Neurons, Synaptic Transmission & Neurotransmitters

Question 1

what is a neuron

Answer 1

basic building block of the nervous system. They are nerve cells that process/transmit messages through electrical/chemical signals

Question 2

what are neurotransmitters

Answer 2

brain chemicals released from synaptic vesicles. Relay signals from one neuron to another across a synapse. Can be divided into those that perform an excitatory function or inhibitory function

Question 3

what is synaptic transmission

Answer 3

neighbouring neurons communicate by sending chemical messages across synapse

Question 4

what are the 7 features of the neuron

Answer 4

dendrite
soma (cell body)
nucleus
myelin sheath
node of ranvier
axon
axon terminal
axon hillock

Question 5

function of dendrite

Answer 5

receives messages from other neurons which trigger an action potential (electrical impulse) in cell

Question 6

axon hillock function

Answer 6

where nerve impulse is triggered from

Question 7

axon function

Answer 7

extension of cell body, passes electrical impulse towards the axon terminals

Question 8

axon terminal function

Answer 8

passes nerve impulses from cell body to parts of the body that they control or activate e.g. another neuron

Question 9

soma (cell body) function

Answer 9

houses genetic material from a neuron

Question 10

myelin sheath function

Answer 10

provides insulating layer to axon; helps speed up rate of message transmission

Question 11

nodes of ravier function

Answer 11

gaps between the cells along the myelin sheath

Question 12

explain the sensory neuron

Answer 12

carry messages from sensory receptors (e.g. touch and temp-sensitive receptors in skin) along nerves in peripheral nervous system to central nervous system

has long dendrites, short axons

Question 13

explain the motor neuron

Answer 13

carry messages from CNS ,along nerves in PNS, to effectors (e.g. muscles and glands)

has short dendrites, long axons

Question 14

explain the relay neuron

Answer 14

connect sensory and motor neurons together. Connect other relay neurons too

has short dendrites, short axons, ONLY found in CNS

Question 15

Neuron in resting state?

Answer 15

inside of cell negatively charged relative to outside

Question 16

neuron activated by a stimulus?

Answer 16

inside of cell becomes positively charged for split second

Question 17

what is the switch in charge from a neuron in resting to active state called? what does it create?

Answer 17

depolarisation - creates action potential, AP (electrical impulse)

Question 18

what does the action potential do once created?

Answer 18

travels down axon towards the terminal buttons of neuron (firing an AP)

Question 19

when is AP generated?

Answer 19

once depolarisation reaches a certain threshold, always the same intensity regardless of sizeof stimulus

if threshold not reaches, no AP

Question 20

capability of most myelinated neurons?

Answer 20

up to 500 AP’s a second

Question 21

how does neuron communication generally work?

Answer 21

neurons communicate within neural networks, separated by synaptic cleft (tiny gap)

signals WITHIN neurons transmitted ELECTRICALLY, signals BETWEEN neurons transmitted CHEMICALLYs

Question 22

ynaptic transmission?

Answer 22

chemical process using biochemical substances called neurotransmitters

Question 23

how are neurotransmitters released?

Answer 23

when AP reaches end of neuron called the presynaptic terminal button, its release is triggeres from synaptic vesicles

Question 24

explain when neurotransmitter molecules cross the gap

Answer 24

they fit into matching receptor sites on postsynaptic neuron, where there are different receptors for different neurotransmitters. The chemical signal that they carry is converted back into electrical signal in postsynaptic neuron - may fire another AP

Question 25

explain when neurotransmitter molecules remain in the synapse

Answer 25

reabsorbed into presynaptic neuron, usually broken down first - process is called reuptake, meaning neurotransmitters can be used again

Question 26

where have neurotransmitters been identified?

Answer 26

brain
(some) glands
spinal cord

Question 27

describe how neurotransmitters are unique

Answer 27

each has own specific molecular structure, fitting into specific type of postsynaptic receptor. Specific functions e.g. acetylcholine found where motor neuron meets a muscle, where upon its release, will cause the muscle to contract

Question 28

why do neurotransmitters fall in 2 main categories? what are they?

Answer 28

depending on effect to neighbouring neurons

inhibitory and excitatory

Question 29

example explanation of an inhibitory neurotransmitter?

Answer 29

serotonin causes inhibition in postsynaptic neuron, making it more negatively charges and less likely to fire

Question 30

inhibitory definiton

Answer 30

preventing or hindering an action

Question 31

excitatory definition

Answer 31

having an effect, exhibiting

Question 32

example explanation of an excitatory neurotransmitter?

Answer 32

dopamine causes excitation of the postsynaptic neuron by increasing its positive charge, making it more likely to fire

Question 33

explain summation

Answer 33

a postsynaptic neuron can receive inhibitory or excitatory inputs from a neural network, wherby firing depends on summation of signals over time - (TEMPORAL SUMMATION)
or space - (SPATIAL SUMMATION)

Question 34

describe how summation works

Answer 34

the excitatory and inhibitory influences are summed, whereby if the net effect on postsynaptic neuron is inhibitory, then it is less likely to fire
WHEREAS
if the net effect is excitatory, the postsynaptic neuron is more likely to fire, whereby the inside of this neuron will momentarily become positively charged

Question 35

what happens when the net effect on the postsynaptic neuron is excitatory?

Answer 35

depolarisation takes place, the AP travels down the dendrite towards the cell body, then along the axon

Question 36

what does the term “net” mean?

Answer 36

remaining, after the deduction of all charges