W7 Neurology and Neurocytology (watch recording for slides 11/12)

Question 1

what structures make up a typical neuron?

Answer 1

cell body, dendrites, axon, pre-synaptic terminals a myelin sheath and a nucleus

Question 2

what does the cell body do?

Answer 2

makes proteins essential for neuronal function

Question 3

what do dendrites do?

Answer 3

receive signals from other neurons

Question 4

what do axons do?

Answer 4

transmit electrical impulses to pre-synapatic terminals

Question 5

what do pre-synaptic terminals do?

Answer 5

transmit signals to adjacent cells

Question 6

what doe sthe myelin sheath do?

Answer 6

speeds up conduction

Question 7

what are the three types of neuroglial cells?

Answer 7

microglia, astrocytes and oligodendrocytes

Question 8

what do oligondendrocytes do?

Answer 8

form the myelin sheath (aka Schwann cells in the PNS)

Question 9

what do astrocytes do?

Answer 9

serve as a barrier between neurons and is important in development and inflammation (protoplasmic (grey matter) / fibrous (white matter))

Question 10

what are microglia responsible for?

Answer 10

responsible for cellular clearance after injury

Question 11

what do axons end in?

Answer 11

a synapse or neuromuscular junction in muscle

Question 12

axon terminal contains vesicles of neurotransmitters such as?

Answer 12

acetylcholine, noradrenaline, dopamine and serotonin

Question 13

as nerve impulses travel down axons, vesicles fuse with what?

Answer 13

pre-synaptic membranes

Question 14

what does a neurotransmitter diffuse across from and to?

Answer 14

diffuses from a synaptic cleft and interacts with a post-synaptic receptor

Question 15

neurons have a resting potential but what happens when the threshold potential is reached?

Answer 15

the neuron will ‘fire’ - increased firing frequency increases intensity of the signal

Question 16

do excitatory neurons move the resting potential towards or away from the threshold?

Answer 16

towards - inhibitory neurons move it away from the threshold

Question 17

what are the 5 stages of action potential generation and propagation?

Answer 17

1. there is stimulus (must reach over -55mV (the threshold potential) otherwise the initiation will fail)
2. depolarisation occurs as sodium ions move in reaching an action potential of around +40mV
3. repolarisation occurs as sodium ions move out
4. hyperpolarisation occurs where the potential is below resting
5. resting potential is reached again at -70mV
   * this all happens in the space of few miliseconds

Question 18

what is a refractory period?

Answer 18

if a second stimulus is applied to a neuron less than 0.001 second after the first it will not trigger another impulse. The membrane is depolarised and this is known as the refractory period

Question 19

how does repolarisation occur?

Answer 19

it is first established by the opening of potassium channels and the facilitated diffusion of potassium out of the cell

Question 20

how does repolarisation occur?

Answer 20

it is first established by the opening of potassium channels and the facilitated diffusion of potassium out of the cell

Question 21

in some neurons the refractory period lasts only 0.001-0.002 seconds meaning that how many impulses can a neuron transmit per second?

Answer 21

500-1000

Question 22

what are the first 6 stages of a synaptic transmission?

Answer 22

1. uptake of the precursors
2. synthesis of transmitter
3. storage of transmitter in vesicles
4. degradation of surplus transmitter
5. action potential
6. influx of calcium

Question 23

what are the last 7 steps of a synaptic transmission?

Answer 23

7. release of the neurotransmitter
8. diffusion to post-synaptic receptors
9. interaction with postsynaptic receptors
10. inactivation of transmitter
11. reuptake of neurotransmitter
12. uptake of the neurotransmitter by non-neuronal cells
13. interaction with pre-synaptic receptors

Question 24

what is a neurotransmitter?

Answer 24

a chemical used for neuronal communication in the body, there are over 50 that have been identified and can be classified by chemical structure and functional role

Question 25

what functional roles can a neurotransmitter have?

Answer 25

excitatory or inhibitory

Question 26

what are EPSP and IPSP?

Answer 26

excitatory postsynaptic potentials and inhibitory postsynaptic potentials

Question 27

a single EPSP is unable to bring postsynaptic neuron to AP threshold, what will bring it it to the threshold?

Answer 27

the result of thousands of synaptic events from many neurones, via temporal or spatial summation

Question 28

describe temporal summation:

Answer 28

EPSPs last around 15ms, high frequency activation of a single presynaptic terminal can cause summation if the interval between pulses is less than 15ms

Question 29

describe spatial summation:

Answer 29

activation of multiple presynaptic terminals can cause summation

Question 30

what is botulinum toxin also known as, what does it do?

Answer 30

botox, blocks release of ACh

Question 31

what effect does myasthenia gravis have?

Answer 31

immune destruction of ACh receptors