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Anatomy and Physiology

Unit 1

Body Organization and Homeostasis

6 topics · 24 practice questions · Free responseNot yet reviewed

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Notes

Levels of organization

  • The body is organized as chemical, cellular, tissue, organ, organ system and organism levels. Anatomy studies structure and physiology studies function, and the two are closely linked.
  • The necessary life functions are maintaining boundaries, movement, responsiveness, digestion, metabolism, excretion, reproduction and growth.

Anatomical language

  • Anatomical position is upright with palms facing forward. Key terms: superior/inferior, anterior/posterior, medial/lateral, proximal/distal, superficial/deep.
  • Sagittal planes make left and right parts, frontal (coronal) planes make front and back parts, and transverse planes make upper and lower parts.
  • The dorsal cavity holds the brain and spinal cord. The ventral cavity has a thoracic part (heart, lungs) and an abdominopelvic part (digestive organs, bladder, reproductive organs), separated by the diaphragm.

Homeostasis and feedback

  • Homeostasis keeps the internal environment stable. A control loop has a receptor, a control center and an effector.
  • Negative feedback reverses a change (temperature, glucose, blood pressure). Positive feedback amplifies a change and ends when the event finishes (labor, clotting).

Topics in this unit

Each topic has its own short notes and practice.

Practice

Which term describes a structure that is closer to the point of attachment of a limb to the trunk?
A surgeon makes a cut that divides the body into front and back portions. This cut is along a:
The brain is located in which body cavity?
A group of similar cells that work together to perform a function is called a(n):
When blood pressure rises, receptors in the arteries signal the brain, which causes the heart rate to slow and blood vessels to widen. The blood pressure then falls. This is:
In the blood pressure example, which part of the loop is the heart (slowing its rate)?

Free response

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Free-response question

A hiker on a mountain walk in cold wind notices that her skin is cool, she begins shivering, and her core body temperature stays close to 37 degrees C.

(a) Identify the receptor, control center and effector in this response.

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Receptors: temperature-sensitive nerve endings in the skin (and the brain). Control center: the hypothalamus in the brain. Effector: skeletal muscles that shiver.

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(b) State whether this is positive or negative feedback and explain why.

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It is negative feedback. Shivering produces heat, which reverses the drop in body temperature and returns it toward the set point.

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(c) Explain why homeostasis is described as a dynamic balance rather than a constant value.

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Body temperature is not fixed at exactly 37 degrees C. It rises and falls slightly around a set point, and the control system continually corrects changes to keep it within a normal range.

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