Chapter 12 Flashcards
What are the subdivisions of CNS and PNS? What are the different types of neurons and what
are their functions?
*CNS- Brain and spinal cord
*PNS- Nerves and ganglion
(IN ORDER THEY OCCUR)
PNS- Sensory neurons (afferent= toward) conduct signals from receptors to the CNS
CNS- Inter neurons are confined to the CNS
PNS- Motor neurons (efferent= away) conduct signals from the CNS to effectors such as muscles and glands
What are the main parts of a neuron (soma- know its contents, dendrites, axons) and their
functions? What are nissl bodies and lipofuscin granules (role in determining age of a neuron)?
Soma- the control center of the neuron, has no centrioles, contents include a Nucleus, Cytoplasm, RER, neurofibrils, and Nissl bodies
Dendrite- Extension of a neuron that receives information from other cells or from environmental stimuli and conducts signals to the soma.
Axon- efferent nerve fiber
Lipofuscin accumulates with age and pushes the nucleus to one side of the cell. Lipofuscin granules are also called “wear and tear granules” because they are most abundant in old neurons.
What is axon hillock, axoplasm, axolemma, synaptic knob, synapse, synaptic vesicles?
axon hillock- a mound on one side of the axolemma
axoplasm- cytoplasm of an axon
axolemma- membrane of an axon
synapse- A junction at the end of an axon where it stimulates another cell
synaptic vesicles- A spheroidal organelle in an axon terminal containing neurotransmitter.
What is antigrade and retrograde transport and which proteins (kinesin and dynein) assist in this
process?
– Anterograde transport: (kinesin assist) movement down the
axon away from soma
– Retrograde transport: (dynein assist) movement up the axon
toward the soma
What do we mean by an-axonic, unipolar, bipolar or multipolar neurons?
an-axonic- have multiple dendrites but no axon
unipolar- have only a single process leading away from the soma
bipolar- have one axon and one dendrite
multipolar- one axon multiple dendrites
What are the different types of glial cells in the CNS and PNS and what are their functions?
What is astrocytosis or sclerosis?
CNS
Oligodendrocytes- form myelin in brain and spinal cord
Ependymal cells- line cavities of brain and spinal cord
Microglia- destroy microorganisms, foreign matter, and dead nervous tissue
Astrocytes- most abundant glial cells in CNS, cover entire brain surface
PNS
Schwann cells: envelope nerve fibers, produce a myelin
sheath in the peripheral nervous system, and assist in the
regeneration of damaged fibers
* Satellite cells: surround the neuromas in the ganglia of the
PNS, provides electrical insulation around the soma, and
regulate the chemical environment of the neurons
astrocytosis or sclerosis- When neuron is damaged,
astrocytes form hardened scar tissue
What are the causes of brain tumors and what are the treatment options?
Brain tumors arise from…
-Meninges (protective membranes of CNS)
– Metastasis from nonneuronal tumors in other organs
– Often glial cells that are mitotically active throughout life
Treatment options- radiation or surgery
What is myelination, myelin sheath, and nodes of Ranvier, and internodes? What
causes multiple sclerosis and Tay-Sachs disease.
Myelination—production of the myelin sheath
– Begins at week 14 of fetal development
– Proceeds rapidly during infancy
– Completed in late adolescence
– Dietary fat is important for CNS development
Myelin sheath—an insulating layer around a nerve
fiber
– Formed by oligodendrocytes in CNS and Schwann
cells in PNS
– Consists of the plasma membrane of glial cells
* 20% protein and 80% lipid
– Nodes of Ranvier: gap between segments
– Internodes: myelin-covered segments from one
gap to the next
Multiple sclerosis- Degenerative disorders of the myelin sheath, Cause may be autoimmune triggered by virus infection
Tay–Sachs disease: a hereditary disorder of infants of Eastern European Jewish ancestry
What are the different steps in the process of nerve fiber regeneration? What forms the
regeneration tube?
See slide diagram
1. Normal nerve fiber
2. injured nerve fiber
3. degeneration of severed fiber
4. early regeneration
5. late regeneration
6. regenerated fiber
The regeneration tube is formed by Schwann cells, the basal lamina, and the neurilemma
What factors affect the resting membrane potential? What causes depolarization, repolarization,
and hyperpolarization? What are the differences between LP and AP?
Potassium K (ICF) and Sodium NA (ECF). The greatest factors that affect resting membrane potential are potassium ions (K+) because the plasma membrane is more permeable to K+ than any other ion
Causes of
Depolarization-, Sodium Na+, enters
repolarization-, potassium leaves the cell
repolarization- sodium and potassium channels closing
Actional potential is more of a dramatic changed produced by voltage-gated ions compared to local potential
actional potential follows an all-or-none law
What is refractory period? How is absolute refractory period different than the relative refractory
period? Process of conduction of an action potential through a myelinated nerve fiber
Refractory period— period of
resistance to re-stimulation
* Refractory period refers only to a
small patch of the neuron’s
membrane at one time
Absolute refractory period- no stimulus will trigger AP,
Relative refractory- (after absolute) only very strong stimulus will trigger new AP
See diagram
1. Na+ inflow at node generates action potential (slow)
2. Na+ diffuses along inside of axolemma to next node (fast)
3. excitation of voltage regulated gates will generate next action potential here
How messages are transmitted across the
synapse? What is the mechanism of transmission at the excitatory cholinergic, inhibitory GABA-
ergic and an excitatory adrenergic synapse?
