Directional Terms and Landmarks · Cerebrum - Gross Anatomy • two cerebral hemispheres divided by...

14-1

Directional Terms and Landmarks

14-2

Cerebrum • longitudinal fissure – deep

groove that separates cerebral hemispheres

• gyri - thick folds

• sulci - shallow grooves

• corpus callosum – thick nerve bundle at bottom of longitudinal fissure that connects hemispheres

Figure 14.1a

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Frontal lobe

Occipital lobe

Central sulcus

Longitudinal fissure

Parietal lobe

(a) Superior view

Cerebralhemispheres

14-3

Cerebellum

• occupies posterior cranial fossa

• marked by gyri, sulci, and fissures

• about 10% of brain volume

• contains over 50% of brain neurons

Figure 14.1b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


14-4

Brainstem

• brainstem – what remains of the brain if the cerebrum and cerebellum are removed

• major components

– diencephalon

– midbrain

– pons

– medulla oblongata

Figure 14.1b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


14-5

Median Section of the Brain

Figure 14.2a


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)

EpithalamusAnteriorcommissure

Temporal lobe

Medullaoblongata

14-6

Gray and White Matter• gray matter – the seat of neuron cell bodies,

dendrites, and synapses– forms surface layer, cortex, over cerebrum and

cerebellum

– forms nuclei deep within brain

• white matter - bundles of axons– lies deep to cortical gray matter, opposite relationship

in the spinal cord– composed of tracts, bundles of axons, that connect one

part of the brain to another, and to the spinal cord

Embryonic Neural TubeCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

leaves

(a) 19 days

(c) 22 days

Ectoderm

Notochord

Neural groove

Neural fold

Neural plate

(b) 20 days

(d) 26 days

Somites

Neural crestNeural crest

Neuralcrest

Neuraltube

14-7

Figure 14.3

14-8

Meninges of the Brain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Subdural space

Skull

Pia mater

Blood vessel

Dura mater: Periosteal layer Meningeal layer

Arachnoid mater

Brain:

Gray matter

White matter

Arachnoid villusSubarachnoidspace

Superior sagittalsinus

Falx cerebri(in longitudinalfissure only)

Figure 14.5

14-9

Brain Ventricles

Figure 14.6 a-b

Lateral ventricles

Central canal

Lateral aperture

Fourth ventricle

Third ventricle

Median aperture

(a) Lateral view

Caudal

Interventricularforamen

Cerebralaqueduct

Rostral

Lateral ventricle

Third ventricle

Cerebrum

Lateral aperture

Fourth ventricle

Median aperture

(b) Anterior view

Interventricularforamen

Cerebralaqueduct


14-10

Ventricles and Cerebrospinal Fluid• ventricles – four internal chambers within the brain

– two lateral ventricles – one in each cerebral hemisphere – third ventricle - single narrow medial space beneath corpus

callosum– fourth ventricle – small triangular chamber between pons and

cerebellum• connects to central canal runs down through spinal cord

14-11

Cerebrospinal Fluid (CSF)choroid plexus – spongy mass of blood capillaries on the floor of

each ventricleProduced cerebrospinal fluid

ependyma – neuroglia that lines the ventricles and covers choroid plexus

produces cerebrospinal fluid

• cerebrospinal fluid (CSF) – clear, colorless liquid that fills the ventricles and canals of CNS– bathes its external surface

• ependymal cells modify blood filtrate

14-12

Functions of CSF• buoyancy

– allows brain to attain considerable size without being impaired by its own weight

– if it rested heavily on floor of cranium, the pressure would kill the nervous tissue

• protection– protects the brain from striking the cranium when the head

is jolted

• chemical stability– flow of CSF rinses away metabolic wastes from nervous

tissue and homeostatically regulates its chemical environment

14-13

Flow of Cerebrospinal FluidCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Choroid plexus in fourthventricle adds more CSF.

CSF flows out two lateral aperturesand one median aperture.

CSF fills subarachnoid space andbathes external surfaces of brainand spinal cord.

At arachnoid villi, CSF is reabsorbedinto venous blood of duralvenous sinuses.

1

2

3

4

56

7

7

8

1

2

3

4

5

6

7

8

CSF is secreted bychoroid plexus ineach lateral ventricle.

CSF flows throughInterventricular foraminainto third ventricle.

Choroid plexus in thirdventricle adds more CSF.

CSF flows down cerebralaqueduct to fourth ventricle.

Arachnoid villus

Superiorsagittalsinus

Arachnoid mater

Subarachnoidspace

Dura mater

Choroid plexus

Third ventricle

Cerebralaqueduct

Lateralaper ture

Fourth ventricle

Median aperture

Centralcanalof spinal cord

Subarachnoidspace ofspinal cordFigure 14.7

14-14

Blood Supply to the Brain

•brain is only 2% of the adult body weight, and receives 15% of the blood•neurons have a high demand for ATP, and therefore, oxygen and glucose, so a constant supply of blood is critical to the nervous system

– 10 second interruption of blood flow may cause loss of consciousness

– 1 – 2 minute interruption can cause significant impairment of neural function

– 4 minutes with out blood causes irreversible brain damage

14-15

Brain Barrier System• blood is also a source of antibodies, macrophages, bacterial toxins, and

other harmful agents

• brain barrier system – strictly regulates what substances can get from the bloodstream into the tissue fluid of the brain

• blood-brain barrier - protects blood capillaries throughout brain tissue– consists of tight junctions between endothelial cells that form the capillary

walls– astrocytes reach out and contact capillaries with their perivascular feet– induce the endothelial cells to form tight junctions that completely seal off

gaps between them– anything leaving the blood must pass through the cells, and not between

them– endothelial cells can exclude harmful substances from passing to the brain

tissue while allowing necessary ones to pass

14-17

Medulla Oblongata

• cardiac center – adjusts rate and force of heart

• vasomotor center – adjusts blood vessel diameter

• respiratory centers – control rate and depth of breathing

• reflex centers – for coughing, sneezing, gagging, swallowing,

vomiting, salivation, sweating, movements of tongue and head

14-18

Medulla and PonsCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Diencephalon:

Midbrain:

Thalamus

Optic tract

Cranial nerves:

Oculomotor nerve (III)

Optic nerve (II)

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vestibulocochlear nerve (VIII)

Glossopharyngeal nerve (IX)

Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Spinal nerves

Infundibulum

Mammillary body

Cerebral peduncle

Pyramid

Anterior median fissure

Pyramidal decussation

Spinal cord

(a) Anterior view

Pons

Medulla oblongata: Regions of the brainstem

Midbrain

Diencephalon

Pons

Medulla oblongata

Figure 14.8a

14-19

Pons

Figure 14.2a


leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata

• pons – anterior bulge in brainstem, rostral to medulla

14-20

Pons• ascending sensory tracts

• descending motor tracts

• pathways in and out of cerebellum• reticular formation in pons contains additional

nuclei concerned with:– sleep, respiration, and posture

14-21

Reticular Formation• reticular formation –

loosely organized web of gray matter that runs vertically through all levels of the brainstem

• clusters of gray matter scattered throughout pons, midbrain and medulla

• occupies space between white fiber tracts and brainstem nuclei

• has connections with many areas of cerebrum


Visual input

Reticular formation

Thalamus

Radiations tocerebral cortex

Ascending generalsensory fibers

Descending motorfibers to spinal cord

Auditory input

Figure 14.10

14-22

Functions of Reticular Formation Networks

• somatic motor control

• cardiovascular control

• pain modulation

• sleep and consciousness

• habituation

14-23

Cerebellum

• the largest part of the hindbrain and the second largest part of the brain as a whole

• consists of right and left cerebellar hemispheres connected by vermis


leaves

(b) Superior view

Folia

Anterior

Posterior

Anterior lobe

Vermis

Posterior lobe

Cerebellarhemisphere

Figure 14.11b

14-24

Cerebellum

• cerebellar peduncles – three pairs of stalks that connect the cerebellum to the brainstem

– inferior peduncles – connected to medulla oblongata (input)

– middle peduncles – connected to the pons (input)

– superior peduncles – connected to the midbrain (output)


Superior colliculus


Pineal glandInferior colliculus

Mammillary bodyMidbrain

Cerebral aqueduct

Oculomotor nerve

Pons

Fourth ventricle

Medulla oblongata

Gray matter

(a) Median section

White matter(arbor vitae)

Figure 14.11a

Input and Output to

Cerebellum

14-26

Cerebellar Functions• monitors muscle contractions and aids in motor

coordination

• evaluation of sensory input– comparing textures without looking at them– spatial perception and comprehension of different views of 3D

objects belonging to the same object

• timekeeping center– predicting movement of objects– helps predict how much the eyes must move in order to

compensate for head movements and remain fixed on an object

• hearing– distinguish pitch and similar sounding words

• planning and scheduling tasks

14-27

The Forebrain

Diencephalon

Mesencephalon

TelencephalonForebrain

Pons

CerebellumMetencephalon

Spinal cord

Hindbrain

(c) Fully developed

Midbrain

Myelencephalon(medulla oblongata)


• forebrain consists of :– Thalamus– hypothalamus– cerebrum

Figure 14.4c

14-28

Thalamus

• Thalamus– nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, filters

information on its way to cerebral cortex– motor control - relays signals from cerebellum to cerebrum– memory and emotional functions of the limbic system – includes some cerebral

cortex of the temporal and frontal lobes and some of the anterior thalamic nuclei

14-29

• hypothalamus – forms part of the walls and floor of the third ventricle

– relay signals from the limbic system to the thalamus

• infundibulum – a stalk that attaches the pituitary gland to the hypothalamus

– major control center of autonomic nervous system and endocrine system

– plays essential roll in homeostatic regulation of all body systems

Hypothalamus

14-31

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

Hypothalamus

Cerebrum

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

voluntary motor actions

14-32


leaves

Thalamus

Hypothalamus

Frontal lobe

Corpus callosum

Cingulate gyrus

Optic chiasm

Pituitary gland

Mammillary body

Midbrain

Pons

Central sulcus

Parietal lobe


Occipital lobe

Pineal gland

Habenula


Cerebral aqueduct

Fourth ventricle

Cerebellum

(a)


Temporal lobe

Medullaoblongata

Figure 14.2a

14-33

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

Cerebralhemispheres

Figure 14.1a,b

Brainstem

Cerebellum

Cerebrum

Spinal cord

Rostral Caudal

Central sulcus

Lateral sulcus

Gyri

(b) Lateral view

Temporal lobe


14-34

• frontal lobe– voluntary motor functions – motivation, foresight, planning, memory, mood, emotion, social

judgment, and aggression

• parietal lobe– receives and integrates general sensory information, taste and some

visual processing

• occipital lobe– primary visual center of brain

• temporal lobe– areas for hearing, smell, learning, memory, and some aspects of

vision and emotion

• insula (hidden by other regions)– understanding spoken language, taste and sensory information from

visceral receptors

Functions of Cerebrum - Lobes

14-36

Limbic System• limbic system – center of emotion and learning

– hippocampus – in the medial temporal lobe - memory– amygdala – immediately rostral to the hippocampus - emotion

• circular patterns of feedback

14-37

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

14-38

The Electroencephalogram

• electroencephalogram (EEG) – monitors surface electrical activity of the brain waves

– useful for studying normal brain functions as sleep and consciousness– in diagnosis of degenerative brain diseases, metabolic abnormalities, brain tumors, etc.

• brain waves – rhythmic voltage changes resulting from synchronized postsynaptic potentials at the superficial layer of the cerebral cortex

– 4 types distinguished by amplitude (mV) and frequency (Hz)• persistent absence of brain waves is common clinical and legal criterion of

brain death

Figure 14.18a


© The McGraw-Hill Companies, Inc./Bob Coyle, photographer

1 second

Alpha ()

Beta ()

Delta ()

Theta ()

(a) (b)Figure 14.18b

14-39

Brain Waves

• alpha waves– awake and resting with eyes closed and mind wandering– suppressed when eyes open or performing a mental task

• beta waves– eyes open and performing mental tasks– accentuated during mental activity and sensory stimulation

• theta waves– drowsy or sleeping– if awake and under emotional stress

• delta waves– deep sleep


Sensory Homunculus

14-41


Fingers

Eye and eyelid

Tongue

Ankle

Lips

Face

JawPh

aryn

x

VocalizationSalivationMasticationSwallowing

NeckBrow

VHand

Wrist

Elb

ow

Sh

ou

lder

Tru

nk

Kne

e

Hip

Toes

IVIII

IIThumb (I)

I

II

IIIIV

V

(b)

Lateral Medial

Motor Homunculus

Figure 14.23b

Input and Output to

Cerebellum

14-43

Functional Regions of Cerebral Cortex

Wernicke area

Broca area

Primary motorcortex

Motor associationarea

Prefrontalcortex

Olfactoryassociationarea

Primary somestheticcortex

Somestheticassociation area

Primary gustatorycortex

Visual associationarea

Primaryvisual cortex

Primaryauditory cortex

Auditoryassociation area

Figure 14.21


14-44

Language• language include several abilities: reading, writing,

speaking, and understanding words assigned to different regions of the cerebral cortex

• Wernicke area– permits recognition of spoken and written language and creates

plan of speech

– when we intend to speak, Wernicke area formulates phases according to learned rules of grammar

– transmits plan of speech to Broca area

• Broca area – generates motor program for the muscles of the larynx, tongue,

cheeks and lips

– transmits program to primary motor cortex for commands to the lower motor neurons that supply relevant muscles

14-45

Language CentersCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

leavesPrecentral gyrus

Anterior Posterior

Speech center ofprimary motor cortex

Primary auditorycortex(in lateral sulcus)

Postcentralgyrus

Angulargyrus

Primaryvisual cortex

Wernickearea

Brocaarea

Figure 14.25

Directional Terms and Landmarks · Cerebrum - Gross Anatomy • two cerebral hemispheres divided by...

Documents

Transcript of Directional Terms and Landmarks · Cerebrum - Gross Anatomy • two cerebral hemispheres divided by...