Test 1 Flashcards
what was berthold’s conclusion
- There must be a ‘secretory, blood-borne factor” responsible for the effects of the male chicken developing
Horsley and Murray conclusion
- Successfully used organotherapy
- Horsley removed thyroids in monkeys and they developed hypothyroidism
- Murray developed extract from sheep thyroid which was a successful replacement treatment
Bayliss and Starling
- First to put a name to hormones
- Pancreas’s only connection with body is via blood vessels which means there must be a chemical in the blood.
Halban conclusion
- Glands don’t communicate through nerves but instead internal secretions
How to design endocrine experiments
REMOVE IT AND PUT IT BACK (RORO)
- Remove
- Observe
- Replace
- Observe restoration
Hormone
Regulatory substance produced in an organism and transported in tissue fluids, such as blood, to stimulate specific cells or tissues into action
What are the two types of local communication
autocrine
paracrine
How does autocrine work?
substance released by the cell as a self regulator
How does paracrine work?
substance is released to a target cell nearby. This results in quick responses that only last a short time
Long Distance messenger
Endocrine
substances are released and travel to distant cells through the blood. relatively slow
3 types of hormones
peptides
steroids
monoamine hormones
What determines transport
water solubility
hydrophobic
not water soluble. hormone needs help moving through the blood
hydrophilic
water soluble. can move freely through the blood
what influences hormone-cell interactions
lipid solubility
lipophilic
lipophobic
lipophilic can move easily across membrane barriers while lipophobic needs help moving across
Characteristics of peptide/protein hormones
structure: chain of amino acids
water soluble
lipid insoluble
how many amino acids on each
peptides
polypeptides
proteins
glycoproteins
peptides- less than 20
polypeptides- 20 -100
proteins- more than 100
glycoproteins - carbohydrate added
Peptide synthesis
encoded by genes (translation and transcription)
original translate protein is called pre-prohormone or prohormone these must undergo translational modifications
peptide storage
stored in endocrine gland in secretory vesicles until release is triggered
peptide signaling
binds to cell surface receptors - fast 2nd messenger signals
Characteristics of Steroid Hormones
chemical strucuture - carbon ring
hydrophobic
lipidphilic
all derived from cholesteral
where are steroid hormones produced
adrenal glands, gonads, and some additional tissue
steroid storage
cannot be stored. made on demand
steroid signaling
binds to intracellular receptors; slow genomic effect
Specificity
receptors bind to only one hormone or class of hormone
characteristics of hormones
distinguish a hormone from other molecules with similar structures
bind to hormone even when concentration is low
conformational change when bound to the hormone
catalyze biochem events
Types of Receptors
Intracellular (in cytosol and nucleus; steroids and thryoid hormones)
membrane-bound (on cell surface; peptide and most monoamines)
what influences sensitivity of target cells
- hormone concentration
- receptor affinity
- # of receptors
negative feedback regulation
hormones or their physiological responses inhibit further secretion. Most hormones are regulated this way.
positive feedback
hormones cause even more hormones to be
released. Drive for secretion becomes progressively more
intense until it terminates with some cataclysmic event
down-regulation
tissue decreases receptors
less sensitive to hormone
up-regulation
tissue increases receptors
more sensitive to a hormone
seen when hormone levels are chronically low
synergistic effects
2 hormones with similar effects produced an amplified response
antagonistic effect
2 hormones have opposing effects, usually act to maintain homeostasis
permissive effects
one hormone enables another to act, even though the hormone itself does not initiate the response. 2 hormones acting together may produce an effect neither can make alone
agonists
bind to the receptor and
produce a similar response to the intended hormone because they are so structurally similar
antagonistic
bind to the receptor
but don’t produce a response, because they are just structurally similar enough to have a high
affinity but not to activate it. Prevents the hormone from binding.
heat shock proteins
bind to the intracellular receptor when hormone is not present
released when hormone arrives
Hormone response element
portion of dna receptors bind to.
2 main forms of membrane-bound receptors
2nd messenger (G-protein)
intrinsic enzymatic activity (tyrosine kinase)
G-protein signaling basics
3 subunits
effector enzyme
target of activated G
proteins that produce second messengers
second messengers
intracellular signaling
molecules released by the cell in response to
exposure to a hormone
alpha subunit
Alpha (s) - adenylyl cyclase - cAMp
Alpha (I) - adenylyl cyclase - cAMP
Alpha (q) - phospholipase C - IP3/calcium
Serotonin as neurotransmitter
mood
feelings of relaxation and sleep
memory processing
cognition/learning
serotonin as hormone (in gut)
satiety
digestion/nutrients absorption
gut motility
Dopamine as neurotransmitter
motivation/pleasure seeking
cognition/memory
fine tuning of motor functions
dopamine as hormone
secreted by hypothalamus to regulate
prolactin secretion (“prolactin-inhibiting
hormone”)
dopamine mesolimbic pathway
Dopaminergic neurons project from ventral tegmental area (VTA) to nucleus accumbens (NA)
- NA is part of the limbic system - network of connected structures that influence emotions, motivation, and memory
- Functions: motivation, emotions, reward, and addiction
dopamine mesocortical pathway
- Dopaminergic neurons project from
ventral tegmental area (VTA) to the
cortex (mostly frontal lobe) - Functions: cognition and emotions
Dopamine nigrostriatal pathway
- Dopaminergic neurons project from
substantia nigra to striatum and
basal ganglia - Functions: voluntary movement
Dopamine tuberinfundibular pathway
- Dopaminergic neurons project from
hypothalamus to pituitary - Dopamine is released into circulation
functions: inhibits prolactin release
Dopamine and Parkinson’s
Parkinson’s Disease: lose ability to control movements due to the death of dopamine secreting cells
Dopamine and Schizophrenia
Dopamine hypothesis of schizophrenia:
* Too much dopamine in the mesolimbic
pathway - hallucinations
* Too little dopamine in the mesocortical pathway - cognitive symptoms
grows out of the digestive tract of the embryo
anterior pituitary
anterior pituitary cell types
acidophils
basophils
chromophobes
extension of the brain
posterior pituitary
posterior pituitary cell types
nerve cells
connects to the hypothalamus via the hypophyseal portal system (blood vessels)
Anterior Pituitary Lobe
connects to the hypothalamus via neurons
posterior pituitary lobe
posterior pituitary has 2 regions
- Pars nervosa – largest region and where most hormones are stored
- Infundibular stalk – connects the pars nervosa to the base of the brain
largest region and where most hormones are stored
pars nervosa
connects the pars nervosa to the base of the brain
infundibular stalk
Posterior Pituitary function
does not produce hormones. Just stores and secretes two protein hormones.
Arginine vasopressin
Oxytocin
Hormone secretion is regulated by the hypothalamus via nerve cells
Arginine Vasopressin
Target organs are kidneys and blood vessels
2 major vasopressin receptors
V1- located on blood vessels and stimulates vascular smooth muscle contraction
V2- located on kidneys and stimulates reabsorption of water into the blood
Regulated by baroreceptors in blood vessels that detect decreases in blood
pressure/volume and signal the hypothalamus to trigger secretion of vasopressin
V1 - Vasopressin
Regulated by osmoreceptors that
detect increases in osmolality and
signal secretion of ADH
V2 - Anti-Diuretic Hormone
Oxytocin Functions
The primary target organs are muscles in the:
Uterus - stimulates the uterine muscles
to contract during childbirth
Breasts - promotes ejection of milk
through ducts during lactation
what is the love hormone
oxytocin
Anterior Pituitary Anatomy
Pars Distalis
pars intermedia
pars tuberalis
largest region and where most hormones are produced
pars distalis
resides next
to the posterior pituitary;
produces one main hormone
pars intermedia
extends from pars distalis and wraps around the infundibulum, contains
blood vessels
pars tuberalis
produces
and secretes most of the
hormones of the pituitary
anterior pituitary
Hormone secretion is
regulated by the
hypothalamus via the
hypophyseal portal
system
pituitary cell type that contains polypeptides
acidophils
pituitary cell type that contains glycoproteins
basophils
pituitary cell type that contains minimal hormone content
chromophobes
secreted from acidophils
prolactin and growth hormone
secreted from basophils
FSH
LH
Thyroid stimulating hormone (TSH)
ACTH
corticotropin hormone - CRH - Pituitary (acth)- adrenal hormone
HPA axis
GnRH - LH and FSH - gonadal hormone
HPG axis
thyrotropin releasing hormone - TRH - TSH - thyroid hormone
HPT axis
Its only known physiological role is to
stimulate secretion of thyroid
hormones
(T3 and T4) regulate metabolic
rate and energy expenditure
TSH
Targets the gonads and promotes secretion of sex steroids
FSH and LH
promotes growth of ovarian follicles and stimulates sperm
production in testes
FSH
induces ovulation and stimulates secretion of sex steroids from
ovaries and testes
LH
Regulation of FSH and LH Secretion
LH is favored with fast pulses
FSH is favored with slow pulses
Targets the adrenal glands and promotes glucocorticoid secretion
(cortisol and/or corticosterone)
ACTH
plays a role
in metabolism, immune
function, and stress responses
Hypothalamic-Pituitary-Adrenal Axis
is stimulated by the
hypothalamic secretion of prolactin-
releasing hormone
Main function: promote lactation for breastfeeding
Prolactin
targets most cells in the body, but primarily bone, muscle, and liver where it promotes protein synthesis and tissue building.
Growth Hormone
Growth hormone is inhibited by hypothalamic secretion of
somatostatin
is characterized by excess growth hormone after puberty, often because
of a non-cancerous tumor on the pituitary gland.
Acromegaly
is characterized by excessive growth in children when growth hormone levels are too high before puberty. Typically caused by a non-cancerous pituitary
tumor.
gigantism
is characterized by short stature with normal
body proportions and normal mental development. Adult height is less than 4’10”. Can be present at birth or develop later.
Pituitary dwarfism
