Monitoring the Circulatory System

Control of the Heartbeat Cardiac muscle has the capacity to cause its own contractions. The nervous system controls the rate of heart beat Nerves first make contact with a small mass of tissue in the right atrium called the sinoatrial (SA) node aka pacemaker This is where the contraction of the heart originates

The SA node, located in the wall of the right atrium stimulates the surrounding muscle fibers to contract and relax rhythmically. The SA node generates an electrical impulse that quickly spreads over the two atria, causing them to contract simultaneously.

As the atria contract, the electrical impulse reaches another specialized node called the atrioventrical node (or A-V node ) The A-V node is located near the atria in the partition between the right and left ventricles (in the septum). The A-V node transmits an electrical pulse by a bundle of fibres called the bundle of His which then divide into Purkinje fibres (specialized muscle fibres) that surrounds the walls of the ventricles, causing them to contract. Wilhelm His Jr. (1863-1934)--the man behind the bundle. Wilhelm His Jr. (1863-1934) was a Swiss-born cardiologist and anatomist. In 1893, he discovered thebundle of His-the specialized tissue in the heart that transmits the electrical impulses and helps synchronize contraction.

NOTE: when relaxed, your S-A node fires regularly at about 70 times per minute. However, it can adjust to meet your body’s needs.

https://www.youtube.com/watch?v=IR0nWe47eek Play Until 1:20

Electrocardiogram (ECG) An electronic device that records the changing electrical currents produced as the S-A and A-V nodes fire impulses. The device produces a print out that can be used to diagnose any heartbeat irregularities.

P Wave: SA node fires and the atria contract

-Ventricles fill with blood QRS Complex: -Ventricles fill with blood -Atrioventricular valves close AV node stimulate the ventricles to contract

T Wave: -Ventricles relax -Semilunar valves close

https://www.youtube.com/watch?v=KWrzdJY4G9Q Entire video 2) Myocardial infarction (aka heart attack) https://www.youtube.com/watch?v=mLmKq5bQOg0&feature=iv&src_vid=tPqs4xKPG3A&annotation_id=annotation_1086275415

Blood Pressure The highest pressure in the cardiac cycle is the contraction of the ventricles or systolic pressure The lowest pressure is just before the ventricles contract or diastolic pressure blood pressure is measured in mm Hg and “normal adult” blood pressure is “120 over 80” 120mm Hg = systolic 80mm Hg diastolic

Two common disorders: Hypertension = high blood pressure Low blood pressure HW: Find out what causes each of the disorders Find out what their blood pressure readings are like Read pages 489 -491 Pg. 491 # 13-17 Pg. 493 # 2,6,7,9,11,14 PLANT ISU CHECK POINT IS NEXT WEEK!

Hypertension and Hypotension

Hypertension & Hypotension High BP (hypertension): danger of bursting vessels Aneurism - bulging vessels Brain (stroke), heart (heart attack), kidney (renal failure)

Hypertension & Hypotension Low BP (hypotension): Shock  death: brain damage (lack of O2)

Risk Factors Diet High Salt or High glucose Draws water from tissues into blood and thus increases blood volume, leading to increased BP High Cholesterol Accelerates atherosclerosis, a thickening of artery walls, which results in reduction of elasticity and vessel diameter, leading to increased BP Stress The stress response (eg. “fight or flight”) releases adrenaline from the adrenal gland, thus increasing HR, leading to increased BP Stimulants Caffeine, nicotine, alcohol imitate the effects of adrenaline, increasing HR & BP

Measuring Blood Pressure