4.4 Regulation of body temperature in animals Flashcards
What is core body temperature?
Core body temperature relates to the temperature in organs and deep tissues within the core of the body. around 37 for humans.
What physiological mechanisms that lead to the production or loss of heat?
What is the job of receptors , the control centre and effecters in the change of temperature?
Receptors sense (detect) changes in the external and internal temperatures: These receptors are located in the skin, liver, skeletal muscles and hypothalamus.
The control centre identifies the response to change: groups of nerve cells in the hypothalamus can receive either ‘warm’ or ‘cold’ signals from the thermoreceptors, compare them with the desired set point, identify the response needed and signal this to effectors.
Effectors respond to change: blood vessels in skin, , skeletal muscles and sweat glands defend against heat or cold through automatic (involuntary) response
What is vasoconstriction and what is the purpose of it and what triggers it to happen ?
Vasoconstriction is narrowing of the diameter of blood vessels, and it results in less heat loss across the skin and more heat retained within the body. It is caused by a decrease in temperature in the external environment.
What is ilorection and what is its purpose?
Iloerection, also known as “goosebumps”. A tiny bundle of smooth muscle fibres is attached near the base of each hair follicle. When the hypothalamus receives input from cold sensors, it sends impulses to these muscles, causing them to contract and raise the hair or fur.
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.
How does shivering heat up the body?
Shivering requires energy. To power their shivering, muscles release energy from their cellular store, and heat energy is released in this process. Shivering increases the body’s metabolic rate and raises the associated heat production to about five times that of the resting rate (basal metabolic rate). Thus, shivering produces significant amounts of additional heat for the body.
Why is shivering not sustainable for long periods of time?
because of its high rate of energy use, shivering cannot be sustained for long periods because the energy stores of muscle tissue become depleted — they run out of fuel!
What is hyperthermia?
Hyperthermia condition in which core body temperature exceeds the upper end of the normal range without any change in the temperature set point as set point is reset.
What steps happens when core temperature gets to high?
The stimulus is detected by heat receptors in the skin and various organs, and is signalled to the hypothalamus.
The hypothalamus signals a range of automatic ‘cooling down’ instructions for effectors.
The effectors are cutaneous blood vessels and sweat glands in the skin.
The responses by the effectors are an increase in blood flow in the skin blood vessels and the production of sweat by the sweat glands.
What is vasodilation and what is its purpose ?
When the core body temperature rises above the upper limit of the set point, the hypothalamus sends a nerve signal that inhibits vasoconstriction of (skin) blood vessels. Vasodilation is the widening of blood vessels to increase blood flow and increase heat loss across the skin as wider blood vessels mean a greater SA:V Ratio and thus more heat can be lost. It is the body’s he first response to a rise in body temperature above its normal range.
How does sweating increase heat loss?
Nerve impulses from the hypothalamus activate sweat glands.
Liquid sweat on the skin evaporates, forming a vapour.
When liquid water evaporates, energy is needed to change its state from liquid to gas. The evaporation of sweat requires heat energy, and this is taken from blood vessels close to the skin, thus cooling the body.
Using the stimulus–response model, clearly explain how homeostatic mechanisms act to return body temperature to normal.
Thermoreceptors throughout the body and within the hypothalamus detect that the body temperature is low. These receptors sends nerve signals to the hypothalamus. The hypothalamus sends nerve signals to activate various effectors. It signals blood vessels near the skin surface to constrict, reducing body heat loss; it signals skeletal muscles to shiver, producing metabolic heat through the release of thyroxine it increases the BMR . These various responses return the core body temperature to within the normal range. This forms a closed homeostatic loop with negative feedback
Briefly explain a key difference between fever resulting from a microbial infection and hyperthermia arising from prolonged strenuous physical activity in hot conditions.
A fever caused by a microbial infection causes the hypothalamus to raise the normal temperature set point to a higher value, such as 39 °C or 40 °C. In response to this reset, the heat-producing mechanisms, such as shivering, are initiated to raise the core body temperature to within the range of the new higher core body temperature set point .
Prolonged strenuous physical activity in hot conditions causes a rise in core body temperature to a value above the normal set point of the hypothalamus of about 37 °C. In response to this increase, the body initiates homeostatic mechanisms to cool the body, such as sweating and vasodilation of blood vessels .
A person with a low body temperature often has pale skin. Explain this observation.
A person with low body temperature will respond by reducing heat loss.Vasoconstriction of blood vessels near the surface of the skin will reduce the flow of blood to the skin and hence reduce heat loss. This will make the person pale.
