Anatomy and Physiology: Homeostasis and Body Systems
What this domain tests
Anatomy and Physiology tests the structure and function of body systems and how they maintain homeostasis. Expect questions on anatomical terminology, cell transport, skeletal and muscle function, circulation, gas exchange, kidney function, nerve signalling and endocrine control.
Core rules
- Anatomical position: standing erect, face forward, palms forward, feet together. Proximal is nearer the trunk; distal is farther away.
- Homeostasis is maintained mainly by negative feedback: a change is detected, a response reverses it. Example: rising blood glucose triggers insulin, lowering glucose.
- Cardiac output (CO) = heart rate (HR) × stroke volume (SV). Normal resting CO is about 5 L/min.
- Pulmonary artery carries deoxygenated blood to the lungs; pulmonary veins carry oxygenated blood to the left atrium. This is the opposite of systemic vessels.
- The left ventricular wall is thickest because it pumps against systemic resistance.
- Parasympathetic vagal stimulation slows the heart; sympathetic stimulation increases rate and contractility.
Worked example
A person has HR 75/min and SV 70 mL. Calculate CO. Reasoning: CO = 75 × 70 = 5,250 mL/min, or 5.25 L/min. This is within the normal adult resting range. If HR rose to 150/min with the same SV, CO would double to 10.5 L/min; if SV fell to 40 mL at HR 75, CO would fall to 3 L/min, which could reduce tissue perfusion.
Traps
- Mixing afferent (towards the CNS) with efferent (away from the CNS).
- Saying the pulmonary artery carries oxygenated blood.
- Treating all feedback as positive; most homeostasis is negative feedback.
- Forgetting that the SA node is the normal pacemaker.