Thermoregulation

what is thermoregulation?

is the regulation of body temperature, making us relatively independent of the environmental temperature

what is the optimum temperature for core body temperature and why?

37 degrees is the set temperature for core body temp, this is the temperature where chemical reactions in cells are stable and optimised

what happens if body temperature is too high?

proteins will denature, serve cells do not function correctly, chemical reactions are uncontrolled, and death

What happens if body temperature is too low

cellular reactions are too slow, leads to death

what are some behavioural responses to temperature change

getting out of the sun and putting on a jumper

conscious and unconscious responses…

work together to keep the bodys core temperature within its tolerance limits

why is it important to have a constant temperate?

thermoregulation is an important aspect of homeostasis because chemical reaction occurring in cells are very heat sensitive.

How dos the body achieve the optimum temperature?

heat gained by the body must be equal to the heat lost from the body

what is the temperature of the body that remains constant?

36.8 degrees

under most conditions, the internal body temperature is… than the surrounding environment temperature ?

higher

How does the body maintain being at a higher temperature than the surroundings?

internal heat is produced from metabolic activity. (the breaking down of glucose to produce energy, and this is not 100 percent efficient and some energy is lost as heat also many metabolic reactions are exothermic)

what happens during exercise?

the increase in metabolic rate generates more heat than the body needs to keep its temperature constant. The increased heat needs to be removed or the body temperature will rise

what new some examples of heat input?

the heat from body processes (metabolism), especially respiration of liver and muscle cells and heat gained from surroundings by conduction and radiation

what are some examples of heat output?

radiation, conduction and convection to surroundings and evaporation of water from skin and lungs; warm air is breathed out and warm urine and faeces is excreted.

heat gain must be equal to…

heat loss

why can there be variations in body temperature?

this may result from activity to changes in external temperatures, it is usually the lowest temperature in the morning and the highest temperature in the evening. Also women have higher temperatures during the second half of the menstrual cycle as a result of the effects of progesterone.

how is heat produced in the body?

carbohydrates, proteins and lipids that we eat contain energy inn chemical bonds that hold various parts of the molecule together. this energy os released when food is oxidised during cellular respiration. Some of this energy is used for muscle contraction, active transport of substances moving across the cell membrane and building ups of new complex molecules. But most of this energy is released in the form of heat.

what is metabolic rate?

the rate at which energy is released by the breakdown of food.

what factors effect the metabolic rate?

exercise, stress and body temperature

what is the factor that will effect metabolic rate the greatest?

exercise, as during exercise muscular activity can increase metabolic rate up to 40 times, so very large amounts of heat is released.

why does metabolic rate increase bevcause of increased stress?

because the activities of the autonomic division of the nervous system. Stimulation of the sympathetic nerves releases noradrenaline from the nerve endings and noradrenaline increases the metabolic activity of cells. Strong sympathetic stimulation may cause dramatic increases in metabolic rate, but usually only for a few minutes.

for each 1 degree rise in body temperature, how much is biochemical reactions increased by

by 10 percent. therfore when a individual has a high fever, the metabolic rate may up to double the normal rate.

what are temperature receptors called?

thermoreceptors

what are peripheral thermoreceptors

thermoreceptors found in the skin and some mucus membranes

what is the function of peripheral thermoreceptors?

they detect changes in the external environment and sends this information to the hypothalamus.

what are central thermoreceptors?

thermoreceptors in the hyppothalamus

what is the function of central thermoreceptors?

these receptors detect the temperature of the internal environment

where are there additional thermoreceptors?

in the spinal cord, and the abdominal organs that provide the hypothalamus with information about the temperature of the internal environment.

what are the two types of thermoreceptors?

cold and heat receptors

what happens when cold receptors are stimulated?

the hypothalamus receives the information and initiates heat conservation and heat production mechanisms

what happens when heat receptors are stimulated?

mechanisms operate to reduce het production and increase heat loss.

how is the skin very important in regulating body temperature?

because of the large surface area of the skin, and its location between the internal and external environment

heat can be lost from the skin by…

convection, conduction, radiation and evaporation

what is conduction?

is the transfer if heat by direct contact between particles. i.e warm air or water in contact with the skin conducts heat onto the body

what are some examples of conduction?

warm air from the heater in a warm room, warm water in a bath, and warm air outside on a hot day, touching a hot stove.

what is convection?

is the transfer of heat by the movement of a liquid or gas which moves heat away from the body.

what are some examples of convection?

cold air outside or in a a cold room, cold wind moves heat very quickly away from skin, cold water in a bath or swimming pool, sweat evaporating off skin, taking heat away from the skin

what is radiation?

is the transfer of heat by inferred radiation being emitted by objects e.g like the sun or a heater

what is evaporation?

is the process of a liquid forming a gas, which absorbs heat energy

metabolic rate increases during exercise because…

during exercise muscles need energy to contract, cells respire more, more heat is produced, and body heat rises

what are the two modulators for thermoregulation?

the hypothalamus and the cerebral cortex

what does the hypothalamus do as a modulator?

it receives input from thermoreceptors in skin and also its own thermoreeptors. the hypothalamus will then send messages to effectors to regulate temperature

what does the cerebral cortex do as a modulator?

it receives input from thermoreceptors in the skin and hypothalamus, integrating conscious awareness of body temperature. it also coordinates effectors to regulate temperature.

what are the effectors in thermoregulation?

the skin, blood vessels, sweat glands, muscle activity , endocrine glands that effect metabolism and therefore heat gain from cellular respiration.

what are the blood vessels function as effectors

diameter of blood vessels can be controlled to increase or decrease exchange of heat between internal and external environments

blood vessels located where carry heat to the skin from the core of the body?

in the dermis

diameter of arterioles are controlled by what?

autonomic nerves. (sympathetic stimulation from the hypothalamus)

what is vasodilation?

is when the diameter of the arterioles in the dermis is increases so that more blood is transported to the capillaries in the skin and the rate of heat loss increases.

what is the function of vasodilation

blood vessels int eh skin dilate, therefore more blood can move through and allows heat to be lost to the environment

what is vasoconstriction?

is when the diameter of blood capillaries are reduced and less blood is transported thorugh the capillaries in the skin and the rate of heat loss decreases. And therefore less loss to cold environment via conduction, convection and radiation

when must sweating occur?

when heat must be lost and the skin blood vessels are already at maximum dilation

how is vasodilation triggered?

hypothalamus receives messengers from the thermoreceptors and initiates cooling response via the autonomic nervous system this allows heat to be los from the environment

what is sweating

is the active secretion of fluid by sweat glands and the periodic contraction of cells surrounding the ducts to pump sweat to the skins surface.

how does sweating occur?

the hypothalamus receives messages from thermoreceptors and initiates a cooling response via the autonomic nervous system. (production and transport of sweat is stimulated by sympathhetic nerves)

what is the only option for cooling above 37 degrees?

sweating

when is sweating needed?

for environmental temperatures above 28 degrees

how does sweating decrease temperatures

evaporation of sweat from the skin has a cooling effect, as heat is removed from the skin when liquid swear turns to vapour. the cooling of the skin results in cooling of blood flowing through the skin

what is sweat made out of?

is made out of water containing dissolved substances, primarily sodium chloride and small amounts of urea, lactic acid and potassium ions

in what kind of environment does seating work best in?

low humidity environments

how is sweating decreased?

by the autonomic stimulation from hypothalamus (which decreases sweat production and therfore decreases evaporative cooling)

other than sweating, what are some other forms of evaporative cooling?

there is a continual loss of water by evaporation from external body surfaces such as from the lungs and respiratory passages (this also causes heat loss)

muscle activity generates…

heat

shivering is due to…

an increase in skeletal muscle tone

how does shivering occur?

the hypothalamus sends messages to brain centres that controls muscle tone. shivering can influenced by the cerebral cortex up to a point (for example you are able to consciously stop shivering))

what is shivering?

is the rhythmic muscle tremors that occur at a rate of 10 to 20 per second. this requires cellular respiration and heat is produced as a by product to this cellular respiration.

what are the conscious behavioural responses when body temperature falls below a set point

our conscious awareness will result in behavioural changes to minimise heat loss such as seeking shelter form cold weather, putting on clothing to insulate against the heat loss, curling up tight to decrease surface area for heat loss and to move more to increase metabolic activity and therfore heat gain

what are the conscious and behavioural responses to heat gain

wearing fewer clothing layers, seeking cooler environments and reducing physical activity

what are the endocrine responses to temperature falling below a set point?

the hypothaamic sympathetic stimulation of adrenal medulla resposnse, so that adrenalin and noradrenalin is released. this will increase cellular metabolism and heat production. this will counteract heat loss. Also there will be an increase in thyroxine production; they hypothalamus will release thyrotropin releasing hormone which causes the anterior pituitary lobe to release thyroid stimulating hormone which will cause thyroxine to be released. thyroxine increases metabolic rate and therefore heat.

what are the endocrine responses wen body temperature rises above a set point?

the rise in body temperatures are detected by thermoreceptors, the hypothalamus receives a message and initiates a response, this will inhibit messages to the thyroid (via the anterior pituitary) to inhibit thyroxine production. less thyroxine means a lower metabolic rate, so less heat is produced. this tends to be a much longer term response (i.e seasonal)

how does the hypothalamus monitor the temperature of the core temperature?

it monitors the temperature of the blood and receives impulses from the peripheral thermoreceptors. through negative feedback loops involving the autonomic division pf the nervous system, it controls the diameter of skin arterioles, sweating, shivering and other mechanisms involving temperature

what is a dangerous body temperature?

a temperature over 42 degrees and death usually occurs after 45 degrees

what happens when the temperature and relative humidity are high?

it is difficult for the body to lose heat by evaporation or radiation.

what is heat stroke?

when the body is unable to manage temperature due to extreme external conditions, and core body temperature rises above the tolerance limits (body temps rise and regulatory mechanisms cease) this can be fatal is brain cells are affected.

what is the treatment for heat stroke?

cooling off the body can quickly as possible by immersing the patient in cold water (i.e careful cooling)

what is heat exhaustion?

is less severe than heat stoke, it is dehydration from sweating and vasodilation, (the loss of water fro sweating reduces the volume of blood plasma and vasodialation reduces the resistance to blood flow) thus there is a decrease in blood pressure and the output of the blood decreases therfore patient may faint. Core body temperature may not change it a drop in blood pressure because of the normal cooling responses

when does hypothermia occur?

when core temperature falls below 33 degrees, the metabolic rate is so slow that heat production is unable to replace the heat lost and the body temperature continues to fall. death can occur if it falls below 32 degrees.

what is the treatment for hypothermia?

careful slow warming

what is the treatment for heat exhaustion?

help patient feel cooler (cold compress, cold drink) and give fluids