Neural Impulse Transmission Flashcards
Julius Bernstein
Suggested that nerve impulses were an electrochemical message caused by the movement of ions through the membrane of a nerve cell.
Cole and Curtis
Helped find the evidence for Bernstein’s theory. They placed an electrode inside the large nerve cell of a squid and detected a change in the electrical potential difference when the nerve became excited.
Resting Membrane Potential
Nerve cell membrane is impermeable to the flow of ions, and the potential is around -70 mV. No impulse is generated.
Action potential
The reversal of potential from negative to positive when the nerve becomes excited, so an impulse is generated.
Plamsa membranes
Selectively permeable and is made up of a phospholipid bilayer.
Facilitated diffusion
A selective process from which ions can moves along the concentration gradient.
Polarized
Concentration of K+ ions is greater on the inside of neuron along with other negatively charged ions, and the concentration of Na+ ions is greater on the outside. Due to this, the inside has a negative charge and the outside has a positive charge.
Depolarization
Na+ ions enter, and the inside becomes positive and the outside becomes negative. Reversal of charge, so there is an action potential.
Repolarization
K+ diffuse out of the neuron, so the inside is negative and the outside is positive.
Hyperpolarizaton
Outside of the neuron is more positive than when it was at resting potential.
Sodium-potassium pump
3Na+ out and 2K+ in
Refractory period
The time taken for the membrane to return to resting potential after repolarization.
Another nerve impulse can’t be initiated until the neuron has been completely…
Repolarized
Threshold Level
The minimum level of stimulus required to produce an action potential.
All-or-none response
When the threshold level of a neuron has been reached, the action potential creates a full response. So increasing the intensity of a stimulus, will not increase the intensity of the action potential.
What are the 2 ways to increase the intensity of a stimulus?
Increase the number of neurons being stimulated and increasing the frequency of impulses being sent.
Wave of depolarization
Many action potentials are created one after another along the membrane.
Salutatory conduction
For myelinated axons, the action potentials are only generated at the nodes of Ranvier where the gated ion channels are located. Faster nerve transmission.
Neurotransmitter
Carry chemical signals from one neuron to the next. They can be excitatory or inhibitory.
Acetylcholine
Excitatory neurotransmitter that is made of an acetate molecule and choline. It causes the sodium channels to open and sodium to enter the neuron, so an action potential is generated due to depolarization.
Cholinesterase
An enzyme that breaks acetylcholine into acetate and choline molecules, which cleans the synapse and allows it to repolarize.
Inhibitory neurotransmitter
Prevents neutrons from becoming depolarized
Parkinson’s disease
Associated with inadequate levels of dopamine
Alzheimer’s disease
Associated with low levels of acetylcholine
Stimulants
Can mimic excitatory neurotransmitters, decrease the breakdown of neurotransmitters in the synapse, increase the number of neurotransmitters released into the synapse
Depressants
Can block receptor sites of neurotransmitters, decrease the number of neurotransmitters available, and increase the rate of neurotransmitter breakdown in the postsynaptic membrane.
Summation
Combined action of two or more neurons to create a stimulation for the brain.
Examples of excitatory neurotransmitters
Acetylcholine, dopamine
Examples of inhibitory neurotransmitters
Endorphins, GABA
Neurotransmitter that can be excitatory or inhibitory
Serotonin
Neurotransmitter that is excitatory and inhibitory
Norepinephrine
