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Anat Exam 2--1 of 6
Hamster
60
Anatomy
Undergraduate 4
10/09/2010

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Term
The general functions of the Nervous System
Definition
- Communication/Homeostasis
1.Sensation
2. Integration
3. Reaction
Term
The nervous system can be divided into 2 major parts:
Definition
CNS: Central Nervous System
PNS: Peripheral Nervous System
Term
The major anatomical components of the CNS
Definition
Brain and Spinal Cord
Term
Major anatomical components of the PNS
Definition
Nerves: cranial nerves and ganglia
Ganglia: Sensory and Autonomic (a type of motor)
Term
somatic
Definition
sensation from the outside
"soma"=body
Term
visceral
Definition
sensation from inside, organs (ex: nausea)
"viscus"=organ
Term
visceromotor
Definition
motor to cardiac, sm muscle, and glands (ex: sweat glands)
Term
somatomotor
Definition
sk muscles
Term
Functional unit of Nervous System
Definition
neuron, so each neuron can do the basic functions of the nervous system
Term
3 basic properties of neurons
Definition
1. excitability
2. conductivity
3. secretion
Term
(basic properties of neurons): 1. Excitability (def)
Definition
respond to stimuli (chemical, electrical, mechanical)
Term
(basic properties of neurons): 2. Conductivity
Definition
quickly conduct/transmit electrical signals over long distances
Term
(basic properties of neurons): 3. Secretion
Definition
releases a NT to affect another cell
Term
3 basic classes of neurons--based on function
Definition
1. Sensory/afferent
2. Interneurons
3. Motor/Efferent
Term
Sensory/Afferent neurons
Definition
-Conduct signals from receptors to the CNS
- Cell bodies in PNS, axons in CNS
Term
Interneurons
Definition
only in CNS, cell bodies and axons in CNS
Term
Motor/efferent neurons
Definition
-conduct signals from CNS to effectors (muscles and glands)
- cell bodies in CNS, axons in PNS
Term
Most cell bodies are in _____ (PNS or CNS?)
Definition
CNS
-interneurons
-motor (but some motor cell bodies of motor neurons can be in PNS)
Term
Cell body/Soma contains ________
Definition
nucleus
Term
Neurofibrils
Definition
bundles of axons that support the cell, help the cell maintain the correct shape
Term
Nissl bodies
Definition
massive accumulations of rough ER (which synthesize proteins)
Term
Dendrites
Definition
-receive incoming signals
-where other cell's axon usually makes contact
- carries info to the cell body
Term
Axon (one per neuron)
Definition
-carries info away from cell body
- a single process that transmits an AP
- sends signal to a target
Term
Initial segment
Definition
-highly sensitive to electrical changes of membrane
-first part to depol
Term
Axon collaterals (def and purpose)
Definition
def: branch of axon
purpose: so there can be multiple targets for a single neuron
Term
Axon terminals
Definition
where axons terminate on their target (target can be neurons/muscles/gland/etc)
Term
resting potential
Definition
baseline charge of the neuronal membrane
Term
depolarization
Definition
decrease in polarity across the membrane
Term
repolarization
Definition
-sodium channels close after a fixed amount of time
- Re-establish polarity of membrane at rest
Term
Distinguish between ganglia and nuclei
Definition
ganglion: clusters of cell bodies with a common function in the PNS
nuclei: cell bodies with common func in CNS
Term
Distinguish between tract and a nerve
Definition
tract: clusters of axons with a common func in the CNS
nerve: axons with a common func in the PNS
Term
3 diff types of neurons based on shapes: determined by how many dendrites
Definition
1. Multipolar
2. Bipolar
3. Unipolar
Term
Multipolar
Definition
-many dendrites, single axon
- most common type
- many diff functions
Term
Bipolar
Definition
- one dendrite, one axon
*rare- only in the special senses (sight, hearing, etc, so some locations would be in retina, cochlea, etc)
Term
Unipolar
Definition
-there are lots of these
- one process is both the dendrite and axon
- general sensory cells in dorsal root and cranial nerve ganglia
- in these, the cell body only really used to keep neuron alive
- aren't out in skin b/c they would be too vulnerable to damage out there
Term
nerves out numbered __:__ by glial cells
Definition
50:1
Term
Four glial cell types found in the CNS
Definition
1. Astrocyte
2. Ependymal cell
3. Oligodendrocyte
4. Microglial cell
Term
Astrocyte (functions-there are 3)
Definition
- "astro"=star
1. take up ions from ECF (via endocytosis)
2. surround blood vessels and form tunnels
3. form scar tissue when neurons are injured
Term
Ependymal cell
Definition
- line the ventricles (which are fluid filled spaces in the brain)
- produce CSF (cerebro-spinal fluid)
Term
Oligodendrocyte
Definition
- produce myelin in CNS
- myelinate axons in CNS
Term
Microglial cell
Definition
- equivalent to macrophages
- eat debris, clear it out so the astrocytes can come in and lay down scar tissue
Term
Two types of glial cells found in the PNS
Definition
1. Satellite cells
2. Schwann cells
Term
Satellite cells
Definition
- encircle the cell bodies in the PNS and separate them from surrounding tissue
- found in ganglia
*nothing like this in the CNS b/c in the CNS is all nervous tissue
Term
Schwann cells
Definition
- myelinate axons in the PNS
- produce basement membrane
- associated with all axons in the PNS--surround all, but don't necessarily myelinate all
Term
What determines whether or not an axon gets myelinated?
Definition
Its diameter
Term
myelin
Definition
A lipid sheath around a nerve fiber, formed from closely spaced spiral layers of the plasma membrane of a Schwann cell or an Oligodendrocyte
Term
How does myelination differ in the CNS and PNS?
Definition
- Each Oligodendrocyte helps myelinate multiple axons in the CNS
- multiple Schwann cells myelinate a single axon in the PNS
Term
Node of Ranvier
Definition
- gap between adjacent Schwann cells
- no myelin here
- only site in a myelinated axon capable of depol.
Term
How does myelin speed up conduction process?
Definition
- a myelinated axon is functionally much shorter
- speeds up AP propagation
- unmyelinated: lots and lots of little segments of membrane, have to depol them all
- myelinated: can skip/jump from Node of Ranvier to Node of Ranvier
Term
Diseases that cause demyelination
Definition
-ex: MS
-myelin gets thinner and shorter
- exposes parts of axons membrane that were covered with myelin: parts that aren't able to depol
- not only slower AP, but AP can't go at all!
Term
How are unmyelinated fibers protected from their surroundings?
Definition
- have sunk under the surface of the Schwann cell
- a single Schwann cell surrounds many axons
Term
How do unmyelinated axons conduct AP's?
Definition
-have ion channels and depol along entire length of the membrane
*slower
Term
Neurons communicate with each other and with muscles and glands though _______.
Definition
Synapses
Term
Post-synapic neuron
Definition
-usually on dendrites of target cell, but can be any part of the target cell
Term
Axodendritic
Definition
- axon terminates on dendrites of target cell
Term
Axosomatic
Definition
- axon terminates on nerve cell body of target cell
Term
Axoaxonic
Definition
- axon terminates on another axon
* usually inhibatory
Term
Typical chem synapse
Definition
- AP reaches the Axon terminal
- calcium enters the axon terminal, which stimulates exocytosis of NT's
Term
To excite, send ____. To inhibit, send ____
Definition
excite: sodium ions to depol
inhibit: chloride to hyperpolarize
Term
Two types of circuits: convergent and divergent. Explain and give an advantage.
Definition
1. Convergent: many neurons converge on a single neuron. Heightens sensitivity but decreases ability to localize
2. Divergent: one neuron branches/diverges. AMPLIFIES signal being snet through system, good if you're in a crisis
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