Neurology Flashcards
3 main functions of spinal chord?
Carry motor information from brain to spinal segment
Carry sensory information from spinal segment to brain
Integration centre for certain reflexes
Define dermatome
Area of skin supplied by a single spinal nerve root
Sensory function
Define cutaneous distribution
Area of skin supplied by a cutaneous branch of a nerve
Sensory function
Define myotome
Group of muscles supplied by a single spinal nerve root
Motor function
Name the nerve plexus divisions from proximal to distal
Roots Trunks Divisions Chords Branches
What are the main plexi?
Cervical
Brachial
Lumbar
Sacral
What are the cutaneous areas of distribution UEX?
Axillary Medial cutaneous brachii Cutaneous antibrachii medialis Musculocutaneous Radial Ulnar Median
Which dermatomes supply UEX?
C5-T2
Where do dermatomes and myotome arise from?
Somites, divisions of the body of an embryo
What myotomes innervate UEX?
C5-T1
What dermatomes innervate LEX?
L1-S4
What are the deep tendon reflexes, corresponding myotome relay and peripheral nerve?
Biceps brachii, C5, musculocutaneous Brachioradialis, C6, radial Triceps, C7, radial Finger, C8, median and ulnar Patella, L3-L4, femoral Archillies, S1, sciatic
Explain an excitory action potential?
If the membrane potential reaches a depolarisation threshold of -55mV, an excitatory action potential is generated, which will release neurotransmitters into the synaptic cleft which will depolarise the post synaptic neuron
If this depolarisation reaches threshold, the process is repeated on to the next post synaptic neuron
Explain an inhibitory action potential?
Neurotransmitters released by the pre synaptic neuron will hyperpolarise the post synaptic neuron, making depolarisation by excitory synapse more difficult, greater depolarisation must occur to reach threshold
How does a tract differ to a nerve?
Tracts are situated in CNS and do not have connective tissue coverings
Nerves are situated in PNS and have connective tissue coverings
Explain white vs grey matter?
White matter consists of myelinated nerves/tracts, primarily axons that do not contain cell bodies, they are the “pathway” to the grey matter
Grey matter consists of non myelinated nerves/tracts, they are the “control centres” and are composed of cell bodies (and short distance connecting axons), only found in CNS or just outside spinal column (dorsal root ganglion)
Explain muscle spindles?
intrafusal fibres; parallel to extrafusal (contractile) muscle fibres, contain sensory dendrites that detect size and speed of muscle length change.
Dendrites send impulse to spinal chord, which enacts a motor response to contract the stretched muscle (DTR) and relax antagonist muscle (reciprocal inhibition) to prevent over stretching
Explain golgi tendon?
Continuous with extrafusal muscle fibres, in the tendon. Responds to tension
Where are the cell bodies/grey matter of motor and sensory nerves located in the spinal chord?
Motor- deep spinal chord
Sensory- just outside each spinal segment (dorsal route ganglion)
Define a nerve?
Bundle of fibres in the PNS with its own blood supply and innervation that transmits impulses between the CNS and the effector organ
Explain the difference between stretch and glide of a nerve? (Neuro dynamic testing)
Stretch involves stretching the nerve at both proximal and distal ends
Glide involves stretching the nerve at either the proximal or distal end
Define muscle tone and relationship between deep tendon reflex?
Muscle tone is the amount of resistance a muscle has in response to an externally applied stretch
Both are a contractile protective reaction to an externally applied stretch, the DTF is more rapid in terms of stretch application and consequent contraction
What is hypo and hyper reflexia, and what may they indicate?
Hypo reflexia is lesser response to DTR, commonly associated with less muscle tone, indicates dysfunction within PNS
Hyper reflexia is a greater response to DTR, commonly associated with greater muscle tone, indicates dysfunction within CNS
Explain the process of stretch/deep tendon reflex (DTR)?
Dendrites of muscle spindles sense a lengthening/stretch, this transmits an impulse directly to spinal chord which relays a motor impulse causing the muscle to rapidly contract.
This is the only monosynaptic pathway in the human body (involving only 2 neurons)
And serves as a rapid protective response to avoid overstretching.
