✓ Neurons & Synaptic Transmission (AO1)

Question 1

Describe the structure of a Neuron?

Answer 1

__ / dendrite
/ \ / cell body
| . |/ nucleus
\__/
|
gap = nodes of ranvier
|
myelin sheath
| schwann cells
|
axon
|
—-|—-
/ | \
/ | \
/ | \
. . . axon terminals

Question 2

Function of dendrites?

Answer 2

branch-like + receive signals from other neurones

Question 3

Function of cell body?

Answer 3

contains the nucleus

Question 4

Function of nucleus?

Answer 4

contains genetic material

Question 5

Function of axon?

Answer 5

long slender fibre that carries nerve impulses away from the cell body

Question 6

Function of schwann cells?

Answer 6

form myelin sheath

Question 7

Function of myelin sheath?

Answer 7

protects the axon so that the electrical impulses travel faster along the axon

Question 8

Function of nodes of ranvier?

Answer 8

gap in the myelin sheath - speeds up the transmission

Question 9

Function of axon terminals?

Answer 9

at the end of the axon, contains neurotransmitters (stored in vesicles)

Question 10

What are Hormones?

Answer 10

produced by endocrine gland
released into bloodstream
takes longer time to have an effect
widespread effects around the body

Question 11

What are Neurotransmitters?

Answer 11

released by nerve terminal
released into synapse
has an immediate effect
direct effect to next neuron

Question 12

Function/Structure of sensory neuron?

Answer 12

carries impulses from the PNS receptors to CNS ,sometimes only spinal cord (no brain) = reflex actions

long dendrites, short axons

Question 13

Function/Structure of relay neuron?

Answer 13

carries impulses from sensory neurons to motor neurons - allows them to communicate (relay neurons only in CNS)

short dendrites, short axons

Question 14

Function/Structure of motor neuron?

Answer 14

carries impulses from CNS to effector (e.g. muscles or glands)

short dendrites, long axons

Question 15

Describe the Structure of a synapse?

Answer 15

/ \ axon
/ \
/ \ nerve impulse |
/ \ \/
/ \
/ \
/ - . \ synaptic knob
/ . - \ vesicles .
/ . - . \ mitochondria -
—————
synapse
......_ postsynaptic receptor sites

Question 16

Step 1 of synaptic transmission?

Answer 16

action potential travels down the axon of the pre-synaptic neuron

Question 17

Step 2 of synaptic transmission?

Answer 17

vesicles release neurotransmitter into synaptic cleft (synapse)

Question 18

Step 3 of synaptic transmission?

Answer 18

neurotransmitters bind to post synaptic receptors & take an effect

Question 19

Step 4 of synaptic transmission?

Answer 19

excess neurotransmitters are taken up by the pre-syn neuron re-uptake pump
(vesicles are replenished w new + reused neurotransmitter)

Question 20

Step 5 of synaptic transmission?

Answer 20

enzymes are released to break down the remaining neurotransmitter

Question 21

Step 6 of synaptic transmission?

Answer 21

summation

Question 22

Role of neurons in synaptic transmission?

Answer 22

neurons must transmit info both within the neuron & from one neuron to the next
+
an elec signal called an action potential transmits info within a neuron, down the axon to the axon terminals
+
once an action potential reaches the axon terminals the signal has to be passed onto the next neuron - this is done via synaptic transmission
+
st, which passes the signal over the synaptic gap between the 2 neurons through a chemical process

Question 23

Action Potentials?

Answer 23

when a neuron is in a resting state the inside of the cell is - charged compared to the outside
+
when a neuron is activated by a stimulus the inside of the cell becomes + charged for a split second
+
this causes an action potential to occur
+
this creates an elec impulse that travels down the axon towards the end of the neuron

Question 24

Summation?

Answer 24

whether or not the next neuron fires another action potential & continues the message depends on summation
+
if there is more of a + charge (excitatory NTs) than a - charge (inhibitory NTs) = the action potential will fire
+
if there is more - than + the action potential will not fire

Question 25

Excitation?

Answer 25

NTs that are excitatory cause the receiving neuron to be more likely to fire e.g. dopamine
+
known as “on switches” - cause excitation of the post-synaptic neuron by increasing its positive charge

Question 26

Inhibition?

Answer 26

NTs that are inhibitory cause the receiving neuron to be less likely to fire e.g. seretonin
+
known as “off switches” - cause inhibition of the post-synaptic neuron by increasing its negative charge, making it less likely to fire