NREMT EMT 6: Anatomy, Physiology, and Pathophysiology - Cardiovascular System, Heart Anatomy, Cardiac Cycle, Blood Flow, Systemic/Pulmonary Circulation, Electrical Conduction

What This Is: Understanding the Cardiovascular System

The cardiovascular system is like a network of roads and highways that transport life-giving oxygen and nutrients to all parts of the body. When this system fails, it can lead to serious emergencies like heart attacks or strokes. Imagine a car engine running out of fuel – without a steady supply of oxygen and nutrients, the body's "engine" can shut down.

Key Steps / Core Facts:

• Heart Anatomy: The heart is a muscular pump that's about the size of a fist. It's divided into four chambers: the left and right atria (upper chambers) and the left and right ventricles (lower chambers). (Think of it like a four-room house with two upper rooms and two lower rooms.)
• Cardiac Cycle: The heart beats about 100,000 times per day, pumping blood through the body. It's like a never-ending cycle of inhale-exhale, inhale-exhale.
• Blood Flow: Blood flows through the heart in one direction, from the top chambers (atria) to the bottom chambers (ventricles). It's like water flowing through a pipe from the top to the bottom.
• Systemic Circulation: The heart pumps blood to the rest of the body through the arteries, which branch off into smaller and smaller vessels. It's like a tree with branches and leaves.
• Pulmonary Circulation: The heart also pumps blood to the lungs to pick up oxygen and drop off carbon dioxide. It's like a two-way traffic flow between the heart and lungs.
• Electrical Conduction: The heart has its own electrical system that tells it when to beat. It's like a pacemaker that keeps the heart ticking.
• Cardiac Output: The heart pumps about 2,000 gallons of blood per day. That's like filling a swimming pool every day!
• Blood Pressure: Blood pressure is the force of blood pushing against the walls of the arteries. Normal blood pressure is around 120/80 mmHg. (Think of it like the pressure of water in a hose.)
• Heart Rate: A normal heart rate is around 60-100 beats per minute. (Think of it like a metronome ticking away.)
• Cardiac Arrest: Cardiac arrest occurs when the heart suddenly stops beating. It's like a car engine stalling in the middle of the road.
• CPR Compression Depth: At least 2 inches – like pushing down a soda can. (AVPU: Alert, Verbal, Pain, Unresponsive)
• CPR Ratio: 30:2 – 30 chest compressions followed by 2 breaths. (OPQRSTI: Onset, Provocation, Quality, Region, Severity, Time, Insurance)
• Blood Pressure Ratio: 120/80 mmHg – the top number (systolic) is the pressure when the heart beats, and the bottom number (diastolic) is the pressure when the heart rests.

What Laypeople Can Do:

• If someone collapses, first check for danger (oncoming traffic, fire). Then shout and tap their shoulder.
• If someone is having a heart attack, call 911 and try to keep them calm.
• If someone is experiencing cardiac arrest, start CPR (30:2 ratio) and use an automated external defibrillator (AED) if available.

Common Mistakes:

• Mistake: Not checking for danger before approaching a collapsed person.
• Fix: Always check for danger first – it's better to be safe than sorry.
• Mistake: Not calling 911 in a medical emergency.
• Fix: Call 911 immediately if someone is experiencing a heart attack or cardiac arrest.
• Mistake: Not using an AED in cardiac arrest.
• Fix: Use an AED if available – it can help save a life.

Quick Practice Scenarios:

• A 55-year-old man collapses in the middle of the street. What should you do first?
• Answer: Check for danger (oncoming traffic, fire) and shout and tap his shoulder.
• A 75-year-old woman is experiencing chest pain and shortness of breath. What should you do first?
• Answer: Call 911 and try to keep her calm.
• A 30-year-old man is in cardiac arrest. What should you do first?
• Answer: Start CPR (30:2 ratio) and use an AED if available.

Last-Minute Exam Cram:

• Normal heart rate: 60-100 beats per minute.
• Normal blood pressure: 120/80 mmHg.
• Cardiac output: 2,000 gallons per day.
• CPR ratio: 30:2.
• Blood pressure ratio: 120/80 mmHg.
• Agonal breathing is NOT normal breathing – start CPR.
• Cardiac arrest is a medical emergency – call 911.
• Always use an AED in cardiac arrest.
• Never delay calling 911 in a medical emergency.
• Always check for danger before approaching a collapsed person.