PSL300

• Many reflexes disappear with age
• somatic reflexes involve skeletal muscles
• the stretch reflex is subconcious
• the stimulus for a stretch reflex is passive stretch of a muscle or contraction of an antagonist muscle
• the response of a strech reflex is active contraction of muscle
• stretch reflex is very sensitive and fast because it is monosynaptic (sensory afferent directly synapses with motor neuron)
• stretch reflex is a spinal reflex
• during movement the stretch reflex is suppressed
• Golgi tendon reflex will relax the muscle after it is contracted
• golgi tendon reflex is polysynaptic because it passes the interneurons
• the stimuli for golgi tendon reflex is the contraction in the muscle
• the response of the golgi tendon reflex is the relaxation of the muscle
• the golgi tendon reflex is inhibitory and is the opposite of the stretch reflex
• golgi tendon reflex activates the inhibitory interneurons that inhibit the motoneurons
• flexion withdrawal reflex is the conscious reflex, the touch the hot stove reflex
• the stimuli for the flexion withdrawal reflex is pain
• response of the flexion withdrawal reflex is flexion of joints proximal to stimulus
• flexion withdrawal reflex is slow because it goes through multiple interneurals
• the response of flexion withdrawal reflex is the extension of joints distal from stimulus
• reciprocal inhibition is where the activation of one motor nucleus happens simultaneously as the inhibition of antagonistic motor nucleus
• when co-contraction of antagonists is needed, the reciprocal inhibition is suppressed
• patellar tendon reflex is where a stimuli to the patellar tendon (knee) causes quads to stretch then contract via the stretch reflex
• patellar tendon reflex simultaneously inhibits hamstring contraction via reciprocal inhibition
• cross extension reflex: contraction of leg via flexion withdrawal reflex is coupled with extension of the other leg
• stimuli for the extensor thrust reflex is pressure on the sole of the foot
• Babinski sign test can be conducted to look for damage in the corticospinal tract
• If there is damage to the corticospinal tract, the flexion withdrawal reflex is activated and toes will curl up in response to stroking of the sole
• Vestibulospinal reflex is stimulated by head movement sensed by otolith afferents (ear stones)
• limbs on the same side as the downward tilt will extend due to the vestibulospinal reflex
• most reflexes maintain posture and balance, but flexion withdrawal reflex avoids pain
• central pattern generators allow rhythmic patterns and coordinate multiple motor groups
• each leg has a swing phase of flexion in the air and a stance phase of extension on the ground
• each leg has 2 CPGs, one per phase
• flexor burst generator and extensor burst generator reciprocally inhibit each other
• The flexion or swing phase has a fixed duration
• the next swing phase if the leg is not supporting weight, the hip is extended, and the opposite leg is supporting leg
• arm swings: when one leg is flexed, the contralateral arm is also flexed
• the leg CPGs and the arm CPGs are connected by propriospinal tracts
• the upper body needs to be balanced with CPGs in the reticular formation
• spinal injuries can disable walking because the leg CPGs cannot be initiated, but the CPGs themselves are not damaged just the brain-spinal connection