ch 22 iontropic receptor signaling

parts of a neuron

dendrites, cell body, nucleus, axon hillock, axon, myelin sheath, terminal branches

Na+/K+-ATPase establishes electrochemical gradients of

sodium and potassium

The k+ leak channel ____ the potassium permeability and potassium travels ___ the concentration gradient making (out of the cell)

increases, down

at resting membrane potential the amount of potassium in the cell is ___ than the amount of ___ and viceversa

higher, sodium

acetylcholine is an example of an ___ ____

excitatory neurotransmitter

acetylcholine binds to the nicotinic receptor which is a

ligand-gated ion channel

nicotine receptor is activated by ___. it allows ___ to go into the cell

nicotine, sodium

neurons have two types of voltage gated channels

sodium and potassium

sodium voltage gated channel is made of ___ polypeptide subunits

single

the potassium voltage gated channels is made of ____ polypeptides subunits

4 separate

when the membrane potential depolarizes to -50mv voltage gated channels change their conformation causing the channel to

open

sodium and potassium are surrounded by

water

describe how oxygen helps sodium and potassium get through the channel

to shed the hydration shell of the sodium and the potassium the oxygen atoms in the amino acids channel interacts with their ions and they shed the water allowing them to pass through

sodium and potassium cannot pass though each other’s channel due to ___. they also cannot she enough water to fit in each other’s channel

size

To prevent a channel of opening too quick…

the inactivating particle portion of the protein blocks the channel and after a millisecond it returns to it’s original conformation

describe action potential

1. resting state: sodium and potassium gates are closed and the resting potential is at about -60mV

2. depolarizing phase: sodium channels open and action potential begins when the neuron is depolarized by about 20 mV to its threshold potential. potential reaches +40 mV very rapidly

3. repolarizing phase: sodium channels inactivate and potassium channels open. once the cell reaches its peak positive potential, it repolarizes and returning to a negative membrane potential

4. hyperpolarizing phase: potassium channels remain open and sodium channels close. Often the membrane potential becomes more negative than the resting potential

action potential moves one way due to the

refractory period

myelin is surrounded by ___ ___ that wrap their plasma membrane around the axons of peripheral neurons

schwann cells

the small gaps between the patches of myelin are called

nodes of ranvier

The myelin insulated the axon’s ___ and ion exchange only occurs at the ___

membrane, nodes

the action potention thorugh myelin skips from node to node and that is called

saltatory conduction

___ ___ speeds up the rate of action potential 10x

saltatory conduction

electrical synapse is a physical connection and the presynaptic and post synaptic cells are directly connected by

gap junction

in electrical synapses sodium diffuses directly from the presynaptic neuron to the post synaptic neuron causing

depolarization

in chemical synapse the presynaptic and post synaptic cells are separated by the

synaptic cleft

formation of the binding between synapses

neurotransmission is a form of regulated transmission. When the action potential reaches the synaptic terminal volted gated Ca++ channels open. Ca++ diffuses rapidly into presynaptic neuron acting as secondary messenger causing vesicles filled with neurotransmitters to fuse with the plasma membrane. Neurotransmitter is released and diffuses across the synaptic cleft and binds receptors on the postsynaptic neuron

synaptic vesicles dock at the plasma membrane with

VSNARE and T SNARE

___ inputs open sodium channels generating excitatory postsynaptic potential

excitatory

___ inputs open potassium channel or chloride channels and generate the postsynaptic potential

inhibitory

there is no voltage gated channels in the ___ ___ only past axon hillock

cell body

the neurotransmitter can be

diffused degraded or retaken

action potential can only be generated if the

membrane potential reaches threshold at the axon hillock