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

Conductivity :

 Means ability of cardiac muscle to propagate electrical impulses through the entire heart ( from one part of the heart to another)  by the excitatory -conductive system of the heart.
 
Excitatory conductive system of the heart involves:

1. Sinoatrial node ( SA node) : Here the initial impulses start and then conducted to the atria through  the anterior inter-atrial pathway ( to the left atrium) , to the atrial muscle mass through the gap junction, and to the Atrioventricular node ( AV node ) through anterior, middle , and posterior inter-nodal pathways.
The average conductive velocity in the atria is 1m/s.

2- AV node : The electrical impulses can not be conducted directly from the atria to the ventricles , because of the  fibrous skeleton , which is an electrical isolator , located between the atria and ventricles. So the only conductive way is the AV node . But there is a delay in the conduction occurs in the AV node .
This delay is due to:
- the smaller size of the nodal fiber.
- The less negative resting membrane potential
- fewer gap junctions.

There are three sites for delay:
- In the transitional fibers , that connect inter-nodal pathways with the AV node ( 0.03 ) .
- AV node itself ( 0.09 s) .
- In the penetrating portion of Bundle of Hiss ( 0.04 s)  .
This delay actually allows atria to empty blood in ventricles during the cardiac cycle before the beginning of ventricular contraction  , as it prevents the ventricles from the pathological high atrial rhythm.
The average velocity of conduction in the AV node is 0.02-0.05 m/s

3- Bundle of Hiss : A continuous with the AV node that passes to the ventricles through the inter-ventricular septum. It is subdivided into : Right and left bundle. The left bundle is also subdivided into two branches: anterior and posterior branches .

4- Purkinje`s fibers: large fibers with velocity of conduction 1.5-4 m/s.
the high velocity of these fibers is due to the abundant gap junctions , and to their nature as very large fibers as well.
The conduction from AV node is a one-way conduction . This prevents the re-entry of cardiac impulses from the ventricles to the atria.
Lastly: The conduction through the ventricular fibers has a velocity of 0.3-0.5 m/s.

Factors , affecting conductivity ( dromotropism)  :

I. Positive dromotropic factors :

1. Sympathetic stimulation : it accelerates conduction and decrease AV delay .
2. Mild warming
3. mild hyperkalemia
4. mild ischemia
5. alkalosis

II. Negative dromotropic factors :

1. Parasympathetic stimulation
2. severe warming
3. cooling
4. Severe hyperkalemia
5. hypokalemia
6. Severe ischemia
7. acidosis
8. digitalis drugs.

Bile - produced in the liver and stored in the gallbladder, released in response to CCK . Bile salts (salts of cholic acid) act to emulsify fats, i.e. to split them so that they can mix with water and be acted on by lipase.

Pancreatic juice: Lipase - splits fats into glycerol and fatty acids. Trypsin, and chymotrypsin - protease enzymes which break polypeptides into dipeptides. Carboxypeptidase - splits dipeptide into amino acids. Bicarbonate - neutralizes acid. Amylase - splits polysaccharides into shorter chains and disaccharides.

Intestinal enzymes (brush border enzymes): Aminopeptidase and carboxypeptidase - split dipeptides into amino acids. Sucrase, lactase, maltase - break disaccharides into monosaccharides. Enterokinase - activates trypsinogen to produce trypsin. Trypsin then activates the precursors of chymotrypsin and carboxypeptidase. Other carbohydrases: dextrinase and glucoamylase. These are of minor importance.

DNA (Deoxyribonucleic acid) - controls cell function via transcription and translation (in other words, by controlling protein synthesis in a cell)

Transcription - DNA is used to produce mRNA

Translation - mRNA then moves from the nucleus into the cytoplasm & is used to produce a protein . requires mRNA, tRNA (transfer RNA), amino acids, & a ribosome

tRNA molecule

• sequence of amino acids in a protein is determined by sequence of codons (mRNA). Codons are 'read' by anticodons of tRNAs & tRNAs then 'deliver' their amino acid.
• Amino acids are linked together by peptide bonds (see diagram to the right)
• As mRNA slides through ribosome, codons are exposed in sequence & appropriate amino acids are delivered by tRNAs. The protein (or polypeptide) thus grows in length as more amino acids are delivered.
• The polypeptide chain then 'folds' in various ways to form a complex three-dimensional protein molecule that will serve either as a structural protein or an enzyme.

• Sensory:
  • Somatic (skin & muscle) Senses:
    Postcentral gyrus (parietal lobe). This area senses touch, pressure, pain, hot, cold, & muscle position. The arrangement is upside-down (head below, feet above) and is switched from left to right (sensations from the right side of the body are received on the left side of the cortex). Some areas (face, hands) have many more sensory and motor nerves than others. A drawing of the body parts represented in the postcentral gyrus, scaled to show area, is called a homunculus .
  • Vision:
    Occipital lobe, mostly medial, in calcarine sulcus. Sensations from the left visual field go to the right cortex and vice versa. Like other sensations they are upside down. The visual cortex is very complicated because the eye must take into account shape, color and intensity.
  • Taste:
    Postcentral gyrus, close to lateral sulcus. The taste area is near the area for tongue somatic senses.
  • Smell:
     The olfactory cortex is not as well known as some of the other areas. Nerves for smell go to the olfactory bulb of the frontal cortex, then to other frontal cortex centers- some nerve fibers go directly to these centers, but others come from the thalamus like most other sensory nerves
  • Hearing:
    Temporal lobe, near junction of the central and lateral sulci. Mostly within the lateral sulcus. There is the usual crossover and different tones go to different parts of the cortex. For complex patterns of sounds like speech and music other areas of the cortex become involved.
• Motor:
  • Primary Motor ( Muscle Control):
    Precentral gyrus (frontal lobe). Arranged like a piano keyboard: stimulation in this area will cause individual muscles to contract. Like the sensory cortex, the arrangement is in the form of an upside-down homunculus. The fibers are crossed- stimulation of the right cortex will cause contraction of a muscle on the left side of the body.
  • Premotor (Patterns of Muscle Contraction):
    Frontal lobe in front of precentral gyrus. This area helps set up learned patterns of muscle contraction (think of walking or running which involve many muscles contracting in just the right order).
  • Speech-Muscle Control:
    Broca's area, frontal lobe, usually in left hemisphere only. This area helps control the patterns of muscle contraction necessary for speech. Disorders in speaking are called aphasias.
• Perception:
  • Speech- Comprehension:
    Wernicke's area, posterior end of temporal lobe, usually left hemisphere only. Thinking about words also involves areas in the frontal lobe.
  • Speech- Sound/Vision Association:
    Angular gyrus, , makes connections between sounds and shapes of words

Alveolar Ventilation: is the volume of air of new air , entering the alveoli and adjacent gas exchange areas each minute . It equals to multiplying of respiratory rate by ( tidal volume - dead space).
Va = R rate X (TV- DsV)
     = 12 X ( 500-150)
     = 4200 ml of air.