Neurology & Cytology

Question 1

what are neurons?

Answer 1

these are highly specialised cells of the brain and nervous system

Question 2

what do neurons communicate?

Answer 2

they communicate information in electrical and chemical form

Question 3

what is the broad classification of neurons?

Answer 3

glia

Question 4

dendrites - what do they do?

Answer 4

they receive signals from other neurones

Question 5

what does the cell body of the neuron do?

Answer 5

makes proteins which are essential for neuronal function

Question 6

what does the nucleus of the neuron do?

Answer 6

contains the genetic material (chromosomes) of neuron cell

Question 7

what does the axon hillock part of the neuron do?

Answer 7

plasma membrane generates the impulse

Question 8

what does the axon of the neuron do?

Answer 8

it conducts electrical impulses along the neuron cell

Question 9

myelin sheath of neuron?

Answer 9

insulate the axon to help protect the neuron cell and speed up transmission of electrical impulses

Question 10

what is the myelin sheath made up of?

Answer 10

schwann cells

Question 11

gap between schwann cells?

Answer 11

nodes of ranvier

Question 12

axon terminal of neuron?

Answer 12

transmits electrical and chemical signals to other neuron cells

Question 13

afferent neuron?

Answer 13

sends signal through axon - signal is processed at cell body of neurons and sent to axon terminals

Question 14

what does the motor division of PNS involve?

Answer 14

voluntary movement by skeletal muscles
AND
involuntary body responses, such as heart rate, blood pressure, respiration, digestion and sexual arousal

Question 15

sensory division of PNS includes?

Answer 15

vision, hearing, smell or taste, touch, pain and temp

Question 16

what do the Schwann cells (of PNS) and oligodendrocytes ( of CNS) do?

Answer 16

insulation and myelination

Question 17

what do satellite cells (of PNS) and astrocytes (of CNS) do?

Answer 17

for support of the neurons

Question 18

what do the microglia of the CNS do?

Answer 18

immune support, phagocytosis

Question 19

what do the ependymal cells of the CNS do?

Answer 19

creating CSF
cerebral spinal fluid

Question 20

myelin sheath is essential for?

Answer 20

for electrical insulation and to speed up action potential propagation

Question 21

what is the axon terminal designed to do?

Answer 21

to convert the electrical signal into a chemical signal in a process called synaptic transmission

Question 22

what do motor proteins do?

Answer 22

they ‘walk’ along the microtubules carrying material away from the soma (anterograde transport) or back to the soma (retrograde transport)

Question 23

what does an axon terminal refer to?

Answer 23

it refers to the axon endings that are somewhat enlarged and often club or button shaped

Question 24

what do axon terminals do that are part of a nerve cell?

Answer 24

they make synaptic connections with another nerve cell or with an effector cell

Question 25

what does an axon end in?

Answer 25

a synapse but it is a neuromuscular junction in muscle

Question 26

what does the axon terminal contain?

Answer 26

it contains vesicles of neurotransmitter e.g. ACh, noradrenaline, dopamine and serotonin

Question 27

as nerve impulses travel down axon - what happens?

Answer 27

vesicles fuse with pre-synaptic membrane neurotransmitter diffuses across synaptic cleft & interacts w/ post-synaptic receptor

Question 28

how do neurons send messages?

Answer 28

electrochemically meaning that chemicals (ions) cause an electrical signal the important ions in the nervous system are sodium and potassium

Question 29

At rest, describe the concentrations of Na and K:

Answer 29

a higher conc of Na+ is kept outside the cell and higher conc of K+ inside, creating a voltage difference called resting potential

Question 30

what happens to the Na+ and K+ conc when an impulse moves down an axon?

Answer 30

Na+ move into the cell, creating a reversal in voltage called an Action potential

Question 31

what happens when a second stimulus is applied to a neuron less than 0.001 second after the first?

Answer 31

it will not trigger another impulse the membrane is depolarised and the neuron is in its refractory period

Question 32

how is repolarisation first established?

Answer 32

by the opening of potassium channels and the facilitated diffusion of potassium ions (K+) out of the cell

Question 33

what happens to Na+ during repolarisation?

Answer 33

they are actively transported back out of cell

Question 34

in some neurones, how long can the refractory period last?

Answer 34

only 0.001-0.002 seconds - meaning that the neuron can transmit 500-1000 impulses per second

Question 35

What is happening during nerve conduction/signal transduction?

Answer 35

neurons have a resting potential the neuron 'fires' if a threshold potential is reached signalling - all or nothing increased frequency of firing increases intensity of signal excitatory neurons move the resting potential towards the threshold inhibitory neurons make resting potential more negative away from threshold

Question 36

in response to the signal (action potential) what happens to the soma end of the axon?

Answer 36

it becomes depolarised

Question 37

as the depolarisation spreads down the axon - what is happening?

Answer 37

the first part of the membrane repolarises Na+ channels are inactivated and additional K+ channels have opened, the membrane cannot depolarise again the action potential continues to travel down the axon

Question 38

what does an excitatory postsynaptic potential (EPSP) do?

Answer 38

increases the likelihood of a postsynaptic action potential occurring and are induced by excitatory neurotransmitters (Glutamate)

Question 39

what does an inhibitory postsynaptic potentials (IPSP) do?

Answer 39

it decreases the likelihood of a postsynaptic action potential occurring and are induced by inhibitory neurotransmitters (GABA)

Question 40

what is the postsynaptic response a result of?

Answer 40

possibly thousands of synaptic events from many neurones

Question 41

how is the postsynaptic neuron brought to action potential threshold?

Answer 41

via temporal or spatial summation

Question 42

spatial summation?

Answer 42

activation of multiple presynaptic terminals can cause summation

Question 43

temporal summation?

Answer 43

high frequency activation of a single presynaptic terminal can cause summation if interval between impulses < 15 msec

Question 44

botox?

Answer 44

botulinum toxin

Question 45

the formation of an action potential can be divided into 5 steps - what is the 1st step?

Answer 45

a stimulus from a sensory cell or another neuron causes the target cell to depolarise toward the threshold potential

Question 46

the formation of an action potential can be divided into 5 steps - what is the 2nd step?

Answer 46

if the threshold of excitation is reached, all Na+ channels open and the membrane depolarises

Question 47

the formation of an action potential can be divided into 5 steps - what is the 3rd step?

Answer 47

at the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close

Question 48

the formation of an action potential can be divided into 5 steps - what is the 4th step?

Answer 48

the membrane becomes hyperpolarised as K+ ions continue to leave the cell The hyperpolarised membrane is in a refractory period and cannot fire

Question 49

the formation of an action potential can be divided into 5 steps - what is the 5th step?

Answer 49

the K+ channels close and the Na+/K+ transporter restores the resting potential

Question 50

Describe how synapses function before an action potential occurs:

Answer 50

precursors are taken up and transmitters are synthesised. The transmitter is stored in vesicles and any surplus transmitter is degraded.

Question 51

Describe how a synapse functions, starting with an action potential:

Answer 51

Action potential Influx of Ca2+ and release of neurotransmitter which diffuses to the post-synaptic membrane This NT then interacts with postsynaptic receptors

Question 52

Once the neurotransmitter has interacted with the postsynaptic receptors - how does the synapse function?

Answer 52

inactivation of transmitter and then reuptake of neurotransmitter Uptake of neurotransmitter by non-neuronal cells which interact with pre-synaptic receptors

Question 53

how can neurotransmitters be classified?

Answer 53

by chemical structure e.g. ACh, dopamine by functional role e.g. excitatory/inhibitory

Question 54

what molecules are neurotransmitters typically?

Answer 54

typically small, rapid-acting molecules they are either excitatory e.g. glutamate, acetylcholine inhibitory e.g. GABA, glycine or others e.g. noradrenaline, serotonin, histamine, dopamine