Cardiovascular Physiology Lecture 4 Flashcards
(95 cards)
1
Q
The cardiac cycle can be divided into _______ (ventricular contraction) and _______ (ventricular relaxation)
A
The cardiac cycle can be divided into systole (ventricular contraction) and diastole (ventricular relaxation)
2
Q
What is Systole?
A
Ventricular contraction and blood ejection
3
Q
What is Diastole?
A
Ventricular relaxation and filling
4
Q
_______: period of time from beginning of one heartbeat to the beginning of the next
(each heart beat involves one ventricular systole and one ventricular diastole)
A
Cardiac cycle length: period of time from beginning of one heartbeat to the beginning of the next
(each heart beat involves one ventricular systole and one ventricular diastole)
5
Q
The heart spends most of the time in ______
*important for ventricular filling as the ventricles only fill when relaxed*
A
The heart spends most of the time in diastole
6
Q
What are the two phases of ventricular systole?
A
- Isovolumetic ventricular contraction
- Ventricular ejection
7
Q
When the ventricle contract, they squeeze the volume of blood in their chambers, generating _______ which creates blood flow
(recall flow = change in pressure / resistance)
A
When the ventricle contract, they squeeze the volume of blood in their chambers, generating pressure which creates blood flow
(recall flow = change in pressure / resistance)
8
Q
_________: same volume (constant/unchanging)
A
Isovolumetric: same volume (constant/unchanging)
“iso” = same
“volumetric” = volume
9
Q
What is isovolumetric ventricular contraction?
A
Phase of ventricular systole:
- Ventricles contract
- All heart valves are closed
- blood volume in ventricles remains constant but pressure rises
- muscle develops tension but cannot shorten
10
Q
What is the ventricular ejection phase?
A
Phase of ventricular systole:
- pressure generated by the ventricles during contraction now exceeds the pressure in the artery into which the ventricles eject blood
- forward pressure gradient:
- opens semilunar valves
- ventricular muscle fibres shorten
- Blood is ejected from ventricles
11
Q
During the ventricular ejection phase of systole, the AV valve is kept from inverting by the _______ and the ______
A
During the ventricular ejection phase of systole, the AV valve is kept from inverting by the chordae tendinae and the papillary muscles
12
Q
What is stroke volume?
A
Volume of blood ejected from each ventricle during systole or during contraction
13
Q
Which ventricle ejects the greater volume of blood?
A
Both left and right ventricle eject the same amount of blood. The only difference is that the left does so with more pressure
14
Q
What are the two phases of Diastole?
A
Two phases of diastole
- isovolumetric ventricular relaxation
- ventricular filling
15
Q
What has to be relaxed for for the ventricles to fill?
A
Ventricular myocardium (muscle layer of the ventricles)
16
Q
What is happening during isovolumetric ventricular relaxation?
A
Phase of diastole
- all heart valves closed
- blood volume remains constant
- pressures drop as myocardium relaxes
17
Q
What happens during ventricular filling?
A
Phase of Diastole
- AV valves open, blood flows passively into ventricles from atria (atria are relaxed)
- Two Phases:
- Passive ventricular filling
- Atrial contraction
18
Q
What are the two phases of ventricular filling?
A
Ventricular filling:
second phase of Diastole;
Two phases:
- Passive ventricular filling
- Atrial contraction (or atrial kick)
19
Q
What happens during passive ventricular filling?
A
First phase of the ventricular filling phase of diastole:
- the ventricles receive approximately 70% of their blood volume via passive ventricular filling
- blood flows from relaxed atria to relaxed ventricles
20
Q
What happens during atrial contraction?
A
second phase of the ventricular filling phase of diastole
- Atrial systole begins
- Atrial contraction forces small amount of blood into relaxed ventricle completing ventricular filling
21
Q
What is the cardiac cycle?
A
the rhythmical contraction and relaxation of the heart’s chambers coordinated by the electrical activity in the heart; represents the events that occur in the chambers of the heart during one single heartbeat
22
Q
What is the pressure-volume curve also called?
A
Wiggers diagram
23
Q
______ is the key to understanding blood flow patterns and the opening and closing of valves
A
Pressure is the key to understanding blood flow patterns and the opening and closing of valves
24
Q
When is pressure generated in the heart?
A
- When the muscles of the heart chamber contract
- When a chamber fills with blood
25
Valves open and close in response to:
Pressure gradient
* a forward pressure gradient opens a one-way valve while a backward pressure gradient shuts a one-way valve
26
The amount or volume of blood in each ventricle at the **end of ventricular diastole** (measured in millilitres)
End diastolic volume (EDV)
27
The amount or volume of blood in each ventricle at the end of ventricular systole, or at the end of ventricular contraction and ejection
(measured in mL)
Ends systolic volume (ESV)
28
The volume of blood pumped out of each ventricle during systole
Stroke volume
29
How do you calculate Stroke Volume (SV)?
SV = EDV-ESV
EDV = End diastolic volume
ESV = End systolic volume
30
Typical SV values for an adult at rest?
stroke volume for an adult at rest ~70-75mL
31
* What state are the left ventricle and left atrium in at the beginning of the Cardiac cycle (pressure-volume curve).
* Is the aortic valve open or closed?
* Is the AV Valve open or closed?
* What phase is this?
* Left atrium and ventricle are **relaxed.**
* Aortic valve is **closed**
* AV valve is **open** (pressure in the atrium is slightly higher than in ventricle)
* **Passive ventricular filling** (phase of ventricular phase of Diastole)
* ****Blood is passively flowing from relaxed atrium to relaxed ventricle
32
What does the P-wave signify on the pressure-volume curve?
What phase is this?
Atrial contraction
* more blood into ventricle
* small increase on the left ventricular volume curve (orange line)
* Phase: **Atrial contraction (atrial kick) phase of Ventricular Phase of Diastole**
33
What is the volume at the end of diastole called? In the first part of the Pressure volume?
What is its approximate value?
EDV
End diastolic volume
~135mL
34
What does the QRS complex signify on the pressure-volume curve (recall this is measured on an ECG)
Ventricular depolarization and contraction (systole)
35
The first heart sound (lub) is caused by:
Closure of AV valves at the beginning of isovolumetric ventricular contraction (of Systole)
36
What sound signifies the onset of ventricular systole?
What causes this sound?
Lub
Caused by closure of AV valves during isovolumetric ventricular contraction
37
What is the second heart sound "Dub" caused by?
What does it signify?
Closure of the **semilunar valves**
* signifies onset of ventricular diastole
38
The heart sound reflect _______ when the valves passively snap shut as the pressures across them changes
The heart sound reflect _turbulence_ when the valves passively snap shut as the pressures across them changes
39
What is a heart murmer?
Abnormal sounds produced by the heart.
Can be caused by defects that cause blood flow to be turbulent (normally **laminar** & makes no sound)
40
What is normal laminar blood flow characterized by?
Smooth concentric layers of blood moving in parallel down the length of a blood vessel
41
The flow profile is _____ once laminar flow is fully developed
The flow profile is _parabolic_ once laminar flow is fully developed
42
What is stenosis?
Blood flows rapidly through a narrowed valve (stenotic valve); leaflets do not open completely
43
What is a stenotic valve and how might it occur?
A stenotic valve is a valve in which the leaflets do not open completely;
Can occur when the valve leaflets become stiffer due to **calcium** deposits or scarring of the valve
44
What is an insufficient valve and how might it occur?
Valve does not close completely due to widening of the aorta or scarring of the valve
Blood flows backwards through the leaky valve and produces turbulence which is heard as a murmur
45
The heart is innervated by which division of the autonomic NS?
Both
Sympathetic - atria, ventricles, SA node, AV node
Parasympathetic - atria, SA node, AV node
46
Which nerve provides sympathetic innervation to the heart?
The thoracic spinal nerves
47
Sympathetic _______ fibres innervate the entire heart, including the atria, ventricles, SA node and AV node
Release the NT: \_\_\_\_\_\_\_\_
Sympathetic _Postganglionic_ fibres innervate the entire heart, including the atria, ventricles, SA node and AV node
Release the NT: _norepinephrine_
48
Which nerve provides parasympathetic innervation to the heart?
Vagus Nerve
49
Parasympathetic **postganglionic fibres** innervate the \_\_\_\_\_, \_\_\_\_\_, and \_\_\_\_\_
Releases the neurotransmitter: \_\_\_\_\_\_\_
Parasympathetic **postganglionic fibres** innervate the _atria, SA node_ and _AV node_
Releases the neurotransmitter: _acetylcholine_
50
Which part of the heart does not receive any parasympathetic innervation?
The ventricles
\*ventricular myocardium is not affected by parasympathetic activity\*
51
How does parasympathetic stimulation affect the heart?
(3)
* **Decrease heart rate** by decreasing rate of depolarization (or the rate of rise to threshold, of the pacemaker potential)
* **Decrease the conduction of the electrical impulses through the AV node**, increasing AV nodal delay (takes longer for stimulus to pass through the AV node into the ventricles)
* **Decrease contractility of the atrial myocardium**, decreasing the force of contraction
* \*no effect on contractility of the ventricles (no parasympathetic innervation)
52
What effect does Sympathetic Stimulation have on the heart?
1. **Increase heart rate** by
* increasing rate of depolarization (or the rate of rise) of the pacemaker potential to threshold
2. **Increase conduction of the electrical impulses through the AV node**
* ****Decreases AV nodal delay
* Less time for stimulus to pass through the AV node to the ventricle
3. **Increase the contractility of the atrial and *ventricular*** **myocardium**
* increasing force of contraction
53
What is the effect on the **SA Node** by:
* **Parasympathetic stimulation**
* **Sympathetic stimulation**
What is the effect on the **SA Node** by:
* **Parasympathetic stimulation**
* ****decrease rate of depolarization to threshold
* decrease heartrate
* **Sympathetic stimulation**
* ****increase rate of depolarization to threshold
* increase heart rate
54
What is the effect on the **AV Node** by:
* **Parasympathetic stimulation**
* **Sympathetic stimulation**
What is the effect on the **AV Node** by:
* **Parasympathetic stimulation**
* ****decrease conduction
* Increase AV nodal delay
* **Sympathetic stimulation**
* ****increase conduction
* decrease AV nodal delay
55
What is the effect on the **Atrial muscle** by:
* **Parasympathetic stimulation**
* **Sympathetic stimulation**
What is the effect on the **Atrial muscle** by:
* **Parasympathetic stimulation**
* ****decrease contractility
* **Sympathetic stimulation**
* ****increase contractility
56
What is the effect on the **Ventricular muscle** by:
* **Parasympathetic stimulation**
* **Sympathetic stimulation**
What is the effect on the **Ventricular muscle** by:
* **Parasympathetic stimulation**
* ****No significant innervation = no effect
* **Sympathetic stimulation**
* ****increase contractility
57
the amount of blood pumped by each ventricle in one minute; CO=(HR)(SV)
Cardiac output (CO)
58
How is Cardiac output calculated?
CO = heartrate multiplied by Stroke volume
**Stroke volume:** amount of blood pumped out of each ventricle during systole; typical SV ~70-75mL
59
How is cardiac output different than stroke volume?
Cardiac output differs from stroke volume in that it is measured per unit time
mL/min (CO)
vs
mL (SV)
60
Altering either the ________ or the _______ will alter the cardiac output
Altering either the _Heart rate_ or the _stroke volume_ will alter the cardiac output
CO=SV x HR
61
How is heart rate altered?
By modifying the activity of the SA node (heart's pacemaker)
62
How is stroke volume altered?
SV can be altered by varying the strength of the contraction of the ventricular myocardium
* when the ventricles contract, they do not empty their entire volume of blood
* altering the strength of contraction of the ventricular myocardium will alter the SV
* *Increased strength of contraction will increase SV (decreased strength of contraction will decrease SV)*
63
What does it mean that the heart has a resting *autonomic tone*?
Both the sympathetic and parasympathetic systems are active at a steady background level (called tone)
64
Parasympathetic and sympathetic effects are _______ for heart rate
Parasympathetic and sympathetic effects are _Antogonistic_ for heart rate
65
Under resting conditions, which branch of the ANS dominates Heart Rate?
Parasympathetic
66
Parasympathetic and sympathetic effects on the heart are _____ (originate outside of the heart)
Parasympathetic and sympathetic effects on the heart are _extrinsic_ (originate outside of the heart)
67
How is heart rate increased?
* increased _______ activity and increased release of ________ from the *adrenal \_\_\_\_\_\_\_* will stimulate/increase the activity of the _____ which increases heart rate and cardiac output
* As the sympathetic and parasympathetic are antagonistic, activity in the _______ system must be decreased
How is heart rate increased?
* increased _sympathetic_ activity and increased release of _epinephrine_ from the *adrenal _medulla_* will stimulate/increase the activity of the _SA node_ which increases heart rate and cardiac output
* As the sympathetic and parasympathetic are antagonistic, activity in the _parasympathetic_ system must be decreased
68
To decrease Heart Rate, must increase activity of the ________ division
* increased parasympathetic activity will ______ the activity of the ______ thereby decreasing the HR and CO
To decrease Heart Rate, must increase activity of the _parasympathetic_ division
* increased parasympathetic activity will _decrease/inhibit_ the activity of the _SA node_ thereby decreasing the HR and CO
69
What is responsible for initiating the heart rate?
**conducting myocytes** in the heart
* myocytes of the **SA node** are the heart's *pacemaker* generating the AP's that are responsible for HR
70
Epinephrine, a hormone secreted by the _______ into the blood, acts similarly to norepinephrine released by the \_\_\_\_\_\_\_\_
Epinephrine, a hormone secreted by the _adrenal medulla_ into the blood, acts similarly to norepinephrine released by the _sympathetic nerves_
71
To increase HR
* increased plasma \_\_\_\_\_, increased release of _______ from _______ nerves, and decreased release of _________ from parasympathetic nerves acts on _____ to increase hr
To increase HR
* increased plasma _epinephrine_, increased release of _norepinephrine_ from _sympathetic_ nerves, and decreased release of _acetylcholine_ from parasympathetic nerves acts on _SA node_ to increase hr
72
What are three factors that effect Stroke volume?
1. The end-diastolic volume (EDV) also called the *preload*
2. Contractility of the ventricular myocardium
3. afterload
73
What is EDV?
End diastolic volume : volume of blood in the ventricles at the end of ventricular diastole (after ventricles have finished filling)
74
The heart has an _______ mechanism to alter stroke volume
Intrinsic
75
The relationship between the end-diastolic volume and stroke volume is defined by the \_\_\_\_\_\_\_\_
The relationship between the end-diastolic volume and stroke volume is defined by the _Frank-starling mechanism_
76
What does it mean that stroke volume is intrinsic?
Ventricles will contract more forcefully when they have been stretched prior to contraction
And the stretching of the ventricles is increased by filling the ventricles with more blood
77
How do you fill the ventricles more fully with blood?
Increase the venous return
* fill ventricles more fully
* increase the EDV
* Increase SV
* increase CO
78
What is preload?
Tension (or load) on the ventricular myocardium before it begins to contract
(Aka EDV: amount of filling of the ventricles at the end of diastole)
79
How is venous return increased?
Sympathetic stimulation of venous smooth mm causing vasoconstriction (extrinsic)
\*parasympathetic innervation doesn't effect venous volume bc most vessels only have sympathetic innervation
80
What is the Frank-Starling Mechanism?
* Extrinsic or intrinsic
* stimulation from?
* describes the relationship between what two factors?
What is the Frank-Starling Mechanism?
* intrinsic
* Independent of neural or hormonal stimulation
* describes the relationship between End diastolic volume and stroke volume
* As you increase EDV you increase SV
81
Why does an increased EDV lead to an increased SV?
* main determinant for sarcomere length is the degree of \_\_\_\_\_\_\_
* the initial length of the sarcomere will affect the ______ generated during contraction
* As the ventricles become more filled with blood, the cardiac fibres on the sarcomeres stretch out, putting more load on the sarcomeres;
* how does this affect ventricular contraction and SV?
Why does an increased EDV lead to an increased SV?
* main determinant for sarcomere length is the degree of _diastolic filling_
* the initial length of the sarcomere will affect the _tension_ generated during contraction
* As the ventricles become more filled with blood, the cardiac fibres on the sarcomeres stretch out, putting more load on the sarcomeres;
* ventricles will contract more forcefully when they have been stretched and SV will increase
82
The frank-starling mechanism is a \_\_\_\_\_\_\_\_\_-\_\_\_\_\_\_\_\_ curve
The frank-starling mechanism is a _length-tension_ curve
83
What does the Frank-Starling mechanism ensure?
Matches the outputs of the two ventricles to ensure that the two ventricles pump the same amount/volume of blood and that blood doesn't accumulate in one circuit compared to the other
84
Under normal conditions the ejection fraction of the ventricles is between:
50-75%
85
What is contractility?
The strength of contraction at any given EDV
86
A change in the contractality of the ventricles will alter the _________ pumped by the blood during _____ (aka the \_\_\_
A change in the contractility of the ventricles will alter the _volume of blood_ pumped by the blood during _systole_ (aka the _SV)_
87
What effect would increased sympathetic stimulation have on contraction of the ventricular myocardium?
Increased sympathetic stimulation iwll increase the strength of contraction of the ventricular myocardium increasing SV and CO
88
How would increased parasympathetic activity affect the contractility of the ventricles?
Altering parasympathetic activity will not affect contractility of the ventricles and SV as the ventricular myocardium receives little or no parasympathetic innervation
89
Sympathetic stimulation ________ contractility
Sympathetic stimulation _increases_ contractility
90
How is the frank-starling mechanism altered under sympathetic stimulation?
Frank-starling mechanism still applies under sympathetic stimulation but during sympathetic stimulation, the stroke volume at any give end diastolic volume is GREATER
ie at the same EDV, there is an increase in SV under sympathetic stimulation
91
What effect does increased contractility have on ejection of blood?
Increased contractility leads to a more complete ejection of blood = increases ejection fraction
92
Calculate Ejection Fraction:
SV/EDV
Stroke volume
End diastolic volume
93
How does sympathetic stimulation give the ventricles more time to fill?
Under sympathetic stimulation, the heart contracts and relaxes faster, giving more time for the ventricles to fill despite the increase in heart rate
94
Sympathetic regulation of myocardial contractility acts through a _______ mechanism
Sympathetic regulation of myocardial contractility acts through a _G-Protein coupled_ mechanism
95
