Neurophysiology BSC

Question 1

soma

Answer 1

cell body
perikaryon
- stains dark due to ribosomes called “nissl bodies”

Question 2

case study: history of imparied glucose tolerance and HTN. recently noticed tingling and burning in feet. blood glucose is 146 (normal is 125). has decreased vibratory sensation and fasciculation in both feet

Answer 2

underlying cause: cumulative damage to neurons and glia = peripheral neuropathy, diabetic neuropathy (type of polyneuropathy)

Question 3

fasciculation

Answer 3

twitch

= decreased motor innervation

Question 4

tingling

Answer 4

PNS, decreased sensory innervation

Question 5

peripheral neuropathy

Answer 5

• positive: pain and dysethesia (abnormal sensations)
• negative: loss of sensation or reflex; weakness and muscle atrophy
• irritative: fasciculations (twitching) and paresthesia (tingling and burning)
• this can involve one nerve or many nn.

Question 6

mononeuropathy

Answer 6

• involving only isolated nn.
• often due to trauma or pressure
• radiculopathy: damaged nerve roots

Question 7

polyneuropathy:

Answer 7

due to metabolites, toxins, demyelinating disease and chronic infections

• can affect the axon, myelin or synapse
• becomes more senstivie to mononeuropathy

Question 8

diabetic neuropathy

Answer 8

• hyperglycemia serves as a trigger: inflammatory, metabolic and ischemic
• pro-oxidative and pro-inflammatory
• affects many cell types, but often causes axonal demylination

Question 9

Parts of PNS

Answer 9

• spinal and cranial nerves

- glial cells: Schwann cells

Question 10

resting membrane potential

Answer 10

-65 mV

Question 11

synaptic potentials

Answer 11

the incoming signal of a neuron that is received at the synapse of the dendrites

Question 12

capacitator of neurons?

Answer 12

the lipid bilayer

- allows for storage of charges on opposite sides

Question 13

resistor of neurons?

Answer 13

ion channels - allow a certain amount of current to flow across the membrane

Question 14

conductance vs. resistance?

Answer 14

conductane = flow of ion across the membrane
resistance = halting of flow of ion across the membrane

Question 15

depolarization

Answer 15

decreased internal negativity

- due to inward Na+ current

Question 16

hyperpolarization

Answer 16

increasing internal negativitiy

- due to outward K+ current

Question 17

time constant

Answer 17

= how long it takes to reach final voltage

• dependent on number of channels: many open channels lead to lower time constant
• results in high conductance and low resistance

Question 18

temporal summation

Answer 18

based on the time constant of the summation

- multiple signals conducted quickly may be summed to result in an AP

Question 19

length constant

Answer 19

the distance required for the current to decline

Question 20

spatial summation

Answer 20

decreased length constant, can result in increased summation of AP’s

Question 21

what types of axons are first affected in neuropathy?

Answer 21

longest axons

“stocking and glove” - results in defects in sensation/strength of hands and feet first

Question 22

autonomic vs. motor loss in PND

Answer 22

motor neurons can be lost causing atrophy
Autonomic neurons can be lost:
- efferent: results in sweat loss, dry, cracked skin
- afferent: changes in senation and pain

Question 23

nodes of ranvier

Answer 23

junction between schwann cells

• high concentration of voltage gated Na+ channels
• allows for saltatory conduction

Question 24

nerve-conduction studies

Answer 24

stimulating electrodes are placed on the skin overlying a nerve

• if the recording is then taken along the nerve: then can measure the APs (SNAP: sensory nerve action potential)
• if placed on muscle, then it is detecting a CAMP, compound motor action potential

Question 25

myelin damage

Answer 25

slowed conduction | ectopic propogation

Question 26

axon damage

Answer 26

failure of propogation ectopic propogation decreased SNAP amplitude

Question 27

PNS regeneration

Answer 27

1. schwann cells downregulate the myelin and the myelin sheath is broken down in response to injury. 2. schwann cells rearrange themselves into endoneurial tubes 3. macrophages phagocytose myelin debris 4. anterograde degeneration of axon occurs (wallerian degeneration: axon distal to wound degenerates) 5. retrograde signaling causes soma to reorganize and organelles are reorganized (chromatolysis): neuron must produce a large amount of amount of proteins 6. during regeneration, many neurites sprout and are guided by schwann cells until a connection is made 7 schwann cell redifferentiate

Question 28

sx: generalized neuronal changes, cognitive decline, headache, vomiting, nausea

Answer 28

could be due to intracranial pressure changes or neuronal swelling

Question 29

oligodendrocytes

Answer 29

white (and gray) matter | - form myelin sheaths

Question 30

astrocytes

Answer 30

provide mechanical and metabolic support and response to injury in CNS - are the endfeet of the CNS that provide a covering of endothelial cells, induce the formation of tight junctions in formation of blood brain barrier - control the brain ECF by buffering glucose and K+ - store glucose and release it for energy - take up excess K+ ; have a lower membrane potential than neurons (-85 mV)

Question 31

microglia

Answer 31

phagocystose things in response to injury in CNS

Question 32

Ependymal cells

Answer 32

line the walls of ventricles and secrete CSF

Question 33

endothelial cells

Answer 33

- in the CNS there are no clefts or fenestrae, they have continuous tight junctions - reduced paracytosis - reduced transcytosis

Question 34

what are the two types of astrocytes?

Answer 34

1. fibrous astrocytes: are found in white matter and are associated with myelin; long thin processes 2. protoplasmic astrocytes: short frilly processes and are found in gray matter

Question 35

primary brain injury

Answer 35

- mechanically induced | i. e. contusions, axonal injury, vascular injury, cranial n. injury

Question 36

secondary brain injury

Answer 36

not mechanically induced, will take 12,24 hours to form | - intracranial hemorrhage, swelling, hypoxic injury, infection, ROS injury

Question 37

Cerebral edema

Answer 37

- net accumulation of water in the brain - glial cells uptake K+. Cl- and water follow into astrocytes. - generalized edema: increased total intracranial pressure; if pressure excedes arterial pressure then blood flow can stop, if occurs slowly it will activate sensors in medulla to increase arterial pressure - focal edema: displaces nearby structures sx: headache, vomiting, altered conviousness, focal neurological problems tx: hyperventilation (resp. alkalosis induces vasoconstriction) or osmolytes like mannitol (draw water out)

Question 38

how are neural scars formed?

Answer 38

reactive gliosis: movement and proliferation of glial cells to the area, can result in scar or plaque formation.

Question 39

excess glutamate....

Answer 39

glutamate can be released by ischemia, anoxia, hypoglycemia or trauma and results in excitotoxicity

Question 40

how does xs glutamate affect the neuron?

Answer 40

- inhibits Na/K ATPase - result in large increase in extracellular K and intracelluar Na - results in accidendtal membrane depol and release of NT

Question 41

how does xs glutamate affect astrocytes?

Answer 41

- astrocytes want to take up glutamate, but to do this they need Na/K ATPase - thus there is diminished glutamate uptake

Question 42

how does xs glutamate affect post-synaptic terminals?

Answer 42

glutamate opens Na and K permeable ion channels | - this leads to neuronal damage

Question 43

how does xs glutamate affect cell swelling

Answer 43

neuron cell bodies and dendrites swell b/c Na+ enters and Cl- and water passively follows

Question 44

fast vs. slow synaptic potential

Answer 44

* fast is most common and involves point-to-point contact through ligand-gated ion channels * slow synaptic potentials are less common. they are diffuse . normally occurs between branched and projecting neurons. requires G protein coupled receptors, can be electrically silent

Question 45

EPSP

Answer 45

Depolarizing response that brings membrane closer to threshold for firing an action potential

Question 46

IPSP

Answer 46

Hyperpolarizing response that moves the membrane away from threshold

Question 47

Potentiation

Answer 47

- occurs with brief, high-freq action potentials occuring over long periods of time - results in presynaptic terminal releasing more NT with each action potential - results in entry of too much Ca2+ and residual Ca2+ increases vesicle exocytosis. - high intracellular Ca2+ induces kinases

Question 48

depression

Answer 48

due to long, high frequency APs, cause depletion of synaptic vesicles or due to low-requency APs: moderate intracelluar Ca2+ levels induce phosphatases

Question 49

short vs. long term synaptic plasticity?

Answer 49

Short-term: Lasting seconds Long-term: Lasting days, weeks or longer Dendritic spines Changes shape, number and diameter Changes electrical properties and substrate concentrations

Question 50

long-term memory

Answer 50

Sensitivity of a synapse to past activity influences long-term effectiveness 1. Long-Term Potentiation: Increases the amplitude of EPSPs 2. Long-Term Depression: Decreases the amplitude of EPSPs