Review Flashcards
Depolarization of the nerve cell membrane occurs when there is a rapid inflow of
Sodium ions
When does an action potential occur
When the local potential reaches the threshold level
Continuous conduction of an action potential means that
One action potential stimulates the production of a new action potential at the adjacent site
Which of the following occurs in electrically excitable cells
Depolarization causes voltage gated sodium on channels to open
A specialized junction through which impulses pass from one neuron to another via chemical messengers ( neurotransmitters).
Synapse
Synaptic transmission sequence
- Ap causes release of neurotransmitter
- Neurotransmitters diffuse across the synaptic cleft
- Neurotransmitter binds with receptors on the post synaptic cell
- Membrane permeability to sodium ions on post synaptic cell increases
- Then sodium ion diffuse into the cell and cause a local potential.
A sensory neuron
Always release a neurotransmitter that excites the neurons
Neurons controlling muscles reflexes transmit AP quickly where as those controlling digestive secretions are slower.
Which neurons likely have myelinated axons and what type of AP conduction do they perform
Neurons controlling muscle reflexes
Saltatory conduction
Axons may be myelinated or unmyelinated
True
AP move along unmyelinated axons by
Continuous conduction
Voltage gates open and close sequentially along the entire length of the axon
True
AP travel down myelinated axons quickly by
Saltatory conduction
Ap potential are generated only at the nodes of ranvier, giving the appearance of an AP jumping from node to node
True
On a graph of an action potential the repolarization phase appears as a ……downward trend in the membrane potential, meaning it is quickly becoming more……
Steep
Negative
Repolarization is the second phase of an action potential
True
Repolarization involves a negative change in membrane potential because:
Sodium voltage gates close preventing further depolarization
Potassium voltage gates open fully allowing potassium to leave the cell
The exit of potassium returns the membrane toward-70 mV
On a graph of an action potential, the depolarization phase appears as a …… upward trend in the membrane potential, meaning it is quickly becoming more……
Steep
Positive
Action potential true statements
Sodium entered the cell as it diffused down its concentration gradient.
Entry of sodium through one channel stimulates the next channel to open.
The membrane potential depolarizes from-70 to +30 mV.
Why is the PSP from synapse 3 the only one to trigger an action potential? Assume the PSPs from all synapses are EPSPs of identical strengths
Signals from synapses 1 and 2 lose too much strength because they have farther to travel.
True statements about temporal summation
Individual EPSPs are too weak so multiple signals are needed to reach threshold.
The strength of each EPSP fades with time, so signals Mia occur in a quick succession.
True statements to generate IPSP
Cl- enters the cell, making the membrane potential more negative
K+ exit the cell, making the membrane potential more negative.
To generate an EPSP
Sodium enters the cell making the membrane potential more positive
Neurotransmitters bind to ligand gated channels causing them to open
True
The nervous system is the major communication and control center of the body
True
Nervous tissues contain neurons aka nerve cells that communicate with other body cells through electrical signals called
Action potential ( nerve impulses) and chemicals called neurotransmitters.
Multipolar neurons are the most common structural type of neuron have 100 of dendrites that receive incoming signals that are transferred toward the cell body.
A single axon transmits the nerve impulse or action potential
Two types of graded post synaptic potentials
EPSP excitatory which occurs in response to the opening of specific ligand gated ion channels in the membrane resulting in a increase of sodium into the cell causing depolarization
Second type is inhibitory IPSP which occurs when either ligand gated potassium or chloride channels open, depending on the specific neurotransmitter. This allows for influx of potassium or chloride resulting in hyperpolarization of the membrane.
Multiple grades pSP are received at the dendrites and cell body.
They determine the resulting response of the neuron
Threshold is -55 mV
If threshold is met then an action potential is generated
Temporal summation
Occurs as multiple signals are sent from the same presynaptic terminal in a rapid fire fashion
Spatial summation
R/t the proximity of the multiple postsynPtic potentials to each other and their relative distance to the axon hillock.
Once threshold has been reached, voltage gated sodium channels within the trigger zone opens, allowing sodium to enter the cell causing depolarization and begin the propagation of the action potential 
Depolarization
Voltage gated potassium channels open slowly during the rise of the AP, allowing an efflux of potassium. The combination of closing voltage gated sodium channels and opening potassium voltage gated channels results in
Replorization of the membrane towards -70mV
Towards the end of repolarization the voltage gated potassium channels starts to close slowly causing and overshoot making the membrane more negative
Hyperpolarization
RMP is re established through the redistribution of ions by the sodium potassium pump and leakage channels
Time period when the voltage gated sodium channels are inactivated and no new AP can occur
Absolute refractory period
