Homeostasis and thermoregulation Flashcards
what is homeostasis?
it is the ability to maintain a constant internal environment
how is homeostasis achieved?
through negative feedback
what is negative feedback?
a type of control in which the conditions being regulated are brought back to set value as soon as it is detected that they have deviated from it.
what are the components of the negative feedback control system?
there is an input - a change to the system (e.g. increase in body temp.), followed by a
receptor - measures the level of the variable, followed by
the control centre - level of operation is set here, and info from receptor received and compared with set value, and commands to effector dispatched from here, followed by
the effector - brings about a second change to system (in the opp. direction to the input), followed by
the feedback loop back to the receptor - the receptor establishes the change has been corrected, and causes the effector to be switched off, followed by
an output - condition is restored to set value (e.g. a decrease in body temp.)
what does the hypothalamus act as? what does it consist of?
the control centre. it consists of a ‘heat loss centre’ and a ‘heat gain centre’
how does the hypothalamus sense things? then what does it do?
external stimuli: it receives information via sensory nerves from temperature-sensitive receptors located in the skin
internal stimuli: neurones detect changes in the temperature of the blood flowing through the brain.
it then communicates with the rest of the body via the nervous system.
how does sweat glands react to warm/cold conditions?
when your body is too hot and needs to lose heat, the sweat glands secrete more sweat. more sweat will then evaporate from your skin, allowing the heat from your skin to be lost quicker to the surrounding air.
when your body is cold, the sweat glands produce less sweat, resulting in less evaporation of sweat which reduces heat loss through the latent heat of vaporisation.
how does hair erector muscles react to warm/cold conditions?
when your body is too hot, the hair erector muscles will relax, causing the hair to lay flat and less air is retained against the skin, resulting in increased heat loss by convection/radiation.
when the body is too cold, the hair erector muscles will contract, causing the hairs to be raised. Much still air is retained against the skin, causing a decreased heat loss through radiation/convection.
how does skin arterioles react to warm/cold conditions?
when the body is hot, vasolidation of skin arterioles occur. the skin arterioles dilate and the by-pass arteriole are constricted. more blood flows to the skin surface resulting in increased heat loss by radiation.
when the body is cold, vasoconstriction of skin arterioles occur. the skin arterioles are constricted and the by-pass arterioles are dilated. Less blood flows to the skin surface resulting in decreased heat loss through radiation.
what is thermoregulation?
thermoregulation in the skin detects the increase/decrease in body temperature above/below the set point. This results in signal impulses being transmitted via the nervous system to the hypothalamus, which coordinates the response of effectors.
