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Negative inotropic agents include hypoxia, acidosis, hyperkalemia, and a variety of synthetic drugs. These include numerous beta blockers and calcium channel blockers. Early beta blocker drugs include propranolol and pronethalol, and are credited with revolutionizing treatment of cardiac patients experiencing angina pectoris. There is also a large class of dihydropyridine, phenylalkylamine, and benzothiazepine calcium channel blockers that may be administered decreasing the strength of contraction and SV.

Afterload

Afterload refers to the tension that the ventricles must develop to pump blood effectively against the resistance in the vascular system. Any condition that increases resistance requires a greater afterload to force open the semilunar valves and pump the blood. Damage to the valves, such as stenosis, which makes them harder to open will also increase afterload. Any decrease in resistance decreases the afterload. [link] summarizes the major factors influencing SV, [link] summarizes the major factors influencing CO, and [link] and [link] summarize cardiac responses to increased and decreased blood flow and pressure in order to restore homeostasis.

Major factors influencing stroke volume

This table describes major factors influencing stroke volume. Preload may be raised due to fast filling time or increased venous return. These factors increase end diastolic volume and increase stroke volume. Preload may be lowered due to decreased thyroid hormones, decreased calcium ions, high or low potassium ions, high or low sodium, low body temperature, hypoxia, abnormal pH balance, or drugs (for example, calcium channel blockers). These factors decrease end diastolic volume and decrease stroke volume. Contractility may be raised due to sympathetic stimulation, epinephrine and norepinephrine, high intracellular calcium ions, high blood calcium level, thyroid hormones, or glucagon. These factors decrease end systolic volume and increase stroke volume. Contractility may be lowered due to parasympathetic stimulation, acetylcholine, hypoxia, or hyperkalemia. These factors increase end systolic volume and decrease stroke volume. Afterload may be raised due to increased vascular resistance or semilunar valve damage. These factors increase end systolic volume and decrease stroke volume. Afterload may be lowered due to decreased vascular resistance. This factor decreases end systolic volume and increases stroke volume.
Multiple factors impact preload, afterload, and contractility, and are the major considerations influencing SV.

Summary of major factors influencing cardiac output

This flowchart lists all the important factors that affect cardiac output.
The primary factors influencing HR include autonomic innervation plus endocrine control. Not shown are environmental factors, such as electrolytes, metabolic products, and temperature. The primary factors controlling SV include preload, contractility, and afterload. Other factors such as electrolytes may be classified as either positive or negative inotropic agents.
Cardiac Response to Decreasing Blood Flow and Pressure Due to Decreasing Cardiac Output
Baroreceptors (aorta, carotid arteries, venae cavae, and atria) Chemoreceptors (both central nervous system and in proximity to baroreceptors)
Sensitive to Decreasing stretch Decreasing O 2 and increasing CO 2 , H + , and lactic acid
Target Parasympathetic stimulation suppressed Sympathetic stimulation increased
Response of heart Increasing heart rate and increasing stroke volume Increasing heart rate and increasing stroke volume
Overall effect Increasing blood flow and pressure due to increasing cardiac output; hemostasis restored Increasing blood flow and pressure due to increasing cardiac output; hemostasis restored
Cardiac Response to Increasing Blood Flow and Pressure Due to Increasing Cardiac Output
Baroreceptors (aorta, carotid arteries, venae cavae, and atria) Chemoreceptors (both central nervous system and in proximity to baroreceptors)
Sensitive to Increasing stretch Increasing O 2 and decreasing CO 2 , H + , and lactic acid
Target Parasympathetic stimulation increased Sympathetic stimulation suppressed
Response of heart Decreasing heart rate and decreasing stroke volume Decreasing heart rate and decreasing stroke volume
Overall effect Decreasing blood flow and pressure due to decreasing cardiac output; hemostasis restored Decreasing blood flow and pressure due to decreasing cardiac output; hemostasis restored

Chapter review

Many factors affect HR and SV, and together, they contribute to cardiac function. HR is largely determined and regulated by autonomic stimulation and hormones. There are several feedback loops that contribute to maintaining homeostasis dependent upon activity levels, such as the atrial reflex, which is determined by venous return.

SV is regulated by autonomic innervation and hormones, but also by filling time and venous return. Venous return is determined by activity of the skeletal muscles, blood volume, and changes in peripheral circulation. Venous return determines preload and the atrial reflex. Filling time directly related to HR also determines preload. Preload then impacts both EDV and ESV. Autonomic innervation and hormones largely regulate contractility. Contractility impacts EDV as does afterload. CO is the product of HR multiplied by SV. SV is the difference between EDV and ESV.

Questions & Answers

sorry I cant see the full question
Jessica Reply
what was the question?
evelyna
what is spine as a bone marking?
John
similar to a crest but raised more
evelyna
pointed process
evelyna
slender
evelyna
pointed projection i meant
evelyna
what fills the hallow space in the middle of bones? thanks
John
marrow
evelyna
bone marrow
evelyna
hey you gotta read a book
evelyna
i just happen to take this bone chapter in my book last week so i remember
evelyna
yeah i should. how about the correct match of the number of tarsal, metatarsal and phalanges?
John
10, fingers and toes, u know this
Patrick
what is the difference between basal laminal and basal membrane
Nartey Reply
I think they r the same
Patrick
If one is missing the opsin which detects wavelengths of approximately 560 nm what color would they be unable to see?
Alicia Reply
how do I explain into details the epithelial tissue
Sir Reply
Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. An example is the epidermis, the outermost layer of the skin. There are three principal shapes of epithelialcell: squamous, columnar, and cub
DJ
thank you
Sir
explain how the intestinal irritation results in diarrhoea
Sir
what is cerebrospinal fluid
nitesha Reply
Cerebrospinal fluid is a clear, colorless body fluid found in the brain and spinal cord. It is produced by the specialised ependymal cells in the choroid plexuses of the ventricles of the brain, and absorbed in the arachnoid granulations.
DJ
cerebrospinal fluid is the fluid present in the brain and spinal cord
olusoga
it is whitish in colour
olusoga
what are the function of the blood
Hannah Reply
to transport oxygen in hemoglobin and nutrients
Thembani
ok
Hannah
describe the pulmonary circulation
Hannah
Which of the following structures contains membranes with mucus glands and blood vessels to help humidify and warm air?
Sheika Reply
thoracic pump for blood, and lymphatic flow for mucus membranes .
Rugiatu
explanation shortly about organizaton of human body
Maulidi Reply
the human body is the entire structure of a human being.it is composed of many different types of cells that together create tissues and subsequently organ systems.they ensure homeostasis and viability of the human body
Chundu
which is the largest body organ?
Carine Reply
skin
Vinod
hello everyone what is blood carcinoma?
Khabat Reply
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Many thanks for your cooperation
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Also please keep all the conversations in English language to be understandable for all users.
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Akash
smallest basic unit of life
Adna Reply
cell
Divya
how does the cell work
Akash
cells in our body together with similar cells and form tissues in our body
Chundu
different kinds of sutures and their functions...
Andy
its cell
Kalka
what is Gross anatomy
susana
gross anatomy is the study of what you can observe of the human body without a microscope.
Jessica
what is smallest bone
Gulista
excuse me if you are questing us or testing our knowledge?
Divya
stapes
Chundu
susana ...gross anatomy this are body structures tht we can see with our naked eyes
Otilie
How to work heart
anjali
how many organs in the body doctor
supreme
cell
Vinod
five vital organ hote hain beta koi mushkil pocho bacho wale question m ni dhekta
DR
beta cell is the basic setrecture and function unit of the body
DR
define the cns Dr. Shahid plz
REEMA
reema... cns .. central nervous system is the one of the two major division of the nervosu system
DR
what are the types of vein
Godwin Reply
what is a bone ?
Amoako Reply
give examples of short bones
Amoako
patella
Adna
how is a bone formed under the endochondral process
Juliet Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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