B3.3 Maintaining internal environments Flashcards
Homeostasis definition
- means keeping a ‘steady state’
- In the body, temp, pH, water and glucose must all stay as constant as possible
- important so reactions can happen at appropriate rate
Core body temp
- keeping a core body temp of 37°C ensures enzymes can work efficiently
How is body temp controlled?
- the thermoregulatory centre is found in the brain (hypothalamus)
- it contains receptors which monitor the temp of the blood flowing through it
- It also receives information from the temp receptors in the skin
- if a change in temp is detected, impulses are sent to effectors
- These effectors respond and return body temp to normal
What happens to skin when you are hot?
- Arterioles (small blood vessels) widen, which increases the blood flow close to the skin surface. TMT more heat is lost to surroundings by radiation this is called vasodilation
- sweat glands in skin produce more sweat - when this evapourates from the skin’s surface it cools the body
- Hair erector muscles relax, allowing hair to lie flat, less air is trapped so less insulation
What happens to skin when you are cold?
Arterioles become narrower and decrease blood flow near skin surface vasoconstriction and reduces amount of heat lost by radiation
- Sweat glands stop producing sweat - less heat is lost through evap of sweat
- Hair erector muscles contract, raising hair & trapping a layer of insulating air next to the body - works better on animals
- Muscles contract spontaneously (shivering) which releases heat from respiration which helps raise blood temp
Insulin definition
Hormone made by pancreas. regulates amount of glucose in blood
tells your body to turn glucose into glycogen
Glucose definition
Sugar in respiration to transfer energy
Glycogen definition
Storage substance made of glucose - stored in the liver
Glucagon definition
Hormone that changes glycogen in the liver back into glucose - made by the pancreas
Diabetes definition
Condition where blood glucose is unable to be controlled
High blood glucose
- Pancreas detects increase in blood glucose levels & secretes insulin
Insulin causes cells (particularly muscle cells) to absorb more glucose from the blood - resulting in increased respiration and release of energy - Liver cells also take up more glucose, converting excess glucose to glycogen (storage carbs made of a long chain of glucose molecules)
- blood glucose is lowered
Low blood glucose
- Pancreas detects decrease in blood glucose levels & secretes glucagon
- Glucagon cause glycogen stores in the liver to be converted back into glucose
- this increase blood glucose levels back to normal
Controlling blood glucose levels
- Glucose rises (eat food) –> insulin produced by the pancreas causes glucose to change to glycogen in the liver –> glucose falls –> normal blood glucose level
- Glucose falls (Exercise) –> Glucagon released and glycogen converted back to glucose –> glucose rises –> normal blood glucose levels
Urine samples
- Blood in urine may be a sign of different diseases in the kidneys, the urinary system or the bladder
- Sugar in urine may be a sign of diabetes
- Protein in urine maybe be a sign of a kidney disease & can be used to detect the early signs of kidney damage from long-standing diabetes
Type 1 diabetes
- Genetic - born with it
- Cannot produce insulin
- Usually begins in childhood
- Usually controlled by insulin injections
- Can be controlled by regulating diet - more so in type 2 diabetes
Type 2 diabetes
- Cannot respond to insulin
- Usually occurs later in life
- Usually controlled by regulating diet
- linked to obesity
What is lysis?
- cells swell & burst
- the disintegration of a cell by the rupture of its cell wall or membrane
What are your kidneys?
- a pair of reddish-brown organs - important in maintaining homeostasis
- They filter your blood and produce urine
What is urine?
a mixture of toxic urea, excess salts and excess water
What is the ‘journey’ of urine?
- Urine passes from the kidneys along the ureter to the bladder
- It is stored in the bladder before being released through the urethra
What produces urea?
the liver
What is the ureter?
the tube through which urine passes from the kidney to the bladder
What is the ring of muscle by the bladder?
it controls the opening and closing of the bladder
What is the renal artery?
brings blood containing urea and other substances in solution to the kidney
What is the renal vein?
carries blood away from the kidney, after urea and other substances have been removed from the blood by the kidney
What does the bladder store?
Urine
What is the urethra?
Tube through which passes to the outside of your body
Water Balance
- The kidneys balance your water levels by altering the volume of urine produced
- when you are low on water - a small volume of concentrated urine is produced
- when you have drunk lots of water - a large volume of dilute urine is produced
How is the volume of urine controlled?
- through negative feedback
- involves hypothalamus and ADH
- ADH is released from the pituitary gland and makes the kidney tubules more permeable to water
- TMT more water is reabsorbed into the blood & a smaller volume of urine is produced
Structure of Kidney - Pelvis
The central chamber where the urine arrives from the collecting ducts
Structure of Kidney - Renal artery
brings blood to the kidney
Structure of Kidney - Renal vein
carries filtered blood away from the kidney
Structure of Kidney - Ureter
carries urine down to the bladder
Structure of Kidney - cortex
v dark red as there are many capillaries
Structure of Kidney - capsule
composed of tough fibers to protect vital tissue from injury and support the kidney mass
Structure of Kidney - medulla
contains the loop of Henle from the nephrons and regulates urine concentration
Structure of Kidney - pyramid
collection of tubules, collecting ducts and blood vessels
How is urine produced - FRU
F - Filtration small molecules (water, glucose,urea and salts) are squeezed out of the blood into the kidney tubule
R - Absorption - useful substances are reabsorbed back into blood capillaries wrapped round each kidney tubule
U - Urine - contains mix of toxic urea and excess salts & water
How many nephrons are in each kidney?
1 million
Where does ultra filtration take place?
in the Bowman’s capsule
what is ultra-filtration?
where glucose, urea and salts from the blood are filtered the Bowman’s capsule
what is reabsorbed back into the blood capillaries surrounding the nephron?
All the glucose, most water and some salts
where does the filtrate pass through (nephron)
the loop of Henle and collecting ducts, the amount of salt and water is regulated
how many litres of water does a human need per day?
2 litres
why do you need more water if it is hot or you do strenuous exercise?
because you will sweat
hypothalamus during thirst response
- has receptors which constantly monitor the bloods concentration of sodium and other substances
- receives impulses from sensors in blood vessels that monitor blood volume and pressure
when does the hypothalamus send out a strong message? (thirst)
when blood sodium concentration falls to low (from excessive sweating) or if blood sodium concentration rises to high (from eating salty snacks)
what does the hypothalamus increase?
the synthesis of ADH (anti-diuretic hormone) - causes more water to be reabsorbed from the urine, reducing urine volume - from the pituitary gland
when does dehydration occur?
when your body loses more fluid than you take in
during dehydration what happens to the blood plasma?
the water pot is reduced
early warning signs of dehydration
- thirst
- lightheaded and dry mouth
- tiredness
- dark-coloured, strong smelling urine
- passing urine less often than usual
what can severe dehydration lead to if left untreated?
can cause kidney damage and death
what is over hydration also known as?
hyponatremia
what is over hydration cause by?
increased water levels and low sodium (salt) levels
who does over hydration sometime affect? and why?
Athletes as their blood sodium level is reduced through sweat and then diluted by drinking large amount of water
over hydration symptoms
- nausea & vomiting
- headache
- in serious cases the brain can swell, causing confusion, seizures, coma and (in rare cases) death
what happens when you exercise?
you respire and sweat more, losing water, minerals, ions and glucose
your cells become dehydrated and can’t function properly
some sports drinks can help with this
what dialysis a possible treatment for?
Kidney failure - is essential for people who’s kidneys can’t keep the concentration of urea and salt at an optimum level to ensure that tissue damage doesn’t occur
How does the dialysis machine work?
- Patient is linked up to the dialysis machine and their blood flows into the machine. Machine contains fluid designed to have optimum concentration of salts - e.g. sodium & potassium ions and glucose as would be found in a healthy persons blood.
- The patients blood passes over a partially permeable membrane and the machine that is designed to replicate the kidney tubules. The dialysis fluid is on the other side of the membrane.
- A concentration gradient is established, allowing excess ions and urea to diffuse from an area of high concentration in the patients blood to an area of low concentration in the dialysis fluid
Advantages of dialysis
- gives patient more time to find a donor kidney
-
Disadvantages of dialysis
- it lasts 3-4 hours and is needed 3 times a week
- increased risk of blood clots and infections
- expensive process
