Physiology Flashcards
What is neuropathic pain?
Nerve damage causing pain
What is spontaneous pain?
Pain in the absence of a stimulus
Two Major types of pain fibres and their properties?
A fibres - Fast, myelinated
C Fibres - Slow unmyelinated
What type of pain are C fibres involved in transmitting?
Aching, burning pain
What type of pain are A fibres involved in transmitting? the four types of fibre?
A alpha fibres - muscle pain
A beta fibres - mechanical
A gamma fibres - muscle and pressure
A delta - sharp pain
What do substance P and CGRP do at peripheral synapses?
Lead to flare and oedema
The two types of ascending pathways that transmit pain in the peripheries, their properties?
Spinothalamic (neospinothalamic)
- Direct
- immediate, exact location
Spinoreticulothalamic (Paleospinothalamic)
- Indirect
- Involve limbic structures (amygdala included)
- Emotional and visceral pain
- descending suppression of pain
What fibres are involved in descending suppression of pain? What do they release?
C Fibres release glutamate and substance P
How do glial cells respond to painful stimuli?
What can this lead to?
They release mediators to sensitise the post-synaptic receptor e.g.
IL 1 and 2 TNF NO Prostaglandins Glutamate ATP
This can lead to central sensitisation
Two types of sensitisation?
Central
Peripheral
What mostly leads to central sensitisation?
Repetitive input
What does repetitive input produce?
Wind-up
What is wind up?
Increased electrical activity that results in increased excitability of second order neurones in the spinal cord
What two things can central sensitisation cause?
Define them
Allodynia - Pain from a stimulus that is not usually painful
Hyperalgesia - increased sensitivity to painful stimuli
What are the three main mechanisms of central sensitisation?
Increase of membrane excitability
Synaptic facilitation
Disinhibition (less inhibitory neurotransmitters)
Where does central modulation occur?
The dorsal horn
One main example of how central modulation works?
The gate theory
What is the gate theory?
the theory that descending pathways inhibit pain fibres
A beta fibres inhibit pain fibres in the dorsal horn
Two main types of synapses in the CNS?
Electrical and chemical
What type of synapses are gap junctions?
Electrical
What type of synapses involve the SNARE complex?
Chemical
What is the SNARE complex?
A complex in the pre-synaptic cell that changes in the presence of high intracellular calcium.
In the presence of high calcium the SNARE complex allows a pore to be formed between the vesicles and the cell membrane which allows neurotransmittors to be released.
Three types of chemical synapse?
Axo-dendritic
Axo-somatic
Axo-axonic
What is the one type of chemical synapse that is excitatory as well as inhibitory, also the most common by far?
Axo-dendritic
What is the speed of ionotropic receptors compared to metabotropic receptors?
Ionotropic - Fast
Metabotropic - Slow
Two main ways neuronal transmission is modulated?
G-protein coupled receptors (through second messengers)
Co-transmitters - excitatory and inhibitory (neuropeptides)
How do neuropeptides (co-transmitters) modulate neuronal activity?
Through their action on G-protein coupled receptors
They are only released in high Ca concentration
An example of a neuropeptide involved in pain? what does it do?
Substance P, increases pain transmission
What does enkephalin do?
Reduces pain through reduction of substance P and Glutamate
As each synapse releases on average 1 vesicle each (there are 10,000+) What are the two types of synaptic integration (summation)?
Temporal - summation at the same synapse
Spatial - from several different synapses
What is the loss of both temporal fields of the eye called?
Bitemporal hemianopsia
What area is damaged to cause bitemporal hemianopsia, example of what can cause this damage?
Optic chiasm
Pituitary tumour
Where would damage have occured to cause loss of vision in one eye? examples?
optic nerve
MS
Glioma
Head trauma
What artery would be damage to give one eye full vision loss
Anterior cerebral artery
Haemorrhage of what artery would cause bitemporal hemianopsia?
Anterior cerebral artery (anterior communicating artery)
What would loss of vision to the left temporal visual field and the right nasal field be called?
Left homonymous hemianopsia
Where would damage have occurred to cause left homonymous hemianopsia? Causes?
Optic tract (right side) OR optic radiations
Tumour
What artery would be damaged to cause left homonymous hemianopsia?
Posterior Cerebral Artery
What is left superior quadrantopsia? Causes?
Both superior left quadrants damaged
Temporal lobe tumour
Where is damaged to cause left superior quadrantopsia?
Meyers loop (the lower radiations)
What artery would be damaged to cause left superior quadrantopsia?
PCA
What are the two pathways from V1 (primary visual area)?
What do they do?
The dorsal (parietal pathway) = movement
The ventral (temporal pathway) = colour and form
4 main conditions that give rise to acute neuro-dengeneration?
Traumatic brain injury
Stroke
TIA
Intracranial haemorrhage
Two types of stroke, which is more common?
Ischaemic (85%)
Haemorrhagic
Causes of an ischaemic stroke?
Occlusion e.g. atherosclerotic arteries
Emboli
Three main molecular mechanisms that lead to ischaemic neuro-degeneration?
Increased [Ca2+]
Increased Glutamate
Increased free radical levels
What’s ischaemic depolarisation?
Large amounts of ATP are usually required to maintain resting potential (Na+/K+ pump)
In ischaemia there is no available ATP and depolarisation followed by normalisation of that resting potential occurs
What free radicals are produced in ischaemic neuro-degeneration and where?
Superoxide formed in mitochondria (O2-)
NO formed from arginine
Bind together to form ONOO-
How does raised calcium cause cell death in acute neuro-degeration?
Increased Free radical production
Oedema
activates proteases
Two classified areas of the affected cerebrum in stroke?
The necrotic core
The penumbra
Two types of cell death in the ischaemic penumbra?
Necrotic
Apoptotic
Treatment for AF?
Warfarin
Main types of stroke syndromes?
TACS - total anterior circulation syndrome
PACS - partial anterior circulation syndrome
Posterior circulation syndrome (basilar/vertebral/posterior cerebral)
Lacunar anterior circulation syndrome
Two main arteries supplying the basal ganglia?
Recurrent medial striate artery
Anterior choroidal artery
What’s a watershed infarct?
Infarct in the periphery of two arterial territories
Types of haemorrhagic strokes?
Supratentorial
Cerebellar
Pontine
Subarachnoid haemorrhage
Main symptom that distinguishes a haemorrhage from a stroke?
Sudden onset severe headache, followed by neurological signs
Symptoms of total anterior circulation syndrome?
deterioration of conscious level
Contralateral homonymous hemiplegia
Contralateral hemisensory deficits
Symptoms of partial anterior circulation syndrome, of the anterior cerebral artery?
Contralateral hemiparesis (leg more)
Mild/non existent sensory deficit
Apathy/disinhibition
Symptoms of partial anterior circulation syndrome, of the middle cerebral artery?
Contralateral hemiplegia (arm more)
sensory deficit
hemianopia
aphasia/neglect
Symptoms of posterior circulation syndrome, of the posterior cerebral artery?
Hemianopia
amnesia
occulomotor/language disturbances
Symptoms of posterior circulation syndrome, of the vertebral artery?
(only supplies the posterior inferior cerebellar artery)
Laterally medullary syndrome
- ipsilateral limb ataxia
- ipsilateral horners
- contralateral sensory loss to limbs
Two types of basilar artery syndromes?
Complete basilar artery syndrome? (most of pons and medulla);
- Impairment of conscious level
- bilateral motor + sensory dysfunction
- cranial nerve signs
‘Top of the basilar’ syndrome (midbrain/thalamic/temporal/occipital):
- hemianopia/cortical blindness
- amnesia
- vertical gaze palsies
One perhaps promising stroke treatment?
IL-1 receptor antagonists
main functions of complement?
Lysis
Opsonization
What’s the choroid plexus?
Barrier between blood and CSF
Secretes CSF
Two categories of descending motor pathways?
Lateral
ventromedial
Two tracts in the lateral descending motor pathways?
Rubrospinal
Corticospinal
Where do fibres from the corticospinal tract arise?
The Primary motor cortex
The association motor cortex
Somatosensory areas
lesions to both lateral tracts often cause what?
What does it not cause a deficit in?
Loss of fine motor control
slower and less accurate movement
Can still stand upright however
A lesion to only the corticospinal tract cause what?
Intially the same deficits as a lesion to both of the tract in the lateral pathway
However the rubrospinal tract has plascticity and will take over some of the corticospinal tracts roles, apart from fine motor control.
What are the 3 ventromedial pathways?
Vestibulospinal tract
Tectospinal tract
Reticulospinal tract
What is the flexion crossed extension reflex?
When a cutaneous afferent causes contraction of a flexor and relaxation of an extensor, in reaction to noiceceptive input.
What are central pattern generators?
Examples?
Circuits that are hardwired into the CNS that do not need to be learned.
Key components of locomotion
respiration
mastication
Swallowing
Stages of the motor loop, involved in generating a voluntary muscle movement in the brain?
Feeds in from sensory cortex and prefrontal cortex will then relay to the VLN (through pons/cerebellum and basal ganglia) which will relay back to the Primary motor cortex, programme is stored in association motor cortex, which will fire if the depolarisation is above threshold
Three areas of the cerebellum, their roles?
Spinocerebellum - muscle tone/coordination
Cerebrocerebellum - planning, storing of procedural memory
Vestibulocerebellum - balance, eye movement coordination
What is the cerebellar motor loop?
When the cerebellum projects directly to the VLN, allowing direct movement
3 different structures of synapses?
One to one
Many to one
One to many
Mechanisms of plasticity in the CNS?
Presynaptic: increase or decrease transmitter release
Postsynaptic: increase or decrease in signal transduction
Recruiting silent synapses
In simple animals how does habituation and sensitisation occur?
Both caused by the response of the post-synaptic cell
Habituation is caused by the desensitisation of the Voltage Dependent Calcium Channel (VDCC)
Sensitisation is caused by increased calcium influx
In mammals what is long term potentiation? How does it occur?
Synapses that fire more (higher frequency) will be strengthened
Mostly through activated NMDA receptors that activate CAM kinase, which do several things to strengthen a synapse:
Phosphorylate AMPA receptors
Recruit more AMPA receptors
Cause increased neurotransmitter release
In mammals what is long term depression? How does it occur?
Synapses with low frequency signals will weaken
Pre-synaptically: Decreased glutamate release due to decreased VDCC
Post-synaptically: Dephosphorylation of AMPA receptors
How do dendritic cells present viral peptides to T-lymphocytes if they are not infected?
Can activate MHC class I to present a viral peptide
How do T-cells return to the place that the APC cell was activated?
Through up-regulation of specific adhesion molecules
Difference in Th1 and Th2 cells?
Both will stimulate the production of B-cells
Th1 is mostly involved in fighting parasites (eosinophils/basophils)
Th2 cells are mostly involved in fighting bacteria/viruses (macrophages)
What do Tc cells use to perforate cells, two types?
Use cytotoxic proteins:
- Perforin
- Granzymes (A and B)
How do perforin and granzymes interact to produce cell death?
Perforin makes pores in the cell surface membrane and granzymes will activate apoptosis in the cell, moving through pores made by perforin.
What’s myelitis?
Infection of the spinal cord
The ability to recover from a spinal cord injury is determined by what factors?
Age
Characteristics of the lesion
Effect of experience
Training
Two categories of brain tumours? examples?
Intrinsic: glioma
Extrinsic: meningioma
Four types of haematoma?
Extra-dural
Acute sub-dural
Intracerebral
Intraventricular
Two different appearances of a scan of a subdural and an extradural haematoma?
Acute subdural - crescent (long and thing)
Extra dural - fatter look like a lemon
Four types of brain herniation?
Subfalcine
Tentorial (uncal)
Tentorial (central)
Tonsilar
What pathway promotes sleep?
VLPO (GABA) pathway
What neurotransmitters promote wakefulness?
NA, Histamine, Dopamine, Ach, glutamate
Hypnotic medications?
Benzodiazepines
Melatonin receptor agonists
Histamine receptor antagonists
Antidepressants
Stages of swallowing?
Buccal - voluntary
Pharyngeal
Eosophageal
What is degulation?
Swallowing
