Nervous System Physiology Flashcards
(53 cards)
bundles of peripheral nerve fibers held together by several layers of connective tissue
nerves
bundles of nerve fibers within the CNS
tracts
neurons exhibit both _____ and ______.
excitability and conductivity
signals initiated and conducted by neurons
nerve impulses
The difference in electrical charge due to excess of (+) ions on the outside of the membrane and an excess of (-) ions on the inside of the membrane
membrane potential
The membrane potential maintained by a non-conducting neuron’s plasma membrane
resting membrane potential (RMP)
The light excess of (+) ions on a membrane’s outer surface is produced by (2):
- ion transport mechanisms
2. selective permeability of the membrane
One mechanism that is very important in maintaining the RMP is the ____________.
Sodium-potassium pump
an active transport mechanism in the plasma membrane that transports sodium (Na+) and potassium ions (K+) in opposite directions and at different rates
sodium-potassium pump
the sodium-potassium pump transports ____ ions out of cells and ____ ions into cells
sodium (Na+), potassium (K+)
the sodium-potassium pump changes shape and releases # ____ to the outside of the cell, and attracts # ____ and releases them to the inside of the cell
3 Na+, 2 K+
a slight shift away from the RMP in a specific region of the plasma membrane
local or graded potentials
ion channels that open in response to a mechanical stimulus or a chemical stimulus located in dendrites and soma
stimulus-gated channels
When stimulus triggers the opening of stimulus-gated Na+ channels. More Na+ enters the cell allowing the potential to move towards zero.
excitation (depolarization)
When stimulus triggers the opening of stimulus gated K+ channels. More K+ exits the cell allowing the potential to move away from zero.
Inhibition (hyperpolarization)
The membrane potential of a neuron that is conducting an impulse; also known as a nerve impulse
action potential
A _____ is an all or none response.
action potential
Forced recall: Mechanism of the action potential
- Adequate stimulus triggers stimulus-gated Na+ channels to open, causing Na+ to diffuse rapidly into cell and producing a local depolarization
- When threshold potential is reached voltage-gated Na+ channels open. More Na+ enters cell, causing further depolarization
- As Na+ enters the cell membrane potential moves rapidly toward 0 mV. It continues in a positve direction until it peaks (30+mv)
- voltage gated Na+ channels stay open for 1 ms before they automatically close
- Repolarization
- K+ channels often remain open as membrane reaches RMP. Possible hyperpolarization may occur.
voltage-gated K+ channels open when threshold is reached, however, they open slowly and do not allow outward diffusion of K+ until peak is reached
repolarization
brief period during which a local area of the axon’s membrane resists restimulation
refractory period
about 0.5 ms after membrane surpasses threshold potential, it will not respond to any stimulus… no matter how strong
absolute refractory period
few ms after absolute refractory period - the time during which the membrane it repolarizing and restoring the RMP. Membrane will only respond to very strong stimuli.
relative refractory period
Conduction of an action potential: Reversal of _____ from RMP to peak of an action potential causes electrical current to flow between the site of reversal and adjacent regions of membrane
polarity
During a _________ the refractory period prevents restimulation of previous segments.
conduction of an action potential
