Lesson 11: Ch. 21 Human Reflex Physiology & Ch. 22 General Sensations

reflex arc

mediated by neural paths (connections of neurons) to yield rapid involuntary muscle response to stimuli

Two main groups of reflexes

1.Autonomic

2.Somatic

autonomic reflexes

mediated through autonomic nervous system (smooth muscles in digestion, glands in sweating)

somatic reflexes

involve sensory stimulation that causes skeletal muscles to react (withdrawal reflex from pain)

components of reflex arc

1.receptor

2.sensory neuron

3.integration center

4.motor neuron

5.effector

components of reflex arc: receptor

site of stimulus

components of reflex arc: sensory neuron

transmits afferent impulse to central nervous system (CNS)

components of reflex arc: integration center

one or more synapses in CNS

components of reflex arc: motor neuron

conducts efferent impulse to effector

components of reflex arc: effector

muscle/glands respond to impulses

spinal reflexes

initiated & completed at spinal cord level without involvement of higher brain centers (remember these are somatic reflexes!!!)

knee-jerk reflex

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

flexor reflex

utilized sensory and motor neurons connected by interneurons - “polysynaptic” reflex arc

spinal reflex

1.stretch reflex

2.crossed extensor reflex

3.superficial cord reflex

stretch reflex

maintains posture/balance & locomotion; tendon stretch causes agonist muscle contraction and antagonistic relaxation e.g. Patellar (knee jerk) reflex

crossed extensor reflex

flexion of one limb followed by extension of opposite limb

superficial cord reflex

result from pain and temperature changes e.g. plantar reflex- Babinski’s sign (abnormal response is flared toes)

corneal reflex

a function of cranial nerve V (trigeminal). Touching of the cornea causes blinking to occur

gag reflex

a function of cranial nerves IX (glossopharyngeal) & X (vagus). touching of the uvula causes gag relfex

pupillary reflexes

reflex caused by light stimulation of cranial nerve II (optic) causing iris constriction by cranial nerve III (oculomotor)

pupillary reflexex are

1.pupillary light reflex

2.consensual reflex

pupillary light reflex

pupil constricts due to light stimulus

consensual reflex

light stimulation on one eye causes pupil constriction in contralateral (opposite side) eye

ciliospinal reflex

stimulation of back of neck causes ipsilateral (same side) pupil dilation

salivary reflex

food odor detection causes salivation

general senses

general sensory receptors respond to touch, pressure, pain, heat, cold, stretch, vibration, & body position. found throughout body

special senses

localized in groups; receptors for sight, hearing, equilibrium, smell, & taste

types of receptors that can detect stimuli

exteroceptors

interoceptor/visceroceptor

proprioceptor

exteroceptors

react to external stimuli

interoceptor/visceroceptor

react to internal stimuli

proprioceptor

detects body/limb position

free/naked nerve endings

hair follicle receptor (non-encapsulated)

free nerve endings

hair follicle receptor (non-encapsulated)

detects light touch

free nerve endings

detects pain, temperature

encapsulated nerve endings

tactile (meissner’s) corpuscle

bulbous (ruffini’s) corpuscle

lamellar (pacinian) corpuscle

tactile (meissner’s) corpuscle

detects light touch, light pressure

bulbous (ruffini’s) corpuscle

detects deep pressure/stretching

lamellar (pacinian) corpuscle

detects deep pressure/high frequency vibrations

four qualities of cutaneous sensations

touch, heat, cold, & pain

non-uniformly distributed throughout the body (hands have more touch receptors than arm, etc.)

distribution based on the importance of the area and the need for those receptors

stimulus detection terminology

two-point threshold

tactile localization

adaptation

referred pain

two-point threshold

smallest distance 2 points of contact can be perceived (use a vernier caliper for this activity)

tactile localization

determining which point on skin has been stimulated

adaptation

sensory receptor discharge from stimulus slows causing the perception of stimulus to decrease

referred pain

perception of pain from one area of the body when another area is actually receiving the noxious stimulus