are peptide and steroid hormones water soluble
peptide hormones are water soluble, hydrophilic - dissolves in plasma for transport
Steroid hormones are hydrophobic
describe the peptide and steroid hormones half life
P : short half life, open to degradation during transit to target
S : long half life due to protective effects of carrier proteins
how are peptide hormones stored and released, describe the its secretory pathway
-pre-synth’d → stored in vesicles ready for release
- released following stimulus → Ca2+-stimulated exocytosis
what is the function of the 2nd messenger system in peptide hormone signal transduction
modification of existing
protein
→rapid response
may also alter gene
expression
→slower, longer lasting
activity
where is the production of steroid hormones restricted to and where are they derived from
gonads, adrenal cortex and placenta
in the S.E.R
what do steroid hormone producing cells have
extensive smooth ER for cholesterol synthesis
describe the steroid hormone production pathway into bloos stream
esterified cholesterol
–> signal is released
–> conversion to active hormone
–> cytoplasmic con. increases
–>simple diffusion across across membrane into blood stream
how and where are steroid hormone stored
stored as lipid droplets (esterified form-precursor storage) within the S.E.R for cholesterol production
steroid hormones have poor solubility, what do they need to help them pass across the membrane
plasma carrier proteins
what does lipophilic mean for the molecular transport
tend to dissolve in lipids hence cannot be stored in vesicles
are steroid hormones pre-synthesised
no , they are lilpophilic- cant be stored in vesicles
why do hormones need a carrier protein
required for blood borne transit and protection for degradation
benefits of carrier proteins
increased solubility and half life (>60 min)
are carrier proteins specific or non specific, and provide example
they can be both
S: corticosteroid- binding globulin
NS: albumin
how do steroid work in collaboration with the carrier proteins to prolong its activity
- as steroid taken up; more is
released from carrier
→creates reservoir of hormone ready for action
→prolonged activity as
the effects of the carrier proteins on the steroid hormones and equilibrium
equilibrium dictates a small
proportion of steroid is
unbound within blood stream
bound steroids blocked from entering the cells, so only unbound will cross
what receptors do steroid hormones use and what does the receptor complex form
intracellular receptor, transcription factor
steroid hormone signal transduction pathway
→acts on specific genes with
hormone response elements
(HREs)
- influences protein production (+ve or -ve)
→cellular response (delayed)
(genomic effects)
can steroid hormones bind to cell surface receptors
*some evidence of action through C.S.R
→non-genomic, rapid effects
Rare but not impossible
compare a steroid and peptide hormone:
stored as…
short/prolonged action
receptor type
response time
Peptide
stored as mature form
short-acting
cell surface receptor
rapid response
Steroid
stored as pre-cursor
prolonged action
intracellular receptor
slow response
where is an amine hormone derived from
either tyrosine or tryptophan (aromatic amino acids)
provide example of an amine hormone
tryptophan –> enzymatic conversion into melatonin
what is the role of melatonin
*circadian rhythm hormone
*day/night cycling
what is tyrosine
it is the parent amino acid for 2 different classes of amine hormones: catecholamines and thyroid hormones
function of catecholamines
association with nervous system
→ neurohormones
how are catecholamines made
by modifying the side groups of tyrosine: dopamine, norepinephrine, epinephrine
which other hormone class does catecholamines and thyroid hormones behave like
C: peptide hormones:
H : steroid
how are thyroid hormones synthesized
from 2 tyrosine and iodine atoms
what functional group is the thyroid hormone
aromatic group: flat, cyclic ring structures
meaning they are non polar
describe the shape and position of the pituitary gland within the body
bean shaped and sized endocrine gland (~14 mm diameter)
what is the the infundibulum
connecting stalk the pituitary gland to the hypothalamus
how many tissues does the pituitary gland have and name them
contains 2 different types of tissue – anterior and posterior pituitary
name key functions of the pituitary gland
adrenal function
thyroid function
gonadal function
lactation parturition
growth
water balance metabolism
name key functions of the hypothalamus
cold
stress
metabolic
demand
hydration
status
pregnancy
exercise day/night menstrual
cycle sleep
breastfeeding
puberty
what is the role of the posterior pituitary
stores and releases 2 peptide neurohormones:
➢vasopressin (anti-diuretic hormone; ADH)
➢oxytocin
where is the neurohormones synthesised in the posterior pituitary
magnocellular neurons in the hypothalamus
what do the different subsets make in the posterior pituitary
different subsets make either vasopressin or oxytocin
describe how the hormones are received from the hypothalamus in the posterior pituitary
axons project down the infundibulum to the nerve terminal in the posterior pituitary in a vesicle
how do the hormones get into the blood stream
hormones are released into blood from vesicle
what type of hormones do oxytocin and vasopressin behave as and what does that mean
typical peptide hormones
i.e. synthesis and storage in vesicles, cell surface receptors
what is vasopressin (ADH)’s main function
regulate water balance
what is oxytocin’s main function
milk ejection and uterine contraction
what is vasopressin (ADH) released triggered by
increased plasma osmolarity, decreased plasma volume/blood pressure
what is oxytocin triggered by
suckling, labour (baby’s head against cervix)
what is vasopressin’s Site/mode of action
kidney collecting ducts
→ increased water reabsorption
vascular smooth muscle uterine smooth muscle
→ increased blood pressure
what is oxytocin sit of action
milk duct smooth muscle
→ contracts muscle, ejecting milk
→ child birth
which organ is the true endocrine organ
anterior pituitary gland
how is the the anterior pituitary connected to the hypothalamus
connected to hypothalamus via hypothalamic-hypophyseal portal system (2 capillary beds connected in series)
what is the role of the hypothalamus in the anterior pituitary
hypothalamus does this by producing “releasing” or “inhibiting” hormones that stimulate or inhibit hormone production from the anterior pituitary
what are tropic hormones
hormones controlling release of other hormones
stimulate and maintain growth of endocrine cells
what forms a multi-layered endocrine axis
anterior pituitary
what’s the difference between hypertrophy and atrophy
A: lack of hormone input
H: too much hormone input
describe the Hypothalamic-hypophyseal portal system
- integration of inputs
- hypothalamic neurons
that produce releasing/inhibiting hormones - hypothalamic
hormone released
from stimulated
H.N - ant. pit. cell releases hormone that diffuses into
capillary system&circulation - hypothalamic hormone moves through portal system, binds to surface receptor of A.P cell
- endocrine cell in A.P with hormone receptor for hypothalamic inhibiting or releasing hormones
why do we need a Hypothalamo-hypophyseal portal system
portal system → only small volume of blood as a vehicle
*very small amounts of hormones & neurosecretory
neurons required
*short distance – very rapid and dynamic
what did Guillemin and Shalley do 1977
Nobel prize for obtaining hypothalamus of animals, sheep/pigs
name the 7 hypothalamic hormones
- dopamine
- prolactin-R. H
- thyrotropin-R. H
- corticotropin-R. H
- growth hormone-R. H
- growth hormone-I.H (somatostatin)
- gonadotropin-R. H
R. H - Releasing hormone
I. H - Inhibiting hormone
what type of hormone are all the 7 hypothalamic hormones
peptide aside from dopamine
name all the 7 anterior pituitary hormones
prolactin
thyroid-stimulating hormone
adrenocorticotropic hormone
growth hormone
follicle-stimulating hormone
luteinising hormone
what type of hormone are all the 6 anterior pituitary hormones
all peptide hormones
what is the function of prolactin (Anterior pituitary hormones)
breast → lactation (direct)
what is the function of prolactin (Anterior pituitary hormones)
thyroid → TH release (trophic)
what is the function of prolactin (Anterior pituitary hormones)
ad. cortex → cortisol release
(trophic)
what is the function of prolactin (Anterior pituitary hormones)
breast → lactation (direct)
what is the function of thyroid-stimulating hormones (Anterior pituitary hormones)
thyroid → TH release (trophic)
what is the function of adrenocorticotropic hormones (Anterior pituitary hormones)
ad. cortex → cortisol release
(trophic)
what is the function of growth hormone (Anterior pituitary hormones)
liver → IGF-1 release (trophic)
& tissue growth actions (direct)
what is the function of luteinising hormone (Anterior pituitary hormones)
gonads → regulation of
reproductive function (direct) &
sex hormone release (trophic)
what do receptor profiles of the anterior pituitary hormone specific cell types key function
different cells types produce different hormones in the A.P
They confers selectivity to incoming hypothalamic hormones
where in the Anterior pituitary hormone-specific cell are the acidophil cells and what hormone types are there
top half, lactotrophs (PL), somatotrophs (GH)
describe the 3 integration centres in the anterior pituitary feedback control
hypothalamus, anterior pituitary, target endocrine cell
where in the Anterior pituitary hormone-specific cell are the basophil cells and what hormone types are there
bottom half, corticotropes (ACTH), gonadotrophs (LH/FSH) and thyrotrophs (TSH)
are hormones are positive or negative feedback signal
hormones themselves act as negative feedback signal
compare the length of the feedback from the endocrine & the anterior pituitary to hypothalamus
AP-H: short loop feedback
E: long loop feedback
where do the portal vessels trophic hormones
directly to the Anterior pituitary
what is cortisol an example of
the anterior pituitary feedback control system
