Chapter 2- Nerve Cells and Nerve Impulses Flashcards
glia (neuroglia)
smaller and more numerous than neurons. several types; many functions
neurons
cells that receive and transmit information to other cells
membrane (plasma membrane)
composed of two fat molecule layers, allows uncharged chemicals in and out of the cell; charged particles flow through protein channels
nucleus
the structure that contains the chromosomes
mitochondrion
provides the cell with energy; performs metabolic activities; requires fuel and oxygen to function
ribosomes
site of protein synthesis in the cell
endoplasmic reticulum
network of thin tubes that transport newly synthesized proteins to their locations
motor neuron
soma in the spinal cord; receives excitation from other neurons and conducts impulses to muscles and glands from the spinal cord
sensory (receptor) neuron
specialized at one end to be sensitive to certain kinds of stimulation (light, sound, touch)
dendrites/ dendrite spines
arbers; input branching fibers that extend from the cell body, lined with synaptic receptors to receive info from other neurons
short outgrowths that further branch out found on some dendrites
cell body (soma)
contains the nucleus, ribosomes, mitochondria, and other structures
axon
long, thin fiber of a neuron responsible for transmitting nerve impulses toward other neurons, organs, muscles
myelin sheath
insulating material covering on vertebrate axons; composed of fats and proteins
nodes of Ranvier
interruptions along the myelin sheath, short unmyelinated sections
presynaptic terminals (end bulb)
end points that release chemicals that cross the junction between one neuron and the next
afferent axons
brings information into a structure
efferent axons
send information away from a structure
interneurons (intrinsic neurons)
those whose dendrites and axons are completely contained within a single structure
astrocytes
a glia that absorbs chemicals released by axons and later returns those chemicals back tot he axon to help synchronize the activity of neurons; removes waste
microglia
very small glia that removes waste materials as well as viruses, fungi
oligodendrocytes
a glia that builds the myelin sheath around certain neurons in the brain and spinal cord
schwann cells
a glia that builds the myelin sheath around certain neurons in the periphery of the body
radial glia
guides the migration of neurons and the growth of their axons and dendrites during embryonic development
the blood- brain barrier
a mechanism that surrounds the brain and blocks most chemicals from entering
active transport system
protein mediated process that uses energy to pump chemical from the blood into the brain through the blood brain barrier (glucose, hormones, amino acids, vitamins)
glucose
a simple sugar for neuron nutrition
thiamine
vitamin needed to use glucose
electrical gradient
a difference in the electrical charge inside and outside of the cell
polarization
a difference in the electrical charge between two locations (slightly more negative on the inside relative to the outside)
resting potential
the state of the neuron prior to the sending of a nerve impulse
microelectrodes
A typical resting memebrane potential which is -70 millivolts (mV)
selectively permeable
membrane which allows some molecules to pass freely while restricting others
sodium-potassium pump
a protein complex that continually pumps three sodium ions out of the cells while drawing two potassium ions into the cell
concentration gradient
the difference in distributions of ions between the inside and the outside of the membrane
hyperpolarization
increasing polarization (when the negative charge inside the axon increases)
depolarization
decreasing polarization towards zero (when the negative charge inside the axon decreases)
threshold of excitation
the level that a depolarization must reach an action potential to occur
action potential
messages sent by the axon; when the depolarization meets or goes beyond the threshold of excitation
voltage-gated channels
regulating channels of sodium and potassium; permeability depends on the voltage difference across the membrane
local anesthetic drugs
block the occurrence of action potential by blocking voltage-activated sodium gates
all-or-none law
states that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it
refractory period
a period immediately after an action potential during which time the neuron resists the production of another action potential
absolute refractory period
an action potential cannot occur regardless of stimulation (sodium gates are incapable of opening)
relative refractory period
action potential can be initiated exceeding threshold (sodium gates can open, but potassium channels remain open)
axon hillock
where the action potential begins; a swelling located at where the axon exits the cell body
propagation of the action potential
the transmission/movement of an action potential down the axon
saltatory conduction
the “jumping” of the action potential from node to node
local neurons
small neuron with short dendrites, short axons
exchange information with only close neighbors, and do not produce action potentials
graded potential
membrane potentials that vary in magnitude in proportion to the intensity of the stimulus
