Ch 4: The Nervous System Flashcards
Neurons
Specialized cells capable of transmitting electrical impulses and then translating those electrical impulses into chemical signals.
Each has unique shape that matches its function.
NOT physically connected to each other
Where is the nucleus of a neuron located?
Cell body/Soma
Dendrites
Finger like projections off of a neuron’s soma, responsible for receiving incoming messages from other cells.
Axon Hillock
Located at base of neuron cell body which integrates incoming signals (through summation) and initiates an action potential ONLY IF the net depolarization reach the threshold value (-55 to -40mV)
Axon
Long appendage that extends from the cell body to somewhere in close proximity of the target structures.
Myelin Sheath
fatty membrane that insulates nerve fibers so signals are not crossed or lost.
Increases speed of the conduction of the axon.
Broken up by Nodes of Ranvier
What produces myelin?
Oligodendrocytes in the CNS and Schwann cells in the PNS
Nerve terminal/Synaptic bouton
Enlarged and flattened structure at the end of an axon that allows signal to be transmitted to the next neuron and neurotransmitters to be released
Synaptic Cleft
small space between terminal portion of the axon and dendrites of the adjacent neuron
Synapse
nerve terminal + synaptic cleft + postsynaptic membrane.
Where neurotransmitters are released, transverse, and then bind
Nerve
a bundle of multiple neurons within the PNS. Can be sensory, motor, or mixed, depending on the types of information they carry. clustered into ganglia.
Tracts
a bundle of multiple neurons in the CNS. Only carry one type of information and neurons are grouped into nuclei.
Glial Cells/Neuroglia
cells that provide structure and support to neurons, including…
- Astrocytes
- Ependymal Cells
- Microglia
- Oligodendrocytes/Schwann cells
Astrocytes
nourish neurons and form blood-brain barrier, controls transmission of solutes from bloodstream into nervous tissue
Ependymal Cells
line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber
Microglia
Phagocytic cells that ingest and break down waste products and pathogens in the CNS
Oligodendrocytes/Schwann Cells
produce myelin around the axons in the CNS and PNS
Action Potentials
all-or-nothing messages that relay electrical impulses down the axon, ultimately causing the release of neurotransmitters
resting membrane potential
net electric potential difference that exists across the cell membrane, created by movement of charged molecules (most importantly K+ and Na+) across that membrane.
For neurons, about -70mV, inside negative relative to outside d/t continuous slow leak of K+ out of the cell
Most important ions involved in generating and maintaining the resting potential
K+ and Na+
potassium concentration/gradient in cells
140mM inside the cell, 40mM outside the cell
Favorable to move OUTSIDE the cell
OPPOSITE of Sodium
potassium leak channels
Transmembrane channels that allow for the slow leak of potassium out of the cell.
Equilibrium potential of potassium
around -90mV. Equilibrium that occurs when K+ has been slowly leaked out of the cell, creating a positive environment outside and a negative environment inside the cell, until there is no net movement of the ion.
sodium concentration/gradient in cells
12mM inside the cell, 145mM outside the cell
Favorable to move INSIDE the cell
OPPOSITE of potassium
sodium leak channels
Transmembrane channels that facilitate a slow leak of sodium into the cell with equilibrium ~60mV
