Nervous System Activities: Graded and Action Potentials

Question 1

What are changes in the membrane potential?

Answer 1

• Pieces of information/messages.
• response to temporary changes in membrane permeability.
  Resulting from opening or closing of specific membrane channels.

Question 2

What are the two types of membrane channels responsible for the changes in membrane potential?

Answer 2

• Passive channels - leak channels: are always open and ions move via diffsuion, membrane permeability changes in response to the envrionment
• Active channels - gated channels: open and close in response to specific stimuli, at resting potential most gated channels are closed.

Question 3

What are the three types of Active (gated) channels?

Answer 3

• Voltage gated - change in charge
• Chemically gated - ligand binds to receptor
• Mechanically gated - change in structure of the gate

Question 4

Process of neurotransmission from the start (simple).

Answer 4

• Chemical stimulus activated chemically gated sodium channels, creating a graded potential
• graded potential truns into a action potential
• action potential triggers calcium influx into presynaptic cell
• calcium ions trigger neurtotransmitters to undergo exocytosis
• exocytosis occurs, neurotransmitters bind to complementary receptors
• transmission occurs to post synaptic cell.

Question 5

Steps of the resting membrane potential -> graded -> action.

Answer 5

• resting membrane potential -70mili volts
• depolerization - +30 mili volts
• repolerization -70 mili volts
• restering membrane potential -70 mili volts
• hyperpolerization -90 mili volts
• return to resting membrane potential -70 mili volts

Question 6

Difference btween a graded potential and action potential.

Answer 6

• graded: small, local, and temporary change in membrane potential - activated by a weak stimuls - won’t turn into an action potential and won’t be able to relay the message as far.
• action: past -55mili/volt threshold - action potential is signalled and starts at the axon hillock and reaches axon terminal
• wide-spread, activated by a strong stimulus and carries information furthe,r from neuron to neuron.

Question 7

How do you generate an action potential? - full process

Answer 7

• at resting membrane potential, voltage-gated sodium and potassium ion channels are closed.
• depolerisation: stimulus creates a graded potential (-60/-55mili volts) and voltage gated sodium channels open. Sodium rushes into the cell via diffusion from leak channels and inside the cell becomes more positive (+30 mili volts) - rapid depolerization. Then voltage gated sodium ion channels close and the sodium ion channel becomes innactivated. Voltage gated potassium channels open and potassium moves out of the cell. Inside the cell becomes neagtive - repolerisation begins.
• repolerisation: voltage-gated potassium channels close as resting membrane potential is reached, resulting in the slow, continual movement of potassium ions out of the cell causing a brief hyperpolerization.
• Hyperpolerisation: sodium and potassium voltage gated channels are closed and resting membrane potential is restored by the movement of sodium and potassium through leak channels.

Question 8

What are nodes?

Answer 8

• Spaces between myelin sheath along the axon.
• action potentials are propogated from from node to node.