Synaptic Transmission

Question 1

AP are __ or ___

Answer 1

all or none, AP’s are always the same size

Question 2

AP frequency is linearly correlated with what

Answer 2

stimulus intensity and depolarization
more frequent = more intense AP down the axon

Question 3

how does lidocaine affect action potentials

Answer 3

prevents APs by binding to NA channels to impede the transmission of pain (numbing agent that blocks pain)

Question 4

what types of neurons are unmyelinated and small in diameter
what types of neurons are myelinated and large in diameter

Answer 4

unmyelinated/small: type IV motor, type C sensory (slower)
myelinated/large: type 1 or A alpha (faster)

Question 5

nerve fibres can be categorized according to what two things
what are the two classification systems

Answer 5

fibre diameter and conduction velocity
1. based on conduction velocities of different types of motor and sensory nerve fibres
2. for sensory nerve fibres only and is based on diameter and sensory receptors they innervate

Question 6

which nerve fibre classification is unmyelinated
are these nerve fibres large or small in diameter
these fibres play a role in what type of pain

Answer 6

c fibres, small in diameter
slowest when it comes to conduction velocity
diffuse and slow pain

Question 7

in what ways do nerve fibre types differ

Answer 7

respond to treatment/medication differently
differ in stimulus intensity required to activate them

Question 8

which fibres are fastest and play a role in motor and sensory functions
why are they the fastest

Answer 8

A alpha (motor) and A beta (sensory)
they have the thickest diameter and are myelinated

Question 9

which fibres type is the easiest to activate and require the least amount of stimulus to fire
which fibre type requires moderate input to activate
which fibres require a lot of input to activate

Answer 9

A alpha and A beta
A delta
C fibres

Question 10

name the origination and number of the sensory nerve fibres:
1. A alpha
2. A alpha
3. A beta
4. A delta
5. dorsal root C

Answer 10

muscle spindle, annulospiral ending, 1A (largest diameter)
GTO, 1B (largest)
muscle spindle, 2
pain and cold receptors, 3
pain, temperature and other receptors, 4 (smallest)

Question 11

what does electromyography measure and what does it evaluate

Answer 11

measures electrical activity in response to a nerves stimulation of the muscle
evaluates how well and how fast conduction is occurring in specific nerves (measures compound AP or sum of AP of a given fibre)

Question 12

what is EMG used to assess and what does it assist in telling you

Answer 12

neuromuscular abnormalities
assists with localization but doesn’t identify cause

Question 13

what is the typical response and abnormal response of the muscle when the needle is inserted in an EMG study

Answer 13

typical: brief burst of activity
abnormal: twitch or fibrillation

Question 14

why should EMG be used in conjunction with a clinical assessment

Answer 14

because it can lead to misdiagnosis
it is normal for some people to have an absence of a sensory response or fibrillation which may be mistaken for indication of neuropathy

Question 15

what are the two types of response that can occur at the post synaptic terminal

Answer 15

inhibitory (negative change) or excitatory (positive change)

Question 16

which types of synapses are excitatory
synapses can be either excitatory or inhibitory between ___

Answer 16

neuromuscular and neuroglandular
neurons

Question 17

where are excitatory (EPSP) and inhibitory (IPSP) localized
whether or not an EPSP or IPSP occurs depends on what

Answer 17

EPSP: dendritic tree or the soma
IPSP: near or on the soma
the type of receptors that are there

Question 18

what are graded responses
where does summation occur

Answer 18

the adding and subtracting by EPSP (adding) and IPSP (subtracting) until threshold to send an AP is reached
inside the cell

Question 19

EPSP and IPSP can summate either spatially or temporally, explain what each is

Answer 19

spatial: summation due to the release of NT from multiple presynaptic neurons
temporal: frequency at which the synapses are activated over time

Question 20

compare and contrast ionotropic and metabotropic receptors

Answer 20

ionotropic: linked directly to ion channels, immediate effects on post synaptic potential
metabotropic: affects ion channels through intermediates, G protein coupled receptors, slow response following activation

Question 21

what are the two types of receptors acetylcholine can bind to, say whether they are excitatory/inhibitory or ionotropic/metabotropic

Answer 21

nicotinic: excitatory, ionotropic
muscarinic: inhibitory, metabotropic

Question 22

when there are issues with ACh in the basal forebrain and brainstem, there is an effect on what brain functions
what disease would cause impacts on these brain functions
what is the etiology of this disease

Answer 22

learning, memory, arousal and attention
alzheimers disease
plaques and tangles form in the nerves that result in it no longer being functional

Question 23

where in the body is acetylcholine found and which enzyme breaks it down

Answer 23

in the CNS (basal forebrain and brainstem) and the PNS (skeletal NMJ)
autonomic NS (pre and post ganglionic (para)sympathetic neurons)
acetylcholinesterase breaks down acetylcholine at the synaptic cleft

Question 24

medication that inhibits which enzyme is used to treat Alzheimer’s disease

Answer 24

acetylcholinesterase

Question 25

how do glial cells and glutamate interact which types of receptors does glutamate bind to glutamate makes up a majority of the ___ neurons in the ___

Answer 25

glial cells release and take up glutamate ionotropic and metabotropic excitatory, CNS

Question 26

why are elevated levels of glutamate neurotoxic explain how this occurs with neural injury

Answer 26

because glutamate initiates a cascade of cell death when there is injury to the brain the cellular processes in that area stop, one of the processes that stops is the uptake of glutamate out of the cleft so glutamate levels become elevated

Question 27

which neurotransmitter plays a key role in synaptic plasticity

Answer 27

glutamate

Question 28

explain the role of GABA (inhibitory/excitatory?, ionotropic/metabotropic?) GABA is common to ___

Answer 28

is the major inhibitory NT has both ionotropic and metabotropic receptors common to interneurons

Question 29

what is gamma hydroxybutyrate (GHB)?

Answer 29

a naturally occurring NT and precursor to GABA, glutamate and glycine is also a CNS depressant (used as a date rape drug)

Question 30

how are dopamine levels different in individuals with Parkinson's disease and psychiatric disorders in what brain regions is dopamine implicated in

Answer 30

lower dopamine levels, meds containing dopamine can alleviate symptoms implicated in many brain regions (corpus striatum, substantia nigra)

Question 31

where is norepinephrine produced in the CNS and what does NE act as what activities does NE influence

Answer 31

in the locus coeruleus (in pons) acts as a NT and stress hormone in the CNS and PNS sleep (low levels) / wakefulness (high levels), attention, feeding behaviour

Question 32

what structure releases NE in the PNS which drugs block the effects of NE

Answer 32

sympathetic ganglia alpha and beta blockers because they bind to NE receptors

Question 33

where are neuropeptides produced and what do they mediate

Answer 33

in the cell soma with no synthesis at terminals mediators of inflammation and tissue repair

Question 34

what types of nerve fibres do neuropeptides have neuropeptides have ___ and more ___ action and can be ___ or ___ neuropeptides are active in both the ___ and ____

Answer 34

sympathetic and cholinergic slower, prolonged, excitatory, inhibitory CNS and pNS

Question 35

what is substance p where is substance p synthesized and what actions does it have

Answer 35

a neuropeptide dorsal root ganglia vasodilation, increased vascular permeability, protein extravasation after injury (proteins move from blood to tissues to stimulate cell growth) stimulates proliferation of epithelial, vascular and connective tissue

Question 36

what is anterograde axonal transport and what things is it important for

Answer 36

cell body nutrients are carried to the distal end vital for axonal growth during development, maintenance of axonal structure, synthesis and release of NTs

Question 37

what is retrograde axonal transport and what is it important for

Answer 37

distal end of axon back to cell body return of used materials from the terminal to the cell body for restoration and reuse route by which toxins enter the CNS from periphery

Question 38

what does axonal transport do

Answer 38

maintains the integrity of the axon

Question 39

explain the effects of tetanus and how it enters the CNS what muscles does tetanus first attack and what symptoms does this lead to is tetanus localized or general

Answer 39

causes increase in tone and spasms, inhibits motor neurons of the CNS enters the CNS through retrograde axonal transport attacks facial and jaw muscles stiffness of the neck, difficulty swallowing, stiffness in abdominal musculature can be either localized or general

Question 40

what can interfere with transmission and are these effects direct or indirect

Answer 40

drugs, toxins, endogenous compounds, injuries or diseases can be either direct or indirect

Question 41

what is myasthenia gravis what receptors does it affect and what does this condition lead to what is the treatment for this

Answer 41

an acquired autoimmune disorder affecting transmission at the NMJ affects nicotinic ACh receptors leads to skeletal muscle weakness and fatiguability in orbital, oropharyngeal and limb musculature acetylcholinesterase inhibitors (would allow for an increase in the amount of ACh)

Question 42

what NT is active at the NMJ what is botulinum toxin and how does it affect this NT at the NMJ botulinum toxin can be used as a treatment for what conditions

Answer 42

ACh a bacteria that prevents the release of ACh at the NMJ and causes flaccid paralysis which can be fatal severe dystonia or cerebral palsy (both have muscle contractures so the bacteria relaxes these contractures)

Question 43

describe each type of nerve injury and their characteristics (damage, paralysis vs block, wallerian degeneration, example, recovery)

Answer 43

neurapraxia: damage to the sheath but neuron still intact, block in conduction, no wallerian degeneration, compression injury, fast recovery axonotmesis: axon and sheath damaged but connective tissue intact, paralysis, wallerian degeneration, stretch injury, slow recovery neurotmesis: complete nerve damage, paralysis, wallerian degeneration, trauma, recovery may not be possible (may require surgery)

Question 44

damage to which part of the neuron would make recovery impossible loss of ___ is irreparable but ___ can regenerate if cell body is intact

Answer 44

cell bodies neurons, axons

Question 45

regeneration of axons is limited to axons in the CNS or PNS what can assist in repairing an axon to regrow what can occur if there is an issue during the repair of a neuron

Answer 45

PNS Schwann cells develop a neuroma (thickening of nerve tissue and enlargement)

Question 46

what conditions may cause muscle atrophy what does denervation of muscles lead to is muscle atrophy reversible

Answer 46

injury, acute critical illness, cancer, diseases with chronic inflammation, neurological disorders, long term corticosteroid therapy muscle fibre death and muscle atrophy, changes in metabolism or morphology and transmitter receptor production may be reversible depending on the cause and duration of illness

Question 47

intensive care unit acquired weakness (ICUAW) is caused by what what happens to the vascular permeability of the endometrium in ICUAW and what does this allow

Answer 47

axonal neuropathy, myopathy or both increases in permeability allowing toxins to penetrate in the nerve ends

Question 48

what does mechanical ventilation in the ICU change the balance between what can help reduce the severity of ICUAW

Answer 48

protein synthesis and protein degradation (changes fibre composition of the diaphragm) mobility, passive stretching, electrical stimulation

Question 49

what is neuropathy and what are the causes of it give an example of a focal neuropathy

Answer 49

damage to peripheral nerves that result in sensations of numbness, weakness, tingling or pain most common cause is diabetes but can also be infectious/inflammatory diseases, exposure to toxic substances carpal tunnel syndrome

Question 50

what is Guillain barre syndrome what is Charcot Marie tooth disease what is MS

Answer 50

an acquired, acute onset inflammatory peripheral demyelinating neuropathy with axonal sparing hereditary polyneuropathy with demyelination of sensory and motor axons an acquired demyelinating disease of the CNS

Question 51

what changes do we see presynaptically with synaptic plasticity what changes do we see postsynaptically with synaptic plasticity

Answer 51

pre: increase in size of presynaptic terminal, number of axon terminals, quantity of NTs in vesicles post: increase in the receptor zone, in the number of receptors, growth of dendritic spines

Question 52

how can chronic stress affect synaptic plasticity differently in different areas of the brain

Answer 52

pruning in the prefrontal cortex which can impact memory and learning amygdala (emotions and fear response) develops more connections and we have exaggerated responses to fearful situations

Question 53

describe what makes a stress positive, tolerable or toxic

Answer 53

positive: necessary for development and to enable stable and supportive relationships (exercise) tolerable: potentially disruptive, buffered by supportive relationship and safe environments (school) toxic: disrupts brain architecture, increases risk of stress related physical and mental illness (burnout)