short, highly branched signal receptive regions of the nerve cell. Convey incoming
dendrites
message toward cell bodies
each nerve cell (neuron) has only one axon
axon impulse generating and conducting region of neuron
Whitish fatty protein layer that protects and electrically insulates the axon. Increases
myelin sheath
the speed of transmission of nerve impulses
myelin sheath is only associated with axons, not dendrites
what determines resting membrane balance of K+ and Na+
potential
k+ leak permeability out of the cell
Na+ leak permeability into the cell
3 types of ion channels chemically gated, voltage gated, mechanically gated
chemically gated ion channels channel-linked receptors that open to let a specific ion pass in response to a ligand
voltage-gated ion channels Channels that open or close in response to a change in the membrane potential.
membrane ion channels that are opened or closed by deformation or stretch of the
mechanically gated ion channels
plasma membrane
action potentials are also known as nerve impulses
self-regenerating wave of electrochemical activity that allows neurons to carry a
action potential
signal over a distance. All or non phenomenon
resting membrane potential -70mV
"Depolarization to Threshold"
step one of action potential
A graded depolarization brings an area of excitable mebrane to threshold (-60mV)
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, 10/14/24, 5:53 PM
"Activation of Sodium Channels and Rapid Depolarization"
1. The voltage-regulated sodium channels open (sodium channel activation)
step two of action potential 2. Sodium ions, driven by electrical attraction and the chemical gradient, flood into
the cell.
3. The transmembrane potential goes from -60 mV, the threshold level, toward +30
mV.
"Inactivation of Sodium Channels and Activation of Potassium Channels"
1. the voltage-regulated sodium channels close (sodium channel inactivation occurs)
Step Three of Action Potential at +30 mV.
2. The voltage-regulated potassium channels are now open, and the potassium ions
diffuse out of the cell.
3. Repolarization begins.
"Return to Normal Permeability"
1. The voltage regulated sodium channels regain their normal properties in 0.4-1.0
msec. The membrane is now capable of generating another action potential if a
larger than normal stimulus is provided.
step four of action potential
2. The voltage regulated potassium channels begin closing at -70 mV. Because they
do not all close at the same time, potassium loss continues and a temporary
hyperpolarization to approximately -90 mV occurs.
3. At the end of the relative refractory period, all voltage-regulated channels have
closed and the membrane is back to its resting state.
the period immediately following the firing of a nerve fiber when it cannot be
absolute refractory period
stimulated no matter how great a stimulus is applied
A period after firing when a neuron is returning to its normal polarized state and will
relative refractory period
fire again only if the incoming message is much stronger than usual
how is Na+/K+ balance reestablished after sodium potassium pump
action potential
Rapid transmission of a nerve impulse along an axon, resulting from the action
saltatory conduction potential jumping from one node of Ranvier to another, skipping the myelin-
sheathed regions of membrane.
fluid compartments in body digestive tract, bloodstream, and intracellular fluid
Most body fluids are found in intracellular fluid
4 tissues of the human body epithelial, connective, muscular, nervous
tissues are collections of cells that preform limited functions
functions of epithelial tissue lines, protects, and secretes
characteristics of epithelial tissue cellularity, polarity, attachment, avascularity, regeneration
Cellularity cell junctions, cells fit closely together
polarity apical and basal surfaces
attatchment the lower surface is bound by a structure called the basement membrane
avascularity lack of blood vessels
how does this tissue get its nutrients diffusion and absorption
regenerates easily if well nourished
2/5
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