Chapter 15: Brain and Cranial Nerves

cerebral aqueduct

A canal called the ___________________ ___________________ passes down the core of the midbrain and leads to the fourth ventricle.

Reticular formation

A loosely organized web of gray matter that runs through all levels of the brainstem and has connections with many areas of the cerebrum. Consists of more than 100 small neural networks.

mnemonic

A memory-aiding phrase to help you remember anatomy names and terms (like the order of cranial nerves) is called a ____________________.

Third ventricle

A narrow median space inferior to the corpus callosum.

central (periaqueductal) gray matter

A region of gray matter surrounding the aqueduct, functions with the reticular formation in controlling our awareness of pain.

Fourth ventricle

A small triangular chamber between the pons and cerebellum . Caudally, this space narrows and forms a central canal that extends through the medulla oblongata into the spinal cord.

Arachnoid mater

A transparent membrane over the brain surface.

Longitudinal fissure

A very deep groove that separates the right and left hemispheres.

midbrain

After embryonic development is complete, the mesencephalon will inly develop into the

deep nuclei

All cerebellar input goes to the cortex and all output comes from the

amedian aperature and two lateral aperatures

All of the CSF escapes through three pores in the walls of the fourth ventricle:

Optic Oculomotor Trochlear Abducens

All of the following begin or end in the orbit:

CVOs

Allow brain to monitor blood chemistry

Buoyancy

Allows the brain to attain considerable size without being impaired by its own weight.

Cerebellum

Although it is only 10% of the mass of the brain, it has about 60% as much surface area as the cerebral cortex and contains more than half of all brain neurons (about 100 billion).

oxygen and glucose

Although the brain constitutes only 2% of the adult body weight, it receives about 15% of the blood and consumes 20% of the

Cerbral crura

Anchor cerebrum to the brainstem.

pyramids (separated by anterior median fissure)

Anterior surface of medulla bears a pair of club like ridges, the

association cortex

Areas of cerebral cortex that identify or interpret sensory information are called

ependymal cells joined by tight junctions

At the choroid plexuses, there is a simialr blood-CSF barrier composed of

hypothalamus

Because of a brain lesion, a certain patient never feels full, but eats excessively that she now weighs nearly 600 pounds. The lesion is most likely in her

The choroid plexuses produce

CSF

40% in the subarachnoid space 30% by ependymal lining of ventricles 30% by choroid plexuses

CSF formation

arachnoid granulations (cauliflower like extensions of the arachnoid meninx that protrude through the dura mater into the superior sagittal sinus of the brain).

CSF is absorbed from the subarachnoid space by

heartbeat

CSF is driven by its own pressure, by beating of the cilia on the ependymal cells, and by rhythmic pulsations of the brain produced by each

Lateral ventricle to interventricular foramina to Third ventricle to Cerebral aqueduct to Fourth ventricle

CSF is secreted in the

1. Buoyancy 2. Protection 3. Chemical stability

CSF serves three purposes:

toward the spinal cord (tail)

Caudal means

foramen magnum of the skull

Caudally, the brainstem ends at the

arbor vitae

Cerebellum has a surface cortex of gray matter and a deeper layer of white matter. A branching fernlike pattern in the white matter is called the

cerebellar peduncles (2 inferior connect it to the medulla, two middle to the pons, and 2 superior to the midbrain).

Cerebellum is connected to the brainstem by three pairs of stalks called

choroid plexus

Cerebrospinal fluid is secreted partly by a mass of blood capillaries called the ______________________ in each ventricle.

VIII to XII

Collectively the cranial nerves _____________________ include touch, pressure, temperature, taste, hearing, and pain.

Frontal lobe

Concerned with cognition (thought), and other higher mental processes, speech, and motor control.

Vagus nerve CN V

Controls cardiac, pulmonary, digestive and urinary functions.

Abducens nerve CN VI

Controls lateral movement of the eye.

Oculomotor nerve CN III

Controls movement of the eye, constriction of the pupil and focusing.

Hypoglossal nerve CN XII

Controls movement of the tongue and swallowing.

Accessory nerve CN XI

Controls swallowing and movements of the head, neck and shoulders.

Glossopharyngeal nerve CN IX

Controls the secretion of the salivary glands and swallowing. Also, transmits taste, touch, pressure and pain sensations from the tongue.

pons

Cranial nerve V through VIII begin or end in the

midbrain

Cranial nerves III and IV both concerned with eye movements, originate in the

medulla oblongata

Cranial nerves VIII, IX, X, and XII begin or end in the

receptors

Cranial nerves that convey sensory patterns originate in

brainstem

Cranial nerves that convey sensory patterns terminate in the

Commissural tracts

Cross from one cerebral hemisphere to the other through bridges called commissures. Corpus callosum

abducens

Damage to the ________________ nerve could result in defect of eye movement.

Substantia nigra (suppresses unwanted muscle contractions)

Dark gray to black nucleus pigmented with melanin, located between the tegmentum and cerebral crura.

white matter

Deeper masses called nuclei are surrounded by

Toward the nose, toward the forehead, or higher (vertical).

Define the term rostral.

Parkinson's disease

Degeneration of the substantia nigra leads to uncontrollable muscle tremors of

mesencephalon or midbrain

During embryonic development, the midbrain does not divide and retains the name

folia

Each hemisphere of the cerebellum exhibits slender, parallel folds called

thalamus, hypothalamus, epithalamus (these structures surround the third ventricles of the brain)

Embryonic diencephalon has three major derivatives:

myelencephalon and metencephalon

Embryonic hindbrain differentiates into two subdivisions, the

midbrain, a short segment of the brainstem that connects the hindbrain and forebrain

Embryonic mesencephalon produces the

cerebrum (largest part of the brain)

Embryonic telencephalon becomes the

Medial group

Emotional output to prefrontal cortex; awareness of emotions.

brianstem.

Even though the cerebellum is part of the metencephalon, it is not part of the

Tectum

Exhibits four bulges called the corpora quadrigemina. Rostral pair = superior colliculi. Caudal pair = inferior colliculi (Aid in locating the source of a sound in space), auditory reflexes, startle response to a loud noisem

falx cerebri

Extends into the longitudinal fissure as a vertical wall between the right and left cerebral hemispheres, and is shaped like the blade of a sickle.

ventricles

Fluid-filled internal chambers of the brain are called ________________________.

diencephalon and cerebrum

Forebrain consists of the

Hypothalamus

Forms part of the walls and floor of the third ventricle.

temporal lobe

Hearing is associated mainly with the

Temoral lobe

Hearing, smell, learning, memory, and some aspects of emotion.

corpus callosum

Hemispheres are connected by a thick bundle of nerve fibers called

BBB

Highly permeable to water; glucose; lipid-soluble substances such as oxygen and carbon dioxide; and drugs such as alcohol, caffeine, nicotine, and anesthetics

Two

How many cerebral hemispheres are there?

Four

How many ventricles are located in the brain?

Hormone secretion Autonomic effects Thermoregulation Food and water intake Sleep and circadian rhythms Emotional and sexual responses Memory

Hypothalamus functions:

-Atrophy of cerebral gyri. -Abundant neurofibrillary tangles. -Atrophy of the hippocampus. -Abundant senile plaques.

Identify some of the key histological and gross anatomical features seen in autopsied brains of Alzheimer's Disease victims.

arbor vitae

In a sagittal section, the cerebellar white matter exhibits a branching pattern called the

1,600 g (3.5 pounds)

In men the brain weighs about

white

In the brain and spinal cord, tracts are located within the ___________________ matter.

1,450 g

In women the brain weighs about

Pia mater

Is a very thin, delicate membrane that closely follows all contours of the brain surface, even dipping into the sulci. Usually not visible without a microscope.

Cerebellum

Is the second largest region of the brain, constituting about 10% of the brain's volume but contains over 50% of its neurons.

Cerebellum

Largest part of the hindbrain and second largest part of the brain as a whole. Consists of right and left cerebellar hemispheres connected by a narrow wormlike bridge, the vermis.

olive

Lateral to each pyramid is a prominent bulge called the

Cerebellum

Lies inferior to the cerebrum in the posterior cranial fossa, and is separated from the cerebrum by the transverse cerebral fissure.

categorical

Linear, analytical, and verbal thinking occurs in the ___________________ hemisphere of the cerebrum, which is on the left in most people.

Cerbellum

Main role is subconscious evaluation of diverse kinds of sensory input; monitoring the movements of muscles is only part of that role.

diencephalon, midbrain, pons, medulla oblongata

Major components of brainstem from rostral to caudal:

Hypothalamus

Major control center for the ANS and endocrine system plays an essential role in homeostatic regulation of nearly all organs.

Alzheimer's disease

Memory loss associated with atrophy of the hippocampus and lowered levels of acetylcholine is one of the first symptoms exhibited in

pons and cerebellum

Metencephalon develops into the

Meninges

Name the connective tissue membranes surrounding the brain and spinal cord.

vision, memory, cognition, and motor control of prehensile hand

Over the course of human evolution, the brain has shown its greatest growth in areas concerned with

Anterior group

Part of limbic system; memory and emotion

hippocampus

Part of the limbic system is involved in forming new memories in the

vertical falx cerebri

Partially separates the right and left halves of the cerebellum on the inferior side.

Insula

Plays roles in taste, visceral sensation, and understanding spoken language.

peduncles, that attach it to the cerebellum

Posteriorly, the pons consists of two pairs of thick stalks called

Facial nerve CN VII.

Primary nerve that controls the facial muscles.

Trigeminal nerve CN V

Primary nerve that transmits sensory information from the face.

Parietal lobe

Primary site fro receiving and interpreting signals of the general senses; taste (a special sense); and some visual processing.

Occipital lobe

Principal visual center of brain.

Inferior colliculi

Receive and process auditory input from lower levels of the brainstem and relay it to other parts of the brain,e specially the thalamus.

Thalamus

Relays cerebellar signals to the cerebral cortex so that the cerebrum can male fine adjustments in muscle performance.

Somatic motor control Cardiovascular control Pain modulation Sleep and consciousness Habituation

Reticular formation functions:

toward the forehead (nose)

Rostral means

Cerebrum

Seat of sensory perception, voluntary motor actions, memory, and mental processes such as thought, judgement, and imagination (which distinguishes humans from other animals).

subarachnoid space

Separates the arachnoid from the pia.

Subdural space

Separates the dura from the arachnoid.

Sulci

Shallow grooves

Gray matter

Site of neurosomas, dendrites, and synapses forms a surface layer called the cortex over the cerebrum and cerebellum.

Lateral group

Somatosensory output to association areas of cortex; contributes to emotional function of limbic system

Ventral group

Somatosensory output to postcentral gyrus; signals from cerebellum and basal nuclei to motor areas of cortex.

Cerebral gyri are narrower. More space between the brain and the meninges. Thinner cerebral cortex. Cerebral sulci are wider.

Some of the gross anatomical changes seen in the aged brain include

tentorium cerebeli

Stretches horizontally like a roof over the posterior cranial fossa and separates the cerebellum form the overlying cerebrum.

23 nuclei Anterior Medial Ventral Lateral Posterior

Thalamus is composed of at least

circumventricular organs (CVOs) on the walls of the third and fourth ventricles

The BBB is absent from patches called

pons

The ______________ is most closely associated with the cerebellum in embryonic development and retains its primary source of input fibers throughout life.

ependymal cells

The blood-CSF barrier is formed by

30

The brain attains its peak development and efficiency around age ____________.

ventricles, cerberospinal

The brain has four chambers called ____________________ filled with _________________________ fluid.

ventricles

The brain has four internal chambers called

Cerebrum (83% of brain's volume) Cerebellum Brainstem (crucial for survival)

The brain is divided into three major portions:

500 mL CSF

The brain produces about _________________ of CSF per day, but the fluid is constantly reabsorbed at the same rate and only 100 to 160 mL is present at one time.

ignore repetitive inconsequential stimuli while remaining sensitive to others.

The brain stem's reticular activating system functions primarily to

midbrain

The cerebral aqueduct (channel connecting third and fourth ventricle) passes through the

cerebral hemispheres

The cerebrum has a pair of half globes called

Taste Equilibrium Vision Smell Hearing

The classification of "special senses" includes

thalamus

The diencephalon structure that is located on each side of the brain at the rostral end of the brainstem beneath the cerebral hemispheres is the

thalamus

The diencephalon structure that is located on each side of the brain at the rostral end of the brainstem is the ____________________.

Temporal lobe Occipital lobe Midbrain tectum Trochlear nerve

The following are involved in vision:

lateral ventricles, which form an arch in each cerebral hemisphere

The largest are the two

cardiac center vasomotor center Two respiratory centers

The medulla contains several nuclei concerned with basic physiological functions:

foramen magnum

The medulla oblongata begins at the ____________________ ___________________ and extends approximately 3 cm rostrally.

Broca area

The motor pattern for speech is generated in an area of cortex called the _________________ and then transmitted to the primary motor cortex to be carried out.

medulla oblongata

The myelencephalon gives rise to one structure, the

ascending sensory and descending motor

The nerve fibers connecting the brain to the spinal cord passing through the medulla are

Sleep, respiration and bladder control

The pons contains several nuclei involved in basic physiological functions including:

gracile and cuneate fasciculi, a continuation of the ones in the spinal cord

The posterior surface of the medulla exhibits two pairs of ridges, the

regulate passage of materials from the blood into the CSF and the brain.

The primary function of the blood brain barrier is to

precentral

The primary motor area of the cerebrum is the _______________________ gyrus of the frontal lobe.

corpus callosum

The prominent C-shaped band of nerve tracts that connect the right and left cerebral hemispheres to each other is referred to as the

descending corticospinal fibers

The pyramids of the medulla oblongata contain

corpus callosum

The right and left cerebral hemispheres are connected to each other by a thick C- shaped bundle of fibers called the

Brainstem

The smallest of the three major parts and most crucial for survival.

Commissural (structure is corpus callosum).

The structure indicated by the letter A is comprised of what kind of white matter tracts?

blood brain barrier

The structure that regulates the passage of materials from the blood into the cerebrospinal fluid and the brain is referred to as the

reticular activating

The system that consists of reticular formation nuclei that modulate activity of the cerebral cortex and functions to maintain consciousness is called the ____________________ _________________________ system or RAS.

meninges

The three-layer fibrous membranes surrounding the brain and spinal cord are collectively called the __________________________.

cortical gray matter

The white matter lies deep to the

tracts

The white matter of the brain and spinal cord contains __________________.

12

There are __________ pairs of cranial nerves.

Gyri

Thick folds

interventricular foramen

Through a pore called the ________________________ __________________, each lateral ventricle is connected to the third ventricle.

Vetsibulocochlear CN VIII

Transmits information for the sense of hearing and balance.

Optic nerve CN II

Transmits information for the sense of vision.

Olfactory nerve CN I

Transmits informations for the sense of smell.

medulla oblongata

Trigeminal nerve emerges from the pons, but its nucleus extends into the

True

True or False: By age 75, the average brains weigh slightly less than half what it did at age 30.

cranial nerves

Twelve pairs of nerves that arise from the base of the brain, exit through skull foramina, and lead to muscles and sensory organs primarily of the head and neck are classified as

rostral and caudal

Two directional terms often used to describe the brain anatomy are

Periosteal layer (outer) Meningeal layer (inner)

Two layers of dura mater

Superior sagittal sinus Transverse sinus

Two major dural sinuses are: (These meet like an inverted T in the back of the brain and empty into the internal jugular veins of the neck).

special

Vision, hearing, equilibrium, taste and smell, are limited to the head and require the sense organs and are classified as _____________________ senses.

arbor vitae

What is the arrow "B" pointing to?

Cranial nerves V to VIII begin or end in the pons.

Which cranial nerves emerge from the pons?

CN VI CN V CN VIII

Which of the following cranial nerves begin or end in the pons.

reticular activating system

While studying in a noisy cafeteria, you get sleepy and doze off for a few minutes. You awaken with a start and realize that all the cafeteria sounds have just come back. While you were dozing, this auditory input was blocked form reaching your auditory cortex by the

myelin

White color of the brain comes from

arbor vitae

White matter located in the deeper aspects of the cerebellum exhibiting a branching fern-like pattern is referred to as the

caudal; rostral

With regard to directional terms often used to describe brain anatomy, the term __________________ means toward the tail, while the term _____________________ means toward the nose.

frontal lobe

Your personality is determined mainly by which lobe of the cerebrum?

Ependymal cells

a type of neuroglia, cover each of the choroid plexus, the entire interior surface of the ventricles, and the canals of the brain and spinal cord.

mammilary bodies function

acquisition of new memories

Superior peduncles

carry most cerebellar output.

Middle peduncles

carry signals from the cerebrum about what the muscles were commanded to do.

CSF

clear, colorless liquid that fills the ventricles and canals of CNS and bathes its external surface.

dural sinuses

collect blood that has circulated through the brain.

Crura, tegmentum, and substantia nigra

collectively form the cerebral peduncle

Tegmentum (main mass of hindbrain)

contains the red nucleus, which collaborated in fine motor control

Anterolateral system

contains the spinothalamic tract en route to the thalamus, and the anterior spinocerebellar tract, carrying signals en route to the cerebellum.

Projection tracts

extend vertically between higher and lower brain and spinal cord centers and carry info between the cerebrum and the rest of the body.

Superior sagittal sinus

found just under the cranium along the midsagittal line

Superior colliculi

function in visual attention (peripheral vision).

The cerebral aqueduct

is caudal to the hypothalamus

Meninges (dura mater, arachnoid mater, pia mater)

lie between the nervous tissue and bone.

Choroid plexus

on the floor or wall of each ventricle, there is a spongy mass of blood capillaries

Posterior group

relay of visual signals to occipital lobe (via lateral geniculate nucleus) and auditory signals to temporal lobe (via medial geniculate nucleus)

CSF flow

rinses metabolic wastes from the nervous tissue and homeostatically regulates its chemical environment.

Transverse sinus

runs horizontally from the rear of the head toward each ear.

BBB (tight junctions between endothelial cells and the basement membrane)

seals nearly all the blood capillaries throughout the brain tissue

Cerbellum's

tiny, densely packed granule cells are the most abundant neurons in the entire brain. Its most distinctive neurons are the large purkinje cells.