1 The Central Nervous System Brain II Cranial Nerves

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The Central Nervous System

Brain II

Cranial Nerves

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Lecture Overview• Review/Questions from last lecture (Brain I)

• Brain II (pp. 84-87)– Cerebrum

• Myelinated tracts• Basal ganglia• Sensory areas• Motor areas

– Brain coverings (meninges)– Cerebrospinal fluid (CSF)– Ventricular System– Cranial nerves

Review of Major Brain Areas

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12

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1

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5

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10 (White part)6 7 8 9

Summary from Last Lecture

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Part of Brain Major Function

Brainstem

Medulla Oblongata(Embryology?)(Ventricles nearby?)

1. Contains cardiac, vasomotor, and respiratory control centers2. Nucleus gracilis/cunneatus3. Origin of CN 9, 10, 11, 12

Pons(Embryology?)(Ventricles nearby?)

1. Bridge between medulla and midbrain via transverse tracts (to cerebellum) and longitudinal tracts(to medulla/midbrain)

2. Helps regulate rate and depth of breathing3. Origin of CN 5, 6, 7, 8

Midbrain(Embryology?)(Ventricles nearby?)

1. Major connecting center between spinal cord and brain and parts of brainstem2. Contains corpora quadrigemina (visual and auditory reflexes)3. Origin of CN 3 and 44. Location of red nucleus (rubrospinal tract)5. Origin of substantia nigra

Cerebellum(Embryology?)(Ventricles nearby?)

1. Subconscious coordination of skeletal muscle activity, maintains posture2. Hemispheres separated by falx cerebelli and vermis3. Cerebellar peduncles (sup, middle, inf) attach to rest of brainstem

Diencephalon (Embryology?)(Ventricles nearby?)

Thalamus 1. gateway (relay) for sensory impulses heading to cerebral cortex; hearing, vision, taste2. Crude interpretation for pain, touch, pressure, and temperature3. relay for motor information (voluntary)4. Forms walls of third ventricle

Hypothalamus 1. Vital functions associated with homeostasis, ANS, psychosomatic illness, feeding/satiety2. Connected to pituitary by infundibulum (pituitary stalk)

Brain - Cerebrum

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-Over 85% of brain mass, with about 14 billion multipolar neurons in cortex- Lobes names for overlying bones. (See sulci above for divisions)

Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

Brain - Cerebrum

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Upper figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

Lateral Sulcus


Dural Folds

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Falx Cerebri – within longitudinal fissure; separates cerebral hemispheres

Tentorium Cerebelli – above cerebellum; separates occipital lobe from cerebellum


Myelinated Tracts of Cerebrum

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Three types of myelinated tracts form cerebral white matter:

1. Association – same hemisphere

2. Commisural – between corresponding gyri in opposite hemispheres (corpus callosum)

3. Projection (Projector) – Ascending and descending tracts


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Basal Nuclei (formerly basal ganglia)• nuclei are masses of gray matter in CNS

• deep within cerebral hemispheres

• three nuclei: caudate nucleus and putamen, (together called the striatum), and the globus pallidus

• subconscious control certain muscular activities, e.g., learned movement patterns

1. Receive input from entire cerebral cortex.

2. Relay motor impulses originating in the substantia nigra (where is this?), along with their own output, through the thalamus to the motor cortex to influence muscle movement.

Basal Nuclei – Transparent View

10Figure From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

Brain – Sensory and Motor Areas

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*Somatosensory (in figure) = Somesthetic (in your notes)

(Gnostic)

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46

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1719

184142 22

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75

9

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*

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Meninges of the Brain

- dura mater – outer, tough (anchoring dural folds)

- arachnoid mater – web-like

- pia mater – inner, delicate

- Subdural space – like interstitial fluid

- Subarachnoid space – CSF

*Singular of meninges is meninx


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Cerebrospinal Fluid• ~500 ml/day secreted by choroid plexus of ventricles; only ~120 ml present in subarachnoid space at one time

• circulates in all ventricles, cerebral aqueduct, central canal of spinal cord, and subarachnoid space

• completely surrounds brain and spinal cord

• clear liquid (more Na+ and Cl-, but less K+, Ca2+, glucose, and protein than plasma)

• nutritive and protective (shock absorber)

Flow of CSF

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(Luscka)

(Magendie)

(Monro)


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Ventricles of the Brain

• interconnected cavities• within cerebral hemispheres and brain stem• continuous with central canal of spinal cord• filled with cerebrospinal fluid (CSF)

• lateral ventricles (2)• rt/lt cerebral hemispheres• under corpus callosum

• third ventricle (1)• between thalamus

• fourth ventricle (1)• between cerebellum and pons

• cerebral aqueduct connect 3rd and 4th

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Divisions of the Nervous System

CNS PNS

You are here

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Peripheral Nervous System

• Cranial nerves arising from the brain• Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera

• Spinal nerves arising from the spinal cord• Somatic fibers connecting to the skin and skeletal muscles• Autonomic fibers connecting to viscera

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Cranial NervesPaired. Numbered (roughly) in the order of their occurrence from anterior to posterior. Abbreviated using N or CN.

Figure from: Hole’s Human A&P, 12th edition, 2010

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The Cranial NervesNumeral

Name

Function Sensory, Motor, or Both (Mixed Nerve)

I OLFACTORY (OLD) OLFACTION/SMELL SENSORY (SOME)

II OPTIC (OPIE) VISION SENSORY (SAY)

III OCULOMOTOR (OCCASIONALLY) MOVE EYE; ACCOMMODATION; PUPIL SIZE

MOTOR (MARRY)

IV TROCHLEAR (TRIES) MOVE EYE (superior oblique) MOTOR (MONEY)

V TRIGEMINAL (TRIGONOMETRY) MAJOR SENSORY NERVE FROM FACE; MASTICATION (chewing)

BOTH (BUT)

VI ABDUCENS (AND) MOVE EYE (lateral rectus) MOTOR (MY)

VII FACIAL (FEELS) MAJOR MOTOR NERVE OF FACE BOTH (BROTHER)

VIII VESTIBULOCOCHLEAR (VERY)(ACOUSTIC)

HEARING AND EQUILIBRIUM SENSORY (SAYS)

IX GLOSSOPHARYNGEAL (GLOOMY) MOVE MUSCLES OF TONGUE AND PHARYNX; CIRCULATORY AND ESPIRATORY REFLEXES

BOTH (BIG)

X VAGUS (VAGUE) INNERVATE VISCERAL SMOOTH MUSCLE; MUSCLES OF SPEECH; CVS REFLEXES

BOTH (BOOBS)

XI ACCESSORY (AND) MOVE NECK MUSCLES MOTOR (MATTER)

XII HYPOGLOSSAL (HYPOACTIVE) MOVE TONGUE; SPEECH, MASTICATION, DELGLUTITION (swallowing)

MOTOR (MOST)

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Cranial Nerves I and II

Olfactory (I)• sensory• fibers transmit impulses associated with smell

Optic (II)• sensory• fibers transmit impulses associated with vision

Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001

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Cranial Nerves III, IV, and VI

Trochlear (IV)• primarily motor• origin in midbrain• motor impulses to the superior oblique (SO) muscles that move the eyes

Oculomotor (III)• primarily motor• origin in midbrain• motor impulses to muscles that

• raise eyelids• move the eyes• focus lens• adjust pupil size

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

What’s a ganglion?

Abducens (VI)• primarily motor• origin in pons• motor impulses to the lateral rectus (LR) muscles that move the eyes

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Cranial Nerve V

Trigeminal (V)• both sensory and motor• origin in pons• opthalmic division

• sensory from surface of eyes (cornea), tear glands, scalp, forehead, and upper eyelids

• maxillary division• sensory from upper teeth, upper gum, upper lip, palate, and skin of face

• mandibular division• sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip• motor to muscles of mastication and muscles in floor of mouth

Major sensory nerve of face

Figure from: Hole’s Human A&P, 12th edition, 2010

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Cranial Nerve VII

Facial (VII)• both sensory and motor• sensory from taste receptors (ant. 2/3 tongue)• motor to muscles of facial expression, orbicularis oculi, tear glands, and submandibular and sublingual salivary glands

Major MOTOR nerve of face

Figures From: Marieb & Hoehn, Human Anatomy & Physiology, 9th ed., Pearson, 2013

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Cranial Nerves VIII and IXVestibulocochlear (VIII)

• sensory• origin in pons• sensory from equilibrium receptors of ear• sensory from hearing receptors

Glossopharyngeal (IX)• both sensory and motor• origin in medulla• sensory from pharynx, tonsils, tongue (post. 1/3), and carotid arteries• motor to parotid salivary gland and muscles of pharynx

Figures from: Martini, Anatomy & Physiology, Prentice Hall, 2001

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Cranial Nerve XVagus (X)

• both sensory and motor

• origin in medulla

• somatic motor to muscles of speech and swallowing

• autonomic motor (parasympathetic) to viscera of thorax and abdomen

• CVS and respiratory reflexes

• sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen

Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

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Cranial Nerves XI and XIIAccessory (XI)

• primarily motor• origin in medulla/spinal cord• motor to muscles of soft palate, pharynx, larynx, neck (sternocleidomastoid), and back (trapezius)

Hypoglossal (XII)• primarily motor• origin in medulla•motor to muscles of the tongue• impt in speech, mastication, and deglutition

Figure from: Martini, Fundamentals of Anatomy & Physiology, Pearson Education, 2004

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1 The Central Nervous System Brain II Cranial Nerves