Neurons

Question 1

what are neurons?

Answer 1

nerve cells

Question 2

where are neurons?

Answer 2

in the nervous system

Question 3

what are neurons specialised for?

Answer 3

communication

Question 4

what do neurons connect with?

Answer 4

other neurons and with other excitable cells

Question 5

what are the different parts of the neuron?

Answer 5

dendrites, cell body, axon and axon terminals

Question 6

where do the inputs go into in the neuron?

Answer 6

dendrites

Question 7

where do the signal outputs come from in the neuron?

Answer 7

axon terminals

Question 8

name the 6 different types of neurons

Answer 8

purkinje cell, spinal interneuron, sensory neuron, pyramidal cell, motor neuron and bipolar cell

Question 9

what is the resting membrane potential?

Answer 9

a potential difference across the membrane of all cells

Question 10

what is the value for the resting membrane potential?

Answer 10

20-90mV

Question 11

comment on the polarity of the membrane

Answer 11

polarised

Question 12

comment on the positive and negative charges on each side of the membrane

Answer 12

approximately equal numbers but not distributed evenly with the ICF negative to the ECF

Question 13

are sodium ions higher in the ECF or ICF

Answer 13

ECF

Question 14

are potassium ions higher in the ECF or ICF

Answer 14

ICF

Question 15

are chlorine ions higher in the ECF or ICF

Answer 15

ECF

Question 16

where does the resting membrane potential arise from?

Answer 16

the separation of charges on either side of the membrane

Question 17

what is the resting membrane potential determined by?

Answer 17

The diffusion of K+ from cell interior through K+ channels. The sodium potassium pump (3Na+ out and 2K+ in)

Question 18

how is the membrane potential altered?

Answer 18

applying an electric current to the cell

Question 19

what does a hyperpolarising current do?

Answer 19

moves the MP further from 0

Question 20

what does a depolarising current do?

Answer 20

moves the MP nearer to 0

Question 21

what happens if the MP is raised to -55mV

Answer 21

a large depolarisation occurs

Question 22

what is the action potential?

Answer 22

large change in MP

Question 23

what is the first action potential step?

Answer 23

stimulus applied, depolarisation and MP moves towards 0mV

Question 24

what is the second step of action potential?

Answer 24

MP reaches about -55mV, voltage-gated Na+ channels open, MP moves towards 0mV

Question 25

what is the third action potential step?

Answer 25

Na+ diffuse inwards through voltage-gated channels

Question 26

why does action potential occur?

Answer 26

the entry of Na+

Question 27

what is the fourth action potential step?

Answer 27

when MP reaches about +35mV the Na+ channels shut and K+ channels open for K+ to leave the cell making the MP more negative

Question 28

what is the fifth action potential step

Answer 28

after a small overshoot (hyperpolarisation) the MP returns to original resting level

Question 29

is the amplitude of the action potential dependent or independent of the stimulus?

Answer 29

independent

Question 30

what happens at the threshold of the action potential?

Answer 30

voltage-gated Na+ channels open and Na+ diffuse in (depolarisation)

Question 31

what happens at the peak of the action potential?

Answer 31

Na+ channels close, voltage-gated K+ channels open and K+ diffuse out (repolarisation)

Question 32

how do local anaesthetics stop nerve conduction?

Answer 32

by blocking the Na+ channels

Question 33

what is the refractory period?

Answer 33

the neuron cannot generate another AP until the first one has ended - the period of inexcitability

Question 34

what is the refractory period due to?

Answer 34

the inactivation of voltage-gated sodium channels

Question 35

what is AP propagation?

Answer 35

the AP in one section of the axon depolarises adjacent resting parts of the axon. The AP is regenerated further along the axon

Question 36

how do action potentials travel along the axon?

Answer 36

as waves of depolarisation

Question 37

what increases the AP propagation

Answer 37

the axon diameter

Question 38

do large or small axons conduct more rapid impulses?

Answer 38

large axons

Question 39

how is rapid conduction achieved?

Answer 39

only with very large axons

Question 40

what does myelination do?

Answer 40

greatly increases the AP conduction speed

Question 41

what is myelin

Answer 41

a fatty layer

Question 42

what is myelin formed by?

Answer 42

wrapping the membranes og glial cells round the axon

Question 43

what does myelin do?

Answer 43

insulates the axon and improves conduction

Question 44

what are nodes of ranvier?

Answer 44

interruptions in the myelin sheath

Question 45

what occurs at the nodes of ranvier

Answer 45

ion flow can occur