Name: malik Mohammed
Unit 9: Human regulation and Reproduction
Learning Aim B: Understand the homeostatic mechanisms used by the human body.
Homeostatic control of body systems
P2
In homeostasis, an organism can keep a constant internal environment (regulating hormones, body
temp., water balance, etc.). Homeostasis requires constant monitoring of internal conditions. From
body temperature to blood pressure to nutrient levels, everything has a set point. A set point is a
physiological value around which the normal range varies. A normal range is a set of values that are
healthy and stable. The average human body temperature is 37°C (98.6°F). Temperature and blood
pressure, for example, usually fluctuate within a few degrees of that threshold. The brain's control
centres help maintain normal physiological parameters. The body will resist any significant deviation
from homeostasis and restore it through a process known as a feedback loop.
A feedback loop consists of three parts. A sensor, known as a receptor, is part of a feedback system
that monitors a physiological value. It is responsible for detecting environmental changes. This value
is forwarded to the control centre. The control centre is part of a feedback system that compares the
value to the expected range. If the value differs too much from the set point, the control centre
activates an effector. The effector in a feedback system is the component that makes a change to
reverse the situation and return the value to its normal range. The effectors are muscles and glands.
The receptor identifies a change in the environment. The control or integration centre receives data
from the receptor. The effector reacts to the control centre's commands by opposing or enhancing
the stimulus. This continuous process restores and maintains homeostasis. Examples of temperature
receptors in the skin are blood vessels and sweat glands, which signal the brain (the control centre)
to regulate body temperature. Because the body's internal and external environments are
constantly changing, adjustments must be made to maintain a set point.
Positive feedback increases the magnitude of a change in the body's physiological state rather than
decreasing it. Increased change occurs due to a deviation from the normal range, which causes the
system to drift further away from the normal range. Positive feedback is typical in the body only
when there is a clear endpoint to the observed process. Standard positive feedback loops, such as
those that occur during childbirth and the body's response to blood loss, are only activated when
they are necessary.
, Negative feedback refers to a system in which the reaction to a stimulus has the effect of turning off
or decreasing the strength of the initial stimulus. The most common mechanism through which the
body maintains homeostasis is through negative feedback loops. Negative feedback is constantly
employed to maintain homeostasis throughout the body, and hence a working knowledge of
negative feedback is required for a working knowledge of human physiology.
P2
The set-point of a system can be changed. When this occurs, the feedback loop kicks in to keep the
new setting in place. Blood pressure is an example of this: as blood pressure continues to rise, the
normal or set point for blood pressure can rise as well. The body no longer considers the elevation to
be abnormal and makes no attempt to return to the lower set point. As a result, elevated blood
pressure is maintained, which can be harmful to the body. Medication can help to reduce high blood
pressure and the system's set point to a healthier level. In a feedback loop, this is referred to as a
process of changing the set point.
Unit 9: Human regulation and Reproduction
Learning Aim B: Understand the homeostatic mechanisms used by the human body.
Homeostatic control of body systems
P2
In homeostasis, an organism can keep a constant internal environment (regulating hormones, body
temp., water balance, etc.). Homeostasis requires constant monitoring of internal conditions. From
body temperature to blood pressure to nutrient levels, everything has a set point. A set point is a
physiological value around which the normal range varies. A normal range is a set of values that are
healthy and stable. The average human body temperature is 37°C (98.6°F). Temperature and blood
pressure, for example, usually fluctuate within a few degrees of that threshold. The brain's control
centres help maintain normal physiological parameters. The body will resist any significant deviation
from homeostasis and restore it through a process known as a feedback loop.
A feedback loop consists of three parts. A sensor, known as a receptor, is part of a feedback system
that monitors a physiological value. It is responsible for detecting environmental changes. This value
is forwarded to the control centre. The control centre is part of a feedback system that compares the
value to the expected range. If the value differs too much from the set point, the control centre
activates an effector. The effector in a feedback system is the component that makes a change to
reverse the situation and return the value to its normal range. The effectors are muscles and glands.
The receptor identifies a change in the environment. The control or integration centre receives data
from the receptor. The effector reacts to the control centre's commands by opposing or enhancing
the stimulus. This continuous process restores and maintains homeostasis. Examples of temperature
receptors in the skin are blood vessels and sweat glands, which signal the brain (the control centre)
to regulate body temperature. Because the body's internal and external environments are
constantly changing, adjustments must be made to maintain a set point.
Positive feedback increases the magnitude of a change in the body's physiological state rather than
decreasing it. Increased change occurs due to a deviation from the normal range, which causes the
system to drift further away from the normal range. Positive feedback is typical in the body only
when there is a clear endpoint to the observed process. Standard positive feedback loops, such as
those that occur during childbirth and the body's response to blood loss, are only activated when
they are necessary.
, Negative feedback refers to a system in which the reaction to a stimulus has the effect of turning off
or decreasing the strength of the initial stimulus. The most common mechanism through which the
body maintains homeostasis is through negative feedback loops. Negative feedback is constantly
employed to maintain homeostasis throughout the body, and hence a working knowledge of
negative feedback is required for a working knowledge of human physiology.
P2
The set-point of a system can be changed. When this occurs, the feedback loop kicks in to keep the
new setting in place. Blood pressure is an example of this: as blood pressure continues to rise, the
normal or set point for blood pressure can rise as well. The body no longer considers the elevation to
be abnormal and makes no attempt to return to the lower set point. As a result, elevated blood
pressure is maintained, which can be harmful to the body. Medication can help to reduce high blood
pressure and the system's set point to a healthier level. In a feedback loop, this is referred to as a
process of changing the set point.
