The Nervous SystemThe Nervous SystemThe Brain The Brain Chapter 16Chapter 16

The Nervous SystemThe Nervous SystemThe Brain The Brain Chapter 16Chapter 16

The Brain - Overview

Brain stem

medulla oblongata (M.O.)

pons

midbrain (mesencephalon)

Diencephalon

thalamus

hypothalamus

epithalamus (pineal gland)

Cerebrum

Cerebellumm.o.

pons

midbrain

T

HPP

Cerebrum

Cerebellum

Cranial Meninges

Three layers: Dura mater, Arachnoid mater, Pia mater

Dura mater – tough, fibrous outer layer; 2 layers thick around brain (superficial “periosteal layer”/deeper “meningeal layer”) with creation of dural (venous) sinuses between layers, and dural folds into cranial cavity

Dural folds

Falx cerebri

Tentorium cerebelli

Folds that create septa to subdivide cranial cavity and stabilize the brain. Includes:

falx cerebri – between cerebral hemispheres in longitudinal fissure

tentorium cerebelli – between cerebrum & cerebellum in transverse fissure

falx cerebelli – between cerebellar hemispheres

diaphragma sellae – lines sella turcica

Dural sinuses

Superior sagittal sinus

Transverse sinus

Inferior sagittal sinusFalx cerebri

Tentorium cerebelli

Straight sinus

Confluence of sinuses

Sigmoid sinus

Spaces between dural layers and dural folds functioning as veins for drainage of blood from cerebral veins, and CSF from subarachnoid space (superor sagittal sinus)

Arachnoid mater – “spidery” web-like middle layer with fine collagen & elastic connections to underlying Pia Mater

Pia mater – delicate, thin inner layer

Subarachnoid space – between arachnoid & pia mater; contains cerebrospinal fluid (CSF)

Arachnoid granulations (villi) – projections of arachnoid into dural sinuses for drainage of CSF

Cerebrospinal Fluid (CSF) clear, colorless fluid formed by filtration of blood plasma by choroid plexuses within ventricles of the brain.

functions in protection of CNS, support, nutrient supply, waste removal

CSF Circulation

Lateral ventricles (in cerebral hemispheres) interventricular foramen third ventricle (in diencephalon around and between R/L thalamus) cerebral (mesencephalic) aqueduct of midbrain fourth ventricle (between pons/cerebellum) subarachnoid space & central canal of SC

Reabsorption of CSF through arachnoid granulations (arachnoid villi) of dural sinuses (superior sagittal sinus) into cerebral veins

Blood supply to Brain Brain requires large amounts of O2 and nutrients (glucose)

Internal carotid arteries + basilar artery (from vertebral arteries) “cerebral arterial circle (of Willis)”

Venous drainage from dural venous sinuses & cerebral veins into vertebral and internal jugular veins

The Brainstem Medulla oblongata

continuation of the SC above the foramen magnum

contains the pyramidal decussation within the pyramids

cranial nerve nuclei (XII-VIII (cochlear)

cardiac, vasomotor, & respiratory reflex centers

Pons

“bridge” linking cerebellum to SC & other parts of brain via middle cerebellar peduncle

cranial nerve nuclei (VIII (vestibular) – V)

respiratory center

The Brainstem Midbrain (mesencephalon)

cerebral peduncles – location of ascending (sensory) & descending (motor) tracts

tectum – posterior aspect of brainstem; contains

corpora quadrigemina

superior colliculi – visual reflex centers

inferior colliculi – auditory reflex centers

cranial nerve nuclei (IV-III)

The Brainstem Midbrain (mesencephalon)

substantia nigra – nucleus with dark pigmented neurons that regulate motor output of basal nuclei (basal ganglia) of cerebrum

reticular formation – network of interconnected nuclei throughout brainstem responsible for maintaining states of consciousness

The DiencephalonThalamus

surrounds 3rd ventricle

2 sides (left & right thalamus) usually connected by intermediate mass (interthalamic adhesion)

comprised of nuclei that function primarily as sensory relay stations

Hypothalamus connects to pituitary gland via the infundibulum has many important functions relating to maintaining homeostasis including (but not limited to):

-integrating nervous & endocrine systems through control over pituitary gland

-integration of ANS from visceral stimuli-hunger/satiety, thirst, body

temp. regulation, circadian rhythms-hormone production

(ADH, oxytocin) mamillary bodies – reflex centers associated with eating, & processing of olfactory sensations

The Diencephalon

The DiencephalonEpithalamus -Pineal gland

secretes Melatonin which helps regulate day-night cycles (circadian rhythm)

The Cerebellum Separated from cerebrum by transverse fissure

“Tentorium cerebelli” encloses straight sinus & transverse sinus

Two hemisphereres joined by vermis

Hemispheres have 3 lobes – anterior, posterior & flocculonodular

outer cortex of gray matter folded into “folia”

inner white matter “arbor vitae”

Transverse fissure

The Cerebellum

Functions include: control of skeletal muscles (unconscious) for balance, coordination & posture stores patterns of movement

Links to brainstem by cerebellar peduncles inferior cerebellar peduncle M.O. (and S.C.) middle cerebellar peduncle pons superior cerebellar peduncle midbrain (and diencephalon/cerebrum)

Cerebrumgyrus

sulcus

convolutions

Transverse fissure

Frontal lobe

Central sulcus

Parietal lobe

Occipital lobe

Parieto-occipital sulcus (seen along medial surface)

Temporal lobe

Lobes of Cerebral Hemispheres

Lateral sulcus

(Insula is deep to lateral sulcus)

insula

Parieto-occipital sulcus

Gray & White matter of cerebrumGray matter :

superficial cortex –functional areas includes sensory, motor , & higher order functions deep cerebral nuclei (aka basal nuclei/basal ganglia)

White matter: fibers – association commissural projection

Association fibers

Commissural fibers

Projection fibers

association fibers – connect gyri in same hemisphere commissural fibers – connect gyri in opposite hemispheres (e.g. corpus callosum, anterior commissure) projection fibers – connect cerebrum with other parts of brain & spinal cord (e.g. internal capsule)

White matter of cerebrum

Gray matter of cerebrum Paired clusters of gray matter deep within cerebral hemispheres Include: caudate nucleus, putamen, globus pallidus Involved primarily in subconscious control of skeletal muscle tone, and coordination of movement patterns once movement is initiated

Basal (cerebral) Nuclei

Gray matter of cerebrum

Motor and Sensory areas – receive sensory info & generate motor (skeletal muscle) responses

Association areas – interpretation of sensory info & planning and coordination of motor responses

Cerebral processing centers - higher order integrative & analytical functions

Cerebral Cortex - Functional areas

Motor & Sensory

primary motor cortex (precentral gyrus)

Motor & Sensory

primary sensory cortex (postcentral gyrus)

Motor & Sensory primary motor cortex (precentral gyrus)

gustatory cortex

primary sensory cortex (postcentral gyrus)

auditory cortex

olfactory cortex

visual cortex

Association areas• interpret incoming sensations; coordinate motor responsessomatic motor association

area (premotor cortex)

visual association area

Cerebral Processing Centers• higher-order integrative centers

• may be unilateral

general interpretive area (Wernike’s) –Lt hemisphere usually

motor speech center (Broca’s) - Lt hemisphere usually

Prefrontal cortex (bilat.)

Hemispheric SpecializationHigher order centers in brain not bilaterally symmetrical in regards to function:Left hemisphere more involved in linear, mathematical, verbal, analytical functionsRight hemisphere more involved in abstract analysis, spatial perception, sensory relationship, music, emotional context of language

Functionally related areas in cerebrum, thalamus & hypothalamus involved in emotional states, drives & behaviors linking conscious areas of cerebrum with unconscious areas of brainstem long term memory

Limbic System

Major areas include:Amygdaloid body (amygdala)Cingulate gyrusDentate gyrusParahippocampal gyrusHippocampus FornixMamillary bodies

Cranial Nerves 12 pairs of nerves that connect to the brain; provide motor, sensory &/or autonomic (parasympathetic) function

Cranial Nerves (know #, name & basic function)

I Olfactory – smell

II Optic – sight

III Oculomotor – motor to eye muscles; ANS for accommodation of lens & pupil constriction

IV Trochlear – motor to one eye muscle

V Trigeminal – motor to muscles of mastication, sensation to face & mouth

VI Abducens – motor to one eye muscle

VII Facial – motor to muscles of facial expression; taste; ANS to lacrimal & salivary glands

VIII Vestibulocochlear – equilibrium & hearing

IX Glossopharyngeal – swallowing, taste, ANS to salivary glands, sensory reception from monitoring of blood pressure in large arteries

X Vagus – sensation from viscera; ANS visceral muscle movement (respiratory, digestive, cardiovascular systems)

XI Accessory – motor to muscle of pharynx, SCM & Trapezius

XII Hypoglossal – motor to tongue muscles