brain anatomy

Central Nervous System (CNS)

� CNS – composed of the brain and spinal cord

� Cephalization

� Elaboration of the anterior portion of the CNS

� Increase in number of neurons in the head

� Highest level is reached in the human brain

I take

exception to

The Brain

� Surface anatomy includes cerebral hemispheres,

cerebellum, and brain stem

Embryonic Development

� During the first 26 days of development:

� Ectoderm thickens forming the neural plate

� The neural plate invaginates, forming the neural folds

� Superior edges fuse forming neural tube which detaches

from the ectoderm and sinks deeper

� Neural tube differentiates into the CNS

� Brain forms from neural tube (rostrally) as well as spinal

cord (posterior/dorsally)

� Neural crest cells give rise to some neurons destined to

reside in ganglia

Embryonic Development

Figure 12.1

Brain Development: Primary Brain Vesicles

� The anterior end of the neural tube expands and

constricts to form the three primary brain vesicles

� Prosencephalon – the forebrain

� Mesencephalon – the midbrain

� Rhombencephalon – hindbrain

� Remainder of neural tube becomes the spinal cord

Neural Tube and Primary Brain Vesicles

Figure 12.2a, b

Secondary Brain Vesicles

� In week 5 of embryonic development, secondary

brain vesicles form

� Telencephalon and diencephalon arise from the

forebrain

� Mesencephalon remains undivided

� Metencephalon and myelencephalon arise from the

hindbrain

Secondary Brain Vesicles

Figure 12.2c

Adult Brain Structures

� Fates of the secondary brain vesicles:

� Telencephalon – cerebrum: cortex, white matter,

and basal nuclei

� Diencephalon – thalamus, hypothalamus, and

epithalamus

� Mesencephalon – brain stem: midbrain

� Metencephalon – brain stem: pons

� Myelencephalon – brain stem: medulla oblongata

Adult Neural Canal Regions

Figure 12.2c, d

� Adult structures derived from the neural canal

� Telencephalon – lateral ventricles

� Diencephalon – third ventricle

� Mesencephalon – cerebral aqueduct

� Metencephalon and myelencephalon – fourth

ventricle

Figure 12.2c, e

Space Restriction and Brain Development

Figure 12.3

Space Restriction and Brain Development

� Flexures: midbrain and cervical, which bend the

forebrain toward the brain stem

� Cerebral hemispheres: grow posteriorly and

laterally and envelop the diencephalon and

midbrain

� Continued growth causes the surface to crease

and fold producing convolutions thus increasing

the surface area

Basic Pattern of the Central Nervous System

� Spinal Cord

� Central cavity surrounded by a gray matter core

� External to which is white matter composed of myelinated fiber tracts

� Brain

� Similar to spinal cord but with additional areas of gray matter

� Cerebellum has gray matter in nuclei

� Cerebrum has nuclei and additional gray matter in the cortex

Basic Pattern of the Central Nervous System

Figure 12.4

Ventricles of the Brain

� Continuous with one another and with the central canal of the spinal cord

� Filled with cerebrospinal fluid and lined with ependymal cells

� C-shaped reflects the pattern of cerebral growth

� Septum pallucidum separates lateral ventricles via the interventricular foreamen

� Third ventricle connected to the fourth ventricle via the cerebral aquaduct

� Fourth ventricle is continuous with the central canal of the spinal cord

� Fourth ventricle is also continuous with the fluid filled space surrounding the brain (subarachnoid) via lateral and medial apertures.

Ventricles of the Brain

Figure 12.5

Cerebral Hemispheres

� Form the superior part of the brain and make up 83% of its mass

� Contain ridges (gyri) and shallow grooves (sulci)

� Contain deep sulci called fissures

� Are separated by the longitudinal fissure

� Transverse fissure separates the cerebral hemispheres from the cerebellum

� Have three basic regions: cortex, white matter, and basal nuclei

Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere

� Prominent sulci divide the hemispheres into five

lobes:

� Frontal, parietal, temporal, occipital, and insula

� These are named for the cranial bones under which

they lie

� Central sulcus – separates the frontal and parietal

lobes.

� Bordered by the precentral gyrus (anteriorly)

and the postcentral gyrus (posteriorly)

Brain Lobes

Figure 12.6a–b

Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere

� Parieto-occipital sulcus – separates the parietal and

occipital lobes

� Lateral sulcus – outlines the temporal lobe and

separates the parietal and temporal lobes

� Insula: buried within the lateral sulcus and forms

part of the floor of the cerebral hemispheres

Cerebral Cortex: Our “conscious mind”

� The cortex – superficial gray matter; accounts for

40% of the mass of the brain.

� Gray matter: neuron cell bodies, dendrites,

associated glia, blood vessels

� It enables sensation, communication, memory,

understanding, and voluntary movements

� Each hemisphere acts contralaterally (controls the

opposite side of the body)

� Cerebral cortex has been extensively mapped

Functional Areas of the Cerebral Cortex

� The three types of functional areas are:

� Motor areas – control voluntary movement

� Sensory areas – conscious awareness of sensation

� Association areas – integrate diverse information

� All neurons here are interneurons not sensory & motor

neurons

� Each hemisphere is chiefly concerned with the sensory and

motor functions of the opposite side of the body

� Each side has specialization and is not necessarily bilateral

Figure 12.8a

Figure 12.8b

Cerebral Cortex: Motor Areas (Voluntary Movement)

� Lie in the posterior part of the frontal lobes:

� Primary (somatic) motor cortex

� Premotor cortex

� Broca’s area

� Frontal eye field

Primary Motor Cortex (Brodmman’s Area #4)

� Located in the precentral gyrus of the

frontal lobe of each hemisphere

� Pyramidal cells:

� allow conscious control of

precise, skilled, voluntary

movements.

� Their long axons project into the

spinal cord forming the massive

pyramidal tracts (corticospinal

tracts)

Primary Motor Cortex (Brodmman’s Area #4)

� The entire body is represented spatially in the

primary motor cortex of each hemisphere (this

type of mapping is called somatotopy)

Premotor Cortex (Brodmman’s Area #6)

� Located anterior to the precentral gyrus in the frontal lobe

� Controls learned, repetitious, or patterned motor skills

� Coordinates movement by sending impulses to the primary

motor cortex

� Involved in the planning of movements

� Controls voluntary movements that depend on sensory feedback

Broca’s Area: Brodmann Area #44 & 45

� Broca’s area

� Located anterior to the inferior region of the premotor area

� Present in one hemisphere (usually the left)

� A motor speech area that directs muscles of the tongue

� Is active as one is planning to speak

Frontal Eye Field: Brodmann’s Area #8

� Frontal eye field

� Located anterior to the premotor cortex and

superior to Broca’s area

� Controls voluntary eye movement

Sensory Areas

� Primary somatosensory cortex

� Somatosensory association cortex

� Visual and auditory areas

� Olfactory, gustatory, and vestibular cortices

Sensory Areas

Figure 12.8a

Primary Somatosensory Cortex: Brodmann’s Area #1-3

� Located in the postcentral gyrus of parietal lobe

� Receives info. from sensory receptors in the skin and

proprioceptors in the skeletal muscles, joints, tendons

� Neurons identify the body region being stimulated (spatial

discrimination)

Primary Somatosensory Cortex: Brodmann’s Area #1-3

� Body is represented

spatially: contralaterally

and upside down

� The amount of sensory

cortex devoted to a given

body region is related to

the degree of sensitivity

in that region, and not the

body size (e.g. face, lips,

fingertips)

Somatosensory Association Cortex: Brodmann’s Areas 5 &7

� Located posterior to the primary somatosensory cortex

� Integrates sensory information relayed from the primary

somatosensory cortex to produce an understanding of the object

being felt

� Determines size, texture, and relationship of parts

Visual Areas: Brodmann’s Areas 17-19

� Primary visual (striate) cortex

� Seen on the extreme posterior tip of the occipital lobe

� Most of it is buried in the calcarine sulcus

� Receives visual information from the retinas

� Visual association area

� Surrounds the primary visual cortex

� Interprets visual stimuli (e.g., color, form, and movement)

Auditory Areas: Brodmann’s Areas 41-43

� Primary auditory cortex

� Located at the superior margin of the temporal lobe

� Receives information related to pitch, rhythm, and volume

� Auditory association area

� Located posterior to the primary auditory cortex

� Stores memories of sounds and permits perception of sounds

� Wernicke’s area

Olfactory Cortex: Brodmann’s Areas: 28 & 34

� Located in the medial aspect of the temporal lobe dominated by

the uncus

� Afferent fibers from smell receptors in the superior nasal

cavities send impulses along olfactory tracts and relay them to

the olfactory cortex

� The O.C. is part of the primitive rhinencephalon

…and the other corteces

� Gustatory cortex (located in the insula)

� Deep to the temporal lobe

� Taste

� Visceral sensory area (also in the insula)

� Located just posterior to the gustatory cortex

� Perception of visceral sensations

� Vestibular (equilibrium) cortex

� Located in the posterior part of the insula

� Balance

Multimodal Association Areas

� Information flows from sensory neurons to

� Primary sensory cortex to

� Sensory association cortex to

� Multimodal association cortex

� Gives meaning to the information

� Stores it in memory

� Decision making area

� Relay decisions to premotor cortex and then the motor

cortex

Prefrontal Cortex (Anterior Association Area)

� Located in the anterior portion of the frontal lobe

� Most complicated cortical region

� Involved with intellect, cognition, recall, and

personality

� Necessary for judgment, reasoning, persistence,

and conscience

� Matures slowly, dependent on positive/negative

feedback

Posterior Association Area

� Region encompassing parts of: temporal, parietal,

and occipital lobes

� Involved in recognizing patterns, surroundings,

bringing different sensory inputs into a whole

� Brings conscious attention to an area in space or to

an area of one’s own body

� Problems here can result in a smelly, half naked

Language Areas

� Located in a large area surrounding the left (or language-dominant) lateral sulcus

� Major parts and functions:

� Wernicke’s area –sounding out unfamiliar words

� Broca’s area – speech preparation and production

� Lateral prefrontal cortex – language comprehension and word analysis

� Lateral and ventral temporal lobe – coordinate auditory and visual aspects of language

Lateralization of Cortical Function

� Lateralization – each hemisphere has abilities not shared

with its partner

� Cerebral dominance – designates the hemisphere dominant

for a given task

� Left hemisphere – controls language, math, and logic

� E.g. Dad buys half a cow for conversation sake

� Right hemisphere – controls visual-spatial skills, emotion,

and artistic skills

� Most “righties” are left cerebral dominant, while most

“south paws” are right cerebral dominant.

Cerebral White Matter

� Located deep to the cortical grey matter

� It is responsible for communication between the

cerebral cortex and lower CNS center, and within

areas of the cerebrum

� Consists of deep myelinated fibers and their large

tracts

Cerebral White Matter

� Tracts are classified according to the direction in which they run

� Types include:

� Commissures – connect corresponding gray areas of the two hemispheres.

� E.g. corpus collosum

� Fibers run horizontally

� Association fibers – connect different parts of the same hemisphere

� E.g. connect adjacent gyri

� Long fibers can connect different cortical lobes

� Fibers run horizonatally

� Projection fibers – enter the hemispheres from lower brain or cord centers

� Tie the cortex to the rest of the nervous system and to the body’s receptors and effectors

� E.g. corona radiata: fan like projection of fibers from the brain stem to the cortex

� Fibers run vertically

Fiber Tracts in White Matter

Figure 12.10a

Basal Nuclei

� Masses of gray matter found deep within the

cortical white matter

� The corpus striatum (striped appearance) is

composed of three parts

� Caudate nucleus

� Lentiform nucleus – composed of the putamen and

the globus pallidus

� Fibers of internal capsule running between and

through caudate and lentiform nuclei

Basal Nuclei

Figure 12.11a

Basal Nuclei

Figure 12.11b

Functions of Basal Nuclei

� Nuclei of the corpus striatum receive input from

the entire cerebral cortex

� The basal nuclei project signals to the premotor

and prefrontal cortices (logic and reasoning of a

movement and how to best execute it)

� And influences muscle movements

(subsequently directed by the primary motor

cortex)

� Precise function of basal nuclei is still elusive

Diencephalon

� Central core of the forebrain

� Surrounded by the cerebral hemispheres

� Consists of three paired structures – thalamus,

hypothalamus, and epithalamus

� Encloses the third ventricle

Diencephalon

Figure 12.12

Thalamus

� Paired, egg-shaped masses that form the

superolateral walls of the third ventricle

� Connected at the midline by the intermediate mass

� Contains four groups of nuclei – anterior, ventral,

dorsal, and posterior

� Nuclei project and receive fibers from the cerebral

cortex

� Thalamus, thyroid, thymus

Thalamus

Figure 12.13a

Thalamic Function

� Afferent fibers from all senses and all parts of the body

converge and synapse in the thalamus

� Impulses of similar function are sorted out, edited, and

relayed as a group (e.g. “The Hot Bowl of Soup”)

� All inputs ascending to the cerebral cortex pass through the

thalamus

� Mediates sensation, motor activities, cortical arousal,

learning, and memory

� Thalamus is the “gateway” to the cerebral cortex

Hypothalamus

� The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis).

� Located below the thalamus, it caps the brainstem and forms the inferolateral walls of the third ventricle

� Extends from the optic chiasma to the posterior margin of the mammillary bodies

� Main visceral control center of the body

� Vital for homeostasis

Hypothalamus Associated Structures

� Mammillary bodies

� Small, paired nuclei bulging anteriorly from

the hypothalamus

� Involved with recognition memory

� Relay station for olfactory pathways

� Infundibulum – stalk of the hypothalamus; connects

to the pituitary gland

Hypothalamic Nuclei

Figure 12.13b

Hypothalamic Function

� Autonomic control center: controls autonomic nervous system.

� Regulates cardiac and smooth muscle

� Regulates gland secretion

� Influences blood pressure, heartbeat rate, digestive tract motility, eye pupil size

� Emotional response center

� Center for pleasure, fear, rage

� Body temperature regulation

� Sweating, shivering

� Regulation of food intake

� Regulates the feeling of hunger and satiation

� Regulation of water balance and thirst

� Regulates release of antidiuretic hormone causing kidneys to retain water

� Regulates sleep wake cycle

Endocrine Functions of the Hypothalamus

� Releasing hormones control secretion of hormones

by the anterior pituitary gland

� E.g. The supraoptic and paraventricular nuclei

produce ADH and oxytocin

Epithalamus

� Most dorsal portion of the diencephalon; forms

roof of the third ventricle

� Pineal gland – extends from the posterior border

and secretes melatonin

� Melatonin – a hormone involved with sleep

regulation, sleep-wake cycles, and mood

Epithalamus

Figure 12.12

Brain Stem

� Consists of three regions – midbrain (mesencephalon), pons, and medulla oblongata

� Similar to spinal cord but contains embedded nuclei

� Controls automatic behaviors necessary for survival

� Provides the pathway for tracts between higher and lower brain centers

� Associated with 10 of the 12 pairs of cranial nerves

Human Brain: Ventral Aspect

Figure 12.14

Brain Stem

Figure 12.15a

Brain Stem

Figure 12.15b

Brain Stem

Figure 12.15c

Midbrain (Mesencephalon)

� Located between the diencephalon and the pons

� Midbrain structures include:

� Cerebral peduncles – two bulging structures that

contain pyramidal motor tracts descending toward

the spinal cord

� Cerebral aqueduct – hollow tube that connects the

third and fourth ventricles

� Various nuclei

Midbrain Nuclei

� Corpora quadrigemina – four domelike protrusions

of the dorsal midbrain (superior and inferior

colliculi)

� Superior colliculi: visual reflex centers

� Inferior colliculi: auditory relay (startle reflex)

Midbrain Nuclei

� 2 pigmented nuclei:

� Substantia nigra – pigmented from melanin

� Precursor of dopamine released here. Disorders here, e.g.

Parkinson’s disease

� Red nucleus – largest nucleus of the reticular formation

� Controls some movements of the shoulder & upper arm

� Red coloration due to high degree of vascularization

� Bulging brainstem region between the midbrain and the medulla

oblongata

� Forms part of the anterior wall of the fourth ventricle

� Formed of tracts coursing in 2 directions

� Deep projections: connect higher brain centers and

spinal cord

� Superficial projections relay between the motor cortex

of the cerebrum and the cerebellum

Medulla Oblongata

� Most inferior part of the brain stem

� Along with the pons, forms the ventral wall of the

fourth ventricle

� Contains a choroid plexus of the fourth ventricle

� Pyramids – two longitudinal ridges formed by

corticospinal tracts

� Decussation of the pyramids – crossover points of

the corticospinal tracts

Medulla Oblongata

Figure 12.16c

Medulla Nuclei

� Inferior olivary nuclei – gray matter that relays

sensory information on the state of stretch of

muscles and joints to the cerebellum

� Cochlear nuclei: auditory relays

� Vestibular nuclear complex – synapses that

mediate and maintain equilibrium

� Nucleus gracilis and caneatus: where somatic

sensory information ascends from the spinal cord

to the somatosensory cortex

Medulla Nuclei

� Involved in autonomic reflex center involved in

homeostasis

� Cardiovascular control center – adjusts force

and rate of heart contraction

� Respiratory centers – control rate and depth of

breathing

� Additional centers – regulate vomiting,

hiccuping, swallowing, coughing, and sneezing

The Cerebellum

� Located dorsal to the pons and medulla

� Protrudes under the occipital lobes of the cerebrum

� Makes up 11% of the brain’s mass

� Provides precise timing and appropriate patterns of

skeletal muscle contraction subconsciously

� E.g. coordination

The Cerebellum

Figure 12.17b

Anatomy of the Cerebellum

� Two bilaterally symmetrical hemispheres connected medially by the vermis

� Contains folia – transversely oriented gyri

� Fissures subdivide each hemisphere into three lobes – anterior, posterior, and flocculonodular

� Neural arrangement – gray matter cortex, internal white matter, scattered nuclei

� Arbor vitae – distinctive treelike pattern of the cerebellar white matter

Cerebellar Peduncles

� Three paired fiber tracts that connect the cerebellum to the brain stem

� All fibers in the cerebellum are ipsilateral

� Superior peduncles connect the cerebellum to the midbrain

� Middle peduncles connect the pons to the cerebellum

� Inferior peduncles connect the medulla to the cerebellum

Cerebellar Processing

� Cerebellum receives impulses of the intent to

initiate voluntary muscle contraction

� Proprioceptors and visual signals “inform” the

cerebellum of the body’s condition

� Cerebellar cortex calculates the best way to

perform a movement

� A “blueprint” of coordinated movement is sent to

the cerebral pre-motor cortex

brain anatomy

pearson education

brain developmentfigure

brain stemcopyright

benjamin cummingsi

brain development flexures

primary brain vesiclesfigure

cns brain forms

benjamin cummingsneural

Documents

anatomy of human brain

columbia intro psych--brain anatomy columbia intro...

brain anatomy - wou

cns brain anatomy pics

brain gross anatomy

segment 1 brain anatomy

anatomy brain

basic brain anatomy

the brain anatomy

2020 mlstroke brain anatomy and functional anatomy

the human brain: anatomy, functions, and injury · brain...

brain anatomy: cerebellum

brain anatomy hemispheres

the human-brain-anatomy

the human brain: anatomy, functions, and injury. main menu...

surface anatomy of brain

brain anatomy powerpoint template

the human brain: anatomy, functions, and...

guide to brain anatomy

the human brain anatomy,