Functions of the nervous system:

1) Integration of body processes

2) Control of voluntary effectors (skeletal muscles), and mediation of voluntary reflexes.

3) Control of involuntary effectors (  smooth muscle, cardiac muscle, glands) and mediation of autonomic reflexes (heart rate, blood pressure, glandular secretion, etc.)

4) Response to stimuli

5) Responsible for conscious thought and perception, emotions, personality, the mind.

1. Automatic control (sensory) of respiration is in - brainstem (midbrain) 

2. Behavioral/voluntary control is in - the cortex

3. Alveolar ventilation -the amount of atmospheric air that actually reaches the alveolar per breath and that can participate in the exchange of gasses between alveoli and blood

4. Only way to increase gas exchange in alveolar capillaries - perfusion-limited gas exchange 

5. Pulmonary ventiliation not effected by - concentration of bicarbonate ions

6. Central chemoreceptors - medulla -  CO2, O2 and H+ concentrations

7. Peripheral chemoreceptors - carotid and aortic bodies- PO2, PCO2 and pH 

8. Major stimulus for respiratory centers - arterial PCO2 

9. Rhythmic breathing depends on 
1. continuous (tonic) inspiratory drive from DRG (dorsal respiratory group)
2. intermittent (phasic) expiratory input from cerebrum, thalamus, cranial nerves and ascending spinal cord sensory tracts

10. Primary site for gas exchange - type I epithelial cells for alveoli

HEART DISORDERS

1. Pump failure => Alters pressure (flow) =>alters oxygen carrying capacity.
   1. Renin release (Juxtaglomerular cells) Kidney
   2. Converts Angiotensinogen => Angiotensin I
   3. In lungs Angiotensin I Converted => Angiotensin II
   4. Angiotensin II = powerful vasoconstrictor (raises pressure, increases afterload)
      1. stimulates thirst
      2. stimulates adrenal cortex to release Aldosterone
         (Sodium retention, potassium loss)
      3. stimulates kidney directly to reabsorb Sodium
      4. releases ADH from Posterior Pituitary
2. Myocardial Infarction

    

   1. Myocardial Cells die from lack of Oxygen
   2. Adjacent vessels (collateral) dilate to compensate
   3. Intracellular Enzymes leak from dying cells (Necrosis)
      1. Creatine Kinase CK (Creatine Phosphokinase) 3 forms
         1. One isoenzyme = exclusively Heart (MB)
         2. CK-MB blood levels found 2-5 hrs, peak in 24 hrs
         3. Lactic Dehydrogenase found 6-10 hours after. points less clearly to infarction
      2. Serum glutamic oxaloacetic transaminase (SGOT)
         1. Found 6 hrs after infarction, peaks 24-48 hrs at 2 to 15 times normal,
         2. SGOT returns to normal after 3-4 days
   4. Myocardium weakens = Decreased CO & SV (severe - death)
   5. Infarct heal by fibrous repair
   6. Hypertrophy of undamaged myocardial cells
      1. Increased contractility to restore normal CO
      2. Improved by exercise program
   7. Prognosis
      1. 10% uncomplicated recovery
      2. 20% Suddenly fatal
      3. Rest MI not fatal immediately, 15% will die from related causes
3. Congenital heart disease (Affect oxygenation of blood)
   1. Septal defects
   2. Ductus arteriosus
   3. Valvular heart disease
      1. Stenosis = cusps, fibrotic & thickened, Sometimes fused, can not open
      2. Regurgitation = cusps, retracted, Do not close, blood moves backwards

Structure of a nerve:

A peripheral nerve is arranged much like a muscle in terms of its connective tissue. It has an outer covering which forms a sheath around the nerve, called the epineurium. Often a nerve will run together with an artery and vein and their connective coverings will merge. Nerve fibers, which are axons, organize into bundles known as fascicles with each fascicle surrounded by the perineurium. Between individual nerve fibers is an inner layer of endoneurium.

 The myelin sheath in peripheral nerves consists of Schwann cells wrapped in many layers around the axon fibers. Not all fibers in a nerve will be myelinated, but most of the voluntary fibers are. The Schwann cells are portrayed as arranged along the axon like sausages on a string. Gaps between the Schwann cells are called nodes of Ranvier. These nodes permit an impulse to travel faster because it doesn't need to depolarize each area of a membrane, just the nodes. This type of conduction is called saltatory conduction and means that impulses will travel faster in myelinated fibers than in unmyelinated ones.

The myelin sheath does several things:

1) It provides insulation to help prevent short circuiting between fibers.

2) The myelin sheath provides for faster conduction.

3) The myelin sheath provides for the possibility of repair of peripheral nerve fibers. Schwann cells help to maintain the micro-environments of the axons and their tunnel (the neurilemma tunnel) permits re-connection with an effector or receptor  CNS fibers, not having the same type of myelination accumulate scar tissue after damage, which prevents regeneration.

1) Storage - the stomach allows a meal to be consumed and the materials released incrementally into the duodenum for digestion. It may take up to four hours for food from a complete meal to clear the stomach. 
2) Chemical digestion - pepsin begins the process of protein digestion cleaving large polypeptides into shorter chains . 
3) Mechanical digestion - the churning action of the muscularis causes liquefaction and mixing of the contents to produce acid chyme. 
4) Some absorption - water, electrolytes, monosaccharides, and fat soluble molecules including alcohol are all absorbed in the stomach to some degree.

Functional Divisions of the Nervous System:

1) The Voluntary Nervous System - (ie. somatic division) control of willful control of effectors (skeletal muscles) and conscious perception. Mediates voluntary reflexes.

2) The Autonomic Nervous System - control of autonomic effectors - smooth muscles, cardiac muscle, glands. Responsible for "visceral" reflexes