The Autonomic Nervous System (ANS) is
the involuntary arm of the PNS and is also called the
Visceral Motor Division
somatic vs autonomic
Somatic
*Stimulates
*Conscious and unconscious movement
*one synapse
V.S
Autonomic
-Smooth and cardiac muscle and glands
-Stimulates or Inhibits
-Unconscious regulation
-Two synapses (preganglionic and postganglionic)
Cholinergic Neurons
Release Acetylcholine (ACh)
Adrenergic Neurons
Release Norepinephrine
The ANS manages vital process through Visceral Reflex Arcs:
Sensory signals from the viscera and skin are sent by sensory neurons to the brain or spinal cord where they are integrated by the CNS
Visceral Reflex Arcs
Divisions of the ANS
ANS Divisions:
*Sympathetic Nervous System
*Parasympathetic Nervous System
*Enteric Nervous System
Divisions of the ANS
Sympathetic Nervous System:
*"Fight or flight" division
*Prepares body for
emergency situations
Sympathetic neurons reach organs through:
1.Spinal Nerves: Sweat glands; smooth muscle of blood vessels to skeletal muscle and skin; arrector pili muscles
2.Head and Neck Nerve Plexi: Sweat glands, smooth muscle of blood vessels to skeletal muscle and skin; arrector pili muscles
3.Thoracic Nerve
Parasympathetic Nervous System:
*"Rest and digest" division
*Plays a role in the body's
maintenance functions
including digestion and
urine formation
Cranial Nerves
Oculomotor (ciliary muscles and iris)
Facial (lacrimal
glands, mucus and
salivary glands)
Glossopharyngeal (salivary
gland)
Vagus Nerve and Thoracic Nerve Plexi
Heart; Lungs; Esophagus
Abdominopelvic Nerve Plexi:
Stomach and other Viscera
Pelvic Splanchnic Nerves and Nerve Plexi
Colon; Urinary Bladder; Reproductive Organs
Sympathetic and parasympathetic
these divisions work together to maintain homeostasis
parasympathetic
This division preserves homeostasis between periods of increased physical activity
Sympathetic Tone
it dominates in the blood vessels and keeps them partially constricted
Parasympathetic Tone
dominates in the heart and keeps the heart rate at an average of 72 beats per minute
Special Senses
Special sensory neurons detect light, chemicals, and sounds present in the environment
Special Senses includes
1.Smell (olfaction)
2. Taste (gustation)
3. Vision
4. Hearing (audition)
5. Balance (vestibular sensation)
Special Senses differ from General Senses in two significant ways:
*Many special senses rely on receptors that are not neurons, but general sensory receptors are receptive ends of sensory neurons
*Special senses are confined to the head so all information travels on axons of cranial nerves while general sensory informati
the special senses
Olfaction
allows for the detection of odorants in air and the transduction of them into signals perceived as odors
Olfaction - Initiated at olfactory epithelium in the superior nasal cavity:
*Olfactory Neurons - Modified bipolar chemoreceptors that detect chemical substances perceived as odors
*Basal Cells - Stem cells that continually replace olfactory neurons which have a limited lifespan of 30-60 days
*Supporting Cells - Columnar cells tha
Olfactory Neurons send action potentials to:
*Olfactory Nerve (CN I) - Combined axons of olfactory neurons
*Olfactory Bulb - Structure that sits above cribriform plate of ethmoid bone, inferior to frontal lobe of brain
*Olfactory Tract - Composed of axons that exit olfactory bulb; travel to other re
Olfactory tract is
only sensory pathway that
bypasses thalamus
Primary Olfactory Cortex
Responsible for awareness and identification of an odor (in frontal lobe)
Which parts of the olfaction receive information from primary olfactory cortex which evokes emotional and visceral responses to odors
Amygdala, hippocampus, hypothalamus, and components of limbic system
Gustation
Gustation, or Taste, involves chemoreceptors that
are stimulated by various chemicals
Gustation also invloves
*olfactory chemoreceptors,
thermoreceptors, and nociceptors
* Taste Buds - Small clusters of receptor cells and
supporting cells scattered about tongue and other
surfaces of oral cavity
*Each taste bud is associated with a sensory neuron
that carries info
Tongue is covered with rounded projections called papillae that are classified into 4 classes
*Vallate (Circumvallate) Papillae - Largest of four classes; contain 100's of taste buds
*Fungiform Papillae - Mushroom-shaped; contain only a few taste buds
Foliate Papillae - Ridges on sides of tongue; only contain taste buds in childhood
*Filiform Papi
Taste buds located on lateral surfaces of papillae and contain three cell types:
*Gustatory (Taste) Cells - Specialized epithelial cells with microvilli that project into a small opening called a taste pore
*Basal Cells - Stem cells that continuously differentiate into new gustatory cells and have a short lifespan of 10-14 days
*Suppo
Taste Sensations rely on detection of five classes of chemicals
*Sweet Tastes - Elicited by simple sugars such as glucose and fructose
*Sour Tastes - Produced by hydrogen ions such as citric acid found in lemon juice
*Salty Tastes - Elicited by presence of metal ions such as sodium and potassium ions
*Bitter Flavors -
Taste Receptors
Substance must dissolve in
saliva to be detected as a gustatory stimulus
In taste receptors how do stimuli pass through the facial
Vagus and Glossopharyngeal cranial nerves to the medulla
oblongata, the thalamus and finally to the Primary
Gustatory Cortex (in parietal lobes)
where do taste signals travel through
they travel to the frontal lobe for integration with visual and olfactory information
and to the limbic system for emotional reactions to taste
Vision
Occurs in response to light that
stimulates the receptors (rods and cones) on the retina
where does the retina lay
within the eyeball, which also
includes a focusing lens and fluid filled chambers
Eyes are moved and protected by several
accessory structures
Accessory Structures
Protect, lubricate,
move, and generally assist the eye
Eyebrows/Eyelashes
Prevent perspiration (and light) from entering the eye
Eyelids (Palpebrae)
Protect the eye from
foreign objects and light (includes the eyelashes) and lubricate the surface
Conjunctiva
Outermost covering of the eye (mucus membrane)
Lacrimal Apparatus
Glands produce tears
Extrinsic Eye Muscles
Muscles that move
the eye
Eyeball
Hollow sphere with 3 distinct tissue layers that maintain the shape of the eyeball, focuses light as it enters eye
eyeball layers include
-Outer Fibrous Layer
-Middle Vascular Layer
-Inner Neural Laye
Fibrous Layer
Includes a white sclera that protects the inner layers and a transparent cornea that allows light to enter
Vascular Layer
Includes a dark choroid that is filled with blood vessels and prevents light from escaping
ciliary body
that controls the shape of the lens
Nervous Layer
Includes the retina
Lens
*Transparent, biconvex crystalline structure covered by an elastic transparent
capsule
*Focuses the light onto the retina
Retina
is made of an outer pigmented epithelial layer and an inner layer with photoreceptors
Cones
Photoreceptors that function in bright light for processing high-resolution color vision (~6 to 7 million)
Rods
Photoreceptors that do not detect colors but are most sensitive in low light and as component of peripheral vision (~120 million)
Macula Lutea
(center back) contains the Fovea Centralis (best vision)
Optic Disc
(blind spot) is the site of blood vessel and nerve supply to the eye
Anterior Chamber
is between the cornea and iris and the Posterior Chamber is between the iris and lens
Vitreous Chamber
is behind the lens
*Filled with Vitreous Humor (jelly-like) that holds the lens and retina in place
*Both fluids also maintain eye shape and refract light
Cataracts
A transparent lens is essential for vision so if light cannot pass through the lens, vision is impaired
what is one of the most frequent causes of blindness
A clouded lens, or cataract
Vision
1. The iris allows light through the pupil
2. The lens, cornea, and humors focus the light
onto the photoreceptors on the retina
3. The light striking the retina is converted into
action potentials by the photoreceptors
4. The action potentials are relaye
Focusing
Adjusting the convergence of light
to move the focal point
what do photoreceptors contain
pigments that change shape when struck by light
Rods contain pigment:
Rhodopsin - Composed of opsin and retinal (derived from vitamin A)
Cones contain pigment:
Iodopsins (3 different) - Composed of photopsin (3 forms�blue, red, or green) and retinal
When the image is closer than 20 feet, 3 events
must occur:
1. Accommodation - The lens must be more
convex
2. Pupil Constriction - Gives better depth of
focus (but requires more light on the image)
3. Convergence - The eye moves toward the
object (usually medially)
External Ear
-Auricle (Pinna)
-External Acoustic Meatus
-Tympanic Membrane (Eardrum)
Middle Ear
-Auditory Ossicles
-Eustachian (Auditory) Tube
Inner Ear
-Vestibule
-Semicircular Canals
-Cochlea
External Ear involves only in
hearing
Auricle
Fleshy part of the ear that collects sound
External Acoustic Meatus
Passageway lined with hairs and Ceruminous Glands (cerumen or earwax)
Tympanic Membrane
Thin membrane that vibrates when hit by sound waves and transmits the vibration to the middle ear
Middle Ear only Involves
in hearing
Auditory Ossicles
-Malleus, Incus, and Stapes
-Transmit vibrations from the tympanic membrane
to the oval window
Eustachian Tube (Auditory Tube)
*Connects the middle ear to the nasopharnyx
(throat)
*Equalizes pressure between the ear and the
outside environment
Otitis media
Inflammation of middle ear cavity
Inner Ear - Involved in hearing and balance
1. Vestibule - Involved in balance
2. Semicircular Canals - Involved in balance
3. Cochlea - Involved in hearing
The structures of the inner ear are collectively
called the
Bony Labyrinth
Inside the Bony Labyrinth are tunnels and
chambers called the
Membranous Labyrinth
The space between the bony and membranous
labyrinths is filled with
Perilymph
The space inside the membranous labyrinth is
filled with
Endolymph
what fluids move like a wave through all 3
parts of the inner ear and bend Hair Cells
hearing and balance
In the Vestibule and Semicircular Canals, this
movement determines "balance" and helps
determine body position
hearing and balance
what in the Cochlea, this movement registers as
"hearing
hearing and balance
Vestibule
-Consists of the Saccule and Utricle with specialized areas called Maculae
-Evaluates the position of the head relative to gravity
-Responds to linear acceleration and deceleration
Semicircular Canals
-The bases (Ampullae) contain specialized areas called Crista Ampullaris
-Evaluates movements of the he
In the cochlea, vibrations reach the Organ of Corti which contains specialized
Hair Cells that bend in response to the wave
Bending of the hair cells triggers an action potential, which results in
hearing
Auditory stimuli travel through the cochlear portion of vestibulocochlear nerve to the
Superior Olivary Nucleus in pons
Medial Geniculate Nucleus of
thalamus
Primary Auditory Cortex in the
temporal lobe
Connects with other regions of temporal lobe
that are involved in language, and limbic
system, which is involved in
emotions and memory