cell signaling Flashcards
what are the three ways cells communicate?
- secreting chemical signals
- displaying molecules on their plasma membranes
- gap junctions
why do cells communicate with each other?
- regulate their development and organization to tissues
- control their growth and division
- coordinate other activities
how do cells send signals through chemical mediators that act locally?
- hormones travelling through the bloodstream via endocrine system
- neurotransmitters at synapses between two neurons
what communications do local chemical mediators act through?
- paracrine
- autocrine
- contact-dependent
what are the modes of secretion?
- merocrine
- holocrine
- apocrine
what is the type of secretion if the cell secretes signal by exocytosis without any damage to the cell itself?
merocrine
what are examples of merocrine secretion?
sweat glands
mammary glands
If the whole cell is expelled during the process of secretion and the ruptured cell becomes part of the secretory product, what kind of excretion is this?
holocrine
what is an example of holocrine secretion?
sebaceous glands
what is the secretion where only the apical part of the cell is shed in the secretory product?
apocrine
what is an example of apocrine secretion?
sweat glands in the armpit
what do all three cell signaling types (autocrine, paracrine, and endocrine) have in common?
involve secretion of some kind of chemical signal from a cell that binds to a receptor and causes downstream effect
what kind of cell signaling occurs when a cell releases a signal that acts on itself, binding to receptors on the plasma membrane and causing an effect within the same cell?
autocrine
what is an example of autocrine signaling?
release of cytokine IL-2 from T cells
how do cytokines protect our bodies through our immune system?
by promoting proliferation and differentiation of the same T cells
what cell signaling occurs when the cells releases a signal that acts on nearby cell and causes a downstream effect on target cells?
paracrine
where can paracrine signaling be seen?
neuromuscular junction
what cell signaling occurs when a cell releases a signal that must travel through the bloodstream to reach its target cells, which is often far away?
endocrine
what is an example of endocrine signaling?
hypothalamus releases GnRH that acts on the anterior pituitary to release LH that acts on Leydig cells in the testicle to produce testosterone
what type of signaling involves the chemical messages sent between two neurons at a synapse?
neurotransmitter
In order to deliver a message from one cell to another, the signal sent must be received by a ______
receptor
what are the two broad groups of cell receptors?
intracellular receptors
cell-surface receptors
where are intracellular receptors found?
within the cell, usually in the nucleus
what kind of substrates do intracellular receptors bind to?
substrates that can cross the plasma membrane , like steroid hormones
list examples of steroid hormones
estrogen
testosterone
progesterone
corticosteroids
true or false: steroid hormones are lipid soluble and can easily diffuse through the plasma membrane
true
where do most steroid hormone receptors bind to?
nucleus of the cell
what happens when steroid hormone receptors bind to the nucleus of the cell?
causes an overall change in the levels of gene expression that leads to the production of specific proteins to produce effects
what is androgen insensitivity syndrome?
X-linked recessive disease caused by the cells’ inability to respond to adrogens present in the body
During development of the embryo, there are certain critical periods in which the sex of the organism is determined by the response of the cells to the presence or absence of _________.
androgens
what is an androgen?
steroid hormone that regulates development and maintenance of male characteristics
while the fetus develops, how will it develop into a male fetus?
presence of androgens
how will a fetus develop into a female fetus?
no androgens present
on the Y chromosome, what is the sex determining region?
SRY gene
what is the purpose of the SRY gene?
induces the development of the testes that produces testosterone
what happens physiologically to the bodies of people with androgen insensitivity syndrome?
- individuals born with Y chromosome produce appropriate amounts of testosterone but their cells do not respond to it
- individuals present phenotypically as female
- patients may have undescended testes that remain in their abdominal cavity, poor beard growth, and gender dysmorphia
list some examples of water soluble molecules
neurotransmitters
protein hormones
growth factors
how do water soluble molecules cross the cell membrane?
binding to a receptor that’s on the surface of the cell
Once the molecule has bound to the cell surface receptor, the receptor converts this binding event into an _________________ which alters the activity of the target cell (the cell with the receptor).
intracellular cascade
what happens when a ligand binds to the target cell?
undergoes conformational change
what are the different kinds of cell surface receptors and provide and example for each
- ion-channel receptor- acetylcholine receptor
- transmembrane receptor
- enzymes with intrinsic enzymatic activity- tyrosine receptor kinases
- enzyme-associated receptors- G-protein coupled receptors
what are secondary messengers?
messengers between receptor and downstream proteins that mediate cell actions
what are examples of secondary messengers?
cAMP and calcium ions
what is cAMP?
secondary messenger used among many signal transduction pathways
what is glucagon?
protein hormone produced from alpha cells of the pancreas
when and why is glucagon released into the bloodstream?
during fasting periods to maintain our blood glucose at a constant level
what is an example of a pathway that uses cAMP?
transduction pathway of glucagon
what is the receptor for glucagon?
G-protein coupled receptor
what are the 3 subunits of G-protein coupled receptor
- alpha
- beta
- gamma
what enzyme produces cAMP?
adenylate cyclase
what happens when glucagon binds to the receptor?
GDP molecule is exchanged for GTP which causes the release of the alpha subunit from the beta and gamma subunit
what unit activates adenylate cyclase to use GTP to create cAMP?
alpha
cAMP binds to ____________ which can phosphorylate downstream proteins to activate them
protein kinase
when are calcium ions used as a secondary messenger?
during muscle contraction
When a muscle cell is stimulated by the excitatory neurotransmitter __________, the intracellular calcium concentration increases, which causes the muscle cell to contract.
acetylcholine
how does the sarcoplasmic reticulum play a role in the rapid increase in intracellular calcium concentration?
it stores the ion in large amounts and releases it into the cell’s cytoplasm when stimulated
what is used as a secondary messenger to induce the fusion and release of neurotransmitter containing vesicles into the synaptic cleft?
calcium
Once a neuron is stimulated by an action potential, there is also an increase in the intracellular concentration of calcium at the _____________
axon terminal.
what is myasthenia gravis?
autoimmune disorder that results in the destruction of acetylcholine receptors at the neuromuscular junction so muscles cannot contract properly
what are symptoms of myasthenia gravis?
diplopia
dysphagia
dysarthria
difficulty chewing
why are patients with MG given edrophonium or pyridostigmine?
they temporarily block the action of acetylcholinesterase so acetylcholine can last in the neuromuscular junction for a longer time to induce response in the muscles
