anatomy 9000 Flashcards
graded potentials
strength can vary (depending on strength of stimulus)
occurs at dendrites or cell body
small and localized
action potentials
strength does not vary (will be identical to all other AP’s)
-“all or none process”
occur at “trigger zone” (axon hillock, where axon leaves cell body)
larger scale and can sprea down length of an axon
all or none potential
once an action potential begins the action potential will proceed with a precise and steady process
parts of action potential
- depolarization
- repolarization
- afterpotential (hyperpolarization)
- repeat
depolarization
open Na+ channels
large amount of Na+ diffuses into the ccell
repolarization
starts when membrane potential reaches about +30 to 35 mV
closing Na+ channels and opens K+ channels
Na+ stop moving into cell and K+ start moving out
hyperpolarization
membrane potential drops below resting potential mark briefly then returns to resting potential
refractory period
absolute
relative
absolute refractory period
covers depolarization and repolarization
impossible to begin aother action potential during that time
relative refractory period
during hyperpolarization
another action potential can occur but will require a stronger stimulus than normal
propagation of action potential
- continuous
2. saltatory
continuous propagation
requires depolarization to occur down entire length of axon
saltatory propagation
occurs with myelinated axons
depolarization occurs only at nodes of Ranvier (jumps from one node to the next)
synapse
connection between 2 cells
ex: neuron and its effector cell
types of synapse
electrical synapse
chemical synapse
electrical synapse
extremely common in central nervous system (CNS)
electrical message easily passed from one neuron to next
chemical synapse
extremely common outside of the CNS
neuron releases a chemical called a naurotransmitter
neurotransmiter diffuses across on small space and triggers a response in posysynaptic cell
ex: neuron releasing acetylcholine to stimulate skeletal muscle
many other neurotransmiters involved in other activities
postsynaptic potentials
work in postsynaptic cells to increase or decrease response to a presynaptic neuron
EPSP
IPSP
excitatory postsynaptic potential
depolarize
brings potential closer to threshold
inhibitory possnaptic potential
hyperpolarize
brings potential further from threshold
