18. Temperature Control Flashcards
What is the advantage of being homeothermic?
Can live in cold climates as are unaffected to changes in ambient temperature
What are the disadvantages to being homeothermic?
Expends energy
Complex regulation
What is the optimal internal temperature range?
35.5-37.7
What is the name for an animal that can’t control its own body temperature?
Poikilothermic
What is the effect of temperatures between 40 to 44?
Heat stroke
Brain lesions
What causes body temperatures between 38 to 40?
Fever
Exercise
What happens at temperatures between 34 to 36?
Mild hypothermia
What happens at temperatures between 30 to 34?
Impairment of temperature regulation
What happens at temperatures between 27 to 29?
Cardiac fibrillation
Where can temperature be taken from?
Mouth
Axilla
Rectum (.56 higher)
Ear
Where do homeothermic animals get heat from?
Metabolic oxidation of food
Exercising muscle
What is the function of the core?
Heat generation
Remains constant at 37.8 degrees
What is included in the core?
Internal organs
CNS
Skeletal muscle
What is the function of the shell?
Insulation
Exchange of heat depending on ambient temperature
What is involved in the shell?
Skin
Subcutaneous fat
What is the temperature range of the skin?
20-40
What are the 4 methods of heat transfer?
Radiation
Conduction
Convection
Evaporation
What form is heat emitted as?
Electromagnetic waves via radiation
What is conduction?
Transfer of heat between two objects of different temperatures in direct contact
What is the function of convection in heat loss?
Carries heat away from the body
Why does sweating help cool us down?
Heat is lost when water evaporates
How is temperature controlled through the vasomotor response?
Changing the width of blood vessels regulates the flow of blood in skin
What is the thermoneutral zone?
Temperature range at which core temperature is maintained constant by vasomotor responses alone
Why does humidity prevent heat loss?
Increased water concentration in the air prevents sweat evaporating
Heat cannot be lost through evaporation
What neurotransmitter is used in sweat glands?
ACh
What is the primary method of involuntary heat production?
Shivering
What is shivering?
Rhythmic skeletal muscle contraction and increased tone
All energy produced is used as heat as no work is done
How much can shivering increase internal temperature?
2-5 times
How does piloerection promote heat retention?
Heat is trapped amongst hair
What does lesion of the anterior hypothalamus result in?
Chronic hyperthermia (loss of heat loss reflexes)
Lesion of what part of the brain would cause chronic hypothermia? (due to loss of heat production and conservation)
Posterior hypothalamus
What is the function of peripheral thermoreceptors?
Monitor skin temperature
Where can core thermoreceptors be found?
Hypothalamus
CNS
Internal abdominal organs
What variations of body temperature is due to diurnal rhythm?
Lowest between 6-7am
Highest between 5-7pm
How much can exercise increase body temperature by?
2.3
What variations of body temperature is due to the menstrual cycle?
Increase of .5 in 2nd half of cycle
What are the secondary causes of hypothermia?
Hypothyroidism Hypopituitarism Malnutrition Stroke Trauma Drugs Burns Surgery
What are the symptoms of hypothermia?
Metabolic processes slow down
Higher cerebral functions affected
Decreased breathing rate
Decreased Cardiac Output
What are the pathological causes of hyperthermia?
High TH or adrenaline
Malfunction of hypothalamus
What is fever triggered by?
Pyrogens: interleukin-1B, TNFa
What releases pyrogens?
Macrophages in response to bacteria or viruses
What to pyrogens increase the production of?
Prostaglandins
What do prostaglandins induce?
Shivering and vasoconstriction
How to paracetemol and aspirin stop fever?
Block pyrogen pathway
