Ch 15 brain

•Cerebrum

•Diencephalon

•Brainstem

•Cerebellum

•Gyri: folds

•Sulci: depressions between folds

•Anterior (rostral): toward the nose

•Posterior (caudal): toward the tail

•Prosencephalon (forebrain)

•Mesencephalon (midbrain)

•Rhombencephalon (hindbrain)

•Telencephalon: from prosencephalon; forms cerebrum

•Diencephalon: from prosencephalon; forms thalamus, hypothalamus, and epithalamus

•Mesencephalon: only primary vesicle that does not form a new secondary vesicle

•Metencephalon: from rhombencephalon; forms pons and cerebrum

•Myelencephalon: from rhombencephalon; forms medulla oblongata

motor neuron and interneuron cell bodies, dendrites, telodendria, unmyelinated axons

•Forms cerebral cortex, surface of most of adult brain

•Within white matter, gray deep clusters of neuron cell bodies called cerebral nuclei

•Made up of myelinated axons

•Deep to the gray matter

•Bony cranium

•Protective connective tissue (meninges)

•CSF

•Blood–brain barrier

Cranial meninges are connective tissues

•Separating brain from bones of cranium

•Protecting blood vessels of brain; form some large veins that drain blood from brain

•Containing and circulating cerebrospinal fluid

•Pia mater: thin, innermost layer adhering to brain

•Subarachnoid space is area between arachnoid and pia

•Arachnoid mater: has web of fibers called arachnoid trabeculae

•Dura mater: tough outer layer with two sublayers

•Deeper meningeal layer (superficial to subdural space)

•More superficial periosteal layer

•Layers usually fused except where they separate to form dural venous sinuses

The meningeal layer extends into cranial cavity at four locations to form double-layered dura called cranial dural septa:

-partition the brain and provide support

•Falx cerebri: projects into longitudinal fissure; separates left and right cerebral hemispheres

•Tentorium cerebelli: horizontal fold that separates cerebrum from cerebellum

•Falx cerebelli: separates left and right cerebellar hemispheres

•Diaphragma sellae: small septum between pituitary and hypothalamus

form in locations where the two layers of the dura mater have separated:

1.Superior sagittal sinus: located within the superior margin of the falx cerebri

2.Inferior sagittal sinus: located within the inferior margin of the falx cerebri

3.Transverse sinuses: located within the posterior border of the tentorium cerebelli

4.Occipital sinus: located in the posterior vertical border of the falx cerebelli

cavities within brain that contain cerebrospinal fluid (CSF)

•Two lateral ventricles, one in each cerebral hemisphere, separated by a thin septum pellucidum

•A third ventricle in diencephalon

-Communicates with lateral ventricles through interventricular foramen

-Communiates with fourth ventricle through cerebral aqueduct

•A fourth ventricle between pons and cerebellum

-Merges with central canal of spinal cord

clear liquid that circulates in ventricles and subarachnoid space

•Buoyancy: brain “floats” in the CSF

•Protection: provides liquid cushion

•Environmental stability: transports nutrients and removes waste from brain

Formed by the choroid plexus in each ventricle

•Composed of a layer of ependymal cells and the capillaries that lie within the pia mater

•Blood from capillaries is filtered to form CSF

1)CSF is produced by the choroid plexus in the ventricles.

2)CSF flows from the lateral ventricles, through the interventricular foramen into the third ventricle, and then through the cerebral aqueduct into the fourth ventricle.

3)CSF in the fourth ventricle passes through the paired lateral apertures or the single median aperture, and into the subarachnoid space as well as the central canal of the spinal cord.

4)As the CSF flows through the subarachnoid space, it provides buoyancy to support the brain.

5)Excess CSF flows into the arachnoid villi, then drains into the dural venous sinuses. The greater pressure on the CSF in the subarachnoid space ensures that CSF moves into the dural venous sinuses without permitting venous blood to enter the subarachnoid space.

regulates what substances can enter interstitial fluid of brain

Capillary endothelial cells, astrocyte perivascular feet, and continuous basement membrane contribute to the BBB

•Choroid plexus (because the capillaries must be permeable to make CSF)

•Hypothalamus (hormones are made that need ready access to blood)

•Pineal gland (hormones are made that need ready access to blood)

conscious thought and intellectual functions

•Contains many neurons for complex, analytical functions

-Contains an outer cortex, inner white matter, and deep regions of gray matter called cerebral nuclei

- gyri (ridges), sulci (grooves), and deep fissures

cerebral hemispheres

longitudinal fissure that extends along the midsagittal plane

corpus callosum

The two hemispheres appear to be mirror images but display some functional differences

Both cerebral hemispheres generally receive their sensory information from and project motor commands to the opposite sides of the body

Some functions, such as memory or consciousness, cannot easily be assigned to a single region

1.Frontal lobe

2.Parietal lobe

3.Temporal lobe

4.Occipital lobe

5.Insula

Frontal lobe is located deep to the frontal bone and forms anterior part of cerebral hemisphere

•Ends posteriorly at central sulcus; inferior border marked by lateral sulcus

•includes Precentral gyrus anterior to central sulcus

•Frontal lobe functions: voluntary movement, concentration, verbal communication, decision making, planning, and personality

superoposterior part of each hemisphere and is under parietal bone

•Terminates anteriorly at the central sulcus, laterally at the lateral sulcus, and posteriorly at the parieto-occipital sulcus

•includes Postcentral gyrus(posterior to central sulcus)

-general sensory functions

inferior to lateral sulcus, under the temporal bone

•Involved with hearing and smell

posterior region of each hemisphere underneath occipital bone

•Processes incoming visual information and stores visual memories

deep to the lateral sulcus

•Involved in interoceptive awareness, emotion, empathy, taste

•Motor areas: control voluntary motor functions

•Sensory areas: provide conscious awareness of sensation

•Association areas: integrate and store information

(somatic motor area) controls voluntary skeletal muscle activity

•Located within precentral gyrus; axons project contralaterally to brainstem and spinal cord

diagrammed as a motor homunculus on the precentral gyrus

(Broca area) controls muscular movements for vocalization

•Located in most individuals within the inferolateral portion of the left frontal lobe

Frontal eye field helps control and regulate eye movements

•Located on superior surface of middle frontal gyrus, immediately anterior to premotor cortex

located within the postcentral gyrus

•This area receives general somatic sensory information from touch, pressure, pain, and temperature receptors

•Sensory homunculus

Primary visual cortex processes visual information; located in occipital lobe

Primary auditory cortex processes auditory information; located in temporal lobe

Primary gustatory cortex processes taste information; located in insula

Primary olfactory cortex provides awareness of smell; located in temporal lobe

coordinates skilled motor activities

•Located in frontal lobe just anterior to precentral gyrus

integrates and interprets sensory information

•Located in parietal lobe just posterior to post central gyrus

Auditory association area interprets characteristics of sound and stores memories of sound

•Located in temporal lobe, posteroinferior to primary auditory cortex

Visual association area processes visual information

•Located in occipital lobe, surrounding primary visual cortex

recognizes and comprehends spoken and written language

•Typically located in left hemisphere overlapping the parietal and temporal lobes

Direct complicated analytical functions or complex motor activity

- speech, cognition, understanding spatial relationships, and general interpretation

Housed in both cerebral hemispheres

deep to cortical gray matter

Composed primarily of myelinated axons

connect areas within one hemisphere

•Arcuate fibers within a lobe

•Longitudinal fasciculi connect different lobes of same hemisphere

•connect two hemispheres

connect cerebrum to lower areas (e.g., spinal cord)

(basal nuclei) are masses of gray matter located deep within brain’s white matter

Specific cerebral nuclei include:

•Caudate nucleus—helps coordinate walking

•Amygdaloid body—participates in emotional expression

•Lentiform nucleus—involved in movement and muscle tone

-Composed of putamen and globus pallidus

•Claustrum—consciousness and processing of multiple sensory stimuli

•Epithalamus

•Thalamus

•Hypothalamus

partially forms posterior roof of diencephalon and covers third ventricle

Components include:

•Pineal gland: secretes melatonin, a hormone that regulates circadian rhythm

•Habenular nuclei: relays signals from limbic system to midbrain; involved in visceral and emotional responses to odor

Paired masses of gray matter on each side of third ventricle

•These masses are connected by the midline interthalamic adhesion

Each mass is composed of about a dozen thalamic nuclei with axons projecting to regions of cerebral cortex

-Sensory impulses except olfaction

•Main relay point for sensory information that will be projected to somatosensory cortex

is the anteroinferior region of diencephalon

Thin, stalklike infundibulum extends inferiorly from hypothalamus to attach to pituitary gland

Specific nuclei control various functions in body:

•Master control of the autonomic nervous system

•Master control of the endocrine system

•Regulation of body temperature

•Control of emotional behavior, food intake, water intake

•Regulation of sleep–wake (circadian) rhythms

connects forebrain and cerebellum to spinal cord

•Passageway for all tracts between cerebrum and spinal cord

Contains many autonomic and reflex centers required for survival

Houses nuclei of many of the cranial nerves

superior portion of brainstem

Nuclei of oculomotor nerve (CN III) and trochlear nerve (CN IV)

Somatic motor axons descend from primary motor cortex through cerebral peduncles to spinal cord

extends through midbrain and connects third and fourth ventricles

•Surrounded by periaqueductal gray matter

connect cerebellum to midbrain

between substantia nigra and periaqueductal gray; relays information between cerebrum and cerebellum

produce dopamine; involved in motor control, emotion, pleasure, and pain

•Degeneration of substantia nigra=Parkinson’s disease

visual and auditory reflex centers

Pons is bulging region on anterior brainstem

Middle cerebellar peduncles are transverse fibers that connect pons to cerebellum

Contains autonomic nuclei in pontine respiratory center that help regulate breathing

Houses sensory and motor cranial nerve nuclei for trigeminal (CN V), abducens (CN VI), and facial (CN VII) nerves

Superior olivary complex nuclei receive auditory input and help localize sound source

most inferior part of brainstem

Pyramids are composed of motor projection tracts called the corticospinal tracts

•Most axons in pyramids cross midline at decussation of the pyramids

Contains inferior olivary nucleus that relays proprioceptive information to cerebellum

•Inferior cerebellar peduncles connect medulla to cerebellum

Contains nucleus cuneatus and nucleus gracilis which relay somatic sensory information to thalamus

•Cardiac center: regulates heart rate and its strength of contraction

•Vasomotor center: controls blood pressure by regulating contraction and relaxation of smooth muscle in walls of arterioles

•Medullary respiratory center: regulates respiratory rate

•Other nuclei involved in coughing, sneezing, salivation, swallowing, gagging, and vomiting

second largest part of brain

Partitioned into three regions:

•Outer gray matter layer of cerebellar cortex

•Internal region of white matter, called the arbor vitae

•Cerebellar nuclei in deepest layer

Cerebellum has left and right cerebellar hemispheres

•Each hemisphere has an anterior and posterior lobe

•A narrow vermis sits on midline between hemispheres

Folds called folia

coordinates and fine-tunes movements

Stores memories of previously learned movement patterns

Adjusts muscle activity to maintain equilibrium and posture

Uses proprioceptive information from muscles and joints and to regulate the body’s position

•Monitors position of each body joint and its muscle tone

•Superior cerebellar peduncles: connect midbrain to cerebellum

•Middle cerebellar peduncles: connect pons to cerebellum

•Inferior cerebellar peduncles: connect medulla oblongata to cerebellum

cerebral and diencephalic structures that form a ring around the diencephalon

-process and experience emotions

-Affects memory formation through integration of past memories of physical sensations with emotional states

•Cingulate gyrus: ridge superior to corpus callosum; brings emotions into consciousness

•Parahippocampal gyrus: tissue associated with hippocampus (functions in memory)

•Hippocampus: nucleus shaped like a seahorse; essential in consolidating long-term memories

•Amygdaloid body: involved in emotion, especially fear; helps sort and code memories based on how they are emotionally perceived

•Olfactory bulbs, olfactory tract, olfactory cortex: odors can provoke emotions/memories

•Fornix: thin tract of white matter connecting hippocampus with other limbic structures

•Various nuclei in diencephalon also contribute to emotional function

Twelve pairs Roman numerals

Some only motor or sensory; mixed nerves)

The motor components of a cranial nerve may be somatic motor and/or parasympathetic motor in function

olfactory

Sensory

smell

Damage: anosmia (loss smell)

optic

Sensory

Vision

damage: anopsia (visual defect)

oculomotor

Motor

Four extrinsic eye muscles (medial rectus, superior rectus, inferior rectus, inferior oblique); levator palpebrae superioris muscle (elevates eyelid)

-pupil constrict;

damage: ptosis eyelid droop, strabismus(eye not parallel)

trochlear

Motor

Superior oblique eye muscle

damage:strabismus(eye not parallel), diplopia double vision

trigeminal

Both

-General sensory from anterior scalp, nasal cavity, nasopharynx, entire face, most of oral cavity, teeth, anterior two-thirds of tongue; part of auricle of ear; meninges

-Muscles of mastication, mylohyoid, digastric (anterior belly), tensor tympani, tensor veli palatini

damage:trigeminal neuralgia pain

abducens

Motor

Lateral rectus eye muscle

damage: paralysis of lateral rectus limits, diplopia double vision

facial

Both

-Taste from anterior two-thirds of tongue

-Muscles of facial expression, digastric (posterior belly), stylohyoid, stapedius

-secretion from silva and tears

damage: decrease tears, dry mouth, bell palsy

vestibulocochlear

Sensory

Hearing (cochlear branch); equilibrium (vestibular branch)

damage:loss of balance, nausea

glossopharyngeal

Both

-General sensory and taste to posterior one-third of tongue, general sensory to part of pharynx, visceral sensory from carotid bodies

-One pharyngeal muscle (stylopharyngeus)

-Increases secretion from parotid salivary gland

damage:dry mouth, lost of taste posterior 1 third of tongue

vagus

Both

-Visceral sensory information from heart, lungs, most abdominal organs

General sensory information from external acoustic meatus, tympanic membrane, part of the pharynx, laryngopharynx, and larynx

-Most pharyngeal muscles; laryngeal muscles

-Innervates smooth muscle and glands of heart, lungs, larynx, trachea, most abdominal organs

damage: larynx issue, hoarseness, monotone, lost voice, swallowing

accessory

Motor

Trapezius muscle, sternocleidomastoid muscle

damage: difficult to elevate shoulder

hypoglossal

Motor

Intrinsic tongue muscles and extrinsic tongue muscles

damage: swallowing and speech difficulties

•Cingulate gyrus: ridge superior to corpus callosum; brings emotions into consciousness

•Parahippocampal gyrus: tissue associated with hippocampus (functions in memory)

nucleus shaped like a seahorse; essential in consolidating long-term memories

involved in emotion, especially fear; helps sort and code memories based on how they are emotionally perceived

odors can provoke emotions/memories

thin tract of white matter connecting hippocampus with other limbic structures

•Pia mater: thin, innermost layer adhering to brain

area between arachnoid and pia

has web of fibers called arachnoid trabeculae

tough outer layer with two sublayers

•Deeper meningeal layer (superficial to subdural space)

•More superficial periosteal layer

•Layers usually fused except where they separate to form dural venous sinuses