Skeletal Muscle Organ Reflex Flashcards
Exteroceptors
Surface of the body and sensitive to external environment
Pain, pressure and touch
Proprioceptors
Muscle, tendons, joints and in the inner ears and sensitive to movement
Perceives where the body is located (standing, sitting, etc.)
Sense of space
Interoceptors
Located in the viscera of the body and sensitive to changes in the internal environment
pH change, stomach cramping
Muscle spindles
In parallel to the contracting skeletal muscle fibers
Detects muscle length
Sensory organ inside muscle fibers
Golgi tendon organ
Arranged in series with the contracting skeletal muscle fibers
Detects muscle tension
Reflex through alpha motor neurons
Muscle spindle sensory innervation
Ia afferent nerve
Group II afferent nerves
Ia afferent nerve (sensory innervation)
Innervates the central region of both the nuclear bag fibers
Synapses on alpha motor of extensor
Group II afferent nerves (sensory)
Innervates the nuclear chain fibers
Muscle spindle motor innervation
Contractile end regions innervated by gamma efferent fibers that maintain spindle sensitivity
Synapse on interneurons that are inhibitory to flexors
Alpha- gamma coactivation
- Alpha motor neuron fires and gamma motor neuron fires
- Muscle contracts
- Stretch on centers of intrafusal fibers unchanged
firing rate of afferent neuron remains constant
Contraction without gamma motor neurons
- Alpha motor neuron fires
- Muscle contracts
- Less stretch on center of intrafusal fibers
- Firing rate of spindle sensory neuron decreases
Reflex arc
An involuntary response of the nervous system to a stimulus
Fixed motor response to a sensory stimulus mediated through specific neuronal linkages
What are the 5 components of a reflex arc?
- receptor
- sensory neuron
- one or more synapses in CNS
- motor neuron
- target organ, usually a muscle
Reciprocal innervation
Seen in knee jerk
Excite flexors
Inhibits extensors
Crossed- extensor reflex (part of the withdrawal reflex)
Serves postural function
Extension of contralateral limb to support animal when an extremity is flexed
Polysynaptic
Double reciprocal innervation
What does biceps reflex test?
Sensory and motor components
Musculocutaneous nerve
C6 and C7 spinal nerve
What does triceps reflex test?
Sensory and motor neurons
Radial nerve
Spinal cord segments C7, C8, T1`
Cranial Tibial Reflex
Tests integrity of SC segments L6 to S2
Sciatic and peroneal nerves
Perineal reflex
Light stimulation of perineum with forceps
Tests function of sacral SC segments and associated nerve roots
What is the response of the perineal reflex?
Contraction of anal sphincter and flexion of tail
