A&P Capter 1

A group of organs arranged in such a way that they can together perform a more complex function than can any organ alone.

The study of the structure of an organism and the relationship of its parts.

The study of the functions of living organisms and their parts.

The smallest "living" units of structure and function in our body.

A state of relative constancy of the body's normal internal environment.

Our survival is dependent on the stability of the chemical composition of our body fluids.

Amplifies a change that is occurring (stimulatory).

Opposes or negates a change in a controlled condition (inhibitory).

• Each structure that makes up the human body has a level of complexity.
• Chemical
• Cell
• Tissue
• Organ
• Organ System
• Organism

The reference position for the body that gives meaning to directional terms.

serves as a reference position when dissecting the body into planes, regions, or cavities. It allows us to discuss the body and the relationship of portions to the whole in a universal manner.

• When in the anatomical position:
• The body is in an erect or standing posture.
• Face is forward.
• Arms are at the sides.
• Anatomical directions
• Click to enlarge
• Feet and palms of the hands are directed forward.
• Feet are slightly apart.

The directional terms used to describe the relative positions of body parts are:

• Superior (towards the head) and inferior (towards the feet)
• Anterior [Front, in front of (same as ventral in humans)] and posterior [Back, in back of (same as dorsal in humans)]
• Medial (Toward the midline of a structure) and lateral (Away from the midline or toward the side of a structure)
• Proximal (Toward or nearest the trunk, or nearest the point of origin of a structure ) and distal (Away from or farthest from the trunk, or farthest from a structure's point of origin)
• Superficial (Nearer the body surface ) and deep (Farther away from the body surface)

To further describe the spatial relationships of internal body parts, we utilize three main imaginary planes that dissect the body into different parts.

• A frontal plane divides the body into anterior (front) and posterior (back) positions.
• A sagittal plane divides the body into right and left sections.
• A transverse plane divides the body into superior (upper) and inferior (lower) sections.

Internal organs are neatly arranged in two main body cavities:

• Ventral (Of or near the belly; in humans, front or anterior)
• Thoracic cavity
• Pleural
• Mediastinum (Midportion of thoracic cavity)
• (Diaphragm)
• Abdominal
• Abdominopelvic
• Pelvic

• Dorsal (Referring to the back; in humans, back or posterior)
• Cranial cavity
• Spinal cavity

Within these two cavities are several subdivisions that contain organs and systems of similar or cooperative function.

To provide a means of identifying specific regions or areas of the body, anatomical descriptive terms are used that allow details to be described in an acceptable universal language.

• The two main body regions are:
• Appendicular — The bones of the upper and lower extremities and the bones of attachment.
• Axial — Refers to the head, neck, and torso or trunk of the body.

Temperal

Temporal (side of skull)

To assist in this process, a highly complex, integrated communication control system is necessary.

Is a complex integrated communication control network, classified as positive or negative.


Negative and positive feedback loops work independently to provide the inhibitory or stimulatory mechanisms required to maintain homeostasis.

The body's negative feedback loop compared to a house's thermostat

Negative feedback or negative feedback loops reverse a body response back to a normal state or homeostasis. They are stabilizing and inhibitory.

When the blood pressure decreases, body sensors detect the deviation and initiate changes that return the pressure within normal range. These changes are brought about as a result of negative feedback.

• Positive feedback or positive feedback loops promote change from a normal state and are not frequently used in a healthy body.
• If this change is a departure from homeostasis, it can lead to a continuous deterioration of homeostasis.
• There are some positive feedback loops that offer beneficial outcomes for the body.
• The contractions of the uterus during childbirth and the blood clotting process are two examples of positive feedback loops that provide assistance to the body without causing harm.

Positive feedback must be temporary and relatively rapid because it is stimulatory and the body cannot adapt to the constant instability of the changes and possible destruction of homeostasis.

• The scientific method is a systematic approach to discovery. Many scientists use the following methods to accurately draw conclusions about the world around them.
• A hypothesis is an idea or principle to be tested in experiments.
• An experiment is a test of that hypothesis. In a controlled experiment, outside elements are eliminated to produce a more trustworthy result.
• A theory or law is a hypothesis that has been proven by experiment to have a high degree of confidence.