VESSELS, PRESSURE & THE CARDIAC CYCLE
Blood pressure is measured using this instrument, and a normal reading is expressed as this ratio.
What is a sphygmomanometer? Normal reading is 120/80 mmHg (systolic over diastolic).
This cup-shaped structure surrounds the glomerulus and collects the filtrate at the start of nephron processing.
What is Bowman's capsule?
This structure in the brainstem controls heart rate, breathing rate, and blood pressure.
What is the medulla oblongata?
Explain the structural difference between an artery and a vein that allows each to perform its function.
Arteries have thick, muscular, elastic walls to withstand high pressure from ventricular contractions. Veins have thin walls and valves to prevent backflow, they carry blood at low pressure back to the heart, assisted by skeletal muscle contractions.
Name the three processes of urine formation in order, and state where in the nephron each primarily occurs.
Filtration: glomerulus/Bowman's capsule.
Reabsorption: PCT, loop of Henle, DCT, collecting duct.
Secretion: PCT and DCT (additional wastes moved from blood into filtrate).
Name the three processes required for urine production in the nephron.
What are filtration, reabsorption, and secretion?
During systole, the ventricles contract and blood is pushed out. Describe the pressure changes in the left ventricle and aorta during this phase and explain what keeps blood from flowing backward into the atrium.
Left ventricular pressure rises above aortic pressure, forcing blood through the aortic semilunar valve into the aorta. The bicuspid (mitral) valve snaps shut (causing the 'lub' sound), preventing backflow into the left atrium. Once ventricular pressure drops below aortic pressure, the aortic semilunar valve closes (causing the 'dub' sound).
Explain why glucose does NOT normally appear in urine, and under what condition it would. What does its presence indicate clinically?
The PCT reabsorbs all filtered glucose. These carriers become saturated when blood glucose exceeds the renal threshold . Above this level, excess glucose remains in the filtrate and is excreted as glycosuria. Clinically this indicates uncontrolled diabetes mellitus blood glucose is too high for the nephron to fully reabsorb.
A person sprints up a flight of stairs. Name four specific physiological changes that occur and identify which body system is primarily responsible for coordinating them.
Increased heart rate, increased breathing rate, dilation of bronchioles, blood redirected to skeletal muscles (away from digestive organs), increased sweat production, dilated pupils. The sympathetic nervous system (autonomic nervous system) coordinates these via the fight-or-flight response.
A patient has a blood pressure of 165/105 mmHg consistently. Explain what each number represents physiologically, identify this condition, and describe two mechanisms by which it causes long-term arterial damage.
165 = systolic pressure (during ventricular contraction); 105 = diastolic pressure (during ventricular relaxation). Condition = hypertension. Damage: (1) Chronic high pressure mechanically stresses and damages the lining of the arteries, making them prone to atherosclerotic plaque formation. (2) Arterial walls thicken and lose elasticity (arteriosclerosis), narrowing the lumen and further raising pressure which is a dangerous positive feedback cycle.
Explain the function of the loop of Henle in creating concentrated urine. Why is the descending limb permeable to water but not salt, while the ascending limb is the opposite?
The loop creates a concentration gradient in the medulla.
Descending limb: permeable to water but not Na+/Cl-. water leaves by osmosis into the salty medulla, concentrating the filtrate.
Ascending limb: impermeable to water but actively pumps Na+ and Cl- out raises medulla osmolarity without losing water. This gradient allows the collecting duct (under ADH control) to reabsorb water by osmosis, producing concentrated urine.
Explain why surface area is critical in BOTH the respiratory system and the excretory system. Name the specific structure in each system where surface area is maximized and explain how it is achieved structurally.
Respiratory: alveoli maximize surface area (~70 m²) through millions of tiny air sacs, each surrounded by capillaries: allows rapid diffusion of O₂ and CO₂.
Excretory: the proximal convoluted tubule (PCT) has increased surface area for efficient reabsorption of glucose, amino acids, and water. Both systems use high surface area to maximize the rate of exchange across thin membranes.
Capillaries have walls only one cell thick with no smooth muscle, yet they are the most important vessels for body function. Explain why this is true, what would happen if capillary walls were as thick as arterial walls.
Thin walls minimize diffusion distance for O₂, CO₂, nutrients, and waste, the entire point of circulation is exchange, which occurs only at capillaries. Thick walls would make diffusion impossible.
A patient has damage to the following: the SA node, the left kidney, and the medulla oblongata. For each injury, explain the immediate physiological consequence, the body's compensatory response (if any), and the long-term outcome without treatment.
SA node damage: heart loses its pacemaker → AV node takes over at a slower rate (~40-60 bpm) → reduced cardiac output, dizziness Without treatment (artificial pacemaker), chronic low output leads to heart failure.
Left kidney damage: right kidney compensates by increasing nephron filtration rate → nearly normal function short-term → over decades, right kidney may be overburdened → eventual renal insufficiency.
Medulla oblongata damage: loss of autonomic control of HR, breathing, and BP → life-threatening without ventilatory support → no natural compensation possible; brainstem damage is often fatal or requires intensive intervention.