The Nervous System 9.14 Brain

Zahraa A.Rima S

2nd hour

Content objective: SWD understanding of section 9.14 dealing with the human brain

Language objective: SWD understanding of the human brain by listening, taking notes, filling in work sheet, and participating in a game

NOTE: Worksheet will be collected and graded for 10 formative points

IntroductionComposition: The brain is made up of 100 billion multipolar neurons

Function: neurons communicate with each other and other neurons in various parts the nervous system

Division: 4 parts

1. The cerebrum2. The diencephalon3. The brain stem4. The cerebellum

1. The cerebrum: biggest partcomposition: includes nerve centers that deal with sensory and motor functions. Its also provides higher mental functions

ex: memory and reasoning

2. The diencephalon: process sensory information

3. The brain stem: contains nerve pathways that connect different parts of the nervous system,and control specific visceral activities

4. The cerebellum: includes centers that coordinate voluntary muscular movements

Structure of the CerebrumComposition of the cerebrum:

1. Cerebral hemispheres: 2 large masses refers to a the left and right cerebral hemispheres

2. corpus callosum: a deep bridge of nerves that connect the cerebral hemispheres

3. dura mater: Thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord

4. gyri: ridges located on the surface of the cerebrum, composed of single gyrus separated by grooves

A.) sulcus: shallow groove

B.) fissure: deep groove

1. Longitudinal fissure:deep groove that separates the left and right cerebral hemisphere

2. Transverse fissure:deep groove that separates the cerebrum from the cerebellum

sulci divides each hemisphere into lobes

Examples of distinct patterns formed in brain

Lobes of the cerebral hemispherelobes name is based on the bone the underlie

1. Frontal lobe: forms the anterior portion of each cerebral hemisphere. Its posteriorly bordered by the central sulcus. The central sulcus extends from the lateral fissure at a right angle. It inferiorly extends by a lateral sulcus which extends from under the brain's surface along its sides

2. Parietal lobe: located behind the frontal lobe and is separated by the central sulcus

3. Temporal lobe: located under the frontal and parietal lobe and is separated by the central sulcus

4. Occipital lobe : forms the lower part of each cerebral hemisphere and is separated from the cerebellum by a shelf like extension of dura mater.

5. Insula: located deep within the lateral sulcus and is covered by portions of frontal, parietal, and temporal lobes. Insula is separated from other lobes by a circular sulcus.

Lobe overview

Cerebral cortexCerebral cortex: thin layer of grey matter located on the outer most portion of the cerebrum.

A. The layer covers the gyri and it dips into the sulci and fissures.

B. It contains 75% of neuron cells bodies in the nervous system

White matterWhite matter: composed of bundles of myelinated axons located under the cerebral cortex.

A. This matter connects neuron cell bodies of the cortex with other parts of the nervous system

B. makes up the mass of the cerebrum.C. Some the fibers pass from one cerebral

hemisphere to another by the way of the corpus callosum

D. Other fibers also carry sensory or motor impulses from parts of the cortex to nerve centers in the brain or spine

Functions of the CerebrumThe cerebrum:

1. Provides higher functions of the brain2. Contains centers for interpreting(viewing) sensory impulses coming from

sense organs.3. contains centers for starting voluntary muscular movement.4. stores information that make up memories used for reasoning5. Activity originates (forms) intelligence & personality

Functional Regions of the Cerebral Cortex

1. Motor area: a. part of cerebral cortex, found in frontal lobes. b. Type of nerve tissue: pyramidal cells/ upper motor neurons = Signal =>

lower motor neurons. c. Axons crisscross along the two hemisphere of the brain. (that’s why the

left side of brain controls the right side of body).d. Ex: Frontal eye field - eye and eyelid, voluntary movement.e. Other part control hand and finger movement.

Functional Regions of the Cerebral Cortex

2. Sensory area:

Responsible for feelings and sensation by interpreting impulses. Like the motor fibers, the right side is controlled by the left hemisphere and vise versa.

Interpretes the 5 senses:

● Cutaneous ● Visual ● Auditory ● Taste● Smell

Functional Regions of the Cerebral Cortex3. Association areas:

a. Processing unit- memory, emotions, perception, cognition, etc.. b. Located at the anterior of frontal lobes, in lateral area of parietal,

temporal, occipital lobes.c. Helps with planning, solving, speech, expressing of emotion.d. Language and speech: (left hemisphere)

i. Sensory speech area/ Wernicke’s area. (parietal lobe)ii. Motor speech area/ Broca’s area. (frontal lobe)

e. Recognition and memory- one or more sensory areas are used to create patterns. (ex: smelling a certain food, and imagining it visually, or tasting it)

Hemisphere Dominance● In most people, dominant hemisphere is a side of the cerebrum that controls

understanding and using language. (usually left, some people have right dominance, and some have both).

● Non dominant hemisphere would control nonverbal communication (body language), musical and visual patterns, and emotions.

● The two are connected by nerve fibers of corpus callosum. They allow communication between, transfer of info. Dominant controls non dominant, and nondominant sends info to dominant to make decisions.

Hemisphere Dominance● Basal nuclei: masses of gray

matter, the caudate nucleus, the

putamen, and the globus

pallidus. ‘relay stations’ for

motor impulses, or modify their

pattern which helps conscious

muscle movement. Respond to

dopamine (inhibitor).

Ventricles in the brain are cavities filled cerbronspinsol fluid

Ventricles & Cerebrospinal FluidVentricles

1. Series of interconnected cavities located within the cerebral hemispheres and brainstem.

A. Lateral ventricles 1. Is the largest ventricle, 2. extending into the cerebral hemispheres,3. taking over parts of the frontal, temporal, and occipital

lobes.B. Third ventricle

1. located in the midline of the brain under the corpus callosum.2. communicates with the lateral ventricles through openings in front of its

end

C. The fourth ventricle

1. Located in the brain stem, in front of the cerebellum.

D. Cerebral aqueduct

1. A narrow canal that connects the fourth ventricle to the third ventricle

2. Passes through the brainstem

E. The fourth ventricle continues with the central canal of the spine and contains openings in its roof leading to the subarachnoid space of the mennings.

Choroid plexuses and cerebrospinal fluidA. Choroid plexuses : Tiny, reddish, cauliflower like mass of specialized capillaries from the pia mater

B. Choroid plexuses projects into the ventricles & secretes cerebrospinal fluid

which is formed in the lateral ventricles

C. cerebrospinal fluid slowly circulates (flows) into the third and fourth ventricles and into the spinal cord's central canal.

D. Cerebrospinal fluid enters subarachnoid spaces of the mennings through the fourth ventricle wall near the cerebellum this causes the fluid to completely surround the brain and spinal cord.

E. organs (brain and spine) that float in the fluid are protected because the fluid absorbs any forces that could potentially damage the organs

F. It completes its circulation by being absorbed into the blood.

G. Cerebrospinal fluid maintains a stable ionic concentration in the central nervous system and also provides a path for wastes

DiencephalonDiencephalon: Between cerebral hemispheres and superior to the midbrain. Composed of gray matter.

● Thalamus: within Diencephalon. Receives all sensory impulses, and directs them to appropriate areas. Produces awareness of some sensations (temp., touch, pain)

● Hypothalamus: region of diencephalon, includes many nuclei (gray matter). Maintains homeostasis (by connecting nervous w/ endocrine system).

○ Heart rate & blood pressure○ Water & ion balance○ Hunger & body weight. + digestive system activities○ Production of neurosecretory molecules (regulate pituitary gland)○ Sleep cycle

Diencephalon● Limbic system: hypothalamus, thalamus, & basal nuclei. Controls actions

based on emotions. Sences dangerous physical & physiological conditions. Increase survivability by changing behavior based on mood.

Other parts of Diencephalon:

● Optic tracts & optic chiasma: formed from optic fibers crossing over.● Infundibulum : attaches pituitary gland.● Posterior pituitary gland: bottom of hypothalamus.● Mammillary bodies: behind infundibulum. ● Pineal gland: upper portion of diencephalon.

BrainstemA. Brainstem: bundle of nervous tissue that connects the cerebrum to the spinal

cord.

B. It contains an abundant track of nerve fibers and a few nuclei.

C. Parts of the brainstem include

1. The Midbrain

2. Pons

3. Medulla oblongata

1. MidbrainA. Midbrain: Small section of the brainstem

B. Located between the diencephalon and the pons.

C. It contains bundles of myelinated axons that bring together the lower part of the brainstem and spinal cord with higher parts of the brain

D. Corticospinal tracts: 2 bundles of axons, located on the underside of the midbrain. They function as the main motor pathways between the cerebellum and the lower part of the nervous system

Fun fact: the Corticospinal tracts carry voluntary impulses from the brain to your skeletal muscles

E. The midbrain include masses of grey matter that works as reflex centers.

Example #1: the midbrain has centers for specific visual reflexes that include

1. Centers responsible for moving your eyes to see something while your head turns

Example #2: the midbrain also has auditory reflex centers that include

1. Centers that you to move your head to hear sounds clearly.

Brainstem- PonsA. Rounded bulge

B. Located on the underside of the brainstem

C. It separates the midbrain from the medulla oblongata

D. The dorsal part of the pons mostly contains large longitudinal nerve fibers that rely on nerve impulses from and to the medulla oblongata and the cerebellum.

E. The ventral part of the pons has large bundles of transverse nerve fibers that transmit impulses from the cerebrum to centers in the cerebellum

Nuclei functions of pons

Some nuclei of the pons rely on sensory impulses from the peripheral nerves to higher brain centers.

Other nuclei function with center of the medulla oblongata to maintain a stable breathing rhythm.

Brainstem- Medulla OblongataA. Medulla oblongata: is Part of the brain stem, located between the pons and spinal cord.

1. Its dorsal (behind/lower) surface forms the floor of the fourth ventricle.

2. Its ventral (front) surface is marked by the crossing over of corticospinal tracts

B. Because of the location of the medulla oblongata the ascending(arising) and descending (plunging) nerve fibers that connect the brain and spine must pass through

A. white matter of the medulla oblongata surrounds a central mass of grey matter.

B. “Nerve fibers separate the grey matter into nuclei which then rely on ascending impulses to the other side of the brainstem and then onto higher brain centers” (book page 242)

C. Other nuclei of the medulla oblongata control important visceral (deep) activities including

1. Cardiac center2. Respiratory center3. Vasomotor center

Nuclei function within the medulla oblongata

The cardiac center: impulses that originate in the cardiac center are transmitted onto the heart on peripheral nerves changing heart rate.

1. The cardiac center

Respiratory center: adjusts the rate and depth rate of breathing by acting with the pons to keep a stable breathing rhythm

2. Respiratory center

3. Vasomotor centerVasomotor center : special cells initiate (begin) impulses that travel (move) to smoothe muscle in the walls blood vessels that stimulate them to contract.

A. Vasoconstriction: Blood pressure is raised due to constriction of blood vesicles

B. Vasodilation: Vasomotor center cells that produce dilating blood vessels causing blood pressure to drop.

Brainstem- Reticular FormationReticular formation: network of nerve fibers. From the top of the spinal cord to the diencephalon. Joins nerve fibers of major areas with the ascending & descending tracts. When it senses impulses, it ‘wakes up’ the cerebral cortex. (no activity in reticular formation = sleep).

When it’s damaged, a person becomes unconscious (comatose). Caused by severe accidents, or drugs that negatively affect CNS.

Brainstem- CerebellumCerebellum: found below occipital lobes, and posterior to pons.

Made of 2 hemispheres separated by layer of dura mater + connected by vermis. Mostly white matter, w/ some gray matter on surface → Cerebellar cortex.

Cerebellar peduncles - 3 pairs of nerve traces that helps cerebellum communicate w/ CNS.

1. Inferior peduncles- joints & limbs to cerebellum. 2. Middle peduncles- move signals from cerebral cortex to cerebellum.3. Superior peduncles- sends signals from cerebellum to midbrain.

Brainstem- Cerebellum

Cerebellum coordinates skeletal muscle movement + maintains posture.

If damaged, then tremors develop, inaccurate movement of muscles, losing muscle tone & equilibrium.

SummaryBrain is composed of 4 parts:

● The cerebrum: 4 lobes: Parietal, Temporal, Occipital, Insula lobe. (motor,

sensory, association areas)

● The diencephalon: Thalamus (Produces awareness), Hypothalamus

(maintain homeostasis).

● The brainstem: bundle of nervous tissue that connects the cerebrum to the

spinal cord. Has 3 parts: The Midbrain, Pons, Medulla oblongata

● The cerebellum: coordinates skeletal muscle movement & maintains posture

Class question! 1. What are the major 4 parts of the brain?

2. What are the 3 functions of the Cerebral Cortex?

3. What are two of the many functions of the Hypothalamus?

4. What are the 3 parts of the brainstem?

Brain review gameDirections: come up and label each empty part. If you get the answer correct you’ll get candy!Look on page 235 for reference

#1

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Word choices● Spinal cord● Corpus

callosum● Cerebellum● Diencephalon● Brainstem● Skull● Cerebrum● menings