ANSC 3080 pt 3 reflex arcs

somatic is

reflex (skeletal muscle)

what is a reflex

involuntary, unvarying response

an automatic or unconscious response of effectors organs muscle of gland to a stimulus

what are the 5 fundamental components of a reflex arc

sensory cells/ receptors

sensory nerve fibers

coordinating center

motor nerve fibers

effectors (muscle or gland cells

somatic (skeletal muscle) reflex arcs pt 1

1. receptors

transduce the environmental energy

• skin- heat, cold, pressure

• muscle (spindle)- stretch

• tendon (Golgi)- tension

converts energy into action potentials

frequency of AP proportional to intensity of energy transduced (frequency coding)- enables CNS to detect intensity

somatic (skeletal muscle) reflex arcs pt 2

2. sensory (afferent) nerve

   • conduct AP from the receptor

   • cell body in ganglion outside of spinal cord

   • enter spinal cord via dorsal root

somatic (skeletal muscle) reflex arcs pt 3

3. coordinating center= CNS synapses

   • monosynaptic (muscle spindle reflex)

   • multisynaptic ( elaborate reflexes)

somatic (skeletal muscle) reflex arcs pt 4

4. motor (efferent) nerve

   • carries AP from CNS to target (effectors) organs

   • via ventral roots

   • cell body within CNS

somatic (skeletal muscle) reflex arcs pt 5

5. target organ response

   • skeletal muscle (knee jerk)

   • multiple targets (scratching)

stretch and tendon reflex

changes in muscle length detected by muscle spindles