Homeostasis And The Kidneys Flashcards
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment to keep conditions at an optimum. The nervous system and hormones are responsible for this.
What are hormones?
A hormone is a chemical messenger produced in the endocrine glands and carried in the blood to a target organ
What is glucose needed for?
Is needed by cells for respiration
What is insulin?
Insulin is a hormone produced by the pancreas that regulates glucose levels in the blood
What happens when there is low glucose in blood?
- Insulin not secreted into the blood
- Liver does not convert glucose into insoluble glycogen
- Glucose blood level increases
What happens when there is too high levels of glucose in the blood?
- In pancreas, insulin secreted into the blood
- Liver converts glucose into insoluble glycogen for storage
- Glucose blood levels decreases
What system helps control homeostasis?
negative feedback mechanisms:
if the level of something rises, control systems reduce it again
if the level of something falls, control systems raise it again
5 processes of negative feedback mechanisms?
- Conditions in the body change from a set point
- Change is detected
- Corrective mechanisms activated
- Conditions return to set point
- Corrective mechanisms switched off
What are enzymes?
A protein which catalyses or speeds up a chemical reaction
Ideal body temperature?
37*c
What happens to our hair when we are too warm?
the hair erector muscle relaxes, lowering the hair
a thin insulating layer of air is trapped above the skin
more heat is lost to the environment
What happens to our hair when we are too cold?
he hair erector muscle contracts, raising the hair
the hairs trap a thicker layer of air above the skin
the air insulates the skin against heat loss
What is vasoconstriction?
cold picked up by thermoreceptors
brain sends nerve impulses
the narrowing of blood vessels (Arterioles) at the skin surface to reduce heat loss through the surface of the skin
What is vasodilation?
hot picked up by thermoreceptors
brain sends nerve impulses
the widening of blood vessels (Arterioles) at the skin surface to increase heat loss through the surface of the skin
Why do we shiver when we are cold?
- involuntary contractions by muscles
- muscle contractions require energy from respiration which releases heat
- the heat is used to warm us up
Why do we sweat when we are hot?
- sweat is produced in sweat gland
- travels up sweat duct, out of sweat pore onto skin
- will evaporate, and takes excess body heat with it
What is tropism?
A plants growth response to light, water or gravity
What is phototropism?
growth response where the stimulus is light
What is gravitropism/geotropism?
growth response where the stimulus is gravity
What is positive tropism?
plant grows towards the stimulus
Stems response to light?
positive phototropism (grows towards the light) the shaded side contains more auxin and grows longer – causing the stem to bend towards the light
Roots response to gravity?
positive geotropism (grows in the direction of the force of gravity)
What is auxin?
Auxin is a family of plant hormones
Auxin change the rate of elongation in plant cells, controlling their length
How do stems and roots respond with high concentrations of auxin?
cells in stems grow more
cells in roots grow less
What is diabetes?
Diabetes is a condition in which the blood glucose levels remain too high
Treated with insulin
Type 1 and type 2
How is blood glucose level reduced?
insulin causes the liver to convert glucose into glycogen, which reduces the blood glucose level
What is type 1 diabetes?
damage to the beta cells in the pancreas
can be inherited, but can also be caused by contracting particular viruses and the body’s response to them
people with type 1 diabetes produce little or no insulin.
How can type 1 diabetes be treated?
following a low sugar/carbohydrate diet
injecting insulin
possible transplant of pancreatic tissue
What effects amount of insulin needed?
Diet (often raises glucose) and exercise levels (lowers glucose)
What is type 2 diabetes?
a person’s body becoming resistant to insulin
there is a link between rising levels of obesity and increasing levels of type 2 diabetes
Factors that contribute to the onset of type 2 diabetes?
- Poor diet (high in sugar and fat)
- Little exercise (a high BMI, obesity)
- Drinking too much alcohol
- Misuse of drugs
What does alcohol increase?
Reaction time, which is particulary bad if someone is driving
Its an addictive substances, people have withdrawal symptoms without it
Where are the kidneys located?
The back of the abdomen
What are the two functions of the kidneys?
they regulate the water content in the blood
they excrete/remove the toxic waste products of metabolism
How does the kidney filter blood?
Blood is brought to the kidney in the renal artery which branches off the aorta
The kidney regulates/controls the water and salt content and removes urea
The filtered excess water, salts and urea form a liquid called urine
The urine is transported to the bladder along tubes called ureters
The bladder stores the urine until it is convenient to expel it from the body through the urethra
The purified blood returns to the circulation through the renal vein and to the heart through the vena cava
What is the nephron and what does it do?
The kidney is packed with around a million structures called nephrons.
The nephron regulates the level of water, and salts and removes urea from the blood.
How does the nephron work?
The Bowman’s capsule (renal capsule):
surrounds a ball of capillaries called the capillary knot
high pressure is created in the capillary knot by the diameter of the capillary leaving the knot being narrower than the capillary entering
this pressure results in ultrafiltration where water, salts, glucose, and other small molecules pass out of the capillary and into the Bowman’s capsule
proteins and blood cells are too big to leave the capillaries to go into the tubule
How does the tubule and collecting duct work?
The rest of the tubule is responsible for the selective reabsorption of glucose, some salts, and lots of the water.
The collecting duct is responsible for the selective reabsorption of water and for sending urine to the ureter.
What is ADH?
Anti-diuretic hormone
It is a hormone that controls amount of water in blood
What is blood plasma?
The liquid part of blood containing glucose, amino acids, minerals and hormones, but also harmful products like urea.
What 3 factors change the concentration of the blood?
excess drinking (increases water content) excess sweating (decreases water content) consumption of salty foods (decreases water content)
What happens when there is too little water in the blood?
Brain detects water level Pituitary gland releases ADH More water reabsorbed by kidneys Less water lost in urine Blood water levels return to normal
What happens when there is too little water in the blood?
Brain detects water level Pituitary gland releases LESS ADH Less water reabsorbed by kidneys More water lost in urine Blood water levels return to normal
What does glucose in urine suggest?
The person is diabetic
The glucose levels in the blood are so high the kidney is unable to reabsorb it and it leaves the body in urine
What does protein in the urine suggest?
Indicates to damage in the kidney
generally proteins in the blood are too large to pass through into the nephron tubule
What is dialysis treatment?
To remove toxic urea, and to maintain the correct balance of salts and water in the body, a patient whose kidneys are not working properly needs to spend many hours a week attached to a dialysis machine.
Advantages of dialysis?
It can keep a patient alive whilst they are waiting for a suitable donor to be found.
It does not involve major surgery
Disadvantages of dialysis?
Patients need to follow a carefully controlled diet.
Patients need to spend many hours every week attached to a dialysis machine.
Dialysis machines are very expensive.
Dialysis will only be successful for a certain amount of time.
What is meant by ‘rejection’ in transplants?
An organ is rejected if it get attacked by the immune system in an autoimmune response
What are immunosupressents?
Drugs that prevent the immune system attacking an organ
Disadvantage - makes recipient more suseptable to other illnesses
Advantages of transplants?
Once the transplant has occurred the patient no longer has diet restrictions.
Long periods of time on dialysis are no longer necessary.
Although not a life-long cure, a kidney transplant will generally allow the patient to live a fuller life for longer than a patient on dialysis.
Disadvantages of transplants?
It is difficult to find a donor organ with a matching tissue type.
The risk of organ rejection.
Having to take drugs which suppress the immune system, leaving the patient susceptible to contracting other diseases.
Regular doctors’ appointments to detect signs of organ rejection.
Major surgery is required.
How does a dialysis machine work?
Blood is removed from the patient and flows into the dialyzer where it is kept separated from dialysis fluid by a partially permeable membrane.
The dialysis fluid contains the same concentration of glucose and salts as normal blood plasma so there is no net movement of glucose out of the blood by diffusion.
Excess salts diffuse into the dialysis fluid.
The dialysis fluid contains no urea, so all of the urea diffuses from the blood in to the dialysis fluid from the high concentration in the blood to the lower concentration in the dialysis fluid.
The blood and dialysis fluid move in opposite directions across the membrane (a counter current system) in order to maintain concentration gradients all the way along.
The clean blood is returned to the patient and the waste dialysis fluid is disposed of.
