Week 1- The Heart- Cardiovascular System Flashcards
1
Q
What is the size and form of the heart?
A
- roughly the size of a closed fist
- 4 chambered muscular organ
2
Q
Where is the heart located?
A
- Located in the thoracic cavity between the lungs
- Superior to the diaphragm and retrosternal
- Posteriorly it rests against the 5th to the 8th thoracic vertebrae
- Located approx. at the 2nd through 6th ribs
- Apex (bottom) lies on the diaphragm
3
Q
What are the functions of the heart?
A
- Generating blood pressure
- Routing of blood through the pulmonary and systemic circulatory routes
- Ensuring one way blood flow with a valve system
- Regulating blood supply to meet metabolic needs
4
Q
Is the right side of the heart low or high pressure?
A
- right side is a low-pressure pump
5
Q
Is the left side of the heart low or high pressure?
A
- left side is a high pressure pump
6
Q
What are the two sets of tubing?
A
- systemic circulation
- pulmonary circulation
7
Q
What is the pericardial cavity?
A
- space filled with fluid (approx 10-15 mls)
8
Q
What is the pericardial sac?
A
- double layered closed sac that surrounds and anchors the heart
- Loose fitting, inextensible
9
Q
Pericardium outer layer
A
- tough fibrous layer attached to the diaphragm, inner surfaces of the sternum and vertebral column
10
Q
Pericardium Inner Layer
A
- thin outer layer of the heart wall
11
Q
What is the serous membranes?
A
- secrete fluid to, lubricate the membranes to reduce friction during contraction
12
Q
What are the major structures of the heart?
A
- Atria and ventricles
- Valves (pulmonary, aortic, bicuspid, tricuspid)
- Vessels (aorta, pulmonary arteries and veins, superior and inferior vena cava)
- Chordae tendineae, papillary muscles
- Interventricular septum
- Right & left atria, right & left ventricles
- Septum
13
Q
Atria
A
- 2 superior chambers, R & L
- Receive the blood from the veins
- Walls are relatively thin
14
Q
Why are atria walls thinner?
A
- b/c they don’t need to generate much impulses as they are only moving blood a small distance to the ventricles
15
Q
Ventricles
A
- 2 lower chambers of the heart
16
Q
Why are ventricle walls thicker?
A
- b/c they are considered to be the primary “pumping chambers” as they are responsible to pump the blood out of the heart
- Left ventricle is thicker than the right as it is responsible to push blood to the entire body
17
Q
What are the 3 layers of the heart wall?
A
- Endocardium
- Myocardium
- Epicardium
- Pericardium surrounds all layers and encloses the coronary vessels
18
Q
What is the Epicardium?
A
- Visceral pericardium
- Outer layer of the heart
- Thin membrane attached to the outer surface of the myocardium
- Blood vessels that nourish the heart are inside the pericardium
19
Q
What is myocardium?
A
- Sandwiched between 2 layers of membranes (middle layer)
- Thickest wall of the heart
- Contraction of the myocardium provides the force that pumps the blood through the blood vessels attached to the heart
20
Q
What are the heart valves?
A
- Allow blood flow in one direction
- AV valves
- Semilunar
21
Q
Atrioventricular Valves
A
- formed of fibrous connective tissues
- 2 AV valves- mitral (bicuspid) and the tricuspid
- Allows blood from the atrium to the ventricles but not back
22
Q
Tricuspid
A
- right side, 3 cusps of tissue from the fibrous tissues that separate the atria and ventricles
23
Q
AV Valves
A
- Strands of tissues- called the Chordae Tendineae- extend from the cusps to the papillary muscles (located in the walls of the ventricles)
- Prevent the valves from being forced into the atria during ventricular contraction
- They are just the right length to allow the cusps to close and seal tightly
24
Q
Semilunar valves
A
- In the bases of the large arteries that carry blood from the ventricles
- Pulmonary and Aortic semilunar valves
- 3 pocket-like cusps (half moon shaped)
- Allow blood to exit the ventricles and prevent blood flow back into the ventricles
25
Q
Pulmonary
A
- at the opening b/t the R ventricle and the pulmonary trunk
26
Q
Aortic semilunar valves
A
- at the opening b/t the left ventricle and the aorta
27
Q
Coronary Blood Supply
A
- 2 major arteries- the right and the left coronary arteries
- These branch directly off the aorta immediately above the aortic valve
28
Q
Left coronary artery
A
- originates at the left cusp of the aortic valve
- divide into left anterior descending artery (anterior interventricular)
- Supplies 65-75% of the blood supply to the Left ventricle and septum
- Oxygenation and nourishment to the myocardial cells
29
Q
Right coronary artery
A
- Originate at the right cusp of the aortic valve
- Divides into the right marginal artery and posterior interventricular artery
- Supplies 25-35% of the blood supply to the left ventricle and all of the right ventricle
30
Q
Cardiac Veins
A
- Refer to the veins that drain the blood supply of the heart wall
- Collect the deoxygenated and metabolic waste rich blood from the capillary beds
- The venules then join together to form the veins
31
Q
How is blood supplied to the heart?
A
- Blood passes through to capillary beds in the myocardium and then drains via the cardiac veins
- Empty in to the coronary sinus in the right atrium- (collection of small veins that form this larger vessel)
- Right Coronary Vein- anterior
- Middle and posterior cardiac veins
- Small cardiac vein around the RA
32
Q
Heart Veins
A
- The heart veins collect deoxygenated blood containing metabolic waste from the myocardium
- Return it to the right atrium via the coronary sinus
33
Q
Cardiac Cycle
A
- Contraction and relaxation phases of the heart
- Contraction= systole
- Relaxation= diastole
- Atria and ventricles contract alternately, both relax between beats
34
Q
Cardiac Cycle- Broken down
A
- Blood enters the heart via the vena cava, enters into the right atrium
- Goes through tricuspid valve into the right ventricle
- The deoxygenated blood then leaves the heart through the pulmonary artery
- Blood then goes to the lungs to get oxygenated
- Back into the pulmonary veins- towards the heart
- Into the left atrium (oxygenated now)
- Through the mitral valve
- Into the left ventricle
- Out the aorta and to the body/organs
35
Q
Heart sounds
A
- sounds (“lubb-dupp”) produced by the vibrations from the closing of the heart valves
- 1st- AV valves- beginning of ventricular systole causes a low “lubb” sound
- 2nd- semilunar valves closing with ventricular diastole- “dupp” sound
- Defective valves that leak or do not open completely cause unusual turbulence in the blood flow, resulting in abnormal sounds often called murmurs
36
Q
Regulation of the heart rate- Autonomic
A
- Autonomic Regulation from the cardiac center in the medulla of the brain
37
Q
How do baroreceptors in the walls of the aorta and internal cartoid arteries work?
A
- in blood pressure and alert the cardiac center
- Then responds through stimulation of the sympathetic nervous system (SNS) or parasympathetic nervous system (PNS)
38
Q
Cardiac Center
A
- SNS innervation causes an increase in HR (tachycardia) and contractility
- PNS innervation causes a decrease in HR (bradycardia) and contractility (vagus nerve stimulation)
- Constantly changes to meet the needs of the body cells
39
Q
Sympathetic Innervation
A
- From the cardiac center- spinal cord to the SA node, AV node and portions of the myocardium
40
Q
Where is epi and nonepi secreted?
A
- Secreted at the synapses in the heart - increase the rate and strength of the contraction
- this in turn stimulate beta receptors and increased HR and contractility
41
Q
What factors increase HR?
A
- Elevated body temp
- Increased environmental temp
- Exercise
- Smoking
- Stress
42
Q
Parasympathetic Innervation
A
- Cardiac center to the vagus nerve to innervate the SA and AV nodes through the right and left vagus nerves
- Acetylcholine is secreted at the synpases- slows the rate (acts on muscarinic and nicotinic cholinergic receptors)
- The greater the frequency of impulses the slower the rate
43
Q
What other factors affect heart rate?
A
- Age, sex, physical condition, temperature, blood levels K+ and CA++ ions
- HR declines with age
- Faster in females
- Slower with good conditioning
- Increase with temperatures
- Increased CA++ increases with HR and prolongs contraction
- Excessive K+ (hyperkalemia) decreases HR and contraction, low K+- lethal rhythms
44
Q
Cardiac Muscle Cells
A
- Cardiocytes (myocardiocytes)
- Heart muscle cells build to form involuntary striated muscle strands
- Highly resistant to fatigue due to high level of mitochondria
- Break down nutrients into cell energy
45
Q
Cardiac Cells
A
- Intercalated discs synchronize the contractions of all cardio myocytes
- Unique to cardiac muscle, found where cells join end to end (allow all the cells to function as a single organ)
- Contribute to the superiority of conductivity
- These disks regulate the passage of positive and negative electrons
- Allows electrical current to spread rapidly throughout the myocardium
46
Q
As a result action potentials travel from cell to cell without delay
A
- Contain actin and myosin (protein filaments) for contraction capabilities
- Muscle contraction occurs when these filaments slide over one another repetitively
- Myofibrils lock together with other cells and increase their effciency
- Because they are mechanically, chemically and electrically connected they act as a single cell (functional syncytium)
47
Q
Contractile Cells
A
- Mitochondria produce ATP
- ATP provides the energy for contraction but needs O2
- There is no significant oxygen debt like in the skeletal muscles (eg. no deprivation like in muscle cells when working out)
- Cardiac muscle cells are limited to about 200 contractions/ min
- Tetany- contracted muscles building on one another to sustain the contraction
- B/c of the refractory period, this is not possible in cardiac muscles
48
Q
What are the properties of Cardiac Cells?
A
- Contractility
- Automaticity
- Rhythmicity
- Conductivity
- Refractory period
49
Q
What is contractility?
A
- ability to respond to an impulse by contracting
50
Q
What is automaticity?
A
- ability to generate their own impulses
51
Q
What is rhythmicity?
A
- regular impulse generation
52
Q
What is conductivity?
A
- ability to transmit impulses to adjacent cells
53
Q
What is refractory period?
A
- relaxation without response to another simulation
54
Q
What is cardiac output?
A
- CO is the volume of blood ejected by a ventricle in one min and depends on the HR and SV (CO= HR x SV)
- SV is the volume pumped from one ventricle in one contraction
- This means that the heart pumps an amount equal to the body’s total blood volume each minute
55
Q
What is stroke volume?
A
- Varies with sympathetic simulation and venous return
- When an increased amount of blood returns to the heart (exercise), the heart is stretched more, and the force of contracting increases
- During stress, exercise or infection- CO increases
