Synapse/ synaptic function Flashcards
synapse
site of communication between neurons
components of synapse
- presynaptic neuron
- post synaptic neuron
- synaptic cleft
presynaptic neuron (structure, function)
Structure
- axon terminal
- contains synaptic vesicles (holt NT)
- contain voltage gated calcium channels
Function
-transmits signal
post synaptic neuron (structure, function)
Structure
- usually dendrites or soma
- contain receptors for NT
Function
-receives signal
synaptic cleft (structure, function)
Structure
-narrow extracellular space between neurons
Function
-allow diffusion of NT
Communication across membrane steps (6)
- AP arrives at axon terminal
- voltage gated calcium channels open
- Ca2+ flows in –> exocytosis of synaptic vesicles
- NT diffuse across cleft –> bind to receptors
- postsynaptic cell responds
- response is stopped when NT is removed from cleft
- degradation, reuptake, diffusion
Effects of NT
-change membrane potential in post-synaptic cell
- excitatory
- inhibitory
excitatory
- excitatory postsynaptic potential (EPSP_
- depolarizing
- NT bind to receptors triggering Na+ channels to open having Na+ move into cell –> depolarizing
- moves membrane closer to threshold
Inhibitory
- inhibitory postsynaptic potential (IPSP)
- hyperpolarizing
- NT binds to receptors triggering:
- K+ channels to open. K+ moves out of the cell –> hyperpolarizing
- Cl- channels to open. Cl- moves into cell –> hyperpolarizing
- NT binds to receptors triggering:
- moves membrane potential further from threshold
- membrane stabilizing
divergence
one presynaptic neuron –> several post-synaptic neurons
convergence
several presynaptic neurons –> one post synaptic neuron
graded potentials (what they are and properties)
-small changes in membrane potential due to ion channels opening/ closing in response to stimuli
- properties
1. graded
2. decremental
3. depolarizing or hyperpolarizing
4. summation
graded
-change in membrane potential reflects the strength of the stimulus
- weak stimuli –> small change
- strong stimuli –> large change
decremental
-change dissipates with distance from the stimulus
summation (what it is and types)
- can combine effects of stimuli
- add, cancel
Types
- temporal
- same stimulus
- repeated close together in time
- spatial
- different stimuli
- overlap in time
purpose of graded potentials and how
graded potentials determine if an action potential will occur or not.
How? if the membrane potential at the axon hillock is depolarized about threshold –> AP
