Monday, May 27, 2013

Endocrine System #3: Thyroid Gland

Located at the base of the neck, the thyroid gland is one of the biggest endocrine glands in the body.

It's main function is to produce thyroid hormones, which are used for regulating the body's metabolism.

Endocrine System #2: Stress Regulation

The adrenal gland handles stress through secreting various hormones. The adrenal cortex is responsible for dealing with long-term stress, whereas the adrenal medulla is responsible for dealing with short term stress.

Dealing with Short-Term Stress
  1. Stress causes the release of the acetylcholine, a neurotransmitter
  2. This signals the adrenal cortex to release catecholamines: epinephrine and nor-epinephrine
  3. Effects: 1) increased breakdown of glucagon into glucose;  2) increased blood pressure and bloodflow; 3) increased metabolism; 4) decrease in bloodflow to kidneys and intestines, and more blood flows to the brain, muscles and muscles, and 5) increased breathing rate.

Endocrine System #1: Glucose Regulation

In the pancreas, the islets of Langerhans contain cells that secrete hormones that regulate blood glucose levels and glucose metabolism.

The alpha cells secrete glucagon when blood sugar levels are low. Glucagon triggers the liver to break down more glycogen into glucose, and to convert more amino acids and glycerol to glucose.

The beta cells secrete insulin when blood sugar levels are high. Insulin increases cells' glucose uptake by activating their glucose transporters. It also suppresses the liver's ability to convert glycogen to glucose.

Tuesday, May 21, 2013

Kidney #2— Functions and Mechanisms

  1. Blood enters a ball of capillaries called glomerulus
  2. Due to high blood pressure (65 mm Hg as opposed to 25 mm Hg), blood is filtered into the lumen of Bowman's capsule. Water and small dissolved molecules (salts, sugar, amino acid, nitrogenous waste, etc.) enter the glomerulus and become the filtrate. Blood cells, plasma proteins, and platelets are filtered out.
    •  Bowman's capsule is the blind end of the nephron's tubule, and it surrounds the glomerulus
  3. In the proximal tubule, hydrogen ions are secreted, and bicarbonate ions—which are important buffers— are reabsorbed. The epithelial cells also secrete ammonia to maintain a constant pH within the filtrate. In addition, drugs and other toxins are released from the peritubular capillaries, and they travel through the interstitial fluid and are secreted into the filtrate. Furthermore, important nutrients, such as glucose, amino acids, potassium ions, are actively or passively transported back to the blood. Sodium ions are pumped into the interstitial fluid, which allows water to follow by osmosis.
  4. The filtrate now travels into the descending limb of the loop of Henle, from the cortex to the inner medulla. In this section, the transport epithelium is permeable to water but not salt and other solutes, so water diffuses out of the tubule.
  5. The filtrate now travels up the ascending limb of the loop of Henle, from the inner medulla back to the cortex. In the thin segment that is close to the turn, NaCl is passively diffused out of the tubules, which contributes to the high osmolarity of the inner medulla. In the thick segment in the cortex, NaCl is pumped out of the tubule.
    The reason why an osmotic gradient exists within the entire loop of Henle is that the blood flows in the opposite direction as the filtrate.
  6. Next, the filtrate enter the distal tubule. Potassium and hydrogen ions are secreted, and  NaCl and bicarbonate ions are reabsorbed.
  7. The filtrate then enters the collecting duct, which carries the filtrate into the renal pelvis (note that the collecting duct collects from several nephrons). Here, sodium chloride is actively transported out of the duct. Also, in the inner medulla, urea diffuses into interstitial fluid. This increases the osmolarity of the interstitial fluid and enables water to be reabsorbed.

Kidney #1

The kidney is an essential organ in the excretory system. It performs the following tasks:
  • maintaining blood pressure
  • blood filtration
  • hormone secretion
  • waste excretion
  • pH maintenance


Osmoregulation is the regulation of body's water content and solute concentration.


Physical Adaptations
  • Fur, hair, etc to insulate heat

Circulatory Adaption
  • Countercurrent flow

Behavioural Adaption
  • Gross muscle movements
  • huddling
  • relocation
  • torpor

Physiological Changes
  • Regulating rate of heat exchange through vasoconstriction and vasodilation
  • Regulating rate of heat production through muscle contractions and shivering
  • Regulating rate of metabolic heat production 

Tuesday, May 14, 2013

Foreign Exchange Market

 photo foreign_exchange_market.png

For simplicity, I will explain everything using the graph above.

In this case, The demand function is determined by the Japanese, who wants Canadian dollars in order to purchase Canadian goods, services, or assets.

The supply function is determined by Canadians, who want to exchange their currency for yen in order to purchase Japanese goods, services, or assets.

Things that increase the demand (the opposite decreases the demand) :
  • If Japanese people become richer, they will buy more imported goods, thus increasing demand for CAD.
  • If the interested rate of CAD rises, Japanese people will want to hold CAD as a financial asset
  • If inflation is higher in Japan than in Canada, Japanese people will want more imported goods because they become relatively cheaper
  • Speculation of a rise in CAD exchange rate.

Things that increase the supply (the opposite decreases the supply) :
  • Canadian investments in Japan
  • If Canadians become richer, they will buy more imported goods
  • Inflation in Canada

Sunday, May 12, 2013

Money Market

The horizontal axis should be labeled: quantity of money
The vertical axis should be labeled: nominal interest rate

The money supply is a vertical line.

Loanable Funds Market

The lonanable funds market is our banks. The supply of loanable funds represents how much people are willing to deposit into their banks, and the demand represents how much people are willing to borrow.

The horizontal axis should be labeled: quanitity of loanable funds.
The vertical axis should be labeld: real interest rate (%).

Phillips Curve

The phillips curve is a curve showing the inverse relationship between unemployment rate and inflation rate. It represents the tradeoff between inflation and unemployment in the short run.

A rightward movement along the phillips curve represents a leftward movement of the AD curve, and vice versa.

An outward shift of the phillips curve represents a supply shock or an increase in inflationary expectation.