Physiology Exam 2 - reflexes and Sensory Systems

Monosynaptic reflex

has a single synapse between the afferent and efferent neurons

polysynaptic reflex

have 2 or more synapses (interneurons). This somatic motor reflect has both synapses in the CNS

autonomic reflexes

- are polysynaptic
ex. cranial reflexes: regulation of heart rate, BP, breathing, eating, water balance, body temp, salivating, sneezing, vomiting, coughing etc.
ex. spinal reflexes: urination and defecation

stretch reflex

the contraction of a muscle in response to stretch of that muscle

Muscle stretch and there is an increase in afferent signal to spinal cord ->increased efferent output through alpha motor neurons and the muscle contracts

ex. close your eyes and your mother hands you a super heavy bag of groceries your muscle will immediately adjust to hold the weight = stretch reflex

intrafusal muscle fibers

the ends contract and are innervated by gamma motor neurons

central region has no myofibrils and is surrounded by sensory nerve endings that stimulate by stretch.

Proprioceptors

Types: muscle spindles, Golgi Tendon organs, joint receptors
these monitor limb position, movements, and exertion to give awareness of your body in space

alpha motor neurons

fancy word for the typical somatic neurons that carry APs to cause skeletal muscle to contract

extrafusal muscle fibers

typical muscle fiber

muscle spindle

a muscle receptor that lies parallel to extrafusal fibers (normal muscle fiber) and sends impulses to the central nervous system when the muscle is stretched

knee jerk reflex

utilizes a 2 neuron (sensory and motor neurons) - "monosynaptic" reflex arc.

stimulus: tap to tendon stretches muscle

Receptor: muscle spindle stretches and fires

Afferent path: AP travels through sensory neuron

Intergration center: Sensory neuron synapses in spinal cord

Efferent path 1: somatic motor neuron

effector 1: quadriceps muscle

response: quadriceps contracts

*reciprocal inhibition: efferent path 2: interneuron inhibiting somatic motor neuron to hamstring muscle, response= hamstring stays relaxed (allowing extension of leg)

flexion/ crossed extensor reflex

stimulus: pain
receptor: activate nociceptor
Afferent path: AP travels to spinal cord and diverges
a. collateral activates ascending pathway for sensation, pain, and postural adjustments to the brain
b. withdrawal reflex pulls foot away from painful stimulus
c. crossed extensor reflex supports body as weight shifts away from painful stimulus (activate extensors, inhibit flexors)