Review Sheet -- Exam 4                 Bio 2212                     Dr. Adams

AUTONOMIC NERVOUS SYSTEM
(purely motor); also called involuntary/visceral NS

Comparisons:                 Somatic                 vs.                 Autonomic
Effectors:                   Skeletal Muscle                     Cardiac/smooth Muscle, Glands

Efferent Pathways:     1 neuron from CNS             2 neurons (pre-/postganglionic) from CNS 
                                        to effector                            to effector, with synapse in ganglia

NT's/NT effects:      ACh; always excitatory        Ach or norepinephrine; receptor-dependent 

Somatic and Autonomic divs. consistently work together -- e.g., when voluntarily exercising 
skeletal muscle, the autonomic division is involved in increasing heart/respiratory rates and 
controlling distribution of blood flow, as well as regulating sweat gland function.

Divisions of the ANS: Parasympathetic/Sympathetic
    Most organs fed by one ANS division fed by other as well -- dual innervation. Typically, 
        effects of the two divisions are antagonistic

Comparisons:                 Parasympathetic                 vs.                 Sympathetic

General Function:          Relaxation, Digestion                                "Fight or flight"

Origin Sites in CNS:             Craniosacral                                         Thoracolumbar

Lengths of fibers --
        Preganglionic:                     Long                                                     Short
        Postganglionic:                   Short                                                      Long

Location of Ganglia:     At or in effectors (terminal)                 Near CNS (para-/prevertebral)

NT=s released --
        Preganglionic:                 Acetylcholine                                         Acetylcholine
        Postganglionic:                Acetylcholine                                 Norepinephrine (mostly)

Parasympathetic Division: the Craniosacral division
    Cranial outflow involves cranial nerves 3, 7, 9, and 10 (10 is the "biggie": the vagus nerve)
            Know
effects on: iris (pupil), lens (ciliary body), lacrimal glands, salivary glands (3/7/9)
        Vagus nerves: 90% of parasympathetic preganglionic neurons in this pair of nerves
            Innervate: heart, lungs/bronchi (in thoracic cavity), liver, gallbladder, stomach, small &
                        proximal half of large intestine, pancreas, kidney (in abdominal cavity)
                In general, slows activity of organs in thoracic/increases activity in abdominal cavities
    Sacral outflow: Spinal nerves (S2-S4) serve lower pelvic organs (through splanchnic nerves). 
                Innervate: distal half of colon, urinary bladder/ureters, reproductive organs


Sympathetic Division
: the thoracolumbar division (T1-L2)
    Decidedly more complex than parasympathetic, because it innervates more organs, e.g. 
        sweat glands, blood vessels walls (smooth muscle), arrector pili muscles
    Lateral horns
of the gray matter are found from T1-L2 because of the numerous 
             sympathetic preganglionic neurons arising from this region.  
    Preganglionic axons enter spinal nerves through ventral roots, then pass through white 
            rami communicantes
(singular: ramus communicans) to the anteriorly located
            paravertebral, or sympathetic chain, ganglia. One set of these ganglia are located 
            on either side of the vertebral column, extending from coccygeal to cervical regions.

Possible sympathetic pathways (see Figure 14.5, pg. 530):
    1.  Preganglionic synapses at same level in paravertebral ganglion and postganglionic neuron
            reenters spinal nerve though gray ramus communicans.
    2.  Preganglionic ascends or descends chain to synapse in a ganglion at a different level; 
            necessary for getting sympathetic stimulation into head region, and explains why cervical 
            nerves have only gray rami communicantes.
    3.  Preganglionic passes through chain ganglia to the prevertebral ganglia (mostly located in 
            a network [plexus] on the surface of the aorta). This is typical for sympathetic stimulation 
            of the abdominal organs, and these neurons form part of the splanchnic nerves.
    4.  There are a few preganglionic that synapse directly with the adrenal medulla, stimulating 
           it to release norepinephrine and epinephrine.
Know basic effects of sympathetic division on organs innervated, and reticular formation.

Physiology of the ANS
    Cholinergic vs. adrenergic receptors; understand the importance of beta blockers

Interactions of the ANS divisions: as discussed previously, interactions of the two parts is 
    typically antagonistic, though in many cases, one division or the other predominates in its 
    effects. At rest, many organs exhibit parasympathetic (mostly vagal) tone, with sympathetic 
    effects only occurring in periods of stress. Vessels do, however, exhibit sympathetic  
    (vasomotor) tone, even during rest. Cooperative affects do occur: parasympathetic division
    is responsible for arousal phase (blood flow into erectile tissue), and sympathetic the climactic
    phase (orgasm; contraction of muscles, including ejaculation) of sexual interaction.

Unique roles of sympathetic division: thermoregulation and numerous metabolic effects

Localization and duration of effects:
    Further comparisons:   Parasympathetic             vs.              Sympathetic

Effects typically:              localized and brief                   diffuse (widespread) and longer . . .

                                                                     BECAUSE:
Ganglionic synapses:                  Few                             Many, potentially at many levels

Postganlionic axons:      branch sparsely at targets           branch profusely at targets

NT=s:                          ACh destroyed immediately         Norepinephrine taken back up by
                                     by acetylcholinesterase               postganglionic neuron (takes longer)

Hormones:                            not involved                 Norep. and epin. involved (from adrenal
                                                                            medulla; must be cleared from bloodstream)

    Control of Autonomic Functioning:
        Hypothalamus, through control centers in brain stem (particularly medulla) & spinal cord
                Emotions play a major role in regular and unusual activity of the ANS
        Reticular formation is an important part of the brain stem controls; conciousness important
                for awareness of autonomic events, and can influence autonomic events.
        Higher Brain Centers (cerebral cortex) can influence ANS function, and people can have 
                some conscious control over the ANS through biofeedback.

SPECIAL SENSES
-- five (touch not included); taste, olfaction, vision, hearing, balance

I. & II.  Chemical senses: Taste and Olfaction; respond to chemicals dissolved in water
  I. Taste: organ of taste -- taste buds on papillae (fungiform and circumvallate); also filiform 
        papillae without taste buds (all papillae help grip food). Taste buds also found sparingly 
        other places, including epiglottis (for reflexive closing of larynx). Taste has homeostatic 
        importance -- allows detection of needed/poisonous substances.
    Taste bud structure: epithelial cells; know structure/function of supporting, gustatory, and 
            basal cells. Turnover 10-14 days. Wrapped around base of taste buds are sensory
            dendrites of "taste" neurons (cranial nerves VII [facial] and IX [glossopharyngeal])
        Taste sensations: salty, sweet, sour, bitter and umami ("beefy"); some more sensitive 
            than others; many respond to more than one quality. Taste is 80% smell, and may
            involve mechanoreceptors (texture), thermoreceptors (temp.), and even nociceptors.
      Physiology of taste: gustatory cells do contain synaptic vesicles which ultimately stimulate 
            neurons; bitter receptors have lowest threshold for activation. Receptors adapt rapidly.
      Taste pathway to the brain:  gustatory cortex in insula; involves multiple inputs, as indicated
            above, including overlap from sense of olfaction.

  II. Olfaction: organ of olfaction -- olfactory mucosa with olfactory receptors (unique,ciliated, 
            bipolar neurons, with regenerative capabilities); neurons of cranial nerve I. Actually, 
            several separate bundles passing through cribiform plate of ethmoid, synapsing with 
            mitral
cells in olfactory bulb. Turnover of  receptors every 60 days.
        Olfactory sensations: some 1000 genes seem to be involved with olfaction; receptors 
            extremely sensitive to volatile substances dissolved in mucus. As with taste, smell may 
            involve nociceptors
        Olfactory pathways: through olfactory bulb and tract to several areas of brain (remember 
                connections to limbic system), ultimately to underside of frontal lobes, and to insula for
                interactions with taste. Adaptation in olfactory bulbs (mitral cells), not the receptors
                themselves. Mitral cells can integrate a bit, refining signal before relaying it.

III. Vision -- the Eye
        Accessory structures: eyebrows; eyelids (palpebrae), including fissure, canthi, caruncle 
                with lacrimal puncta, tarsal plates with attached levator palpebrae superioris muscle,
                tarsal glands, eyelashes; conjunctiva (ocular and palpebral, conjunctival sac); lacrimal
                apparatus (lacrimal gland, canals, puncta, sac).
            Tears with lysozyme
            Extrinsic eye muscle movements: saccades and scanning movements
    Structure of the Eyeball -- tunics:
            1. Fibrous: sclera and cornea; know general structure of both
            2. Vascular (uvea) -- choroid, ciliary body (with suspensory ligaments), iris (pupil)
                     know general structure and function of each part
            3. Sensory (retina) -- pigmented and neural layer
                   neural layer: photoreceptors (rods and cones), bipolar cell layer, ganglion cell layer
         Ganglion cell axons form cranial nerve II (optic), which leaves eye at optic disc (blind
                spot), wrapped by extension of sclera (epineurium/dura mater) to brain
         Know general functions/distributions of photoreceptors -- rods and cones
                Macula lutea, fovea centralis
      Chambers and fluids: posterior segment with vitreous humor, anterior segment with 
            aqueous humor.  Aqueous humor continuously recycled -- produced by ciliary body, 
            drained by scleral venous sinus (canal of Schlemm)
        Lens -- biconvex, flexible; changes shape when ciliary body contracts/relaxes
                Along with cornea, responsible for refraction of light waves
                Lens fibers, crystallins. Lens enlarges throughout life (decreases elasticity)
   Physiology of Vision: Understand wavelength, color, reflection, refraction
      Focusing:
            Focal points; image inverted on retina
                Focusing of light on retina: involves refraction by cornea and lens:
                    Distance -- far point of vision (normal: 20 feet); ciliary body relaxed
                    Close -- accomodation of the lenses (to near point of vision, if necessary), 
                        constriction of  pupils, convergence of the eyeballs
                Near point of vision recedes with age as lens elasticity decreases

        Functional Anatomy of Photoreceptors: Inner and outer segments, with discs containing 
                visual pigments. 
Pigments consist of retinal and different opsins (depending on 
                receptor type); retinal changes shape (bleaches) and comes off opsin when struck
                by light, which opens ion channels and generates graded potentials (hyperpolarization)
            Discs (and pigments) -- recycled (phagocytotically by cells of pigmented layer) 
                    following a circadian rhythm. The discs are the receptive surface (with the pigments,  
                    as described); the different pigments make different receptors differentially sensitive 
                    to different wavelengths:
            rods -- dim light (VERY sensitive), gray tones, respond strongly to slight changes in
                    intensity of light (motion detectors); cones -- three different color sensitive populations;
                understand color blindness.  Rods and cones wired differently: rods diffusely (many 
                    rods per one ganglion cell), cones straight through (one or few cones per ganglion 
                    cell); explains acuity

     Light Transduction -- non-photostimulated receptors are depolarized in the dark and generate
        dark current; when light strikes photopigments, Na+ entry inhibited and rods/cones hyper-
        polarize (!), turning off NT release (still effective at transmitting info; see visual processing).
        Receptors and bipolar cell generate graded potentials; only ganglion cells produce AP=s.
    Light and Dark Adaptation -- know generalized concepts
    Visual Pathway to Brain -- optic nerves, chiasma, tracts
        Field of view of eyes overlaps; neurons from both eyes receiving information from a part 
        of the field pass to one side of occipital cortex, through thalamus, which sharpens image 
        and emphasizes middle of field of view (see thalamic processing*). This sorting of 
        information allows for stereoscopic vision/depth perception
    Visual processing --
            Basal (dark) current unaffected by illuminating entire retina
            Ganglion cell currents change dramatically with spot illumination
         Generalized pattern of info processing: light hyperpolarizes receptors "on" bipolar 
            neurons depolarize, "off" bipolar neurons hyperpolarize, which in turn excite ("on") 
            or inhibit ("off") the ganglion cells with which they synapse cones have straight 
            through connections (sharp images), whereas rods are integrated in the retina (amacrine 
            cells) and more than one feeds a given ganglion cell (fuzzy images)
    *Thalamic processing (discussed above) -- sharpen contrast and emphasize center
    Cortical processing

IV.  Hearing and Balance -- The Ear; both mechanoreception due to fluids bending cells
  Structure of the Ear: outer, middle and inner
    1.  Outer Ear: auricle (pinna), external auditory meatus, tympanic membrane (eardrum)
            Pinna internal structure elastic cartilage; ceruminous glands in canal; eardrum flattened 
            cone with skin externally, mucosa internally
    2.  Middle Ear (tympanic cavity): auditory tube; ossicles (malleus, incus, stapes); round 
            and oval windows (membrane-covered openings in bony wall; stapes in contact with 
            oval) Auditory tube allows for equalization of pressures on both sides of eardrum for 
            normal passage of sound to inner ear
        Ligaments suspend bones in cavity, and muscles (tensor tympani on malleus and stapedius 
            on stapes); contract reflexively with very loud sounds
    3.  Inner Ear (labyrinth): bony and membranous labyrinths, filled with peri- and endolymph,     
            respectively; house vestibule, semicircular canals and cochlea. Cochlea with 
            scalae (vestibuli, tympani, media); media houses spiral organ of Corti (with basilar 
            membrane and hair cells, embedded in tectorial membrane)

Hearing
: detection of sound (compressions/rarefactions) by spiral organ of Corti
    Sound Properties: know wavelength (frequency/pitch), quality, intensity (amplitude/loudness)

    Transmission of sound to inner ear: waves strike eardrum; move ossicles (in order given 
        above); stapes moves against oval window. Since eardrum larger than oval window, 
        sound transmission to inner ear enhanced .20 times; sets perilymph in motion. Wave
        travels up scala vestibuli, transmitted through vestibular membrane to endolymph in scala
        media
or cochlear duct.  This wave sets basilar membrane, tuned by length of CT fibers,
        in motion, which sets hair cells in motion thereby bending cilia embedded in tectorial
        membrane
. Fibers near oval window short, respond to high frequencies; near tip long,
        respond to low frequencies. Cochlear nerve neuron dendrites coiled around bases of hair cells,
        and pass the information on to brain.  Waves dissipated down scala tympani, and pressure
        of waves in the fluid "released" at round window.

     Auditory pathway: part of cranial nerve number VIII to medulla, sound from both ears sent 
            to both temporal lobes (through thalamus); allows comparisons for localization of sound*

    Auditory processing: can clearly hear separate sounds within mix; processing clearly complex. 
            Understand
processing of pitch (discussed above), loudness, and localization of sound*.

Equilibrium and Orientation: organs are maculae within saccule and utricle in vestibule, and 
        crista ampullaris in semicircular canals.  Works with concept of inertia.

    Static Equilibrium (linear): maculae within the saccule and utricle of the vestibule
         Maculae not unlike spiral organ of Corti, with supporting cells surrounding hair cells 
            embedded in otolithic membrane, which has otoliths (calcium carbonate crystals).
            In utricle, macula is horizontal; in saccule, macula is nearly vertical. Linear motion 
            bends cilia as otolithic membrane experiences inertial non-movement.

    Dynamic Equilibrium (rotational): crista ampullaris in ampullae of semicircular canals
        Semicircular canals -- each ear with one in each plane, each with swollen ampulla housing
            crista ampullaris
.  Crista has cupula in which dendrites of vestibular nerve are embedded;
            cupula bends dendrites as endolymph moves with rotation; a given pair of cristae in the
            frontal or transverse plane will be stimulated oppositely in two ears with single rotational
            movement (the two in the sagittal plane will be stimulated similarly).

    Equilibrium pathway (includes visual/proprioceptive/skin tactile inputs; vestibular nystagmus) --   
        Vestibular nerve to several places (see Figure 15.36, pg. 583)