Chapter 7 - Homeostasis Of Body Temperature Flashcards
What is thermoregulation?
Maintaining the balance between heat production and heat loss
What is the optimum body temperature?
37 degrees Celsius
What causes heat input?
- heat from body processes (metabolism), especially respiration of muscle and liver cells
- heat gained from surroundings by conduction and radiation
What causes heat output?
- radiation, convection and conduction to surroundings
- evaporation of water from skin and lungs, warm air breathed out, warm urine and faeces
What does a high temperature above normal cause?
Enzymes denature, change shape, disrupts cellular activity
What is higher, internal or external temperature?
Internal due to metabolism
Cold conditions: to decrease heat loss
- vasoconstriction
- reduction in sweating
- conscious behaviour such as putting on a jumper
- reduction of surface area by curling into a ball
Cold conditions: to increase heat production
- shivering
- increase in voluntary activity
- increased metabolic rate
Hot conditions: to increase heat loss
- vasodilation
- increase in sweating
- conscious behaviour
- increase surface area by spreading out
Hot conditions: to decrease heat production
- decrease in voluntary activity
- decreased metabolic rate
Where are peripheral thermoreceptors found?
Skin and mucous membranes
Where are central thermoreceptors found?
Hypothalamus
What are the two types of peripheral thermoreceptors?
- cold receptors: stimulated by temperatures lower than normal
- heat receptors: stimulated by temperatures higher than normal
Where are other central thermoreceptors located?
Spinal cord and abdominal organs, connected to hypothalamus
What is the body’s main temperature regulation centre?
Hypothalamus
What would peripheral receptors alone not be efficient in temperature regulation?
Because it is the core body temperature that needs to be controlled
What controls vasoconstriction and vasodilation?
Autonomic nerves
What is sweating?
The active secretion of fluid by the sweat glands and the periodic contraction of cells surrounding the ducts to pump sweat to the skin surface
What is sweat made of?
Water, sodium chloride, urea, lactic acid and potassium ions
How does sweat work to increase heat loss?
Evaporation of sweat from the body has a cooling effect: heat is removed from the skin when liquid sweat changes into vapour
What stimulates secretion of sweat?
Sympathetic nerves
What is shivering?
Rhythmic muscle tremors that occur at a rate of 10-20 per second
At what temperature does death occur?
Above 45 degrees
What causes heat exhaustion?
When extreme sweating and vasodilation occurs to lose heat
What happens when the body is heat exhausted?
- the loss of water in sweating reduces the volume of blood plasma and vasodilation reduces resistance to blood flow
- blood pressure is decreased and the output of blood from the heart is reduced
What is hypothermia?
When a persons core temperature falls below 33 degrees, the metabolic rate is so low that heat production is unable to replace heat lost and body temperatures continue to fall
What is heat stroke?
When humidity is high and it is difficult for the body to lose heat by radiation or evaporation
