A 63 year-old woman was brought to the emergency room by her daughter A 63 year-old woman was brought to the emergency room by her daughter.  The woman had shortness of breath, severe fatigue and weakness, abdominal distension, swelling of the ankles, pale, cold and moist skin and fluid sounds in both lungs. Further examination revealed slight cyanosis (bluish skin), distension of the neck veins, increased respiratory rate, enlarged heart with increased heart rate. 

The emergency room diagnosed the patient as having left ventricular failure resulting from myocardial infarction and admitted the woman to the cardiac intensive care ward.

BLOOD PRESSURE, HEART RATE & CARDIAC OUTPUT & ECGs

BLOOD PRESSURE (BP) force blood exerts against wall of a blood vessel average BP = 120/80 (systolic/diastolic) (units = mm Hg) systole = ventricular contraction (depolarization) diastole = ventricular relaxation (repolarization)

Cardiac Cycle http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__the_cardiac_cycle__quiz_2_.html

MEASURING BLOOD PRESSURE USING THE AUSCULATORY METHOD http://www.mayoclinic.org/diseases-conditions/high-blood-pressure/multimedia/how-to-measure-blood-pressure/vid-20084748

Pressure in Blood Vessels

contraction of left ventricle provides continuous high pressure to blood (pressure in aorta is so high that if cut, blood will spurt several meters) death occurs quickly if major artery cut  rapid blood loss and lowering of BP (volumetric shock) as arteries branch and blood flows farther from heart, pressure drops Closed circulatory system allows for high pressure and rapid transport low pressure in capillaries allows for exchange of oxygen for CO2 and other wastes from cells

REGULATION OF BLOOD PRESSURE BP INCREASES if either: the BLOOD VOLUME INCREASES OR the ELASTICITY of the ARTERIES DECREASES OR the HEART RATE INCREASES As BP increases, stretch receptors in arterial walls are triggered. Also, CO2 and O2 chemoreceptors in arteries detect changes in the concentration of these gases. Both kinds of receptors trigger the medulla oblongata, which releases acetylcholine from the vagus nerve, which directly innervates the SA node and slows heart rate, returning BP to normal.

When BP is too high or too low High BP (hypertension): danger of bursting vessels Aneurism - bulging vessels Brain (stroke), heart (heart attack), kidney (renal failure) 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 vagus and adrenal gland, thus increasing HR, leading to increased BP Stimulants Caffeine, nicotine, alcohol imitate the effects of adrenaline, increasing HR & BP

ELECTRICAL CONDUCTION Stimulation of the S.A. node causes the AV node to contract. From the AV node, impulses run through the Bundle of His to the Purkinje Fibres  these impulses cause ventricles to contract

CARDIAC CYCLE & ECG

Normal electrocardiograph The change in voltage produced by these electrical signals can be measured using a device called an electrocardioGRAM (ECG) The tracing produced by an electrocardiogram is called an electrocardioGRAPH Normal electrocardiograph Depolarization = contraction Repolarization = relaxation

Let’s play Doctor

Artificial Pacemakers They are useful if the SA node cannot transmit regular impulses It consists of: battery, timer and electrode These are inserted into heart region where the pacemaker would normally be Electrode sends out impulses at timed intervals to either speed up a slow heart or correct an erratic heart beat

REGULATION OF HEART RATE (HR) Although the regular beating of the heart is caused by spontaneous firing of the sino-atrial (SA) node, HR is also regulated by the medulla oblongata (MO). The vagus nerve connects the MO to the SA node. Two neurotransmitters have opposite effects: adrenaline INCREASES HR acetylcholine DECREASES HR

Cardiac Output (p.492) Cardiac Output (CO): volume of blood pumped by the heart per unit time 2 factors affect CO 1. heart rate (HR) - number of beats per minute (bpm) 2. stroke volume (SV) - volume of blood forced out of heart (i.e. ventricle) with each heartbeat (avg. person has a stroke volume of 70 mL) CO = SV x HR Values for the average person:  CO = SV x HR = 70 mL/beat x 70 beats/min = 4900 mL/min

Fitness (p.492 table) A low resting heart rate is considered an indicator of physical fitness because it means that stroke volume is high. Regular cardiovascular exercise can increase fitness by: increasing elasticity of ventricles increasing capacity of ventricles and thus also increasing stroke volume

TOMORROW Go straight to library computer lab