Study sets, textbooks, questions
Upgrade to remove ads
A&P: Heart Physiology
Terms in this set (90)
Help hold cells together, give structural integrity to the muscle sheet
What are cardiac myocytes?
Cardiac myocytes are connected toe ach other by?
Intercalated discs, that contain multiple gap junctions and desmosomes
The gap junctions allow the?
Spread of the action potential throug hthe muscle so that the cells contract together during a heartbeat
Briefly define an action potential?
-sodium channels open
-Calcium is released from the sarcoplasma reticulum
-Binds to the troponin
-which allows the myosin to bind to the actin
-causing a CONTRATION
In a cardiac muscle, what are the steps to an action potential?
What happens during the Plateau?
Allows for the ventricles to fill with blood
What is absolute refractive period?
The same as the Plateau
What are the two types of cardiac muscle cells?
(Create action potentials)
-includes pacemaker cells and cells of the conducting system that spread the action potential throughout the heart
Cells that create the force of contraction
What is the pacemaker cell?
The Sinoatrial node (SA Node) which starts the impulse
Describe the pathway of the pacemaker cells that make the heart contract?
-SA Node sends impulse
-Atrioventricular node (AV node)
-AV bundle (bundle of his)
-purkinje fibers that move back up the heart on the side
Purkinje fibers are?
much larger that contractile cells (action potential travels faster)
The SA node is located in?
The posterior walls of the right atrium, above the superior vena cava
The SA node has a pacemaker activity of?
80-100 action potentials per minute
The AV node has a pacemaker activity of?
40-60 action potentials per minutes
The SA node establishes the?
The conducting cells of the AV node are?
small, so the signal is conducted slowly through the AV node.
The delay between the SA node and the AV node allows for?
The atria to finish contracting before the ventricles begin to contract
Purkinje fibers radiate from the?
apex toward the base, so the wave of depolarization (and contraction) begins at the apex and streads toward the base (pushing blood up into the arterial trunks)
What are the three cardiac arrhythmias?
What does atrial flutter do?
ectopic focus, the atria are happily fluttering, not likely to kill you
The atria beats 200-400 times/min
What are PVCs?
prematrue ventricular contraction
-due to the irritation of the heart by stimulants, emotional stress, or lack of sleep
-can idicate more serious situations
What is ventricular fibirllation?
serious arrhythmia caused by electrical signals arriving at different regions of the myocardium at widely different times
What does ectopic mean?
out of place, it can disrupt timing between atrial and ventricular contrations
Abnormal pacemaker activity can lead to?
What is bradycardia
-slower than normal heart rate
What is tachycardia?
faster than normal heart rate
Impulse conduction through the heart steps
-SA node depolarizes and atrial activation begins
-The impulse slows down at AV node to allow time for atria to contract
-The impulse travels to apex (bottom) of heart to purkinje fibers that travels up through ventricles to cause ventricles to contract
A cardiac cycle consists of?
one complete contraction and relaxation of all four heart chambers
What is systole? (contraction)
chamber contracts and pushes blood into an adjacent chamber or into an arterial trunk
What is diastole? (relaxation)
chamber fills with blood and prepares for the next cardiac cycle
Phases of the cardiac cycles
-atrial systole begins
-atrial systole ends, atrial diastole begins
-ventricular systole begins
-ventricular diastole begins and ends
What happens during the ventricular systole
-first phase: Ventricular contraction pushes AV valves closed but does not create enough pressure to open sumilunar valves
-Second phase: as ventricular pressure rises, the semilunar valves open and blood is ejected
What happens during ventricular diastole?
-early:ventricles relax, pressure in ventricles drops, and blood flows back against cusps of semilunar valves and forces them closed (blood flowing into relaxed atria)
-late: all chambers are relaxe and ventricles fill passively
Explain the events of the cardiac cycle again?
(know the chart on slide 16)
-atrial contraction begins
-atria injects blood into ventricles
-atrial systole ends, AV valves close
-Isovolumetric ventricular contraction
-Ventricular ejection occurs
-semiluminar valves close
-isovolumetric ventricular relaxation
-AV valves open, passive atrial filling occurs
What is Isovolumetric relaxation?
The pressure falling with all valves closed
What is the end diastolic volume?
the amount of blood before systole occurs
What is auscultation?
Listening to the heart sounds by stethoscope
What is cardiac output?
The amount of blood pumped by the heart in one minute
How do you determine the cardiac output
The heart rate (beats/min)*Stroke volume (ml/beat)
What affects the heart rate?
autonomic innervation and hormones
What affects the stroke volume?
end-diastolic and end-systolic volume
What useful information can be provided by cardiac output?
indication of ventricular efficiency over time
Heavy exercise can increase?
cardiac output by 300-500%
What is cardiac reserve?
the difference between resting and maximal cardiac output
What does autonomic innervation of the heart affect?
It affects the heart rate and thus affects cardiac output
What part of the nervous system can help slow the heart rate down?
The parasympathetic nervous system
What nerve does the parasympathetic nervous system use to slow the heart down?
the vagus nerve (10)
What part of the nervous system speeds the heart rate up?
The sympathetic nervous system
What nerve does it use to do that?
The great cardiac nerve
Pacemaker cells have an increased number of?
leaky sodium channels
The normal pacemaker function have no?
resting membrane potentials, it is always moving and changing
In the pacemaker cells in a resting function, have?
Prepotential (spontaneous depolarization)
In the parasympathetic stimulation (vagus nerve) what does it do?
It increases permeability of pacemaker cells to potassium (moving out of cell) which is hyperpolarizing and slows the heart rate down
In the sympathetic stimulation (great cardiac nerve) what is happening?
It increases the permeability to calcium from interstitial fluid into the cell which will increase the contractility of the cells and is beating harder and decreases the systolic volume
What can affect your heart rate?
Hormones, such as E, NE, and thyroid hormone will increase your heart rate and contractility of the heart
What is the hypothalamus in control of?
It is in direct control of the medulla oblongata which contains the reflex centers that affect the heart rate directly
Explain the process from the hypothalamus to the heart rate?
The medullary centers control?
The autonomic input
What are two sensory inputs ?
responds to changes to pressure
responds to changes in oxygen and CO2
What are two "centers" that the sensory inputs affect in the medulla?
What does the cardioacceleratory center do?
It sends the sympathetic impulses to the heart which increases the heart rate (great cardiac nerve)
What does the cardioinhibitory center do?
It sends the parasympathetic impulses to the heart which slows down the heart rate (vagus nerve)
Chemoreceptors affecting heart rate are stimulated by?
a fall in the oxygen concentrations or by a rise in the carbon dioxide cocnentration
What is barostatic reflex?
An increase in blood pressure in the head/neck region will lead to a decrease in heart rate
What is the atrial relex or bainbridge reflex?
the reflexive increase in heart rate after an increase in venous return
What does EDV stand for?
End diastolic volume
What does it do?
- the amount of blood a ventricle contains at the end of diastole and just before contraction begins
What effects the EDV?
filling time and venous return
What does ESV stand for?
End systolic volume
What does it do?
-It is the amount of blood remaining in a ventricle at the end of systole and just before relaxation begins
What effects ESV?
What is preload?
degree of stretching experienced by ventricular muscle cells during ventricular diastole
What is contractility?
The amount of force produced during a contraction
What is Afterload?
The amount of tension the contracting ventricle must produce to force open the semilunar valve and eject blood
What are the three factors that affect stroke volume?
What does the preload do?
It is the amount of tension in the ventricular myocardium immediately before it begins to contract
What does the contractility do?
It is how hard the myocardium contracts for a given preload
Increasing the preload, increases?
Factors that increases contractility are?
Positive inotropic agents
Positive inotropic means?
increasing the strength of muscular contraction
Factors that decrease contractility are?
negative inotropic agents
Negative inotropic means?
weakens the force of muscular contractions
What does the afterload do?
The blood pressure in the aorta and pulmonary trunk immediately distal to the semilunar valves, it opposes the opening of these valves and thus limits stroke volume
What is the frank-starling law of the heart?
Stroke volume is proportional to the end diastolic volume, meaning the ventricles eject as much blood as they receive
Whitin limits, the more that they are stretched, the more they...
contract on the next beat
Sets with similar terms
Cardiac Physiology test 3
Ch. 20 The Heart: Review Questions
Chapter 20: The heart
Physiology Lab 7
Sets found in the same folder
Hepatic Portal System
Urinary System Anatomy
CH 21 Reproductive Systems
Chapter 25 HW
Other sets by this creator
EPI Chapter 3 Terms
A&P II Blood
Name three ways to protect yourself from stress.
Distinguish between primary care physicians and medical specialists.
Gina can cook basmati rice 3 1/2 times faster in her pressure cooker than in a regular pot. If rice normally cooks in 20 minutes, what is the cooking time in the pressure cooker (to the nearest second)?
Which of the following influences teens to stay alcohol-free? (a) Having peers who drink alcohol, (b) Seeing alcohol ads on TV, (c) Having parents who disapprove of alcohol use, (d) Attending alcohol-sponsored sporting events.
Recommended textbook solutions
Clinical Reasoning Cases in Nursing
Julie S Snyder, Mariann M Harding
Clinical Reasoning Cases in Nursing
Julie S Snyder, Mariann M Harding
Global Health 101
Douglas Singh, Leiyu Shi
Other Quizlet sets
Physics 1112 Exam 1
World geo chapter 3 North Africa/ Southwest Asia
Ch. 8 and 9 Bio Exam Questions
what are the 4 contraction of muscles
Which artery supplies the frog's head with oxygenated blood?
where is pressure the lowest in the cardiovascular system?
What are true physiological benefits of surfactant