Homeostasis (blood glucose and body temp) Flashcards
Homeostasis
- 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)
What’s a feedback system
- The body’s response to a stimulus where the original stimulus is altered
- Negative or positive
What do feedback loops have and explain each
- Stimulus – a change in environment
- Receptor – detects the change
- Modulator – control centre / processes the information
- Effector – carries out the response
- Feedback – change of the original stimulus
Negative feedback
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
Positive feedback
The feedback AMPLIFIES the initial stimulus
Eg – blood clotting, child birth
Adds more into into it
Regulation of blood sugar (glucose)
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
What’s the role of the liver
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
Role of pancreas (GLYCOGENESIS)
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
Role of pancreas (GLYCOGENOLYSIS)
The conversion of stored glycogen back into glucose
- Under the influence of the hormone GLUCAGON
- Secreted by alpha cells in the Islets of Langerhans
Role of pancreas (GLUCONEOGENESIS)
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
Role of pancreas
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
Thermoregulation (body temperature)
- 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
Thermoregulation (heat stroke)
- Body is unable to lose heat (eg high humidity)
- Can cause death if brain cells are affected
Thermoregulation (heat exhaustion)
- Extreme sweating and vasodilation causing low blood pressure and possibly fainting
- Internal body temperature is within tolerance limits
Thermoregulation (hypothermia)
- Core body temperature below 33oC
- Low metabolic rate and cannot maintain heat balance
- Death can occur below 32oC
What are the types of thermoreceptors
- 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
Cooling mechanisms (skin)
- 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
Cooling mechanism (vasodilation)
- 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
Cooling mechanism (sweating)
- Occurs when vasodilation is at maximum under sympathetic nervous control
- Evaporation removes heat
- Cooler skin cools blood by conduction
Heating mechanism (vasoconstriction)
- The diameter of blood vessels is decreased under the control of the ANS
- Decreased diameter = less blood is transported = less heat loss
Heating mechanism (shivering)
- Increased skeletal muscle contractions by way of tremors
- Occurs without work being done = heat gain
Heating mechanism (goosebumps)
- 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
Behavioural mechanism (conscious cooling behaviours)
- Remove clothing
- Seek shade
- Turn on fans / air conditioning
- Increase surface area - spread out limbs
Behavioural mechanism (conscious heating behaviours)
- Add clothing
- Eat or drink something warm
- Seek shelter
Turn on heaters - Decrease surface area – curl up
- Rub skin - friction
