Chapter 19 - The Heart1 Flashcards
The cardiac cycle
Changes with in the heart from one heartbeat to the next
Contractor cardiac muscles
- Sarcolemma of a contract out cardiac muscle cell possess
RMP: -90mV - Action potential (initiated in the conduction system) will sweep through the cells causing depolarization
-90-> +30mV - Ca2+ Will enter sarcoplasm > find to troponin> shift tropmyosin> opening myosin binding sites> cross Bridge formation> Power stroke
Systole
Contraction of a heart chamber
Diastole
Relaxation of the heart chamber
Pressure changes in
contraction and
relaxation
Increase
Decrease
Pressure changes in the heart chambers are responsible for
1 movement of blood through chambers (from high to low blood will go) MAKES THINGS MOVE
2 opening of heart valves (ensures blood movement in forward direction)
PREVENT BACKFLOW
The exact order of events in the cardiac flow insures
Unidirectional flow of blood through the heart
Atrial systole
Atrial contraction forces additional blood to relaxed ventricles
Ventricular systole
(Contracting)
Ventricular contraction create P that:
a. shuts down the AV valves
B. opens SL valves and blood is ejected
Ventricular diastole
A. SL valves close
B. AV valves open and blood fills ventricles
End diastolic volume (EDV)
Volume of blood in the ventricles at the end of the filling
End systolic volume (ESV)
Volume of blood remaining in the ventricles after contraction
Stroke volume (SV)
Volume of blood ejected it with each heartbeat (SV=EDV-ESV)
Cardiac output (CO)
The amount of blood pumped by a single ventricle in one minute
Output is determined by:
Heart rate
Stroke volume
Heart rate (HR)
Number of beats per minute
Stroke volume (SV)
Volume of blood ejected during one beat
Cardiac output equation
HR x SV = CO
Total blood volume is about
5 Liters
-pumped the circulation every minute
Cardiac reserve
Increase in cardiac output above wrist level
Heart rate can> 170 beats per minute, while stroke volume> 100mL)
Cardiac reserve equals
Cardiac output with exercise - cardiac output at rest
Cardiac reserve is a measure of
Health and exercise
- Increase fourfold in healthy non-athlete
- Increased to seven fold in athlete
- With wakened heart may have a little reserve an exercise limitation
Cardiac output (CO)
Blood pumped per minute
Heart rate (HR)
Beats per minute
Chronotropic agents
Factors that change heart rate by altering activity of SA nodal cells
Positive chronotropic agents
Increased heart rate
- Sympathetic stimulation release of (norepinephrine)
- Release of epinephrine & norepinephrine by adrenal medulla
- Thyroid hormone
- Caffeine
- Nicotine
- Cocaine
Negative chronotropic Agents
Decreased heart rate
- parasympathetic stimulation (release of acetylocholine)
- beta-blocker drugs (used to treat high blood pressure)
Stroke volume (SV)
Blood volume ejected with each beat
Venous return
(Preload)
Volume of blood return to the heart
Inotropic agents
Substances that change stroke volume by altering contractibility )force of contraction)
Positive inotropic agents
Increases force of contraction by increasing calcium levels
- sympathetic stimulation release of norepinephrine)
- release of norepinephrine by adrenal medulla
- thyroid hormone
- certain drugs (example: digitalis)
Negative inotropic agents
Decrease contractility by increasing calcium levels
Ex: increased K+ or H+ levels
Certain drugs
Afterload
Resistance in arteries to ejection of blood by ventricles the pressure that must be overcome before blood is a ejected
A factor in the older people due to the Plaques in vessel lining
The increased afterload-the decreased SV
