Chapter 14: The Brain and Cranial Nerves

Cerebrum

-Largest portion.

-2 half globes called cerebral hemispheres.

Longitudinal fissure

divides the 2 half globes of the cerebrum

Gyri

thick folds that mark the cerebrum

Sulci

shallow grooves that mark the cerebrum

Corpus Callosum

a thick bundle of nerve fibers that connects the cerebral hemispheres

Cerebellum

-2nd largest part of the total brain and contains 50% of neurons.

-2 of them separated by transverse cerebral fissure.

Brain stem

-everything else.

-major components: diencephalon, midbrain, pons, medulla oblangata.

Gray Matter

-neurosomas, dendrites, and synapses (same as spinal cord).

-intergration: the thinking part (receives signals).

-outer portion.

White Matter

-bundles of axon.

-sends/moves signals.

-lies deep to cortical gray matter (opposite relation in the spinal cord).

Dura Mater

-superficial.

-pressed closely against the cranial bones but not attached.

Arachnoid mater

-middle.

-Transparent membrane over brain surface.

Pia mater

-deep.

-Very thin and follows the contours of the brain.

-not usually visible without a microscope.

Cerebrospinal fluid (CSF)

fluid in the brain.

3 Functions of CSF

-buoyancy (helps it float in the middle).

-protection.

-chemical stability.

Hydrocephalus

abnormal accumulation of CSF in the brain from a blockage in its route of flow.

-can be fatal.

-in a fetus or infact, the entire head can swell due to unfused cranial bones.

-treated by placement of a shunt.

Blood-brain barrier (BBB)

Barrier between blood and brain.

-consists of a tight junction between endothelial cells that form the capillary walls.

-highly permeable to: H20, glucose, 02, C02, alcohol, caffeine, nicotine, and anesthetics.

Regions of the Brainstem

from rostral to caudal:

-diencephalon,

-midbrain.

-pons.

-medulla oblongata.

(-spine)

Reticular Formation

gray matter than run vertically through all levels of the brain stem.

Reticular Formation Functions

-somatic motor control.

-cardiovascular control.

-pain.

-sleep and consciousness.

-habituation (ignore constant stimuli).

Hindbrain

-medulla oblongata.

-pons.

-cerebellum.

Medulla Oblongata

contains:

-Glossopharyngeal nerve (IX)

-Vagus nerve (X)

-Accessory nerve (XI)

-Hypoglossal nerve (XII)

The Pons

contains:

-Trigeminal nerve (V)

-Abducens nerve (VI)

-Facial nerve (VII)

-Vestibulocochlear nerve (VIII)

The Midbrain

contains:

-Oculomotor nerve (III)

-Trochlear nerve (IV)

Cerebellum functions

-motor muscle contractions and coordination.

-Evaluation of sensory input.

-timekeeping center (predicting movement of objects etc.)

-hearing.

Forebrain

-diencephalon.

-telencephalon (or cerebrum).

Diencephalon

-thalamus.

-hypothalamus.

-epithalamus.

Thalamus

-largest part of the diencephalon.

-the gateway to the cerebral cortex (nearly all input passes through).

functions:

-motor control.

-memory.

-emotional functions.

Hypothalamus

-control center of the endocrine and ANS.

-attached to the pituitary gland.

functions:

-hormone secretion.

-autonomic effects (integrating center).

-thermoregulation.

-food and water intake.

-sleep and circadian rhythms.

-memory.

-emotional behavior.

Epithalamus

-composed primarily of the pineal gland.

-primary function is to produce melatonin.

General Anatomy of the Cerebrum

-frontal lobe.

-insula.

-parietal lobe.

-temporal lobe.

-occipital lobe.

Cerebral White Matter

has 3 kinds of tracts:

-projection tracts: extend vertically; carries information between the brain and body.

-commissural tracts: cross between hemispheres.

-association tracts: connect different regions of the same hemisphere (inside one).

Neural Integration

-cerebral cortex.

-basal nuclei.

-limbic system.

Electroencephalogram (EEG)

-monitors electrical activity called brain waves.

-4 types: alpha, beta, theta, delta.

Alpha waves

awake and resting with eyes closed and mind wandering.

Beta waves

eyes open and performing mental tasks.

Theta waves

sleepy children or drowsy light sleeping adults.

Delta waves

deep sleep in adults.

Sleep

-temporary state of unconsciousness.

-restorative effect: brain glycogen and ATP levels increase in non-REM.

-memories strengthened in REM.

Stage 1 of sleep

Feel drowsy, close eyes, begin to relax.

-Alpha waves

Stage 2 of sleep

Pass into light sleep.

-Theta waves.

Stage 3 of sleep

Moderate to deep sleep.

-theta and delta waves appear.

Stage 4 of sleep

called slow-wave sleep (SWS): high-amplitude delta waves.

Information Management

-Learning.

-Memory.

-Forgetting.

Declarative memory

inability to describe past events.

Amnesia

defects in declarative memory

Anterograde amnesia

unable to store new information

Retrograde amnesia

person cannot recall things known before the injury.

Cerebral Lateralization

difference in the function of the cerebral hemispheres.

Left Hemisphere

usually the categorical hemisphere.

-math and sciences.

Right hemisphere

usually the representational hemisphere.

-musical and artistic skill.

Epilepsy

sudden, massive discharge of neurons.

Migraine headaches

recurring headaches often accompanied by nausea, vomiting, dizziness, and aversion of light.

Schizophrenia

disorder involving delusions, hallucinations, inappropriate emotional response to situations, incoherent speech and withdrawal from society.

Bell palsy

paralysis of the facial muscles on one side resulting in distortion of facial features.