Reflexes

Reflex arc

The neural pathway that mediates a reflex action, involving sensory neurons, spinal cord, motor neurons, and effectors.

Reflex classification

Divided into somatic (activating skeletal muscles) and autonomic (activating visceral effectors) reflexes.

Somatic reflexes

Reflexes that are mediated by the spinal cord and do not involve direct brain activity.

Components of Reflex arc

Receptors > Afferent neuron > Integration center > Efferent neuron > Effector (muscle)

Monosynaptic reflex

A reflex arc that involves one synapse between an afferent neuron and an efferent neuron.

Polysynaptic reflex

A reflex arc that involves multiple synapses, leading to more complex responses.

Structures involved in somatic reflexes

Muscle spindles and Golgi Tendon Organ

Muscle spindles

Sensory receptors that detect the length of muscles and changes in stretch.

Golgi Tendon Organ (GTO)

A sensory receptor that senses tension on muscles and tendons, providing self-inhibitory feedback.

Stretch Reflex

A reflex initiated by the stretch of a muscle, causing a contraction in response.

Stretch reflex (steps)

•       Muscle stretched in quad

•       Spindle senses stretch, sends afferent signal to spinal cord

•       Afferent neuron synapses with motor neuron of quad and inhibitory neuron of hamstring

•       Result- quad contracts and the hamstring relaxes

Crossed-Extensor reflex

A reflex that maintains balance, ipsilateral involving withdrawal and contralateral extension of limbs.

Hypo-reflexia

Reduced or absent reflex responses often due to lower motor neuron injury.

Sensory signal cannot get to spinal cord

Hyper-reflexia

Exaggerated reflex responses due to upper motor neuron injury.

Reflex in formation cannot be modified by CNS

Afferent neuron

Neuron that transmits sensory information to the central nervous system.

Efferent neuron

Neuron that carries nerve impulses away from the central nervous system to effectors.