Upper and Lower Motor Neurons Flashcards
The tendon is made out of what two things?
Epimysium
Fascia
What is a muscle spindle?
Small receptor within the muscle
Encapsulated by CT
No contractile force
Mechanoreceptors activated when middle of spindle is stretched
Does more or less firing occur when
- Muscle is lengthened/stretched
- Muscle is shortened
- More firing
2. Less firing
Extrafusal muscle fibers
Skeletal muscle fibers that are innervated by alpha motor neurons
Intrafusal muscle fibers
Innervated by gamma motor neurons
Allows you to further stretch or reduce stretch
Muscle fibers involved in the muscle spindle
Length information is carried by the muscle spindle and type __ afferents
2
1a afferents are coded by…
Firing rate
Carry info about length and rate of change
Ultrastructure of myofibrils
A bands: anisotropic (dark) = myosin
I bands: isotropic (light) = actin
Z discs: filamentous proteins attaching to actin and connecting adjacent myofibrils
What is a motor unit?
One anterior horn cell that branches and innervates a bunch of muscle fibers
The motor neuron and all the muscle fibers it innervates
Are all the fibers of a motor unit the same or different?
All are the same type
Ex: all fast or slow twitch, type 1 or 2
In the neuromuscular junction, where is there a
- Ligand-gated channel
- Voltage-gated channel
- The nicotinic AChR (binding allows Na and K efflux, which changes the membrane potential to get an EPP)
- In the T tubules (a voltage-gated Na channel on the sarcolemma - opening causes an AP)
Spinal shock
Damage to upper motor neurons will cause hyper reflexia
Doesn’t develop immediately (days to weeks)
Babinski sign will be immediate though
2 signs of an upper motor neuron lesion
Increased tone/spasticity
Hyperreflexia
4 signs of a lower motor neuron lesion
Decreased tone
Hyporeflexia
Atrophy
Fasciculations
