Cardio-Resp 3&4 Flashcards
1
Q
Which is greater LV or RV?
A
- LV performs more work by a factor of 5-7
- LV wall is thicker (8-10mm) vs RV (2-3mm)
2
Q
Atria and ventricles are separated into ______ by ______ and ____
A
2 functional units
by connective tissue
and one way atrioventricular (AV) valves that preveent backflow to atria
3
Q
AV valve between RA and RV
A
tricuspid valve
4
Q
AV valve bewteen LA and LV
A
mitral valve or bicuspid
5
Q
Valves located at origin of pulmonary artery and aorta are called…
A
one way semi-lunar valves
pump deoxy blood to lungs and pump oxy blood to body (respectively
6
Q
Semilunar valves open as a response to…
A
- the ventricles contracting. so that it can pump the blood out and through them
- ventricles relax, semi-lunar valves shut so no backflow to into ventricles
7
Q
How does blood travel from atria to ventricles?
A
-both atria fill with blood then contract simultaneously and send blood to ventricles
- then simultaneous contraction of ventricles (0.1-0.2 s) after
(one ventricle to pulmonary system - lungs; one ventricle to systemic system - body)
8
Q
Stroke volume
A
- ventricles contracting ejects 2/3 of blood contained
- the amount of blood coming from the ventricle in one heart beat
9
Q
End systolic volume
A
- the 1/3 of the initial blood volume in the ventricles
10
Q
Diastole
A
- filling of blood in ventricles (end diastolic - filled)
11
Q
Systole
A
- pumping of blood in ventricle (end systolic - pumped)
12
Q
Cardiac output equation
A
CO = heart rate x stroke volume
13
Q
Is the cardiac cycle equally split? Explain
A
at an average of 75bpm
- the cycle lasts 0.8 seconds
- diastole (atria contracted, ventricles relaxed - filling) = 0.5 s
- systole = 0.3 seconds
14
Q
3 regions of the heart that can spontaneously generate action potentials
A
- Sinoatrial node (SA node)
- AV node
- Purkinje fibers
15
Q
SA node
A
sinoatrial node
- functions as pacemaker
- located in right atrium near opening of superior vena cava
- vagus nerve innervates SA node, can adjust heart rate
16
Q
Action potentials originate at ____
A
SA node
17
Q
How do action potential spread to RA and LA?
A
spread to adjacent myocytes in RA and LA through gap junctions between cells
18
Q
What do specialized myocardial cells in the AV node do?
A
Since the atria and ventricles are separate
- these cells are required to move impulse from atria to ventricles
19
Q
Sequence of electrical activity of heart
A
- SA node
- AV node
- AV bundle, “bundle of His”
- descends down intraventricular septum, divides right and left with Purkinje fibers in ventricle wall
- endocardium to epicardium
- ventricles contract simultaneously
20
Q
Impulse starts at SA node
A
- SA node cells directly contact atrial muscle cells
- impulse spreads quickly (0.8 - 1.0 m/s)
21
Q
Impulse moves to AV node
A
- located in the posterior septal wall of the right atrium
- conduction rate slows (0.03 to 0.05 m/s)
- allows atria to contract and ventricles to fill
22
Q
Impulse moves to the atrioventricular bundle (of His)
A
- located between atria and ventricles
- it is the only connection between atria and ventricles
- conduction rate begins to increase
23
Q
Impulse to Purkinje fibres (bundle branches)
A
- conduction rate peaks
- rapid conduction caused by more positive resting membrane potential and many gap junction
- synapse directly with ventricular myocytes
24
Q
Electrocardiogram (ECG)
A
- recording of potential differences generated by heart
- conducted to body surfaces and recorded by electrodes on skin
- a recording of production and conduction of action potential in heart (not single action potential)
25
The sequence of ECG
- P wave
- PR segment
- QRS complex
- ST segment
- T wave
26
P wave
- right atrium with signal from SA node
| - spreads across both atria, causing muscle cells to depolarize and contract (atrial systole)
27
PR segment
- conduction after atrias contract, before ventricles contract
- flatline
- signal leaves atria and enters AV node before ventricles
28
QRS wave
- down to Q: enters the bundle of His
- up to R: spreads to bundle branch
- downto S: spreading through Purkinje fibers along ventricle walls
- contractile fibers contract rapidly and induce ventricular systole
- atrial repolarization also occurs but not depicted on the diagram
29
T wave
- ventricular diastole
| - ventricular repolarization
30
ST segment
-ventricles are depolarized
31
QT interval
-depolarization AND repolarization occurs
32
How does a MI look on an ECG?
- ST segment falls very low and has to curve up a lot to reach the T wave
- -this is the signal heading out of the ventricles as they relax, heading to diastole (T wave)
- but there is a problem with infact region that blocks them to do so
33
Bradycardia is due to what?
- right vagus innervates SA node and hyperstimulation causes bradycardia
- the vagus nerve slows down HR
34
Epinephrine
- catecholamine from adrenal medulla
| - activate in times of stress
35
Epinephrine causes
- increased heart rate, ionotropy
- increased cardiac output
- vasoconstriction of systemic arteries and veins
- muscle and liver vasculatore
- -low conc - vasodilation
- -high conc. vasoconstriction
36
Norepinephrine
-adrenal medulla catecholamine release, but most of it comes from sympathetic nerve spill over into the circulation
37
Norepinephrine causes
- increased heart rate, ionotropy
- increased cardiac output
- systemic vascular resistance therefore, increased arterial blood pressure
- vasoconstriction in systemic arteries and veins
38
Blockers
alpha and beta blockers
| - one can alter response but another adrenoreceptor can still bind the catecholamine
39
How does beta blockers treat cardiac function?
- beta blockers are used to treat chronic heart failure
- inhibits progressive deterioration of cardiac function
- blocks sympathetic activation
40
What does caffeine do to the heart?
- stimulates the CNS
- increases stroke volume (blood pumped from LV)
- incr. blood pressure
- incr. herat rate
41
What are heart muscle cells called?
myocardial cells / myocytes
42
Myocardial cell structure/components
- actin filaments
- myosin filaments arranged
- striated
- 2 organelles: mitochondria and sarcoplasmic reticulum (SR)
43
What is the structure called of actin and myosin filaments?
sarcomeres
| - contract via sliding mechanism
44
How are myocytes connected?
- gap junctions
- stained as "intercalated discs"
- located at the end of the myocardial cell
- permits electrical impulses to be conducted cell to cell (synchrony)
45
What is the main purpose of the SR?
Sarcoplasmic reticulum
| -Ca2+ handling
46
How does an electrical signal cause a heart muscle cell to contract?
- action potential originates at SA node
| - contraction from Ca2+ induced Ca2+ release
47
How does Ca2+ induced Ca2+ release work?
- Ca2+ enters myocyte cytoplasm through voltage gated channel
- stimulates opening of Ca2+ release channel in sarcoplasmic reticulum SR
48
Ca2+ from voltage gated channels serve as ______
a messenger for Ca2+ release channels (SR)
49
How do heart muscles relax after contraction?
Ca2+ in cytoplasm is pumped back into the SR. (Sarcomeres located in cytoplasm).
50
Excitation - Contraction Coupling in Cardiac muscle (5 steps)
Voltage gated calcium channels open and...
1. Ca2+ diffuse ECF to cytoplasm
2. Ca2+ release channels on SR open
3. Ca2+ released from SR (2nd pool of calcium) binds to sarcomere
- this stimulates contraction
4. Ca2+ ATPase pump returns calcium back into SR
5. Myocardial cell relaxes
51
Heart cells are arranged into long, rod shaped organelles that are called
myofibrils
52
What are Z discs?
- proteins that anchor thin protein filaments (actin)
| - separates each myofibril
53
What is the section of fibre between Z-discs called?
Sarcomere
54
What happens to the filaments when muscles contract?
thin filaments (actin)
thick filaments (myosin)
these slide past each other
Z dics move closer together
55
What gives the striated pattern?
overlapping thin and thick filaments
56
Recall the differences in the light and dark bands and zones within.
- light bands: "I bands"
- Z discs in middle of I band
- dark bands "A bands"
- "H zone" centre of A band where there is no actin present
57
Myosin
- thick filaments (TF)
- rod shaped protein with angular head at one end
- contraction causes swivel of head
58
Tropomyosin
attached to actin
| string like
59
Troponin complex
3 subunit attached to tropomyosin
60
How does myosin activation occur?
- myosin head has actin binding site and ATP binding site
- ATP to ADP (hydrolyzed); myosin head is activated and changes orientation
- Ca2+ to troponin causes movement of troponin-tropomyosin complex
- this exposes binding sites on actin
- myosin cros bridge can now attach to actin and undergo power stroke
(contracting: ca2+ binds, Pi released from ATP, myosin binds actin)
61
3 differences between cardiac and skeletal muscle contraction:
1. stimuli
- skeletal need external stimuli by somatic motor nerves
| - cardiac produces action potential automatically (SA nerve), involuntary
62
3 differences between cardiac and skeletal muscle contraction:
2.
- skeletal muscles are long and fibrous
- myocardial are short, branched, interconnected; tubular cells; adjoined to adjacent myocardial cells by electrical synapses (gap junctions)
63
3 differences between cardiac and skeletal muscle contraction:
3.
- skeletal have direct excitation-contraction coupling between transverse tubules and SR (same pool of calcium)
- cardiac havevoltage gated ca2+ channels in plasma membrane and Ca2+ release channels in SR do not directly interact
(Ca2+ induced Ca2+ release)
64
What is coronary artery disease?
- 1 or more of 3 coronary arteries have plaque build up
- partly restricts blood flow to heart causing chest pain/angina
- build up of artherosclerosis causes MI/heart attack (death of heart muscle cells)
65
Congestive heart failure
- heart pumps inefficiently and cannot meet bodily needs for blood
- ventricls (main heart pumps) cause insufficient flow
- often caused by CAD or MI
66
"congestive" congestive heart failure
- back up of blood in veins leading to the ehart
- causes the kidney to retain the fluid
- symptoms: water retention or edema in legs/ankles
67
Treatment to congestive heart failure
- beta blockers to help heart pump
- diuretics to remove salt and fluids
- late stage surgery / heart transplant
68
How do beta blockers work?
- beta blockers target beta receptor
- beta 1 adrenergic receptor (heart and kidneys) 1/3 beta receptors
- beta receptors bind catecholamines and blockers block the binding
= reduced heart rate
- beta blockers also affect RAAS system of kidneys and dilate arteries
69
Max heart rate _____ as age increases.
decreases
