Download heart rate

Vital Signs: Pulse & Heart Rate
Video 1.1: Basic Heart Anatomy
The Heart’s Location within the Thoracic Cavity
- The heart is a hollow, muscular, cone-shaped organ
o General location
a. Positioned in the mediastinum (explain what this means!)
b. within the _____________ cavity
c. between the _________ cavities
o enclosed by the pericardium
a. function –____________________
- Esophagus and trachea are posterior to the heart
The Heart’s Internal Structure
- 4 chambers, or compartments
o Two superior chambers, or _________
o Two inferior chambers, or ___________
o To prevent mixing of blood between chambers-- interatrial septum
and interventricular septum
 Ventricular walls are thicker than atrial walls because they are
responsible for pumping blood into the systemic and
pulmonary circulations
o Right atrium
 Receives deoxygenated blood from the body from three
vessels
 Explain the functions of each of the following vessels in terms
of where they carry blood to/from.
1. Superior vena cava
2. Inferior vena cava
3. Coronary sinus
 From the right atrium, blood goes to the right ventricle
o Right ventricle
 Pumps deoxygenated blood into the pulmonary trunk
o Left atrium
 receives oxygenated blood via the __________ veins
o Left ventricle
 Pumps oxygenated blood into the aorta
 Left ventricular walls are __________ than right ventricular
walls because they need to contract with more force in order
to send blood throughout the systemic circulation
- The systemic circulation supplies the tissues and organs of the body with
oxygenated blood
o the newly deoxygenated blood returns to the right atrium by the
superior vena cava, inferior vena cava, and coronary sinus
Video 1.2a: Your Beating Heart
The Heart at a Microscopic Level
- 2 functional units (syncytia):
o the atrial syncytium
o the ventricular syncytium
o Atria contract, then ventricles contract, then the heart relaxes
- Two types of cells in the heart wall
o Contracting cells
o Cells that generate an electrical signal (what is their role?)
 Form the cardiac conduction system:
 Occurs in each heartbeat
The Cardiac Conduction System
- Starts at the _________ node (SA node)
o Location: _________
o Part of the cardiac conduction system that generates an electrical
signal most rapidly
o Spreads signal over entire atrial syncytium causing atrial contraction
- Signal spreads to the ____________node (AV node)
- Signal passes through the atrioventricular bundle (AV bundle)
- Signal arrives in the interventricular septum
o Passes through two bundle branches (right and left)
- At apex, the fibers branch extensively, forming Purkinje fibers
- Electrocardiograms (ECGs) assess the cardiac conduction system
o Determine if electrical activity of the heart is working properly
Video 1.2b: ECG Demo
- ECGs are devices we use to detect the electrical activity in the heart
o Electrodes are placed on the body
 2 upper limb leads (Where do you attach them to the body?)
 2 lower limb leads (where do you attach them?)
 6 precordial leads (explain where they are attached to the
patient).
 Allows you to look at the heart from 12 different angles-> can
pinpoint location of abnormality, if present
- The current arising from the SA node is a positive current, called
depolarization
o The positive current passes
through the atrial walls
o A
negative
current
restores the electrical potential of the
atrium back to normal after the passing
of the positive current, this is called
repolarization
- Normal Sinus Rhythm (explain
the shape/size of each wave).
o P wave: first wave
o QRS
group of waves
complex:
second
 Consists of the Q, R, S waves
o T Wave: third wave
o Isoelectric lines –occur when there is no change occurring in the
electrical state of the heart (i.e., no depolarization or repolarization is
occurring)
 Between P wave and QRS complex
 Between QRS complex and T wave
Video 1.3a: Heart Valves, Part 1
- Heart valves ensure that blood flows in one direction through the heart
o Composed of dense, fibrous connective tissue
o covered in endocardium- function?__________
- Heart has 4 valves- organized as two pairs
o Atrioventricular valves (AV valves)
 Location: ____________
 tricuspid valve
 mitral valve:
 Close when ventricles contract and the pressure in the
ventricles exceeds pressure in the atria
 chordae tendinae: function:___________
 papillary muscles contract along with ventricles,
creating tension in the chordae tendinae, preventing the
free edges of the valves from swinging upward into the
atria
 Open after ventricular relaxation, when atrial pressure exceeds
ventricular pressure
o Semilunar valves (SL valves)
Video 1.3b, Heart Valves, Part 2
- Blood passes from right ventricle to the pulmonary trunk and from the left
ventricle into the aorta
o Semilunar valves:
 pulmonic valve:______
 aortic valve:__________
 When closed, the cusps fall into the center of the pulmonary
trunk and aorta to prevent backflow of blood from the vessel
into the ventricle
 When the ventricles contract, pressure in them increaseswhen ventricular pressure exceeds pressure in the aorta and
pulmonary trunk, the semilunar valves open
 When the ventricles relax, pressure drops- when the
ventricular pressure falls below the pressure in the aorta and
pulmonary trunk, the semilunar valves close
Movement of valves during the cardiac cycle
- When the heart is relaxed
o the semilunar valves are closed and the AV valves are open
 blood is coming back to the right atrium through the superior
vena cava, inferior vena cava and coronary sinus
 On the left side, blood is returning to the heart from the
pulmonary veins from the lungs
- Atria contract
o Pressure in atria increases
- Atria relax, ventricles contract
o Pressure in ventricles exceeds pressure in atria
o Pressure continues to climb as ventricles continue to contract ->
ventricular pressure exceeds pressure in aorta and pulmonary trunk
- Ventricles stop contracting, start to relax
- Cycle repeats
- When valves close, they cause vibrations to occur in the blood that’s
passing through the heart
o Vibrations are carried to the body’s surface and can be heard with a
stethoscope
o sound one:_________
o sound two:___________
Video 1.3c, Assessing Heart Rate Demo
- Auscultation:
- The heart is positioned deep to the sternum, slightly to the left of the
midline in the chest cavity
o the apex:
 Location:
 Orientation:
 point of maximal impulse- the most accurate place to check
heart rate
- Feeling the heart rate, or palpating, assesses the number of beats per
minute
- Auscultation allows assessment of heart rate as well as heart sounds
o Heart sounds include sound one and sound two, usually called S1 an
S2
 S1
 S2
- Physicians often auscultate
in multiple locations to assess
heart sounds related to the
specific valves
o aortic valve: _____
o pulmonic valve:____
o tricuspid valve: ____
o mitral valve: ______
- If a valve does not close all
of the way, it will make a swishing
sound
- If a valve does not open all of the way, it will make a clicking sound
Video 1.4a, The Cardiac Cycle, Part 1
Electrical Changes During the Cardiac Cycle
- Conduction system:
o Starts at the SA node
 Excitation of the atria creates the P-wave on an ECG
o Signal sent to the AV node
 Delayed for 1/10th of a second—
o Passed to AV bundle
 The only electrical connection between the atrial syncytium
and ventricular syncytium
o Excitation of the ventricles creates the QRS complex on an ECG
o Heart relaxes, ventricles repolarize
 Creates the T wave on the ECG
- These electrical signals create changes in the contracting cells, triggering
muscle contraction
Video 1.4b: The Cardiac Cycle, Part 2
Pressure Changes During the Cardiac Cycle
- Pressure changes in the heart cause the valves to open and close, to
prevent backflow of blood
o The P wave on an ECG is followed closely by an increase in atrial
pressure
 atrial contraction, atrial systole
 After atrial systole, the atria contract and pressure remains low
o The QRS complex on an ECG is followed almost immediately by an
increase in ventricular pressure
 The period of ventricular contraction is called ventricular
systole
 When ventricular pressure exceeds aortic pressure, the
semilunar valves open
 Once this pressure peaks, the ventricles stop contracting
o Pressure in ventricles falls below the pressure in the
aorta and pulmonary trunk
 The ventricles continue to relax and ventricular pressure
continues to fall
o When this pressure falls below atrial pressure, the
AV valves open
o The period when the ventricles are relaxed is called
ventricular diastole –during this phase, ventricles fill
with blood
Ventricular Volume During the Cardiac Cycle
- Ventricular volume is fairly high during relaxation, or diastole
- During atrial systole- a little more blood is pushed into the ventricles, so the
volume increases slightly
- Ventricles contract, pressure increases and volume decreases
o Blood is being ejected to the aorta and pulmonary trunk
o AV valves open and ventricular volume begins to increase again
Heart Sounds During the Cardiac Cycle
o Heart sound one indicates the start of ventricular systole
o Heart sound two indicates start of ventricular diastole
Video 1.4c: Assessing Pulse Demo
- Heart rate:
- Pulse:
o We assess pulse in elastic arteries, which can distend and retract
o Pulse and heart rate are typically the same in a person with healthy
cardiovascular function, but could be different if someone has poor
peripheral circulation or arterial disease
Locations to assess pulse:
- carotid artery
- brachial artery (at the antecubital fossa)
- radial artery
- femoral artery
- dorsalis pedis
- posterior tibial
Video 1.5: Cardiac Output
- Need to keep blood circulating through the body to supply the cells with
oxygen and nutrients and to carry away metabolic waste products
- Cardiac Output (CO) = the volume of blood ejected per minute
o Influenced by heart rate (HR) and stroke volume (SV)
o CO = HR x SV
- Stroke volume: the volume of blood ejected during a single heartbeat
o End diastolic volume (EDV):
o End systolic volume (ESV):
o Stroke volume = EDV - ESV
- Cardiac output can be increased or decreased to meet the needs of the
body
- The autonomic nervous system plays a role in regulating cardiac output
o Two branches: parasympathetic and sympathetic
 sympathetic division:
 in the heart, the sympathetic nervous system innervates
SA node, AV node and the contractile cells of the
myocardium
 when activated, causes the SA node to depolarize more
quickly and can shorten the delay at the AV node
o tachycardia = HR > 100 bpm
 sympathetic activation also causes contractile cells of
myocardium to contract more forcefully -> leads to
increased stroke volume
 parasympathetic division:
 in the heart, the parasympathetic nervous system
innervates the SA node & the AV node
 parasympathetic nervous system slows the SA node’s
rate of self-excitation
o parasympathetic signals are carried to the SA node
by the vagus nerve
o bradycardia = HR < 60 bpm