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Topics: Reflexes, Cranial nerves, Reflex Pages: 8 (853 words) Published: February 6, 2013

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Anatomy & Physiology
Lab II

Chap 22: Human Reflex Physiology
Chap 23: General Sensation

Chap 22: Reflex Physiology
Reflex Arc: mediated by neural paths (connections
of neurons) to yield rapid involuntary muscle
response to stimuli
Two main groups of reflexes:
1) Autonomic: mediated thru autonomic nervous sys
(smooth muscles in digestion, glands in sweating)
2) Somatic: involve sensory stimulation that causes
skeletal muscles to react (withdrawal reflex from



Components of Reflex Arc
1. Receptor: site of stimulus
2. Sensory neuron: transmits
afferent impulse to central
nervous system (CNS)
3. Integration center: one or
more synapses in CNS
4. Motor neuron: conducts
efferent impulse to effector
5. Effector: muscle/glands
respond to impulses

Monosynaptic & Polysynaptic Spinal Reflex
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)
Flexor reflex: utilizes sensory and motor neurons
connected by interneurons



Somatic Reflexes (cont)
Spinal reflex:
1. Stretch reflex: maintains posture/balance &
locomotion; tendon stretch causes agonist
muscle contraction and antagonistic relaxation.
e.g. Patellar (knee jerk) reflex

2. Crossed extensor reflex: flexion of one limb
followed by extension of opposite limb.
3. Superficial cord reflex: result from pain and
temperature changes. e.g. Plantar reflex

Somatic Reflexes (cont)
Cranial Nerve Reflex
1. Corneal reflex: a function of cranial nerve V
(trigeminal). Touching of the cornea causes
blinking to occur.
2. Gag reflex: a function of cranial nerves IX
(glossopharyngeal) & X (vagus). Touching of
the uvula causes gag reflex.



Autonomic Reflexes
Pupillary reflexes: reflex caused by light stimulation
of cranial nerve II (optic) causing iris constriction
by cranial nerve III (oculomotor)
1. Pupillary light reflex: pupil constricts due to
light stimulus
2. Consensual reflex: light stimulation of 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

Chap 23: General Sensation
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: react to external stimuli
Interoceptor/visceroceptor: react to internal stimuli
Proprioceptor: detects body/limb position



General Sensory Receptors
Free/naked nerve endings:
Tactile (Merkel) disc: detects light touch
Hair follicle receptor: detects light touch

Encapsulated nerve endings:

Lamellated (Pacinian) corpuscle: detects deep
pressure/high frequency vibrations

Receptor Physiology
Four qualities of cutaneous sensations: touch, heat,
cold, & pain. They are 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



Receptor Physiology (cont)
Stimulus detection terminology:
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 body
when another area is actually receiving the noxious stimulus

How to use/read a vernier caliper

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