Ch 20 - The Heart Flashcards
(112 cards)
1
Q
Cardiovasc Sys. Functions
A
- Transport gas, nutrients, hormones, & metabolic wastes
- Regulation of pH and ion composition of interstitial fluid
- Restriction of fluid loss at injury sites
- Defense against toxins/pathogens
- Stabilization of body temp
2
Q
Components of Cardiovasc Sys.
A
a) blood - transport medium
b) heart - muscular pump that moves blood around the body
c) system of tubes/vessels - arteries, veins, capillaries
3
Q
Blood Vessels are arranged in two circuits:
A
- Pulmonary: to/from the lungs
- Systemic: to/from the rest of the body
4
Q
Pulmonary Circuit
A
to and from the lungs
5
Q
Systemic Circuit
A
to & from the rest of the body
6
Q
Where is the heart located?
A
in the mediastinum in the thoracic cavity, within the pericardial cavity surrounded by pericardial fluid
7
Q
The pericardium is compose of 2 parts:
A
a tough outer layer lined by a delicate serous membrane
Visceral & Parietal
8
Q
the fibrous pericardium is …
(structure/purpose)
A
a very dense and non-flexible CT that helps protect and anchor the heart
9
Q
Epicardium is another word for
A
visceral pericardium
10
Q
2 layers of Pericardium:
A
- Visceral pericardium - also called epicardium, adheres closely to the outer surface of the heart
- Parietal Pericardium - lines the inner surface of the pericardial sac
11
Q
Visceral Pericardium
A
adheres closely to the outer surface of the heart
12
Q
Parietal Pericardium
A
lines the inner surface of the pericardial sac
13
Q
Pericardial Fluid (function/location)
A
provides lubrication b/w parietal pericardium & visceral pericardium
14
Q
Visceral Mesothelium
A
refers to the mesothelial cells that make up the visceral pericardium/epicardium.
mesothelium is a type of simple squamous epithelium that lines body cavities and covers organs
15
Q
Cardiac Tissue
A
- Pericardium - loose fitting sac around heart
- Myocardium - heart’s muscular layer
- Endocardium - intimately covers inner chambers of heart (atrium/ventricles)
16
Q
Pericardium
A
- a loosely fitting CT sac that surrounds the heart
- the pericardial cavity contains a small amount of lubricating serous fluid that allows the heart to glide smoothly against the pericardium
17
Q
Serous Fluid
A
allows the heart to glide smoothly against the pericardium
18
Q
Myocardium
A
- the heart’s muscular layer
- cardiac muscle tissue
19
Q
Endocardium
A
a layer of simple squamous epithelial tissue that intimately covers the inner chambers of the heart (atrium and ventricles)
20
Q
the Fibrous pericardium is also called…
A
the dense fibrous layer
21
Q
Cardiac Muscle Tissue
A
- striated
- unlike skeletal muscle, shorter fibers
- fibers branch and only have one nucleus
22
Q
Cardiac muscle cells connect to & communicate with neighboring cells forming _ __________ _________
A
2 functional syncytiums
23
Q
2 functional synctiums of cardiac muscle
A
Atrial/ventricular
24
Q
cardiac muscles connect to & communicate with neighboring cells through ___ _________ in ____________ _____.
A
gap junctions in intercalated discs.
25
Chambers of the heart
Right/Left Atria
Right/Left Ventricles
26
Right Atrium
receives deoxy blood from:
- **superior vena cava** - blood from head/upper limbs
- **inferior vena cava** - blood from trunk/lower limbs
- **coronary sinus** - from cardiac veins
27
Left atrium
receives oxy blood from left/right **pulmonary veins**: drawn from the lungs
28
Right Ventricle
pumps blood into the **lungs** via the right/left **pulmonary arteries**
29
Left Ventricle
pumps blood **into the body** via the **aorta**
30
Which chamber of the heart is thickest and why?
Left Ventricle - pumping blood up/out of heart to the rest of the body, needs a lot of force/muscle
31
what shapes do the right/left ventricles look like from a top view
RV: half moon
LV: Full moon
32
Heart Valves
flaps of dense CT that act as one way valves
ie. blood can only flow in one direction
33
Atrioventricular Valves
**Tricuspid** - right AV valve
**Bicuspid (Mitral)** - left AV valve
34
Semilunar Valves
**Pulmonary** - b/w right ventricle and pulmonary artery
**Aortic** - b/w left ventricle and aorta
35
What determines the flow of blood in the heart?
**changes in pressure** determine the flow of blood in the heart and **cause the valves to open and close**
36
Blood moves along a _______ ________
pressure gradient (high to low)
37
38
What happens when the AV valves open?
1) blood returning to the heart travels through the atria and force the **AV valves** open
2) the **atria contract** forcing blood into the ventricles
39
What happens when the AV valves close?
1) the **ventricles** contract forcing blood against the AV valves
2)**AV valves close** (first heart sound)
3)**Papillary muscles** contract to stabilize the valves
40
Papillary Muscles
- attached to ventricle walls
- small muscle projections inside the ventricles that anchor the chordae tendineae
- when the ventricles contract, the **papi. muscles also contract, pulling on the chordae tendi. to keep the valves closed** and prevent the blood from flowing backward.
41
Chordae Tendineae
- thin, tendon-like cords that connect the AV valves to the papillary muscles
- they prevent the valve flaps from inverting when the ventricles contract
42
Function of papillary muscles/chordae tendineae
to contract (pap. muscles) during ventricular systole to **prevent prolapse** and ensure **one-way blood flow**
43
what are Stenotic valves and what do they result in ... what does it sound like?
a **Narrowed Valve**, results in reduced blood flow
**Turbulent flow** = murmur
44
What are **Insufficient Valves** and what do they result in ... what does it sound like?
a **Leaky valve**, results in reduced blood output due to regurgitation
**Turbulent backflow** = murmur
45
What happens in a **prolapsed** valve?
when the valve folds backward
46
Like neurons and skeletal muscle fibers, cardiac cells are capable of generating __________ _______
electrical signals (i.e. excitable tissue)
47
What leads to contraction in cardiac cells (similar manner as skeletal muscle fibers)
the electrical signals, **Action Potentials**, cause the release of calcium into the cytosol causing the interaction of **actin/myosin**
48
the cardiac cycle refers to
the repetitive contraction and relaxation of the heart
49
Systole
a term used to describe the **contraction phase** of the cardiac cycle
50
Diastole
a term used to describe the **relaxation phase** of the cardiac cycle
51
What is essential in order for the cardiac cycle to be effetive?
proper timing
- time must be permitted for the ventricles to fill
- the atria must contract prior to the ventricles
- and both the ventricles must pump the same amount of blood at the same time
52
The initiation of the cardiac cycle and the coordination of the complex timing of events is achieved by the _______ __________ ______
*Cardiac Conduction System*
53
The Cardiac Conduction System
initiates contraction of the heart chambers through a serious of electrical impulse through specific nodes and fibers in the heart
54
What is cardiac contraction initiated by?
- a group of specialized cells (not neurons) called the **Sinoatrial Node (SA node)**
- the electrical signal then travels through the interconnected atrial cells and reaches the **Atrioventricular Node (AV node)**, where the signal is slightly delayed
- the signal is then delivered to the ventricles by the **Bundle of His** and the **Purkinje Fibers**
55
Cardiac Conduction Pathway
SA node to AV Node, delayed, then to ventricles by Bundle of His and Purkinje Fibers
56
Where is the SA node located
in the roof of the right atrium
57
Bundle of His
collection of muscle cells specialized for electrical conduction **from the AV node to the point of the apex** of fascicular branches
58
the fascicular branches lead to
Purkinje Fibers
59
Purkinje Fibers
excite the ventricles cause the ventricle muscle to contract at a paced interval
60
what happens to the electrical impulse when it reaches the AV node
it is slightly delayed
61
Steps of Cardiac Conduction Sys.
1. Sinoatrial node reaches threshold and generates an action potential
2. Depolarization is spread to all the cells of the atria via gap junctions and internodal pathways... **a wave of contraction follows the wave of depolarization**
3. Depolarization reaches the AV node, which conducts the electrical impulse more slowly: 100msec delay... this **gives atria time to empty into ventricles**
4. The action potential is conducted from the AV node through the AV bundle and down the left/right bundle branches
5. The action potential reaches the **Purkinje Fibers** which conduct the impulse through the ventricles where it passes from cell to cell in the contractile fibers via gap junctions
62
What is the purpose of the delay when depolarization reaches the AV node?
gives the atria time to empty into ventricles
63
As ventricle **(depolarizes/hyperpolarizes)?**, ventricles are **(emptied/filled)?**, Av valves **(opens/close)?**, and the **(Ca++/Mg+)?** within each ventricular cardiac muscle is released from storage in the sarcoplasmic reticulum's, triggering the simultaneous **(contraction/relaxation)?** of each ventricular cell.
Depolarizes
Filled
Close
Ca++
Contraction
64
P wave
atrial depolarization
65
P-R interval
conduction through AV node and AV bundle
66
Q wave
beginning of ventricular depolarization
67
QRS complex
completion of ventricular depolarization
68
What happens during **Atrial Systole**?
the **atria contract**, pushing blood into the ventricles through the open AV valves
69
What electrical event triggers **atrial systole**?
The **P wave** on an ECG
70
What happens during **atrial diastole**?
the **atria relax and refill** with blood from the veins while the ventricles contract
71
When does atrial diastole occur in relation to ventricular systole?
it **overlaps** with ventricular systole
72
What happens during **ventricular systole**?
the **ventricles contract**, forcing blood into the aorta and pulmonary artery
73
what causes the first heart sound (S1, lub)?
**closure of the AV valves** at the start of **ventricular systole**
74
What electrical event triggers **ventricular systole**?
the **QRS complex** on an ECG
75
What happens during **ventricular diastole**?
the **ventricles relax**, allowing blood to flow in rom the atria
76
What causes the second heart sound (S2, dub)?
**closure of the semilunar valves** at the start of **ventricular diastole**
77
what electrical event corresponds to **ventricular diastole**?
the **T wave** on an ECG
78
the ____ node is responsible for initiating cardiac contraction. These specialized cardio____ achieve this by '___________' depolarizing
SA node, cardiomyocytes, spontaneously
79
what prevents the cells of the SA node from ever achieving a **true resting state**?
due to the plasma membrane of specialized cardiomyocytes being **leaky to Na+**
- as soon as they repolarize, they start depolarizing again)
80
what controls the heart rate and how
the **ANS**, by influencing the **rate of spontaneous depolarization** in the SA node
81
Plateau Phase
when **extracellular Ca++ moves into the cells** (through Ca++ channels) during depolarization
82
Calcium Induced Calcium Release
when the **influx of Ca++** causes the **release of more Ca++** from the sarcoplasmic reticulum
83
EKG is same as
ECG
84
Why is the ECG an important diagnostic tool?
it can detect abnormalities in cardiac conduction
85
3 stages of an action potential in a cardiac muscle cell
1. Rapid Depolarization - sudden spike
2. Plateau - slow flat to curved decline
3. Repolarization - steeper decline till flat bottom
86
Why can't summation occur in cardiac muscle contraction process and why is that important?
in a cardiac muscle cell, the **AP is prolonged**, and thus the period of active muscle contraction is also extended.
Because the **refractory period continues until relaxation is well under way**, summation cannot occur and **tetanic contractions do not occur**
This feature is vital because: a **heart in tetany could not pump blood**
87
Phase 1 of Cardiac Cycle
**Ventricular filling**
- the **volume** of blood in the ventricle **increases** passively due to the low pressure in the heart
- the **SA node** depolarizes leading to **atrial depolarization (P-wave)** and contract
88
Phase 2 of Cardiac Cycle
**Ventricular Systole**
- the depolarization wave reaches the **ventricles** and they begin to **contract** (QRS wave).
- when the ventricular pressure exceeds the atrial pressure, the **AV valve** closes (1st sound)
- blood propelled through the aorta
89
Phase 2 of Cardiac Cycle
**Early Diastole**
- as the pressure in the ventricle begins to decline, it is exceeded by the pressure in the **aorta**, causing the aortic valve to **close** (2nd sound)
90
How is Cardiac Output calculated?
CO = HR x SV
Cardiac Output = Heart Rate x Stroke Volume
91
Any factor that effects the _____ ____ or _______ ______ will affect **Cardiac Output**
Heart Rate or Stoke Volume
92
What is the **Cardiac Reserve**
the **difference b/w the CO at rest and the maximum CO** the heart can generate
93
How to calc your ave max HR?
~220 - your age
94
What determines max SV?
Heart size
95
Ave Cardiac Reserve is
4-5 times resting value
96
Exercise draws upon the _______ _______ to meet the body's increased physiological demands and maintain homeostasis
cardiac reserve
97
Starling's Law
- the more the heart is **stretched (filled)** before contraction, the **more forcefully the heart will contract** (increase SV)
- equalizes output of right/left ventricles
98
Coronary Circulation is
blood flow to the heart
99
Coronary Arteries
supply the myocardium with O2 and nutrients
100
What happens to coronary blood flow during ventricular contraction?
High intraventricular pressure compresses the coronary arteries in the myocardium, temporarily stopping blood flow
101
When does the myocardium primarily recieve blood?
during diastole, when the ventricles relax and coronary arteries are no longer compressed
102
What happens if the coronary arteries are blocked by plaques?
blood flow is reduced, failing to deliver oxy, which leads to **tiss ischemia (lack of oxy)**
103
Angina
chest pain caused by **reduced blood flow to heart muscle** due to **tiss ischemia**, often from coronary arteries.
104
MI
**Myocardial Infarction (Heart Attack)**
- caused by **blocked coronary artery**, leading to **permanent heart muscle damage** due to prolonged lack of oxy.
**causes death of cardiomyocytes**
105
When will blood actually flow through the coronary circulation?
only during the **relaxation phase of ventricular diastole**, when the coronary arteries are **no longer compressed**
106
Where do Coronary Veins collect into?
the **Coronary Sinus** on the back part of the heart
107
Coronary Sinus
empties into the **right atrium** where the deoxy coronary blood joins with oxy-depleted blood from the rest of the body
108
Atherosclerosis
a condition where **plaques of fat, cholesterol, and other substances** build up in the arteries, **narrowing** them and **reducing blood flow**, which can lead to **ischemia, angina, or MI**
109
The heart only receives blood during
diastole
110
what prevents blood flow during systole
high pressures
111
what is one factor not (directly) related to cardovasc. sys. that regulates blood flow to the heart
local metabolism
112
