13.2 The Heart

Question 1

describe the heart

Answer 1

• muscular organ size of a fist
• has four chambers (2 thin walled atria & 2 thick walled ventricles)
• pumps blood

Question 2

what is the septums function

Answer 2

separates the heart into the right and left side

Question 3

what do valves do

Answer 3

direct the flow of blood and prevent any back flow

Question 4

chordae tendineae role

Answer 4

• strong fibrous strings
• attract to muscular projections of walls
• supports the valves and prevent them from inverting during contraction

Question 5

what are semilunar valves

Answer 5

• valves that connect to the aorta and the pulmonary trunk (aortic semilunar valve & pulmonary semilunar valve)
• resemble half moons

Question 6

how is the passage of blood through the heart

Answer 6

• both VC carry oxygen to right atrium
• right atrium sends blood through tricuspid valve to right ventricle
• right ventricle sends blood through pulmonary SL valve into pulmonary trunk.
• pulmonary trunk divides into pulmonary artery (lungs) and pulmonary vein (left atrium)
• the left atrium sends blood through biscupid valve to the left ventricle
• the left ventricle sends blood through aortic SL valve into aorta

Question 7

why is blood pressure greatest in the aorta

Answer 7

• left side of heart pumps whole body

- right side of heart pumps lungs

Question 8

stages of the cardiac cycle (heart beat)

Answer 8

• when atria contract, the ventricles are filling with blood and relaxed
• when ventricles contract, the AV valves close and SL valves open and blood pumps into pulmonary or aorta
• when heart is relaxed, both atria and ventricles are filling with blood

Question 9

intrinsic conduction system (function and what)

Answer 9

• causes rhythmical contraction of chambers

- SA node & AV node

Question 10

what initiates a heart beat

Answer 10

• SA node initiates a heart beat and automatically sends an impulse (causing atria to contract)
• theres a slight delay to allow the atria to finish contracting before ventricle contracts

Question 11

purkinje fibers fuction

Answer 11

-consists of specialized cardiac muscle fibers that efficiently cause the ventricles to contract

Question 12

what does the SA node do

Answer 12

• “pacemaker”
• keeps the heart beat regular
• if not working properly, AV node takes over although much slower

Question 13

The portion of the brain that controls heart rate

Answer 13

• Medulla oblongata (cardiac control center)

- can alter the beat of the heart by autonomic system and nervous system

Question 14

what does our extrinsic system do during exercise

Answer 14

• the heart pumps faster and stronger due to sympathetic stimulation
• releasing epinephrine and norepinephrine (hormones)

Question 15

how does the autonomic NS control our heart rate

Answer 15

autonomic NS has two parts:
sympathetic NS:
-increases HR
parasympathetic NS:
-decrease HR