Lab 2 Flashcards
What causes electrical currents to be generated?
impulses travelling through heart
Where do electrical current go?
into tissues around heart and some reach surface of the body.
How can u detect and record electrical currents?
What is a recording called?
a machine called an Electrocardiograph.
-recording called an electrocardiogram (ECG)
How do you determine the length of 1 heartbeat?
measuring time from one peak of QRS complex to another.
What does the cardiac cycle include?
1 complete cycle of contraction and relaxation of all chambers of the heart.
When both atria contract and then relax, what follows?
the contraction and then relaxation of both ventricles.
What does the cardiac cycles start with?
Ventricular filling phase- semilunar valves are closed and AV valves are open, allowing blood to flow from the atria to the ventricles.
What happens when the ventricles start to contract?
AV valves close and the 1 heart sound (S1) is heard.
What is the phase where pressure builds in the ventricles until the pressure in the ventricles meets the pressure in the vessels leaving the heart?
isovolumetric contraction phase
Which valves are open during the isovolumetric contraction phase?
none, all valves are closed and no blood leaves ventricles.
As pressure builds, _________ valves open and blood leaves the heart in the ________ and ____. this is called the ventricular ejection phase.
Semilunar;
pulmonary trunk;
aorta
What phase occurs when the ventricles relax causing blood to start moving backwards, down pressure gradient, forcing semilunar valves shut?
Isovolumetric relaxation
Which valves are closed during the isovolumetric relaxation phase?
all and no blood enters or leaves the ventricles.
S1 and S2 occur at the closure of what valves?
S1= both AV valves S2= both semilunar valves
When can a ‘splitting’ of either S1 or S2 be heard as the 2 valves closing separately?
in some healthy hearts and some disease conditions
Deep inspiration _____ pressure in thoracic cavity and _______ venous return into heart (atrial suction).
decreases, increases.
Where is the aortic valve located?
-2nd intercostal space, right of the sternum at the level of the sturnal angle
Where is the Pulmonary valve located?
2nd intercostal sapce or left of the sternum at the level of the sturnal angle
Where is the tricuspid valve located?
4th or 5th intercostal space
Where is the Mitral valve located?
4th or 5th intercostal space or just under left nipple
What is a heart murmur?
valve prolapse and regurgitation
The amount of blood that may be pumped by the heart in one min is called?
cardiac output (CO)
what is the average CO?
5 L/min but can increase to up to 25 L/min with strenuous exercise.
CO is directly related to?
Stroke volume (SV) and Hear rate (HR)
When a person exercises, signals from proprioceptors travel to the cardiac acceleratory center which signals the heart what?
signals the heart that the muscles are active and will need more oxygen
The cardiac acceleratory center exerts a positive chronotropic effect on the heart to increase ________.
HR
Effectors that connect the cardiac acceleratory center with the heart include?
sympathetic nerves, and SA and AV nodes.
With exercise, stroke volume ____.
increases
What is stroke volume?
the amount of blood that leaves the ventricle with each beat.
When is more blood returned to the heart then usual?
during exercise. (increasing SV)
The sympathetic nervous system signals the myocardium to contract ___ ________.
more strongly (increasing SV)
What is the major difference between action potential in a cardiac muscle cell (cardiosyte) compared to a skeletal muscle cell?
- Ca channals hold excitation at peak for prolonged time.
- allows for heart contraction to last longer
When the P wave occurs, the SA node fires causing the atria to _____.
depolarize
During the QRS complex on the ECG, signals travel down the AV bundle, bundle branches, to the ____________. ventricles __________. now ventricles contract.
purkinje fibers (apex), depolarize.
During the t wave, the ventricles _______.
repolarize.
The cardiac cycle ends with the ventricles in _________.
relaxation.
What structure electrical conduction system sets the heart rate? what would the resting heart rate be if this was the only regulator of heart rate?
the structure is SA nodes
if this was the only regulator, resting HR would rest at 100 bpm.
What division of the autonomic system plays a role in setting the Resting HR?
the parasympathetic nervous system.
Which division of the autonomic nervous system acts to increase the heart rate during exercise?
sympathetic nervous system
Which division of the autonomic nervous system acts on the cardiac muscle to increase the strength of contraction during exercise?
sympathetic nervous system
What receptor is used when the stimuli is the increase of CO2 in the blood? Where is it located? does HR go up or down?
chemoreceptors
location: carotid arteries and aortic bodies
HR- increases
What receptor is used when the stimuli is the increase of blood pressure? Where is it located? does HR go up or down?
Baroreceptors
location: carotid arteries and aortic arch
HR-Decreases
What receptor is used when the stimuli is exercise (muscle contractions)? Where is it located? does HR go up or down?
Proprioceptors
location: muscles and joints
HR-increases
What 2 control centers regulate HR?
cardioacceleratory center and cardioinhibitory center. both located in medulla
What are the effectors that actually change the heart?
sympathetic and parasympathetic
How can a stressful thought can lead to an increase in HR even when your sitting quietly?
activates cardiac center
What are the average resting values of the equation to determine resting cardiac output?
SV(70mL/beat) x HR(75beats/min)=resting CO(5250mL/min)
What are the 3 factors that affect Stoke Volume?
- Preload= amount of tension in ventricles before contraction
- Contractility= the force of contraction for a given preload.
- afterload= the blood pressure in arteries just outside the semilunar valves.
What is the difference in HR for a ranking of ‘poor’ vs. ‘excellent’?
excellent result would be due to lower overall HR meaning your body can meet your bodies need without working to hard.
