Neuromuscular Physiology Flashcards
Brain tissue is divided into
Grey matter, white matter
What is in grey matter
Dense with cell bodies
What is in white matter
Mainly connecting axons
Folds of cortex
Gyrus = ridge
Sulcus = groove
Purpose of folds in cortex
Allows for more grey matter
How many cerebral hemispheres
2
What connects 2 hemispheres
Corpus callosum
Name the 4 lobes
Frontal, temporal, parietal, occipital
What is the cerebrum the origin of
Conscious thought and intellectual function
What does cerebrum exert
Voluntary/involuntary control over some somatic motor neurones
Primary motor cortex=
Pre-central gyrus
Primary sensory cortex=
Post central gyrus
What info does gyrus get from receptors
Touch,pain,pressure,tempereature
Occipital lobe =
Visual cortex
Frontal lobe =
Gustatory cortex
Temporal lobe =
auditory and olfactory cortex
Somatic sensory association areas
Monitors activity in primary sensory cortex, allows recognition of somatic senses, special senses have their own association areas
Somatic motors association areas
Coordinates learned movement, instructions for primary motor cortex arise here
Structure of spinal cord
White matter = ascending (afferent) and descending (efferent) tracts
Grey matter = motor and sensory spinal neurone cell bodies
Sensory N enter via dorsal horn
Motor N enter via ventral horn
How many sets of spinal nerves
31
What do the spinal N contain
Motor and sensory fibres from ventral and dorsal roots
Where does cord end
Lower lumbar area, sacral and coccygeal vertebrae carry N roots (cauda equina ) from higher levels
What is myasthenia gravis
Autoimmune destruction of ACH receptors, causes muscle weakness/fatigue
How to treat myasthenia gravis
- Increase ACH conc in synaptic cleft -inhibit acetylcholinesterase
- Immunosuppression by drugs or removal of thymus
3 brain stem motor areas
Rubrospinal tract, vestibulospinal tract, reticular formation
Rubrospinal tract
Innervates mainly spinal motor neurones innervating distal limb muscles ie fine movement
Crosses midline, descends contralaterally
Vestibulospinal tract
Input from vestibulocochlear nerve
Descends and innervate ipsilateral motor neurones
Innervate proximal muscles, control balance, locomotion
Reticular formation
Extensive network in brain stem
Many connections with sensory and motor paths
Descend and innervate ipsilateral motor neurones
Inputs of cerebullum
Vestibular apparatus
Peripheral sensory receptors, especially muscle spindles and joint receptors
Visual and auditory systems
Corticospinal paths
Outputs of cerebellum
(Via thalamus)
Motor cortex, brain stem motor areas
Grey matter beneath lateral ventricles =
Basal (cerebral) nuclei
Function of cerebral nuclei
Directs many activists outside conscious control
What inhibits basal nuclei
Substantia nigra
Damage to alpha motor neurone or anterior horn =
Paralysis & wasting of muscle
Decreased muscle tone
Stretch reflex absent
Bilateral spinal cord injury (1st response)
Spinal shock, paralysis of all muscles below defect
Bilateral Spinal cord injury (second response)
Gradual increased musc tone
Exaggerated stretch reflex
Mechanism not clear
Increased sprouting of excitatory motor nerve endings and interneurones?
Upper motor lesions
Interference with vascular supply to brain - stroke
Cerebellar damage results in:
Loss of balance, unsteady gait, decreased muscle tone, reflects loss of facilitation of cortex and brain stem motor areas
Function of somatosensory system
Touch, temperature, proprioception, pain
Somatosensory 1st order neurones
Nerves with receptor endings
Cell bodies with dorsal root ganglia
Enter SC via dorsal roots
2nd order somatosensory neurones
Travel to brain via 2 primary ascending tracts
Connect to cerebral cortex - 3rd order
Spinothalamic tract
Pain and tempo receptors cross to contra lateral side via synapse
Ascend in spinothalamic tract
Synapse in thalamus
Travel to sensory cortex
Dorsal column
Proprioceptor/touch/vibration info ascend by ipsilateral dorsal column
No synapse in spine
Ascend to dorsal column nuclei
Cross midline in medulla to thalamus
Peripheral somatosensory defects
Localised symptoms
Damage to primary sensory axons
Nerve root damage, neuropathy - impaired conduction
Leads to: numbness, pins and needles, all modalities affected
Ascending tract damage
Bilateral; sensory loss in all modalities below level of lesion
Unilateral(rare): joint position sense lost on same side of lesion. Temp and pain lost on opposite side
Somatosensory damage within brain caused by and leads to
Stroke; damaging tracts from thalamus to cortex - sensory loss from opposite side of body. Motor deficits from nearby affected areas common
