Lecture 10 Synapses and Synpatic function

Question 1

what is a Synapse

Answer 1

site of communication between neurons

Question 2

what are the components of synapse

Answer 2

1. presynaptic neuron
2. post synaptic neuron
3. synaptic cleft

Question 3

What is Presynaptic Neuron Structure

Answer 3

• Axon terminal
• contains synaptc vessicles
• contain voltage gated channels

Question 4

what is the presynaptic function ?

Answer 4

transmit signal

Question 5

what are synaptic vessicles

Answer 5

hold the neurotransmitters

Question 6

what is the Postsynaptic neuron structure

Answer 6

usually dendrites or soma

contain receptors for NT

Question 7

what is the function of the postsynaptic neuron

Answer 7

receives the signal

Question 8

what is the structure of the synaptic cleft?

Answer 8

narrow extracellular space between neurons

Question 9

what is the function of synaptic cleft ?

Answer 9

allow diffusion of NT

Question 10

communication steps across a synapse

Answer 10

1. Action potential arrives at axon terminal
   2 voltage gated Ca+ channels open
2. Ca2+ flows in –> exocytsis of synaptic vessicles
3. NT diffuse across cleft –> bind to receptors
4. Postsynaptic cell responds
5. response is stopped when NT is removed from cleft
   - degradation
   - reuptake
   -diffusion

Question 11

what are the effects of Neurotransmitters

Answer 11

Change membrane potential in postsynaptic cell

1. excitatory
2. inhibitory

Question 12

what is Excitatory

Answer 12

Excitatory Postsynaptic Potential (EPSP)
Depoloarizing
NT bind to receptors triggering
-Na+ channels open
-Na+ moves into the cell–> depolarizing
Moves membrane potential closer to threshold

Question 13

What is Inhibitory

Answer 13

Inhibitory Postsynaptic potential (IPSP)
Hyperpolarizing
-NT binds receptors triggering
1. k+ channels open –> K+ moves out of the cell –> hyperpolarizing
2. Cl- channels to oopen
- Cl- move into the cell —> hyperpolarize
move the membrane potential further from threshold
-membrane stabilizes

Question 14

what is divergence

Answer 14

one presynaptic neuron–> several post synaptic neurons

Question 15

What is convergence

Answer 15

several presynaptic heuronss—> one post synaptic neuron

Question 16

what are graded potentials

Answer 16

small changes in membrane potential due to ion channels opening/closing in response to stimuli

Question 17

what are the properties of graded potentials

Answer 17

1. graded
2. decremental
3. depolarizing or hyperpolarizing
4. summation

Question 18

what is graded

Answer 18

change in membrane potential reflects strenght of stimulus

• weak stimuli–> small change
• strong stimuli–> large change

Question 19

what is decremental

Answer 19

change dissipates with distance from the stimulus

Question 20

What is depolarizing and hyperpolarizing

Answer 20

IPSP= hyperpolarizing 
EPSP= depolarizing

Question 21

what is summation

Answer 21

can combine effects of stimuli

1. add
2. cancel

Question 22

what are the types of summation

Answer 22

temporal: same stimulus
repreated close together in time

spatial: different stimuli
overlap in time

Question 23

what is the purpose of graded potentials

Answer 23

graded potentials determine if an action potential will ocurr or not

Question 24

what is the rule of graded potentials

Answer 24

if the membrane potential at the axon hilock depolarized above the threshold –> AP