Module 9: Body Movement

Inborn (intrinsic) reflex

rapid, involuntary, predictable motor response to a stimulus.

Learned Reflexes

Reflexes that result from practice or repetition, such as driving skills.

Somatic Reflexes

Reflexes that activate skeletal muscle and are clinically important for testing the condition of the nervous system.

Autonomic Reflexes

Reflexes that activate visceral effectors like smooth or cardiac muscle and glands.

Reflex Arc

The pathway followed by nerve impulses in a reflex action, including receptors, sensory neurons, integration centers, motor neurons, and effectors.

Proprioceptors

Sensory receptors that provide input about the length of muscles and the amount of tension in muscles.

Muscle Spindles

Modified skeletal muscle fibers that detect stretch and are involved in the stretch reflex.

Alpha Motor Neurons

Nerve cells that carry efferent impulses from the integration center to skeletal muscle fibers. Contraction of extrafusal fibers

Stretch Reflex

A reflex that maintains muscle tone in large postural muscles and causes contraction in response to muscle stretch.

Reciprocal Inhibition

A process where stimulation of motor neurons to antagonistic muscles is inhibited during a reflex.

Tendon Reflex

A polysynaptic reflex that helps prevent muscle damage due to excessive tension.

Flexor Reflex

A reflex initiated by a painful stimulus that causes an automatic withdrawal of a body part.

Crossed Extensor Reflex

A reflex that occurs with flexor reflexes in weight-bearing limbs to maintain balance by extending the opposite side.

Gamma Motor Neurons

Nerve fibers that maintain spindle sensitivity by innervating the contractile ends of muscle spindles. Cause contraction of intrafusal fibers

Integration Center

The region in the CNS where sensory impulses are processed and a response is formulated during a reflex.

Components of a reflex arc

1) receptor 2) sensory neuron 3) integration center 4) motor neuron 5) effector

sensory neuron

Transmits afferent (incoming) impulses to CNS

Monosynaptic reflux

Has a single synapse between the afferent and efferent neurons

How to relax?

Stop sending the excitatory or inhibit the motor neuron

Inhibitory interneurons

Hyperpolarize the target

Hyperactive reflex

Peripheral nerve damage or ventral horn injury

Hyperactive reflex

Potential lesions in the corticospinal tract

Golgi Tendon Organ

Sensory receptors located at the junction of muscles and tendons that detect changes in muscle tension. On/Off, cause relaxation