Chapter 2: Nerve Cells & Nerve Impulses Flashcards
Neurons
receive information and transmit it to other cells
Santiago Ramon y Cajal
used newly developed staining techniques to show that a small gap separates the tips of one’s neuron’s fibers from the surface of the next neuron
Charles Sherrington
widely recognized as one of the two founders of neuroscience
Membrane
a structure that separates the inside of the cell from the outside environment
* plasma membrane
Neucleus
the structure that contains the chromosomes
Mitochondrion
the structure that performs metabolic activities, providing the energy that the cell requires for all other activities
Ribosomes
the sites at which the cell synthesizes new protein molecules
Endoplasmic reticulum
a network of thin tubes that transport newly synthesized proteins to other locations
Motor neuron
receives excitation from other neurons through it’s dendrites and conducts impulses along it’s axon to a muscle
*has it’s soma in the spinal cord
Sensory neuron
specialized at one end to be highly sensitive to a sensitive to a particular type of stimulation, such as light, sound or touch
Dendrites
branching fibers that receive information from other neurons
Dendritic spines
the short outgrowth that increase the surface area available for synapses
Cell body (soma)
contains the nucleus, ribosomes, and mitochondria * most of the metabolic work of the neuron occurs here
Axon
a thin fiber of constant diameter, in most cases longer than the dendrites
Myelin sheath
an insulating material
rodes of Ranvier
interruptions in the myelin sheath of vertebrate axons
Presynaptic terminal
the point from which the axon releases chemicals that cross through the junction between one neuron and the next * also known as end bulb & button
Afferent axon
brings information into a structure (exits)
Efferent axon
carries information away from the structure (admit)
Interneurons/Intristic neuron
a neuron whose axons and dendrites are all confined within a given structure
Glia
type of cell in the nervous system that, in contrast to neurons, does not conduct impulses over long distances
Astrocytes
a star-shaped glia that synchronizes the activity of the axons
Microglia
cells that remove waste material and other microorganisms from the nervous system
Oligodendrocytes
glia cells that build myelin sheaths
Schwann Cells
glia cells that build myelin sheaths
Radial glia
cells that guide the migration of neurons and the growth of axons and dendrites during embryological development
Blood-brain barrier
mechanism that excludes most chemicals from the brain
Active transport
a protein-mediated process that expends energy to pump chemicals from the blood into the brain
Glucose
sugar; vertebrate neurons depend almost entirely on glucose
thiamine
B1 vitamin necessary to use glucose
electrical gradient (polarization)
a difference in electrical charge between the inside and outside of the cell
resting potential
the difference in voltage in a resting neuron
selective permeable
some chemicals pass through it more freely than others do
sodium-potassium pump
mechanism that actively transports sodium ions out of the cell while drawing in two potassium ions
concentration gradient
the difference in distribution of ions across the membrane
Action potentials
messages sent by axons
hyperpolarization
increased polarization across a membrane
depolarization
to reduce polarization toward zero across a membrane
threshold of excitation
minimum amount of membrane depolarization necessary to trigger an action potential
Voltage-aged channels
membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane
all-or-none law
principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it
refractory period
time when the cell resists the production of further action potentials
Absolute refractory period
a time when the membrane is unable to produce an action potential
relative refractory period
time after the absolute refractory period that requires a stronger stimulus to mitiate an action potential
Propagation of the action potential
transmission of an action potential down an axon
Axon hillcock
a swelling where the axon exits the cell body
Myelin
an insulating material composed of fats and proteins
Myelinated axons
axons covered with myelin sheaths
Saltatory conduction
the jumping of action potentials from node to node
Local neurons
neurons w/o an axon
graded potential
a membrane potential that varies in magnitude in proportion to the intenisty of the stimulus
