Central Nervous System

THE BRAIN

Neural Tube

Develops into the central nervous system in embryos.

VentriclesCavities in the brain

filled with cerebrospinal fluid.

Cerebral Hemisphere

SpeechMemoryLogical and emotional responseConsciousnessInterpretation of sensationVoluntary movement.

Parts of the Brain

a) Gyri – elevated ridges of tissue.

b) Sulci – shallow grooves that separate the gyri.

c) Fissures – deeper grooves that separate large regions of the brain.

d) Lobes – parietal, occipital, temporal, and frontal.

Lobes

Parietal lobe – somatic sensory area (excluding special senses).

Occipital lobe – visual Temporal lobe – auditory and olfactory Frontal lobe – primary motor area

Lobes

Parts of the Brain

e. Cerebral cortex – gray matter

f. Cerebral white matter – fiber tracts (bundles of nerve fibers)

g. Corpus callosum – connects the cerebral hemisphere

h. Basal nuclei – small “islands” of gray matter buried deep within the white matter of the cerebral hemispheres.

Diencephalon or Interbrain

a) Thalamus – relay station for sensory impulses passing upward to the sensory cortex.

b) Hypothalamus – floor of diencephalons; regulation of body temperature, water balance, and metabolism; center of many drives and emotions.

c) Epithalamus – pineal body; choroids plexus – capillaries within each ventricle that forms cerebrospinal fluid.

Diencephalon - Interbrain

Epithalamus

Brain Stem

a) Midbrain – reflex centers involved with vision and hearing.

b) Pons – breathing

c) Medulla oblongata – heart rate, breathing, blood pressure, swallowing, and vomiting.

Brain Stem

Cerebellum

Has two hemispheresOuter cortex of gray matter and inner

region of white matter. Controls precise timing for skeletal muscle

activities; controls balance and equilibrium.

Cerebellum

Protection

MeningesCerebrospinal FluidBlood-Brain Barrier

Meninges

Dura mater

Arachnoid mater

Pia mater

Dura Mater

Periosteal layer – attached to inner surface of skull.

Meningeal layer – outmost covering of brain extending to the spinal cord.

Arachnoid Mater

Subarachnoid space – between arachnoid mater and pia mater

Arachnoid villi – projections that protrude through the dura mater

Absorbs cerebrospinal fluid

Pia Mater

Clings tightly to the surface of the brain and spinal cord

Delicate layer

Cerebrospinal Fluid

Formed from blood by the choroid plexusChoroid plexus – cluster of capillaries

hanging from the roof of each ventricles.Cushions the brain from trauma or blowsForms and drains at a constant rate –

normal volume = 150 mL /half a cup

Circulation of CSF

Two lateral ventricles, Third ventricle, Cerebral aqueduct of midbrain, Fourth ventricle,

Some will flow down to the central canal of the spinal cord.

Most will circulate in the subarachnoid space.

The Blood-Brain Barrier

Composed of the least permeable capillaries.

Prevents the following from entering the brain – nonessential ions and amino acids, metabolic waste (urea, toxins, proteins, most drugs)

Does not prevent against – fats, respiratory gases, other fat-soluble molecules ( alcohol, nicotine, anesthetics)