Neuro 2 Flashcards
Simple diffusion is a type of ____ transport
passive transport
- do not consume energy
Small uncharged molecules pass the lipid bilayer via _____
simple diffusion (passive) i.e. steroid hormones
Active transport requires
ATP (energy) because it is moving substances against their electrochemical gradient
All cells in the body have potential difference/voltage across membrane. What is this called?
resting membrane potential
What is the resting membrane potential in neurons?
-70 mV
all cells -ve inside
What is necessary in terms of electrical activity in axons to conduct an electrical signal in neurons?
- voltage gated ion channels
- channels open and realse change in membrane potential of the cell
What are action potentials?
signals that go along nerve from one place to another
- momentary discharges (depolarizations) of resting membrane potential
- caused by rapid influx of Na+ from opening of sodium ion channels
- once initiated, move along axon membrane towards synapse
What is the primary function of a nerve cell?
- receive, conduct and transmit signals
Signals travel long distances, what doe they do to keep the signal going?
- use voltage gated ion channels to continuously reamplify along the way
Explain the opening and closing of the ion channels with respect to action potentials.
- channel closed (resting membrane potential)
- gated channel opens in response to depolarization (action potential)
- gated channel closes
What does depolarization mean?
- cell becomes more positive than the resting potential (depolarize/hypopolarize)
With respect to ions, what is happening when the cell depolarizes? What happens to membrane potential?
- rapid influx of Na+
- explosive increase in Na+ permeability
- membrane potential from -70 to +30 mV
Where is there a rapid decrease in Na+ permeability?
- Na+ channels close
Due to the closing of Na+ channels closing, how does the cell compensate for all the positive charge inside?
- repolarize
- K+ (also positive) exits the cell
- inside less positive
The amplitude of action potentials are always the same. Why?
- amplitude peak = depolarization reaches the threshold
- action potentials are all or none
- must reach the maximum potential for the action potential to occur
Why doesn’t the membrane potential become more than 30mV?
- the Na+ channels close quickly and the K+ channels open (to compensate)
In non-myelinated axons, the action potential passes _______
- smoothly,
all parts of membrane are depolarized
What are myelinated conductions called?
saltatory conduction
How do action potentials move in saltatory conduction?
- nodes of ranvier (non-insulated parts)
- action potentials jump between
- rapid movement of action potentials,
- need less energy to restore membrane after action potential transmitted
What does the refraction period do?
- helps ensure the action potential only goes in one direction down the axon (occurs in the nodes of ranvier after it has jumped)
- i.e. repolarize
The end of a neuron is called the _____
synapse
In the CNS, the 2nd cell is a ____
neuron
In the PNS, the second cell is ____
a neuron effector cell (in muscle/gland)
A terminal bouton is found in the ____ neuron
presynaptic neuron
part of the synapse
- releases the NT
