Chapter 6 part D Flashcards
What are the two parts of the nervous system?
the peripheral nervous system (PNS)
the central nervous system (CNS)
What makes up the central nervous system?
the brain
the spinal cord
What makes up the peripheral nervous system?
all of the nerves in the body not including the brain and the spinal cord.
What is the afferent division of the peripheral nervous system?
the division that carries signals to the CNS.
What is the efferent division of the peripheral nervous system?
the division that carries signals to the target or effector organ.
What kinds of neurons make up the efferent division of the PNS
somatic neurons and autonomic neurons.
What two systems make up the autonomic neurons?
the sympathetic
the parasympathetic
What is the enteric nervous system?
lies within the wall of the gastrointestinal tract.
Describe afferent neurons.
have sensory receptors.
cell bodies are in the dorsal root ganglion (DRG).
Describe efferent neurons.
cell bodies are generally located in the CNS.
efferent axons or nerve fibers leave the CNS and travel to the target organ.
Describe the location of the autonomic efferent fibers.
have 2 neurons between the CNS and target organ, the cell body of the first neuron is in the CNS, and the cell body of the second neuron is a ganglion.
Describe interneurons.
lie entirely within the CNS.
make up 99% of all neurons.
coordinate information between the afferent and efferent fibers and also, in the brain, provide signal processing for higher cognitive function.
What are tracts?
bundles of axons in the CNS
What are nerves?
bundles of axons in the PNS.
What are nuclei?
clusters of cell bodies in the CNS.
What are ganglia?
clusters of cell bodies in the PNS.
What are glial cells?
make up 90% of cells in the CNS.
Make up 50% of the volume of the brain.
do not conduct nerve impulses.
are able to divide.
What are astrocytes?
glial cells in in the CNS that are star-shaped and hold neurons together in proper spatial relationships.
serve as scaffolding for neuronal migration in brain development.
What do astrocytes accomplish by retracting their processes?
allow new synapes to form.
What do astrocytes establish?
the blood brain barrier by working with small blood vessels.
What do astrocytes maintain?
the proper relationship between sodium and potassium in the brain by taking up potassium.
high potassium concentrations in the extracellular fluid are correlated with epileptic seizure episodes.
What are the lesser functions of astrocytes?
repair injuries and form neural scar tissue.
provide metabolic support for the neurons by taking up and degrading glutamate and GABA.
communicate with other astrocytes and neurons via gap junctions and chemical messages.
What are oligodendrocytes?
glial cells that myelinate the axons in the CNS.
What are ependymal cells?
glial cells in the CNS that line the ventricles of the brain and central canal of the spinal cord and play a role in the production of CSF.
have cilia to help with flow of CSF.
can act as stem cells for neurons and glia.
What are microglia?
glial cells in the CNS that are phagocytic and remove invading organisms.
develop from the same lineage as monocytes, but these cells have migrated to the brain and differentiate into microglia
What do microglia release?
reactive oxygen species and may be the cause of cell death in ALS.
What are the glial cells of the PNS?
schwann cells and satellite cells.
What are schwann cells?
glial cells in the PNS that myelinate axons
What are satellite cells?
glial cells in the PNS that support cell bodies of neurons in ganglia.
What are gliomas?
cancer of the brain of glial cells.
How much of the bodies oxygen does the brain use?
20%
How much of the body’s glucose does the brain use?
50%
What is neuroglobin?
a protein like hemoglobin and myoglobin, specialized to bind oxygen.
Does the brain store glucose?
no, during starvation, the brain can use ketones for energy.
How long does it take brain tissue to begin to die after blood supply has been blocked?
4-5 minutes.
What provides nutrients to the brain?
blood and CSF.
What are the three protective structures of the brain?
skull, vertebral column, and meninges.
What are the meninges?
membranes that wrap around the CNS.
Contains dura matter, dural sinuses, and arachnoid mater.
What are the dura mater and dura sinuses?
the outer layer of the meninges that are very tough.
In the sinuses, the blood and CSF recombine.
What is arachnoid mater?
the middle layer of the meninges that is filled with CSF.
What are arachnoid villi?
villi that project into the dural sinuses and provide structure for passage of CSF into the blood.
What is the pia mater?
the highly vascular inner layer of the meninges.
lies next to the nervous tissue.
What is the function of cerebral spinal fluid?
cushions the brain and provides it with nutrients.
Where is the cerebral spinal fluid?
Inside the four ventricles within the interior of the brain and a central canal within the spinal cord.
Describe the flow of CSF
- CSF is produced by the choroid plexus
- CSF circulates in the ventricles
- CSF flows out of the 4th ventricle into the subarachnoid space
- CSF enters the venous system via the dural sinuses, CSF is therefore reabsorbed into the blood at the dural sinuses.
How is CSF formed?
by the choroid plexuses (special clusters of ependymal cells) found within the ventricles of the brain.