BY
Lect. Dr. Zahid M. Kadhim
Receptor Physiology
 Sensory receptors are specialized structures
that detect a specific form of energy in the
external environment.
 Modality the principal types of sensation that
we can experience like pain, touch, sight, sound,
and so forth.
 adequate stimulus is the particular form of
energy to which a receptor is most sensitive
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Type of sensation
Receptor
A- Mechanoreceptors
Muscle receptors
Hearing
Equilibrium
Arterial pressure
B- Thermoreceptors
C- Nociceptors
Free nerve ending
Merkel's discs
Ruffini's endings
Hair end-organs
Pacinian corpuscles
Muscle spindles
Golgi tendon receptors
Sound receptors of cochlea
Vestibular receptors
Baroreceptors of carotid sinuses and aorta.
Cold receptors
Warm receptors
D- Electromagnetic receptors
E- Chemoreceptors
Free nerve endings
Rods Cones
Taste-Receptors of taste buds
Smell-Receptors of olfactory epithelium
Arterial oxygen-Receptors of aortic and carotid bodies
Osmolality- supraoptic nuclei
Blood CO2-Receptors in medulla and in aortic and carotid bodies
Blood glucose, amino acids, fatty acids-Receptors in hypothalamus
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receptor potential a non-propagated
depolarizing potential resembling an
excitatory postsynaptic potential (EPSP) is
recorded in the receptor
graded potentials rather than all-or-none as
is the case for an action potential.
The intensity of sensation is determined by
the amplitude of the stimulus applied to the
receptor.
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receptor adaptation
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If a stimulus of constant strength is
maintained on a sensory receptor, some
receptor types continue to respond to the
stimulus as long as its applied while others
adapt, that is mean the frequency of the
action potentials in their sensory nerve
declines over time.
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Dorsal Column-Medial Lemniscal System
Touch sensations requiring a high degree of
localization of the stimulus
Touch sensations requiring transmission of fine
gradations of intensity
Phasic sensations, such as vibratory sensations
Sensations that signal movement against the
skin
Position sensations from the joints
Pressure sensations related to fine degrees of
judgment of pressure intensity.
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Anterolateral System
Pain
Thermal sensations, including both warmth
and cold sensations
Crude touch and pressure sensations capable
only of crude localizing ability on the surface
of the body
Tickle and itch sensations
Sexual sensations
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is an unpleasant sensory and emotional
experience associated with actual or
potential tissue damage.
nociception is defined as the unconscious
activity induced by a harmful stimulus applied
to sense receptors.
Acute and chronic pain
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Hyperalgesia is an exaggerated response to a
noxious stimulus.
allodynia is a sensation of pain in response to
a normally innocuous stimulus.
Causes:1- release of chemical mediators
2- activation of nerve growth factor
3- activation of microglia in the spinal cord
Tenderness is pain or discomfort when
affected area is touched.
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Visceral pain
Perceived by receptors in the walls of the
hollow viscera and transmitted to the brain
by autonomic nerve fibers
visceral pain is diffuse, poorly localizing and
often referred to distant usually superficial
structure. it may be accompanied by nausea,
vomiting, change in vital signs and emotional
manifestations.
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Referred pain
Irritation of a visceral organ frequently
produces pain that is felt not at that site but in
a somatic structure that may be some
distance away.
Referred pain can be explained by
convergence–projection theory.
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Modulation of pain signals
gate-control theory.
Endogenous
Analgesia
system