Chapter 12: Blood Circulation and Blood Pressure

Question 1

Average Blood Pressure

Answer 1

120/80 mmHg (systolic/diastolic)

Question 2

Systolic Sound

Answer 2

heard at the beginning of VENTRICULAR systole
First sound (lubb)
Believed to be caused by contraction of ventricles and vibrations of AV valves closing (end of atrial systole).

Question 3

Diastolic Sound

Answer 3

heard at beginning of VENTRICULAR diastole
Short, sharp sound (dupp)
Thought to be caused by vibrations of SL valves closing (end of ventricular systole)

Question 4

Cardiac Output

Answer 4

Amount of blood pumped by the heart each minute
CO = HR x SV
Increases with exercise
Average CO = ~ 5-5.5 Liters/min (average)

Question 5

Parasympathetic NS

Answer 5

Decreases Heart rate

Question 6

Sympathetic NS

Answer 6

Increases Heart rate

Question 7

End Diastolic Volume (EDV)

Answer 7

AKA pre-load
Volume of blood in ventricles immediately before ventricular systole
Stroke volume is directly proportional to the EDV (preload)

Question 8

Norepinephrine

Answer 8

neurotransmitter released by Sympathetic branch

Question 9

Epinephrine

Answer 9

neurotransmitter release by Adrenal Medulla

Question 10

Norepinephrine and Epinephrine

Answer 10

Both bind adrenergic receptors on ventricular myocytes increasing force of contraction.
Increase available of free Ca+2 in myocardium,
Results in increased force of contraction,
Therefore more blood leaves the ventricles resulting in increased cardiac output.

Increase open probability of Na+ and Ca+2 channels,
SA node cells depolarize
Resulting in faster pacemaker potential

Question 11

Acetylcholine (ACh)

Answer 11

Increases open probability of K+ channels,
SA node cells repolarize,
Resulting in a slower pacemaker potential

Question 12

When blood flow to body needs to be increased

Answer 12

Activation of sympathetic branch (norepinephrine and epinephrine),
Increased cardiac output by increasing stroke volume, heart rate, amount of venous return to heart, fluid in cardiovascular system, and by decreasing blood pressure.

Question 13

When blood flow to body needs to be decreased

Answer 13

Activation of parasympathetic branch (acetylcholine),
Decreased cardiac output by decreasing stroke volume, heart rate, amount of venous return to heart, fluid in cardiovascular system, and by increasing blood pressure.

Question 14

Reflex integrator

Answer 14

coordinates autonomic stimulation through
Sympathetic (from Cardiac Plexus)
Parasympathetic (CN 10 – Vagus)

Question 15

Baroreceptors

Answer 15

detect pressure changes on aorta and carotid arteries.

Question 16

Chemoreceptors

Answer 16

detect levels of chemicals such as CO2, O2 and pH in blood and cerebrospinal fluid.

Question 17

Korotkoff Sounds (1st)

Answer 17

Sytolic: First sound heard
Caused by collapsed artery expanding enough to allow blood to flow during systole,
Can range from 110 – 130 mmHg

Question 18

Korotkoff Sounds (2nd)

Answer 18

Diastolic: Last sound heard
Caused by artery being completely open and not posing any resistance to blood flow during systole or diastole,
Can range from 60 – 80 mmHg

Question 19

Baroreflex

Answer 19

Baroreceptors in carotid artery,
are stretch receptors that detect increased arterial diameter during hypertension

Afferent neuron (glosophryngeal nerve, CN IX)
Sends information to nuclei in pons and medulla,
Interneurons synapse on efferent neuron (vagus nerve CN X - parasympathetic),
Which synapses on the terminal ganglion of the heart – postsynaptic neuron releases ACh to decrease heart rate.

Question 20

Compensation for Changes in Blood Pressure

Answer 20

Neural Reflex - first to respond (milliseconds)
Compensation for hypertension – decreased heart rate,
Compensation for hypotension – increased heart rate and increased strength of ventricular systole.

Neural Hormonal Reflex – responds within 24 hours
Compensation for hypertension – diuresis (↑urine volume)
Compensation for hypotension – water conservation

When BP is up, Baroreceptors (detect BP change) -> carotid artery -> glosophryngeal nerve -> Pons/Medulla -> Vagus Nerve -> Terminal Ganglion (HR decreases).