Hyperventilation

1. Treatments :Rebreath air, hold breath (Increase CO₂)
   Give oxygen for Hypoxemia

The Stomach :

The wall of the stomach is lined with millions of gastric glands, which together secrete 400–800 ml of gastric juice at each meal. Three kinds of cells are found in the gastric glands

• parietal cells
• chief cells
• mucus-secreting cells

Parietal cells : secrete

Hydrochloric acid : Parietal cells contain a H⁺ ATPase. This transmembrane protein secretes H⁺ ions (protons) by active transport, using the energy of ATP.

Intrinsic factor: Intrinsic factor is a protein that binds ingested vitamin B₁₂ and enables it to be absorbed by the intestine. A deficiency of intrinsic factor  as a result of an autoimmune attack against parietal cells  causes pernicious anemia.

Chief Cells : The chief cells synthesize and secrete pepsinogen, the precursor to the proteolytic enzyme pepsin.

Secretion by the gastric glands is stimulated by the hormone gastrin. Gastrin is released by endocrine cells in the stomach in response to the arrival of food.

Typical Concentration Gradients and Membrane Potentials in Excitable Cells

The Na Pump is Particularly Important in the Kidney and Brain

• All cells have Na pumps in their membranes, but some cells have more than others
• Over-all Na pump activity may account for a third of your resting energy expenditure!
• In the kidney the Na pump activity is very high because it is used to regulate body salt and water concentrations
  • Kidneys use enormous amounts of energy: 0.5% of body weight, but use 7% of the oxygen supply
• Pump activity is also high in the brain because Na and K gradients are essential for nerves
  • The brain is another high energy organ; it is 2% of body weight, but uses 18% of the oxygen supply

In the Resting State Potassium Controls the Membrane Potential of Most Cells

• Resting cells have more open K channels than other types
• More K+ passes through membrane than other ions- therefore K+ controls the potential
• Blood K+ must be closely controlled because small changes will produce large changes in the membrane potentials of cells
  • Raising K will make the membrane potential less negative (depolarization)
• High blood K+ can cause the heart to stop beating (it goes into permanent contraction)

During an Action Potential Na Channels Open, and Na Controls the Membrane Potential

• Whichever ion has the most open channels controls the membrane potential
• Excitable cells have Na channels that open when stimulated
• When large numbers of these channels open Na controls the membrane potential

Regulation of Blood Pressure by Hormones

The Kidney

One of the functions of the kidney is to monitor blood pressure and take corrective action if it should drop. The kidney does this by secreting the proteolytic enzyme renin.

• Renin acts on angiotensinogen, a plasma peptide, splitting off a fragment containing 10 amino acids called angiotensin I.
• angiotensin I is cleaved by a peptidase secreted by blood vessels called angiotensin converting enzyme (ACE) — producing  angiotensin II, which contains 8 amino acids.
• angiotensin II
  • constricts the walls of arterioles closing down capillary beds;
  • stimulates the proximal tubules in the kidney to reabsorb sodium ions;
  • stimulates the adrenal cortex to release aldosterone. Aldosterone causes the kidneys to reclaim still more sodium and thus water.
  • increases the strength of the heartbeat;
  • stimulates the pituitary to release the antidiuretic hormone (ADH, also known as arginine vasopressin).

All of these actions, which are mediated by its binding to G-protein-coupled receptors on the target cells, lead to an increase in blood pressure.

Normal Chemical Composition of Urine

Urine is an aqueous solution of greater than 95% water, with a minimum of these remaining constituents, in order of decreasing concentration:

Urea 9.3 g/L.

Chloride 1.87 g/L.

Sodium 1.17 g/L.

Potassium 0.750 g/L.

Creatinine 0.670 g/L .

Other dissolved ions, inorganic and organic compounds (proteins, hormones, metabolites).

Urine is sterile until it reaches the urethra, where epithelial cells lining the urethra are colonized by facultatively anaerobic gram-negative rods and cocci. Urea is essentially a processed form of ammonia that is non-toxic to mammals, unlike ammonia, which can be highly toxic. It is processed from ammonia and carbon dioxide in the liver.

Urine is a waste byproduct formed from excess water and metabolic waste molecules during the process of renal system filtration. The primary function of the renal system is to regulate blood volume and plasma osmolarity, and waste removal via urine is essentially a convenient way that the body performs many functions using one process. Urine formation occurs during three processes:

Filtration

Reabsorption

Secretion

Filtration

During filtration, blood enters the afferent arteriole and flows into the glomerulus where filterable blood components, such as water and nitrogenous waste, will move towards the inside of the glomerulus, and nonfilterable components, such as cells and serum albumins, will exit via the efferent arteriole. These filterable components accumulate in the glomerulus to form the glomerular filtrate.

Normally, about 20% of the total blood pumped by the heart each minute will enter the kidneys to undergo filtration; this is called the filtration fraction. The remaining 80% of the blood flows through the rest of the body to facilitate tissue perfusion and gas exchange.

Reabsorption

The next step is reabsorption, during which molecules and ions will be reabsorbed into the circulatory system. The fluid passes through the components of the nephron (the proximal/distal convoluted tubules, loop of Henle, the collecting duct) as water and ions are removed as the fluid osmolarity (ion concentration) changes. In the collecting duct, secretion will occur before the fluid leaves the ureter in the form of urine.

Secretion

During secretion some substances±such as hydrogen ions, creatinine, and drugs—will be removed from the blood through the peritubular capillary network into the collecting duct. The end product of all these processes is urine, which is essentially a collection of substances that has not been reabsorbed during glomerular filtration or tubular reabsorbtion.