Chapter 13 Excretion And Homeostasis Flashcards
What do arterioles do?
Bring oxygenated blood to the skin.
Define excretion:
The removal of waste products of metabolism and substances in excess of requirements
Define urea:
Waste product produced in liver from the breakdown of excess amino acids.
Define urine:
A solution of urea and other waste products in water
Produced by the kidneys
Define ureter:
A tube (one of a pair) that carries urine from the kidneys → bladder
Define urethra:
Tube that carries urine from bladder → outside
Why is carbon dioxide toxic for body cells?
Dissolves to form weak acid
→ lowers the pH of cells and the blood
How is urea removed from the blood?
It is removed by the kidneys
How is urine produced?
The kidneys produce urine by removing excess ions and water from the blood.
How does urine get transported to the bladder?
Kidneys → ureters → bladder
How does urine flow from the ureters out of the body?
The sphincter muscle at the entrance to the urethra relaxes and the urine flows out
Where is urea formed?
Liver
From what is urea made?
Excess proteins and amino acids
Why is excess proteins and amino acids removed from the body?
The body can’t store it
Where do digestive enzymes break proteins into amino acids?
Stomach, ileum, duodenum.
Where are amino acids absorbed?
They are absorbed into the blood capillaries in the villi in your ileum.
What is the hepatic portal vein formed of?
The blood capillaries of the villi in your ileum from this vein.
Where does the hepatic portal vein take the amino acids?
Liver
Are all protein and amino acids transformed to urea in the liver?
No, only the excess.
What happens to needed amino acids in the liver?
They are made into proteins and released into the blood.
What happens to excess proteins in the liver?
They are deaminated to carbohydrate and a nitrogen-containing compound.
What happens to the carbohydrates in the liver?
They are used or stored in the liver
What happens to the nitrogen-containing part of the compound in the liver?
Converted into urea
What happens to the urea after the liver?
It is dissolved in the blood plasma and taken to the kidneys.
Define deamination:
The removel of the nitrogen-containing part of amino acids to form urea.
Name the 2 main parts of the longitudinal section through a kidney:
Cortex and medulla.
Define cortex:
The tissue making up the outer layer in a kidney.
Define medulla:
Tissue making up the inner layers in a kidney.
Define a nephron:
One of the thousands of microscopic tubes inside a kidney where urine is made.
What is the tube leading from the kidney called?
Ureter
To where does the ureter lead?
Bladder
Where is the tube that leads urine out from the bladder?
Urethra
Where is the sphincter muscle?
Right below the bladder at the top of the urethra?
Describe where in a kid ney the nephron is situated:
Each nephron begins in the cortex, loops down into medulla, back into cortex, then goes down again through medulla.
Nephrons join up with the ureter.
Cortex → medulla → cortex → medulla → ureter
Define glomeruli:
(Singular glomerulus)
A little ‘network’ of blood capillaries, where blood is filtered in a kidney.
Through what does blood flow into the kidney?
Renal artery
In the kidney the RA devides into many tiny coiled capillaries (glomeruli)
What substances can be filtered through the glomerulus and move into the nephron? (What are the filtrate?)
1) Water
2) Urea
3) Glucose
4) Ions
Describe re-absorbtion in a kidney nephron:
Taking back required substances into the blood. (Like water and glucose)
Why are the blood capillaries close to the nephron?
It makes it easy for filtrate to move into and out of the blood.
What is the final liquid that flows out of the nephron?
A solution of urea and salts in water. urine
How much water is filtered by 2 kidneys in a day?
Approx. 170dm^3
How much urine is produced by 2 human kidneys per day?
Approx. 1.5dm^3
How can urine be an indication of how well hydrated a person is?
Dehydrated
Didnt drink alot of water / sweated alot
Small volumes concentrated urine
Dark colour urine
Hydrated
Drank more water than they need
Large volumes dilute urine
Lighter colour
Define homeostasis:
The maintenance of a constant internal environment.
Define internal environment:
Conditions inside the body.
Why is body temperature kept constant at 37 degrees?
It helps enzymes work at optimum rate.
Why should your body maintain a constant concentration of glucose?
So that there is always enough fuel for respiration.
Why would too much glucose in the blood be bad for a person?
Can cause water to move out of cells and into blood by osmosis
→ leaves cells w too little water to carry out their normal metabolic processes
What controls blood glucose concentration?
Hormones secreted by the pancreas.
Define insulin:
A hormone secreted by the pancreas, which decreases blood glucose concentration.
How many glands is the pancreas?
2
Through what does the pancreatic juice flow?
Pancreatic duct
Define glucagon:
A hormone secreted by the pancreas, which increases blood glucose concentration.
What cells in the pancreas secrete the two hormones glucagon and insulin?
Islets
Why are the cells in the pancreas called islets?
They are scattered across the pancreas and situated in small groups so they look like little islands among the other cells in the pancreas.
Where are the hormones transported to from the pancreas?
Through the blood to the liver
What happens when insulin reaches the liver?
It causes the liver to absorb glucose from the blood
-some used for respiration
-some turned into insoluble polysaccharide, glycogen
What happens when blood glucose concentration falls too low?
1) pancreas secretes glucagon
2) causes liver cells to break down the glycogen to glucose and release it into the blood
Where is glycogen stored?
Liver
Skeletal muscles
What is a normal concentration of glucose?
0.8 - 1.1mg per cm^3 of blood
What is the total volume of blood in our body?
5dm^3
Total volume of glucose circulating our bloodstream at any one time:
Minimum of 4g
Define set point:
The normal range/value for a particular parameter
Ex. The normal range of blood glucose concentration
The normal body temperature (37degrees Celsius)
Define negative feedback:
A mechanism that detects a move away from the set point, and brings about actions that take the value back towards the set point.
Define hormones:
Chemicals that are produced by a gland and carried in the blood, which alter the activities of their specific target organs.
Define type 1 diabetes:
A condition in which insufficient insulin is secreted by the pancreas, so that blood glucose concentration is not controlled.
What is thought to cause type 1 diabetes?
A persons immune system attacking and destroying the cells in the pancreas that secrete insulin.
What symptoms will a person with type 1 diabetes experience when their blood glucose concentration rises?
1) dry mouth
2) blurred vision
3) feel very thirsty
4) heart- and breathing rate may increase
How would a person with type 1 diabetes know when to eat something sweet to raise their blood glucose levels?
They are familiar with the symptoms experienced when having low blood glucose concentration.
They recognize when these occur and know how to counteract it.
1) Irritable behavior
2) Increased tiredness
Eventually they can become unconscious
Why cant a person who has T1 diabetes body raise their blood glucose concentration by secreting glucagon?
Because no insulin is excreted the liver hasn’t built any glycogen stores that can be broken down to produce glucose and be released into the blood.
Why must a person w T1 diabetes keep their blood glucose concentration within reasonably normal limits?
Because if they don’t it, over long periods of time, it can cause damage to organs.
How do you treat T1 diabetes?
Check blood glucose concentration often through:
1) blood drops on simple sensor
2) urine and simple dipstick
Eat little and often (avoid large amounts of carbohydrates) help blood glucose concentration fluctuating too widely.
Inject w insulin
What are 2 types of insulin?
1) Rapid-acting
-taken shortly before/after meal
-judge how much carbs they will eat (or have eaten) and adjust dose accordingly
2) Long-acting insulin
-taken once a day at the same time each day
-provides a background dose of insulin
What are the dead cells structure and function in controlling body temperature?
Structure:
-Skin is covered in layer of dead cells → tough impermeable barrier
Function:
-Prevents water from evaporating from living cells below
-Prevents pathogens from entering the body
Define sweat gland:
A structure found in the skin of mammals which secretes a watery fluid onto the skin surface to reduce body temperature.
Explain in detail the function of sweat glands:
They extract water and ions from the blood → produce sweat → travels up sweat duct to skin surface → released through pore
What is a venule?
Small vein
What is an arteriole?
Small artery
What is the function of arterioles?
Bring oxygenated blood to the skin
These divide to form capillaries that take blood just beneath skin surface
Then the capillaries join to form venules
What is the muscle attached to hair that is on the surface of skin called?
Hair erector muscle
What two receptors are under skin surface?
Pressure and temperature receptors
Define hypothalamus:
Part of the brain that is involved in the control of body temperature.
What does hypothalamus do?
Coordinates the activities of the body to help keep temperature of blood at its set point.
How does the hypothalamus work?
Contains temperature receptors that sense the temp of blood running through it
If its above/below 37degrees celsius → sends electrical impulses along neurones → to parts of body which have the function of regulating your body temperature
What does body do when temperature falls?
1) Muscles contract
2) Metabolism may increase
3) Hairs stand up
4) Vasoconstriction
5) Sweat glands reduce secretion
What does the body do when temperature rises?
1) Hairs lie flat
2) Vasodilation
3) Sweat production increases
Define vasoconstriction:
Narrowing of arterioles, caused by the contraction of the muscles in their walls.
Define vasodilation:
Widening of arterioles caused by the relaxation of the muscles in their walls.
