Class 1 - Overview/Signal Transmission Flashcards
Give examples of white matter found in the PNS
nerves, which are bundles of myelinated axons or dendrites
What is a nerve?
a bundle of myelinated axons plus its associated connective tissue and blood vessels in the PNS
Where can grey matter be found in the PNS?
ganglia
Compare/contrast nerves vs. tracts
nerves are found in the PNS
tracts are found in the CNS and connect nuclei or areas of the cortex
both are white matter, bundles of myelinated axons
True or false: all of the following are grey matter Neuron cell bodies Unmyelinated axons Dendrites Nuclei Axon terminals Neuroglia
True
The enteric plexus is composed of ___ and ___. What layer of the digestive tract wall is each of these found?
Myenteric (Auerbach) plexus (within the muscularis)
Submucosal (Meissner’s) plexus (within the submucosa)
What are the three types of sensory receptors?
- free nerve endings (bare dendrites)
- encapsulated free endings
- separate cells
What are the effectors of the somatic nervous system?
skeletal muscles
What is the most abundant structural type of neuron?
multipolar
The myelin sheath is formed by who in the PNS and who in the CNS?
PNS - Schwann cells
CNS - oligodendrocytes
Most sensory neurons are of what structure?
unipolar
Motor neurons are of what structure?
multipolar
Most interneurons are of what structure?
multipolar
Describe multipolar neurons
several dendrites
one axon
Describe bipolar neurons
one main dendrite, one axon, with the cell body interrupting the path between them
Where are bipolar neurons found?
retina of the eye, inner ear, olfactory area of the brain
Describe unipolar neurons
dendrites and one axon that are fused together - the cell body stems off from this long process, without interrupting it
they begin in the embryo as bipolar neurons
The dendrites of most unipolar neurons function as…
sensory receptors
What is a Purkinje cell, where is it found?
a neuron with an expansive pattern of dendrite dispersion, found in the cerebellum
What is a pyramidal cell, where is it found?
a neuron found in the cerebral cortex, which as a pyramid-shaped cell body
What cells of the nervous system are capable of cell division?
neuroglial cells
Which neuroglial cells are only found in the CNS?
astrocytes
microglia
oligodendrocytes
ependymal cells
What are the functions of astrocytes?
create the BBB
regulate growth, migration, and interconnection of embryonic neurons
influence formation of neural synapses
maintain chemical environment for generation of nerve impulses
What role do oligodendrocytes play?
make and maintain myelin sheaths in the CNS
Which neuroglial cell is most numerous?
astrocytes
Describe the structure of microglia, astrocytes, oligodendrocytes, and ependymal cells
Microglia - small cells with spine-like projections
Oligodendrocytes - similar to astrocytes but smaller and fewer processes
Astrocytes - star-shaped with many processes
Ependymal cells - have cilia and microvilli
What is the function of microglia?
phagocytosis of debris and bacteria in damaged tissue
What is the function of ependymal cells?
arranged in a single layer to line the ventricles, forming part of the blood-CSF barrier
What is the function of satellite cells?
regulate exchange of material between neuronal cell bodies and ISF
Which part of the neuron membrane is more negatively charged?
the inside surface
A cell with a membrane potential is said to be…
polarized
What is the average resting membrane potential of:
neurons
RBC’s
heart/skeletal muscle
neurons -70mV
RBC’s -10mV
heart/skeletal muscle -90mV
Graded potentials are useful for ___ while action potentials are useful for ____
GP: short distance communication
AP: long distance communication
What is ‘decremental conduction’?
refers to the gradual decrease in the stimuli and resultant response along the pathway of conduction (GP decreases as it spreads)
What is ‘summation’?
stacking of GP’s (adding together to result in a stronger or longer stimulus) –> can be temporal summation (repeated input) or spatial summation (multiple at same time)
Graded potentials mainly occur where?
dendrites + neuron cell bodies
What is the action potential ‘threshold’?
-55mV
What occurs in the depolarization phase of an action potential?
- stimulus causes Na+ channels to open
- Na+ ions rush into the cell
- K+ moves out at a slower rate
- inside of cell becomes much more positively charged, reversing the polarity
What occurs in the repolarization phase of an action potential?
- Na+ channels close, extra K+ channels open
- K+ moves out very quickly, resulting in the membrane potential being even more negative than originally until K+ channels close
- Sodium-potassium pumps re-establish the required Na/K concentrations
Why does an absolute refractory period occur?
Na+ channels cannot reopen before the cell returns to its resting state
What two conditions are required in the relative refractory period to generate a second AP?
- a larger than normal stimulus
2. K+ channels are still open, inactivated Na+ channels have already returned to their resting state
