Huan Bio Ch 6 Flashcards
What is excretion?
The removal of the waste products of metabolism from the body
What are the 4 main ways of excretion in the body?
- Lungs - involved in the excretion of carbon dioxide, CO2 and water are produced by all cell of the bodies during cellular respiration. The body excretes CO2 through the lungs and some water vapour when we breathe out.
- Sweat glands - in the skin secrete by products of metabolism such as salts, urea and lactic acid.
- Alimentary canal - passes out bile pigments that entered the small intestine. These pigments are breakdown products from haemoglobin from red blood cells. They leave the body with the faeces.
- Kidneys - are the principal excretory organ. They are responsible for maintaining a constant concentration of materials in the body fluids. Most important waste product is urea, which is produced in the liver. They also play a major role in regulating the composition of body fluids.
What are the main components of the kidney?
- Ureter - the tube that leaves each kidney and drains into the urinary bladder
- Urinary bladder - a hollow muscular organ near the base of the abdominal cavity, and collects urine from the two ureters.
- Urethra - the tube that empties the bladder to the outside, in males it also carried sperm.
- Bladder - a muscular bag that holds the urine until it is passed out of the body
- Renal vein - takes blood away from the kidney
- Renal artery - takes blood to the kidney
What is a nephron?
A nephron is the functional unit of the kidneys. There are 1.2 million nephrons in each kidney. They carry out the kidneys role in excretion and water regulation.
What is the process of a nephron?
- Blood enters the glomerulus under high pressure
- Filtration - the high blood pressure forces water and small dissolved molecules out of the blood and into the capsule. Large molecules and blood cells are retained in the blood.
- The filtrate is collected by the glomerular capsule
- Reabsorption - the filtrate passes through the proximal convoluted tubule of the loop of Henle, the distal convoluted tubule and the collecting duct. Water and other useful substances are reabsorbed into the peritubular capillaries.
- Secretion - some materials that need to be removed from the body are secreted into the kidney tubule from the peritubular capillaries.
- Urine - the water and dissolved substances that remain make up the urine. Urine is carried by collecting ducts to the ureter and then the bladder.
What are the main components of a nephron?
- Glomerulus
- Glomerular capsule
- Proximal convoluted tubule (does reabsorption through osmosis)
- Distal convoluted tubule (active reabsorption/ADH affects permeability of the walls/Aldosterone)
- Collecting duct (ADH affects permeability of walls/Aldosterone)
- Peritubular capillaries
How does Antidiuretic hormone (ADH) affect the kidneys?
ADH controls the level of active reabsorption in the distal convoluted tubule. ADH also control the permeability of the walls of the distal convoluted tubule and the collecting duct. When the concentration of ADH in the blood is high, the tubules are very permeable to water therefore water is able to leave the tubules and enter surrounding capillary network. When the ADH levels are low, the tubules are not very permeable to water, and little water is reabsorbed into the plasma of the blood.
ADH is another example of a feedback process in the controlling the water balance in the body.
What are osmoreceptors and what do they do?
Receptors sensitive the the osmotic pressure of body fluids. They detect a change in the level of concentration in the body and produce multiple responses to alter the stimulus.
How does Aldosterone affect the kidneys?
Sometimes called salt-retaining hormone, regulates water content of the body. Responds to a:
1. Decrease in the concentration of sodium ions
2. Decrease in blood volume
3. Decrease in blood pressure
4. Increase of potassium ions in the blood
It acts on the distal convoluted tubule and collecting ducts to increase the amount of sodium ions reabsorbed into the bloodstream and the amount of potassium secreted in the urine. It achieves this through active transport using a sodium-potassium pump. This causes a net movement of ions into the blood and the subsequent transport of water via osmosis.
What is the thirst response?
There are osmoreceptors in the body that are able to trigger the thirst centre in the hypothalamus, prompting the person to drink water, this is also known as the thirst reflex. This water is then absorbed across the wall of the alimentary into the blood, decreasing the osmotic pressure.
What is the steps in the feedback loop of the thirst response?
S - as water is lost from various body fluids, there is a reduction in plasma volume, and an increase in osmotic pressure.
R - osmoreceptors in the thirst centre in the hypothalamus
M - stimulation of the thirst centre in the hypothalamus makes the person thirsty
E - the conscious feeling of being thirsty makes the person drink water
R - fluid consumed is absorbed by the alimentary canal into the blood plasma
F - as the blood circulates the body it allows the intracellular fluid to return to normal osmotic pressure.
What is dehydration?
Excessive loss of water and accompanying salts from the body, results when the body loses more fluid than it is taking in.
What is water intoxication?
A potentially life-threatening condition caused by drinking too much water when the amount of salt and electrolytes in the body is too low. Commonly caused by long bouts of intense exercise during which electrolytes are not replenished and large amount of water are consumed.
What are the muscles that control breathing?
- The diaphragm is a muscle that separates the thorax from the abdomen (phrenic nerve impulses)
- The intercostal muscles are muscles between the ribs (intercostal nerve impulses)
These are skeletal muscles that require nerve impulses to initiate contraction.
What is the respiratory centre?
The nerve impulses that travel to the diaphragm and intercostal muscles are controlled by the respiratory centre that is located in the medulla oblongata. The respiratory centre is a part of the brain that regulates breathing rate.
It has 2 regions:
1. expiration
2. inspiration
