Introduction to Physiology

The Six Levels of Organization

• Chemical level– Atoms

• Cell Level

• Tissue Level– A tissue is a group of similar cells and the

materials surrounding them

• Organ Level– An organ is composed of 2+ tissue

types that perform the same functions

• Organ System Level– Organ system is a group of organs that

have a common function (11 major organ systems)

• Organism Level

Homeostasis

• Existence and maintenance of a constant internal environment

• Mechanisms keep body temperature near an ideal normal range called set points.

– The points need to remain in a normal range.

Negative Feedback• Negative means that any deviation from

the set point is made smaller or resisted

• Regulates most body systems

• There are three components– Receptor– Control center– Effector

Receptor

• Monitors the value of some variables

• Detects changes and sends message to the brain

• Example: Blood pressure

Control Center

• Establishes the set points around which the variable is maintained

• Receives messages and tells body how to react

Effector

• Can change the value of the variable

• Example: Sweat, raise/lower blood pressure

Positive Feedback• Rare

• Creates a deviation further from the normal set point

• Example: Natural birth

Body Positions• Anatomical position

– Face directed forward– Upper limbs hanging to the side, palms

facing forward

• Supine– A person lying face upwards

• Prone– A person lying face downwards

Directional terms of the trunk• Superior = Cephalic

– Up, towards the head

• Inferior = Caudal

– Down, towards the “tail”

• Posterior =Dorsal

– Back side

• Anterior = Ventral– Front, belly side

Directional terms of the trunk

• Medial– Towards the midline

• Lateral– Away from the midline

Directional terms of the limbs

• Proximal

– Nearest the point of attachment

• Distal

– Furthest from the point of attachment

Planes• Sagittal

– Separates a body into a left and right

– Midsagittal/Median• Separates body into equal left and right

halves

– Parasagittal• Unequally divides left and right sides

• Transverse = Horizontal

– Horizontally divides body into superior and inferior portions (top and bottom)

• Frontal = Coronal

– Vertically divides body into anterior and posterior portions (front and back)

– Face remains intact

Body Cavities• The trunk contains 3 large cavities:

– Thoracic

• Surrounded by rib cage

• Partition called the mediastinum separates left and right parts

• Mediastinum contains the heart, thymus, trachea, esophagus

• Abdominal cavity

– Contains most of the digestive tract

• Pelvic cavity

– Located within the pelvic bones

• The pelvic and abdominal cavities are not physically separated and are sometimes called the abdominopelvic cavity

Serous Membranes

• Membrane that lines trunk cavities and organs

• Serous membranes are made of 2 layers:–Visceral serous is in contact with

internal organs–Parietal serous lines the walls of the

cavity

• The thoracic cavity contains 3 serous membrane – lined cavities:

–1 Pericardial cavity

–2 Pleural cavities

The Pericardial Cavity

• Surrounds the heart

• The visceral pericardium touches and covers the surface of the heart, which is contained within the parietal pericardium.

The Pleural Cavities

• Surrounds each lung

• Each lung is covered by visceral pleura, which is contained within a parietal pleura.

The Peritoneal Cavity

• Covers the abdominopelvic cavity

• Each organ is covered by a visceral peritoneum, which is located within the parietal peritoneum.