Download Nervous System III

Nervous System III
Chapter 12
Introduction
• General senses
– Receptors widely distributed
– Skin, organs, etc.
• Special senses
– Receptors generally confined to head structures
– Eyes, ears, nose, mouth
Sensory receptors
• Specialized nervous cells that collect info from
environment
• Sends info along sensory (afferent) nerves to the
brain
Types of sensory receptors
Nociceptors
Pain via chemicals released
during tissue damage
Transferring info to the brain
• Stimulation of receptor- chemical changes
• Electrical current generated
• Can cause action potential, if stimuli is large
enough
• Peripheral nerves transmit impulses to CNS
• Analyzed and interpreted in CNS
Sensation and Perception
• Sensation- brain becomes aware of sensory
event
• Perception- brain’s interpretation of the
sensory event
• Pain vs. realization of what caused the pain
Sensory Adaptation
• Ability to ignore unimportant stimuli
• Decreased sensory impulses
• Can refocus attention
Hypokalemic sensory overstimulation
General Senses
• Receptors located all over body- skin, muscles,
joints, etc.
• Three groups
– Exteroceptive senses
• Associated with body surface (touch, pressure, temp, pain)
– Visceroceptive senses
• Associated with changes in organs (blood pressure stretch,
stomach receptors)
– Proprioceptive senses
• Associated with changes in muscles, tendons (body position,
movement)
Exterioceptors
Free nerve endings
• Common in epithelial
tissues
• Simplest receptors
• Sense itching
Tactile (Meissners) corpuscles
• Abundant in hairless portions of
skin and lips
• Detect fine touch and texture
Lamellated (Pacinian) corpuscles
• Common in deeper subcutaneous
tissues, tendons and ligaments
• Detect heavy pressure and vibrations
Free nerve
endings
Section of
skin
Epithelial
cells
Epidermis
Sensory (afferent)
nerve fiber
(a)
Epithelial
cells
Dermis
Tactile
(Meissners)
corpuscle
(touch receptor)
Sensory (afferent)
nerve fiber
(b)
Lamellated
(Pacinian)
corpuscle
(pressure receptor)
Connective tissue
cells
(c)
Sensory (afferent)
nerve fiber
Nociceptors
• Pain receptors
• Free nerve endings
• Widely distributed
(exterio and viscero)
• Stimulated by tissue
damage, chemical
release
• Brain tissue
Pain receptors
• Only visceroreceptors that produce a
sensation
• Brain doesn’t do a good job localizing
• Referred pain
Referred Pain
Liver and
gallbladder
Lung and
diaphragm
Heart
Stomach
Pancreas
Small
intestine
Ovary
(female)
Appendix
Colon
Kidney
Ureter
Urinary bladder
Liver and
gallbladder
Visceroceptors
• Receptors in internal organs
• Conveys info such as fullness, gas, pain
originating from internal organs
Proprioception
• Mechanoreceptors (stretch receptors)
• Sends info to CNS about body position and
length, tension of muscles
Stretch receptors
Sensory
(afferent)
nerve fiber
Sensory
nerve endings
Intrafusal
fiber
Skeletal muscle
fiber
Muscle spindle
Connective
tissue sheath
• http://www.youtube.com/watch?v=FKxyJfE83
1Q
• http://topdocumentaryfilms.com/the-manwho-lost-his-body/