regulation of body temperature Flashcards
(25 cards)
what is core body temperature and peripheral surface temperatures
- core body temperature; the temperature in organs and deep tissues within the core of the body.
- perpheral surface temperatures; can be manu degrees cooler.
- core temperature of humans is approximately 37 degrees, typical rage 36-39 degrees.
endotherms
- if an animal is able to regulate their internal body conditions we call them endotherms
- endothermic refers to mammals and birds whose internal temperature comes from metabolic processes:
endo = inside
thermo = heat
ectotherms
- if an animal’s internal envirnoment is dependant on the external envirnoment conditions, we call them ectotherms
- ectothermic refers to snakes, lizards, fish
what is thermoregulation
the regulation of body temperature
* it ensures heat gain and heat loss are in balance
* results in response to either increase or decrease the core body temperature
* many responses are physiological
* the thermoregulatory center in the hypothalamus monitors and controls temperature.
(enzymes involved in metabolism must have the correct temperature to catalyse reactions)
general stimulus-response model of thermoregulation
- stimulus, change in internal body and/or envirnomental temperature
- receptor, thermoreceptors
- modulator, hypothalamus
- effector, variety of cells and tissues
- response, change that alters heat transfer in body
hypothalamus, heat production and heat conservation centre
- vasoconstriction
- rise in metabolic rate
- shivering
- hair raised
effectors and responses
- effector, sweat glands; responses in cold - sweating inhibited, responses in heat - sweating occurs.
- effector, skeletal muscles of limbs and trunk: response in cold - shivering occurs, reponses in heat - shivering inhibited
- effector, brown adipose tissue (BAT): response in cold - heat produced BAT metabolism activated, response in heat - BAT metabolism inhibited
what are the 4 main methods of heat transfer
- conduction - the transfer of heat through physical contact with another object
- convection - the transfer of heat via the movement of a liquid or a gas between areas of a different temperature
- evaportaion - the loss of heat via the conversion of water from liquid to gas form
- radiation - the transfer of heat via eletromagnetic waves such as light (i.e. doesn’t require physical contact with another object)
decreased body temperature, the stimulus-response model when body temperature decreases
- stimulus, decrease in body temperature below normal
- receptor, decrease detected by thermoreceptors in skin, organs and hypothalamus of brain
- modulator or control centre, hypothalamus sends signals via nerve and hormonal systems to effectors
- effectors, -blood vessels in skin, - skeletal muscles, - brown adipose tissue (BAT)
-
responses, -reduced blood flow in skin vessels, - shivering, - BAT heat production, - increased metabolic heat from BAT.
(negative feedback)
when body tempurature is too low
hypothermia
* core body temperature falls below 35 degrees
* prolonged severe hypothermia with further falls in core tempurature can result in death.
several forms of hypothermia
- Acute hypothermia- sudden exposure to extreme cold, such as immersion in cold water.
e.g. Passengers on the Titanic, water temperature on that morning is thought to have been just above −2 °C. Those passengers who were immersed in the ocean died quickly from hypothermia.
- Exhaustion hypothermia- exposure to a cold environment, individual exhausted and no have sufficient food.
Metabolic heat cannot be generated to compensate for loss of heat so core body temperature falls.
e.g. Antarctic explorers and mountaineers climbing for days at high altitude on Earth’s highest mountains are at risk of exhaustion hypothermia.
what is vasoconstriction
- constriction of cutaneous blood vessels to limit blood flow to the skin, resulting in less heat loss across the skin and more heat retained within the body.
- it is a heat-conserving mechanisms
what is piloerection(heat-conserving mechanisms)
- Piloerection means ‘hair standing on end’.
- It occurs in many mammals.
- In humans it is easily seen as ‘goosebumps’ around each hair follicle
- Raised hairs create a layer of still air between the skin and the external environment that acts as an insulator and reduces heat loss from the body.
what is shivering (heat-conserving mechanisms)
- Occurs when exposed for an extended period to cold air or water without suitable protection from cold.
- An involuntary action
- The hypothalamus contains a centre that controls the shivering reflex.
- Alternate contraction and relaxation in rapid succession of many small skeletal muscle groups (in upper limbs and body trunk)
- Usually starts when the core temperature has fallen to 35oC.
what is adipose tissue (heat-conserving mechanisms)
- All mammals have two types of adipose (fat) tissue:
1. white fat cells that serve as energy stores
2. brown adipose cells (BAT) - BAT cells break down fatty acids, rapidly releasing almost 100 per cent of the energy directly as heat,with no production of ATP.
- Heat production by BAT cells can be sustained in the longer term.
- Important when the core body temperature can no longer be regulated by vasoconstriction and shivering can no longer continue.
behaivours for gaining and conserving heat
- vigorously exercising
- putting on another layer of clothing
- soaking in a hot bath
- having a hot drink
- rubbing your hands together
- reducing exposed body surface area
- wearing a hat and gloves
- standing in front of a heater
increased body temperature, stimulus response model
- stimulus, increase in body tempurature above normal
- receptor, increase detected by thermoreceptors in skin, organs and hypothalamus
- modulator or control centre, hypothalamus sends signals via nerves to effectors
- effectors, blood vessels in skin, - sweat glands
-
response, vasodilation of skin vessels, - intiatation of sweating, - inhibition of BAT metabolism
(negative feedback)
when body temperature is too high
hyperthermia
* core temperature rises to 38 degrees or higher
* two different types:
- non-fever hyperthermia; caused by external factors, set point for core body temperature stays within 36.5 to 37.5 degrees. this type can result in heat stroe
- fever hyperthermia; set point for core body temperature reset to a higher value, 38 degrees to gretaer than 40 degrees. produces fever, severity depends on the reset level.
syptoms of heat exhaustion and stroke
heat exhaustion
* headaches, nausea and vomiting
* excessive, sweating
* fatigue and exhaustion
* poor coordination
* slow pulse
* thirst
* increase in body temperature
heat stroke
* headaches, nausea and vomiting
* minimal sweat
* possible seizures or coma
* dizziness and delirium, with slurred speech
* fast pulse
* excessive thirst
* skin may fell cool compared to internal body temperature.
heat loss mechanisms: vasodilation
- the first response to a rise in body temperature above it’s normal range
- in heat stress, the blood flow through the skin capillaries can reach up to 8 litres per minute!
heat loss mechanisms: sweating
- Liquid sweat on the skin evaporates, forming a vapour.
- When liquid water evaporates, energy is needed to change state (liquid to gas).
- Evaporation of sweat requires heat energy, taken from blood vessels close to the skin, cooling the body.
- This is known as evaporative cooling
behavioral changes, behaviours for losing heat
- removing a layer of clothing
- having a cold shower
- resting in the shade
- using an ice pack
- removing your hat and gloves
- sitting in front of a fan
- maximising the body surface area exposed to a cooling wind
- soaking your feet in cold water
human body responses to temperature
hot
* vasodilation
* sweating
* pilorelaxation (this means the hair flattens)
* stretching out
cold
* vasoconstriction
* shivering
* piloerection
* curling up
- Homeothermy
the ability of endothermic species to regulate their body core temperature within a narrow range despite significant variations in ambient temperature.
