Homeostasis
The internal environment of an organism refers to all the conditions inside the body.
For a cell, its immediate environment is the tissue tissue fluid that surrounds it.
Features of tissue fluid that influence cell activities are:
Temperature – low temperatures slow down metabolic reactions; at high
temperatures, proteins, including enzymes are denatured and cannot function
Water potential – if the water potential decreases, water may move out of
cells by osmosis, causing metabolic reactions in the cell to slow or stop; if the
water potential increases, water may enter the cell causing it to swell and
maybe burst
Concentration of glucose – glucose is the fuel for respiration, so lack of it
causes respiration to slow or stop, depriving the cell of an energy source; too
much glucose may cause water to move out of the cell by osmosis
Homeostatic control
Negative feedback: a process in which a change in some parameter, such as blood
glucose level, brings about processes, which move its level back towards normal
again
Most control mechanisms in living organisms use a negative feedback control loop to
maintain homeostatic balance. This involves a receptor and an effector (muscles and
glands). The receptor detects stimuli that are involved with the condition being
regulated. A stimulus is any change in a factor, such as a change in blood temperature
or the water content of the blood.
The body has receptors, which detect external stimuli and others that detect internal
stimuli. These receptors send information about the changes they detect through the
nervous system to a central control in the brain or spinal cord. This sensory
information is known as the input. The central control instructs an effector to carry
out and action, known as the output. Continuous monitoring of the factor by
receptors produces a steady stream of information to the control centre that makes
continuous adjustments to the output. This causes the factor to fluctuate about a set
point and is controlled by negative feedback.
There are two coordination systems in mammals, the nervous system and the
endocrine system:
In the nervous system, information in the form of electrical impulses is
transmitted along nerve cells (neurones)
The endocrine system uses chemical messengers called hormones that travel
in the blood, in a form of long distance cell signalling
The control of body temperature - thermoregulation
This involves both coordination systems. All mammals generate heat from
respiration (mostly by liver cells) and have ways to retain it within their bodies. As a
result, they do not depend on absorbing heat from their surroundings and can be
active at any time.
The internal environment of an organism refers to all the conditions inside the body.
For a cell, its immediate environment is the tissue tissue fluid that surrounds it.
Features of tissue fluid that influence cell activities are:
Temperature – low temperatures slow down metabolic reactions; at high
temperatures, proteins, including enzymes are denatured and cannot function
Water potential – if the water potential decreases, water may move out of
cells by osmosis, causing metabolic reactions in the cell to slow or stop; if the
water potential increases, water may enter the cell causing it to swell and
maybe burst
Concentration of glucose – glucose is the fuel for respiration, so lack of it
causes respiration to slow or stop, depriving the cell of an energy source; too
much glucose may cause water to move out of the cell by osmosis
Homeostatic control
Negative feedback: a process in which a change in some parameter, such as blood
glucose level, brings about processes, which move its level back towards normal
again
Most control mechanisms in living organisms use a negative feedback control loop to
maintain homeostatic balance. This involves a receptor and an effector (muscles and
glands). The receptor detects stimuli that are involved with the condition being
regulated. A stimulus is any change in a factor, such as a change in blood temperature
or the water content of the blood.
The body has receptors, which detect external stimuli and others that detect internal
stimuli. These receptors send information about the changes they detect through the
nervous system to a central control in the brain or spinal cord. This sensory
information is known as the input. The central control instructs an effector to carry
out and action, known as the output. Continuous monitoring of the factor by
receptors produces a steady stream of information to the control centre that makes
continuous adjustments to the output. This causes the factor to fluctuate about a set
point and is controlled by negative feedback.
There are two coordination systems in mammals, the nervous system and the
endocrine system:
In the nervous system, information in the form of electrical impulses is
transmitted along nerve cells (neurones)
The endocrine system uses chemical messengers called hormones that travel
in the blood, in a form of long distance cell signalling
The control of body temperature - thermoregulation
This involves both coordination systems. All mammals generate heat from
respiration (mostly by liver cells) and have ways to retain it within their bodies. As a
result, they do not depend on absorbing heat from their surroundings and can be
active at any time.
