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Nervous System
Lecture material- Brain and Spinal Cord
78
Anatomy
Graduate
12/02/2012

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Term
Neuroglia
(definition and types)
Definition
Supporting cells of the NS- 6 types
CNS- Astrocytes, Microglia, ependymal, oligodendrocytes
PNS- satellite cells, Schwann cells
Term
What makes up the Central Nervous System?
Definition
Brain and Spinal cord
Term
2 Components of the Sensory Division of the NS
Definition
Somatic Afferents- info sent to brain from receptors that tell you what you "feel"
Visceral Afferents- info sent to reflex centers- subconscious for visceral organs
Term
2 Divisions of Motor Division
Definition
Somatic NS (somatic efferents)- signals to control voluntary skeletal muscles
Autonomic NS (visceral efferents)- composed of the sympathetic NS and Parasympathetic NS:signals sent from autonomic centers in the brain to visceral organs for control (smooth and cardiac muscle, glands, adipose tissue)
Term
Astrocyte
Definition
largest and most abundant type
wraps around neurons and blood vessels
contribute to Blood brain barrier
guide neuron development
Term
Microglia
Definition
monitor neuron health and can become phagocytic
Term
Ependymal
Definition
have cilia and help circulate CSF
Term
Oligodendrocytes
Definition
wraps around axon to form myelin sheath
Term
Satellite cell
Definition
surround and insulate cell bodies within a ganglia
Term
Schwann Cells
Definition
wrap around axon to form myelin sheath (one cell wraps around one internode of a neuron and creates neurilemma)
Term
What cellular organelle do neurons lack
Definition
centrioles - amitotic so they are not needed because the cells don't replicate
Term
Nissl bodies
Definition
RER of a neuron
Term
Neurofibrils
Definition
neurofilaments that form the cytoskeleton
Term
Terminal branches / telodendria
Definition
end opposite the cell body where NT are released
Term
Neurotubules
Definition
motor proteins involved in fast axonal transport
Term
Neurotubules
Definition
motor proteins involved in fast axonal transport
Term
Anterograde
Definition
soma to axon terminals
Term
Retrograde
Definition
axon terminals to soma
Term
Axolemma
Definition
axon cell membrane
Term
Node of Ranvier
Definition
segement on an axon between myelin sheath
Term
Interneurons (association neurons)
Definition
Most in CNS in autonomic ganglia
Mostly comprised of multipolar neurons
Involved in higher level processing and planning.
Simples type involved one interneuron between a sensory and motor neuron
Term
Potential Energy
Definition
in the form of separation of charges across a membrane
Term
Voltage
Definition
the unit used to measure potential energy (in volts of milivolts)
Term
Electricity
Definition
kinetic energy in the form of current when separate charges are allowed to move through channels
Term
Current
Definition
flow of charges between two points
Ohms law - I=V/R

Depends on Voltage and resistance to flow
Term
Leak Channels
Definition
always open (non-gated)
used to generate Resting membrane potential
Term
Ligand-gated channels
Definition
chemical binding causes the channel to change (conformational change)
Used to generate graded potentials
Term
Voltage-gated channels
Definition
change in voltage triggers channel to open or close
Used to generate AP
Term
Mechanically gated channels (mechanoreceptors)
Definition
respond to deformation in the membrane
Used by some sensory receptors to generate a graded potential (meissner's corpuscles)
Term
What factors create and maintain the Resting Membrane Potential
Definition
1. Leak channels (K>>>>Na)
2. Na-K pump maintains the concentration of Na and K across the membrane
Term
Equilibrium potential for Na and K
Definition
*the membrane potential resulting in an electrical gradient that is equal and opposite to the concentration gradient- no net ion movement
Na +65mV
K -94mV
Term
why is the RMP closer to the resting membrane potential for K?
Definition
because the membrane in more permiable to K. -94 vs -70
Term
What is a graded potential called at the cell body or dendrites
Definition
post-synaptic potential
Term
Why does a graded potential decay over distances?
Definition
resistance of the cytosol and ions leaking back across the membrane
Term
How strong does the graded potential need to be when it reaches the axon hillock to generate an AP?
Definition
15mV- if the resting membrane potential is -70 and the threshold for a cell is -55 you would need 15mV to raise the -70 to threshold for an AP
Term
Activation and Inactivation Gates
Definition
Activation gates for Na open at threshold (both are "triggered" but only one opens first) and then 1ms later the inactivation gate closes. To reactivate the channel, the activation gate must be closed and the inactivation gate must be open.
Term
Repolarization (30 to -70 mV)
Definition
voltage gated K channels are also triggered at threshold but have a 1ms delay (they open when Na inactivation gates close)
Term
Absolute refractory period
Definition
Opening of V-gates NA channels to closure of inactivation gate until enough of the channels have reset
*cannot generate an AP at this time
Term
Relative refractory period
Definition
Some v-gates Na channels are still resetting. Voltage gated K channels still open
*Can generate an AP at this time but need suprathreshold stimulus
Term
Contiguous Conduction
Definition
along an unmyelinated axon
Requires a lot of voltage gated Na channels along the entire length of the axon. More energy used to pump Na back out of the cell. Speed= 2 mph
Term
Saltatory Conduction
Definition
along myelinated axon
Voltage gated Na channels only along Nodes of Ranvier
Less Na moved into the cell so less energy used to pump the ions back out
speed= 40-300 mph
Disease- demelinating disease
Term
Type A neuron
Definition
large diameter and myelinated
150 meters per second
somatic sensory- vision, proprioception, balance, touch and pressure
somatic motor
Term
Type B neurons
Definition
medium diameter and myelinated
speed- 15 meters per second
visceral and somatic sensory- temperature, pain, touch and pressure
Autonomic motor- smooth and cardiac muscle and glands
Term
Type C neuron
Definition
small Diameter and unmyelinated
1 meter per second
same information carried as type B neurons
Term
Types of synapses
Definition
Axosomatic, axodendritic, axoaxonic, electrical synapse, chemical synapse
Term
Electrical synapse
Definition
rare- direct transfer of AP across gap junctions
Term
Chemical Synapse
Definition
same as the Ach synapse at the NMJ (cholinergic synapse)
Term
Spatial Summation
Definition
same time at different location
additive and increase the strength of the depolarization current spreading toward the axon hillock
Term
Temporal Summation
Definition
same location at different times
Term
Mechanism of NT action- Direct Action
Definition
protein that binds receptor is also the channel (nicotinic) faster but only 1:1 reaction- smaller
Term
Mechanism of Action- Indirect Action
Definition
binding of protein to receptor does not directly cause an action (may activate a pathway that creates a second messanger- second messenger pathway)
slower but much larger effect because one NT can generate MANY second messangers
Term
Nicotinic Ach receptors
Definition
direct action, excitatory NT
Found at telodendria of somatic and middle neurons of the PNS and SNS
Term
Muscarinic Ach receptor
Definition
indirect action and can be excitatory or inhibitory
Found at PNS effectors- parasympathetic (for heart cells)
Term
Biogenic Amine receptors
Definition
indirect action
widely used in CNS and SNS (sympathetic NS)
catecholaminues, serotonin and histamines (adrenergic synapse)- Norepinephrine
Term
Amino Acids NT's
Definition
Glutamate- excitatory NT in the brain (direct)
GABA- inhibitory NT in the CNS (direct)0
Term
Neuropeptide NT's
Definition
endorphins and enkephalins
Term
Other categories of NT
Definition
purines, gases, lipids
Term
Serial processing
Definition
chain of neurons leading to a specific, predictable response (spinal reflex, somatic sensory input from receptor in somatosensory cortex of the bain)
Term
Parallel processing
Definition
inputs are divided into multiple pathways, with different destinations and more complex responses
Term
Diverging circuits
Definition
"amplifying circuits"
one input from the upper motor neuron --> many outputs
Term
Converging circuit
Definition
"concentrating" circuit
many inputs (different sensory stimuli)--> one output (single memory)
Term
Reverberating circuit
Definition
"oscillating" circuit
branches in the pathway provide feedback to previous neurons in the chain
Involved in repetitive motor activities (breathing, locomotion, sleep wake cycle)
Term
Hemicholimium
Definition
Blocks Ach synthesis
Term
Botulinis toxin
Definition
Blocks Ach release directly
Term
Barbiturates
Definition
Decreased rate of Ach release
Term
Lidocaine
Definition
reduces membrane permiability to Na by blocking the voltage gated Na channels
Term
Tetrodotoxin (TTX)
Saxitoxin(STX)
Ciguatoxin (CTX)
Definition
blocks sodium ion channels by blocking the fast voltage gated Na Channels
Term
Neostigmine
Definition
Prevents Ach inactiviation by cholinestrase
used to treat myasthenia gravis
Term
Donepezil
Definition
Anti-cholinesterate inhibitor
used to treat alzheimer's disease along with rivastigmine and galantamine
Term
Insecticides
Definition
prevents Ach inactiviation by cholinestrase
Term
d-tubocurarine (curare- plant based)
Definition
prevents Ach binding to postsynaptic receptor
Term
Nicotine
Definition
Binds to Ach receptor site (high doses cause paralysis)
Term
Succinylcholine
Definition
Reduces sensitivity to Ach
(used for muscle relaxation during surgery)
Term
Atropine
Definition
competes with Ach for binding sites on the postsynaptic membrane
producted by nightshade plant (reduces heart rate, smooth muscle activity, salivation, dilates pupils, skeletal muscle weakness
Term
4 phases where compounds interfere with synaptic activity
Definition
1. NT synthesis (hemicholinium)
2. rate of NT release (botox and barbitarates)
3. preventing NT inactivation (Neostigme)
4. preventing NT binding to receptors (chorare)
Term
Black Widow Venom
Definition
stimulates massive release and exocytosis of Ach (sustained contraction)
Term
Myasthenia Gravis
Definition
Antibodies destroy and reduce the number of Ach receptors on the MEP (auto-immune disease. Use black widow venom as treatment
Term
Tubocurarine
Definition
neuromuscular Ach-R antagonist- antagonist binds to and hogs Ach receptor. Cannot contract. (**An agonist would bind to the receptor and excite the cell just like Ach would)
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