Divisions of the nervous system (see Nervous System 1)

Review of tissue types

	White matter - mostly myelinated axons; serves as set of "cables" that transmit information
	Gray matter - mostly cell bodies and dendrites (many synapses); serves as set of "processing centers" or "control centers" Islands of gray matter are called nuclei (CNS) or ganglia (PNS)

Review types of pathways

	Afferent = toward the center
	Efferent = away from the center

Brain (located in cranial cavity)     GA

	Brain stem: medulla, pons, and midbrain     GA Lower level of regulation Control centers for respiration, digestive reflexes, cardiac reflexes, etc. Eye/ear reflexes Corpora quadrigemina (midbrain)  (quadri = "four"  gemina = "twins") Superior colliculi (eye) Inferior colliculi (ear) Pain modulation Pathways for conducting sensory information upward and motor information downward Includes much of the reticular activating system (RAS) Reticular formation: network of gray matter areas     GA "Filters" incoming sensory information and assesses its value/importance Stimulates the higher centers (in cerebrum) to stay awake Some drugs affect the RAS, for example: Barbiturates depress the RAS, reducing alertness Amphetamines stimulate the RAS, increasing alertness Features Pyramids (medulla) Decussation of pyramids (crossing over of some spinal, left-right & right-left)    GA   GA Olives (medulla) Corpora quadrigemina (midbrain) Cranial nerves 12 pairs, all originating on brain stem     GA Can be primarily sensory, motor, or mixed nerves    GA  GA Named by Roman numeral (I, II, III, . . .) beginning with most anterior pair Also named descriptively (Olfactory, Optic, . . .)
	Cerebellum Roughly spherical organ attached to posterior side of brainstem Wrinkled surface of gray matter    GA  GA Regular sulci (grooves) and gyri (raised areas) Allows larger surface area and therefore more processing capability Cerebellum also has more neurons than all other parts of the brain combined Arbor vitae ("tree of life")    GA Interior branches of white matter Gray matter gyri are therefore often called  called folia (literally "leaves") Connections ("wiring")    GA Coordination & planning of skilled muscle activity Motor program = set of nervous signals that accomplish a specific set of movements Some postural regulation (muscle tone, balance) Recent evidence shows it has a much broader role than previously thought, perhaps also being involved "behind the scenes" in many of the cerebrum's more complex functions.
	Diencephalon (lit. "the between-brain") Just superior to brainstem Main regions Thalamus Oval mass of gray matter Two lateral masses joined by thinner intermediate mass Acts as a "switchboard" for information heading up to higher centers (in cerebrum) Low level of consciousness, sensory perception, emotional response Some motor regulation Hypothalamus Below thalamus Mostly small nuclei (areas of gray matter) Neuroendocrine link Homeostatic control centers Center of limbic system Limbic system is a ring of structures in different regions of the brain that center around the hypothalamus Limbic system allows emotional feelings to occur Communicates with conscious centers in cerebrum to allow our thoughts and feelings to be "connected" Pineal body Posterior, cone-shaped structure (pineus = "pine") Another neuroendocrine link Acts as part of body's internal clock Has inputs from the eye that help determine time of day, month, year using fluctuations of daylight and moonlight Releases the timekeeping hormone melatonin to signal other parts of the body "what time it is" Melatonin is an altered form of the neurotransmitter serotonin Brain sand     pp Calcifications in the pineal make it a good landmark in x-ray and CT imaging
	Cerebrum Cortex - gray matter; wrinkled outer surface of cerebrum     GA  GA Subdivided into hemispheres and lobes Hemispheres: left and right Lobes: frontal, parietal, temporal, occipital, insula   GA  GA Functional areas ---> see maps   GA   GA Localization - each job is located at a specific place Plasticity - some ability to change the place at which a job is done Hemisphericity: concept that one hemisphere is better than the other at certain jobs Left: Rt-hand control, spoken & written language, science & math skills, reasoning, sort out parts Right: Lt-hand control, music & art awareness, recognizing faces & 3-D objects, insight & imagination, grasps "whole" of parts Corpus callosum White matter band that connects left and right hemisphere, allowing integrated function     GA  GA Association fibers  White matter/fibers that connect various regions within a hemisphere     GA  Cerebral nuclei (basal ganglia) Islands of gray matter deep inside cortex     GA  GA Coordination of motor activity (motor programming) Functions: consciousness, thinking, problem solving, language, memory, and other complex integrative functions

Coverings of CNS

Bony coverings Cranial bones Vertebral column

Membranous coverings: meninges (sing. meninx) Dura mater ("tough mother") = fibrous outer covering can stop bullets (but don't count on it)     GA  GA Falx cerebri (falx = "sickle") Dural sinuses Falx cerebelli Tentorium cerebelli     GA Arachnoid mater ("spidery mother") = wispy middle covering Subarachnoid space = filled with cerebrospinal fluid (CSF) Pia mater ("delicate mother") = super-thin coating of brain and cord; innermost meninx     GA

Fluid spaces

	Cerebrospinal fluid (CSF) Filtrate from blood of choroid plexus     GA  GA Functions Support/cushioning Fluid for sampling/analysis
	Ventricles and canals     GA  GA  GA Lateral ventricles (left and right)     GA  GA Separated by septum pellucidum Third ventricle    GA Cerebral aqueduct (of Sylvius) Fourth ventricle     GA Lateral & median foramina Central canal Subarachnoid space    GA Reabsorption of CSF     GA

Electroencephalogram (EEG)

	Measured in waves/sec or Hertz (Hz)
	Show relative level of activity of a whole brain region Alpha waves (8-13 Hz) - waking, relaxed Beta waves (13+ Hz) - waking, attentive Theta (4-7 Hz) - drowsy Delta (<4 Hz) - deep sleep

Sleep

	Two states REM (rapid eye movement) - dream state SWS (slow wave sleep) - deep, dreamless sleep
	Swing back and forth between states  90-minute cycles Deepest at beginning of sleep period; gets less deep toward morning

PET

	Positron Emission Tomography
	Nuclear materials emit "positrons" that are detected by sensors
	Tomography is "making pictures of sections (cuts)"
	Can be used to visualize functions (for example, using oxygen or glucose at different rates in different parts of the brain)

Cranial nerves (12 pairs originating from brainstem)

Spinal nerves (31 pairs originating from spinal cord)

Both cranial and spinal nerves have numerous branches

Plexus (literally "braid") is network formed by intermingling of fibers from several different spinal nerves

Sensory: conscious sensation (vision, muscle position, touch, etc.)

	General principles of sensory reception Sensory receptors = structures that are sensitive to specific changes in their surrounding environment (either internal environment or external environment, depending on their location in the body) Receptor potential = voltage fluctuation that occurs in response to a change (sensory stimulus); it may or may not generate an action potential, depending on whether it (in combination with other receptor potentials) reaches the threshold potential at the axon Sensory adaptation = gradual cessation of response to a specific stimulus; in short, many receptors "fatigue" after the initial onset of a stimulus and stop responding to it Dermatomes - sections of the skin that correspond to pathways taken by sensory receptors
	Types of sensory receptors Functional categories (based on modality = what the receptor is sensitive to) Mechanoreceptors = sensitive to mechanical stimuli such as pressure, vibration, stretch, tilt, etc. Thermoreceptors = sensitive to changes in temperature (within a specific range) Photoreceptors = sensitive to changes in the intensity and color of light Chemoreceptors = sensitive to changes in chemistry (presence or absence of certain chemicals) Pain receptors = sensitive to damage or stimuli that may signal potential damage to tissues; any receptor can act as a pain receptor if overstimulated Structural categories (based on where in the body the receptor is located) Exteroceptors = near the exterior surface of the body (skin/mucous membranes) Interoceptors = located within internal structures of the body (muscles/organs)
	General senses Touch Pressure Temperature Proprioception (muscle sense) Pain </