JP lectures Flashcards
What do dendrites do?
Receive info and convey signals to soma (increases cell surface area)
Which part is the metabolic part of a neuron?
Soma (perikaryon)
Where is the site of initiation of the AP?
Axon hillock & initial segment
How do glia cells affect APs?
Insulate axons to allow signals to travel further
What is saltatory conduction?
When AP ‘jumps’ from oneNode of Ranvier to the next
What is the most frequent excitatory transmitter in the CNS?
Glutamate
What are the 2 most frequent inhibitory transmitters in the CNS?
GABA & glycine
What are glutamate, GABA and glycine made of?
Amino acids
Opening of what channels allows receptor activation?
Voltage-activated Ca channels
Which 2 ions are responsible for excitatory depolarisation & flow inward?
Na & Ca
Which 2 ions ae responsible forinhibitory hyperpolarisation?
K & Cl
How do local anaesthetics work?
Na antagonist - stop N flow leading to inhibition
How do benzodiazepines work?
modulate GABA receptor so enhance Cl entry and enhance inhibitioninthepresence ofGABA
What does glutamate do?
Acts on ionotropic receptors to allow Na & Ca in and K out of cell = EPSP, depolarisationandexcitation
What does GABA do?
Acts on ionotropic receptors to allow Cl into the cell leading to inhibition
What senses does the somatosensory system mediate?
All sensations that are not the special senses
What is the receptive field of an afferent neurone?
Theregion that when stimulatedcauses aresponsein that neurone
What do pacinian corpuscles sense?
Vibration
How many sets of spinal nerves are there?
31
Which roots areresponsible for sensory function?
Dorsalroots
Which roots are responsible for motorf unction?
Ventral roots
What is grey matter?
Cell bodies andsensry afferent terminals
In which pathway do all fibres decussate together?
DCML pathway
Where i the first synapse in the DCML pathway?
The brain stem
Where do fibres decussate in DCMLpathway?
All decussate together at the level of the brain stem
if the DCML was severed will the effects be on the same side or opposite?
Same side
How does the primary afferent travel to the brain stem in the DCML pathway?
Via gracile & cuneate tracts
What is stereogenesis?
The ability to recognise and object by feeling it
Where do neurones synapse in the A
STT?
shortlyafter enteringspinalcord
Where do sensory fibres cross over in the STT?
All along the length of the spinal cord
If the STT is severed will sensation be lost on the same or opposite side?
Opposite side
How does general somatic info from the anterior head reach the brain?
Via trigeminal system
What are the 3 divisions of the trigeminal nerve?
V1 = ophthalmic
V2 = maxillary
V3 =mandibular
Where are the soma of sensory neurones of the face located?
Trigeminalsensory ganglion
Where does sensory input to T6 and above travel?
In the cuneate tract
Where does sensory info from below T6 travel?
In the gracile tract
Where is the somatosensory cortex located?
Post central gyrus of the parietal corte
What is the posterior parietal cortex responsible for?
Deciphering the deeper meaning of info in somatosensory cortex
What is the relationship between UMNs & LMNs?
UMNs supply input to LMNs to modulate their activity
What to LMNs recieve input from?
UMNs, proprioceptors & interneurons
Where are UMNs found?
The brain
How do axons of LMNs exit the spinal cord?
In the ventral roots or via cranial nerves
Which ype of skeletal muscle fibre has the largest a-MN?
Slow-oxidative (Type I) fibres
Why are Type-1 skeletal muscle fires red?
High myoglobin content
What is the myotatic reflex?
When skeletalmuscle ispulled itpullsback
What spinal levels are assessed by the knee jerk reflex?
L3-L4
What spinal level is assessed by the triceps reflex?
C7
Which spinal levels are assessed by the biceps reflex?
C5-C6
Which spinal levels are assessed by the supinator reflex?
C5-C6
Which spinal level is assessed by the gastrocenemius (ankle) reflex?
S1
Where are y-MN cell bodies located?
Ventral horn of the spinal cord
Where are golgi tendonorganslocated?
thejunctionofmuscleandtendon
What is thepurposeofgolgitendonorgans?
Protect muscle from overload
Regulate muscle tension to optimal range
Where do descending spinal tracts originate?
Cerebral cortex & brain stem
Which pathways are under control from the cerebral cortex?
Lateral pathways
Which pathways are under control from the brainstem?
Ventromedialpathways
What is the major lateral pathway?
Corticospinal (pyramidal) tract
which hemisphere controls RIGHTmusculature?
LEFT hemisphere
Where do most fibres in the corticospinal tract decussate?
The pyramidal decussation at the base of the medulla
What des the rubrospinal tract control?
Limb flexor muscles
How could lesions of the lateralcolumnspresent?
Loss of ‘fractionated’ movements
Slowing and impairmentofaccuracy of voluntary movements
Little effect on normal posture
What is the function of the vestibulospinal tract?
Helps to hold upright and balanced posture by facilitating extensor MNs of anti-gravity muscles
Where do cell bodies from the tectospinal tract reside?
Superior colliculus
What muscles does the tectospinal tract influence?
Muscles of the neck, upper trunk and shoulders
Which is more medial the medullary or pontine reticulospinal tract?
Pontine
Where do both reticulospinal tracts arise from?
Reticular formation (mesh of neurones located along the length and core of the brainstem)
Which reticulospinal tract descends bilaterally?
Medullary
What is the function of the pontine reticulospinal tract?
Helps to maintain standing posture by facilitating contraction of the extensors of the lower limbs
What is the function of the medullary reticulospinal tract?
Releases antigravity muscles from reflex control
Where are cell bodies of nociceptors located?
Dorsal root ganglia
What is the character of visceral pain?
Poorly localised, dull, aching, throbbing
Why do patient get referred pain?
A some visceral & skin afferents converge on the same spinothalamic neurones
What is viscerosomatic pain?
When inflammatory exudate from a diseased organ contacts a somatic structure
Which of the nociceptive tracts is fast & which is slow?
STT = fast SRT = slow
How do STT & SRT differ?
STT = fast = warns exact location andseverity of pain SRT = slow = registers the emotional/motivationalcomponent ofpain
What are the 3 mechanisms of actions of analgesic drugs?
Direct presynaptic inhibitions (stop Ca influx) Direct postsynaptic inhibition (reduce excitability by opening K channels) Indirect inhibition (activate inhibitory interneurones)
How do opiods work?
Couple to GPCOR to inhibit presynaptically by opening Ca chnnels and upress excitation postsynaptically by opening K channels
What are the 3 types of opioid receptor?
u
delta
Kappa
Which opioid receptor is responsible ofrmost of the analgesic actionsofopioids?
u receptor
What are the adverse effects of activating the u opioid receptr?
Respiratory depression Cnstiation Euphoria Sedation Dependence
What is the adverse effect of delta opioid receptors?
Proconvulsant
What is the difference between morphine & diamorphine?
Diamorphine ismore lipophillic
Which opioidagonist is given IV to provide analgesia in maintenance anaesthesia?
Fentanyl
Which opioid agonist is used in acute pain,particularly labour?
Pethidine
What should pethidine not beused in conjunction with? Why?
MAO inhibitors (excitement, convulsions, hyperthermia)
In which patients should tramadol be avoided?
Epilepsy
What is naloxone?
Competitive agonist of u -receptors used to reverse opioid toxicity
Which should care be taken when prescribing naloxone?
SHort half-life (opioids may have longer duration)
Why is naltrexone better than naloxone?
Much longer half-life
What should be given to a newborn displaying opioid toxicity as a result of pethidine given to the mother during labour?
Naloxone
How does paracetamol have analgesic effects?
Due toit’smetabolites
What is a adverse effect of selective COX-2 inhibitors?
They are prothrombotic
What damage can be caused by long term NSAID use
GI damage
Examples of drugs usedforneuropathicpain
Gabapentin
Pregabalin
Amitriptlline
Carbamazepine
How do gabapentin & pregabalin work?
Reduce surface area of a subunit of some voltage-gated Ca channels which are unregulated in damaged sensory neurones causing a decrease in neurotransmitters
What can gabapentin be used as prophylaxis for?
Migraines
What condition is pregabalin particularly useful in.
Painful diabetic neuropathy
How do amitriptyllinr ,nortryptilline & desipramine work?
Act centrally decreasing the reuptake ofnoradrenaline
How does carbamazepine work?
Blocks subtypes of voltage-activated Na channel that are unregulated in damaged nerve cells
What is carbamazepine first line in?
To control pain intensity & frequency of attacks in trigeminal neuralgia
