Review Sheet -- Exam 4 Bio 2212 Dr. Adams
AUTONOMIC NERVOUS SYSTEM (purely motor); also called involuntary/visceral NS
See Figure 14.2
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
The autonomic ganglia, containing the synapses between the
preganglionic terminals and the
dendrites/cell bodies of the postganglionic neurons, are, as already indicated, purely motor.
Understand, too, that most of the axons (both pre- and post-) are
incorporated into cranial/
spinal nerves for much of their length.
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. See Figs. 14.2 - 14.6, Table 14.1
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) -- Figs. 14.5
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 14.6, pg. 539):
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 (pg. 544)
Interactions of the ANS divisions: SEE Table 14.5, pg. 546;
summary of effects of both 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. Coop-
erative 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
localized and brief diffuse (widespread) and longer . . .
Ganglionic synapses: Few Many, potentially at many levels
Postganlionic axons: branch sparsely at targets branch profusely at targets
ACh destroyed immediately
Norepinephrine taken back up by
by acetylcholinesterase postganglionic neuron (takes longer)
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
See also the "Structures to Know" sheet for the lab practical.
I. 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). See figs. 15.1, 15.2.
Tears with lysozyme, from lacrimal glands; oils from tarsal glands
Extrinsic eye muscle movements: saccades and scanning movements
Structure of the Eyeball -- layers in wall: Fig. 15.4
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. Inner (Sensory) (retina) -- pigmented and neural layer; Fig. 15.6
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 (in nm; color) within visual spectrum, reflection, refraction
Focal points; image inverted on retina; Fig. 15.12
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
Light perception: retinal changes shape by unbending (bleaches) and comes off opsin
within the membrane when struck by light, which opens ion channels and generates
hyperpolarizing graded potentials; rebends and reattaches to opsin when in the dark
Discs (and pigments): recycled (phagocytotically by cells of pigmented layer, Fig. 15.15)
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: SEE Fig. 15.10, pg. 564
rods -- dim light (VERY sensitive), gray tones, respond strongly to slight changes in
intensity of light (motion detectors); pigments are rhodopsins
cones -- three different color sensitive populations, different scotopsins; Fig. 15.10
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, the SHARPNESS of the image produced by cones.
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, which means light striking the medial aspect
of the retina on either side crosses over at the chiasma, but light striking the lateral aspect
does NOT cross over. Once past the chiasma, info passes 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; see Fig. 15.19
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 º "on" bipolar
neurons depolarize, "off" bipolar neurons hyperpolarize, which in turn excite ("on")
or inhibit ("off") the ganglion cells with which they synapse º cones have straight
through connections (sharp images), whereas rods are integrated in the retina (ama-
crine cells) and more than one feeds a given ganglion cell (fuzzy images)
*Thalamic processing (discussed above) -- sharpen contrast and emphasize center
II. & III. Chemical senses: Olfaction and Taste; respond to chemicals dissolved in water
II. Olfaction: organ of olfaction -- olfactory mucosa (Fig. 15.20) with olfactory receptors
(unique,ciliated, bipolar neurons, with regenerative capabilities); which are neurons of
cranial nerve I. Olfactory stem cells can differentiate into new supporting epithelial cells
or new bipolar neurons.several separate bundles passing through cribiform plate of
ethmoid, synapsing with mitral cells in olfactory bulb. Receptor turnover: 30-60 days.
Olfactory sensations: some 400 genes seem to be involved with olfaction; receptors
extremely sensitive to volatile substances dissolved in mucus. As with taste, smell may
involve pain reception
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
(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. Taste: organ of taste -- taste buds (Fig. 15.22) on papillae (approx. 10,000); some
papillae are 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: remember that cranial nerves VII, IX and X all involved.
Gustatory cortex in insula; involves multiple inputs, as indicated above, including over-
lap from sense of olfaction.
IV. Hearing and Balance -- The Ear; both mechanoreception due to fluids bending cells
Structure of the Ear: outer, middle and inner (Fig. 15.24)
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 (on basilar
membrane with hair cells, embedded in tectorial membrane) See Fig. 15.27.
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 (Fig. 15.31). 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
to both temporal lobes (through thalamus); allows comparisons for localization of sound*
Auditory processing: can clearly hear separate sounds within mix; processing clearly
Understand processing of pitch (discussed above), loudness, and localization of sound*.
Equilibrium and Orientation: organs are
maculae in sacs (utricle and
saccule) in vestibule (fig.
15.34), and crista ampullaris in semicircular canals (fig. 15.35). Dependent on 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. At constant speed
hairs not bent. Therefore, maculae detect initial movement, acceleration, deceleration,
Dynamic Equilibrium (rotational): crista ampullaris in ampullae of semicircular canals
Semicircular canals -- each ear with one in each of the three planes, 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. 593)