clinical neurology Flashcards
neurological investigation: recognise the key diagnostic technique used in neurological diagnosis, including computerised tomography (CT), magnetic resonance imaging (MRI), nerve conduction studies (NCS), electromyography (EMG), electroencephalography (EEG) and lumbar puncture (LP)
define electromyography
recording of the action potentials occurring in skeletal muscle fibres
what is extra-cellular recording
where both electrodes are placed outside the muscle fibres, and the emf (potential) between both locations is recorded; non-invasive
other examples of extra-cellular recording
ECG in heart, EEG in brain
what is intra-cellular recording
where one electrode is placed inside the cell axon, and the emf (potential) between this and an extracellular electrode is recorded; invasive
extracellular voltage difference during action potential
at rest, 0mv; when action potential generated, depolarisation (+ve as 2-1) recorded at first electrode; as passes along to second electrode, 0mv; action potential recorded at second potential, depolarisaton (-ve as 2-1)
relevant anatomy
muscle innovated by nerves; if action potential sent along sensory and motor axons, stimulus felt and muscle innovated moves; ulnar nerve; humerus
response of nerve to stimulus
depends on size of stimulus
what is measured on an EMG
gradually increasing then decreasing voluntary contraction (EMG and force)
define twitch
involuntary contraction of group of muscle fibers which then relax
define summation
continuous stimulation causing twitches frequently over short space of time before muscle has fully relaxed (build up)
define tetanus
prolonged contraction without relaxation resulting from repeating stimulation before the muscle has a chance to relax at all
