ANSWER THE ESSAYS AND THE BULLET (-) QUESTIONS

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APLECTURE21CentralNervousSystem-PartII.ppt

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Central Nervous System- Part II

The Forebrains

Diencephalon

Mesencephalon

Telencephalon

Forebrain

Pons

Cerebellum

Metencephalon

Spinal cord

Hindbrain

Midbrain

Myelencephalon

(medulla oblongata)

forebrain consists of :

the diencephalon
encloses the third ventricle
most rostral part of brainstem
has three major embryonic derivatives
thalamus
hypothalamus
epithalamus

the telencephalon
develops chiefly into the cerebrum

Diencephalon: Thalamus

thalamus – at the superior end of brainstem beneath cerebral hemispheres
the “gateway to the cerebral cortex” – thalamic nuclei filters information to cerebral cortex
key role in motor control
relays signals from cerebellum to cerebrum
provides feedback loops between cerebral cortex & basal nuclei
Limbic system- thalamic nuclei a component

leaves

(a) Thalamus

Anterior group

Medial group

Ventral group

Lateral group

Posterior group

Lateral geniculate nucleus

Medial geniculate nucleus

Thalamic Nuclei

Part of limbic system;

memory and emotion

Emotional output to prefrontal

cortex; awareness of emotions

Somesthetic output to

postcentral gyrus; signals

from cerebellum and basal

nuclei to motor areas of cortex

Somesthetic output to

association areas of cortex;

contributes to emotional function

of limbic system

Relay of visual signals to

occipital lobe (via lateral

geniculate nucleus) and auditory

signals to temporal lobe (via

medial geniculate nucleus)

hypothalamus –
forms part of walls and floor of third ventricle

major control center of autonomic nervous system and endocrine system
plays essential roll in homeostatic regulation of all body systems

Diencephalon: Hypothalamus

leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe

Parieto–occipital sulcus

Occipital lobe

Pineal gland

Habenula

Posterior commissure

Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)

Epithalamus

commissure

Temporal lobe

Medulla

oblongata

functions of hypothalamic nuclei
hormone secretion
autonomic effects
thermoregulation
food and water intake
rhythm of sleep and waking
memory
emotional behavior

Diencephalon: Epithalamus

epithalamus – very small mass of tissue composed of:
pineal gland – endocrine gland
habenula – relay from the limbic system to the midbrain
thin roof over the third ventricle

leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe

Parieto–occipital sulcus

Occipital lobe

Pineal gland

Habenula

Posterior commissure

Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)

Epithalamus

commissure

Temporal lobe

Medulla

oblongata

Telencephalon: Cerebrum

cerebrum – largest and most conspicuous part of the human brain
seat of sensory perception, memory, thought, judgment, and voluntary motor actions

leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe

Parieto–occipital sulcus

Occipital lobe

Pineal gland

Habenula

Posterior commissure

Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)

Epithalamus

commissure

Temporal lobe

Medulla

oblongata

Cerebrum - Gross Anatomy

two cerebral hemispheres divided by longitudinal fissure
connected by white fibrous tract the corpus callosum
gyri and sulci – increases amount of cortex in the cranial cavity
gyri increases surface area for information processing capability
some sulci divide each hemisphere into five lobes named for the cranial bones that overly them

Frontal lobe

Occipital lobe

Central sulcus

Longitudinal fissure

Parietal lobe

(a) Superior view

Cerebral

hemispheres

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral

Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe

frontal lobe
voluntary motor functions
motivation, foresight, memory, mood, emotion, & aggression
parietal lobe
receives & integrates general sensory information, taste & some visual processing
occipital lobe
primary visual center of brain
temporal lobe
areas for hearing, smell, learning, memory, & some aspects of vision & emotion
insula (hidden by other regions)
understanding spoken language, taste & sensory information from visceral receptors

Cerebrum Function- Lobes

Postcentral gyrus

Occipital lobe

Temporal lobe

Lateral sulcus

Frontal lobe

Parietal lobe

Insula

Rostral

Caudal

Central

sulcus

Precentral

gyrus

Cerebral White Matter- most of volume of cerebrum
transmits signals between brain regions

Association tracts

Frontal lobe

Corpus callosum

Temporal lobe

(a) Sagittal section

Projection tracts

Parietal lobe

Occipital lobe

Longitudinal fissure

Corpus callosum

Basal nuclei

Cerebral peduncle

Projection tracts

Decussation in pyramids

Commissuralta tracts

Lateral ventricle

Thalamus

Third ventricle

Mammillary body

pons

Pyramid

Medulla oblongata

(b) Frontal section

14-*

Cerebral Cortex

neural integration is carried out in the gray matter of the cerebrum

cerebral gray matter found in three places
cerebral cortex
basal nuclei
limbic system

cerebral cortex – layer covering the surface of the hemispheres
only 2 – 3 mm thick
cortex constitutes about 40% of the mass of the brain
contains 14 – 16 billion neurons

III

Cortical surface

Stellate cells

Small pyramidal

cells

Large pyramidal

cells

White

matter

Figure 14.15

Cerebral Cortex

contains two principal types of neurons

stellate cells
receive sensory input and process information on a local level
pyramidal cells
include the output neurons of the cerebrum
only neurons that leave the cortex and connect with other parts of the CNS

Neocortex- 6-layered tissue,

constitutes ~90% cerebral

cortex

III

Cortical surface

Stellate cells

Small pyramidal

cells

Large pyramidal

cells

White

matter

The Basal Nuclei

basal nuclei – masses of cerebral gray matter buried deep in the white matter, lateral to the thalamus
receives input from substantia nigra of midbrain & motor areas of cortex
send signals back to both these locations
involved in motor control

Cerebrum

Corpus callosum

Lateral ventricle

Thalamus

Insula

Optic tract

Hypothalamus

Third ventricle

Pituitary gland

Internal capsule

Caudate nucleus

Putamen

Subthalamic nucleus

Globus pallidus

Lentiform

nucleus

Corpus

striatum

Limbic System

limbic system – important center of emotion and learning
most anatomically prominent components are:
cingulate gyrus
Hippocampus-memory
Amygdala-emotion
limbic system components are connected through a complex loop of fiber tracts allowing for somewhat circular patterns of feedback
limbic system structures have centers for both gratification and aversion

Basal nuclei

Amygdala

Temporal lobe

Fornix

Hippocampus

Medial

prefrontal

cortex

Corpus

callosum

Cingulate

gyrus

Orbitofrontal

cortex

Thalamic

nuclei

Mammillary

body

Higher Brain Functions

higher brain functions - sleep, memory, cognition, emotion, sensation, motor control, and language

involve interactions between cerebral cortex and basal nuclei, brainstem and cerebellum

functions of the brain do not have easily defined anatomical boundaries

integrative functions of the brain focuses mainly on the cerebrum, but involves combined action of multiple brain levels

Motor Control

intention to contract a muscle begins in motor association area of frontal lobes
where we plan our behavior
where neurons compile program for degree & sequence of muscle contraction required action
program transmitted to neurons of the precentral gyrus (primary motor area)
neurons send signals to the brainstem and spinal cord
ultimately resulting in muscle contraction

pyramidal cells of the precentral gyrus are called upper motor neurons

in the brainstem or spinal cord, the fibers from upper motor neurons synapse with lower motor neurons whose axons innervate the skeletal muscles

basal nuclei and cerebellum are also important in muscle control

Motor Control

basal nuclei
determines onset & cessation of intentional movements
highly practiced, learned behaviors that one carries out with little thought
writing, typing, driving a car
lies in a feedback circuit from the cerebrum to the basal nuclei to the thalamus and back to the cerebrum
dyskinesias – movement disorders caused by lesions in the basal nuclei

cerebellum
highly important in motor coordination
aids in learning motor skills
maintains muscle tone and posture
smoothes muscle contraction
coordinates eye and body movements
ataxia – clumsy, awkward gait

Input and Output to Cerebellum

Cerebrum

Motor cortex

Cerebellum

Brainstem

Inner ear

Eye

Reticular formation

Muscle and joint proprioceptors

(a) Input to cerebellum

(b) Output from cerebellum

Spinocerebellar

tracts of spinal cord

Reticulospinal

and vestibulospinal

tracts of spinal cord

Limb and postural

muscles

Cerebral Lateralization

leaves

Olfaction, left nasal cavity

Memory for shapes

Left hand motor control

Musical ability

Intuitive, nonverbal thought

Vision, left field

Vision, right field

Speech

Verbal memory

Olfaction, right nasal cavity

Left hemisphere

Right hemisphere

Posterior

(Limited language

comprehension, mute)

Feeling shapes with

left hand

Hearing nonvocal sounds

(left ear advantage)

Superior recognition of

faces and spatial

relationships

Right hand

motor control

Feeling shapes

with right hand

Hearing vocal sounds

(right ear advantage)

Rational, symbolic

thought

Superior language

comprehension

Cranial Nerves

the brain must communicate with the rest of the body
most of input/output travels by spinal cord
12 pairs of cranial nerves arise from the base of the brain
exit the cranium through foramina
lead to muscles and sense organs located mainly in the head and neck

some cranial nerves are classified as motor, some sensory, others mixed
sensory (I, II, and VIII)
motor (III, IV, VI, XI, and XII)
stimulate muscle but also contain fibers of proprioception
mixed (V, VII, IX, X)
sensory functions may be quite unrelated to their motor function

Cranial Nerves

leaves

Cranial nerves:

Optic nerve (II)

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vestibulocochlear nerve (VIII)

Glossopharyngeal nerve (IX)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Vagus nerve (X)

Oculomotor nerve (III)

Frontal lobe

Cerebellum

Olfactory tract

Temporal lobe

Infundibulum

Pons

Medulla

Optic chiasm

Olfactory tract

Temporal lobe

Pons

Spinal cord

(a)

(b)

Olfactory bulb

(from olfactory nerve, I)

Longitudinal

fissure

Medulla

oblongata

b: © The McGraw-Hill Companies, Inc./Rebecca Gray, photographer/Don Kincaid, dissections

I Olfactory Nerve

sense of smell

damage causes impaired sense of smell

Olfactory bulb

Olfactory tract

Nasal mucosa

Cribriform plate of

ethmoid bone

Fascicles of

olfactory nerve (I)

II Optic Nerve

provides vision
damage causes blindness in part or all of the visual field

Eyeball

Optic nerve (II)

Optic chiasm

Optic tract

Pituitary gland

III Oculomotor Nerve

controls muscles that turn the eyeball up, down, and medially, as well as controlling the iris, lens, and upper eyelid

damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing and inability to move eye in certain directions

Oculomotor nerve (III):

Superior orbital fissure

Superior branch

Inferior branch

Ciliary ganglion

IV Trochlear Nerve

eye movement (superior oblique muscle)

damage causes double vision and inability to rotate eye inferolaterally

Trochlear nerve (IV)

Superior orbital fissure

Superior oblique muscle

V Trigeminal Nerve

largest of the cranial nerves

most important sensory nerve of the face

forks into three divisions:

ophthalmic division (V1) – sensory
maxillary division (V2) – sensory
mandibular division (V3) - mixed

Lingual nerve

Superior orbital fissure

Ophthalmic division (V1)

Trigeminal ganglion

Trigeminal nerve (V)

Maxillary division (V2)

Mandibular division (V3)

Foramen ovale

Foramen rotundum

Temporalis muscle

Medial pterygoid muscle

Masseter muscle

Lateral pterygoid muscle

Infraorbital

nerve

Superior

alveolar nerves

Inferior

alveolar nerve

Anterior belly of

digastric muscle

Anterior trunk of V3 to

chewing muscles

Motor branches of the

mandibular division (V3)

Distribution of sensory

fibers of each division

VI Abducens Nerve

provides eye movement (lateral rectus m.)

damage results in inability to rotate eye laterally and at rest eye rotates medially

Abducens nerve (VI)

Superior orbital fissure

Lateral rectus muscle

VII Facial Nerve

motor – major motor nerve of facial muscles: facial expressions; salivary glands and tear, nasal and palatine glands
sensory - taste on anterior 2/3’s of tongue
damage produces sagging facial muscles and disturbed sense of taste (no sweet and salty)

Geniculate ganglion

Pterygopalatine ganglion

Lacrimal (tear) gland

Submandibular gland

Stylomastoid foramen

Sublingual gland

Internal acoustic meatus

Facial nerve (VII)

(a)

Parasympathetic fibers

Submandibular ganglion

Motor branch

to muscles of

facial expression

to (b)

Chorda tympani

branch (taste and

salivation)

Five Branches of Facial Nerve

Temporal

Zygomatic

Buccal

Mandibular

Cervical

(b)

Temporal

Zygomatic

Buccal

Mandibular

(c)

Cervical

VIII Vestibulocochlear Nerve

nerve of hearing and equilibrium

damage produces deafness, dizziness, nausea, loss of balance & nystagmus (involuntary rhythms oscillation of the eyes from side to side

leaves

Cochlear nerve

Cochlea

Semicircular

ducts

Vestibular ganglia

Vestibular nerve

Vestibulocochlear

nerve (VIII)

Internal

acoustic meatus

Vestibule

IX Glossopharyngeal Nerve

swallowing, salivation, gagging, control of BP and respiration

sensations from posterior 1/3 of tongue

damage results in loss of bitter and sour taste and impaired swallowing

Glossopharyngeal nerve (IX)

Parotid salivary gland

Jugular foramen

Superior ganglion

Inferior ganglion

Otic ganglion

Carotid sinus

Pharyngeal muscles

X Vagus Nerve

most extensive distribution of any cranial nerve

major role in the control of cardiac, pulmonary, digestive, and urinary function

swallowing, speech, regulation of viscera

damage causes hoarseness or loss of voice, impaired swallowing & fatal if both are cut

Heart

Lung

Liver

Spleen

Small intestine

Stomach

Kidney

Carotid sinus

Laryngeal nerve

Pharyngeal nerve

Jugular foramen

Vagus nerve (X)

Colon

(proximal portion)

swallowing, head, neck and shoulder movement
damage causes impaired head, neck, shoulder movement;
head turns towards injured side

XI Accessory Nerve

Accessory nerve (XI)

Cranial root of XI

Spinal root of XI

Posterior view

Vagus nerve

Sternocleidomastoid

muscle

Trapezius muscle

Jugular

foramen

Foramen

magnum

Spinal nerves

C3 and C4

tongue movements for speech, food manipulation and swallowing
if both are damaged – can’t protrude tongue
if one side is damaged – tongue deviates towards injured side

XII Hypoglossal Nerve

Hypoglossal canal

Hypoglossal nerve (XII)

Intrinsic muscles

of the tongue

Extrinsic muscles

of the tongue