Homeostasis & Thermoregulation Flashcards
What is homeostasis?
The process of keeping the environment inside the body constant
What does homeostasis maintain?
- Core body temperature
- pH concentration
- Concentration of glucose
- Concentration of oxygen and CO2
- Blood pressure
- Concentration of metabolic wastes
What is it meant by a dynamic equilibrium?
When there are fluctuations around a normal level
What does positive feedback refer to?
Response is reinforced or intensified which results in a greater response eg child birth - oxytocin
What does negative feedback refer to?
Negative feedback has the effect of reducing or eliminating the stimulus caused eg air conditioning
What is the difference between negative and positive feedback?
Negative feedback has the effect of reducing or eliminating the stimulus that caused where as positive feedback reinforces and intensifies the stimulus eg oxytocin in childbirth
What does the term thermoregulation refer to?
The maintaining the balance between heat production and heat loss
List the body’s heat inputs?
- Heat from body processes such as respiration of liver and muscle cells
- Heat gained from surroundings by conduction and radiation
Lost the body’s heat outputs?
- Radiation , conduction and convection to surroundings
- Evaporation of water from skin and lungs, warm air breathed out
What ways are there to loss some but retain heat during hot conditions?
- Sweating
- Dilation of blood vessels in the skin
- Conscious behaviour such as removing clothes
- Increase surface area of body by spreading out
What are the ways to reduce heat in hot conditions?
- Decrease in voluntary activity
- Decreased metabolic rate (long term response)
What are the ways to retain heat in cold conditions?
- Constriction of blood vessels in the skin
- Reduction in sweating
- Conscious behaviour such as putting on a jumper
- Reduction in surface area by curling up in a ball
What are the ways to increase heat production in cold conditions?
- Shivering
- Increase in voluntary activity
- Increases metabolic rate (long term response)
What are the three ways metabolic rate is affected?
- Exercise
- Stress
- Rising body temperature
How does exercise affect metabolic rate?
During exercise muscular activity increases metabolic rate by up to 40 times which leads to an increase in heat production
How does stress affect metabolic rate ?
Stress also increases metabolic rate as the activities of the autonomic division of the nervous system. Stimulation of sympathetic nerves release noradrenaline which increases metabolic activity of the cells
How does rising body temperatures affect metabolic rate ?
For each 1 degrees rise in temperature, the rate of biochemical reactions increased by 10% therefore Increasing metabolic rate
What are the body’s thermoreceptors?
- Peripheral thermoreceptors - those in the skin and mucous membranes, cold and hot receptors
- Central thermoreceptors - located in the hypothalamus
- Other internal receptors - located in the spinal cord
What role does the skin play in regulating temperature?
- Changes in the skin can speed up or slow down the rate at which heat is lost from the body
- Blood vessels carry heat to the skin from the core of the body
- Heat can be lost from the skin by conduction, convection, radiation, evaporation
- When large amounts of body heat must be lost by the skin and blood vessels are already at maximum dilation, sweating must occur
What is sweating?
The active secretion of fluid by sweat glands periodic contraction of cells surrounding the ducts to pump sweat to the skin surface is stimulated by sympathetic nerves
How does evaporation work?
Evaporation of sweat from the skin has a cooling affect: heat is removed from the skin when liquid changes into vapour
What is conduction?
When heat is transferred to another object by direct contact , heat is transferred from a hot object to a cold object
What is convection?
Heat leaves the body and moves away as air currents (convection currents) the faster the flow of the air, the faster the rate heat is transferred
What is evaporation?
The conversion of a liquid to a vapour the surface is cooled when evaporation takes place eg sweating leads to heat loss
What is radiation?
The transfer of heat from one object to another without physical contact, heat leaves the body in the form of electromagnetic radiation
What are the ways the body can maintain heat?
- Vasoconstriction (Increases blood pressure) - decreases the heat transfer from internal organs to skin
- Stimulation of adrenal medulla - secrete adrenaline and noradrenaline to increase metabolic rate and heat production
- Shivering - under control of hypothalamus
- Increase in thyroxine - causes AN love to secede TSH which causes the thyroid to release thyroxine and thus increase metabolic rate increasing heat
- Behavioural response - putting on a jumper or curling up in a ball
How does the body prevent body temperature from rising?
- Vasodilation - Increases blood flow through the skin, heat is lost through radiation and convection
- Sweating - needed to increase heat loss from the body, has a cooling affect
- Decrease in metabolic rate - reduction in the secretion of thyroxine to reduce heat production
- Behavioural response - turning on air conditioner, removing clothing
What does temperature tolerance refer to?
Extreme changes in body temperate:
- Hypothermia - extreme cold conditions
- Hyperthermia - extreme heat conditions, death can occur when body temperature reaches 44-46 degrees
