3.1 week 1 Flashcards
where does the spinal cord end?
at the level of the L1-L2 vertebrae
what is the end of the spinal cord called?
conus medullaris
what extends from the conus mdullaris downward?
filum terminale, pia mater, helps anchor the spinal cord to the coccyx
which structures can be found caudally to the conus medullaris?
cauda equina, filum terminale, CSF
what is the cauda equina?
collection of spinal nerve roots that continue from the conus medullaris to L2-Co1
what are the enlargements of the spinal cord caused by?
they are caused by widening of the ventral horns, these segments innervate the upper and lower extremeties, more motor neurons to be able to control the large amount of muscles in the extremeties
the deep branch of the radial nerve penetrates a muscle, what muscle?
the spinator muscle
to what 2 large nerves does the lumbar plexus give rise to?
femoral and obturator nerves
to what nerve does the sacral plexus give rise to?
sciatic nerve
What role do voltage-gated sodium channels play in muscle contraction?
They regenerate the action potential after the endplate potential diminishes, allowing the signal to propagate across the sarcolemma.
What is the role of T-tubules in muscle fibers?
T-tubules help propagate the action potential deep into the muscle fiber, ensuring that all myofibrils contract simultaneously.
What is the relationship between calcium concentration and muscle contraction?
High calcium concentration allows tropomyosin displacement, enabling cross-bridge formation and increasing muscle force.
How does hyperreflexia indicate a CNS problem?
Hyperreflexia results from the loss of upper motor neuron inhibition, leading to exaggerated reflexes seen in CNS damage.
What are fibrillations and what do they indicate?
Fibrillations are spontaneous muscle fiber twitches seen in needle EMG, indicating denervation and a neurogenic process.
What is the Babinski reflex and what does it indicate?
The Babinski reflex is dorsiflexion of the big toe upon foot stimulation, indicating CNS injury, especially in corticospinal tract lesions.
What clinical features are typical of axonotmesis?
Loss of sensory and motor function distal to the injury, with potential for slow recovery as the axons regenerate.
How is neurapraxia different from axonotmesis?
Neurapraxia involves only myelin damage with no axonal damage, leading to quicker recovery compared to axonotmesis, which involves axon damage.
What does the presence of fasciculations in needle EMG suggest?
Fasciculations suggest disorganized firing of motor units, common in peripheral nerve or motor neuron damage, like in ALS.
What is an MEP (Motor Evoked Potential)?
MEP measures the electrical response in muscles following stimulation of the motor cortex, used to assess motor pathway integrity.
What is an SSEP (Somatosensory Evoked Potential)?
SSEP records electrical activity in the brain in response to sensory stimuli, used to assess sensory pathways.
What is a VEP (Visual Evoked Potential)?
VEP measures the brain’s electrical response to visual stimuli, commonly used to diagnose optic nerve and visual pathway disorders.
How is Botox used in clinical neurophysiology?
Botox (Botulinum toxin) is used to treat muscle overactivity and spasticity by temporarily paralyzing the muscles it is injected into.
What is electromyography (EMG)?
EMG measures electrical activity in muscles to assess their health and the nerves controlling them, used to differentiate between neurogenic and myogenic conditions.
What neurophysiological principles underlie EMG?
EMG relies on the detection of electrical potentials generated by muscle fibers during rest and contraction, which reflect the health of motor neurons and muscles.
Why is Wallerian degeneration important?
It helps clinicians understand the recovery potential of nerve injuries, as regeneration can only occur if the proximal axon and connective tissue are intact.
What is Wallerian degeneration?
Wallerian degeneration is the process of degeneration of the distal portion of an axon after it is severed, important in understanding nerve injury and regeneration.
How do we generate muscle force?
Muscle force is generated by recruiting more motor units (recruitment gradation) and increasing the frequency of motor neuron firing (frequency gradation).
What shapes a motor unit action potential?
A motor unit action potential is shaped by the size of the motor unit, the number of muscle fibers it innervates, and the conduction properties of the nerve.
What are nerve conduction studies (NCS)?
NCS measure the speed and strength of electrical signals traveling through nerves, used to assess peripheral nerve function.
What is typical for axonal pathology in nerve conduction studies?
In axonal pathology, NCS typically show reduced amplitude of the action potentials, indicating a loss of axons.
What is typical for demyelination in nerve conduction studies?
In demyelination, NCS show slowed conduction velocity and prolonged latencies, indicating disrupted myelin integrity.
How do you distinguish neurogenic from myogenic conditions in EMG?
Neurogenic conditions show high-amplitude, long-duration motor unit potentials due to motor unit enlargement, while myogenic conditions show low-amplitude, short-duration potentials due to muscle fiber loss.
What pathology can repetitive stimulation identify?
Repetitive stimulation can identify disorders of the neuromuscular junction, such as myasthenia gravis, by showing a decremental response in muscle action potentials.
What is abnormal spontaneous muscle activity in EMG?
Abnormal spontaneous muscle activity includes fibrillations, positive sharp waves, and fasciculations, which indicate denervation or nerve damage.
