17 Regulation of the Heart

Question 1

It is the amount of blood pumped by either the right or left ventricle per minute

Answer 1

cardiac output (CO)

Question 2

It is the amount of blood pumped by the ventricle per heartbeat multiplied by the HR

Answer 2

stroke volume (SV)

Question 3

Stroke volume is equal to ____ minus end-systolic volume (ESV)

Answer 3

end-diastolic volume (EDV)

Question 4

What are the 3 regulation of stroke volume

Answer 4

preload

contractility

afterload

Question 5

-is the amount of stretch on the heart before contraction

-Cardiac muscle fibers are normally shorter than their optimal length for generating force. As a result, the stretch of these fibers results in increased contractile force

-is directly proportional to the volume of blood in the ventricles, or EDV

Answer 5

Preload

Question 5

Two factors affect EDV:

Answer 5

(1) duration of ventricular diastole

(2) venous return, the amount of blood returning to the heart

Question 6

-described as wherein greater stretch of the heart results in more forceful contraction

-It is the intrinsic ability of the heart to adapt to increasing volumes of inflowing blood.

-The greater the heart muscle is stretched during filling, the greater the force of contraction and the greater the quantity of blood pumped into the aorta. Within physiologic limits, the heart pumps all the blood that returns to it by the way of the veins.

Answer 6

Frank-Starling law of the heart

Question 7

is the strength of contraction at a given preload, and it is independent of muscle stretch and EDV. It is influenced by extrinsic factors such as the presence of inotropic substances

Answer 7

Contractility

Question 8

is the pressure that must be exceeded by the ventricles before blood can be ejected through the semilunar valves. Any factor that increases will increase ESV and decrease SV. Such factors include hypertension or narrowing of the arteries, as in arteriosclerosis

Answer 8

Afterload

Question 9

refers to the frequency of cardiac cycles and is usually measured by the number of beats per minute (bpm)

Answer 9

Heart rate

Question 10

Physiologic factors influencing the heart rate:

Answer 10

excitement, muscular exercise, high environmental temperature, digestion, and sleep

Question 11

What are the major chemicals that affect the heart

Answer 11

hormones

cations

Question 12

Epinephrine and NE are both released from the adrenal medulla, and, acting as neurohormones, increase HR and contractility. Thyroid hormones also increase HR and contractility

Answer 12

Hormones

Question 13

important in maintaining resting membrane potentials. Therefore, alterations of this concentrations will affect heart function. Elevated blood Na+ concentrations decrease HR and contractility by interfering with Ca2+ influx into the cardiac muscle fiber. Increased blood K+ also decreases HR and contractility, but it does so by inhibiting the formation of the action potential. Increasing blood Ca2+ levels increase HR and contractility by leading to increased intracellular Ca2+

Answer 13

Cations

Question 14

_____ nervous system increases the activity of the heart while the ____ nervous system has the opposite effect

Answer 14

Sympathetic

parasympathetic

Question 15

-This center receives input from sensory receptors, the limbic system, and the cerebral cortex. It directs the output from both the parasympathetic and sympathetic divisions of the autonomic nervous system

Answer 15

cardiovascular center

Question 16

sensory receptor that monitors the positions of the limbs and joints. Increased movement of joints, such as during exercise, sends signals resulting in a rapid rise in HR

Answer 16

Proprioceptors

Question 17

sensory receptor that monitor blood chemical changes that can lead to changes in HR

Answer 17

Chemoreceptors

Question 18

sensory receptor that are located in the aortic arch and carotid arteries. Sudden changes in pressure in these regions cause changes in HR

Answer 18

Baroreceptors

Question 19

____ is released by sympathetic nerve fibers in response to stressors such as fright, anxiety, or exercise;

Answer 19

Norepinephrine

Question 20

the parasympathetic nervous system reduces HR when stressors are removed. ____ hyperpolarizes membranes of cells – opens K+ channels, PNS fibers in vagus nerves to the heart can decrease CO

Answer 20

Acetylcholine