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The Nervous System
Based on the nervous system from lecture class
50
Anatomy
Undergraduate 2
12/11/2011

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Cards

Term
Excitable Cells
Definition
Neurons, muscle cells, sensory receptor cells, gland cells
Term
Nerve Impulse
Definition
An axon is stimulated, and electrical impulse is generated and conducted along the length of its axon.
Term
Axon Potential
Definition
The electrical part of a nerve impulse
Term
VOltage
Definition
the measure of potential energy, generated by seperated charge
Term
How is potential energy measured
Definition
volts or millivolts
Term
The greater the potential difference between two points, the ______ the voltage
Definition
higher
Term
Current
Definition
the flow of electrical charge from one point to another
Term
The amount of charge that moves between two points depends on _____ and ______
Definition
resistance and voltage
Term
Resistance
Definition
is the hindrance to charge flow provided by substances through which the current must pass
Term
Insulators
Definition
substance with high electrical resistance
Term
Conductors
Definition
substance with low electrical resistance
Term
Omh's law
Definition
gives the relationship between voltage, current and resistance
Term
Omh's law
Definition
I = V/R ; considering that conductance (g) is the inverse of resistance (1/R), I = V g
The greater the voltage, the greater the current; the greater the conductance, the greater the current; and, if there is no voltage (V = 0), then there is no current.
Term
Examle of an excellent insulator
Definition
lipid bilayer of the plasma membrane
Term
ion channels
Definition
special membrane proteins
large proteins with several subunits
Term
Three main types of gated channels
Definition
Chemically gated, voltage gated, mechanically gated
Term
Chemically gated channels
Definition
opens when approriate chemical substance binds to a certain part of the ion channel (neurotransmitters)
Term
Voltage gated channels
Definition
Open and close in response to changes in the membrane potential
Term
Mechanically gated channels
Definition
open in response to mechanical deformation of the plasma membrane
Term
Ions move along chemical concentration gradient when they
Definition
diffuse passively from an area of higher concentration to lower concentration
Term
Ion moves along electrical gradient when they
Definition
move towards an area of opposite electricity
Term
The Na+ concentration is higher on the ________ of the cell
Definition
outside
Term
The K+ concentration is higher on the_____ of the cell
Definition
inside
Term
Depolarization
Definition
A reduction in membrane potential; the inside of the membrane becomes less negative
Term
Hyperpolarization
Definition
An increase in membrane potential; becomes more negative than the resting potential.
Term
Depolarization _____ the probability of producing action potentials
Definition
increases
Term
Two types of signals produced with change in membrane potential
Definition
Graded and action potential
Term
Graded Potential
Definition
magnitude varies directly with stimulus strenght. The stronger the stimulus, the more voltage change and the farther the voltage change goes
Term
Types of Graded Potential
Definition
end-plate potential, postsynaptic potential, receptor or generator potential
Term
End Plate potential
Definition
is a type of graded potential which is at the end plate zone of a skeletal muscle fiber
Term
Postsynaptic Potential
Definition
when the stimulus is the neurotransmitter released by another neuron at the zone of physiological interaction b/w 2 neurons
Term
Receptor or generator potential
Definition
at the receptor end of a sensory receptor cell
Term
Action Potential
Definition
the principle way neurons send signals over long distance is by generating and propogating action potentials
Term
Axon Hillock
Definition
the transition from graded potential to action potential takes place here in motor spinal neuron
Term
In sensory neurons, the action potential is generated by
Definition
receptor potential at the end of the peripheral axonal process
Term
Each Na+ channels has _____ gates
Definition
2: voltage-sensitive activation gate and an inactivation gate
Term
During Resting state of action potential
Definition
only leakage channels are open, maintaining the resting membrane potential
Term
Depolarization Phase
Definition
a sudden increase in Na permeability and reversal of the membrane potential
Term
Repolarization Phase
Definition
decrease in sodium permeability
Term
Absolute Refactory Period
Definition
period that extends from the opening of the Na channels until they begin to reset to their original resting state
Term
Relative Refactory Period
Definition
Interval in which most Na channels have returned to their resting state and some K channels are still open
Term
Absolute Refactory Period
Definition
period that extends from the opening of the Na channels until they begin to reset to their original resting state
Term
Relative Refactory Period
Definition
Interval in which most Na channels have returned to their resting state and some K channels are still open
Term
The rate of impulse propogation depends on
Definition
axon diameter and degree of myelination
Term
Continuous Propogation
Definition
axons are unmyelinated and action potentials are generated at adjacent to each other and propogation speed is slow
Term
Saltatory Conduction
Definition
Action potentials are triggered only at nodes of ranvier
Term
Nerver fibers can be classified based on
Definition
degree of myelination, and conduction speed into groups A, B, C
Term
Group A (nerve fiber)
Definition
has largest diameters and thick myelin sheaths, with propgation speed up to 120 m/s. Mostly sensory somatic and motor axons serving the skin, skeletal muscles and joints
Term
Group B (nerve fiber)
Definition
lightly myelinated axons of intermediate diameter, speed of around 15 m/s
Term
Group C
Definition
unmyelinated with smallest diameter, speed of 1 m/s or less.

Axons of ANS and those conveying info about pain & temperature related to A&B
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