Pain + Reflexes

Visceral Pain

stimulation of visceral organ receptors, felt as vague aching, gnawing, or burning. activated by tissue stretching, ischemia, chemicals, and muscle spasms.

Referred Pain

Pain from one body region perceived from a different region; visceral and somatic pain fibers travel in the same nerves, thus the brain assumes stimulus comes from a common (somatic) region. Such as left arm pain during a heart attack

Inborn/Intrinsic reflex

rapid, involuntary, predictable motor response to stimulus

Reflex arc

receptor: site of stimulus action → sensory neuron: transmits afferent impulses to CNS (spinal cord) → integration center: monosynaptic or polysynaptic region within the spinal cord → motor neuron: conducts efferent impulses from integration center to effector organ → effector: muscle fiber or gland cell that responds to efferent impulses by contracting or secreting. Often, one muscle is activated while another is inhibited. Reflex arcs do send signals to the brain, but the reflex arc is faster, so we cant do anything about it.

Why do we have stretch/tendon reflexes?

Our CNS must receive proprioceptor input to smoothly coordinate skeletal muscle. Includes length of muscle and amount of tension in muscle.

Stretch Reflex

Causes muscle contraction in response to involuntary muscle stretch. Stretch reflexes are monosynaptic and ipsilateral.

Muscle spindle detects muscle stretch → sensory neurons synapse with motor neurons in spinal cord → motor neurons cause stretched muscle to contract AND opposite muscle to relax

Tendon Reflex

Basically the contraction reflex. Causes muscle relaxation in response to tension. Prevents damage from excessive stretching.

Golgi Tendon or Tendon Organ senses excessive tension → afferent impulses are transmitted to the spinal cord → information is simultaneously sent to the cerebellum to adjust muscle tension → contracting muscle relaxes and opposite muscle contracts