THE SYNAPSE

Question 1

what is a synapse

Answer 1

The junction between one neuron and another neuron/muscle/gland

Question 2

electrical synapse

Answer 2

• Direct connection between
two neurons
• Conduct electrical signals
faster
• Bi-directional

it is found in the neural system that requires the fastest possible response such as defensive reflexes

there are gap junctions that directly allow the movement of ions from one neuron to another

rarely in humans

Question 3

chemical synapse

Answer 3

• Chemical messenger transmits
information across space
separating the 2 neurons

• Axon terminal form part of the
pre-synaptic neuron

• Dendrites form part of the postsynaptic neuron

separated by a synaptic cleft

common in humans

unidirectional

Question 4

presynaptic terminal

Answer 4

1. Voltage-gated
   Na+ channel
2. Voltage-gated
   Ca2+ channel
3. synaptic vesicle with neurotransmitter

Question 5

postsynaptic terminal

Answer 5

1. receptors for neurotransmitter, which are a ligand-gated channel for Na, K, Cl, Ca

Question 6

what happens at the presynaptic terminal

Answer 6

1. action potential reaches the axonal knob and causes voltage-gated Na channel to open, the influx of Na occurs which cause the membrane to be more positive thus depolarizing it
2. Depolarisation triggers
   opening of Ca2+ voltage-gated
   channels and Ca2+ enters the cell
3. Ca2+ entry triggers exocytosis
   of synaptic vesicle content

Question 7

what happens at the synaptic cleft

Answer 7

4. Neurotransmitter diffuses
   across the synaptic cleft and
   binds with the receptors on the
   postsynaptic terminal

Question 8

what happens at the postsynaptic terminal

Answer 8

5. Depolarising/hyperpolarising
   postsynaptic (graded) potentials
   allows the influx/efflux of certain
   ions

Question 9

presynaptic terminal is made up of

Answer 9

the terminal axon of one neuron

Question 10

the postsynaptic terminal is made up of

Answer 10

dendrite or cell body of one neuron

Question 11

Excitatory postsynaptic potential

Answer 11

• Neurotransmitter binding
to receptor causes
opening of ligand-gated
Na+ or Ca2+ channels

• Net movement of
positive ions into the cell

• Depolarisation

Question 12

Inhibitory postsynaptic potential

Answer 12

• Neurotransmitter binding to
receptor causes opening of
ligand-gated K+ and Cl channels

• K+
flows out of the cell, Clflows
into the cell (down a concentration
gradients)

• Hyperpolarisation

Question 13

summation- Subthreshold

Answer 13

If EPSP input is
stimulated and it is
stimulated a second time
after the first EPSP has
died off, no summation
occurs

Question 14

summation- temporal summation

Answer 14

Summation of several
EPSPs occurring close
together from the same
neuron

Question 15

spatial summation

Answer 15

Summation of
several EPSPs
originating
simultaneously
from several
presynaptic inputs