Basic Science Flashcards
What are the 5 morphological regions of a neuron?
dendrites soma axon hillock axon synapse
what is the function of dendrites within a neuron?
increase surface area of neuron cell membrane and receives inputs from other neurones
what is the function of the soma of a neuron?
integrates the input signal to generate a net depolarising or hyperpolarising signal
how are the input signals entering a neuron passed from the dendrites to the soma to the axon hillock?
passively
what is the function of the axon hillock?
site of initiation of all-or-none AP
what are the 2 main types of pain?
nociceptive pain
neuropathic pain
compare nociceptive and neuropathic pain?
nociceptive- an appropriate physiological response to painful stimuli via intact nervous system
neuropathic- an inappropriate response to caused by a dysfunction in the nervous system
what is allodynia?
pain from a non-painful stimulus
what is hyperalgesia?
more pain than expected from a painful stimulus
what type of pain do NSAIDs mainly act on?
nociceptive pain
what is the mode of action of NSAIDs?
inhibit COX
reduce prostaglandin synthesis
what are the 3 main side effects of NSAIDs?
- GI irritation/bleeding
- renal toxicity
- cardiovascular side effects (COX 2)
what effect does paracetamol have in addition to its analgesic effects?
antipyretic
what is the mode of action of paracetamol?
inhibition of central prostaglandin synthesis
what is the main side effect of paracetamol?
risk of liver damage
what type of pain do opiods mainly act on?
nociceptive pain
what is the mode of action of opiods?
activate the endogenous analgesic system
modulate pain perception
reduce pain signal transmission
what are the 6 main side effects of opiods?
nausea vomiting constipation dizziness/vertigo drowsiness dry skin/pruritus
what type of pain do tricyclic antidepressants mainly act on?
neuropathic pain
what class of pain medication works best for complex regional pain syndrome?
tricyclic antidepressants
what class of pain medication works best for tension headaches?
tricyclic antidepressants
what are the 6 main side effects of tricyclic antidepressants?
constipation dry mouth drowsiness abnormalities in heart rate/rhythm insomnia increased appetite
what type of pain do SNRI/SSRIs mainly act on?
neuropathic pain
what is the mode of action of SNRI/SSRIs?
selectively inhibit reuptake of noradrenaline or serotonin
what are the 7 main side effects of SNRI/SSRIs?
nausea vomiting constipation drowsiness dry mouth increased sweating loss of appetite
what type of pain do anticonvulsants mainly act on?
neuropathic pain
what is the mode of action of gabapentin? (anticonvulsant)
binds to presynaptic voltage-dependent calcium channels
what is the mode of action of pregabalin? (anticonvulsant)
interacts with N-type calcium channels
what is the mode of action of carbamazepine? (anticonvulsant)
block Na and Ca channels
what pain fibres do topical analgesics work on?
A-delta fibres
C-fibres
what are the main 3 side effects of topical analgesics?
rash
pruritus
erythema
what are the 6 main side effects of anti-convulsants?
sedation dizziness ataxia peripheral oedema nausea weight gain
what is ataxia?
loss of full control of body movements
in a neuron what is the rough ER known as?
nissl substance
what is the function of an axon with a neuron?
conducts APs to other neurones
mediates transport of materials between soma and presynaptic terminal
what are the 2 main ways of axoplasmi transport within a neuron?
anterograde
retrograde
what are the 2 rates of axoplasmic transport?
fast
slow
how does polio get into the soma of a neuron?
gets into presynaptic terminal and then via retrograde axoplasmic transport reaches the soma
what is a neurite of a neuron?
a process arising from the soma
what are the 4 main type of neuron?
unipolar
pseudounipolar
bipolar
multipolar
how many neurites does a unipolar neuron have?
1 neurite
how many neurites does a pseudounipolar neuron have?
1 neurite
how many neurites does a bipolar neuron have?
2 neurites
how many neurites does a multipolar neuron have?
3+ neurites
compare a unipolar neuron to a pseudounipolar neuron?
both have one neurite, but the pseudounipolar neurones neurite bifurcates into two axons
what is the normal resting membrane potential?
-70mV
what is the membrane potential threshold for voltage activated Na channels to open?
-60mV
in the upstroke of an AP in a neuron, what is the resting membrane potential?
+40mV
influx of what ion causes the upstroke in an AP?
influx of Na
efflux of what ion causes the dowstroke in an AP?
efflux of K
what does myelin do to the passive current spread of APs?
increases speed
what cells provide the myelin sheath in the PNS?
schwann cells
what cells provide the myelin sheath in the CNS?
oligodendrocytes
compare schwann cells and oligodendrocytes in how they insulate axons?
many schwann cells needed for one axon
one oligodendrocyte surrounds many axons
what are nodes of ranvier?
gaps in the myelin sheath
what type of conduction occurs through the nodes of ranvier?
saltatory conduction
what type of cells are schwann cells and oligodendrocytes?
macroglia
does MS cause demyelination in the CNS or PNS?
CNS
does Guillian-Barre syndrome cause demyelination in the CNS or PNS?
PNS
what are the 3 main types of synapse?
axodendritic
axosomatic
axoaxonic
what is an axodendritic synapse?
synapse between an axon of one neuron and the dendrite of another
what is an axosomatic synapse?
synapse between an axon of one neuron and the soma of another
what is an axoaxonic synapse?
synapse between an aon of one neuron and the axon of another
what is the most common type of synapse?
axodendritic
how are synapses functionally classified?
inhibitory or excitatory
is an excitatory response depolarising or hyperpolarising?
depolarising
is an inhibitory response depolarising or hyperpolarising?
hyperpolarising
what is the main transmitter used in excitatory synapses in the CNS?
glutamate
what are the main transmitters used in the inhibitory synapses in the CNS?
GABA or glycine
what receptors does glutamate activate?
post-synaptic cation selective, ionotropic, glutamate receptors
what receptors do GABA or glucine activate?
post-synaptic anion selective, ionotropic GABA or glycine receptors
what are the major amino acid neurotransmitters in the CNS?
glutamate, GABA and glycine
what charge influx occurs when glutamate activates the cation selective, ionotropic glutamate receptors on the postsynaptic neuron? what does this cause?
positive influx
depolarisation
what occurs when GABA or glycine activates the anion selective ionotropic GABA/glycine receptors on the postsynaptic neuron? what does this cause?
negative influx
hyperpolarisation
what are pre and post synaptic membranes separated by?
synaptic cleft
what is spatial summation?
many inputs converge upon a neuron to determine its output
what is temporal summation?
output determined by the frequency of APs of a single input
compare the type of vesicles amino acids, amines and peptides are released from?
amino acids and amines- synaptic vesicles
peptides- secretory vesicles
compare ionotropic ligand-gated ion channels and G-protein coupled receptors in terms of speed of neurotransmission?
ionotropic ligand gated ion channels- fast
GPCR- slow
what causes the release of neurotransmitter from vesicles into the synaptic cleft?
influx of Ca through voltage gated Ca channels
after neurotransmitters activate receptors on the post-synaptic membrane, what are the 2 things that can happen to them?
- enzyme-mediate inactivation of transmitter
2. reuptake of transmitter
compare glycine, glutamate, GABA and amines in terms of what cells make them?
glycine and glutamate- all cell
GABA, amines- neurones specifically
how are enzymes that are synthesised in the cell body of neuron transported to the presynaptic terminal?
axoplasmic transport via microtubules
at resting membrane potential, describe the flow of Na, Ca, Cl and K if they were to move freely?
Na flows inward
Ca flows inward
Cl flows inward
K flows outward
do drugs that are agonists of Na channels cause excitation or inhibition of neurotransmission?
excitation
do drugs that are antagonists of Na channels cause excitation or inhibition of neurotransmission?
inhibition
do drugs that are agonist of K channels cause excitation or inhibition of neurotransmission?
inhibition
do drugs that are antagonists of K channels cause excitation or inhibition of neurotransmission?
excitation
compare ionotropic and metabotropic receptors?
ionotropic receptors are direct signalling- fast
metanotropic receptors are indirect signalling- slow
what neurotransmitters signal via non-NMDA ionotropic receptors?
AMPA
kainate
compare non-NMDA and NMDA in terms of what components within an excitatory synaptic potential they mediate?
non-NMDA- fast component
NMDA- slow component
what are the 2 types of receptor GABA activates?
ionotropic GABAa receptor
metabotropic GABAb receptor
what channel does the ionotropic GABAa receptor operate?
Cl-
what channel does the metabotropic GABAb receptor operate?
usually K+ channel
what do benzodiazepines do to the GABAa receptor?
positive modulator (allosterically) therefore increase Cl- entry to enhance inhibition
what is a quanta?
amount of neurotransmitter released from a single vesicle
what are the 2 types of low threshold sensory units?
- low threshold mechanoreceptors
- low threshold thermoreceptors
what are the 4 types of high threshold sensory units?
- high threshold mechanoreceptors (mechanical nociceptors)
- thermal nociceptors
- chemical nociceptors
- polymodal nociceptors
what do polymodal nociceptors respond to?
at least 2 of:
- high intenity mechanical stimuli
- extreme degrees of heat
- substances in tissue
what are the 4 types of axons arising from skin/muscle?
Aa/I
Ab/II
Ad/III
C/IV
as you move from axon group I to IV, what happens to myelination and conduction velocity?
degree of myelination decreases
conduction velocity increases
what group of axons are involved in proprioception of skeletal muscles?
Aa/I
what group of axons are involved in temperature pain and itch?
C/IV
what group of axons are involved in pain and temperature?
Ad/III
what group of axons are involved in low intensity mechanical stimulation of skin?
Ab/II
how is the receptive field of a neurone measured?
two-point discrimination
what is the major difference between meissner’s corpuscles and merkel’s discs in terms of location on skin?
meissner’s corpuscles are not present on hairy skin
merkel’s disc are
what is brown-sequard syndrome?
ipsilateral hemiplegia with contralateral pain and temperature deficits
when does the dorsal column medial leminscal pathway cross the spinal cord?
great sensory decussation in the brainstem
when does the spinothalmic tract cross the spinal cord?
at level of output from the spinal cord
what are the dorsal column medial leminscal pathways formed by?
fasciculus gracilis
fasciculus cuneatus
which is more medial- fasciculus gracilis or fasciculus cuneatus?
fasciculus gracilis
compare sensory input to T6 and below with above T6
T6 and below- fasciculus gracilis
above- fasciculus cuneatus
what is the major route by which touch and proprioceptive information ascends to the cerebral cortex?
dorsal column medial lemniscal pathway
what horn within the spinal cord do the first order neurones in the dorsal column medial lemniscal pathway enter?
dorsal horn
where do the first order neurones in the dorsal column medial lemniscal synapse?
dorsal column gracile nucleus and cuneate nucleus
once the second order neurones in the dorsal column medial lemniscal pathway cross at the great sensory decussation where do they ascend?
medial lemniscus
once the second order neurones in the dorsal column medial lemniscal pathway ascend the medial lemniscus, where do they synapse?
ventral posteriolateral nucleus of the thalamus
where do the third order neurones in the dorsal column medial lemniscal pathway synapse?
primary somatosensory cortex (S1)
what replaces the dorsal column medial lemniscal pathway in conveying sensory information from the anterior head?
trigeminal system
what is stereognosis?
ability to recognise an object by feeling it
what are the 5 main capabilities of the dorsal column medial lemniscal pathway?
stereognosis vibration detection fine touch conscious proprioception weight discrimination
what are the 3 divisions of the trigeminal nerve?
V1 ophthalmic
V2 maxillary
V3 mandibular
where do primary neurones in the trigeminal system synapse?
in chief sensory nucleus of spinal nucleus
where do secondary neurones in the trigeminal system synapse?
ventroposteriomedial nucleus of the thalamus
where do third order neurones in the trigeminal system synapse?
cortex
where is the somatosensory cortex located?
in the post central gyrus of the parietal cortex
where is the post central gyrus of the parietal cortex in relation to the central sulcus?
post central gyrus of the parietal cortex is immediately posterior to the parietal cortex
what are the 4 areas of the somatosensory cortex?
brodmann areas 1, 2, 3a, 3b
what percentages of input from the ventral posteriomedial go to the brodmann areas of the somatosensory cortex?
30% to BA 1 and 2
70% to BA 3a and 3b
where does the input for brodmann area 1 come from?
cutaneous input
where does the input for brodmann area 2 come from?
joint afferents, golgi tendon organs, deep tissues
where does the input for brodmann area 3a come from?
proprioreceptors (muscle spindles)
where does the input for brodmann area 3b come from?
cutaneous receptors
what does brodmann area 1 sense?
texture discrimination
what does brodmann area 2 sense?
object perception (ie sterognosis)
what does brodmann area 3a sense?
body position
what does brodmann area 3b sense?
touch
how many layers are within the somatosensory cortex?
six cell layers
thalamic inputs to the somatosentsory cortex terminate mainly on neurnes within which layer?
layer IV
if an area of the body is amputed, what happens to the area of somatosensory cortex representing the finger?
utilised by other sensoryy inputs
what happens to the area of somatosensory cortex representing an area of the body that has a lot of sensory activity?
slowly increases relatively
what do alpha motor neurones innervate?
a bulk of muscle fibres within a muscle
what do gamma motor neurones innervate?
muscle spindle fibres
axons of lower motor neurones leave the spinal cord from which spinal roots?
ventral roots
ventral roots join dorsal roots to form what nerves?
mixed spinal nerves
what type of nerve fibres do mixed spinal nerves consist of?
sensory and motor fibres
what are the 2 enlargements of motor neurone bundles within the spinal cord?
cervical enlargment
lumbar enlargement
what does the cervical enlargement of motor neurones supply?
the arm
what does the lumbar enlargement of motor neurones supply?
the leg
what is the smallest functional component of the motor system?
motor unit
what does a motor unit consist of?
alpha motor neurone and all of the skeletal muscle fibres that it innervates
what is the name for a collection of alpha motor neurones that innervate a single muscle?
motor neurone pool
what are the 2 principles that grades the force of muscle contraction?
- frequency of APs from the alpha motor neuron
- recruitement of additional synergistic motor units
within the ventral horn, where are LMNs innervating axial muscles in relation to LMNs innervating distal muscles?
LMNs innervating axial muscles are medial to those innervating distal muscles
within the ventral horn, where are the LMNs innervating flexors in relation to LMNs innervating extensors?
LMNs innervating flexors are dorsal to those innervating extensors
compare unfused tetani to fused tetani?
unfused tetani- time for muscle relaxation between contractions
fused tetani- no time for relaxation between contractions
compare the soma diameters of the alpha motor neurones of small motor units compared with larger motor units?
the smaller the motor uni the smaller the soma of the alpha motor unit
what are the main 2 classes of skeletal muscle fibres?
slow oxidative (type 1) fast fibres (type 2)
what are the 2 types of fast skeletal muscle fibres?
type 2a
type 2b
how is ATP derived in type 1 skeletal muscle fibres?
oxidative phosphorylation
how is ATP derived in type 2a skeletal muscle fibres?
oxidative phosphorylation
how is ATP derived in type 2b skeletal muscle fibres?
from glycolysis
why are type 1 skeletal muscles red in colour?
high myoglobin content
compare speed of contraction of type 1, 2a and 2b skeletal muscles fibres?
1- slow
2a and 2b- fast
compare type 1, 2a and 2b skeletal muscles in the ability to fatigue?
1- fatigue resistant
2a- fatigue resistant
2b- not fatigue resistant
what are the 3 types of motor units?
slow
fatigue resistant
fast fatiguing
compare type 1, 2a and 2b skeletal muscles in terms of size of alpha motor neuron?
1- small a-MN
2a- intermediate a-MN
2b- large
what happens to the AP threshold as the size of the alpha-motor neuron increases? (Henneman Size Principle)
AP threshold increases
what is the myotatic reflex?
when a muscle is stretched, it contracts
what sensory organ registers change in length of a muscle?
muscle spindle fibre
compare intrafusal and extrafusal muscle fibres in terms of ability to generate muscle force?
intrafusal- don’t generate force
extrafusal- generate force
what type of reflex arc is the myotatic reflex?
monosynaptic reflex arc
what neurotransmitter mediates the myotatic reflex?
release of glutamate (excitatory)
what spinal cord level is tested by the supinator reflex?
C5/6
what spinal cord level is tested by the biceps reflex?
C5/6
what spinal cord level is tested by the triceps reflex?
C7
what spinal cord level is tested by the quadriceps reflex?
L3/4
what spinal cord level is tested by the gastrocnemius reflex?
S1
during voluntatry movement, why are a-MN and y-MN normally co-activated?
so that the intrafusal muscle fibres contract in parallel with the extrafusal fibres, stops spindle going slack and therefore maintains sensitivity
where are golgi tendon organs located?
at junction of muscle and tendon
what is the function of golgi tendon organs?
regulate muscle tension to protect from overload
what is the inverse myotactic reflex?
contraction of skeletal muscle causes muscle to relax
what are the components of the inverse myotactic reflex?
-Ib afferent nerve which innervates golgi tendon organ
and synapses inhibitory interneurone
which causes alpha motor neurone to relax
where are the 3 main organs/cells/receptors that proprioceptive information arises from?
- muscle spindles
- golgi tendon organs
- joint receptors
what type of interneurons mediate the inverse myotatic response?
inhibitory interneurons
what type of interneurones mediate reciprocal inhibition between extensor and flexor muscles?
inhibitory interneurons
what type of interneurons mediate the flexor reflex?
excitatory interneurons and inhibitory interneurons
what is the flexor reflex?
when a limb flexes in response to noxious stimuli
what type of interneurons mediate the crossed extensor reflex?
excitatory interneurons and inhibitory interneurons
what is the crossed extensor reflex?
during flexor reflex, the contralateral limb extends in order to maintain balance
what are the 2 important descending spinal tracts?
lateral spinal tracts
ventromedial (/anteromedial) spinal tracts
what part of the brain are the lateral descending spinal tracts under control of?
cerebral cortex
what part of the brain are the venteromedial descending spinal tracts under control of?
brainstem
what is the function of the lateral descending spinal tracts?
voluntary control of distal muscles, eg for small skilled movements
what is the function of the ventromedial descending spinal tracts?
posture and locomotion
what is the major lateral descending spinal tract?
the corticospinal (or pyramidal) tract
where do the fibres from the corticospinal tract cross?
85% cross in the medulla
15% cross at level of exit
for the fibres of the corticospinal tract which cross at the medulla, what is this tract now named?
lateral corticospinal tract
for the fibres of the corticospinal tract which dont cross at the medulla, what is this tract now named?
ventral corticospinal tract
compare how far axons from the lateral vestibular nucleus and the medial vestibular nucleus travel down the spinal cord?
lateral -down to lumbar spinal cord
medial - down to cervical spinal cord
what is the function of the lateral vestibulospinal tract?
helps hold body upright by facilitating antigravity muscles
what is the function of the medial vestibulospinal tract?
head movements
compare skin, muscle and viscera in terms of how localised pain is?
skin- well localised
muscle- poorly localised
viscera- poorly localised
what are nociceptors activated by?
intense noxious or damaging stimuli
where are nociceptor cell bodies located?
dorsal root ganglia or trigeminal ganglia
what order neurones are nociceptors?
first order neurones
what sensory fibres do nociceptors comprise of?
Ad and C fibres
what kind of noxious stimuli do Ad fibres respond to?
noxious mechanical and thermal stimuli
what kind of noxious stimuli do C fibres respond to?
all noxious stimuli (polymodal)
compare Ad and C fibres response time to noxious stimuli?
Ad- fast
C- slow
where are soma of trigeminal sensory neurones located?
trigeminal sensory ganglion
the second order neurones of the trigeminal system project to the ventroposteriomedial nucleus of the thalamus via what?
trigeminal lemniscus
the third order neurones of the trigeminal system project to the cortex via what?
thalamocortical neurones
what is CT contrast determined by?
electron density
what artificial contrast agents can be used on CT scan?
injected iodine based agents
why do iodine based agents not pass into the brain?
because of the blood brain barrier
if iodine based contrast agents cannot get into the brain, why are they used in brain CT?
because if there is enhancement (whiteness) it shows that the blood brain barrier has been disrupted (some pathology)
how long after a CT angiogram will the CT venogram occur?
30 seconds
what is MRI contrast deterined by?
Proton density, T1 and T2
what artificial contrast material can be used in T1 weighted MRI?
injected gadolinium compounds
compare bone detail of CT and MRI?
CT has better bone detail
which is generally more tolerated by patients- CT or MRI?
CT
what is the most common cause of spontaneous subarachnoid haemorrhage?
ruptured aneurysm
what investigation is needed to rule out a subarachnoid haemorrhage if CT scan is negative?
lumbar puncture
what are the 2 main methods of aneurysm treatment?
craniotomy and clipping of aneurysm
endovascular treatment
which form of imaging (CT or MRI) is compatible with most ICU/emergency equipment?
CT
what type of inheritance is duchennes muscular dystrophy?
X-linked recessive
what type of inheritance is huntingtons disease?
autosomal dominant
what area of childhood development is delayed in duchennes muscular dystrophy?
delay in motor development
at what age does the weakness of muscle start in duchennes muscular dystrophy?
3-4 years
why do patients with duchennes muscular dystrophy die in their 20s?
death from involvement of respiratory and cardiac muscles
in both duchennes and beckers muscular dystrophy, what happens to the calves?
calf hypertrophy
what gene is affected in duchennes muscular dystrophy?
dystrophin gene
what marker is very raised in muscular dystrophys?
serum creatinine kinase
what is dystonia?
abnormal muscle tone
what is the genetic defect in huntingtons disease?
repeated CAG codes (codes for glutamine)
what is the most common cause of dementia?
alzheimers
what are the 3 main pathologies within the brain that lead to alzheimer disease?
- loss of cortical neurones
- neurofibrillary tangles (intracellular)
- senile plaques (Extracellular)
what are the senile plaques in alzheimers made of?
amyloid B protein
amyloid B protein is a fragment of the product of what protein?
amyloid precursor protein
what chromosome is the gene for amyloid precursor protein?
chromosome 21
what apolipoprotein allele predisposes to alzheimers disease?
apolipoprotein E4
what are the 2 distinct processes of sensitisation of the nociceptive pathway following tissue damage?
peripheral sensitisation
central sensitisation
does peripheral sensitisation after tissue damage cause primary or secondary hyperalgesia?
primary hyperalgesia
does central sensitisation after tissue damage cause primary or secondary hyperalgesia?
secondary hyperalgesia
which causes allodynia after tissue damage- peripheral or central sensitisation?
central sensitisation
which type of pain sensitisation is the cause of persistant pain after tissue healing?
central sensitisation
what are the 2 nociceptive tracts?
spinothalmic tract
spinoreticular tract
where in the spinal column are the nociceptive tracts?
anterolateral spinal cord
within the dorsal horn of the spinal cord, sensory primary afferent nerves terminate at what?
the laminae of rexed (I- V)
what is located in the dorsal root ganglia?
cell bodies of primary afferent sensory neurones
in which lamina of rexed do nociceptive C fibres terminate?
laminae I and II
in which lamina of rexed do nociceptive Ae terminate?
laminae I, II and V
what type of pain does the spinoreticular tract mainly transmit?
slow C-fibre pain
what type of pain does the spinothalmic tract mainly transmit?
fast fibre pain
where do second order neurones of the spinothalmic tract terminate?
posterior and ventroposterior thalamus
where do second order neurones of the spinoreticular tract terminate?
reticular nuclei in the brainstem
within the spinothalmic tract, what neurones relay the signal from the thalamus to the primary somatosensory cortex?
thalamocortical neurones
within the spinoreticular tract, what neurones relay the signal from the reticular formation to the thalamus?
reticulothalamic tracts
within the spinoreticular tract, what neurones relay the signal from the thalamus to the limbic areas of the forebrain?
thalamocortical neurones
why does ‘rubbing it better’ actually help with pain?
counter-stimulation analgesia
-stimulation of non-nociceptive afferents activates inhibitory interneurones that suppress firing of the nociceptive pathway
how do TENS machines work?
counter-stimulation analgesia
-stimulation of non-nociceptive afferents activate inhibitory interneurones that suppress firing of the nociceptive pain pathway
how do NSAID reduce nociception?
act at site of injury to decrease nociception sensitisation in inflammation
how do local anaesthetics reduce nociception?
block nerve conduction
how do opiods reduce nociception?
modify transmission of nociceptive signals in the dorsal horn of the spinal cord and activating descending inhibitory controls
what is step 1 of the WHO analgesic ladder?
paracetamol or NSAID
what is step 2 of the WHO analgesic ladder?
NSAID + weak opiod
what is step 3 of the WHO analgesic ladder?
NSAID + strong opiod
what receptors mediate opiod action?
G protein coupled opiod receptors
what 2 things occur when opiods bind to G protein coupled opiod receptors?
- inhibition of voltage-activated Ca channels on presynaptic neurone (suppresses neurotransmitter release from nociceptor terminal)
- opening of K channels on postsynaptic neurone (hyperpolarises cell so suppresses neurone excitation)
what medical condition should you avoid tramadol in?
patients with epilepsy
what drugs can be used to reverse opiod toxicity?
naloxone naltrexone (longer half life)
are aspirin, ibuprofen, naproxen, diclofenac and indometacin COX2-selective inhibitors or non selective inhibitors?
non-selective
what does inhibiting COX 1/2 do to rate of prostaglandin synthesis?
decreases synthesis
what specific prostaglandin is involed in sensitisation of nociceptive neurones?
PGE2
does inhibition of COX1 or COX2 cause GI toxicity?
inhibition of COX 1
what anti-convulsant drug is often used in painful diabetic neuropathy?
pregabalin
what anti-convulsant drug is used in migraine prophylaxis?
gabapentin
how do tricyclic antidepressants work?
act centrally by decreasing reuptake of noradrenaline
what drug is first line treatment in controlling trigeminal neuralgia?
carbamazepine
what is the function of the nodes of ranvier?
increases conduction speed
why are neurones particularly suscpetible to hypoxia?
cannot generate energy through anaebolic glycolysis
what are the 4 main neuronal responses to injury/disease?
acute neuronal injury
simple neuronal atrophy
sub-cellular alterations
axonal reaction
what is an axonal reaction?
a reaction within the cell body that is associated with axonal injury
why does the cell body of a neurone swell and the nucleus become peripherally displaced in response to axonal injury?
increased RNA and protein synthesis
in response to axonal injury, what way does the degeneration of the axon occur?
anterograde degeneration of axon distal to site of injury
what happens to the myelin sheath in response to axonal injury?
breakdown
what happens to the number of astrocytes in response to neuronal injury?
increases
what is gliosis?
proliferation of astrocytes as a reactive response to injury
what is the most important histopathological indicator of CNS damage?
gliosis
why do microglia proliferate in response to injury?
to phagocytose the debris of dying neurones (neuronphagia)
what are the two organs which autoregulate their blood supply?
brain and kidneys
above and below what BP, are the brain/kidneys unable to regulate their blood flow?
below DBP 50mmHg
above DBP 130mmHg
within the brain, what happens to the vasculature in response to hypotension?
dilates to maintain blood flow
within the brain, what happens to the vasculature in response to hypertension?
constricts to maintain blood flow
what lobe is affected in an anterior cerebral artery stroke?
frontal lobe
what is aphasia/dysphasia?
language disorder
in a middle cerebral artery stoke, what is an important determinant of how bad the signs/symptoms will be?
if dominant or non-dominant side is affected
why are brainstem infarcts life threatening?
because cardiorespiratory centres might be affected
what part of the brain is affected in webers syndrome?
midbrain
what part of the brain is affected in medial and lateral inferior pontine syndromes?
pons
what part of the brain is affected in lateral medullary syndrome?
medulla
what visual field defect can occur with an infarct causing damage to the occipital lobe?
homonymous hemianopia with macular sparing
what kind of gait is acquired in a infarct affecting the cerebellum?
ataxic gait
what is an intention tremor?
a tremor which is not present at rest but is worse as you are trying to do something
what are watershed areas within the brain?
boundary areas of where the cerebral arteries meet
when do watershed infarcts occur?
fall in blood pressure
what lobe of the cerebrum is affected by a posterior cerebral artery infarct?
occipital
why do haemorrhages within the brain cause ischaemia?
- blood vessel goes into spasm
- can act like a SOL causing increased ICP resulting in impaired blood flow to the brain
what is the strongest risk factor for a stroke caused by cerebral haemorrhage?
hypertension
what are arteriovenous malformations?
failure in normal development of an artery leading to high pressures within the vein
-suscpetible to tearing
in mild and moderate ischaemia to the brain, what cells are first to be lost?
neurones
what is a stroke?
sudden disturbance of cerebral function of vascular origin that causes death or lasts over 24 hours
what is a TIA?
sudden disturbance in cerebral function which lasts less than 24 hours
which is more common- stroke due to infarction or haemorrhage?
infarction
what are the 2 most common originating sites for an embolism causing stroke?
heart and carotid arteries
which cerebral arteries are most likely to be affected by embolic strokes?
middle cerebral arteries
what are the 2 main complications of atheroma?
thrombosis
aneurysm formation
why do cystic fluid filled spaces form as a consequence of cerebral infarct?
as cells die, the liquid phospholipids get left behind- this leaves fluid filled cysts
what is the most common cause of a spontaneous subarachnoid haemorrhage?
rupture of saccular/berry aneurysm
where do most saccular/berry aneurysms occur?
arterial bifurcations at internal carotid artery
what life saving procedure can be done for a saccular aneurysm?
clipping
what is the onset like for a subarachnoid haemorrhage?
abrupt
what are lacunes/lacunar infarcts?
small cavities found in the basal ganglia, thalamus and pons
who are lacunes/lacunar infarcts found in?
elderly patients or hypertensives (mainly)
when can hypertensive encephalopathy occur?
when severe hypertension exceeds the upper limit of autoregulation
what kind of dementia is associated with hypertension?
multi-infarct dementia
accumulation of lacunar infarcts
what demyelinating condition can you get post measles?
subacute sclerosing panencephalitis
does MS affect white or grey matter?
white matter
what can you see on a cut-section of the brain of a patient with MS?
plaques
areas of demyelination
describe the plaques of acute MS?
yellow/brown with an ill-defined edge
describe the plaques of chronic MS?
grey/brown and well demarcated
why is there an increased incidence of dementia in Downs syndrome?
because the genes involved are on chromosome 21 (downs is trisomy 21)
what lobe is generally spared of atrophy in Alzheimers?
occipital lobe
what do you see when staining amyloid with congo red and then looking at it under polarised light?
apple green birefringence
what protein is very commonly found in traumatic dementia especially?
tau protein
what are the hallmarks of dementia with Lewy bodies?
hallucinations and fluctuating levels of attention
what is the pathogenesis of dementia with lewy bodies?
degeneration of the substantia nigra
lewy bodies found in remaining nerve cells
cortical atrophy
what is the age of Huntingtons disease onset?
35-50 years old
what is the inheritance pattern of huntingtons disease?
autosomal dominant
what gene is involved in huntingtons disease?
huntingtin gene
what is the triad of clinical features for huntingtons disease?
emotional, cognitive and motor disturbance
what is myoclonus?
jerky contraction of groups of muscles
at what age is the onset of Pick’s disease?
50-60 years old
in Picks disease, what is the frontal lobe function that has very prominent deterioration?
personality and social
what lobes are mainy affected in Pick’s disease?
frontal and temporal lobes
what are the histological hallmarks of Pick’s disease?
pick’s cells (swollen neurones)
pick’s bodies (intracytoplasmic filamentous inclusions)
compare the progression of alzheimers and vascular dementia?
alzheimers is continuously progressive
vascular dementia has an abrupt onset with stepwise progression
how do the ossicles within th emiddle ear correct for the loss of amplitude that occurs within the fluid in the cochlea?
impedance matching
by increasing sound pressure (to match the loss that occurs later)
what are the 3 mechanisms by which the ossicles of the middle ear impedance match? (ie increase dBs)
- ratio of tympanic membrane to stapes footplate (20:1)
- lever action of ossicles
- buckling of tympanic membrane
what membrane separates the scala vestibuli from the scala media?
reissner’s membrane
what membrane separates the scala media from the scala tympani?
basilar membrane
where does transduction occur in the inner ear?
organ of corti
where do the scala vestibuli and the scala tympani connect?
at helicotrema
what window does the scala vestibuli meet?
oval window
what window does the scala tympani meet?
round window
as the basilar membrane goes along (and increases in width), what frequency sound waves correspond to it?
decreasing frequency of sound waves
which auditory receptor hair cells are most abundant- inner or outer hair cells?
outer hair cells
what separates the inner and outer hair cells?
rods of corti
what are inner and outer hair cells?
auditory receptors with sterocilia
which two membranes within the inner ear do the hair cells stretch between?
basilar membrane and tectorial membrane
is the kinocilium directly before or after the stereocilia on a hair cell?
directly after
how does hair cell transduction occur? (ie how is an AP formed?)
force towards the kinocilium opens cation channels
K+ enters causing depolarisation
force then goes back away from the kinocilium
cation channels close
repolarisation
the bending of the hair cells in the cochlea causes vibration of which membrane?
tectorial membrane
which cells within the cochlea release neurotransmitter?
hair cells
compare inner and outer hair cells in terms of which sends afferent signals and which receives efferent signals?
inner hair cells- send afferent signals to auditory nerve
outer hair cells- receive efferent signals
the efferent signals that outer hair cells receive control what?
stiffness
to amplify membrane vibration
compare inner and outer hair cells in terms of the how many hair cells are innervated by a single nerve?
inner hair cells- one cell innervates many nerves
outer hair cells- many nerves innervate one hair cell
what is the motor protein within the outer hair cells composed of?
prestin
what is the function of the motor protein within outer hair cells?
changes the length of the outer hair cells
why is it important that the outer hair cells change in length?
increased vibration of basilar membrane so increased bending of inner hair cells
why can furosemide cause hearing problems?
inactivates the membrane motor within the outer hair cells
does place code or temporal code operate for pitches under 5kHz?
temporal code for under 5kHz
does place code or temporal code operate for pitches above 5kHz?
place code
from cochlea to the auditory cortex, what the is central auditory pathway?
eight cranial nerve
cochlear nucleus superior olivary complex lateral lemniscus inferior colliculus medial geniculate body
where do sound waves from both ears merge?
superior olivary complex
what are the 3 cochlear nuclei?
dorsal cochlear nucleus
posteroventral cochlear nucleus
anteroventral cochlear nucleus
what part of the vestibular system senses head rotation?
semicircular canals
what part of the vestibular system senses translational motion and gravity?
saccule and utricle
within the semicircular canals, what do the cilia project into?
cupula
are the semicircular canals filled with endolymph or perilymph?
endolymph
what is the name for sheets of cells where hair cells are clustered within the semicircular canals?
crista
what plane does the saccule sense movement in?
verticle plane
what plane does the utricle sense movement in?
horizontal plane
what separates the hair cells within the otolith organs?
striola
compare the direction of hair cells in semicircular canals and otolith organs?
semicircular canals- all in same direction
otolith organs- oriented in all directions
what are the 3 major vestibular reflexes?
vestibulo-ocular reflex
vestibulo-colic reflex
vestibular-spinal reflex
what is the vestibulo-ocular reflex?
keeps eyes wtill in space when head moves
what is the vestibulo-colic reflex?
keeps head still in space when you walk
what is the vestibular-spinal reflex?
adjusts for posture for rapid changes in position
why does alcohol cause dizziness?
makes the cupula less dense meaning it floats in the endolymph more
-you think you are rotating when you are still
what happens to the membrane potential of a photoreceptor when light enters the eye?
hyperpolarises
why do photoreceptors hyperpolarise when light enters the eye?
Na+ channels close
what does light do to 11-cis-retinal within rods?
converts it to its active form: all-trans-retinal
why do Na+ channels within photoreceptors cose when light enters the eye?
the all-trans-retinal that is formed causes the Na+ channels to close (and then cell hyperpolarises)
during phototransduction, compare light and dark in terms of how much glutamate there is?
light- less glutamate
dark- more glutamate
what is visual acuity determined by?
photoreceptor spacing mainly
and refractive power
what is the receptive field of a ganglion cell?
the part of the retina that needs to be stimulated to elicit APs from that specific ganglion cell
are rods or cnes used for seeing in dim light?
rods
do the ganglion cells of rods have high or low convergence?
high convergence
ganglion cells of rods have high convergence, what does this mean in terms of sensitivity and acuity?
increased sensitivity
decreased acuity
do ganglion cells of cones have high or low convergence?
low convergence
ganglion cells of cones have low convergence, what does this mean in terms of sensitivity and acuity?
low sensitivity
high acuity
as you move from blue to green to red light, what happens to the wavelength and the frequency?
wavelength increases
frequency decreases
compare rods and cones in terms of chromaticity?
rods- achromatic
cones- chromatic
compare rods and cones interms of location on the retina?
rods- peripheral
cones- central
compare rods and cones in terms of light sensitivity?
rods- high light sensitivity
cones- low light sensitivity
compare rods and cones in terms of visual acuity?
rods- low visual acuity
cones- high visual acuity
lateral inhibition of neurones within the optic system aids with what?
localisation of image
what is the name for the synapse between the motor neuron and the muscle?
mtor end plate
what enzyme degrades acetylcholine?
acetylcholinesterase
what does acetylcholinesterase convert acetyl choline into?
acetate and choline
how does the curare (D-tubocuracine) poison kill you?
binds to the ACh receptor on the postysynaptic membrane and inhibits it
-no muscle contraction and so respiration stops
what are type 1 muscle fibres?
slow oxidative, resist fatigue
what are type 2a muscle fibres?
fast oxidative (aerobic)
what are type 2b muscle fibres?
fast glycolytic, easiy fatigued
what does a fasciculation usually indicate?
disease of motor neurone
