B3.3 Maintaining Internal Environments Flashcards
(21 cards)
What happens when you are exposed to extreme cold?
- exposure to extreme cold reduces the core body temperature:
- enzyme reactions occur too slowly
- respiration does not produce enough energy
- cells begin to die
- if core body temperature drops below 35 degrees Celsius, you are at risk of hypothermia
What happens when you are exposed to very high temps?
- exercise, exposure to very high temperatures and some infections can cause the body to overheat
- energy transfer to molecules is too much
- enzymes denature
- respiration/cells don’t work effectively
What is responsible for regulating body temp?
- The thermoregulatory centre in the brain is responsible for regulating body temperature.
- It relies on signals received from receptor cells in your skin ( to monitor the external environment) and from internal receptor cells ( to monitor the temperature in your blood ).
- When a change in temperature is detected, the brain causes different parts of the body to respond by sending I impulses to effectors. These responses return the body back to its normal temperature.
What happens if you get too hot?
If you get too hot, your brain triggers changes that work to cool you down:
- The hairs on your skin lie flat, preventing an insulating layer of air being trapped around the body.
- Sweat glands produce swear. The water in the sweat evaporates, and energy is transferred by heating from the body to the environment, reducing your temperature.
- Blood vessels supplying capillaries near the surface of the skin widen. This is known as vasodilation and it increases blood flow through the capillaries, increasing heat loss by radiation.
What happens if you get too cold?
If you get too cold, your brain triggers brain triggers changes that work to prevent heat loss:
- Body hairs rise, trapping a layer of air close to the skin. This insulates the body.
- Sweat glands stop producing sweat.
- Blood vessels supplying capillaries near the surface of the skin narrow. This is called vasoconstriction and it reduced blood flow through the capillaries reducing heat loss.
- Shivering begins where muscles contract and relax quickly. This makes cells respire more quickly, transferring extra energy by heating.
How do glucose levels drop?
More glucose is needed during exercise a the body needs to transfer more energy, causing blood sugar levels to drop. This prevents cells from respiring effectively.
How do glucose levels rise?
After eating, the glucose released by digestion passes into the bloodstream, which causes blood sugar levels to rise. If this is maintained over a long period of time the body systems can be damaged, especially the nerves and blood vessels.
Negative feedback system for high blood sugar levels
High blood sugar levels detected by the pancreas —> Pancreas releases the hormone insulin —> Insulin travels in the blood to the liver —> It stimulates the liver to turn glucose into glycogen by a series of enzyme controlled reactions —> glycogen is then stored in the liver —> Sugar levels drop as there is now less sugar in the blood
Negative feedback system for low blood sugar levels
If the blood glucose concentration is too low the pancreas releases the hormone glucagon —> glucagon makes the liver change glycogen back to glucose —> Glucose is released into the blood and blood sugar levels increase back to normal
Type 1 diabetes
- People with type 1 diabetes cannot produce insulin. The person’s own immune system has destroyed the pancreatic cells that make insulin. This condition normally begins in childhood. It is controlled by regular injections of insulin. A type 1 diabetic should also eat a balanced diet and exercise regularly.
Type 2 diabetes
- Type 2 diabetics cannot effectively use insulin. The person’s cells do not produce enough insulin or the person’s body cells do not respond properly to insulin. It normally occurs later in life and has been linked to obesity. Type 2 diabetes is controlled by regulating a person’s carbohydrate intake through their diet and matching thi to their exercise levels. Overweight patients should also lose weight to alleviate symptoms. Sometimes drugs may be given to stimulate insulin production or insulin injections are given.
How do water and salts enter and exit the body?
- Your body has to regulate the amount of water and salts that are present. Water and salts enter the body through consuming food and drink, but water is also produced through respiration. Water and salts are lost through sweating and in urine. Water also leaves the body as water vapour when you exhale. Removal of waste products is known as excretion.
Capsule, cortex, medulla
Capsule - outer membrane of the kidney which helps to maintain the kidney’s shape and protect it from damage.
Cortex - outer part of the kidney
Medulla` - inner part of the kidney
Nephrons
Urine is produced in microscopic tubules called nephrons, inside the kidney. Each kidney contains approximately 1 million nephrons. The top of the nephron is found in the cortex and the lower section (loop of henle) is found in the medulla.
Explain the pathway of blood (ultrafiltration, selective reabsorption)
Blood enters the kidney under high pressure from the renal artery, which contains many branches, each of which leads to the glomerulus. Each glomerulus contains a knot of capillaries.
The blood vessels narrow at the exit to the glomerulus, so increasing the blood pressure here. The increased blood pressure forces small molecules, including water, glucose, salts, and urea, out through the capillary wall into the Bowman’s capsule. Large molecules, such as proteins, are too large to fit through the capillary wall so they remain in the bloodstream.
Next, selective reabsorption takes place. As the filtrate moves through the nephron tubule all of the glucose, some water, and salts needed by the body is reabsorbed into the bloodstream. The filtrate passes through the loop of Henle and the collecting ducts. These structures regulate the amount of salt and water in the body by re absorbing extra water and salt if needed. Excretion then occurs, and the waste solution, urine, collects in the collecting ducts. It travels to the bladder before it is removed from the body.
(Proximal convoluted tubule then distal convoluted tubule)
How does the body control how much urine is produced?
The volume o urine produced is controlled through a negative feedback loop. Your hypothalamus detects the water potential of your blood as it passes through the brain. It responds by secreting the hormone ADH from the pituitary gland. ADH travels in the bloodstream to the kidney where it makes the walls of the collecting ducts more permeable to water. This means more water is reabsorbed into the blood.
If the blood water potential is too low…
Low water potential —> More ADH produced —> More water reabsorbed from nephron into bloodstream —> Less water lost from body —> Small volume of concentrated urine produced
If the blood water potential is too high…
High water potential —> Less ADH produced —> Less water reabsorbed from nephron into bloodstream —> More water lost from body —> Large volume of dilute urine produced
How does the body respond to a lack of water?
A reduction in the water potential of your blood plasma, or increased salt concentration, triggers the thirst response. An impulse is sent to the brain, which informs you to take on more fluids. The kidney responds by producing less urine. If you do not take on more fluids, you will become dehydrates, which can lead to kidney and liver failure.
How does the body respond to too much water?
Taking in too much water, or not enough salts, causes the water potential of your blood plasma to rise above the water potential of your cells. Your kidneys respond by increasing the volume of urine produced. However,, if a large volume of water is consumed rapidly, water will move by osmosis into your cells. This may cause these cells to burst. The concentration of sodium in the blood plasma also drops. This can lead to muscle cramping, confusion, and seizures. In extreme circumstances, when water moves into brain cells by osmosis, it can lead to death.
Explain sport drinks
Sports drinks are especially designed to enable us to exercise or compete in an event and perform as well as possible.
When you exercise you:
- respire more, using up glucose
- sweat more, losing electrolytes and water
- cells will become dehydrates if not replaced
Sports drinks replace water, sugars and electrolytes
