CH. 12 Lecture #1: QOD 1. What body cavity contains the heart? 2. What do we call heart cells? 3. T/F- the ventricles of the heart always contain oxygenated blood.

QOD #1-Location of the heart in the thoracic cavity

What is the design and function of the heart? Analogy: Heart “House” Atria: Smaller, more elastic, pump into ventricles Ventricles: Larger, more muscular, pump into arteries

heart_blood_flow.mpg

Compare the pulmonary & systemic circuits This is what you need to know for the quiz, along with the chambers, major incoming and outgoing blood vessels and the valves

What makes Heart Sounds: "Lubb-dupp” ? Measured with stethescope http://library.med.utah.edu/kw/pharm/hyper_heart1.html

Discuss with group 1.Damage to the semilunar valve of the right ventricle would affect blood flow into which vessel? 2.What prevents the AV valves from swinging into the atria? 3.Why is the left ventricle more muscular than the right ventricle?

Quick check questions: Discuss with group Damage to the semilunar valve of the right ventricle would affect blood flow into which vessel? What prevents the AV valves from swinging into the atria? Why is the left ventricle more muscular than the right ventricle? interfere with blood flow to pulmonary trunk/artery the chordae tendineae- papillary muscles contract, counteracting force pushing valves upwards Must generate enough force to send blood to whole body (except lungs)

Cells: short & branched Intercalated discs : high SA How does cardiac muscle differ from skeletal muscle? Cells: short & branched Intercalated discs : high SA Sarcoplasmic reticulum small

What role does Ca2+ ions have in cardiac muscle?

How does the heart pump blood? B on coloring A on coloring C on coloring E on coloring D on coloring

Why does the heart have a conduction system for its electrical signal? Larger diameter cells  faster electrical signals Myofibrils absent

What is the function of the fibrous skeleton and how does an electrical signal get through it? Fibrous skeleton (collagen fibers) holds valves in place, gives structure, prevents over expansion Signal delayed at AV node, what could cause this?

How electrical activity can be measured/monitored

Compare the contraction of a skeletal muscle to cardiac muscle: Skeletal muscle action potential lasts 10 msec Cardiac contractile cell AP lasts 250–300 msec Until membrane repolarizes it cannot respond to another stimulus This extends the refractory period Limits the number of contractions per minute

Compare this to the images on the previous slide: Spontaneous- autorythmic Compare this to the images on the previous slide: “Funny” (slow) Na+ channels open when membrane hyperpolarized Open Ca2+ channelsdepolarization, K+ channels open repolarize

Quick check questions: Discuss with group- 1.How does the fact that cardiac muscle does not undergo tetanus (as skeletal muscle does) affect the functioning of the heart? 2.If the cells of the SA node were not functioning, how would the heart rate be affected? 3.Why is it important for the impulses from the atria to be delayed at the AV node before passing into the ventricles? 4.What might cause an increase in the size of the QRS complex in an electrocardiogram?

Quick check questions: Discuss with group- How does the fact that cardiac muscle does not undergo tetanus (as skeletal muscle does) affect the functioning of the heart? If the cells of the SA node were not functioning, how would the heart rate be affected? Why is it important for the impulses from the atria to be delayed at the AV node before passing into the ventricles? What might cause an increase in the size of the QRS complex in an electrocardiogram? must relax long enough for chambers can refill with blood cells of the AV node would become pacemaker, but would beat slower -would not allow enough time for atria to finish contracting, ventricles would not be full, less efficient an enlarged heart- the more cardiac muscle that is depolarizing the larger the electrical event

What is cardiac output (CO)? How is it calculated?  

Where do autonomic neurons innervate the heart Where do autonomic neurons innervate the heart? How do they change heart rate?

Compare the autonomic system’s neurotransmitters Sympathetic system also increases ventricular contractility

Explain the effects of the autonomic system on the pacemaker cells & thus on heart rate

What factors affect stroke volume? CO = HR x SV

Frank-Starling Law: Why force of the heart increases with filling

Discuss with group Define cardiac output. 2. If the cardioinhibitory center of the medulla oblongata were damaged, which part of the autonomic nervous system would be affected, and how would the heart be influenced? 3. What effect does stimulation of the acetylcholine receptors of the heart have on cardiac output? 4. What effect does increased venous return have on stroke volume? 5. Why is it a potential problem if the heart beats too rapidly?

Discuss with group Define cardiac output. If the cardioinhibitory center of the medulla oblongata were damaged, which part of the autonomic nervous system would be affected, and how would the heart be influenced? What effect does stimulation of the acetylcholine receptors of the heart have on cardiac output? What effect does increased venous return have on stroke volume? Why is it a potential problem if the heart beats too rapidly? amount of blood pumped in 1 min-HR x SV = CO ml/min Parasympathetic/ heart would not be able to slow down will cause heart rate to decrease, therefore decreasing CO More blood coming back to heart will increase SV Not enough time for ejecting, too much blood left in heart