excitable cells

Question 1

what determines the condition velocity

Answer 1

• degree of myelination
• axon diameter
• temperature

Question 2

dendrites

Answer 2

receive an input

Question 3

axon

Answer 3

transfer input

Question 4

output zone

Answer 4

release neurotransmitters

Question 5

what determines the membrane potential

Answer 5

• concentration of ions, at rest more na+ outside and more K+ inside
• permeability of membrane
• activity of the pumps

Question 6

what is the neurone resting potential

Answer 6

-30mV to -90mV

Question 7

resting potential

Answer 7

• K+ leaks out of K+ channels
• Na+ leaks in at the same time
• this charge will reach equilibrium and stop movement
• membrane is more permeable to K+ so move positive goes out
• Na+/K+ pump maintain gradient, 3Na+ out for 2K+ in

Question 8

graded potential

Answer 8

• there is a stimulus to the membrane
• dissipates through the neurone
• it does not have the capacity to reach threshold to trigger an action potential
• spreads by passive current flow
• are dependent on strength and duration of trigger event

Question 9

action potential

Answer 9

• continues to be generated down the axon
• Na+ channels open so sodium comes in making it more positive
• once threshold is reaches sodium gates close
• potassium channels then open so potassium moves out
• leads to repolarisation

Question 10

stages of action potential

Answer 10

depolarisation > repolarisation> hyperpolarisation

Question 11

what is the purpose of the refractory period

Answer 11

• so action potential is propagated in one direction
• inactivation gates can’t be opened by another stimulus
• activation gates once blocked can be opened by another stimulus

Question 12

types of refractory periods

Answer 12

• absolute refractory period
• relative refractory period

Question 13

synaptic transmission stages

Answer 13

• action potential down axon reaches axon terminal
• depolarises the presynaptic terminal
• opens voltage gated calcium channels
• signals neurotransmitter vesicles
• vesicles move to down membrane
• released via exocytosis
• attach at the post synaptic membrane
• neurotransmitter removed

Question 14

what happens to the calcium channels when neurotransmitters are released

Answer 14

• voltage dependent calcium channels open
• influx aids the formation of the docking complex’s

Question 15

what happens at the neuromuscular junction

Answer 15

• calcium comes in
• neurotransmitter released
• binds to receptor
• neurotransmitter is always Ach
• causes potential
• triggers release of calcium from cytoplasmic reticulum
• neurotransmitter eliminated in the synaptic cleft

Question 16

excitary event

Answer 16

opens sodium channels, increase membrane potential
- depolarising post synaptic potential

Question 17

inhibitory event

Answer 17

opens chloride channels or opens potassium channels
- hyperpolarising post synaptic potential

Question 18

spatial summation

Answer 18

potentials from different dendrites receiving different potentials at the same time

Question 19

temporal summation

Answer 19

receive signals close together in time (only 1)

Question 20

excitatory synapses

Answer 20

• promote action potential
• open sodium channels
• close the chloride and potassium channel
• upregulate number of receptors on post synaptic membrane

Question 21

inhibitory synapses

Answer 21

• opening of chloride ion channels
• opening potassium channels
• close of sodium channels
• activation of receptor enzymes

Question 22

is acetylcholine excitatory or inhibitory

Answer 22

• can be both excitatory and inhibitory
• excitatory in skeletal muscles
• inhibitory in heart
• depends on the receptors

Question 23

how does an action potential start

Answer 23

• exitatory post synaptic potential rises high enough
• begins where the initial segment of axon where the axon leave the neuronalsome

Question 24

how do neurotransmitters work

Answer 24

• synthesis and stored in the neurone
• released from the presynaptic ending of the neurone in response to stimulus
• binding and recognition when neurotransmitter bind to post synaptic target cells