Keeping Internal Conditions Constant Flashcards
What is homeostasis?
The maintenance of constant internal body conditions
What body conditions must be controlled for homeostasis?
- Temerature
- Blood glucose level
- Water levels
- Ion content levels
- Levels of waste products
What waste products are removed by the body and how?
- CO2 produced by respiration is removed via the lungs when we breathe out
- Urea, produced in the liver from the breakdown of amino acids, is removed by the kindeys in urine and temporarily stored in the bladder
How do water and mineral ions enter the body?
When we eat and drink
What could happen if the water or ion content of the body is wrong?
To much water may move into or out of the cells
This could destroy or damage the cells
What does the kindey do?
Filters the blood, excereting substances you do not want and keeping those your body needs
How do the kindeys produce urine?
- First filtering the blood
- Reabsorbing all the sugar
- Reabsorbing the dissolves ions needed by the body
- Reabsorbing as much water as the body needs
- Releasing urea, excess ions, and excess water in the urine
Where does the urine go before it exits the body?
It is temporarily stored in the bladder
What is the ureter?
Tube through which urine passes from the kindey to the bladder
What is the urethra?
Tube through which urine passes to the outside of the body
What are the names of the blood vessels that supply blood to the kindeys and take it away?
The aorta and renal artery
The renal vein and vena cava
What does the renal artery and renal vein do?
Renal artery brings blood containing urea + other susbstances in solution to the kidney
Renal vein carries blood away after these have been removed
Why don’t we constantly piss all the time?
There’s a ring of at the bottom of the bladder which controls when it opens and closes
What is dialysis?
The process of cleaning blood through a dialysis machine when a person’s kindeys don’t work properly or have failed
How does dialysis work?
- The dialysis fluid contains the same concentration of useful substances (ions + sugars) as the patient’s blood
- This means that they do not diffuse out of the patient’s blood so do not need to be reabsorbed
- Urea diffuses out from the blood into the fluid
- Dialysis restores the concentration of substances in the blood back to normal, but needs to be carries out at regular intervals
If a person has a kindey transplant, what will this mean?
They will no longer require further dialysis
Draw and label a diagram of the process of dialysis
The dialysis machine has a partially permiable membrane
Blood cells and proteins are too large to pass through this
How can kidney rejection be prevented?
- Must be a very good ‘tissue match’
- Following the transplant, the recipient must take drugs to suppress the immune response to prevent rejection
- These are called immunosuppressant drugs
What would cause a kidney to be rejected?
- There are proteins called antigens on the surface of cells
- These act as markers for the cells and body
- The recipient’s body may recognise these as ‘foreign’
- This would cause the immune response, which is to release antibodies to attack and kill the foreign cells
What are the advantages of kidney transplants over dialysis?
- Cheaper (for patient/NHS)
- Patient no longer requires dialysis
What are the disadvantages of kidney transplants?
- Some risks from the operations
- Immunosuppressant drugs need to be taken before and after the opperation. This leaves the patient vulnerable to infection
How is the new kidney usually positioned in the body?
In the groin, attached to the blood vessels + bladder
The old kidneys are left in the body
What is the core body temperature and why must it be kept constant?
37°
Must be kept constant so enzymes work efficiently and do not denature
What monitors and controls body temperature?
The thermoregulatory system in the brain
It detects and controls blood temperature only
How is blood temperature monitored?
- The thermoregulatory centre has receptors which detect the temperature of the blood flowing through the brain
- Temperature recepters in the skin also send implulses to the brain to give information about skin temperature
What happens if the core body temperature rises?
- Blood vessels near the surface of the skin dilate allowing more blood to flow through the skin capillaries
- Energy is transfered by radiation and the skin cools
- Sweat glands produce more sweat. The water evaporates from the skin’s surface
- The energy required to make the water evaportate comes from the skin, so it cools down
What happens if the core body temperature falls?
- Blood vessels near the surface of the skin constrict and less blood flows through the skin capillaries
- This means less energy is lost by radiation
- We ‘shiver’. Muscles contract quickly. This requires respiration
- Some of the energy released by this warms the blood
- Hairs on the skins surface become erect
- This traps a layer of insulating air
What do doctors need to consider when thinking of treating patients with kidney failure using dialysis or a transplant?
- The general health of the patient
- How long the patient has been on dialysis
- The total cost of the treatment - long term costs of dialysis vs. operation costs + drugs
- Risks of operation - anaethetics, infection
- The availability of donor kindeys
What are the ethical issues surrounding kindey transplants and dialysis?
- Should everyone automatically be on a transplant register or should they opt in?
- Should people be paid to be donors?
- Should people pay for a new kidney to jump the queue?
- Should people be given a preference? E.g. the young
Why is it important to carry a donor card or tell your family you want to be a donor?
It is distressing to families having to make a descision immediately after the death of a loved one
You can decide what happens
Small children have a large surface area to volume ratio. What can this cause?
- They transfer energy to the surroundings very quickly in cold conditions and dehydrate quickly in hot ones
- If the body temperature is too low the respiratory enzymes work too slowly and too little energy is released
- If the child dehydrates they cannot cool down and overheat, meaning that enzymes denature
What can happen to elderly people in cold conditions and why?
They can suffer from hypothermia in cold conditions because they do not move around much to release energy from respiration in muscles
What do explorers in extreme environments have to learn how to recognise?
The symptoms of hypothermia and dehydration
Why can extreme temperatures be dangerous for survival?
Because the body’s enzymes do not work properly
Which organ controls and monitors the level of glucose in the blood?
The pancreas
What does the pancreas do if there is too much glucose in the blood?
Produces the hormone insulin
What does insulin do?
Causes blood glucose levels to fall
Causes glucose to move from the blood into our cells
What happens to excess glucose in the liver?
It is converted into glycogen for storage
What is Type 1 diabetes?
Diabetes caused when the pancreas produces none or too little insulin.
Causes the blood glucose level to become very high
Usually occurs in children and young adults and lasts throughout their lives
How is Type 1 diabetes controlled?
By regular injections of insulin
Careful attention to diet
Carful attention to levels of exercise
Describe fully how blood glucose level is controlled in the body
- Insulin causes blood glucose levels to fall
- If the level gets too low receptors in the pancreas detect this
- The pancreas released glucagon, another hormone
- The glucagon causes the glycogen in the liver to change into glucose
- The glucose is released back into the blood
What do some diabetics use instead of injections?
Pumps attached to the body
They can adjust the level of insulin injected by the pump
What are the new methods of treating and potentially curing Type 1 diabetes that are currently being developed?
- Pancreas transplants
- Transplanting pancreas cells
- Using embryonic stem cells to produce insulin secreting cells
- Using adult stem cells from diabetic patients
- Genetically engineering pancreas cells to make them work properly
