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54 Cards in this Set

  • Front
  • Back
Name three functions of astrocytes
Nourish neurons
Clean synapses
Plug blood vessel leaks
Which cells make central and peripheral myelin?
Oligodendricytes - central
Schwann cells - peripheral
What proportion of cardiac output does the brain usually require?
~20%
The prosencephalon gives rise to which structures?
Cerebral cortex, thalamus, subthalamus
What is the name of the fissure that separates the parietal from temporal lobe?
Sylvian fissure
Which reflex is responsible for maintaining muscle tone? Where does it synapse?
Stretch reflex
Anterior horn of spinal cord
What is the function of the gamma-reflex loop?
To modify the stretch reflex
What are the afferent and efferent fibres of the stretch reflex?
Afferent = Ia
Efferent = alpha motor neuron
Which reflex allows withdrawal from painful stimuli? Where does it synapse?
Flexor reflex
Synapses with an excitatory interneuron in grey matter of spinal cord
Which reflex stops muscle contraction in response to an overwhelming load? What type of efferent fibre does it use?
Golgi tendon reflex
Ib fibre
What level of spinal injury may cause a stereotypical reduction in heart rate and blood pressure?
Anything above T5-6
What level of spinal injury may cause problems with micturition?
Anything above S2-4
What signs and symptoms are associated with autonomic dysreflexia?
Paroxysmal hypertension, bradycardia, throbbing headaches, profuse sweating, flushing of skin above lesion
What is the mechanism behind changes in blood pressure and heart rate in autonomic dysreflexia?
Abnormal pain/input below spinal level of injury>
Increased local SNA (but fails to ascend)>
Local vasoconstriction and increased BP>
Baroreceptor mediated increase in PSNA that fails to descend below lesion>
Reduced heart rate and failure to switch of raised blood pressure
Name six features that can be associated with a lower motor neuron lesion
Atrophy
Paralysis
Flaccidity
Areflexia
Bladder doesn't work
Fasciculations and fibrillations
Name six features of an upper motor neuron lesion
Paralysis
Hyperreflexia
Spaciticity (clasp-knife)
No atrophy
No control of bladder (reflexes only)
Pyramidal stance with flexion of elbow and extended knee
What type of fibres do meissner, merkel, pacinian and ruffini receptors use?
A-beta (type II)
What type of fibres do pain receptors use?
A-delta (type III) and C (type IV)
What types of fibres do muscle spindles use?
Types Ia, Ib and II
Where would you find the receptors for and what is the function of:
a) Meissner receptors
b) Merkel
c) Pacinian
d) Ruffini
a) Hairless (glaborous skin) - touch and pressure
b) All skin, hair, myelin - touch and pressure
c) Subcutaneous and myelin - deep vibration
d) All skin and myelin - stretch
Describe the path (with synapse, cross and cell bodies) of the spinothalamic tract
Nociceptors via DRG to synapse in DH of SC>
Crosses via anterior white commisure>
Ascends as StT (dorsolateral GM)>
then
NeoStT>VP thalamus> S1
PaleoStT> BRF > DM thalamus > cingulate cortex and insula

Cell bodies in DRG
Describe the path (with cell bodies, synapse and cross) of the dorsal column pathway
Enter via DH of SC>
Ascend as cuneate and gracile tracts>
Synapse at nucleus gracilis or cuneatus>
Cross at sensory decussation of pyramids (above motor) via internal arcuate fibres>
Ascend as medial lemniscus>
VP thalamus>
S1

Cell bodies in DRG
Describe the path (with cell bodies, synapse and cross) of the corticospinal tract
M1, parietal cortex and frontal-cingulate>
Corona radiata>
Internal capsule>
Pyramids, cross at pyramidal decussation>
Descend as CsT>
Synapse in AH of SC

Cell bodies in parietal, motor and frontal-cingulate cortex
Describe the path (with cell bodies, synapse and cross) of the spinocerebellar tract
Proprioceptor via DRG>
synapse in intermediate GM>
ascend in ventrolateral WM>
Cerebellum

Doesn't cross
Cell bodies in DRG
Describe the path (with cell bodies, synapse and cross) of the rubrospinal tract
Red nucleus (cell body)>
Cross in ventral tegmental midbrain>
synapse in AH of GM>
Somatic muscle
Describe the path (with cell bodies, synapse and cross) of the reticulospinal and vestibulospinal tracts
RetsT
BRF (cell body)>
Synapse in GM of SC>
Exit to SmM or SkM

VsT
Vestibular nucleus (cell body)>
Descends to synapse in AH of GM>
SkM

Neither cross
What is the function of the dorsal column tract?
Touch, vibration, pressure
+
Conscious (thalamic) proprioception
What is the function of the spinocerebellar tract?
Unconscious (cerebellar) proprioception
What is the function of the vestibulospinal tract?
Control of posture and autonomics
What is the function of the rubrospinal tract?
Assists the CsT with distal skilled movement
What is the function of the reticulospinal tract?
Control of posture and autonomics
How will a lesion of the corticospinal tract present?
Classical UMN presentation, contraction of anti-gravity muscles, loss of ipsilateral skilled (distal movement)
What type of receptor to preganglionic autonomic neurons act upon?
Nicotinic ACh receptor
What are the sympathetic postganglionic receptors for:
a) viscera
b) vascular SmM
c) adrenal medulla
d) sweat glands
a) NAd
b) NAd
c) Nicotinic ACh
d) Muscarinic ACh
What type of receptors are parasympathetic postganglionc receptors?
Muscarinic ACh
Describe the course of sympathetic efferent fibres (beginning with preganglionic fibres)
Sympathetic preganglionic cell bodies are in interomediolateral grey matter of SC
> ventral horn > exit via ventral root
> spinal nerve
> white ramus
> symp ganglion (ascend, descend or synapse immediately)
> postganglionic exit ganglion via grey ramus
Describe the course of parasympathetic fibres
Preganglionic nuclei (cranial nerve or S2-S4) (assume S2-S4 for rest)
> ventral horn > exit via ventral root
> terminal ganglion near effector organ
T/F Sympathetic preganglions are unmyelinated and sympathetic postganglions are myelinated
False
The reverse is true
What role does PSNA play in micturition?
Responsible for contraction of the detrusor muscle and relaxation of the internal sphincter
What effect does SNA have on the bladder?
Relaxation of the detrusor muscle and contraction of the internal sphincter
Which nerve controls the external sphincter of the bladder?
Pudendal
What are the three most common causes of neuropathic pain?
Amputation
SC trauma
Diabetes
Name three possible mechanisms of neuropathic pain
1) Ectopic activity of nociceptors following trauma due to increased Na channel expression
2) Glutamate release causing Ca influx and increased response to central transmission of pain
3) loss of descending inhibitory pain pathways
4) sprouting or rewiring of damaged nerves
What is the definition of neuropathic pain?
Pain initiated or caused by a primary lesion or dysfunction in the nervous system
What is the cause of a subdural haematoma?
Short-duration angular acceleration causing rupture of dural bridging vessels
What type of force generally causes diffuse axonal injury?
Acceleration of a longer duration (than for subdural haematoma)
e.g. car crash
What is the cause of progressive damage with brain trauma?
Trauma
>glutamate release
>calcium influx
>damage
What is the time course for diffuse axonal injury?
Starts ~2 hrs post injury, may continue for a month
T/F Subdural haematoma has a higher mortality rate than diffuse axonal injury
True
Long-term exposure to boxing-like trauma may cause which pathological inclusions in the brain?
Neurofibrillary tangles and diffuse beta-amyloid plaques
What are the two major causes of spinal cord injury?
MVA (50%) and sports (20%)
What is syringomyelia? When does it occur?
A cavity of CSF that dissects out of the central canal of the spinal cord into the white matter.

Generally post-traumatic
What are the common causes of anterior cord syndrome? What are the symptoms?
Ruptured disc or burst-fracture of vertebrae

Symptoms:
pain & temp (StT) below lesion
LMN (AH) at lesion level
+
larger lesion causes
UMN (CsT) below lesion
What are the common causes and symptoms of Brown-Sequard Syndrome?
Causes:
Penetrating injury, MS, tumour

Symptoms:
Ipsilateral motor UMN weakness (CsT)
Ipsilateral touch, vib and prop loss (DcT)
Contralateral pain and temp loss (StT)
PLUS
Sometimes band of pain and temp loss ipsilat (StT before they cross)