The Brain And Cranial Nerves Chapter 14

Front 1

The brain is divided into 4 principal parts

Back 1

i. brain stem, ii. Diencephalon, iii. Cerebellum, iv. cerebrum

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BRAIN STEM is divided into 3 parts

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i. medulla oblongata, ii. Pons, iii. midbrain

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DIENCEPHALON contains 3 parts

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thalamus, hypothalamus, epithalamus

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Protective and coverings of the brain include:

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i. cranial bones, ii. Cranial meninges, iii. Cerebrospinal fluid,

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CRANIAL MENINGES is divided into 3 parts

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dura mater (no space like in the spinal cord), archnoid mater, pia mater

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CEREBROSPINAL FLUID is produced

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in the VENTRICLES of the brain.

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The ventricles of the brain are

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4 large cavities that COMMUNICATE with each other, with the central canal of the spinal cord, and with the subarachnoid space..

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The 4 cavities of the brain are

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right and left lateral, third and fourth

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RIGHT LATERAL ventricle is located

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in the center of the right half of the brain.

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LEFT LATERAL ventricle is located

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in the center of the left half of the brain.

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THIRD ventricle location

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lies centrally within the DIENCEPHALON

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FOURTH ventricle location

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lies between the BRAIN STEM and the CEREBELLUM

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Cerebrospinal fluid (CSF) consists of

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a CLEAR colorless liquid that contains GLUCOSE, proteins, lactic acid, urea, electrolytes, and some WBCs.

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CSF is formed by

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EPENDYMAL (NEUROGLIA) cells through filtration capillary networks called COROID PLEXUSES which are located in the ventricles.

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Most of the CSF is absorbed by

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the ARACHNOID VILLI located in the subarachnoid space; they protrude into the SAGITTAL SINUS, a blood vein within the dura mater.

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The rate of formation and absorption of CSF are equivalent

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resulting in a constant PRESSURE (10mm Hg) and VOLUME (about 80-150mL). ½ LITER P/DAY

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HYDROCEPHALY is

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a condition in which the CSF pressure is elevated. – CAUSES SEIZURES, IS A BLOCKED “AQUADUCT” – SHUNT PUT IN TO OPEN THE AQUADUCT ALONG WITH A DRAIN THAT EMPTIES INTO THE STOMACH

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CSF contributes to homeostasis by

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protecting (serves as shock abosorber), delivering nutrients & removing waste from the brain

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Blood is supplied to the brain via

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the CIRCLE OF WILLIS AKA CEREBRAL ARTERIAL CIRCLE

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the circle of Willis is fed by

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The INTERNAL CAROTID and the VERTEBRAL arteries ARTERIES carry BLOOD Into the brain

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VEINS carry BLOOD

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AWAY from the brain

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the brain’s weight is

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2% of the weight of the body,

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the brain utilizes about 20% of the body’s total

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OXYGEN.

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The amount of oxygen utilized by the brain

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varies with the level of MENTAL ACTIVITY.

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Interruption of blood flow to the brain impairs

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neuronal function

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Interruption of blood to the brain for 1 to 2 MINUTES causes

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SLIGHT impairment.

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Interruption of blood to the brain for greater than 4 minutes can result in

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permanent injury and CELL DEATH

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GLUCOSE is the principal source of

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energy for brain cells.

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the blood supply of glucose must be continuous because

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the brain’s ability to store glucose is limited

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Low level of glucose in blood may cause

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mental confusion, dizziness, and loss of CONSCIOUSNESS (DIABETIC COMA)

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The BLOOD BRAIN BARRIER is

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a special mechanism composed of neuroglia termed ASTROCYTES.

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The BBB prevents certain materials, especially large molecules and MICROBES from

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passing from the blood to the CSF and brain.

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Glucose, oxygen, ALCHOHOL, nicotine, anesthetic agents, and certain ions

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easily pass across the BBB into the brain.

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Proteins, polysaccharides, many lipids, and most bacteria and viruses

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do NOT cross the BBB.

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the AIDS virus (HIV), polio virus, rabies virus, and a few other types of viruses and bacteria

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can cross the bbb into the brain.

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An injury to the brain from trauma, inflammation, or toxins can cause a

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BREAKDOWN of the BBB permitting passage of normally restricted substances into the brain.

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Brain Stem - The “medulla” is a continuation of

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the SPINAL CORD

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Brain Stem – The medulla forms

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the INFERIOR portion of the brain.

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Brain Stem – The medulla BEGINS

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AT THE MAGNUM FORAMEN

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Brain Stem – The medulla’s white matter contains

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all the ASCENDING (SENSORY) and DESCENDING(MOTOR) spinal tracts.

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Brain Stem – On the ventral side, two structures called PYRAMIDS conduct

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most of the nerve tracts in the body.

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Brain Stem – The pyramids cross each other close to the spinal cord junction at a point called

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the DECUSSATION of the pyramids.

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Brain Stem – one side of the brain controls sensory and motor impulses for the

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OPPOSITE side of the body.

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Brain Stem – RIGHT BRAIN controls

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LEFT BODY

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Brain Stem – LEFT BRAIN controls

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RIGHT BODY

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Brain Stem – The medulla gray matter contains a number of

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NUCLEI.

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The medullary nuclei act as

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REFLEX CENTERS for the regulation of vital body functions

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Brain Stem – The medulla Gray matter contains nuclei where neurons form synapses with one another which control vital body functions such as:

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HEART RATE, RESPITORY RATE, VASO CONSTRICTION (bLOODpRESSURE), SWALLOWING, COUGHING, VOMITTING, HICCUPPING, SNEEZING

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Brain Stem – The pons is located

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superior to the medulla and links the spinal cord to the brain and parts of the brain to each other. THINK BRIDGE FROM SPINAL CORD TO BRAIN

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The midbrain lies

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between and connects the pons to the diencephalon.

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Brain Stem – The midbrain is also known as

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the MESENCEPHALON

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Brain Stem – The midbrain prominent landmarks are:

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cerebral peduncles, tectum substantia nigra, red nuclei, medial lemniscus

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CEREBRAL PEDUNCLES are

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axons which conduct nerve impulses for MOTOR areas in the cerebral cortex to the spinal cord, medulla, and pons.

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TECTUM is

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four rounded elevations (BUMPS) containing reflex center for certain VISUAL and AUDITORY activities. (STARTLE REFLEX)

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SUBSTANTIA NIGRA are

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darkly pigmented nuclei beneath the cerebral peduncles which produce DOPAMINE, a neurotransmitter that controls subconscious muscle activity.

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RED NUCLEI are

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two nuclei with rich blood supply and iron-containing pigment within the neuronal somas. They are involved in COORDINATED muscular movements.

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MEDIAL LEMNISCUS (BROWN WAVY OUTSIDE THE RED NUCLEUS) are

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band of axons that conduct sensory impulses from the medulla to the thalamus. CSF RUNS THROUGH THE AQUADUCT OF THE BRAIN

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Diencephalon - The thalamus is located

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superior to the MIDBRAIN.

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Diencephalon – the thalamus contains

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nuclei that serve as RELAY STATIONS for all sensory impulses to the cerebral cortex.

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Diencephalon – The thalamus relays all sensory impulses except

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The sense of SMELL is an exception. THALMUS IS A RETICULAR ACTIVATING SYSTEM – sound of FIRE ALARM WAKES YOU UP – NOT SMELL OF SMOKE

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Diencephalon - The hypothalamus is located

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INFERIOR to the thalamus.

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The most important functions of the hypothalamus are:

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Control of AUTONOMIC nervous system. (SMOOTH MUSCLE), Regulating the PITUATARY gland, Regulate EMOTIONAL and BEHAVIORAL patterns, Regulation of eating and drinking, Maintaining a normal body TEMPERATURE, Maintaining BIOLOGICAL RHYTHMS

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The hypothalamus Regulates EMOTIONAL and BEHAVIORAL patterns together with the

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LIMBIC system. Aka (EMOTIONAL BRAIN)

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Diencephalon - The hypothalamus regulates thirst through the

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THIRST center.

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Diencephalon - The hypothalamus regulates eating through two centers

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feeding and satiety centers

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Diencephalon - The hypothalamus - FEEDING center is responsible for

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hunger sensations.

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Diencephalon - The hypothalamus- the SATIETY center is responsible for

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inhibiting the feeding center when sufficient food has been ingested.

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Diencephalon - The hypothalamus - The satiety center can be overridden by

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VOLUNTARY impulses from the cerebral cortex.

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Diencephalon - The hypothalamus - FEVERS PRODUCE TOXINS THAT

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ATTACK THE HYPOTHALMUS

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Diencephalon - The hypothalamus responsible for Maintaining BIOLOGICAL RHYTHMS as well as

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states of consciousness.

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Diencephalon - The epithalamus is located

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in the roof of the third ventricle

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Diencephalon - The epithalamus includes the:

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coroplexuses, and the pineal gland

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Diencephalon - The epithalamus COROPLEXUSES are responsible for

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EXCHANGE OF CSF

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Diencephalon - The epithalamus PINEAL GLAND is

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about the size of a small pea which protrudes from the dorsal midline of the third ventricle.

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Diencephalon - The epithalamus PINEAL GLAND secretes

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the hormone MELATONIN and is thought to be responsible for the body’s CIRCADIAN RHYTHMS. (sleep patterns)

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Cerebellum - is separated cerebrum by tentorium cerebelli which fills

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the transverse fissure between the cerebellum and the cerebrum.

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Cerebellum - is attached to brain stem by three paired peduncles which conduct

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AFFERENT INCOMING/SENSORY and EFFERENT impulses between cerebellum and other parts of brain.

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Cerebellum – peduncle 1 INFERIOR cerebellar peduncle carries

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SENSORY information from vestibular apparatus of inner ear and proprioceptors throughout the body.

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Cerebellum – peduncle 2 MIDDLE cerebellar peduncle carries

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MOTOR impulses for voluntary movements.

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Cerebellum – peduncle 3 SUPERIOR cerebellar peduncle contains

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axons which extend from cerebellum to red nuclei of midbrain and thalamus.

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The cerebellum is composed of:

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outer cortex and two hemispheres

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Cerebellum – the outer cortex of GRAY matter has

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an inner tree-like arrangement of WHITE matter tracts called the ARBOR VITAE

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Where is the arbor vitae located

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inside the gray matter of the outer cortex in the tree like arrangement of white matter

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Cerebellum – the Two hemispheres of the cerebellum have deep fissures and slender ridges called

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FOLIA

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Cerebellum – the Two hemispheres of the cerebellum are joined by the

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VERMIS.

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The cerebellum functions in coordination of

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the skeletal muscles, maintenance of normal muscle tone, and responses to changes in body EQUILIBRIUM. DANCING SPEAKING CATCHING BASEBALL

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Damage to the cerebellum results in

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symptoms involving the SAME SIDE of the body

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Cerebellum - there is NO crossing of tracts

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within the cerebellum.

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ATOXIA IS DAMAGE TO

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THE CEREBELLUM – CANNOT TOUCH FINGER TO NOSE, SPEECH PATTERN CHANGES,

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Cerebrum is

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LARGEST PART OF THE BRAIN

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Cerebrum - The surface is called

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the CEREBRAL CORTEX

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Cerebrum – cerebral cortex is

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about 3mm thick and is made of GRAY matter.

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Cerebrum – cerebral cortex contains

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billions of cells, usually in six layers of CELL BODIES – AS we AGE CELLS SHRINK

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Cerebrum – The cortex contains:

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Folds called GYRI/GYRUS, Deep FISSURES, Shallow SULCUS/SULCI

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The cerebrum is separated

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into right and left halves, HEMISPHERES,

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The cerebrum is separated by

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the LONGITUDINAL FISSURE.

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The cerebrum - CORPUS CALLOSUM are

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a massive bundle of transverse white fibers that connect the hemispheres internally

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The cerebral WHITE matter lies beneath

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the cerebral cortex.

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The cerebral WHITE matter tracts connect

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various parts of the brain and other parts of the nervous system.

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Cerebrum – ASSOCIATION tracts conduct

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nerve impulses between the gyri within the SAME hemisphere.

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Cerebrum – COMMISURAL tracts conduct nerve impulses from the gyri of one cerebral hemisphere to

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corresponding gyri of the OPPOSITE cerebral hemisphere via the corpus callosum.

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Cerebrum – PROJECTION tracts conduct

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nerve impulses between the cerebrum and lower parts of the CNS including the thalamus, brainstem, or spinal cord.

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Cerebrum – Each cerebral hemisphere is divided into

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4 lobes by sulci or fissures.

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Cerebrum –The 4 lobes of each hemisphere are:

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FRONTAL lobe, PARIETAL lobe, TEMPORAL lobe, OCCIPITAL lobe.

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Cerebrum – The fifth part of the cerebrum is

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the INSULA

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Cerebrum – The insula lies

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beneath the parietal and temporal lobes and cannot be seen from the brain’s surface.

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Cerebrum – the paired, curled masses of gray matter deep within the cerebral hemispheres are

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The BASAL GANGLIA (basal nuclei)

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Cerebrum – the basal ganglia function to

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regulate the initiation and termination of body movements, memory, and planning.

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Cerebrum – the basal ganglia help to

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control SUBCONCIOUS contractions of skeletal muscles. MOVING ARMS WHILE WALKNG, CAN ANTICIPATE MOVEMENT, WORK WITH LIMBIC SYSTEM FOR BEHAVIOR, OCD,

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Cerebrum – DISORDERS INVOLVING BASAL GANGLIA

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PARKINSONS, HUNTINGTONS, TERRETS, OCD,

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Cerebrum – The LIMBIC SYSTEM is found in

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the cerebral hemispheres and diencephalon.

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Cerebrum – The LIMBIC SYSTEM functions with the hypothalamus in processing

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EMOTIONAL information and MEMORY.

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The AMYGDALA is found in

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the limbic system PAIN PLEASURE DOCILITY – FIGHT, FLEE, FEED, FORNICATION

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Cerebrum – The cerebral cortex may be broken down into

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areas associated with specific functions of the body (functional areas).

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Cerebrum – There are 3 types of functional areas:

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sensory, motor & association

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Cerebrum – SENSORY function areas

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interpret sensory impulses and establish PERCEPTION

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Cerebrum – MOTOR function areas

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control VOLUNTARY muscular movement.

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Cerebrum – ASSOCIATION function areas

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influence emotional and complex integrative functions. INTELLIGENCE, WILL,

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Cerebrum – Brain lateralization implies that the brain is

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not symmetrical in FUNCTION

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Cerebrum – brain lateralization - The LEFT hemisphere is

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important in spoken and written language, reasoning, numerical and scientific skills.

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Cerebrum – brain lateralization - The RIGHT hemisphere is

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important in musical and artistic awareness, spatial and pattern perception, recognition of faces and emotional content of language, insight, imagination, and mental images.

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Cerebrum – Brain cells generate electrical energy called

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BRAIN WAVES.

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Cerebrum – brain wave impulses can

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be picked up and recorded on a device called an ECHOENCEPHALOGRAM (EEG).

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Cerebrum – brain waves - EEG recordings are used

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in the diagnosis and treatment of brain disorders. (USED MONITOR SEIZURES)

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Cranial Nerves - There are 12 pairs of cranial nerves designated by

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name and Roman numerals ex. optic nerve or CN II. NAMED ANTERIOR TO POSTERIOR

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Cranial Nerves - There are 3 types of cranial nerves:

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sensory, motor, mixed

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Cranial Nerves - Sensory only nerves are:

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cn i, cn ii, cn viii

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Cranial Nerves – Sensory nerves - OLFACTORY (CN I) responsible for

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olfaction or smell.

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Cranial Nerves – Sensory nerves - OPTIC (CN II) responsible for

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vision or sight. BLINDSPOT WHERE NERVE ENTERS BACK OF EYE

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Cranial Nerves – Sensory nerves - VESTIBULOCOCHLEAR (CN VIII) responsible for

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auditory and equilibrium.

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Cranial Nerves – Sensory nerves – Vestibulocochlear has two branches

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vestibular and cochlear.

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Cranial Nerves – Sensory nerves - VESTIBULAR branch carries

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impulses for equilibrium.

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Cranial Nerves – Sensory nerves - COCHLEAR branch carries

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impulses for hearing.

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Cranial Nerves – Motor only nerves are:

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cniii, cn iv, cn vi, cn xi, cnxii,

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Cranial Nerves – Motor only nerves (CN III) is

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OCULARMOTOR—movement of eye (superior rectus, medial rectus, inferior recuts, and inferior oblique muscles), iris, lens, and eyelid.

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Cranial Nerves – Motor only nerves (CN IV) is

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(TROCHLEAR)—movement of the eye (superior oblique muscle).

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Cranial Nerves – Motor only nerves (CN VI) is

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ABDUCENS—movement of the eye (lateral rectus muscle).

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Cranial Nerves – Motor only nerves (CN XI) is

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ACCESSORY NERVE—swallowing and movement of the head and pectoral girdle. MOVES HEAD FRONT BACK AND UP &DOWN

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Cranial Nerves – Motor only nerves (CN XII) is

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HYPOGLOSSAL—movement of tongue for speech and manipulation of food, and swallowing.

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Cranial Nerves – Mixed are

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sensory and motor fibers:

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Cranial Nerves – Mixed – identify mixed nerves

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cn v, cn vii, cn ix, cn x

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Cranial Nerves – Mixed – (CN V)

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TRIGEMINAL—ophthalmic, maxillary, and mandible. Sensory—input from touch, pain, and thermal sensations of the scalp, face, eyelid, cornea, forehead, and oral cavity Motor—chewing motions.

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Cranial Nerves – Mixed – (CN VII)

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FACIAL— INNERVATES MORE MUSCLES IN THE BODY THAN ANY OTHER NERVE Sensory—sensations from taste of the anterior two-thirds of the tongue and touch, pain, and thermal sensations from skin in external ear canal. Motor—movement of facial muscles and secretion of tears. (BELLS PALSY)

Front 144

Cranial Nerves – Mixed – (CN IX)

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GLOSSOPHARYNGEAL Sensory—taste of the posterior one-third of the tongue; monitors blood pressure and oxygen and carbon dioxide levels in blood; touch, pain, and thermal sensations from skin of external ear and upper pharynx. Motor—assists in swallowing and secretion of saliva.

Front 145

Cranial Nerves – Mixed – (CN X)

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VAGUS (WANDERING OR VAGRANT)— MEDULA OBLONGATA Sensory—taste from epiglottis; monitors blood pressure and oxygen and carbon dioxide levels in the blood; touch, pain, and thermal sensations from skin of external ear; sensations from thoracic and abdominal organs. Motor—swallowing, vocalization and coughing, motility and secretion of gastrointestinal organs and glands; constriction of respiratory passageways and decreases heart rate.

Front 146

Homeostatic Imbalances - ATTENTION DEFICIT HYPER disorder (ADHD) is

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a learning disorder characterized by an individual that has difficulty finishing tasks and has a short attention span. There is a strong genetic link and imaging demonstrated that individuals with ADHD have less nervous tissue in certain areas of the brain.

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Homeostatic Imbalances - EPILEPSY results from

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irregular electrical discharges within the brain. Depending upon the form of the disease, epileptics experience degrees of motor, sensory, or psychological malfunction. Most forms of epilepsy can be controlled by drugs such as lithium and Dilantin.

Front 148

Homeostatic Imbalances - A cerebrovascular accident (CVA), or STROKE involves

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brain tissue destruction (infarction) due to hemorrhage, embolism, or atherosclerosis. The degree of impairment depends upon the degree of tissue destruction. Risk factors are age, tobacco abuse, high BP, obesity, and alcoholism.

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PARKINSON’S disease results from

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decreased DOPAMINE production in the brain. The disease is characterized by involuntary tremors which progressively become worse until the individual becomes rigid. It is treated with L-dopa, a dopamine precursor. The dopamine molecule, which can be commercially synthesized, is too large to cross the blood-brain barrier.

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Homeostatic Imbalances - ALZHEIMER’S disease is

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a progressively disabling disorder of the elderly that involves intellectual and physical impairment as well as personality changes. Etiology is unknown although a combination of GENETIC factors and ENVIRONMENTAL factors may be contributing factors. The brains of Alzheimer's patients are characterized by DESTRUCTION of the cerebral cortex with a loss of neurons, neurofibrillary tangles, and plaques containing protein. The disease is terminal.