Homeostasis (blood glucose and body temp)

Question 1

Homeostasis

Answer 1

• The process of keeping the environment inside the body fairly constant
• A dynamic equilibrium – input and output of materials and energy are balanced
• Requires the body to sense and respond to both internal and external changes (stimuli)

Question 2

What’s a feedback system

Answer 2

• The body’s response to a stimulus where the original stimulus is altered
• Negative or positive

Question 3

What do feedback loops have and explain each

Answer 3

1. Stimulus – a change in environment
2. Receptor – detects the change
3. Modulator – control centre / processes the information
4. Effector – carries out the response
5. Feedback – change of the original stimulus

Question 4

Negative feedback

Answer 4

NEGATIVE - The feedback REVERSES the initial stimulus
Eg – blood glucose, body temperature, blood gas concentrations, blood water concentration
Gets it back to its original state

Question 5

Positive feedback

Answer 5

The feedback AMPLIFIES the initial stimulus
Eg – blood clotting, child birth
Adds more into into it

Question 6

Regulation of blood sugar (glucose)

Answer 6

glucose + oxygen = carbon dioxide + water + energy

• All cells need glucose for the energy required to function
• Our source of glucose is the food we eat
• Blood glucose levels rise sharply when we eat – excess glucose must be stored for use when required
• Stored glucose = glycogen

Question 7

What’s the role of the liver

Answer 7

Blood will enter the liver through the hepatic portal vein. Glucose will:
1. Be used for normal liver functioning by liver cells
2. Be removed from the blood and stored as glycogen
3.Be converted into fat for long-term storage if there is excess
4. Continue to circulate in the blood for use by body cells

Question 8

Role of pancreas (GLYCOGENESIS)

Answer 8

The conversion of blood sugar into glycogen for storage
- Under the influence of the hormone INSULIN
- Secreted by beta cells in the Islets of Langerhans

Question 9

Role of pancreas (GLYCOGENOLYSIS)

Answer 9

The conversion of stored glycogen back into glucose
- Under the influence of the hormone GLUCAGON
- Secreted by alpha cells in the Islets of Langerhans

Question 10

Role of pancreas (GLUCONEOGENESIS)

Answer 10

The conversion of stored sugars in fat in adipose tissues back into glucose
- Under the influence of the hormone GLUCAGON
- Secreted by alpha cells in the Islets of Langerhans

Question 11

Role of pancreas

Answer 11

Insulin will decrease blood glucose levels by:
1. Increase glucose uptake by body cells
2. Accelerating glycogenesis
3. Stimulating protein synthesis
4. Stimulating lipogenesis – storage of excess blood glucose into fat

Question 12

Thermoregulation (body temperature)

Answer 12

• 37oC is optimum temperature – vital for cellular reactions that are heat sensitive
• Heat gained by the body must equal heat lost
• Internal body temperature is a result of metabolic reactions and is usually higher than the external environment
• In situations of exercise and other strenuous activities, cellular reactions increase and the excess heat produced must be removed

Question 13

Thermoregulation (heat stroke)

Answer 13

• Body is unable to lose heat (eg high humidity)
• Can cause death if brain cells are affected

Question 14

Thermoregulation (heat exhaustion)

Answer 14

• Extreme sweating and vasodilation causing low blood pressure and possibly fainting
• Internal body temperature is within tolerance limits

Question 15

Thermoregulation (hypothermia)

Answer 15

• Core body temperature below 33oC
• Low metabolic rate and cannot maintain heat balance
• Death can occur below 32oC

Question 16

What are the types of thermoreceptors

Answer 16

• PERIPHERAL thermoreceptors = in skin and mucous membranes
  These detect stimuli and send impulses to the hypothalamus
• CENTRAL thermoreceptors = in hypothalamus
  These detect changes in the internal environment
• COLD receptors detect low temperatures
• HEAT receptors detect high temperatures

Question 17

Cooling mechanisms (skin)

Answer 17

• Large surface area = very effective
• Processes of heat loss from skin:
  1. Conduction = direct contact between particles of different surfaces (eg skin and clothes)
  2. Convection = moving air removes heat from skin
  3. Radiation = emission of heat as waves from skin
  4. Evaporation = sweat forming a gas which absorbs heat

Question 18

Cooling mechanism (vasodilation)

Answer 18

• Blood vessels in the dermis carry heat to the skin where it can be removed
• The diameter of these blood vessels can be increased under the control of the ANS
• Increased diameter = more blood is transported = more heat loss

Question 19

Cooling mechanism (sweating)

Answer 19

• Occurs when vasodilation is at maximum under sympathetic nervous control
• Evaporation removes heat
• Cooler skin cools blood by conduction

Question 20

Heating mechanism (vasoconstriction)

Answer 20

• The diameter of blood vessels is decreased under the control of the ANS
• Decreased diameter = less blood is transported = less heat loss

Question 21

Heating mechanism (shivering)

Answer 21

• Increased skeletal muscle contractions by way of tremors
• Occurs without work being done = heat gain

Question 22

Heating mechanism (goosebumps)

Answer 22

• Hair follicles direct hairs to become erect
• This creates a layer of air to form close to the skin
• Acts as an insulating blanket against the skin

Question 23

Behavioural mechanism (conscious cooling behaviours)

Answer 23

• Remove clothing
• Seek shade
• Turn on fans / air conditioning
• Increase surface area - spread out limbs

Question 24

Behavioural mechanism (conscious heating behaviours)

Answer 24

• Add clothing
• Eat or drink something warm
• Seek shelter
  Turn on heaters
• Decrease surface area – curl up
• Rub skin - friction