Thermoregulation & Homeostasis
Thermoregulation is when the body can maintain its core internal temperature (37*). Enzyme
activity is heavily impacted by one's body temperature because different enzymes work best at
specific temperatures. The outer layer of skin is made of dead cells called epidermis, and it
contains sensory nerve endings. Under the epidermis is the dermis, and it contains living cells,
blood vessels, sweat glands, hair follicles and sensory receptors. Under the dermis is the
subcutaneous tissue that stores lipids. The skin is important throughout thermoregulation as it
protects sweat glands and capillaries (effectors) from pathogens and it acts as a receptor.
The human body temperature is controlled by the hypothalamus, located in the brain which can
control every endocrine gland responsible for adjusting blood pressure, body temperature,
metabolism and adrenaline levels. The Hypothalamus have special two sets of thermoreceptors
that are sensitive to the temperature of blood, which give out and receive information about
the surface temperature of the skin that monitor the skin temperature and environmental
temperatures. If the thermoreceptors in the hypothalamus detect a change in body
temperature away from the normal level, the hypothalamus brings about corrective
mechanisms to return the body temperature back to the normal level. This process works by
negative feedback.
Homeostasis is the state that the body is returned to after thermoregulation mechanisms,
thermoregulation is the process that keeps your body at its core internal temperature. In other
words, homeostasis is a variable that triggers counteracting responses to bring the body back to
normal with the help of negative and positive feedback, these are variables that change
depending on the issue. Homeostasis requires communication, this is done with four
components; The stimulus, this is a change in the environment, receptors indicate the value of
the variable(stimulus) that has moved away from the set point. The sensor, this monitors the
values of the variable and sends data to the brain (control system, coordinators, central
nervous system). The control center, this compares the values, if the values are different from
the set point, the nervous system sends a signal to the effector. The effector, this is an
organ/muscle/gland or any other component that acts on the signal from the control center to
the stimulus back towards the set point.
Negative feedback- This is used to achieve homeostasis, when a stimulus has been detected
from a set point, feedback serves to reduce an excessive response back to the set point and
keep a variable within the normal range and then it is switched off. For example, the variable is
temperature, then the body's thermoreceptors in the skin identify a change in temperature,
nerve impulses are sent as neurons to the thermoregulatory center in the hypothalamus,
undersurface of the brain. The body will then try, and counter react depending on the issue. If
the body temperature falls below 37* (stimulus) then nerve impulses will be sent to the skin
and muscle to cause a variety of things to counteract this, RESPONSES:
, Shivering, this is an involuntary response that occurs when the skeletal muscles contract and
relax rapidly. This increases the rate of respiration in muscles, so more heat is generated.
Piloerection, where erector muscles (effector) in hair follicles to contract causing hairs to stand
on end and trap warm air next to the skin. Or vasoconstriction: this narrowing of the arterioles
so the pattern of blood flow switches in the skin so less blood flows in the capillary beds near
the surface of the skin and more blood is retained deeper in the skin structure. This is achieved
by narrowing the arterioles that supply the capillary beds near the surface (arterioles and
arteries have plenty of muscle in their walls that can contract to narrow the lumen of the blood
vessel).
However, If the body temperature goes above 37* (stimulus) then nerve impulses (stimulus)
will be sent to the skin and muscle to cause a variety of things to counteract this, RESPONSES:
Vasodilation is when the arterioles (effectors) relax, so that more blood is flown towards the
capillary beds near the surface. The hypothalamus (coordinator) sends impulses along the
parasympathetic nerves to the skin arterioles, causing smooth muscle in the walls of these
arterioles to relax. The shunt vessel constricts (effector), forcing more blood to flow through
the surface capillaries, thus increasing the amount of heat energy lost by radiation. Sweating,
Sweat is produced by the sweat glands and travels up the sweat duct and out of the sweat pore
onto the skin surface. Here it will evaporate, taking excess body heat with it.
Positive feedback- This is where rather than the variable counteracting, the variable intensifies
the release of hormones and glands. One example is when in labor, the hormone oxytocin
stimulates more uterine contractions to help push the child out. Or blood clotting.
