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.