AS Anatomy and Physiology - Cardiovascular System

Question 1

Describe the Cardiac Conduction System

Answer 1

• Electrical impulse from sinoatrial node spreads through walls of atria, causing them to contract, forcing blood into the ventricles
• Impulse passes through atrioventricular node, AVN delays impulse for approx. 0.1s to enable atria to fully contract before ventricular systole begins
• Impulse passes through bundle of His
• Bundle of His branches out into bundle branches
• These move into smaller bundles called purkinje fibres, which spread through ventricles, causing them to contract

Question 2

Describe the Role of Chemoreceptors

Answer 2

• Found in carotid arteries and aortic arch
• They sense chemical changes
• During exercise, they detect increases in CO2
• Increased conc. of CO2 in blood will stimulate the sympathetic nervous system - heart will beat faster

Question 3

Describe the Role of Baroreceptors

Answer 3

• Contain nerve endings that respond to stretching in arterial wall caused by changes in blood pressure
• Blood pressure above or below set point, signal sent to medulla oblongata
• Increase in arterial pressure, increases stretch of baroreceptor sensors, heart rate decreases (vice-versa)
• Beginning exercise, set point increases as you don’t want heart rate to slow down - it would negatively affect performance, less O2 to working muscles

Question 4

Describe the Role of Proprioceptors

Answer 4

• Sensory nerve endings located in muscles, tendons and joints
• Provide information about movement and body position
• Start of exercise, detect an increase in muscular movement, impulse sent to medulla - sends impulse through SNS to SAN to increase heart rate