Anatomy & Physiology 1 – Exam 4 Notes
Chapter 13: The Peripheral Nervous System – Part 1:
-*KNOW THE NAME, NUMBER, AND FUNCTION OF ALL 12 CRANIAL NERVES*
Peripheral Nervous System (PNS):
- Provides links from and to world outside body
- All neural structures outside brain
- Sensory receptors
- Peripheral nerves and associated ganglia
- Efferent motor endings
From Sensation to Perception:
-Survival depends upon sensation and perception
- Sensation = the awareness of changes in the internal and external environment
- Perception = the conscious interpretation of those stimuli
Sensory Integration:
-Somatosensory system part of sensory system serving body wall and limbs
- Receives inputs from:
- Exteroceptors, proprioceptors, and interoceptors
- Input relayed toward head, but processed along way
- Levels of neural integration in sensory systems:
1. Receptor level sensory receptors
2. Circuit level processing in ascending pathways
3. Perceptual level processing in cortical sensory areas
Sensory Receptors:
-Specialized to respond to changes in environment ( stimuli)
- Activation results in graded potentials that trigger nerve impulses
- Sensation (awareness of stimulus) and perception (interpretation of meaning of stimulus)
occur in brain
,Classification of Receptors:
-Based on:
1. Type of stimulus they detect:
- Classification of Stimulus Type:
1. Mechanoreceptors – respond to touch, pressure, vibration, and stretch
2. Thermoreceptors – sensitive to changes in temperature
- Cold receptors (10-40 degrees Celsius); in superficial dermis
- Heat receptors ( 32-48 degrees Celsius); in deeper dermis
- Outside of those temperature ranges, nociceptors are activated
pain
3. Photoreceptors – respond to light energy (ex: retina)
4. Chemoreceptors – respond to chemicals (ex: smell, taste, changes in
blood chemistry)
5. Nociceptors – sensitive to pain-causing stimuli (ex: extreme heat or
cold, excessive pressure, inflammatory chemicals)
- Player in detection – vanilloid receptor
- Ion channel opened by heat, low pH, chemicals, ex:
capsaicin (red peppers)
- Respond to pinching, chemicals from damaged tissue,
capsaicin
2. Location in body
- Classification by Location:
1. Exteroceptors
- Respond to stimuli arising outside body
- Receptors in skin for touch, pressure, pain, and temperature
- Most special sense organs
2. Interoceptors (visceroceptors)
- Respond to stimuli arising in internal viscera and blood vessels
- Sensitive to chemical changes, tissue stretch, and temperature
changes
- Sometimes cause discomfort, but usually unaware of their
workings
- ex: visceral organs, blood vessels, hunger/thirst
3. Proprioceptors
- Respond to stretch in skeletal muscles, tendons, joints,
ligaments, and connective tissue coverings of bones and muscles
- Inform brain of one’s movements
- Restricted location; help make sure we don’t overstretch
3. Structural complexity
- Classification by Receptor Structure:
1. Simple receptors for general senses
- Tactile sensations (touch, pressure, stretch, vibration),
temperature, pain, and muscle sense
, - Modified dendritic endings of sensory neurons
- Either nonencapsulated (free) or encapsulated
1. Nonencapsulated (free) nerve endings:
- Abundant in epithelia and connective tissues
- Most are nonmyelinated, small-diameter, group C
fibers; distal ending have knoblike swellings
- Respond mostly to temperature and pain; some
to pressure-induced tissue movement; itch
- Ex: Nociceptors; light touch receptors
(Tactile/Merkel discs and hair follicle receptors)
2. Encapsulated Dendritic Endings
- ~All mechanoreceptors in connective tissue
capsule
- Tactile (Meissner’s) corpuscles – discriminative
touch
- Lamellar (Pacinian) corpuscles – deep pressure
and vibration
- Bulbous corpuscles (RufÏni endings) – deep
continuous pressure
- Muscle spindles – muscle stretch
- Tendon organs – stretch in tendons
- Joint kinesthetic receptors – joint position and
motion
2. Receptors for special senses
- Vision, hearing, equilibrium, smell, and taste
Cranial Nerves:
-12 pairs of nerves associated with brain
- 2 attach to forebrain; rest with brain stem
- Most mixed nerves; two pairs purely sensory
- Each numbered (I through XII) and named from rostral to caudal
I: The Olfactory Nerves:
-Sensory nerves of smell
- Run from nasal mucosa to olfactory bulbs
- Pass through cribriform plate of ethmoid bone
- Purely sensory (olfactory) function
, II: The Optic Nerves:
-Arise from the retinas; really a brain tract
- Pass through optic canals, converge, and partially cross over at optic chiasma
- Optic tracts continue to thalamus, where they synapse
- Purely sensory (visual) function
III: The Oculomotor Nerves:
-Fibers extend from ventral midbrain through superior orbital fissures to four of six extrinsic eye
muscles
- Function in raising eyelid, directing eyeball, constricting iris (parasympathetic), and controlling
lens shape
- Motor function
Chapter 13: The Peripheral Nervous System – Part 1:
-*KNOW THE NAME, NUMBER, AND FUNCTION OF ALL 12 CRANIAL NERVES*
Peripheral Nervous System (PNS):
- Provides links from and to world outside body
- All neural structures outside brain
- Sensory receptors
- Peripheral nerves and associated ganglia
- Efferent motor endings
From Sensation to Perception:
-Survival depends upon sensation and perception
- Sensation = the awareness of changes in the internal and external environment
- Perception = the conscious interpretation of those stimuli
Sensory Integration:
-Somatosensory system part of sensory system serving body wall and limbs
- Receives inputs from:
- Exteroceptors, proprioceptors, and interoceptors
- Input relayed toward head, but processed along way
- Levels of neural integration in sensory systems:
1. Receptor level sensory receptors
2. Circuit level processing in ascending pathways
3. Perceptual level processing in cortical sensory areas
Sensory Receptors:
-Specialized to respond to changes in environment ( stimuli)
- Activation results in graded potentials that trigger nerve impulses
- Sensation (awareness of stimulus) and perception (interpretation of meaning of stimulus)
occur in brain
,Classification of Receptors:
-Based on:
1. Type of stimulus they detect:
- Classification of Stimulus Type:
1. Mechanoreceptors – respond to touch, pressure, vibration, and stretch
2. Thermoreceptors – sensitive to changes in temperature
- Cold receptors (10-40 degrees Celsius); in superficial dermis
- Heat receptors ( 32-48 degrees Celsius); in deeper dermis
- Outside of those temperature ranges, nociceptors are activated
pain
3. Photoreceptors – respond to light energy (ex: retina)
4. Chemoreceptors – respond to chemicals (ex: smell, taste, changes in
blood chemistry)
5. Nociceptors – sensitive to pain-causing stimuli (ex: extreme heat or
cold, excessive pressure, inflammatory chemicals)
- Player in detection – vanilloid receptor
- Ion channel opened by heat, low pH, chemicals, ex:
capsaicin (red peppers)
- Respond to pinching, chemicals from damaged tissue,
capsaicin
2. Location in body
- Classification by Location:
1. Exteroceptors
- Respond to stimuli arising outside body
- Receptors in skin for touch, pressure, pain, and temperature
- Most special sense organs
2. Interoceptors (visceroceptors)
- Respond to stimuli arising in internal viscera and blood vessels
- Sensitive to chemical changes, tissue stretch, and temperature
changes
- Sometimes cause discomfort, but usually unaware of their
workings
- ex: visceral organs, blood vessels, hunger/thirst
3. Proprioceptors
- Respond to stretch in skeletal muscles, tendons, joints,
ligaments, and connective tissue coverings of bones and muscles
- Inform brain of one’s movements
- Restricted location; help make sure we don’t overstretch
3. Structural complexity
- Classification by Receptor Structure:
1. Simple receptors for general senses
- Tactile sensations (touch, pressure, stretch, vibration),
temperature, pain, and muscle sense
, - Modified dendritic endings of sensory neurons
- Either nonencapsulated (free) or encapsulated
1. Nonencapsulated (free) nerve endings:
- Abundant in epithelia and connective tissues
- Most are nonmyelinated, small-diameter, group C
fibers; distal ending have knoblike swellings
- Respond mostly to temperature and pain; some
to pressure-induced tissue movement; itch
- Ex: Nociceptors; light touch receptors
(Tactile/Merkel discs and hair follicle receptors)
2. Encapsulated Dendritic Endings
- ~All mechanoreceptors in connective tissue
capsule
- Tactile (Meissner’s) corpuscles – discriminative
touch
- Lamellar (Pacinian) corpuscles – deep pressure
and vibration
- Bulbous corpuscles (RufÏni endings) – deep
continuous pressure
- Muscle spindles – muscle stretch
- Tendon organs – stretch in tendons
- Joint kinesthetic receptors – joint position and
motion
2. Receptors for special senses
- Vision, hearing, equilibrium, smell, and taste
Cranial Nerves:
-12 pairs of nerves associated with brain
- 2 attach to forebrain; rest with brain stem
- Most mixed nerves; two pairs purely sensory
- Each numbered (I through XII) and named from rostral to caudal
I: The Olfactory Nerves:
-Sensory nerves of smell
- Run from nasal mucosa to olfactory bulbs
- Pass through cribriform plate of ethmoid bone
- Purely sensory (olfactory) function
, II: The Optic Nerves:
-Arise from the retinas; really a brain tract
- Pass through optic canals, converge, and partially cross over at optic chiasma
- Optic tracts continue to thalamus, where they synapse
- Purely sensory (visual) function
III: The Oculomotor Nerves:
-Fibers extend from ventral midbrain through superior orbital fissures to four of six extrinsic eye
muscles
- Function in raising eyelid, directing eyeball, constricting iris (parasympathetic), and controlling
lens shape
- Motor function
