Nerve impulse Flashcards
What surrounds neurons?
Plasma membrane
The plasma membrane is impermeable to ions.
What allows the movement of some ions in neurons?
Special channels
These channels may be open or closed.
What is the concentration of K+ inside a neuron compared to Na+ outside?
↑ [K+] inside; ↑ [Na+] outside
What is the resting state of a neuron characterized by?
Polarized membrane
What is the typical resting potential of a neuron measured in millivolts?
-70 mV
What happens to K+ during the resting state of a neuron?
Moves out due to concentration gradient
What causes the interior of a neuron to become more negatively charged?
Movement of K+ out of the cell
What initiates depolarization in an action potential?
Nerve stimulation causes Na+ gates to open
What occurs during repolarization?
Na+ gates close; many K+ gates open
What restores the resting membrane potential?
Na+/K+ pump
Moves 3 Na+ out and 2 K+ in using ATP.
What is saltatory conduction?
Action potentials jump from node of Ranvier to node of Ranvier
What does the ‘All or None’ response refer to in neurons?
Neurons fire maximally or not at all
What does an increase in neuronal stimulation beyond a critical level result in?
No increase in response
How do neurons respond to increased stimulation?
By increasing frequency of firing
What is the threshold level?
Minimum strength of stimulation required to produce an action potential
What is the space called between neurons where communication occurs?
Synapse
How is the message transmitted between neurons?
By release of chemical messengers
What are neurotransmitters?
Chemicals in the end plates of axons
What role does acetylcholine play in synaptic transmission?
Excitatory; makes post synaptic membrane more permeable to Na+
What does cholinesterase do?
Destroys acetylcholine
What happens when inhibitory neurotransmitters are released?
Post synaptic membrane becomes more permeable to K+
What is the result of hyperpolarization in neurons?
Prevents post synaptic neurons from becoming active
What is required for the production of an action potential in neuron D?
The sum of two excitatory neurons
