Neural Tissue and Physiology Part 2 (End of Exam 3) Flashcards
How does sodium flow into the cell if the membrane is so impermeable to it?
Opening of specific membrane channels
What are the 2 types of gated membrane channels?
Voltage gated and chemically gated
Where are chemically gated channels found?
Soma
Where are voltage gated channels found?
Axon
Leak channels that are always open
Passive channels
Gated channels that ope and close in response to stimuli
Active channels
Are active channels ope or close at resting potential?
Closed
Variable strength electrical signals that travel over short distances and lose strength as they travel away from the source
Graded potential
What causes a graded potential?
Opening and closing of gated channels
What are graded potentials used for?
Short distance communication in neurons
Where do graded potentials occur? (3)
Dendrites, somas, synaptic terminals
The greater the stimulus the ____ changed in transmembrane potential and ____ area affected
More, more
What are graded potentials at opposite ends of cells linked by?
Action potential
Large uniform electric signals that can travel great distance without losing strength
Action potential
What causes action potentials?
Opening and closing of voltage gated channels when threshold potential is reached
Where do action potentials occur?
Axons
Action potential is triggered or not; only occurs when threshold is reached
All or none
What is the threshold level of voltage gated sodium channels
-60 to -55 mV
What is the 1st step in producing an action potential?
Graded depolarization brings an area of excitable membrane to threshold
What is the 2nd step in producing an action potential?
Activation of sodium channels causes rapid depolarization, Na+ rush into the cytoplasm, inner membrane changes from negative to positive
What is the 3rd step in producing an action potential?
Closing of sodium gated channels, opening of potassium gated channels; repolarization
What is the 4th step in producing an action potential?
Potassium channels close when membrane reaches resting potential, membrane is hyperpolarized to -90 mV and returns to resting potential
What are the 2 types of propagation?
Continuous, saltatory
Unmyelinated axons in propagation?
Continuous
Myelinated axons in propagation?
Saltatory
Direct physical contact between cells
Electrical synapses
Signal transmitted across a gap by chemical neurotransmitters
Chemical synapses
What determines whether an action potential may or may not be propagated to the postsynaptic cell?
Amount and type of neurotransmitter released
Neurotransmitters that cause depolarization of postsynaptic membrane, promotes action potentials
Excitatory
Neurotransmitters that cause hyperpolarization of postsynaptic membranes, suppress action potentials
Inhibitory
What does the effect of a neurotransmitter depend on ?
Receptor
Any synapse that releases ACh
Cholinergic synapse
Graded potentials developed in a postsynaptic cell in response to neurotransmitters
Postsynaptic potentials
Graded depolarization of postsynaptic membrane
Excitatory postsynaptic potential
Graded hyper polarization of postsynaptic membrane
Inhibitory postsynaptic potential
Repeated stimuli at one synapse
Temporal summation
Many stimuli arrive at multiple synapses
Spatial summation
