Central (CNS): neurons whose cell bodies, axons, & dendrites lie entirely within the cranium or vertebral canal

Peripheral (PNS): neurons that link the CNS to the peripheral tissues/organs

• cerebral hemispheres (cerebrum)
• Diencephalon
• Brainstem
•  Cerebellum

1. frontal
2. temporal
3. parietal
4. occipital
5. limbic

• higher mental function (judgment, planning, reason, conscience)
• speech & language center

• relay station for sensory impulse
• transfers impulse to correct part of cortex for localization & interpretation

• autonomic nervous system center
• regulates body temp & metabolism
• controls water balance
• hunger center
• limbic system (i.e. emotions)
• where pituitary gland attached

• forms roof of 3rd ventricle
• houses pineal body & endocrine gland
• includes choroid plexus
• forms cerebrospinal fluid 

• gray matter (sensory & motor nuclei of cranial nerves)
• white matter nerve tracts
• 3rd & 4th ventricles
• cerebral aqueduct

• maintenance of balance, posture, & coordination
• timing & strength of muscle contractions

provide protection of brain & spinal cord

dura mater, arachnoid, & pia mater

• similar in content to blood, but less protein
• maintains balance of extracellular fluid in brain
• about 400 mL/day of CSF circulates through ventricular system then drains into venous circulation

protective feature composed of extensive capillaries & sinuses that:

• protects brain from hormones & circulating chemicals
• has tight junctions to limit permeability
• has astrocyte processes to secrete paracrines
• has glucose transporters 

• cell body (soma)
• specialized slender processes (axons/dendrites)
• receptive/input region (dendrites/soma)
• conducting component (axon)
• secretory/output region (axon terminal)

• astrocytes
• oligodendrocytes
• microglia
• ependymal cells 

• Schwann cells
• satellite cells

help neurons survive by providing structural & metabolic support

(this can include taking up excess K+ & neurotransmitters)

bundles of neurons that form discrete white, flat, or circular threads visible to naked eye in PNS

(usually include sensory & motor fibers)

• comparable to nerve, except runs w/n CNS
• composed of bundles of axons of interneurons
• either ascending or descending

Internal carotid artery:

• arises in neck
• enters cranial cavity via carotid canals
• terminates as anterior & middle cerebral arteries
• joined to posterior cerebral artery by posterior communicating artery 

• medial brain
• superior brain
• frontal pole

• lateral brain
• temporal pole 

What are the areas supplied by the posterior cerebral artery?

• inferior brain
• occipital pole 

31 pairs

(1 less cervical vertebra than cervical spinal nerves)

What are the enlargements of the spinal cord and what are they due to?

• cervical (C5-C8) & lumbosacral (L4-S1)
• due to large # of axons entering & leaving spinal cord to innervate the extremities

• "medullary cone"
• terminal end of spinal cord
• near lumbar vertebral levels 1 & 2

• continuation of spinal nerves as dangling nerve roots after spinal cord tapers out

integrates information

= cell bodies, neuroglia, unmyelinated axons, & dendrites of motor neurons

1. posterior horn
2. lateral horn
3. anterior horn

(all shaped like an "H")

• information travels to and from brain
• myelinated axons
• white matter of spinal cord divided into columns/funiculi by gray matter horns

1. anterior white columns
2. posterior white columns
3. lateral white columns

(all columns contain tracts that carry information)

• aka Meissner's corpuscles
• type of mechanoreceptor
• responsible for sensitivity to light touch
• skin; especially fingers & lips

• bulbous capsules in the skin containing sensory nerve endings
• can be mechanoreceptors or thermoreceptors
• sensitive to cold (< 20 C)

• aka pacinian corpuscle
• numerous small oval bodies
• sensitive to pressure
• concentric layers of connective tissue

• unspecialized, afferent nerve ending
• cutaneous receptors
• used by vertebrates to detect pain in skin

• aka Merkel's corpuscle
• disklike expansion of nerve fiber end
• tactile function
• associated w/ sense of light touch to discriminate shapes & textures

oval receptor cells found in the skin of vertebrates that have synaptic contacts w/ somatosensory afferents

(associated w/ Merkel discs)

• most common
• includes interneurons & motor neurons

1. Peripheral Nerves
2. Ganglia
3. Nerve Plexuses

What are the somatic and visceral components of peripheral nerves?

(spinal: 31 & cranial: 12)

Somatic:

supply the sensory & motor innervation of skin & muscle

Visceral:

supply the sensory & motor innervation of internal organs

• Somatic - (sensory only); dorsal root ganglia
• Autonomic - (motor to viscera); paravertebral, prevertebral, & enteric

• cervical
• brachial
• lumbar
• sacral
• coccygeal

• General somatic - skin, sensors, body positions
• Special somatic - vision, hearing, balance
• General visceral - organ distention
• Special visceral - taste, smell

• General somatic - to skeletal muscle
• General visceral - to smooth, cardiac muscle
• Special visceral - to facial & speaking muscle

• parasympathetic
• sympathetic
• enteric

• maintain homeostasis
• fight or flight response
• rest & digest response

• fight or flight
• release adrenaline & noradrenaline
• increase heart rate, blood pressure, & blood flow to skeletal muscles
• inhibition of digestive functions

• rest & digest
• calms body to conserve/maintain energy
• lowers heart & breathing rates
• lowers blood pressure

• Sympathetic - pupils dilate
• Parasympathetic - pupils constrict

• Sympathetic - decreases
• Parasympathetic - increases

• Sympathetic - perspires
• Parasympathetic - dries

• Sympathetic - increases
• Parasympathetic - decreases

• Sympathetic - accelerates
• Parasympathetic - slows

• Sympathetic - inhibits
• Parasympathetic - activates

• Sympathetic - secretes stress hormones
• Parasympathetic - decreases secretion of stress hormones

• detect whether it is light or dark
• have a single lens

• found in insects, crustaceans, arachnids, & other multi-jointed legged creatures
• combine what they see into single image or multiple images

1. fibrous coat - cornea, sclera
2. vascular coat - choroid, ciliary body, & iris
3. retina

• tough, white outer coat of eyeball covering approximately the posterior 5/6ths of surface
• continuous anteriorly w/ cornea & posteriorly w/ external sheath of optic nerve
• forms principal part of outer fibrous coat

• protects intraocular contents
• maintains shape of the globe when distended by intrinsic intraocular pressure
• relatively avascular, has irregular connective tissue, & matrix collagen

• transparent part of the coat of the eyeball that covers the iris & pupil
• transparency due to regularity & smoothness of epithelium covering, avascularity, & components of stroma

• responsible for most of eye refraction
• admits light to interior
• refracts light, yielding 2/3rds of eye's optical power

• provides oxygen & nourishment to outer layers of retina
• along w/ ciliary body & iris, forms uveal tract

• composed of ciliary muscle & ciliary processes
• ciliary muscles attached to the lens by connective tissue structure called zonule of Zinn

• responsible for black & white vision
• low light levels
• more numerous (120 million)
• chemical is rhodopsin

• responsible for color vision
• high light levels
• less numerous (6-7 million)
• chemical is one of three cone pigments

1. Outer segment - contains chemicals that decompose upon exposure to light & excite nerve fibers leading to optic nerve
2. Inner segment
3. nucleus
4. synaptic body

• made up of continuation of axons & ganglion cells
• transmits visual information from the retina to brain

• yellowish circle in the center of the retina
• responsible for clear, distinct vision
• sharp visual acuity

• lies within the macula lutea
• area with only cones
• responsible for sharpest visual acuity

• small circular region of retina where axons of the ganglia (as fibers of the optic nerve) emerge from the eyeball
• contains no rods or cones
• optically insensitive
• aka blind spot

• transparent jelly-like substance behind the lens
• largest structure of the eye (80% of globe)
• unique connective tissue
• up to 98.5% water
• spherical shape

• b/n the iris & corneal endothelium (most inner surface of cornea)
• filled w/ aqueous humor produced by epithelium of ciliary body

• nourishes cornea & lens
• secreted by the ciliary body

• behind edge of iris & suspensory ligaments of lens & ciliary processes
• aqueous humor first passes through here on its way to the anterior chamber
• is not the vitreous chamber

• spongy tissue around base of cornea near ciliary body
• guards the entrance to the Canal of Schlemm
• responsible for most of resistance to flow of aqueous humor through the canal

• part of the world seen by the patient with both eyes and looking straight ahead
• total area that can be seen in peripheral vision when the eyes are focused on a central point

• light from the right visual world strikes the left temporal and right nasal retinas
• light from inferior world strikes superior retina (and vice versa)

• region of the visual field whose stimulation affects the activity of a single neuron
• arranged in central area (center) & concentric circle (surround) which respond oppositely to light
• detects edges & contrast (i.e. center is depolarized so surround is hyperpolarized)

• almost 1/2 of cerebral cortex devoted to processing visual information
• located in occipital lobe
• 2 broad divisions are primary & secondary visual cortexes

• left visual cortex receives input from right visual field (& vice versa)
• superior cortex receives input from interior visual field (& vice versa)

1. Mangocellular - "Where?" : conceptualising movement of objects & their position in space
2. Pavocellular - "What?" : detailed visual information used for the recognition of objects

• in animals w/ 2 forward-facing eyes
• 2 retinal images go through series of sensory & motor processes resulting in the perception of singleness & depth

• two corresponding retinal points (2 foveae)
• retinotopic mapping
• 6  EOM in each eye create version
• visual motor feedback (i.e. fusion)
• medial rectus contraction & lateral rectus relaxation

• sensation for depth
• ability to perceive the relative distances of separate objects
• judgement of distance/depth can occur w/ monocular cues
• refers exclusively to binocular retinal disparity

color vision is the result of absorption of light by different classes of cones

• short (S-cones): 440nm
• middle (M-cones): 545nm
• long (L-cones): 565 nm

• when eye samples information of images on retina, info is integrated so the objects appear to be stable
• intermittent stimuli can be perceived as separate or continuous depending on rate
• slow rate = perceived as separate; image stays on but changes in intensity (flicker)

the change in direction of a ray of light (i.e. bending) when passing from one medium to another

the eye refracts light to create an image on the retina

• similar to simple diffusion, but process is aided by a protein which functions as a pump or channel
• protein responds to its binding molecule (ligand)

• gated channel is opened by various signals & named for those
• initiating stimulus can be an electric current, ligand, or mechanical stress

• molecule is pumped from area of low concentration to an area of high concentration
• requires expenditure of energy in the form of ATP

• process that occurs from receptor activation to cellular response
• signal generally a molecule which binds specifically to a protein receptor (that be intra- or extra- cellular)

• activated transducer stimulates primary effector which stimulates production of second messenger
• second messenger stimulates secondary effector
• initiates series of steps...eventually leads to cellular response

• a phosphorylated protein can activate a different protein kinase & so on until cell effect achieved
• each signal molecule can activate thousands of second messengers

1. signal molecules bind to receptor initiating activation of G-protein
2. G-protein activates guanylate cyclase which catalyzes formation of cGMP from GTP
3. cGMP is second messenger
4. enzyme phosphodiesterase hydrolyzed cGMP, destroys it, & ends process

• connected through thin connecting cilium
• outer filled w/ dense stack of membrane discs
• discs carry visual pigment & other transduction components
• inner contains endoplasmic reticulum & Golgi & packed with mitochondria

• synaptic terminal transmits light signal to 2nd order neurons in the retina (bipolar & horizontal cells)
• in darkness: steady inward current through cation conductance on outer-segment membrane
• this depolarizes rod/cone & maintains synaptic release of glutamate

• light closes cation conductance (consists of cGMP-gated channels) to stop dark current
• produces membrane hyperpolarization which decreases/terminates dark glutamate

• Na+/K+ pump on inner segment of rod
• pumps 3 Na+ out for every 2 K+ in (results in inside negative charge)
• outer segment contains Na+ channels; when open allow Na+ to travel down gradient into this portion of cell (negates much of charge)

• open under dark conditions
• resulting charge about -40 mV (average is -70 mV)

• Na+ permeability is decreased but Na+ is still being pumped out
• results in greater inside negativity of the cell
• this is known as hyperpolarization

• Rhodopsin (scotopsin + 11-cis-retinal) absorbs light
• converted to bathorhodopsin
• this decays to lumirhodopsin
• further decays to metarhodopsin I then metarhodopsin II
• this splits completely into scotopsin and all-trans-retinal

• rhodopsin all-trans-retinal converted to 11-cis-retinal via retinal isomerase
• this combines w/ scotopsin to make rhodopsin

• it destroys it
• since cGMP was holding Na+ channels of outer segment open, the channels close resulting in hyperpolarization

• within seconds, rhodopsin kinase inactivates the activated rhodopsin & entire process reverses