synaptic and neuromuscular transmission Flashcards
(42 cards)
neuron structural types
structural classification based on # of processes that extend from the cell body
what are multipolar neurons?
3 or more processes extending from cell body
** MAJOR TYPE IN CNS and EFFERENT PNS
what are bipolar neurons?
- only 2 processes
- retina, olfactory system
what are unipolar neurons?
- single, short processes from cell body, then branches into 2 or more
- peripheral processes associated with sensory perception
- primary afferent PNS
what are electrical synapses?
- current flows between cells via GAP JUNCTIONS
- in cardiac and some smooth muscle
- very fast
what are chemical synapse?
- gap between presynaptic and postsynaptic cells- synaptic cleft
1. AP in presynaptic cell causes voltage-gated Ca2+ channels to open
- Ca2+ influx causes release of neurotransmitter from presynaptic terminal
- neurotransmitter binds ligand-gated Na+ channel on postsynaptic cell, leading to depolarization (can be excitatory or inhibitory)
describe synaptic arrangements
neurons are arranged in circuits where input cells synapse on output cells
- output cell may or may not fire an action potential depending on amount of excitation provided by the input cells
one-to-one synapses
- neuromuscular junction
- single AP in motoneuron cases single AP in muscle fiber
one-to-many synapses
- found in some motoneurons of spinal cord
- spinal AP in motorneurons causes many APs in postsynaptic cells
many-to-one synapses
- many presynaptic cells converge on a postsynaptic cell
- common
- need convergence of multiple input neurons to cause an AP -> sum inputs
net= depolarization=
excite
net= hyperpolarization=
inhibit
common to use many-to-one arrangement
inputs are excitatory or inhibitory
excitatory postsynaptic potential (EPSPs)
- pre-synaptic neuron depolarizes post-synaptic neuron, brings neuron’s membrane potential to threshold opens Na and K channels
- Ach, NE, Epi, dopamine, glutamate, serotonin are excitatory neurotransmitters
inhibitory postsynaptic potentials (IPSPs)
- pre-synaptic neuron hyper polarizes post-synaptic neuron and membrane potential moves away from threshold, opens Cl channels
- GABA, glycine are inhibitory neurotransmitters
temporal summation
- two inputs arrive at postsynaptic cell in rapid succession
- effects are additive
spatial summation
- two or more inputs arrive at postsynaptic cell simultaneously
- both inputs could be excitatory -> depolarization
- one could be excitatory, one inhibitory -> cancels/nothing
synaptic fatigue
repeated stimulation yields a smaller than expected response
ionotropic receptors
- ligand-gated ion channels that usually open in response to binding of neurotransmitter
- usually located along dendrites or cell bodies and receive incoming information from other neurons
effects on post-synaptic neuron by neurotransmitters
- may be excited due to Na influx causing depolarization
- may be inhibited due to either K efflux or chloride influx causing hyperpolarization
- Ca influx?: may or may not cause depolarization, Ca usually associated with 2nd messenger system
What does Glutamate (AA) do?
- primary excitatory neurotransmitters in the CNS
what are the types of glutamate receptors?
- AMPA
- NMDA
what does AMPA do?
- allows both Na and K to cross membrane, but gradient drives Na is stronger -> net effect depolarization
what does NMDA do?
depends on glutamate binding AND voltage, when around RMP, Mg ions blocks binding site/movement of other ions- when glutamate binds AND depolarization, Mg block removed
