The Nervous System: The Brain and Cranial Nerves AHS 101.

The Nervous System: The Brain and Cranial Nerves

AHS 101

Regions of the BrainRegions of the Brain

Slide 7.27Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Cerebral hemispheres

Diencephalon

Brain stem

CerebellumFigure 7.12

Protection of the Central Nervous Protection of the Central Nervous SystemSystem

Slide 7.44a

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Scalp and skin

Skull and vertebral column

Meninges

Figure 7.16a

Protection of the Central Nervous Protection of the Central Nervous SystemSystem

Slide 7.44b


Cerebrospinal fluid

Blood brain barrier

Figure 7.16a

MeningesMeninges


Dura mater

Double-layered external covering

Periosteum – attached to surface of the skull

Meningeal layer – outer covering of the brain

Layers separate in certain places to form large veins called dural sinuses

Folds inward in several areas

MeningesMeninges

Slide 7.45b


Arachnoid layer

Middle layer

Web-like

Pia mater

Internal layer

Clings to the surface of the brain

Cerebrospinal FluidCerebrospinal Fluid


Clear liquid similar to blood plasma composition

Formed by the choroid plexus

Forms a watery cushion to protect the brain

Circulated in arachnoid space, ventricles, and central canal of the spinal cord

Returns to blood via villi in the dural sinuses

Ventricles and Location of the Ventricles and Location of the Cerebrospinal FluidCerebrospinal Fluid

Slide 7.47a


Figure 7.17a

Ventricles and Location of the Ventricles and Location of the Cerebrospinal FluidCerebrospinal Fluid

Slide 7.47b


Figure 7.17b

Blood Brain BarrierBlood Brain Barrier


Includes the least permeable capillaries of the body

Excludes many potentially harmful substances

Useless against some substances Fats and fat soluble molecules Respiratory gases Alcohol Nicotine Anesthesia

Cerebral Hemispheres (Cerebrum)Cerebral Hemispheres (Cerebrum)

Slide 7.28a


Paired (left and right) superior parts of the brain

Include more than half of the brain mass

Figure 7.13a

Cerebral Hemispheres (Cerebrum)Cerebral Hemispheres (Cerebrum)

Slide 7.28b


The surface is made of ridges (gyri) and grooves (sulci)

Figure 7.13a

Lobes of the CerebrumLobes of the Cerebrum

Slide 7.29a


Fissures (deep grooves) divide the cerebrum into lobes

Surface lobes of the cerebrum

Frontal lobe

Parietal lobe

Occipital lobe

Temporal lobe

Lobes of the CerebrumLobes of the Cerebrum

Slide 7.29b


Figure 7.15a

Specialized Areas of the CerebrumSpecialized Areas of the Cerebrum


Somatic sensory area – receives impulses from the body’s sensory receptors

Primary motor area – sends impulses to skeletal muscles

Broca’s area – involved in our ability to speak

Sensory and Motor Areas of the Sensory and Motor Areas of the Cerebral CortexCerebral Cortex


Figure 7.14

Specialized Area of the CerebrumSpecialized Area of the Cerebrum

Slide 7.32a


Cerebral areas involved in special senses

Gustatory area (taste)

Visual area

Auditory area

Olfactory area


Slide 7.32b


Interpretation areas of the cerebrum

Speech/language region

Language comprehension region

General interpretation area


Slide 7.32c


Figure 7.13c

Memory and Learning

• Short-term memory• Retention of information for few seconds or

minutes• Information lost unless reinforced

• Long-term memory• Storage of information that can be recalled

later

DiencephalonDiencephalon

Slide 7.34a


Sits on top of the brain stem

Enclosed by the cerebral hemispheres

Made of three parts Thalamus

Hypothalamus

Epithalamus

DiencephalonDiencephalon

Slide 7.34b


Figure 7.15

ThalamusThalamus


Surrounds the third ventricle

The relay station for sensory impulses

Transfers impulses to the correct part of the cortex for localization and interpretation

HypothalamusHypothalamus

Slide 7.36a


Under the thalamus

Important autonomic nervous system center Helps regulate body temperature

Controls water balance

Regulates metabolism

HypothalamusHypothalamus

Slide 7.36b


An important part of the limbic system (emotions)

The pituitary gland is attached to the hypothalamus

EpithalamusEpithalamus


Forms the roof of the third ventricle

Houses the pineal body (an endocrine gland)

Includes the choroid plexus – forms cerebrospinal fluid

Brain StemBrain Stem

Slide 7.38a


Attaches to the spinal cord

Parts of the brain stem Midbrain

Pons

Medulla oblongata

Brain StemBrain Stem

Slide 7.38b


Figure 7.15a

MidbrainMidbrain


Mostly composed of tracts of nerve fibers

Has two bulging fiber tracts – cerebral peduncles

Has four rounded protrusions – corpora quadrigemina

Reflex centers for vision and hearing

Cranial nerves III and IV originate from the midbrain

PonsPons


The bulging center part of the brain stem between the midbrain and medulla

Mostly composed of fiber tracts that carry impulses between the cerebellum and the rest of the nervous system

Includes nuclei involved in the control of breathing

Medulla OblongataMedulla Oblongata


The lowest part of the brain stem Merges into the spinal cord Includes important fiber tracts Contains important control centers

Heart rate control Blood pressure regulation Breathing Swallowing Vomiting

Medulla Oblongata

• Motor fibers from motor cortex extend through the medulla and most cross from one side to the other.– Results in contralateral control– Right hemisphere controls muscles in the left

side of the body– Left hemisphere controls muscles in the right

side of the body

CerebellumCerebellum

Slide 7.43a


Two hemispheres with convoluted surfaces

Provides involuntary coordination of body movements

Helps maintain balance in standing, walking and sitting

Helps maintain muscle tone

CerebellumCerebellum

Slide 7.43b


Figure 7.15a

Cranial NervesCranial Nerves


12 pairs of nerves that mostly serve the head and neck

Numbered in order, front to back

Most are mixed nerves, but three are sensory only

Distribution of Cranial NervesDistribution of Cranial Nerves


Figure 7.21



I Olfactory nerve – sensory for smell

II Optic nerve – sensory for vision

III Oculomotor nerve – motor fibers to eye muscles

IV Trochlear – motor fiber to eye muscles



V Trigeminal nerve – sensory for the face; motor fibers to chewing muscles

VI Abducens nerve – motor fibers to eye muscles

VII Facial nerve – sensory for taste; motor fibers to the face

VIII Vestibulocochlear nerve – sensory for balance and hearing



IX Glossopharyngeal nerve – sensory for taste; motor fibers to the pharynx

X Vagus nerves – sensory and motor fibers for pharynx, larynx, and viscera

XI Accessory nerve – motor fibers to neck and upper back

XII Hypoglossal nerve – motor fibers to tongue

Cranial Nerves Mnemonic (a memory aid)

On Old Olympus Towering Top, A Finn And German Vaulted A Hedge

Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Acoustic (vestibulocochlear), Glossopharyngeal, Vagus, Accessory, Hypoglossal

Aging of the Nervous System

• Brain decreases in size and weight

• Speed of processing information slows

• Movements slowed

• Memory diminishes

The Nervous System: The Brain and Cranial Nerves AHS 101.

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