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

Respiration involves several components:

Ventilation - the exchange of respiratory gases (O₂ and CO₂) between the atmosphere and the lungs. This involves gas pressures and muscle contractions.

External respiration - the exchange of gases between the lungs and the blood. This involves partial pressures of gases, diffusion, and the chemical reactions involved in transport of O₂and CO₂.

Internal respiration - the exchange of gases between the blood and the systemic tissues. This involves the same processes as external respiration.

Cellular respiration - the includes the metabolic pathways which utilize oxygen and produce carbon dioxide, which will not be included in this unit.

Ventilation is composed of two parts: inspiration and expiration. Each of these can be described as being either quiet, the process at rest, or forced, the process when active such as when exercising.

Quiet inspiration:

The diaphragm contracts, this causes an increase in volume of the thorax and the lungs, which causes a decrease in pressure of the thorax and lungs, which causes air to enter the lungs, moving down its pressure gradient. Air moves into the lungs to fill the partial vacuum created by the increase in volume.

Forced inspiration:

Other muscles aid in the increase in thoracic and lung volumes.

The scalenes - pull up on the first and second ribs.

The sternocleidomastoid muscles pull up on the clavicle and sternum.

The pectoralis minor pulls forward on the ribs.

The external intercostals are especially important because they spread the ribs apart, thus increasing thoracic volume. It's these muscles whose contraction produces the "costal breathing" during rapid respirations.

Quiet expiration:

The diaphragm relaxes. The elasticity of the muscle tissue and of the lung stroma causes recoil which returns the lungs to their volume before inspiration. The reduced volume causes the pressure in the lungs to increase thus causing air to leave the lungs due to the pressure gradient.

Forced Expiration:

The following muscles aid in reducing the volume of the thorax and lungs:

The internal intercostals - these compress the ribs together

The abdominus rectus and abdominal obliques: internal obliques, external obliques- these muscles push the diaphragm up by compressing the abdomen.

Respiratory output is determined by the minute volume, calculated by multiplying the respiratory rate time the tidal volume.

Minute Volume = Rate (breaths per minute) X Tidal Volume (ml/breath)

Rate of respiration at rest varies from about 12 to 15 . Tidal volume averages 500 ml Assuming a rate of 12 breaths per minute and a tidal volume of 500, the restful minute volume is 6000 ml. Rates can, with strenuous exercise, increase to 30 to 40 and volumes can increase to around half the vital capacity.

Not all of this air ventilates the alveoli, even under maximal conditions. The conducting zone volume is about 150 ml and of each breath this amount does not extend into the respiratory zone. The Alveolar Ventilation Rate, AVR, is the volume per minute ventilating the alveoli and is calculated by multiplying the rate times the (tidal volume-less the conducting zone volume).

AVR = Rate X (Tidal Volume - 150 ml)

For a calculation using the same restful rate and volume as above this yields 4200 ml.

Since each breath sacrifices 150 ml to the conducting zone, more alveolar ventilation occurs when the volume is increased rather than the rate.

During inspiration the pressure inside the lungs (the intrapulmonary pressure) decreases to -1 to -3 mmHg compared to the atmosphere. The variation is related to the forcefulness and depth of inspiration. During expiration the intrapulmonary pressure increases to +1 to +3 mmHg compared to the atmosphere. The pressure oscillates around zero or atmospheric pressure.

The intrapleural pressure is always negative compared to the atmosphere. This is necessary in order to exert a pulling action on the lungs. The pressure varies from about -4 mmHg at the end of expiration, to -8 mmHg and the end of inspiration.

The tendency of the lungs to expand, called compliance or distensibility, is due to the pulling action exerted by the pleural membranes. Expansion is also facilitated by the action of surfactant in preventing the collapse of the alveoli.

The opposite tendency is called elasticity or recoil, and is the process by which the lungs return to their original or resting volume. Recoil is due to the elastic stroma of the lungs and the series elastic elements of the respiratory muscles, particularly the diaphragm.

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.

Hypoxia

• Hypoxia is tissue oxygen deficiency
• Brain is the most sensitive tissue to hypoxia: complete lack of oxygen can cause unconsciousness in 15 sec and irreversible damage within 2 min.
• Oxygen delivery and use can be interrupted at several sites

• Causes:
  • Hypoxic: high altitude, pulmonary edema, hypoventilation, emphysema, collapsed lung
  • Anemic: iron deficiency, hemoglobin mutations, carbon monoxide poisoning
  • Ischemic: shock, heart failure, embolism
  • Histotoxic: cyanide poisoning (inhibits mitochondria)

• Carbon monoxide (CO) poisoning:
  • CO binds to the same heme Fe atoms that O₂ binds to
  • CO displaces oxygen from hemoglobin because it has a 200X greater affinity for hemoglobin.
  • Treatment for CO poisoning: move victim to fresh air. Breathing pure O₂ can give faster removal of CO

• Cyanide poisoning:
  • Cyanide inhibits the cytochrome oxidase enzyme of mitochondria
  • Two step treatment for cyanide poisoning:
    • 1) Give nitrites
      • Nitrites convert some hemoglobin to methemoglobin. Methemoglobin pulls cyanide away from mitochondria.
    • 2) Give thiosulfate.
      • Thiosulfate converts the cyanide to less poisonous thiocyanate.

Lipids:

• about 40% of the dry mass of a typical cell
• composed largely of carbon & hydrogen
• generally insoluble in water
• involved mainly with long-term energy storage; other functions are as structural components (as in the case of phospholipids that are the major building block in cell membranes) and as "messengers" (hormones) that play roles in communications within and between cells
• Subclasses include:
  • Triglycerides - consist of one glycerol molecule + 3 fatty acids (e.g., stearic acid in the diagram below). Fatty acids typically consist of chains of 16 or 18 carbons (plus lots of hydrogens).
  • phospholipids - Composed of 2 fatty acids, glycerol, phosphate and polar groups , phosphate group (-PO⁴) substitutes for one fatty acid & these lipids are an important component of cell membranes

steroids - have 4 rings- cholesterol, some hormones, found in membranes include testosterone, estrogen, & cholesterol

Levels of Organization:

CHEMICAL LEVEL - includes all chemical substances necessary for life (see, for example, a small portion - a heme group - of a hemoglobin molecule); together form the next higher level

CELLULAR LEVEL - cells are the basic structural and functional units of the human body & there are many different types of cells (e.g., muscle, nerve, blood)

TISSUE LEVEL - a tissue is a group of cells that perform a specific function and the basic types of tissues in the human body include epithelial, muscle, nervous, and connective tissues

ORGAN LEVEL - an organ consists of 2 or more tissues that perform a particular function (e.g., heart, liver, stomach)

SYSTEM LEVEL - an association of organs that have a common function; the major systems in the human body include digestive, nervous, endocrine, circulatory, respiratory, urinary, and reproductive.

There are two types of cells that make up all living things on earth: prokaryotic and eukaryotic. Prokaryotic cells, like bacteria, have no 'nucleus', while eukaryotic cells, like those of the human body, do.