CNS: The BRAIN HA&P

Male – 3.5 lbs; Female – 3.2 lbs

Brain mass: body mass is equal!

Embryonic Development 3 weeks old – neural plate

forms from ectoderm , and invaginates to form neural grove which deepens to form the neural tube by week four

Neural tube sinks deeper away from ectoderm and differentiates into brain anteriorly and spinal cord develops caudally

Central cavity of neural tube enlarges to form ventricles

Embryonic Brain Development

Space Restriction on Brain Development

Flextures develop bending forbrain towards brain stem

Cerebral hemispheres grow posteriorly and laterally enveloping diencephalon & midbrain

By 26th week cerebral hemispheres form convolutions to increase SA (more neurons to occupy limited space)

Regions of the Brain Cerebral Hemispheres

Longitudinal fissure seperates R/L Hemisperes

4 Lobes: Frontal, Parietal, Occipital, and Temporal

Motor, Sensory, and Cognitive Functions

Diencephelon Thalmus, Hypothalmus, and

Epithalmus Brain Stem

Medulla Oblongata, Pons, Midbrain Cerebellum

Subconscious coordinated movement and agility

Protection of the Brain

Bone Meninges

3 connective tissue membranes

Protect bv Contain CSF

Cerebral spinal Fluid (CSF) Blood Brain Barrier

Meninges Dura Mater (tough mother)

2 layers of strong fibrous connective tissue Periosteal layer connects to periosteum of

skull Subdural space

Arachnoid (spider) Middle loose brain covering Subarchnoid space

w/weblike extensions that attach to the pia mater Filled w/CSF Large bv to brain

Pia Mater (gentle mother) Delicate connecctive tissue Rich w/tiny bv Clings to brain following convolutions

What is meningitis?

A. Inflammation of meninges

B. Bacterial or viral infection

C. Diagnosed by a lumbar spinal tap

D. All of the aboveInflammation of m

eninges

Bacteria

l or v

iral in

fection

Diagnose

d by a lu

mbar ...

All of t

he above

25% 25%25%25%

Cerebral Spinal Fluid Liquid Cushion from blows and

trauma Buoyancy reduces brain weight by

97%! Provides nourishment (similar to

blood plasma) Abundant Na+, Cl-, H+, Less Ca2+

and K+ Formed by choroid plexus

(clusters of cappillaries) @ roof of ea/ventricle (ependymal cells)

Adults – 500mL produced daily, 150mL replaced ea/8 hrs

Removes waste products Circulates through ventricles to

central canal of spinal cord and subarachnoid space

Ventricles Continues w/ea other & central canal of spinal

cord Lateral ventricles (pair) 3rd ventricle 4th ventricle Cerebral aquaduct

Blood-Brain Barrier Maintains stable environment for the

brain Capillaries are the least permeable in

the body (tight junctions) Selective

Glucose, a.a., some electrolytes move by facilitated diffusion

Bloodbourne metabolic wastes, proteins, some toxins, and most drugs are denied entry

Ineffective against fats, fatty acids, O2, CO2, alcohol, nicotine, anesthetics

Incomplete in newborn and premature Lack of brain barrier in hypothalmus

and brain stem (moniter blood, toxins, and vomiting reflex!)

The ___________ is the outermost meninx, and forms supportive and protective partitions between some portions of the brain.

A. Dura materB. ArachnoidC. Pia materD. VentriclesE. Blood brain

barrier

Dura mater

Arachnoid

Pia mater

Ventricle

s

Blood brain barri

er

20% 20% 20%20%20%

Cerebral Hemispheres

83% of total brain mass! Gyri – elevated ridges Sulci – shallow grooves Fissures – deep grooves Anatomical landmarks divide cerebrum into 5 lobes

Longitudinal fissure Transverse cerebral fissure Central sulcus Lateral sulcus

Each hemisphere has 3 regions Cortex – superficial gray matter Internal white matter Basal nuclei – islands of gray matter deep within white

matter

Cerebral Cortex Conscious mind Gray matter: neuron somas,

dendrites, glia, and bv 2-4 mm but 40% of brain mass due

to convolutions Billions of neurons in 6 layers Ea/hemisphere is concerned

w/sensory & motor functions of opposite side of body

Divided into localized domains w/specific functions Motor – control voluntary movements Sensory – conscious awareness of

sensation Association – receiving input from

multiple senses and sending output to multiple areas (complex connections)

Motor Areas Primary motor cortex

Precentral gyrus of frontal lobe of ea/hemisphere Skilled voluntary movements of skeletal muscles

Premotor cortex Anterior to precentral gyrus Learned motor skills of patterned nature (playing

a musical instrument) Coordinates several muscle groups

Broca’s area Anterior to inferior region of premotor area Usually only in left hemisphere Motor speech area (directs muscles used in

speech) Frontal eye field

Anterior to premotor cortex and superior to Broca’s area

Controls voluntary movements of eyes

Sensory Areas Primary Somatosensory cortex

Postcentral gyrus of parietal lobe Receive information from sensory receptors in skin Neurons identify body region being stimulated

(opposite sides of body correlate w/hemispheres) Somatosensory Association cortex

Posterior to primary somatosensory cortex Integrates sensory inputs to understand object

being felt Visual Areas

Extreme posterior tip of occipital lobe & buried deep in medial occipital lobe

Receives visual info from retina of eye Auditory Areas

Superior margin of temporal lobe

Sensory Areas cont’d Olfactory Cortex

Medial aspect of temporal lobe Olfactory tracts from superior nasal cavities

Gustatory Cortex Insula (deep to the temporal lobe) Perception of taste

Visceral Sensory Area Cortex of insula posterior to gustatory cortex Stomach pains, full bladder, lungs bursting, etc…

Vestibular (equilibrium) cortex Posterior region of insula, deep to temporal lobe Awareness of balance and your place in space

Multimodal Association Areas Anterior association area

AKA pre-frontal cortex (frontal lobe) Intellect, cognition, recall, personality, abstract ideas Judgement, reasoning, persistence & planning Matures slowly

Posterior association area Large region of temporal, parietal, and occipital lobes Recognizing patterns, faces Wernicke’s Area – understanding written and spoken

language Limbic association area

Cingulate gyrus, parahippocampal gyrus, and hippocampus

Emotional impact & memories

Are you Left or Right Brained?

Lateralization of Cortical Functioning Both cerebral hemispheres are used for almost

every activity, however there is some division of labor

90% of people have left hemisphere dominance Meaning left hemisphere has greater control over

language abilities, math and logic And the right hemisphere is associated with intuition,

emotion, artistic and musical skills, poetic, creative, and far better at recognizing faces

Typically right handed 10% of people the roles of hemispheres is

reversed or shared equally Typically left handed and male

Cerebral White Matter Responsible for communication

between cerebral areas and between cerebral cortex and lower CNS centers

Myelinated fibers bundled into large tracts Commissures

connects gray areas of two hemispheres (horizontal)

Corpus Callosum –largest (superior to lateral vesicles)

Association Fibers Connect different parts of same

hemisphere (horizontal) Projection Fibers

Connect cortex to bodys receptors and effectors

vertical

Diencephalon Central Core of forebrain

3 paired structures Thalmus Hypothalamus Epithalmus

Thalamus 80% of diencephalon Large number of

nuclei Gateway to cerebral

cortex Afferent impulses

from all senses converge

Information is sorted and relayed to appropriate area of cortex

Crude recognition as pleasant or unpleasant

Hypothalamus

Below the thalamus, above brain stem

Extends from optic chiasma to mammilary bodies (nuclei that relay olfactory pathways)

Infundibulum connects to pituitary gland

Visceral control center of body, vital for homeostatic control

Homeostatic Roles of Hypothalamus ANS

Influences hr, bp, pupils, etc Emotional response (limbic system)

Perception of pleasure, fear, rage, and sex drive Body Temperature regulation

Monitors & initiates sweating or shivering Regulation of food intake

response to changes in blood glucose/a.a., hormones Regulation of water balance and thirst

Response to concentrations of bodily fluids Regulation of sleep wake cycles

In response to light (visual) cues Endocrine system functioning

Controls secretions of pituitary gland Produces hormones ADH and oxytocin

Epithalamus Dorsal portion of

diencephelon, roof of 3rd ventricle

Pineal gland extends from posterior border

Helps regulate sleep wake cycle

Brain Imaging Compare PET, fMRI, CAT, EEG, cerebral

angiography

Brain Stem Survival Behaviors Pathway for fiber tracts Innervation of the head 3 parts:

Midbrain Descending motor tracts Cerebral aqueduct (connects 3rd & 4th ventricles Visual reflex centers Sound (startle)reflex

Pons Bulging region Deep tracts connect brain and spinal cord Superficial fibers connect motor cortex and cerebellum Help medulla maintain breathing rhythm

Medulla Oblongata

Medulla Oblongata Motor cortex fibers cross over to opposite side

of body before spinal cord Relay sensory information Auditory relays Maintains equilibrium Autonomic reflex center

Force and rate of heart contraction Vasomotor center Rate and depth of breathing Vomiting, hiccupping, swallowing, coughing,

sneezing

Cerebellum

11%of total brain mass Dorsal to pons & medulla Using input from cerebral motor

cortex and sensory receptors provides precise timing of skeletal muscle contraction subconsciously Smooth coordinated movements Agility

Brain Activities:1. Limbic System2. Reticular Formation3. Sleep4. Language5. Memory6. Brain wave patterns and EEG

Each group will create a brief (8 ppt slides) presentation w/pictures on their assigned brain topic of interest! You may use textbooks or internet, be sure to cite sources!

Cranial Nerves