The brainAnatomy & Physiology

Brain: unremarkable appearance ~ 3 lbs 4 major regions

right & left connected by large fiber tract: corpus callosum

cover most of other 3 parts surface: elevated ridges = gyri separated by shallow grooves = sulci

Fissures deeper grooves separate regions of brain

1. Cerebral Hemisphere

Gyri, Sulci, & a Fissure

separates cerebral hemispheres other fissures separate brain into lobes

Longitudinal Fissure

spaces in brain filled with CSF

connected to subarachnoid space (around brain & spinal cord) and central canal of spinal cord

Ventricles of the Brain

parietal lobe posterior to central sulcus

receives impulses from sensory receptors (not special senses), interprets them◦pain recognition◦temperature◦light touch

Somatic Sensory Area

Humunculus

anterior to central sulcus in frontal lobe

major voluntary motor tract

Primary Motor Area

Humunculus

visual area

Occipital Lobe

auditory & olfactory areas

Temporal Lobe

Brocca’s Area: ability to speak◦@ base of precentral gyrus (usually only

on left side)◦injury inability to correctly vocalize

words

Frontal Lobe

Frontal Lobotomy

http://www.youtube.com/watch?v=_0aNILW6ILk

Frontal Lobotomy

http://www.youtube.com/watch?v=c6kRP41ygrI

Phineas Gage

anterior frontal lobe: higher intellectual reasoning

complex memories: frontal/ temporal lobe

all facets of speech: occipital/temporal/parietal lobes

Lobe Functions

Gray Matter of the Brain

gray matter in brain that is NOT in cerebral cortex

functions: help regulate voluntary motor activity by modifying instructions sent to skeletal muscle by primary motor cortex

Basal Nuclei

Parkinson’s Huntington’s

Imbalances in Basal Nuclei

2. Diencephalon

sits atop brain stem enclosed by cerebral hemispheres major parts:

◦Thalamus◦Hypothalamus◦Limbic system◦Epithalamus

Diencephalon

relay station for sensory impulses passing thru to sensory cortex

Thalamus

ANS center role in:

◦temperature control◦water balance◦metabolism

Hypothalamus

Limbic System: forms rim surrounding corpus callosum

regulates autonomic & endocrine functions in response to emotional stimuli (“reacting” brain vs. cerebral cortex being “thinking” brain)◦set level of arousal◦motivation◦reinforcing behaviors◦rage, love, memory, empathy

Limbic System

~size of thumb in diameter & ~ 3 inches long

3 parts:1. midbrain2. pons3. medulla oblongata

Brain Stem

knots of capillaries w/in each ventricle

produce & secrete CSF (cerebral spinal fluid)

Choroid Plexus

smallest, uppermost part of brain stem

cerebral aquaduct: tiny canal that runs thru midbrain connecting 3rd & 4th ventricles

contains reflex centers for vision, hearing

Midbrain

Midbrain

“bridge” rounded structure that protrudes below midbrain

contains apneustic (produces deep, prolonged inspirations) & pneumotatic center (inhibits inspiration)

Pons

most inferior part of brain stem inferior border merges into spinal cord

centers: heart rate, BP, breathing, swallowing, vomiting

Medulla Oblongata

large, cauliflower-like projects dorsally from under occipital lobe

2 hemispheres convoluted surface provides precise timing for skeletal muscle activity

controls balance & equilibrium

Cerebellum

Head injuries are leading cause of accidental death in USA.

Concussion: dizziness, “see stars”, briefly lose consciousness; No permanent brain damage

Contusion: result of marked tissue damage. Cerebrum: may maintain consciousness Brainstem: coma

Cerebral Edema: swelling of brain due to inflammatory response to injury/ initially conscious neuro signs deteriorate (think edema or hemorrhage)

Traumatic Brain Injuries

stroke 3rd leading cause of death in USA occur when blood circulation to brain is interrupted ◦vessel could be blocked (temporary or

permanent) or hemorrhaging

Cerebrovascular Accident(CVA)

CVA characterized by:

◦abrupt onset of persisting neurological symptoms that arise from destruction of brain tissue

common causes:◦ intracerebral hemorrhage◦emboli◦atherosclerosis of cerebral arteries

CVA Risk Factors1. hypertension2. hypercholesterolnemia3. heart disease4. narrowed carotid arteries5. hx of TIAs (transient ischemic attacks)6. diabetes7. smoking8. obesity9. excessive alcohol intake

CVA Treatments Thrombolytic:

◦clot-dissolving drug: tissue plasminogen activator (t-PA) greatly improved prognosis for CVA

◦aspirin (makes plts slippery fewer clots)◦blood thinners

Aphasia: from damage to left side cerebrum where language centers are

Motor Aphasia:◦damage to Broca’s area◦loss of ability to speak

Sensory Aphasia:◦loss of ability to understand written or

spoken word

Sequelae of CVA

Transient Ischemic Attack “mini-stroke” due to temporary restriction of blood flow

symptoms last 5 – 50 minutes “red flags” that warn impending & more serious CVAs

TIA

Alzheimer Disease (AD) most common type of dementia >10% population > age 65 4th leading cause of death in US characterized by progressive loss of

reasoning & ability to care for oneself cause of most cases unknown but…

◦genetic factors◦environmental or lifestyle factors◦normal aging process

AD Pathology