Homeostasis Flashcards
All homeostatic control systems have three functional components
start at stimulus A receptor (or monitor) A coordinating centre A regulator (or effector) end with response
The homeostatic control process can be
conscious, such as when you decide to put on a jacket when you feel cold. These are behavioral responses.
unconscious, such as when you start to shiver. These are physiological responses.
Negative feedback
Negative feedback systems, (also called negative feedback loops) are mechanisms that make adjustments to bring the systems of the body back to within an acceptable range.
blood pressure
ectotherms
Most organisms cannot maintain a constant internal body temperature, regardless of their surroundings
thermostat” for thermoregulation is located in a region of the brain called the hypothalamus
when youre hot
heart rate speeds up to pump blood to skin to cool down
sweat
when youre cold
vasocontriction limits blood flow and slows heat loss
Main organs of the excretory system
kidneys
liver
large Intestine
Your excretory system has three main jobs:
to remove waste
monitor water balance
control pH
How does the excretory system help maintain homeostasis?
The excretory system helps maintain homeostasis by filtering out metabolic waste, balancing pH, and monitoring blood pressure.
The structure of the kidney
The outer layer is the cortex and encircles the kidney.
The inner layer, called the medulla, is found beneath the cortex.
A hollow chamber, known as the renal pelvis, joins the kidney with the ureter.
The functional unit of the kidney
nephrons. They are located in the cortex and extend down into the medulla. Nephrons are surrounded by a mesh of fine blood vessels, called capillaries, that allows waste to diffuse out of the blood.
Each nephron consists of five main parts:
Bowman’s capsule (containing the glomerulus) Proximal tubule Loop of Henle Distal tubule Collecting duct
DO DIAGRAM ON 5.2
blood flow in a nephron
The Bowman’s capsule, the afferent arteriole, and the efferent arteriole (branches into peritubular capillaries are located in the cortex of the kidney.
Blood enters the glomerulus and is filtered, through pressure, into Bowman’s capsule, which is located in the cortex.
The filtrate passes through the proximal tubule, which is also located in the cortex. This is where glucose and amino acids are reabsorbed to the blood.
Next, the filtrate moves down into the loop of Henle, which is located in the medulla of the kidney. Here, water is removed from the filtrate and returned to the blood.
The filtrate then moves through the distal tubule located in the cortex, where hydrogen ions and drugs that are to be excreted in the filtrate are extracted (or secreted) from the blood. Even more water is removed from the filtrate and returned to the blood.
Finally, the filtrate moves into the collecting duct, which is located in the medulla. These ducts collect filtrate (now called urine) from many nephrons and eventually merge in the renal pelvis of the kidney. The urine exits the renal pelvis via the ureter, to be stored in the bladder.
Filtration
The movement of fluids from the blood into Bowman’s capsule is called filtration. The dissolved solutes leave the afferent arteriole and enter Bowman’s capsule, which is porous.
Plasma protein, blood cells, and platelets are too large to move through the pores of the glomerulus, while smaller molecules pass through the walls and enter the nephron. It
only uses passive transport.
Step 2: Reabsorption
The transfer of essential solutes and water from the nephron back into the blood is called reabsorption. It uses active transport to move sodium (N + ) ions, glucose, and amino
acids back into the blood and it uses passive transport to move water from the nephron back into the blood.
Step 3: Secretion
The movement of materials, such as nitrogen-containing waste, excess H + ions, and
some minerals and drugs are secreted into the urine. It only uses passive transport.
The roles of the endocrine and nervous systems in water balance
Antidiuretic hormone (ADH), helps to regulate the osmotic pressure of body fluids by causing the kidneys to increase water reabsorption. ADH moves along specialized fibres from the hypothalamus to a gland called the pituitary gland, which stores and releases ADH into the blood. Changes in osmotic pressure in the blood are picked up by specialized nerve receptors in the hypothalamus called osmoreceptors.
Kidneys also play a role in maintaining normal blood pressure.
A hormone called aldosterone acts on the nephrons to increase Na+ reabsorption. Aldosterone is produced in the cortex of the adrenal glands, which lies above the kidneys.
The aldosterone travels in the blood to the kidneys, where it acts on the cells of the distal tubule and collecting duct to increase Na+ transport. When Na+ is reabsorbed, water follows, increasing the blood volume and thus increasing blood pressure.
If low pressure is detected, nearby specialized cells in the adrenal glands, release an enzyme, renin, that converts a plasma protein called angiotensinogen into angiotensin.
angiotensinogen into angiotensin.
conversion by renin
It constricts blood vessels, thus increasing blood pressure.
It stimulates the release of aldosterone from the adrenal gland.
How does ADH work to control water balance?
The release of ADH by the pituitary gland helps the kidneys to regulate the osmotic concentration of body fluids.
ADH does this by making the upper part of the distal tubule and collecting duct permeable to water.
The water leaves the upper part of the distal tubule and enters the blood, making the urine more concentrated.
blood pH is too high
The carbonate ion bonds to any excess H+ ions to form carbonic acid ( H2CO3 ) and so lowers the blood pH.
The carbonic acid breaks down into carbon dioxide and water, and the CO2 is transported to the lungs, where much of it is exhaled.
blood pH is too low
The carbonic acid breaks down into H+ ions and water, in order to raise the blood pH.
Kidney stones occur
solutes from the blood precipitate (solidify) out of the urine. These solutes can accumulate and lodge themselves in the renal pelvis or move into the narrow ureter. As the kidney stones move into the bladder, they can tear delicate tissue and cause severe pain and discomfort. They can also work their way further down the excretory passage and lodge in the urethra, causing a burning sensation, along with excruciating pain.
Diabetes insipidus
ADH-producing cells of the hypothalamus, or the nerve tracts leading from the hypothalamus to the pituitary gland, are destroyed. Without ADH to regulate water reabsorption, urine output increases considerably, so none of the remaining 15% (after the other 85% has been reabsorbed at the proximal tubule), is recovered. As much as 20 L of dilute urine may result, creating a strong thirst response, and a severe need to replace lost water.
brights disease
nephritis or the inflammation (swelling) of the nephrons.
Toxins produced by invading microbes destroy the tiny blood vessels, altering the permeability of the nephron. This means that proteins and other large molecules are able to pass into the nephron. When the nephrons are destroyed, no mechanism occurs in the nephron membrane to reabsorb protein; instead, the protein remains in the nephron and draws water from the neighbouring peritubular capillaries, which, in turn, increases the output of urine.
The endocrine system is instrumental in:
regulating mood growth and development tissue function metabolism sexual function reproductive processes
endocrine system
system of glandular tissues that produce and secrete special messenger molecules called hormones, into the blood.
hormone” means “to excite or set into motion.”
antagonistic hormones
the hormones glucagon and insulin, which are both secreted by the pancreas, have opposite effects in response to high or low blood glucose levels. Hormones that have opposite effects
High (hyperglycemia)
After a meal
Insulin is released from the beta cells in your pancreas
Cells in your muscles, liver, and other organs to become more permeable to glucose.
When the glucose is drawn out of your blood, this lowers your blood glucose level.
Once in your liver, the glucose is converted to glycogen (the storage form of glucose).
symptoms
Glucose in the urine.
Dehydration and thirst caused by glucose in the nephron, which in turn draws water out of the blood through osmosis.
Low energy levels because of a lack of insulin, the permeability of glucose into the cells does not increase, so less glucose is burned and less ATP is made.
Low (hypoglycemia)
Long period after last meal
Fasting
Not enough food ingested
Glucagon is released by the alpha cells of the islets of Langerhans.
During periods of fasting, glucagon is released and promotes the conversion of glycogen to glucose, which is released into the blood, thus raising the blood sugar level.
Type 1 (previously called juvenile onset)
Inability to produce insulin, due to an early degeneration of the beta cells in the islets of Langerhans.
Occurs in early childhood
Insulin must be taken daily in order to survive
Type 2 (Adult onset)
most common
Decrease in insulin production or ineffective use of the insulin that the body does produces\
Can be controlled with diet, exercise, and a variety of medications that are used to enhance insulin levels or reduce the level of glucose in the blood
Epinephrine Increases
Mobilizes energy release from stored carbohydrates and fats
Increases blood glucose and fatty acids
Accelerates heart rate and breathing
in short term stress also norepi is released
Glucagon Increases
Converts glycogen to glucose
in short term stress
Insulin Decreases
Decreases the breakdown of glycogen in the liver
short term stress
Long-term exposure to stress can cause health problems
Higher blood sugar-
Alters osmotic balance between blood and extracellular fluids; can lead to increased fluid uptake by the blood and increased blood pressure
Increases water loss from nephron
Increased blood pressure
Can rupture blood vessels due to higher pressure
Increases blood clotting
Increased heart rate
Can lead to higher blood pressure
Can damage heart muscle
Male hormones are called
androgens
female reproductive cycle, many follicles develop in a process called
oogenesis
