Flashcards in Topic 20: Synapses and Sensory Receptors Deck (40):
What is a synapse?
a junction between synaptic terminal and another cell
What are the 2 types of synapses?
electrical and chemical
What are the steps in chemical synapses?
1. AP reaches terminal of presynaptic cell
2. presynaptic cells release neurotransmitters into synaptic cleft
3. response in polysynaptic cell
How does signaling across a chemical synapse work?
- presynaptic cell synthesizes neurotransmitters, stores them in synaptic vesicles
-When AP reaches synaptic terminal:
- voltage gated Ca2+ channels open
-> Ca2+ enters
-> some synaptic vesicles fuse with PM
-> neurotransmitters released into synaptic cleft
What do neurotransmitters do?
diffuse across synaptic cleft
bind and activate specific postsynaptic receptors
What are the 4 examples of neurotransmitters?
What is acetylcholine responsible for?
muscle stimulation, memory learning
What is glutamate responsible for?
AA, important in brain
What is dopamine responsible for?
level in brain affects mood
What is endorphins responsible for?
What is postsynaptic potentials?
change in membrane potential of postsynaptic cells
What are postsynaptic potentials triggered by?
ligand gated ion channels
What are the 2 types of postsynaptic potentials and what do they do?
excitatory postsynaptic potential: depolarizes
inhibitory postsynaptic potential: hyperpolarizes
What happens during summation of postsynaptic potentials?
addition of all excitatory and inhibitory cells
What happens during temporal summation?
2+ signals arrive at the SAME synapse
What happens during spatial summation?
2+ signals arrive at the same time at DIFFERENT synapses on the same postsynaptic neuron
What is neural plasticity?
capacity for the nervous system to be remodeled
What do neurons do during development?
form more synapses than needed
Where does STM take place and what happens during it?
forms temporary links with LTM which is essential for acquiring memories
Where does LTM take place and what happens during it?
temporary links replaced with permanent connections
What is LTP?
lasting increase in strength of synaptic transmission
What 2 conditions must be met to establish LTP?
1 high frequency series of APs
2. Those APs arrive at terminal when postsynaptic nerve is already depolarized from another stimulus
What are the 2 types of receptors in a postsynaptic neuron?
What are NMDA and AMPA receptors? When do they open?
ligand gated ion channels
open when something specific binds to it
What happens before LTP?
NMDA are already embedded in membrane
AP in presynaptic neuron -> glutamate released into synapse
Glutamate (ligand) opens NMDA receptors
BUT it's BLOCKED by Mg2+
-> no membrane depolarization
How do we establish LTP?
All happen simultaneously:
- depolarization from one synapse
-> Mg2+ released from NMDA receptor
- glutamate released into a different synapse
-> glutamate (ligand) opens NMDA receptors
-> Na+, Ca2+ flow in (only some)
What does the influx of Ca2+ cause?
it causes stored AMPA receptors to be embedded in the membrane
What are the 2 types of sensory receptors and what do they do?
chemoreceptors: stimulus = specific molecules
mechanoreceptors: stimulus = physical change
What are the 4 basic steps of sensory processing?
1. sensory reception
2. sensory transduction
What is gustation?
sense of taste
What are the sensory receptor cells for taste called?
What are the 5 tastant types?
What kind of receptors do taste cells have? Which tastants do they open?
g protein-coupled receptors
sweet, umami, bitter
Which tastants open directly with ion channels?
What happens if tastant is sweet, bitter, or umami?
GPCR activates G protein
G protein activated adenylyl cyclase
adenylyl cyclase converts ATP to cAMP
cAMP opens Na+/Ca2+ channels
What happens if tastant is sour or sweet?
binding opens channels directly
Does everyone taste the same?
No, perception is unique to individuals
What is olfaction?
sense of smell
What is the biggest difference about olfaction and gustation?
sensory cells in the nose are ALSO the afferent neurons