Term
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Definition
Golgi type I
Golgi type II |
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Term
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Definition
long axons (inches-feet); larger diameter
Sensory/motor tracts |
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Term
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Definition
short, smaller diameter axons
Interneurons-connect adjacent cells |
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Term
| Nerve cell types - function |
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Definition
Sensory (afferent)
Motor (efferent)
Interneurons - connect adjacent cells
Cerebral neurons |
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Term
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Definition
point of connection/communication
NO physical contact between neurons |
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Term
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Definition
Presynaptic neuron
Synaptic cleft
Post-synaptic neuron |
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Term
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Definition
Axodendritic (connect axon to dendrite)
Axosomatic (axon to soma)
Axoaxonic (axon to axon) |
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Term
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Definition
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Term
Synaptic Transmission - Big Picture
Pre-synaptic neuron |
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Definition
Message sent down axon to terminal
Neurotransmitter released from vesicles in axon terminal
Neurotransmitters spill into synaptic gap |
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Term
Synaptic Transmission - Big Picture
Post-synaptic neuron |
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Definition
Neurotransmitter binds to receptors on dendrite
Responds to presence of neurotransmitter
Sends message to next neuron |
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Term
Nerve Impulse
Electrical signals |
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Definition
Action potentials, nerve impulses
Within a neuron
Ion Channels and pumps
Sodium, Potassium and Calcium
Ions |
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Term
Nerve Impulse
Chemical signals |
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Definition
At synapses
Neurotransmitters |
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Term
Nerve Impulse - Presynaptic Neuron
Resting State |
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Definition
Not excited, not conducting signal/impulse
Membrane potential = polarized
Negative inside, positive outside cell membrane
-70 mV difference
Ions:
Na+
K+
Cl-
Ca++ |
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Term
Nerve Impulse Presynaptic Neuron
Membrane Potential |
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Definition
Concentration gradient
Ion concentration gradient
Imbalance of types of ions (more Na+ outside than inside)
Electrical gradient
Imbalance of electrical charge (more negative than outside) |
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Term
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Definition
Openings for free ion movement
Usually selective for specific ions |
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Term
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Definition
| Energy-powered pumps to move ions in/out |
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Term
| Membrane Potential (chemical make-up) |
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Definition
Sodium, Chloride - higher outside cell
Potassium - higher inside cell |
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Term
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Definition
| pumps sodium out, potassium in |
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Term
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Definition
Allow Potassium to leave cell
allow chloride in (across concentration gradient)
Maintain negative concentration inside cell |
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Term
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Definition
Cell response to stimuli
Stimuli = chemical mechanical electrical, thermal
Stimulus -> change in membrane potential
Response = nerve impulse/action potential |
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Term
| Action potential sequence |
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Definition
All or nothing
Depolarization
Repolarization
Return to resting state |
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Term
| Depolarization - sequence |
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Definition
Opens sodium channels
Sodium quickly flows in -> large depolarization |
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Term
| Repolarization - sequence |
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Definition
Closure of sodium channels
Opening of potassium channels
Hyperpolarization (K+ flows out)
undershoot: polarization greater than resting state |
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Term
| Return to resting state - sequence |
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Definition
closure of potassium channels
Resting membrane potential returns |
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Term
| Absolute refractory period |
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Definition
the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.
sodium channels inactivated with strong depolarization -> prevent new AP until repolarization occurs |
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Term
| Relative refractory period |
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Definition
the interval immediately following during which initiation of a second action potential is inhibited but not impossible
Hyperpolarized state
AP possible but requires greater depolarization |
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Term
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Definition
Increased internal negativity
Less able to conduct action potential
Inhibitory Post-Synaptic Potential (IPSP) |
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Term
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Definition
decreased negativity
Initiation of action potential
Requires 5-10 mV change from resting potential
Excitatory Post-Synaptic Potential (EPSP) |
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Term
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Definition
Graded
Must reach threshold to initiate AP |
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Term
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Definition
action potential propagated down axon
Continuous depolarization |
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Term
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Definition
speeds up transmission
Action potential "jumps" down axon
Saltatory conduction |
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Term
| what happens when AP reaches axon terminal? |
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Definition
Opens Calcium channels
Exocytosis - synaptic vesicles fuse with presynaptic membrane, release neurotransmitter into synaptic cleft |
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Term
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Definition
Action potential reaches axon terminal
Neurontransmitters bind to post-synaptic receptors
Lock and key mechanism
Binding -> open channels in post-synaptic receptor
ACh, Glutamate -> EPSP due to depolarization
open Na+ channels
GABA -> IPSP due to hyperpolarization
opens Cl- or K+ channels
Ntx recovery and degradation
Ntx bind to receptor, then are released
Reuptake by transporter proteins in presynaptic membrane
destroyed or recycled/repackaged into vesicles
Enzymatic destruction in synaptic cleft
Acetylcholine esterase |
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Term
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Definition
initiated when depolarization reaches threshold
All or nothing
same magnitude each time |
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Term
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Definition
Small EPSP - not strong enough to reach depolarization threshold
Multiple small EPSPs
Spatial summation - from different location/neurons
Temporal summation - from rapid succession of signals |
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Term
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Definition
Reflect stimulus intensity
light touch -> slow repeated APs
high pressure touch -> fast repeated APs |
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Term
| Excitatory + Inhibitory inputs |
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Definition
Net change -> determine response
More EPSPs -> depolarization and action potential
More IPSPs -> hyperpolarization, prevent action potential
Inhibitory - modulate; prevent excitation
Many Inhibitory synapses - axoaxonic, axosomatic |
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Term
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Definition
Excitatory: increase activity
Inhibitory: decrease activity |
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Term
| Action potential reaches axon terminal (list) |
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Definition
1. Synthesis of neurotransmitter and formation of vesicles
2. transport of neurontransmitter down axon
3. action potential travels down the axon
4. action potential causes calcium to enter, evoking release of ntx
5. ntx attaches to receptor, exciting or inhibit post-synaptic neuron
6. separation of ntx molecules from receptors
7. reuptake of neurotransmitter to be recycle
8. vesicles without ntx transported back to cell body |
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Term
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Definition
Chemical released at synapse to transmit signal to post-synaptic neuron
Small molecule transmitters and large molecule transmitters (peptides) |
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Term
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Definition
Acetylcholine (ACh)
Monoamines - produced in brainstem
Dopamine (DA)
Norepinephrine (NE)
Serotonin (5-HT)
Glutamate (Glu)
Gaba-aminobututyric acid (GABA) |
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Term
| Large molecule neurotransmitters |
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Definition
Peptides
Enkephalin, endorphins, substance P |
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Term
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Definition
ACh
Primary PNS ntx - Neuromuscular junction
Muscle contration
controls voluntary movements
also many involuntary muscles |
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Term
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Definition
enzyme to break down ACh at synapse
Allows repetitive nerve impulses
Allows muscle repolarization |
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Term
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Definition
ACh
Antibodies interfere with ACh receptors at neuromuscular junction |
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Term
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Definition
ACh
Affects cholinergic projections to frontal cortex and hippocampus |
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Term
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Definition
DA
Basal Ganglia - interruption/depletion causes movement disorders
Cortex - motivation, cognition (associated with Schizophrenia) |
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Term
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Definition
NE
Noradrenergic cells (contain NE)
Brainstem, thalamus, cortex, limbic system - attention/vigilance
Primary PNS ntx - fight/flight response |
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Term
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Definition
5-HT
95% serotonin = in blood platelets and GI tracts
CNS: various areas
Sleep cycles, depression, modulate pain input |
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Term
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Definition
Primary inhibitory ntx
GABA receptors
Fast inhibitory transmission
Slow modulatory effects
spread through CNS - cortex, hippocampus, cerebellar cortex
Drug treatments - epilepsy, anxiety, insomnia
Huntington's Chorea
Caused by loss of GABA-ergic neurons in basal ganglia |
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Term
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Definition
Primary excitatory ntx in CNX
Fast synaptic transmission
produced by all excitatory neurons
most neurons have glutamate receptors
Excitotoxicity
Toxic to neurons externally
Allows increased Ca influx
Requires re-uptake pumps near synapse
May cause secondary neuronal damage after injury/stroke |
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Term
| Neuronal circuits - types |
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Definition
Divergent circuit
Convergent circuit |
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Term
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Definition
Signal from 1 neuron to many neurons
Amplifies impulse |
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Term
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Definition
| Many inputs (from 1 or many neurons) into 1 post-synaptic neuron |
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Term
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Definition
Inhibition of neighboring cells
Amplifies 1 by shutting down others
localization of touch; visual stimuli |
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Term
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Definition
Self-propagating system
Signal repeated continuously until inhibited from external point |
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Term
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Definition
Modified action of neurotransmitters at synapse
blocking effects
simulating effects (mimics)
Prolonging effects |
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Term
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Definition
Inhibitors
Drug blocks post-synaptic receptors
Prevents ntx from binding
Curare - binds to ACh receptors at neuromuscular junction
ACh unable to bind -> muscle weakness/paralysis
Atropine - blocks ACh at synapse in pupil -> prevent constriction of pupil -> dilation
Botox - prevents vesicles from binding -> prevents ACh release at synapse |
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Term
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Definition
Drug mimics ntx -> brain response as if ntx is present
Nicotine - mimics ACh, binds to ACh receptors and activates post-synaptic neuron |
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Term
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Definition
Blocking breakdown/re-uptake
more ntx in synaptic cleft
blocks enzymes for ntx breakdown
block acetylcholinesterase - ACh survives longer in synaptic cleft
used for treating myasthenia gravis
Block re-uptake back into pre-synaptic cleft. |
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Term
CNS response to injury
Neuronal damage |
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Definition
Axonal (retrograde) reaction
axotomy - degeneration up axon to soma
Wallerian (anterograde) degeneration
Degeneration of axon distally to axon terminal
Begins 12-20 hours post injury
Denervation of muscles within 2-3 days
Myelin degeneration - 7 days to 6 months |
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Term
CNS response to injury
Soma |
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Definition
24-48 hrs post
Swelling of organelles
Nissl substance degenerates
Chromatolysis (continues 8-10 days post)
Degeneration of cell body between axon hillock and nucleus
Pyknosis
Nucleus moves away from center of soma |
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Term
CNS response to injury
General neuronal changes |
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Definition
Increase in RNA and protein synthesis
Regenerate severed axon and prevent cell body death |
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Term
CNS response to injury
Generalized changes |
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Definition
Edema - maximal 90-100 hrs post
Causes by changes to blood-brain barrier
Masks gray/white matter boundaries
Increases intracranial pressure |
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Term
CNS response to injury
Glial cell processes |
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Definition
Hyperplasia - increase in number
Hypertrophy - increase in size
Neutrophils - scavenger white blood cells fight infection
Breakdown of BBB |
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Term
CNS response to injury
Glial cell processes order |
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Definition
Necrotic tissue liquefies
Microglia, astrocytes, other macrophages migrate to site (24 hrs)
Phagocytosis
Microglia eat dead tissue (3+ month process)
Displace pre/post-synaptic terminals
Impair transmission between terminals
Cystic cavity
Gliosis |
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Term
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Definition
resulted from large lesion
fluid filled cavity |
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Term
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Definition
Result of small lesion
Astrocytes from glial scar |
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Term
| Axonal regeneration - PNS |
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Definition
begins 3-4 days post
can be surgically cleaned/re-attached
Schwann cells assist
Fill space between proximal/distal ends
Create tube to guide grown of proximal end
Can re-connect to wrong distal end
"re-wire" signals (pain receptor communicates with touch neuron) |
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Term
| Axonal regeneration - CNS |
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Definition
Minimal re-growth; re-connection
No Schwann cells for structure/guidance
CNS myelin inhibits axonal outgrowth
Inflammation limits regrowth |
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Term
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Definition
Multiple Sclerosis
Autoimmune disease
Degeneration of myelin
Glial proliferation (clean up)
Glia -> plaques
Can trigger axon degeneration
Slowing of nerve conduction |
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Term
Neuropathologies
MS signs/symptoms |
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Definition
Muscle weakness, spasticity, numbness in limbs
Loss of vision; double vision
Vertigo, loss of balance
Later signs
Tremor, ataxia
Dysarthria
Dizziness |
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Term
Neuropathologies: MS
Pattern/damage |
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Definition
Relapsing/remitting pattern
Relapse - increase in number/severity of symptoms
Remit - oligodendrocyte repair
Permanent damage
axonal degeneration |
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Term
Neuropathologies: MS
Patient characteristics |
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Definition
2:1 Female:Male ration
30-60/100,000 cases
more common in northern/colder climates |
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Term
| Neuropathologies: Myasthenia Gravis |
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Definition
Chronic autoimmune disease
progressive weakness with continued muscle use
Loss of ACh receptors - neuromuscular junction
antibodies bind to ACh receptors (prevent ACh function); later destroys receptors |
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Term
Neuropathologies: Myasthenia Gravis
Onset, progression |
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Definition
Onset: graduate
Females more affected before 30 years
Males more affected after 30 years
Progression
Can be slowly progressive
Remission periods can be long |
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Term
Neuropathologies: Myasthenia Gravis
Symptoms |
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Definition
Increasing weakness with muscle use
Diplopia
Ptosis
Weak respiration |
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Term
Neuropathologies: Myasthenia Gravis
Cranial Nerve involvement |
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Definition
Facial expression
Dysphagia
Hypernasality
Dropped jaw |
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Term
Neuropathologies: Myasthenia Gravis
Diagnosis/treatment |
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Definition
Anticholinesterase druges
Neostigmine; Mestinon
Inhibit acetylcholinesterase -> ACh remains in synaptic cleft longer |
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Term
Neuropathologies: Amyotrophic Lateral Sclerosis
Definition |
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Definition
Lou Gherig's disease
ALS
A- no/not
Myo - muscle
Trophic - Growth
Lateral - to the side
Sclerosis - hardening |
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Term
| Neuropathologies: Amyotrophic Lateral Sclerosis |
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Definition
| Degeneration of motor neurons |
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Term
Neuropathologies: Amyotrophic Lateral Sclerosis
Patient characteristics |
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Definition
Males more than females
40-60 years onset
90+% idiopathic (don't know the cause) |
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Term
Neuropathologies: Amyotrophic Lateral Sclerosis
Symptoms |
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Definition
Muscle twitching, craping, stiffness
Slurred speech and difficulty swallowing
muscle weakness in arms/legs
gradually spreads to both head/neck and body
Cognition affected, but later in disease |
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