chapter 16

Question 1

what are the intrinsic and extrinsic factors that regulate heart rate during rest and exercise

Answer 1

• SA node (intrinsic)
• chemical messagers that are circulated through the blood to accelerate the heart before exercise begins and adjust once intensity increases (extrinsic)

Question 2

what are the components of a normal ECG

Answer 2

• p wave: depolarization of both atria
• qrs complex: depolarization of the left ventricle
• t wave: repolarization of both ventricles

Question 3

neural control

Answer 3

sympathetic nervous system increases the rate of blood flow and contractility through the AV node, Purkinje fibres and the septum
parasympathetic nervous system decreases the rate through the vagus nerve and the SA node which sets the resting heart rate

Question 4

what is the central command

Answer 4

area of the brain that takes input from baroreflexes (from arteries near the heart), cardiopulmonary reflexes (in the heart), and exercise pressor reflexes (from the skeletal muscles) and the output is action from other areas of the body (such as inactiviation of certain muscles while others are working harder and need the blood there instead)

Question 5

chemoreceptor

Answer 5

special nerve cells that sense changes in the chemical composition of the blood, monitor metabolites, and blood gases

Question 6

mechanoreceptors

Answer 6

respond to mechanical pressure such as touch, or vibration from the external or internal environments

Question 7

3 factors that affect blood flow resistance

Answer 7

1. blood thickness
2. length of conducting tube
3. blood vessel radius

Question 8

2 differences in blood flow dynamics to different tissues at exercise onset and during exercise

Answer 8

blood flow through arterioles and capillaries varies slightly as arterioles have smooth muscle which allows for them to dilate to allow for more blood to flow

Question 9

effects of epinephrine and norepinephrine during sympathetic stimulation

Answer 9

cause frequency and force effects on the heart
norepinphrine acts as a vasoconstrictor

Question 10

effects of acetycholine during parasympathetic stimulation

Answer 10

acetylcholine slows heart rate after sympathetic activity has occurred

Question 11

volume of flow in a vessel relates to two factors

Answer 11

1. directly to pressure gradient between two ends of the vessels
2. inversely to resistance encountered to fluid flow

Question 12

poiseuilles law

Answer 12

flow = pressure gradient x vessel radius / vessel length x fluid viscosity
- vessel length stays the same, blood viscosity changes very little, radius changes the most

Question 13

what are the two factors that contribute to reduced blood flow to non-active tissues

Answer 13

1. increased SNS outflow
2. chemicals stimulate vasoconstriction

Question 14

vasodilation is mediated by (7)

Answer 14

• temperature
• carbon dioxide
• nitric oxide
• magnesium
• pH
• adenosine
• potassium

Question 15

what is nitric oxides role in blood flow

Answer 15

signal molecule that dilates vessels and decreases resistance to allow for easier flow to occur