B3.3 Flashcards
What is homeostasis?
Maintenance of a constant internal environment.
Why is homeostasis important?
Keeps optimum conditions for enzyme action & all cell functions.
Where is the thermoregulatory centre found?
In the brain.
What does the thermoregulatory centre do?
Monitors and controls body temperature
What do receptors in the thermoregulatory centre detect?
Temperature of the blood.
What do skin receptors detect?
Send impulses about external temperature to the thermoregulatory centre.
What is the normal human body temperature?
37.5 degrees Celsius.
What happens when body temperature is too high?
Sweat produced from glands, evaporates from skin → energy transferred away from body
Vasodilation
What is vasodilation?
Blood vessels widen → more blood flows near skin → more energy lost.
What happens when body temperature is too low?
Sweating stops, skeletal muscles contract rapidly (shivering) - generate heat from respiration, hairs stand up - insulating layer:traps warm air, vasoconstriction
What is vasoconstriction?
Blood vessels narrow → less blood near skin → less heat lost.
Why must blood glucose be kept within limits?
Needed for respiration.
What organ controls blood glucose?
Pancreas
What happens when blood glucose is too high?
Pancreas releases insulin.
What does insulin do?
Binds to cells in target organs - liver + muscle.
What are insulin’s effects on the target organs?
1.glucose move from blood into muscle cells used for respiration
2. Excess converted to glycogen & is stored in liver
What happens to blood glucose after insulin acts?
It is reduced.
What happens when glucose levels are too low?
Pancreas releases glucagon.
Where does glucagon act?
Liver
What does glucagon do?
Binds to liver cells and breaks down glycogen into glucose
That glucose is then released into blood - increasing glucose concentration
How do insulin and glucagon maintain glucose levels?
Negative feedback.
What is negative feedback?
When a change occurs, a hormone is secreted to oppose it.
What causes an increase in blood glucose?
Eating foods that contain carbohydrates
What causes a decrease in blood glucose?
Rigorous activity - exercise
Glucose used for respiration for energy but then reduced in blood
What is type 1 diabetes?
Pancreas cannot make insulin.
What are the effects of type 1 diabetes?
High blood glucose, glucose in urine, lots of thirst.
How is type 1 diabetes treated?
Insulin injections at meals.
What is advised for type 1 patients?
Limit simple carbs (high in glucose).
What are researchers trying to do for type 1?
Pancreas + islet cell transplants, genetically engineer insulin.
What is type 2 diabetes?
Body cells stop responding to insulin.
Risk factor for type 2?
Obesity
How is type 2 treated?
Diet (less simple carbs), exercise & losing weight, drugs to improve insulin response.
What happens if blood water conc. increases?
Water moves into cells → swelling → lysis (bursting)
What happens if blood water conc. decreases?
Water leaves cells → shrink.
Why are kidneys important?
Maintain water + ion balance in the body
How do kidneys make urine?
Filter out waste products from blood at high pressure - water,ions,urea
And then selectively reabsorb useful substances - glucose, ions, water
What is removed from the blood?
Water, ions, urea (amino acids)
What is selectively reabsorbed?
Glucose, ions, water.
What is the outer part of the kidney called?
Cortex
What is the inner part of the kidney called?
Medulla.
What carries urine to bladder?
Ureter
What supplies blood to kidney?
Renal artery.
What removes blood from kidney?
Renal vein.
What are nephrons?
Millions of kidney tubules.
What is the glomerulus?
Ball of capillaries for selective reabsorption.
What is ADH?
Anti-diuretic hormone controlling urine water content.
Where is ADH made?
Pituitary gland but is released into pancreas.
What does ADH do?
Hormone involved in the control of loss of water as urine
When is ADH released?
When blood is too concentrated
Where does ADH act?
Travels in bloodstream to kidney tubules.
What does ADH do?
Increases permeability of tubules → more water reabsorbed back into blood
What is the result of more ADH?
More concentrated (yellow) urine - more water reabsorbed into blood
What happens in high temperatures to water & salt content?
More sweat → more salt loss. - dehydration too
How do kidneys respond to dehydration?
Retain more salt.
What does the brain do during dehydration?
Makes us feel thirsty → drink water to dilute salt in our blood
