Body Plan and Organization and Homeostasis

What is anatomical position?

Anatomical Position = Body upright, facing forward, arms at sides, palms forward, feet flat on ground, eyes open.

How do "right" and "left" apply in anatomical reference?

They refer to the patient's right and left, not the observer’s.

What are the three major body planes?

• Frontal (coronal) plane: Divides into anterior and posterior parts

• Sagittal plane: Divides into left and right parts (midsagittal = equal halves)

• Transverse plane: Divides into superior and inferior parts

Name the main body cavities and an organ found in each.

• Cranial cavity: Brain

• Vertebral cavity: Spinal cord

• Thoracic cavity: Heart and lungs

• Abdominopelvic cavity: Digestive, urinary, and reproductive organs

What are the four abdominopelvic quadrants?

• Right Upper Quadrant (RUQ)

• Right Lower Quadrant (RLQ)

• Left Upper Quadrant (LUQ)

• Left Lower Quadrant (LLQ)

Define the directional term "anterior."

Anterior (ventral) = Toward the front of the body.

Order the levels of organization from simplest to most complex.

Atom → Molecule → Cell → Tissue → Organ → Organ System → Organism

Define "anatomy" and "physiology."

• Anatomy: Study of body structure

• Physiology: Study of body function

What is homeostasis?

Homeostasis = The body's ability to maintain a stable internal environment despite external changes.

What are the components of a homeostatic control system?

• Stimulus: Produces a change

• Receptor (Sensor): Detects the change

• Control Center: Processes information and decides response

• Effector: Carries out response to restore balance

Define:

• Setpoint

• Variable (stimulus)

• Receptor

• Control center

• Effector

• Setpoint: Ideal value for a variable

• Variable (stimulus): Factor being regulated

• Receptor: Detects changes

• Control Center: Decides action

• Effector: Executes the response

What is the difference between equilibrium and steady-state?

• Equilibrium: No net movement; equal.

• Steady-state: Constant movement but stable condition; energy input required.

What is negative feedback?

Negative feedback = Response reduces or shuts off the original stimulus to maintain balance.
Example: Blood pressure regulation.

What is positive feedback?

Positive feedback = Response enhances or amplifies the original stimulus.
Example: Labor contractions with oxytocin release.

Why is negative feedback more common than positive feedback?

Because it stabilizes the body by opposing changes, maintaining homeostasis.

List some examples of negative feedback.

• Body temperature regulation

• Blood glucose control (insulin/glucagon)

• Blood pressure regulation

List examples of positive feedback.

• Labor contractions

• Blood clotting

In a homeostatic control system, what is the afferent vs efferent pathway?

• Afferent pathway: Carries information to the control center.

• Efferent pathway: Carries information away from control center to effector.

Describe how blood pressure homeostasis works when standing up.

• Standing → blood drains → BP drops → baroreceptors sense → brain accelerates heartbeat → BP rises → homeostasis restored.

What is a gradient in physiology?

Movement from high to low concentration, pressure, temperature, or electrical charge.