homeostasis - osmo and gas (chapter 6) Flashcards
types of body fluids
intracellular fluid (cytosol):
- fluid contained within the cells of an organism,
- 2/3 pf total body water
extracellular fluid:
- plasma (1/4 of extracellular fluid)
- intracellular (tissue/interstitual fluid) - (3/4 extracellular fluid, like lymph, cerebrospinal fluid, kidney filtrate etc.)
movement of products
water:
- moves via osmosis (passive transport - from areas of high concentration to low concentrations)
nutrients and waste:
- products if small enough and lipid soluble move via diffusion (passive)
larger/water soluble substances:
- cannot directly diffuse and may remain where they are
stages of formation of urine
filtration:
- blood enters renal capsule under high pressure
selective reabsorption:
- mainly in proximal convoluted tubule - some water and salts are reabsorbed in loop of Henle and distal convoluted tubule
tubular secretions:
- occurs in proximal and distal convoluted tubules
controlling water levels
water is continually lost from the body in sweat, urine, faeces and exhaled air - makes plasma more concentrated and hence higher osmotic pressure
water moves from interstitual fluid into the plasma via osmosis
this results in the interstitual fluid becoming more concentrated
water diffuses out of cells and the cells begin to think from dehydration
osmoreceptors in the hypothalamus detect the increase in osmotic pressure
composition of urine
the volume and composition of urine produced by kidneys depends on how much water there is in the body fluids:
- drink a large volume of water = produced a large volume of urine
- drink not enough water = produces a small volume of concentration urine
99% of water filtered through the glomerulus of the kidneys is reabsorbed:
- reabsorption occurring at the proximal convoluted tubule and loop of henle = osmosis
- reabsorption occurring at the distal convoluted tubule and collecting duct = active reabsorption = levels of active reabsorption is controlled by the hormone ADH
antidiuretic hormone
- hypothalamus stimulates posterior pituitary gland to release ADH
- after a stimulus of water concentration of blood plasma/osmotic pressure in blood increases
- osmoreceptors in hypothalamus detect decrease in water concentration/increase in osmotic pressure
- increased amount of eater is reabsorbed into blood/water concentration of blood plasma increases/osmotic pressure of blood decreases
role of aldosterone
- secreted from adrenal cortex
- acts on distal convoluted tubules and collecting ducts to increase concentration of sodium ions in blood
- decreases the concentration of potassium ions in blood, more K+ is excreted in urine
- water is also reabsorbed from the filtrate with the sodium ions, hence aldosterone causes water content and blood volume to increase
- as a result, aldosterone indirectly increases blood pressure due to the increase in blood volume
dysfunctions
dehydration:
- when 2% or more of body fluid lost, can be due to sweating, vomiting or diarrhoea (in elderly people thirst reflex isn’t as strong) can lead to severe thirst, head aches, low blood pressure and dizziness.
intoxication:
- body fluids become diluted and cells take in extra water due to osmosis, it can happen if you lose lots of water through sweating and replace with plain water. lightheadedness, vomiting and collapse
negative feedback loop (thirst reflex)
stimulus:
- water concentration of blood plasma decreases, osmotic pressure of the blood is increased; mouth becomes dry
receptors:
- osmoreceptors in the thirst centre of the hypothalamus are stimulated
modulator:
- hypothalamus is stimulated (thirst centre)
effector:
- CNS develops conscious desire for water
- skeletal muscles - voluntary control (reach for water)
response:
- person responds to the feeling of thirst by drinking
- water drunk is absorbed into the blood from the alimentary canal
negative response:
- water leaves the blood and extracellular & intercellular fluids return to their normal concentrations
negative feedback loop (thirst reflex)
stimulus:
- water concentration of blood plasma decreases, osmotic pressure of the blood is increased
receptors:
- osmoreceptors in the Hypothalamus are stimulated
modulator:
- hypothalamus stimulates the posterior lobe of the pituitary gland to release ADH
effector:
- permeability to water of the distal convoluted tubules and collecting ducts in the nephron of the kidney is increased.
response:
- increased reabsorption of water into the blood plasma from the DCT and collecting duct
negative response:
- water concentration of the blood plasma increases; osmotic pressure of the blood is decreased
gas exchange
- all cells need a constant supply of oxygen to provide energy through the process of cellular respiration
- carbon dioxide is a by-product of cellular respiration, is toxic to calls, hence must be removed from the cellular environment
- the respiratory system is responsible for taking in oxygen and excreting carbon dioxide
- changes to rate and depth of breathing allow regulation of gas levels in blood
muscles of ventilation
diaphragm:
- muscles that separate the thorax from the abdomen
- stimulated by impulses from the phrenic nerve
- phrenic nerve originate from spinal nerves - these have their origin in the spinal cord at the level of the cervical and thoracic regions
intercostal muscles:
- muscles between the ribs
- stimulated by impulses from the intercostal nerves
- intercostal nerves originate from spinal nerves - these have their origin in the spinal cord at the level of the cervical and thoracic regions
respiratory centre:
- nerve impulses that travel to the diaphragm and intercostal muscles via the phrenic nerve and intercostal nerves are controlled by the respiratory centre, located in medulla oblongata of the brain
- there are 2 regions within respiratory centre:
- 1 controls expiration
- 1 controls inspiration
chemoreceptors
when they are stimulated, they send a nerve impulse to the area of the respiratory centre that regulates breathing.
peripheral:
- groups of cells within the walls of the aorta and carotid arteries
- sensitive to the changes in the concentration of oxygen, carbon dioxide and hydrogen ions in the blood plasma
- known as aortic and carotid bodies
central:
- located in the medulla oblongata
- sensitive to changes in the concentration of carbon dioxide in blood and hydrogen ions in the cerebrospinal fluid
relationship between CO2 and H- concentrations (pH)
- both O2 and CO2 are carried in the blood, their concentrations effect breathing rate
- when CO2 dissolves into plasma it forms carbonic acid which readily breaks down into H- and bicarbonate ions
- increasing H- concentrations causes a decrease in plasma, pH = more acidic
- increasing CO2 concentrations and H- concentrations are main stimuli for increasing breathing rate and depth
oxygen levels
- concentration has to fall to very low levels to stimulate an effect
- a large decrease in oxygen concentration stimulates chemoreceptors in peripheral (sending an impulse)
- sends to diaphragm and intercostal muscles so breathing rate and depth increase
