Chapter 6 - Homeostasis fluid and gas Flashcards
name 3 important roles of fluid in the body
- Transporting substances from one area of the body to another
- Facilitating movement across membranes
- Being the site of chemical reactions
which organs have the highest water content
Brain, kidneys and lungs
Intracellular fluid
Fluid inside the cells (cytosol)
Extracellular fluid
Fluid outside the cells. includes:
- Blood plasma and blood vessels (intravascular fluid)
- Fluid between cells (intercellular/interstitial)
- Fluid and specific body regions (Transcellular fluid)
There is a continuous exchange of materials between different body fluids
Osmotic pressure
The tendency of a solution to take in water. The greater the difference in osmotic concentration between two solutions, the greater the osmotic pressure
Osmotic concentration
Concentration of solutes. If an imbalance in osmotic concentration does occur in any tissue, osmosis restores balance
How is body fluid obtained
- Food
- Metabolic water (Water formed as by product of cellular respiration)
- Drinking
How is body fluid lost
- Lungs
- Skin
- Kidneys
- Faeces
Organs take part in excretion
Lungs, sweat glands, elementary canal, kidneys
role of lungs in excretion
Excretion of carbon dioxide. body cannot use CO2, is carried in blood to lungs for excretion. Water also lost as water vapour
role of sweat glands in excretion
In skin, secrete water containing byproducts of metabolism (salts, urea, lactic acid)
role of alimentary canal in excretion
Passes out bile pigments that entered small intestine with the bile. These pigments are breakdown products of haemoglobin
role of kidneys in excretion
Main excretory organ, responsible for maintaining a constant concentration of materials in body fluids. Removes urea which is produced by the liver during protein breakdown
explain the function of the nephron
- Blood enters glomerulus under high-pressure
- Filtration. The high blood pressure forces water and small dissolved molecules out of the blood and into the glomerular capsule
- The filtrate is collected by the glomerular capsule
- Reabsorption. The filtrate passes through the proximal convoluted tubules, the loop of Henle, the distal convoluted tubules and 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 kidney tubules from capillaries
- Urine. The water and dissolved substances that remain make up the urine
Negative feedback loop of the kidneys and ADH
- Stimulus: Osmotic pressure of the blood is raised due to the decrease in water in the blood
- Receptor: Osmoreceptors in the hypothalamus detect the increased osmotic pressure
- Modulator: Hypothalamus stimulates the posterior lobe of the pituitary gland to release ADH into the bloodstream
- Effector: ADH effects target organs (nephron tubules in kidney). The permeability to water of the distal convoluted tubules and collecting ducts are increased
- Response: More water is reabsorbed into the blood plasma from the distal convoluting tubule and collecting duct
- Feedback: Osmotic pressure of blood decreased. Negative feedback has occurred
Cellular respiration equation
Oxygen + Glucose → Carbon dioxide + water + energy
How is the circulatory system involved in the regulation of gas concentrations
Carries oxygen from the lungs to the cells where it is used. Also takes away the carbon dioxide produced and delivers it to the lungs for excretion from the body
what muscles cause air to move in and out of the lungs
- The diaphragm, stimulated by impulses from the phrenic nerve
- The intercostal muscles, stimulated by impulses from the intercostal nerves
respiratory centre
Located in the medulla oblongata, regulates breathing rate. Two regions, one controls expiration and the other controls inspiration
carbonic acid and bicarbonate ions equation
CO2 + H20 ⇌ H2CO3 ⇌ H (positive) + HCO3 (negative)
two types of chemoreceptors
- Peripheral: groups of cells within walls of aorta and carotid arteries. Sensitive to changes of concentration of oxygen, carbon dioxide and hydrogen ions in the blood. Called aortic and carotid bodies
- Central: Located in medulla oblongata. Sensitive to changes in concentration of carbon dioxide in blood and hydrogen ions in the cerebrospinal fluid. When stimulated send nerve impulse to respiratory centre
explain how oxygen and carbon dioxide levels are regulated
Chemoreceptors recognise changes in the concentration of oxygen, carbon dioxide and hydrogen ions in the blood. They send impulses to the respiratory centre in the Medulla oblongata, which controls rate and depth of breathing. Messages are sent from the respiratory centre, along the descending tract of the spinal-cord and then to the phrenic and intercostal nerves to cause contraction and relaxation of the diaphragm and intercostal muscles. Increasing the rate of the cycle of contraction and relaxation will increase the rate and depth of breathing and therefore The inhalation of oxygen and exhalation carbon dioxide
how can we voluntarily breath
Voluntary control comes via connections from the cerebral cortex to the descending tracts in the spinal cord, bypassing the respiratory centre
hyperventilation
rapid, deep breathing providing more oxygen than required and removing more carbon dioxide than necessary
why is it bad for swimmers to hyperventilate
Allows a person stay in the water for longer due to loss of carbon dioxide. The breath holding ability can be increased to such an extent that the individual loses consciousness from lack of oxygen before feeling the urge to breathe
what happens as a result of an increase of hydrogen ion concentration in the blood
pH decreases. Directly stimulating chemoreceptors in the aortic and carotid bodies, which then transmit impulses to respiratory Centre, resulting in an increase in breathing rate and depth. Also stimulated by an increase in concentration of CO2 which is detected by chemo receptors in the medulla oblongata
What type of reabsorption occurs at the proximal convoluted tubule and the loop of Henle
osmosis
What type of reabsorption occurs at the distal convoluted tubule and collecting tubule
Active reabsorption, Controlled by ADH
What happens when the concentration of ADH in the blood plasma is high
The tubules are very permeable to water and thus water is able to leave the tubule and into the surrounding capillary network
What happens when the concentration of ADH in the plasma is a low
The tubules are not very permeable to water and little water is reabsorbed into the plasma of the blood
What four things is aldosterone secreted in response to
- Decrease in concentration of sodium ions in blood
- Decrease in blood volume
- Decrease in blood pressure
- Increase in concentration of potassium ions in blood
