inversion - the foot is rolled onto its lateral edge, big toe rises
they all start with the foot flat on the floor
eversion - the foot is rolled onto its medial edge, the little toe rises
dorsiflexion - the toes rise towards the shin
plantarflexion - the toes point downwards and the heel rises
the sciatic nerve splits to form the tibial and common fibular nerves which innervate 4 of the 6 muscle compartments in the lower leg and foot
the tibial branch provides motor supply to the posterior compartments of the lower limb and carries sensory information from the touch receptors on the lateral side of the lower leg and plantar surface of the foot
the sciatic nerve exits the pelvis through the greater sciatic foramen
it then runs posterior to the femur deep to the lateral hamstring (biceps femoris) to the popliteal fossa
the nerve enters the popliteal fossa on the posterior aspect of the knee joint
as it descends the posterior thigh the tibial branch innervates the hamstrings
at the most proximal aspect of the popliteal fossa the sciatic nerve divides into the common fibular and tibial nerve.
the common fibular nerve descends laterally, obliquely and superficially to wrap around the fibular head
it then divides into superficial and deep branches which innervate the lateral and anterior compartment muscles of the lower leg - ankle everters and dorsiflexors
the tibial nerve decends the popliteal fossa in the midline medial to the common fibular and enters the lower leg
it descends the midline and then courses medially to enter the ankle and foot around the medial aspect of the ankle joint
as it descends it gives off innervating branches to the posterior compartment - plantarflexors and knee flexors
Damaging the Tibial Nerve
if the tibial nerve is damaged at the popliteal fossa plantarflexion will not occur at the ankle joint because the tibial nerve provides innervation to the posterior compartment muscles where plantarflexion arises from
if the lateral compartment muscles lose their innervation eversion would not happen at the ankle joint because they are in the lateral compartment which controls eversion
if the muscles in the anterior compartment lose their innervation from the deep fibular dorsiflexion would not happen at the ankle joint because the anterior compartment muscles control dorsiflexion
all muscles of the posterior compartment plantarflex the foot at the ankle joint
Monosynaptic Stretch Reflex
the varying strength of tendon tap doesn't effect the latency as the distance between the stimuli and receptor doesn't change
the harder the tap the greater the amplitude as there is a bigger degree of stretch of the muscle spindle which increases AP firing rate which increases the number of muscle units recruited to oppose the stretch
the effect of contracting the muscle before tapping doesn't affect latency but does decrease amplitude because the muscle spindle is slack and so isn't sensitive to stimuli which decreases AP firing rate