Endocrine System: Endocrine Signalling Flashcards
How do hormones communicate locally? (3)
gap junctions (direct cytoplasmic connection) contact-dependent signals (interaction between membranes) autocrine and paracrine signals (signal molecules act on secretory cell)
What is autocrine?
when the cell acts on itself
What is paracrine?
when the cell acts on nearby cells
How do neurohormones move from neuron to response?
neuron (action potential) to neurotransmitter to blood to cell with receptor to response
Why is endocrine system important?
metabolism regulation
responding to stress
regulating growth and development
controlling wake/sleep, temp, reproduction
Parts of the endocrine system from head to toe (17)
pineal gland, hypothalamus, pituitary gland, thyroid, parathyroid, thymus, heart, liver, stomach and intestines, adrenal glands, pancreas, kidney, testes, ovaries, adipose tissue, skin
Does an endocrine gland have a duct? What does it do? What is an example?
ductless
release hormones into surrounding fluid
adrenal gland
Does an exocrine gland have a duct? What does it do? What is an example?
ducts substances (non-hormonal) travel along surface salivary glands some organs have both types, eg. stomach and pancreas
Three forms of signaling
autocrine paracrine endocrine (hormones diffuse into blood stream)
3 main types of hormones + example of each
peptides and proteins (insulin)
steroids (progesterone)
amines (noradrenaline)
How do the types of hormones differ? (3)
how they are made, stored, released and transported
how long they stay active
how they produce effects
What are peptide/protein hormones? How are they made? Where are they stored? How long do they last? How are they transported?
amino acid chains of different length
many synthesized as preprohormone then modified into prohormone in Golgi body
short half-life
lipophobic/hydrophilic (transported in blood but cannot cross plasma membrane)
What are steroids? When are they made? How long do they last? How are they transported? What do they do?
derived from cholesterol
made as needed in gonads, adrenal glands and
placenta
bound to carrier proteins in blood (increases half life)
lipophilic (cross plasma membrane to receptors in cytoplasm or nucleus
activates transcription of target genes
What are amines? How are they made? What are the two types?
amino acids with modified groups
small size
derived from tyrosine (usually)
catecholamines and thyroid hormones
Where do catecholamines come from? Are they lipophobic or lipophilic? What do they bind to? What do they do? How long do they last?
tyrosine derived lipophobic (hydrophilic) cell surface receptors activates signal transduction cascades half-life short (like peptides)
Where do thyroid hormones come from? Are they lipophobic or lipophilic? What do they bind to? What do they do? How long do they last?
iodinated tyrosine derived lipophilic (hydrophobic) intracellular receptors activates genes half-life few days (like steroids)
What is a half-life?
time taken for concentration of substance to reach 50%
How are hormones removed from plasma?
liver and kidneys remove
What determines the size of a hormone response? (4)
amount
affinity (between hormone and receptor)
number of receptors
functionality of components downstream (of receptor)
What is up-regulation and down-regulation?
up: target cells form more receptors in response
down: target cells lose receptors in response
Where can receptors be located?
on surface of membrane
in cytoplasm
in nucleus
How is hormone secretion regulated? And an example of each? (2)
negative feedback (maintaining homeostasis by responding to stimuli, maintaining appropriate levels of most hormones) positive feedback (reinforcing stimulus, oxytocin release during childbirth)
What three factors influence levels of hormone in plasma?
rate of secretion (regulated - most important)
rate of binding (to carrier proteins)
rate of metabolism (activation/degradation)
What are the four types of cell surface receptors?
receptor channel
receptor enzyme
G protein-coupled receptor
integrin
How does the receptor channel work?
ligand binds to open or close channel
How does the enzyme receptor work?
ligand binds to receptor enzyme and activates intracellular enzyme (amplifier enzyme) which turns on second messengers and causes response
How does the G protein-coupled receptor work?
ligand binds to G protein-coupled receptor and opens ion channel or alters enzyme activity
How does the integrin enzyme work?
ligand binds to integrin and alters the cytoskeleton as it is connected via anchor protein
The response to a hormone depends on…
receptor type as the same hormone can cause different responses, eg. noradrenaline can cause vasoconstriction and vasodilation
Lipophilic hormones (** and **) act primarily on _______ receptors
steroid and thyroid intracellular receptors (membrane, cytoplasm, nucleus)
