Ch 14 bio1191

How brain contribute to homeostasis

receiving sensory input, integrating information, making decisions, and executing motor responses

Cranial bones

skull

Cranial meninges

Dura, Arachnoid, PIa

Dura Mater

Periosteal layer: Outer layer attached to the inside of the skull

Meningeal layer: Inner layer faces the brain

When these are seperated they form venous sinuses

Venous sinuses

Channels that drain blood and CSF away from the brain

Falx cerebri

Seperates the right and left cerebrum

Falx cerebelli

seperates the right and left cerebellum

Tentorium cerebelli

Seperates the cerebrum and cerebellum

Blood flow to brain

Internal carotid and vertebral arteries

Blood flow away from brain to heart

Dural venous sinuses drain into internal jugular veins

What happens when the brain is deprived of oxygen

weakening, permanent damage, or death of brain cells.

What happens when the brain is deprived of glucose

confusion, dizziness, convulsions, and unconsciousness.

fMRI

When neuron and neuroglia activity increases in a brain region, blood flow to that area also increases

Tight Junctions in BBB

seal endothelial cells tgt which acts like a wall for brain capillaries

Basement membrane in BBB

surrounds endothelial cell (second layer underneath)

Astrocytes in BBB

press up against capillaries – secrete substances that maintain the tight junctions

Blood Brain Barrier (BBB)

Lipid-soluble easy (O2, CO2, alc, nic, caffeine, anesthesia), Water soluble (glucose), most ions transported slowly, big nope

Cerebrospinal Fluid functions

Mechanical Protection – absorbs shock and protects the delicate tissues of the CNS from jolts • Also buoys the brain so it floats in the cranium

Chemical Protection - optimal chemical environment for neuronal signaling (ions!)

Circulation - medium for exchange of nutrients and waste products between blood and nervous tissue

Formation of Cerebrospinal Fluid

Produced in choroid plexuses

Choroid Plexuses

Capillaries covered by ependymal cells

CSF structure

Colourless liquid which is mainly water, contains glucose, ions (Na, Cl), lil bit O2, few WBC

Ependymal cells and making CSF

Filters blood plasma, lets mostly water, dissolved ions, lil bit of protein, and cells thru

Reabsorption of CSF

CSF is absorbed by Aracnoid Granulation, which it then dumps it into the venous sinus to return to blood stream, disposing of it

Hydrocephalus

Blockage of drainage of CSF (tumour,
inflammation, developmental malformation,
meningitis, hemorrhage or injury)

Pyramid (Med oblon)

Control voluntary movement of lumbs and trunk

Nuclei of Medulla func

1. Cardiovascular center: heart rate, diameter of blood vessels

2. Respiratory: breathe rhythm

3. Reflex: cough sneeze, swallow vomit hiccup

Pons

Consists of both nuclei and tracts, the “bridge” that connects parts of brain, help breathing, contains cranial nerves V-VIII

Midbrain

Contains sensory tracts, motor tracts and nuclei (visual and auditory info)

Cerebral peduncles

Contain corticospinal (Cortex → spinal cord), corticopontine (cortex → pons) and corticobulbar (cortex → medulla) motor axons

Tectum superior colliculi

Reflex centers for visual activities (e.g. tracking a moving object, scanning stationary images)

Tectum inferior colliculi

Part of auditory pathway • Relay impulses from receptors for hearing in ear to thalamus – Reflex center for startle reflex

Substantia nigra

Realse dopamine, helps control subcoscious muscle activity, loss of this = parkinsons

Red Nuclei

rich in blood supply, axons from cortex and cerebellum synapse coordinate precise voluntary muscular movements

Nuclei white or gray

gray

Reticular activating system (RAS)

alerts cerebral cortex to sensory signals (like sound, flashlight, BUT NOT SMELL) to awake from sleep, regulate consciousness, stimuli from ear eye skin muscle. COMA IF DAMAGE

Cerebellum structure

10% of brain weight, 50% of neurons in brain

ataxia

loss of ability to coordinate movements damage to cerebellum