Biology 20 - Circulation Beat Still My Heart Heart Innervation, ECG, Sounds & Blood Pressure http://science.nhmccd.edu/biol/ap2int.htm HEART CENTER ONLINE: http://www.heartcenteronline.com/myheartdr/common/articles.cfm?ARTID=187

How the Heart holds a Beat! Basic Anatomy Draw & Label  Septum with Bundle of His (nerve tissue) Purkintje Fibers Apex Label the right and left side, also the SA & AV too

How the Heart holds a Beat… The heart has a pacemaker called the SINOATRIAL Node (SA –Node) SA is located in the upper right atrium Sends out a signal for atria to contract A 2nd node, ATRIOVENTRICULAR, (AV-Node) is triggered by the SA Node AV is located at the top of the septum

How the Heart holds a Beat… As atria contract blood moves ______? AV node sends a signal down the septum (via Bundle of His) to the apex Ventricles now contract from bottom-up The Bundle of His acts as a time delay between atrial & ventricular contraction

Heart Beat terms… Tachycardia – SA signals speed up Bradycardia – SA signals slow down Pacemaker – device to help set the rate

Nervous System Control of the Heart Beat. Heart rate can be altered by two nerves coming from the medulla oblongata of the brain to the SA node. i. Vagus nerve – more impulses slows heart rate. Part of the parasympathetic nervous system. ii. Sympathetic Nerve – more impulses increase heart rate. Part of the sympathetic nervous system.

Heart rate can also be increased by the release of epinephrine (adrenaline) by the adrenal gland into the blood.

Reading an ECG – electrocardiogram. 5 parts to read: P-wave: atria contract QRS-wave: ventricles contract P-Q: apex receives signal R-S: rapid contraction of heart & relaxation T-wave: rest period T

Cardiac Cycle! - see handout TOP HALF – DIASTOLE [Period of relaxation] – I.e. when heart is resting! DIASTOLE MEANS TO?

Cardiac Cycle! - see handout BOTTOM HALF – SYSTOLE [Period of contraction] SYSTOLE MEANS TO?

Heart Sounds – see handout The “lubb-dup” sound comes from the heart valves slapping to a close First Heart Sound: When ventricles contract Tri & Bicuspid valves slap  LUBB Sometimes called A-V valve flaps Second Heart Sound: When ventricles relax Semi-lunar valves slap  DUP

Heart Sounds… MURMUR - valves do not close properly Blood leaks backwards Causes: Inherited Disease (viral) Not flossing teeth

Blood Pressure – See Handout! How is blood under pressure? Any fluid confined in a vessel (hose or vein) exerts a push against the walls that contains it If the blood vessel narrows what happens to the pressure of the fluid? If the blood vessel expands in diameter what happens to the pressure inside it? If the volume of blood goes up  pressure will ____ If you lose blood volume (bleeding)  pressure will ____

Blood Pressure – See Handout! BP Facts: BP is highest at the heart & decreases from there on That is why your carotid pulse is stronger than your wrist! Any factor that speeds your heart will increase BP! WHY? Your arteries can control BP by changing diameter according to your bodies need

Blood Pressure – See Handout! Low BP: reduces your capacity to transport blood, O2 in tissues go down. High BP: over time weakens the arteries and capillaries which may rupture. Sphygmomanometer measures blood pressure  120/80 gauge that measures the pressure that blood exerts during ventricular contraction (systolic blood pressure) ~ 120 mm Hg also measures pressure during ventricular relaxing (diastolic blood pressure) ~ 80 mm Hg

Blood Pressure Lab Investigation!

Blood Pressure 2 factor affecting blood pressure 1. Cardiac output  C.O.  B.P 2. Arteriolar Resistance  diameter  B.P  diameter  B.P

Cardiac Output Cardiac output - the amount of blood that flows from each side of the heart / minute Two Factors stroke volume heart rate

Cardiac Output Stroke Volume Heart Rate Cardiac Output = Heart Rate x Stroke Volume = 70 beat/min x 70 ml/beat = 4900 ml/min Stroke Volume the quantity of blood pumped with each beat ~ 70ml Heart Rate is the number of times the heart beats per minute

Cardiac Output Problem: Dusty has just finished exercising and in order for his heart to keep up with the increased oxygen demands it is pumping at 150 beats per minute. Dusty’s heart can deliver 70ml of blood per beat. What is Dusty’s cardiac output? Heart rate X Stroke volume 150 beats/min X 70ml/beat 10500ml/min or 10.5L/min

While waiting to complete lab: Read p 319 – 334 Complete: Case study on page 324, #1 – 10 on p 327 and #1 – 12 on p 335