Bio Test 2a Flashcards
what make up the neuron
cell body, axon, terminals and dendrites
three conformations of Na+ Channel
closed
open
inactivated
closed Na+ channel
polarized membrane, resting state, maintain membrane potential, -60 mV
opened Na+ channel
membrane depolarized, Na+ flows in, -60 mV to 40 mV
inactivated Na+ channel
allows channel to desensitize and not respond to second signal, if opened then could depolarize membrane more and damage cell
what causes an action potential
depolarization of plasma membrane from -60 mV to -40 mV, mediated by voltage-gated Na+ channel
propagation of action potentials
action potential travels away from site of depolarization, one direction only, movement of electrical signal
synapse
specialized junctions between the transmitting and receiving cells
voltage-gated Ca2+ channel
regulated by membrane potential
electrical signals are converted to…
chemical signals
neurotransmitter
small signaling molecule that converts an electrical signal to a chemical signal
where are neurotransmitters stored?
synaptic vesicle
what triggers the release of neurotransmitters?
the voltage-gated Ca2+ channels
where does the conversion of electrical signal to chemical signal happen?
at the nerve terminals to relay the signal to the target cells
process of converting chemical signal back to electrical
neurotransmitter diffuses across synaptic cleft
neurotransmitter binds to neurotransmitter receptor concentrated in postsynaptic membrane
transmitter-gated ion channels open
action potential generated on target cell
excitatory neurons
cause postsynaptic cell to fire an action potential
excitatory neurotransmitters
acetylcholine
gultamate
serotonin
receptors for excitatory signals allow what two ions to pass?
Na+
Ca2+
inhibitory neurons
prevent postsynaptic cell from firing
strychnine
causes muscle spasms by blocking inhibitory signals
curare
relaxes muscle by blocks excitatory signals
inhibitory neurotransmitters
GABA
glycine
receptors for inhibitory signals allow what ions through?
Cl-
neurotransmitters are major targets for what?
psychoactive drugs
What binds to GABA-gated Cl- channels?
barbiturates
tranquilizers
What neurotransmitter’s reuptake is blocked by an antidepressant?
serotonin
What are the four ways of cell communication?
endocrine
paracrine
neuronal
contact-dependent
endocrine
long distance
uses hormones as communication tool and are long-lived
through the circulatory system
paracrine
short distance (ex. growth factor) short-lived and have local effect might influence back to signaling cell, process called autocrine coordinate activities of neighboring cells
neuronal
specific to nervous system
signal molecules are neurotransmitters
short-lived
happens over a synapse
contact-dependent
membrane proteins on contacting cells
between 2 adjacent cells
intracellular receptors
smal hydrophobic signal molecules (hormones)
signal receptor complex enters nucleus and binds DNA
what does the intracellular receptor NO do?
it cause the relaxation of smooth muscle cells
what are the two types of intracellular receptors?
hormones Nitric oxide (NO)
what are the three classes of cell surface receptors?
ion-channel-coupled receptors
G-protein-coupled receptors
enzyme-coupled receptors
ion-channel-coupled receptors
ion channel and receptor
what is a coupled receptor?
receptor that is also something else at the exact same time
G-protein-coupled receptors
G-protein and receptor are completely separate but associate with each other
enzyme-coupled receptors
a receptor that is also an enzyme at the same time
characteristics of a signal cascade
binding of signal and receptor receptor pases the signal to intracellular signaling molecules signal amplification integration or divergence of signals trigger fast and/or slow responses
what are two common mechanisms that amplify signals?
phosphorylation
GTP-GDP
responses to a signal cascade
the cell survives
the grows and divides
the cell differentiates (gains a specialized function)
the cell dies
signal cascade
extracellular signal molecule receptor protein intracellular signaling molecules effector proteins cell responses
why are cellular responses fast or slow?
When the response is fast, the receptor just changes the proteins function and cell structure, but when the response is slow, the receptor goes through the nucleus, binds to DNA and begins active transcription.
activation of intracellular molecules can be done in what two ways?
phosphorylation
GTP-binding protein
activation of intracellular molecules through phosphorylation
protein kinase is an enzyme that changes ATP to ADP by losing a phosphate group, then after the target cell has received signal, protein phosphatase removes the phosphate
activation of intracellular molecules by GTP-binding protein
has binding site for GDP and GTP, takes off GDP and replaces with GTP through GTP binding, and after signal is received, GTP hydrolysis removes a phosphate to return it to GDP
G-protein coupled receptors
- typical 7-pass transmembrane proteins
- 3 domains: transmembrane
intracellular
extracellular - primarily for: vision, smell, taste and chemoreception
G-protein
- 3 subunits or heterotrimer
- alpha subunit binds GDP and GTP
- breaks into two signaling units upon activation aplha and beta/lamda signaling units
G-protein coupled receptor process
- an inactive g-protein comes into contact with transmembrane protein
- the signal molecule signals the protein and the G-protein activates
- protein breaks into two subunits through GTP binding
- the beta/lambda complex comes to the channel and signals it to open
- the alpha complex then goes through hydrolysis
- the three subunits then reconnect an return to inactivated state
