Homeostasis

Question 1

What is homestasis

Answer 1

The process keeping the body’s internal conditions relatively constant
- control systems are in charge of this

Question 2

What do control systems include

Answer 2

• receptor cells, they detect stimuli (changes in the environment)
• coordination centres that receive and process information from the receptors
• effectors, which bring about responses
  (Glands secrete hormones, muscles contract)

Question 3

What are the internal conditions controlled by homeostasis

Answer 3

• temperature
• body’s water content
• body’s ion content
• blood glucose levels

Question 4

Where are all the receptors found

Answer 4

• Eyes- sensitive to light
• Ears- sensitive to sound, and changes in position (enabling us to keep out balance)
• tongue and nose- sensitive to chemicals (enable us to taste and smell)
• skin- sensitive to touch, pressure, pain and temperature change
• brain- sensitive to blood temperature and water conc in blood
• pancreas- sensitive to blood glucose levels

Question 5

How does the body take in and lose water

Answer 5

Take ins via food and water

Takes out:
- via the lungs when we breathe out
- via the skin when we sweat
- via the kidneys in the urine

Question 6

How are ions lost from the body

Answer 6

• urea and ions are lost via the skin when we sweat
• excess ions are removed via the kidneys in the urine

Question 7

What are the body’s 2 main waste products

Answer 7

Carbon dioxide- dissolved carbon dioxide can form an acidic solution affecting enzymes in the body
Urea- poisonous, build up can cause damage

Question 8

What is urea

Answer 8

• when you eat more protein than you need, or when body tissues are worn out, the extra protein needs to be broken down as amino acids can’t be used to fuel the body
• the liver removes the amino group from the amino acids through deamination, this forms ammonia which is then converted into urea to be excreted
  (It passes from liver cells into the blood)

Question 9

What is the job of the liver

Answer 9

• deamination of excess amino acids to form urea
• detoxifying poisonous substances and passing the breakdown products into the blood to be excreted in the urine via kidneys
• breaking down old rbc and storing the iron until needed to synthesise more rbc

Question 10

What is the job of the kidneys
(Ions and water balance)

Answer 10

• kidneys filter blood
• glucose, ions, urea and water are all forced out of the blood into the kidney tubules, blood cells and large molecules like proteins can’t pass through the membrane of the tubule
• All of the glucose forced into the kidneys are reabsorbed back into the blood by active transport
• but the amount of water and ions reabsorbed will vary depending and how much the body needs, this is called selective reabsorption

ADH and water balance: (negative feedback mechanism)
- receptor cells in the brain detect water conc in the blood
- if the water conc is too low the pituitary gland secretes lots of ADH into the blood signaling the kidneys to reabsorbed more water back into the blood so less and more concentrated urine is produced
- if the water conc is too high the pituitary gland secrets less ADH so less water is reabsorbed back into the blood, forming a lot of dilute urine

Question 11

How is body temperature monitored

Answer 11

• body temp is monitored and controlled by the thermoregulatory centre in the brain. It has receptors sensitive to the temperature of the blood flowing through the brain
• temperature receptors on the skin send impulses to the thermoregulatory centre, giving info about skin temperature

Question 12

What happens when core temperature is too high

Answer 12

• blood vessels supplying the skin capillaries dilate (vasodilation) so more blood flows through the capillaries and more energy is transferred from the skin to the environment
• sweat glands produce more sweat which transfers energy from the skin to the environment as it evaporates

Question 13

What happens when core temperature is too low

Answer 13

• blood vessels that supply skin capillaries constrict (vasoconstriction) to reduce the blood flow through the capillaries reducing the amount of energy transferred from the skin
• muscles contract and relax rapidly, causing you to shiver. Contraction requires respiration which transfers energy to warm the body

Question 14

How are blood glucose levels maintained

Answer 14

• blood glucose levels are monitored and controlled by the pancreas
  -when blood glucose level rise (like after a meal) :
• the pancreas detects this change and produces the hormone insulin
• insulin allows glucose to move from the blood into cells where it is used
• insulin converts excess glucose into glycogen to be stored in the liver and muscles

When blood glucose levels fall:
- the pancreas produces the hormone glucagon causing glycogen to convert into glucose and be releases into the blood

Question 15

What are the 2 different types of diabetes

Answer 15

Type 1: genetic from birth
- pancreas does not produce enough insulin so blood glucose levels are too high
- eventually kidneys start to release glucose in the urine causing lots of urine and feeling thirsty all the time
- without insulin glucose can’t get into cells this can cause tiredness and lack of energy
- the body breaks down fat and protein to fuel itself instead, causing weight loss
(Controlled by careful diet, exercise and insulin injections)

Type 2: usually from obesity/genetic/develops
- the body stops responding to its insulin
(Controlled by careful diet, exercise and drugs)