Human Physiology Exam 2

Preload

The stretch of the ventricles before contraction; determined by venous return

Afterload

The resistance ventricles must overcome to eject blood

Effect of ↑ preload on stroke volume

Increases stroke volume

Effect of ↑ afterload on stroke volume

Decreases stroke volume

Which vessels have high compliance?

Veins

Which vessels have low compliance?

Arteries

Where is the greatest drop in BP?

Arterioles

Flow equation

Flow = Pressure difference ÷ Resistance

Location of baroreceptors

Carotid sinus and aortic arch

BP drop causes?

↓ Baroreceptor firing → ↑ Sympathetic → ↑ HR

BP increase causes?

↑ Baroreceptor firing → ↑ Parasympathetic → ↓ HR and vasodilation

S1 heart sound

Closure of AV valves

S2 heart sound

Closure of semilunar valves

Determinants of stroke volume

Preload

Cardiac output equation

CO = HR × SV

Normal CO

~5 L/min

P wave

Atrial depolarization

QRS complex

Ventricular depolarization

T wave

Ventricular repolarization

When AV valves open

When atrial pressure > ventricular pressure

When semilunar valves open

When ventricular pressure > arterial pressure

Highest pressure vessel

Aorta

Lowest pressure vessels

Veins / vena cava

Four processes of respiration

Pulmonary Ventilation, External Respiration, Gas Transport, and Internal Respiration

Gas exchange occurs in

Alveoli

What surrounds alveoli?

Pulmonary capillaries

Function of alveolar pores

Equalize air pressure

Tissue that allows lung recoil

Elastic fibers

Pleura definition

Double membrane around lungs

Function of pleural fluid

Lubrication

What keeps lungs expanded?

Transpulmonary pressure

Inspiration is active or passive?

Active

Main muscle of inspiration

Diaphragm

Pressure change during inspiration

Intrapulmonary pressure ↓ to –1 mmHg

Expiration active or passive at rest?

Passive

Why does air exit during expiration?

Lung recoil increases pressure

Tidal volume

500 mL

Residual volume

~1200 mL

Vital capacity

TV + IRV + ERV

FVC

Forced vital capacity

FEV1

Volume exhaled in first second

Minute ventilation equation

VE = TV × RR

Alveolar ventilation equation

VA = (TV − dead space) × RR

Physiologic dead space equation

Dead space = TV × (PaCO₂ − PeCO₂) / PaCO₂