Membrane Potential and Action Potential

Question 1

how do neurons communicate

Answer 1

-they receive, process and transmit information via ‘electrochemical signalling’ communicating via synapses

Question 2

where do the electrochemical signals travel?

Answer 2

The electrochemical signal is recieved at the dendrites, which travels to cell body, along the neuron to the axon terminals

Question 3

name the 5 stages of action potential

Answer 3

1.stimulus
2.depolarization
3.repolarization
4.hyperpolarization
5.resting rate

Question 4

list the components of the neuronal membrane

Answer 4

phospholipid bilayer-barrier to isolate the cytosol from extracellular fluid

transmembrane protein-control passage of ions in/out of neuron

the neuronal membrane is semi-permuable

Question 5

discuss the membrane potential at rest

Answer 5

-(-70mV)
-voltage gated channells closed
-high k+ inside cell,
-high Na+ outside cell

Question 6

discuss depolarised membrane

Answer 6

-membrane potential becomes less negative
-voltage gated Na+ channels open
-Na+ moves into cell

Question 7

discuss repolarisation/hyperpolarisation

Answer 7

-voltage gated Na+ channels close
-delayed opening of voltage gated K+ channel
-K+ moves out of cell
-hyperpolarisation

Question 8

discuss the dendrites of neuron

Answer 8

-component of synapses (postsynaptic membrane) -receptors
-high number of spines meaning high neuronal activity
-spines are dynamic and can change shape-actin cytoskeleton-microfilaments
plasticity-role in learning and memory

Question 9

name the 3 types of dendrites

Answer 9

thin
stuby
mushroom

Question 10

define the following
-axon hillock
-initial segment
-AP conduction velocity

Answer 10

1-site of summation of EPSP’s and IPSP’s from synapses

2-action potential generation

3-axon diameter and myelin

Question 11

describe the components of axonal terminal

Answer 11

-cytoplasm of axon terminal has lost mitochondria

-presynaptic terminal is the site of neurotransmitter release

-presence of synaptic vesicles within terminal and proteins involved in NT release

Question 12

explain the process of synapic transmission

Answer 12

Synaptic transmission is the process by which nerve impulses are transmitted from one neuron to another across a synapse.

1. Action Potential Arrival: An action potential (electrical signal) reaches the presynaptic terminal of the neuron.
2. Neurotransmitter Release:
   o The action potential triggers the opening of voltage-gated calcium channels.
   o Calcium ions influx into the presynaptic terminal.
   o This triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft.
3. Neurotransmitter Binding:
   o Neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane.
4. Postsynaptic Potential:
   o Binding of neurotransmitters to receptors causes ion channels to open or close, leading to a change in the membrane potential of the postsynaptic neuron.
   o This can be either excitatory (depolarization) or inhibitory (hyperpolarization).

Signal Termination: o Neurotransmitters are removed from the synaptic cleft by:
▪ Reuptake into the presynaptic neuron
▪ Enzymatic degradation
▪ Diffusion away from the synapse