5.1 Homeostasis
What is the function of positive feedback loops in the body?
To amplify the stimulus of certain processes that must be completed quickly to prevent excessive stress on the body like child birth
Where does most of the liver's blood supply come through?
Most of the liver's blood supply comes through the hepatic portal vein, which brings blood directly from the stomach, spleen, pancreas and small and large intestines.
Provide an example of a behavioural response that prevents body temperature from rising and from falling
From rising: turning on the fan
From falling: wearing more layers
List and describe the three types of extracellular fluid.
Intravascular fluid: includes the blood plasma within the blood vessels
Interstitial/intercellular/tissue fluid: fluid between the cells
Transcellular fluid: fluid in specific body regions, which includes the fluid in the brain and spinal cord, eyes and joints, and surrounding the heart
What do chemoreceptors do when they are stimulated in the context of breathing?
When chemoreceptors are stimulated, they send a nerve impulse to the area of the respiratory centre that regulates breathing.
Why is the internal environment of the body in a dynamic equilibrium?
It is in an equilibrium to maintain a constant environment for the body to function but it is dynamic as there are constant fluctuations of the equilibrium
Contrast glycogenesis, glycogenolysis, gluconeogenesis.
Glycogenesis:
Glycogenolysis:
Gluconeogenesis:
Compare and contrast heat stroke and heat exhaustion.
Heat stroke: high temperature and high humidity causes difficulty in heat loss causing body temperature to rise and regulatory mechanisms cease
Heat exhaustion: extreme sweating and vasodilation causes major water loss causing reduced blood pressure and decreased blood output from heart
What is ADH and where is it produced, released from and what is its effect?
ADH is produced by the hypothalamus gland and released from the posterior lobe of the pituitary gland.
It regulates bodily water levels by controlling the level of active reabsorption in the collecting duct and distal convoluted tubule in the nephrons of the kidney.
How is the circulatory system involved in regulation of gas concentrations?
The circulatory system carries oxygen from the lungs to the cells, where it is used.
It also takes away the carbon dioxide produced and delivers it to the lungs for excretion from the body.
How does the set point and tolerance limits during a fever affect thermoregulation?
Set point - point where conditions fluctuate around
Tolerance limits - upper and lower limits of the fluctuation where the body still functions normally
Affect on thermoregulation - the set point of the body is reset to a higher level during a fever which then brings up the tolerance limits so thermoregulation brings up body temperature to be within tolerance limits
How does the level of blood glucose regulate secretion of insulin via negative feedback system?
Beta cells in the Islets of Langerhans secrete insulin.
Insulin from the beta cells causes a decrease in blood glucose levels by:
These activities decrease blood glucose levels
The level of blood glucose regulates the secretion of insulin via a negative feedback system
When blood glucose levels rise above normal chemoreceptors in the beta cells of the islets of Langerhans stimulate those cells to secrete insulin.
As the level of blood glucose decreases, the cells are no longer stimulated and production is reduced.
How does metabolism affect body temperature? What impact would hypo/hyper-thyroidism have on body temperature?
Metabolism affects the rate of reactions in the cells of the body so it is directly related to the amount of heat energy produced which is used to regulate internal body temperature.
Hypothyroidism - a condition that results in insufficient production of thyroid hormone for normal body function. This causes a decrease in metabolism which causes a decrease in body temperature
Hyperthyroidism - a condition that results in excessive production of thyroid hormone for normal body function. This causes an increase in metabolism which causes an increase in body temperature
Contrast dehydration and water intoxication (description, cause, symptoms) and their respective effects
Dehydration is when water loss exceeds water intake, and there's not enough water in the body to carry out normal functioning. Symptoms become obvious when more than 2% of normal body water has been lost.
Dehydration symptoms include severe thirst, low blood pressure, dizziness and headache.
Dehydration can be caused by sweating, vomiting and diarrhoea.
Water intoxication or water poisoning is when there's too much water in the body. It occurs when body fluids become diluted and cells take in extra water by osmosis.
Water intoxication symptoms include light-headedness, followed by headache, vomiting and collapse.
Water intoxication can be caused by losing lots of water and salt through sweating, and the loss is replaced with plain water.
Why is the concentration of carbon dioxide a major factor in the regulation of breathing rate and how do they affect breathing rate?
The concentration of carbon dioxide is associated with the concentration of hydrogen ions.
The increase in concentration of both of these chemicals in the blood stimulates the central and peripheral chemoreceptors
These in turn transmit nerve impulses to the respiratory centre, resulting in an increase in breathing rate and depth
Chemoreceptors in the medulla oblongata are responsible for 70-80% of the increase in breathing rate that results from an increase in carbon dioxide concentration of blood
This response takes several minutes
The immediate increase in breathing rate that occurs following an increase in the carbon dioxide concentration of the plasma is produced by the stimulation of the aortic and carotid bodies.
These bodies are stimulated by the associated increase in hydrogen ion concentration.