Central Nervous System

nervous system divided into

2 parts

central nervous system

consists of brain; contains 97% nervous tissue and spinal cord

peripheral nervous system

all other nervous tissue; cranial and spinal nerves, ganglia

gray matter

made of neuronal cell bodies; located on outside in cerebrum, inside in spinal cord

gray matter in CNS

nuclei

grey matter in PNS

ganglia

white matter

bundles of myelinated axons; located on inside in cerebrum, and outside in spinal cord

white matter in CNS

tracts and fibers

white matter in PNS

nerves

physical protection of brain

skin, cranial bones, cranial meninges

cranial bones

tough flat bones forming the skull

cranial meninges

3 layers of fibrous connective tissue separating brain from bone; dura, arachnoid, pia mater

dura mater

outermost thickest/fibrous layer

arachnoid mater

thin, web like with mesh

pia mater

delicate layer resting directly on surface of gray matter

subarachnoid space

region below arachnoid mater; filled with CSF and trabeculae to cushion brain

meningitis

infection of meninges; early treatment involves antibiotics that cross BBB, must be admitted ASAP

bacterial meningitis

can cause stroke, hearing loss, permanent brain damage

viral meningitis

caused by enteroviruses, less serious than bacterial

fungal infection

can also cause meningitis

cells in CNS

neurons, astrocytes, oligodendrocytes, microglia, ependymal cells

neurons

receiving, processing, integrating, transmitting signals between cells

astrocytes

structural support, contributes to BBB, ion homeostasis, forms synapses

astrocyte foot processes

secrete paracrine signals that prompt tight junction formation in endothelial cells

oligodendrocytes

producing myselin sheath around axons in cells

microglia

macrophages of the brain; immune protection and activates during inflammation or injury by releasing toxic factors

ependymal cells

line brain ventricles/produce CSF

cerebrospinal fluid (CSF)

clear, colorless liquid contained within subarachnoid space in ventricular system

80% of CSF is produced by

ependymal cells in the choroid plexus

20% of CSF is produced in

fluid filled space between neurons/capillaries; brain interstitial system

functions of CSF

support, homeostasis, immune function

support/buoyancy of CSF

suspension of brain in CSF reduces weight of the brain

CSF homeostasis

regulates ion and nutrient concentrations

CSF immune functions

provides fluid filled medium that circulates through subarachnoid space

circulation of CSF

flows from ventricles into subarachnoid space; drains through arachnoid granulation villi into dural venous sinuses

CSF diagnostic tool

lumbar puncture spinal tap from subarachnoid space; below end of spinal cord

purposes of CSF diagnostic tool

samples CSF for cell count, glucose, protein, bands; helps diagnose meningitis, multiple sclerosis, encephalitis, neurosyphilis

blood brain barrier (BBB)

formed by brain microvessel endothelial cells; joined by tight junctions and reinforced by astrocyte foot proceses

functions of BBB

controls molecular traffic, blocks toxins, maintains low protein levels for pathogen prevention, ion homeostasis

ions allowed in BBB

small lipophilic molecules and oxygen

membrane transporters

move glucose from plasma into brain interstitial fluid

metabolic needs of the brain

brain receives 15% of hearts blood output at rest, consumes around half of body’s glucose

progressive hypoglycemia

low glucose; leads to confusion, unconsciousness, death

blood supply to the brain is through

internal carotid arteries, vertebral arteries, circle of willis

internal carotid arteries

anterior circulation

vertebral arteries

posterior circulation

circle of willis

provides alternative blood routing if a vessel fails

jugular vein

returns blood; internal jugular exits through jugular foramen to return to arterial system

cerebrum

handles higher level brain functions, conscious thought, sensory processing, voluntary motor control

regions of brain

cerebrum, diencephalon, brainstem, cerebellum

cerebrum is known for

higher brain functions

diencephalon is known for

homeostatic controls

brainstem is known for

autonomic reflex center

cerebellum is known for

coordination of movement

longitudinal fissure

divides left and right hemispheres

transverse fissure

separates cerebrum from cerebellum

lateral fissure

separates frontal and parietal from temporal lobe

central sulcus

separates frontal from parietal lobe

gyri

ridges or bumps on surface of cortex

sulci

grooves between gyri; folds increase surface srea of cortex for more neural connections

coronal plane

front and back

transverse plane

upper and lower

sagittal plane

left and right

contralateral control

cerebral hemispheres control opposite sides of body

EQ

used to compare actual brain size to expected brain size relative to body weight

humans have highest

EQ of any animal; much larger than expected

neuronal density

cerebral cortex has highest amount of mass but lower neurons, cerebellum has lower mass but higher in neurons

increased connectivity

number of neurons doesn’t change but amount of connections between neurons does

white matter tracts

commisural, projection, association fibers

commisural fibers

connect left and right hemispheres

projection fibers

connect cerebrum to other lower brain regions or spinal cord

association fibers

connect different regions within same cerebral hemisphere

5 lobes of cerebrum

frontal, parietal, temporal, occipital, insula

frontal lobe functions

hypothesis generation, planning and organizing, personality, motor control

parts of frontal lobe

primary motor cortex, brocas area, olfactory bulb

primary motor cortex

precentral gyrus; when stimulated, body moves

brocas area

speech; left hemisphere

olfactory bulb

odor perception

parietal lobe functions

sensation and sensory integration; spatial awareness and perception

parts of parietal lobe

primary somatosensory cortex (postcentral gyrus) and somatosensory association cortex

primary somatosensory cortex (post central gyrus)

receives raw touch, temperature, and pain stimuli

somatosensory association cortex

process/interprets sensory information

temporal lobe function

hearing. language comprehension, smell, long term memory formation/retrieval

parts of temporal lobe

primary auditory cortex, wernickes area, hippocampus

primary auditory cortex

processes hearing

wernickes area

responsible for language comprehension; left hemisphere

hippocampus

converts short term into long term memories

occipital lobe functions

processing, integration, interpretation of visual stimuli

parts of occipital lobe

primary visual cortex and visual association area

primary visual cortex

receives visual data; builds 2D sketch

visual association area

interprets information from primary visual cortex

insula function

deep inside lateral fissure; consciousness, emotion, homeostasis, taste, smell, compassion, empathy

interoceptions in insula

awareness of hunger, pain, fatigue

the homunculus

motor and somatosensory cortex map of human body; size of each part corresponds to brain tissue dedicated to controlling it

language areas

receptive sensory language area and expressive motor speech area

receptive sensory language area

wernickes; stroke affects understanding language

expressive motor speech area

broca’s; stroke affects expressing language

articulate fasiculus

connects brocas and wernickes via association fibers

diencephalon is located

between brainstem and cerebrum

3 major regions of diencephalon

epithalamus, thalamus, hypothalamus