• Brain: nerve cells & support cells
• Reflexes integrated
• hormones produced
• integration of all sensory info
• 15% of cardiac output
• glucose for energy (taken directly, does not req insulin)

• Right & Left cerebral hemispheres 
• Diencephalon: core of brain

• Largest part of the brain, outer shells of cerebral hemispheres
• Organized horizontally by fxn, vertically into layers
• Makes sense of environment
• initiates thought and goal-oriented behavior
• Controls thought processes (i.e memory & learning) and motor functions (i.e walking)
• Contains Gray matter, 1° and 2° sensory areas
• Different lobes perform different fxns

• i.e limbic system
• Receive info from 1 and 2 sensory areas, and from other parts of cortex and subcortex
• Allow complex movements, interpretation and production of language, appropriate responses to people and social situations (personality)

- The cerebral cortex forward from the central sulcus and above lateral sulcus
- Contains motor and premotor areas

- Broca's area (left)

- Goal-orientated behavior

- moral decision making

- complex thought

- modifies emotional surges from limbic system (primitive urges)

- stimuli from brain in  motor area send projections to spinal cord: Corticospinal tract

- motor neurons cross sides at level of the brain stem

• controls Expression of speech
• Located in left frontal lobe

• projections from the motor area of the brain down the contralateral side of the brain stem
• decussation occurs at the medulla
• Motor info form left side of cerebral cortes passes down right side of spinal cord and control motor movements of right side of body, and vice versa

• Axons from the motor area that run outside the cortiocospinal tract to the spinal cord
• EPS pathways
• Fine motor movements
• damage to this area causes tremor or clumsiness (ie Parkinson's or Huntington Dz)
• Mainly through the Basal Ganglia

• Behind central sulcus, above lateral fissure, and back to parietooccipital fissure
• contains the sensor strip 
• 1° sensory area of the brain for touch and hearing
• act as 2° association area to interpret incoming stimuli
• forms our body image and controls visual-spatial relations
• passes sensory info on to many other areas of the brain

• Posterior lobe of cerebral cortex
• Posterior to parietal lobe, above parietooccipital fissure, divides it from cerebellum
• 1° visual association center of cortex
• info from retina
• Cortico blindness = damage here

• Cerebral cortex down from lateral fissure; posterior to parietooccipital fissure
• 1° association area for auditory info
• Includes Wernickes area
• interpretation of smell
• important for storage of memory
• left arterial temporal lobe: site of artistic abilities

• located in the temporal lobe
• interpretation of language:
• Receptive language: understanding what you hear and say or what you read and write

• Relay station: 1st processing area for sensory info into the brain
• All areas that contain "Thalamus"

• Main part of the diencephalon
• Receives all incoming sensory info
• relays info thru afferent tracts to all of cerebral cortex
• descending fibers from cerebral cortex
• Motor neurons travel down to thalamus
• part of reticular activating system (RAS)
• Receives Pain info; relays to cerebral cortex

controls sleep-awake cycles (arousal)

• makes up base of diencephalon
• both endocrine and neural
• maintains homeostasis
• integrated info re: temp, hunger, ANS
• activity, emotional status
• regulates hormone levels (esp. pituitary hormones)

• Functional structures
• Islands of gray matter: in diencephalon
• process and influence info in EPS tracts
• control highly skilled movements (that are based on patterns and quick response without intentional thought: baseball player, ballerina, piano playing)
• Includes: caudate nucleus, putamen, globus pallidus
• all projections to and from basal ganglia to thru thalamus

• repetitive movements, grimaces and tremors (Huntington's dz and parkinsons dz)
• Movement abnormalities 

• Diffuse grouping of neurons from different areas of brain (ie, amygdala, hippocampus, mammillary body, fornix, thalamus, hypothalamus...) 
• assoc with production of emotions 
• learning and behavior also influenced

• Made up of: Pons, medulla oblongata & mesencephalon (midbrain)
• controls cardiovascular and respiratory systems, breathing and consciousness 
• Neuron pass thru and carry motor info, controlling equilibrium
• Problems here affect both sides of the body
• CN 10/12 leave here

• Branch of small neurons thru brainstem
• both ascending and descending tracts
• tracts cluster to form centers
• Control: swallowing, vomiting, respiratory and cardiovascular reflexes
• Essential for: wakefulness, and focus attention
• If damaged= coma

• RAS sends info to higher brain areas to maintain wakefulness and arousal
• Functional not anatomical 
• RAS stimulated by ALL sensory stimulation, including pain (ie can be woken up by smells)

• Under control of RAS
• active process when brainstem inhibitory signals arrive at neurons in RAS
• 2ary to serotonin release from reticular formation
• Inhibits RAS firing, ending conscious behavior

• In hindbrain posterior to brainstem
• controls muscle co-ordination and balance
• Smooth skeletal muscle response; grace and direction to voluntary movement (not as fine as EPS)
• Controls fast, repetitive movements (Typing, biking, piano) (without use of forebrain)

• Disrupts fluid movements and postures
• Causes disorders of gait (ataxia), abnormal speech (dysarthria) and eye movements (nystagmus), hypotonia, tremors, clumsiness of movements
• Evaluate by listening to patients speech and gait

• Aka vertebral column
• from base of skull to sacrum
• filled with CSF
• Bony column protects delicate nerves inside
• Spinal cord: interneurons whose axons travel up & down (to around L2)

• Sensory neruons
• Carry Sensory info to CNS from all sensory organs, pressure and volume receptors, temperature receptors, stretch receptors and pain receptors
• enter at each level of the spinal cord on the dorsal (back): Dorsal roots

• Motor neurons
• Deliver neural stimulation to muscles and glands
• leave each level of the cord on the ventral (front) side: ventral roots
• Belong to autonomic or somatic NS

• 31 pairs
• mixed nerve containing both sensory and motor fibers 
• formed by the joining of the dorsal and ventral roots outside the spinal cord

• Thin, fluid filled membranes surrounding brain and spinal cord
• 3 meninges:
  • Dura matter (outside)
  • Arachnoid (middle)
  • Pia matter (immediately over brain, goes into all sulci and fissures)

• Clear fluid that surrounds the brain and open spaces in the brain  
• Circulates in ventricles and in the subarachnoid space (beneath arachnoid, above pia matter)
• Nourishes and provides cushion
• formed from plasma that flows thru brain
• electrolytes and glucose different from plasma

• Epidural: above dura matter
• Subdural: below dura matter
• Both contain many small blood vessels
• Damage to blood vessels = blood in spaces

• Very dangerous, pts can die very quickly
• Shaped like a football

[image]

• Have more time to correct and shaped more convex than an epidural bleed

• CSF continuously recirculated over and thru CNS
• If ventricle pathways blocked, fluid builds up from blockage, and pressure increases either inside or on surface of the brain
• If ICP is ↑ do NOT do lumbar puncture
• ↑ with ↑ in cranial blood, CSF or tissue (tumor)
• Visualized via:  CT - ventricles will shrink/disappear, mid line shift will be apparent; Fundoscope -papilledema
• Intercranial HTN = large increase
• if ICP reaches systemic MAP, blood flow to brain stops: death

• P inside cranium
• Determined by volume of blood in brain, the volume of CSF and volume of brain tissue
• Normal: 5-15mmHg

• made up of nerves traveling between the brain or spinal cord and the rest of the body
• Divided into afferent (sensory) and efferent (motor) divisions
• Travel together in opposite directions
• includes cranial nerves 3-12
• 2 divisions: somatic and automonic

Peripheral Nervous System  

↓                      ↓

   Somatic division        Autonomic Division

                                  ↓              ↓

                                        Parasympathetic     Sympathetic

• Autonomic: Innervates involuntary muscles and glands. Motor neurons: 1st motor neuron synapses in ganglion, 2nd one goes to muscle/gland
• Somatic: Innervates voluntary skeletal muscle       Motor neruons: 1st motor neuron goes directly to muscle

[image]

• Leave Spinal cord and innervate smooth and cardiac muscle & endocrine and exocrine glands
• Involuntary
• 2 divisions: Sympathetic & Parasympathetic
  • Innervate many of the same organs
  • often cause opposite responses 

• Short Preganglionic fibers exit from thoracic or lumbar regions of spinal cord (release Ach)
  • Synapses within a ganglia with a 2nd nerve: post-ganglionic fiber
• Post ganglionic neuron travels to target organ, muscle or gland 
  • Releases Norepiniphrine to adrenergic receptor

• Leave brain in cranial nerves or leave spinal cord from sacrum
• Preganglionic fiber is Long, releases acetylcholine to stimulate post-ganglionic fiber (close to target)
• Post-ganglionic fiber travels to target tissue, muscle or gland and releases Acetylcholine 

• for sympathetic and parasympathetic fibers
• Nicotinic receptors

• for parasympathetic fibers
• muscarinic receptors

• heart (Increases HR and strength of contractions)
• large & small arteries & veins (constriction of all vessels except arterioles supplying skeletal muscle)
• Smooth muscle of GI (↓ motility)
• Smooth muscle of respiratory tract (bronchial relaxation, decreased secretions)
• Affects liver
• stimulates secretions of sweat glands
• ejaculation during male orgasm

• Heart (slows HR)
• Gut (↑ motility)
• bronchial smooth muscle (airway constriction)
• G/U tract (erection in male)

• Made up of efferent motor neurons
• Leave brain or spinal cord and synapse directly on skeletal muscle cells (no ganglia)
• Release acetylcholine at neuromuscular junction

• support nerve cells
• provide nutrients 
• form insulated coating (myelin)
• clear away cell debris
• CNS: examples
  • neuroglia (more of these than actual nerve cells)
  • Astrocytes: nutrients
• Peripheral NS: examples
  • Schwann cells: nutrients, produce myelin

• Example: from lacunar stroke
• Alterations in consciousness: dullness, confusion, lethargy, eventually stupor (difficult to arouse)

• deepening of stupor state (as seen with diencephalon dysfunction)
• dysfunction of medulla & pons
  •  Coma
  • progressive ↓ in consciousness: rostral-caudal progression

• Intact brainstem needed for eyes to:
  • dilate or constrict
  • rapidly and equally

Can change pupil size and reacivity

Pinpoint pupils: damage from opiate (heroin) OD (may be reversed by naloxone)
Fixed & Dilated: severe hypoxia (often irreversible)

Fixed pupils: Barbiturate OD

Fixed B/L in mid-position: brainstem injury

• Steady eyes at rest
• Intact cerebral cortex controlling brainstem

• Loss of cortical function: eyes ROVE and move together toward or away from the side of injury (depending on injury type)

loss of ocular movement (eyes fixed) 

-eyes move with head

• one eye up and one down
• compressive injury to brainstem

• Used to determine if brainstem is functioning
• Place a drop of ice water in pts ear
• In cortical injury but functioning brainstem: eyes will move slow to ice water, fast away
  • indicates functioning brainstem
  • if eyes do not do this = brainstem injury

rhythmic, regular breathing pattern

• CO₂ Dependent breathing: post-hyperventilation apnea
• respirations stop until CO₂ builds up to a threshold, causing hyperventilation (↑ in rr)
• When CO₂ removed, respiration stop again
• Cheyne-Stokes breathing

• Respiratory center over-responsive to CO₂: Crescendo breathing until a certain CO₂ level reached
• Then, rate & depth ↓ smoothly (decrescendo breathing) until apnea reached
• indicates damage to cerebral hemispheres: often metabolically induced coma

A = Cheyne Stokes respirations: cerebral damage or metabolic disorders

B = Central neurogenic hyperventilation: lesions of brainstem tegmentum

C= Apneusis: damage at pontine level (eg basilar artery occlusion)

D = Cluster breathing

E= ataxic breathing: completely irregular pattern associated with lesions of ht lower pontine tegmantum and medulla

• Abnormal motor responses: inappropriate or absent responses to painful stimuli 
• Higher brain center damage: Brainstem reflexes (sucking, grasping) will occur
• Brain Damage: flexion & rigidity of limbs
• Abnormal brain function: 
  • Hyperkinesia (↑ muscle movements)
  • Hypokinesia (↓ muscle movements)
  • Paresis (muscle weakness)
  • paralysis (loss of motor function)

• loss of cerebral cortex functioning but NOT loss of brainstem functioning
• Flexion of upper extremities at elbows and external rotation and extension of lower extremities
• unilateral or bilateral

[image]

• Sever injury to higher brain centers AND brainstem
• Rigid extension of limbs and neck

• Impariment of language comprehension or production
• usually form cerebral hypoxia
• often associated with stroke
• can be from trauma or infection
• usually involves Left cerebral hemisphere (Right involved with some who are left handed)

• Damage in Left Frontal Lobe Broca's area
• Understand language OK
• ability to meaningfully express words in speech or writing is impaired
• Expressive dysphasia
• Ex: Pt asked to touch nose will do so, but will not be able to express how they can touch their nose

• Damage to Wernicke's area in Left Temporal lobe
• Verbal expression of language is OK
• Understanding of spoken or written work impaired
• Receptive dysphasia
• Ex: pt asked to touch nose will not be able to b/c will not understand what you are asking 

• Failure to recognize object b/c of inability to make sense of incoming sensory stimuli
• may be visual, auditory, tactile, taste or smell
• Damage to 1° or assoc. sensory area in cerebral cortex

• Irreversible loss of functioning of cerebral hemisphere
• person unresponsive to environment
• persistent vegetative state
• Consciousness lost, but brainstem and cerebellum function intact
• Respiration, cardiovascular control, body temp, brainstem reflexes (yawning, grasping, sucking) intact
• Sleep-wake cycle will be followed (pt can open eyes)
• no conscious perception

• Similar to cerebral death
• no sleep-wake cycle
• no opening of eyes

• Irreversible loss of cerebral hemisphere, brainstem and cerebellum function
• Lost: consciousness, respiration, cardiovascular and temp control function
• No sleep-wake cycle
• EEG flat

• a pt cannot be legally discontinued from life support without a living will unless brain death is established
• There are 6 steps that need to be followed 

• Slow process
• loss on intellectual functioning without loss of arousal or vegetative functioning
• Affected: memory, general knowledge, abstract thought, judgment, interpretation of written and spoken language
• Cause: infection, drugs, trauma, neuro-degenerative, biochemical disturbance and metabolic imbalance
• Some dementia reversible
• other types (Alzheimer's): progressive, irreversible 

• Large increase in ICP
• can be seen via CT or fundoscopic exam (b/l papilledema) 
• Causes compression of neurons and capillaries in brain

• Common
• Occur with: straining with stool, coughing, sneezing

• ↑ ICP
  
• infection/inflammation (stimulates capillary blood flow and increases capillary permeability)
• Bacterial toxins
• Severe HTN (>200): filtration of plasma into interstitial space
• Bleeding: 2° to head trauma, burst aneurysm, hemorrhagic stroke

• Compensation is eventually no longer effective
• There are 4 stages in response to >ICP

• increase in 1 of 3 volumes in brain (blood, CSF, Tissue) compensated for by ↓ in one or both of other volumes
• Compensation: ICP near normal
• usually ↓ CSF production or ↑ CSF reabsorption
• followed by venous constriction to ↑ blood flow out of brain
• Usually only subtle behavioral changes (drowsiness, confusion)

• Volume continues to ↑
• ICP ↑ significantly
• Progression of tumor or continued bleeding from cut artery
• Brain constricts cerebral arteries
• causes cerebral hypoxia/ hypercapnea (↑ CO₂)
• Brain fxn deteriorates
• ↓ level of consciousness
  
• alterations in breathing patterns (Cheyen-Stokes)
• pupillary changes

• Cerebral arteries dilate reflexively and blood volume ↑
• ICP goes up
• "Decompensation"
• Volume-pressure curve develops so small changes in volume cause large ↑ in pressure
• arterioles and capillaries compressed
• neural cells damaged
• Pronounced ↓ consciousness, altered respiratory patter, loss of pupillary reflexes
• Brain senses worse hypoxia and hypercapnea: ↑ MAP to ↑ its own oxygenation
• ↑ in BP increases ICP
  
• Brain cells destroyed at a faster rate
• Cerebral blood flow slows
• Consciousness, brainstem reflexes lost

• As swelling and P in one compartment of brain become high, herniation of brain into another compartment occurs
• When ICP reaches mean systolic P, cerebral profusion stops

• Osmotic diuretics (mannitol)
• Steroids (decrease inflammation)
• Measure cerebral perfusion P accurately (directly)

• EMG
• EEG
• MRI
• CT
• PET 
• U/S

• Measure peripheral nerve fxn
• record electrical activity of motor nerve-muscle cell unit
• Used to diagnose, describe, monitor neuromuscular pathology

• Measure electrical activity in brain thru electrodes on the scalp
• Picks up unusual brain wave signals
• Indicates brain damage of seizure activity
• Cannot localize damage

• Imaging of choice for most neuro conditions
• Tissue structure and integrity can be seen clearly
• Contraindications: foreign objects in eye, pacemakers, metal protheses 

• X-ray beam rotated around pt, and passes thru tissue from multiple directions
• Pictures recreated by computer to give 3D representation of brain structure
• Contrast media may be injected before Xrays to improve fine detail of structures
• rapid eval of emerging neuro conditions
• detects acute hemorrhage (without contrast)
• good for visualization of bone
• less detailed than MRI
• used when MRI is contraindicated 

• IV injection or inhalation of a positron-emitting isotope 
• followed by sequential radiographs of the skull that monitor the decay of the isotope in tissues that take up the label
• Study distribution of a particular substance in the brain
• anatomically map brain and determine blood flow patterns
• Watch while person performs task to ID involved areas
• ID and monitor therapy progression in MS and Parkinson's 

• Use reflected sound to measure blood flow velocity
• Helps to assess cerebral blood flow when evaluating cerebrovascular dz
• Often used in surgery to study vascular blockage