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Module 1: The Human Body

1.3 Properties of Living Things

Properties of Living Things

These are the concepts we will be discussing throughout this semester in this course. The properties of living things include:

Necessary life functions

In your second semester A & P course we will build on the concepts from this course and begin to discuss many of the necessary life functions. These include the following:

Homeostasis

An extremely important concept that will be discussed throughout both semesters this year is homeostasis. Homeostasis is the maintenance of a stable internal environment. you will often here it referred to as a dynamic state of equilibrium that is necessary for normal body functioning. Homeostasis is necessary to sustain life.

When homeostasis is lost we are in homeostatic imbalance. This is simply a disturbance in homeostasis that ends up most often resulting in disease.

So How do we maintain homeostasis?

The body is a miraculous thing! There are an endless number of ways our body’s work to ensure we function at an optimal level every day.

Homeostasis is maintained by feedback systems. Feedback systems have a few key elements that we first need to understand.

Homeostasis Diagram

Let‘s take a look at these different components. First the Receptor. The receptor is responsible for responding to changes in the environment. We refer to these environmental changes as stimuli. The receptor responds by sending the information to the control center along what we call the afferent pathway. The control center is responsible for determining a set point. It analyzes the information and determines an appropriate response. This response to the stimulus is sent along an efferent pathway to the effector. The effector response by reducing the effect of the stimulus and helping return the system to homeostasis.

Matching Activity

Match the following terms to the correct definition:

Response
Input
Stimulus
Receptor
Output
Produces change in variable.
Detects Change.
Information is sent along afferent pathway to control center.
Information is sent along efferent pathway effector.
Of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level.

The body has several different types of receptors that are continually monitoring the environment to ensure it remains stable. Here is a list of some of the body's receptor types and what they are responsible for detecting:

Now that we understand the key elements of a feedback system, we can look at two types of feedback systems found in the human body.

The first is negative feedback. This type of feedback system is responsible for most of the homeostatic control mechanisms of the human body. It works like a household thermostat. It shuts off the original stimulus or reduces its intensity to bring the body back to homeostasis. There are many examples of this in the human body. One example is blood sugar regulation. When blood glucose levels are high, insulin is released and causes the blood glucose levels to decrease. When blood glucose levels are too low, glucagon is released and causes the blood glucose to increase.

The second type of feedback system is positive feedback. In this type, the original stimulus increases to push the variable farther. The reaction ends up occurring at a faster rate. In our bodies a couple examples of positive feedback are blood clotting and childbirth.

Matching Activity

Match the following receptors with the corresponding detection:

Chemoreceptors
Osmoreceptors
Tactile
Baroreceptors
Mechanoreceptors
Proprioreceptors
Nociceptors
Pain
Changes in Osmolarity
Body Position
Chemical Concentrations
Stretching
Blood Pressure
Touch, Pressure, & Vibration