A&P2 Lecture 1- Heart

winniesmith1's version from 2017-03-13 11:30

Section 1

Question Answer
Components of the cardiovascular system Heart, Blood vessels (Arteries,veins,capillaries) Blood
Function of the cardiovascular systemTransportation of blood (carries 02/CO2, transport & exchange of nutrients/dissolved gases/waste products, carries hormones)
What are the two circuitsPulmonary circuit (blood to and from lungs) and systemic circuit (blood to and from the rest of the body).
direction of blood in veinsblood towards the heart
direction of blood in arteriesblood away from the heart

Section 2

Question Answer
Where is the heart locatedIn the thoracic cavity (between lungs and behind the sternum). Centrally located but apex slightly to left of the midline.
How big is the heartsize of a closed fist (5" long, 3.5" wide, 2.5" thick) weighs 10-13oz
What factors significantly influence heart size?sex,height,weight and age
How many chambers does the heart have2 atria (upper) and 2 ventricles (lower)
Overview of atria primary receiving chambers, blood flows into atria from circulation
Overview of ventriclesReceive blood from atria, contract and pump blood out of heart into circulation
What are the left and right side separated bySeptum
what does the septum allow the heart to doact as a double pump (right side-pulmonary circulation, left side- systemic circulation)

Section 3

Question Answer
What does the right atrium doReceived deoxygenated blood from the systemic circuit via the vena cava
What does the superior vena cava dobrings deoxygenated blood from the upper body (arms, neck, head)
What does the inferior vena cava dobrings deoxygenated blood from the abdomen and lower body.
What does the right ventricle dopumps blood into the pulmonary circuit (lungs) via the pulmonary arteries (L&R)
What does the left atrium doreceives oxygenated blood from the pulmonary circuit via the pulmonary veins
What does the left ventricle dodischarges blood into the systemic circuit via the Aorta

Section 4

Question Answer
What are the layers of the heart wallPericardium,myocardium,endocardium
What is the pericardiumouter layer of fibrous tissues and an inner double layer of serous membrane
What is the pericardium made up of?fibrous layer> parietal layer (outer serous layer) > pericardial cavity (serous fluid) > visceral layer (inner serous layer)(epicardium)
Function of the pericardium Fixes the heart, prevents overfilling, lubrication
How does the pericardium fix the heartmakes attachment to the diaphragm, the sternum and the great vessels. Limits motion
How does the pericardium prevent overfilling?fibrous layer prevents the heart from increasing in size too rapidly, physical limit on potential size of the organ.
How does the pericardium provide lubricationthin film of fluid between two serous layers, reduces friction generated by heart as it moves within thoracic cavity.

Section 5

Question Answer
What is the myocardium the muscle tissue of the heart. forms thick muscular middle layer between the outer epicardium layer and the inner endocardium layer.
Compared to skeletal muscle fibres, cardiac muscle cells areshorter and wider, y shaped; branched, single centrally located nucleus, interconnect at intercalated discs, involuntary due to auto-rhythmicity (myogenic, ANS/endocrine system)
What do intercalated discs do?interconnect cardiac muscle cells, contain gap junctions (propagate action potentials), are secured by desmosomes, support synchronized muscle contraction.
What is the endocardiumthe innermost layer of tissue, lines all the chambers & valves of the heart, consists of epithelial and connective tissue.

Section 6

Question Answer
describe the thickness of the ventricle wallsThe wall of the LV is thick (cylindrical-like shape), whereas the wall of the RV is thinner compared to LV (pouch-like shape).
Why is the LV wall much thicker than RV? LV pressure system is high. Mean systemic pressure is 80-100 mmHg. Pumping blood around the systemic circuit requires 6-7 times more force than pulmonary circuit.
Why is the RV wall thinner than the LVas RV pressure system is low. Mean pulmonary artery pressure is <15 mmHg
How do valves work? (triscuspid and mitral valves).Attaches valve to papillary muscle(PM) on muscle wall. PM contracts to create tension on chordae tendinae, this prevents inversion of the valves during ventricular systole.

Section 7

Question Answer
What does the coronary circulation do?supplies blood to the muscle tissue of the heart.
how much blood do the coronary arteries carry?5-7% of blood
what can happen if the coronary circulation becomes blocked?Area of cardiac tissue is denied blood- myocardial infarction (heart attack). Lack of 02 triggering death of myocytes- impaired cardiac function.

Section 8

Question Answer
What is a heartbeatsingle contraction of the heart (atria first, then ventricles)
What are the 2 types of cardiac muscle cell (myocytes)Contractile cells: produce contractions (99%) and Cardiac pacemaker cells of the conducting system: controls/coordinates the contractile cells (1%)
Compare an action potential in skeletal muscle to an action potential in cardiac muscleIn comparison with skeletal muscle cells (2-3ms) cardiac muscle cells have a longer action potential (300ms), with a long plateau phase and a longer refractory period.
does cardiac muscle need stimulation to contract?No. Cardiac muscle is self-excitable. Contracts without neural or hormonal stimulation- Myogenic.
what is the conducting system made up ofnetwork of two types of specialized cells that distribute electrical impulses to cause contraction of the heart
what are the main components of the cardiac conducting system?Nodal cells and conducting cells (sinoatrial node, arterioventricular node, AV bundle, purkinje fibres.
What are the Nodal cells Sinoatrial node (SA node) and arterioventricular node  (AV node)
What does the sinoatrial node do?called the pacemaker. Starts a wave of electrical activity  which spreads  across the atria‐causing them to contract 
What do the conducting cells do?distribute the contractile stimulus to the myocardium. Elicits co-ordinated contraction.

Section 9

Question Answer
What is the first step in heart contraction/conducting system?SA node fires. Signal initiates at SA node on upper RA. Atrial activation begins.
What is the second step in the conducting system?Excitation spread through atrial myocardium. Signal spreads across atrial surfaces and reaches AV node on lower RA.
What is the third step in the conducting system?AV node fires. 100mv delay at the AV node. Atrial contraction begins.
What is the fourth step in the conducting system?Excitation spreads down AV bundle. Impulse travels along the AV septum within the AV bundle branches to purkinje fibres.
What is the fifth step in the conducting systemPurkinje fibers distribute excitation through ventricular myocardium. Atrial contraction completed and ventricular contraction begins.

Section 10

Question Answer
What is an electrocardiogram A recordings of electrical events in the heart.
What does systole meancontraction- short duration event
What does diastole meanrelaxation- longer duration event
What are the two main heart sounds First sound (lubb)   Produced as the AV valves close, and the  semilunar valves open  Second sound (dupp)  Closing of semilunar valves . Indicates start/stop of systole