B9: Animal physiology 3 Flashcards
homeostasis is
maintenance of a constant internal environment.
involves maintaining internal conditions within set limits.
why is homesotatis impotant
Internal conditions that need to be kept steady relate to the composition of tissue fluid and include water content and nutrient concentrations, as well as temperature.
Major fluctuations that are not promptly rectified could result in the death of the organism.
thermoregulatory centre in the brain
monitor blood temperature
receives information from temperature receptors in the skin.
rise in body tem
detected by the thermoregulatory centre it send nerve impulses to the skin, effectors (arterioles and sweat glands) responding. The arterioles dilate (vasodilation) sweat glands secrete more sweat.
result in the cooling of the skin,
which brings down the elevated body core temperature.
low body temp
thermoregulatory centre detects this
sends nervous impulses
to switch off the processes of vasodilation and sweating,
triggering other responses, vasoconstriction and shivering.
This is negative feedback.
The regulation of blood glucose levels
liver
Responding to an increase in blood glucose levels
After a meal, blood glucose concentrations rise
as a result of the digestion of carbohydrates.
glucose is absorbed into the blood stream,
glucose levels in the blood to rise.
excess blood glucose is removed by the liver
and converted into glycogen.
controlled by the hormone insulin.
blood glucose levels rise, the islet cells
of the pancreas detect the change and secrete insulin in response.
insulin transported to the liver in the blood plasma.
at the liver, insulin stimulates liver cells to take up the glucose from the blood and convert it to glycogen.
Insulin also stimulates other body cells to take up more glucose for use in respiration.
Responding to a decrease in blood glucose levels
the islet cells in the pancreas are stimulated to release a different hormone – glucagon.
Glucagon is transported by the blood plasma
to the liver
where it acts on the cells there,
causing them to convert stored glycogen back to glucose
to raise blood glucose levels.
Type 1 diabetes
first appears in young people
an inability of the pancreatic islet cells to secrete enough insulin
to control blood glucose correctly.
can be inherited.
can also be triggered by an event such as a viral infection.
The infection causes the body’s immune system to attack the islet cells of the pancreas, so they stop producing sufficient insulin. Type 1 diabetes is an example of an autoimmune disease, when caused by a viral infection.
Symptoms of type 1 diabetes
feeling tired feeling very thirsty frequent urination weight loss. There may be glucose present in the urine.
Eating a meal high in carbohydrates can result in the diabetic falling into a coma. Similarly, a shortage of food can result in the diabetic falling into a coma.
Control of type 1 diabetes
regulated diet - stop blood glucose levels from fluctuating too much.
Regular blood tests to monitor blood glucose levels.
Regular injections of insulin to control blood glucose levels.
Type 2 diabetes
common form of diabetes
common in older people and certain ethnic groups.
can be inherited or a result of obesity, lack of exercise and an unhealthy diet (too much fat and a lack of fibre).
These factors can lead to insulin resistance,
where the body doesn’t use insulin properly.
too much water - control
- high water conc of blood
-brain coordinates response
instructs pitutiary gland to secrete
less ADH
-low volume of water reabsorbed by kidney - high urine outpit
too little water - control
- low water conc of blood
-brain coordinates response
instructs pitutiary gland to secrete
more ADH
-high volume of water reabsorbed by kidney - low urine outpit
