Topic 20: Synapses and Sensory Receptors

Question 1

What is a synapse?

Answer 1

a junction between synaptic terminal and another cell

Question 2

What are the 2 types of synapses?

Answer 2

electrical and chemical

Question 3

What are the steps in chemical synapses?

Answer 3

1. AP reaches terminal of presynaptic cell
2. presynaptic cells release neurotransmitters into synaptic cleft
3. response in polysynaptic cell

Question 4

How does signaling across a chemical synapse work?

Answer 4

• 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

Question 5

What do neurotransmitters do?

Answer 5

diffuse across synaptic cleft

bind and activate specific postsynaptic receptors

Question 6

What are the 4 examples of neurotransmitters?

Answer 6

acetylcholine
glutamate
dopamine
endorphins

Question 7

What is acetylcholine responsible for?

Answer 7

muscle stimulation, memory learning

Question 8

What is glutamate responsible for?

Answer 8

AA, important in brain

Question 9

What is dopamine responsible for?

Answer 9

level in brain affects mood

Question 10

What is endorphins responsible for?

Answer 10

pain regulation

Question 11

What is postsynaptic potentials?

Answer 11

change in membrane potential of postsynaptic cells

Question 12

What are postsynaptic potentials triggered by?

Answer 12

ligand gated ion channels

Question 13

What are the 2 types of postsynaptic potentials and what do they do?

Answer 13

excitatory postsynaptic potential: depolarizes

inhibitory postsynaptic potential: hyperpolarizes

Question 14

What happens during summation of postsynaptic potentials?

Answer 14

addition of all excitatory and inhibitory cells

Question 15

What happens during temporal summation?

Answer 15

2+ signals arrive at the SAME synapse

Question 16

What happens during spatial summation?

Answer 16

2+ signals arrive at the same time at DIFFERENT synapses on the same postsynaptic neuron

Question 17

What is neural plasticity?

Answer 17

capacity for the nervous system to be remodeled

Question 18

What do neurons do during development?

Answer 18

form more synapses than needed

Question 19

Where does STM take place and what happens during it?

Answer 19

hippocampus

forms temporary links with LTM which is essential for acquiring memories

Question 20

Where does LTM take place and what happens during it?

Answer 20

cerebral cortex

temporary links replaced with permanent connections

Question 21

What is LTP?

Answer 21

lasting increase in strength of synaptic transmission

Question 22

What 2 conditions must be met to establish LTP?

Answer 22

1 high frequency series of APs

2. Those APs arrive at terminal when postsynaptic nerve is already depolarized from another stimulus

Question 23

What are the 2 types of receptors in a postsynaptic neuron?

Answer 23

NMDA receptors

AMPA receptors

Question 24

What are NMDA and AMPA receptors? When do they open?

Answer 24

ligand gated ion channels

open when something specific binds to it

Question 25

What happens before LTP?

Answer 25

``` 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 ```

Question 26

How do we establish LTP?

Answer 26

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)

Question 27

What does the influx of Ca2+ cause?

Answer 27

it causes stored AMPA receptors to be embedded in the membrane

Question 28

What are the 2 types of sensory receptors and what do they do?

Answer 28

chemoreceptors: stimulus = specific molecules mechanoreceptors: stimulus = physical change

Question 29

What are the 4 basic steps of sensory processing?

Answer 29

1. sensory reception 2. sensory transduction 3. transmission 4. perception

Question 30

What is gustation?

Answer 30

sense of taste

Question 31

What are the sensory receptor cells for taste called?

Answer 31

taste cells

Question 32

What are the 5 tastant types?

Answer 32

``` sweet salty bitter umami sour ```

Question 33

What kind of receptors do taste cells have? Which tastants do they open?

Answer 33

g protein-coupled receptors | sweet, umami, bitter

Question 34

Which tastants open directly with ion channels?

Answer 34

sour | salty

Question 35

What happens if tastant is sweet, bitter, or umami?

Answer 35

GPCR activates G protein G protein activated adenylyl cyclase adenylyl cyclase converts ATP to cAMP cAMP opens Na+/Ca2+ channels

Question 36

What happens if tastant is sour or sweet?

Answer 36

binding opens channels directly

Question 37

Does everyone taste the same?

Answer 37

No, perception is unique to individuals

Question 38

What is olfaction?

Answer 38

sense of smell

Question 39

What is the biggest difference about olfaction and gustation?

Answer 39

sensory cells in the nose are ALSO the afferent neurons

Question 40

What are olfactory receptor cells? Where are they? What do they do?

Answer 40

sensory cells/neurons they line the upper nasal cavity odorants bind to cilia in nasal cavity send APs along axon to olfactory bulb in the brain