Heart Structure

Question 1

Describe the steps in the cardiac conduction cycle

Answer 1

SAN, made up of myocytes that don’t contract
Discharges => depolarizes neighbours, reaches AVN
Cardiac skeleton surrounding valves stops atrial conduction from spreading to ventricles

Wave of depolarization spreads down R and L bundle branch down to apex and up Purkinje fibres

Question 2

Differences between the L and R bundle branches

Answer 2

Right bundle branches, leaves inter ventricular septum early => moderators band
-Extends to papillary muscles, ensures that they contract before ventricles do

Left bundle branch has many branches
-Blood needs to be pumped with greater force, stronger

Question 3

Describe atrial fibrillation

Answer 3

SAN does not coordinate electrical impulses
Many impulses fire in the atria at different times
Not too serious

Question 4

Describe ventricular fibrillation

Answer 4

Affects bundle branches, affects cardiac output

More serious

Question 5

Describe the use of the cardiac pacemaker

Answer 5

Inserted under skin
-Lead in coronary sinus, RA, RV
Coordinates electrical impulses even when the heart starts malfunctioning

Question 6

Describe how a defibrillator works

Answer 6

Stops all cells from contracting, resets pacemaker function

Question 7

How is the cardiac conduction cycle sympathetically innervated?

What happens when it is sympathetically innervated

Answer 7

T1-4
Cardioacceleratory center in medulla oblongata

Impulse travels down nerve to T1-4
Sympathetic preganglionic
Cervical and sup thoracic ganglia
Sympathetic postganglionic fibre/cardiac nerve

Forms plexus in front and behind heart

Increased HR, increased strength of contraction, decreased AVN delay

Question 8

How is the cardiac conduction cycle parasympathetic ally innervated?

What happens when it is parasympathetically innervated

Answer 8

Vagus/X
Cardioinhibitory center in medulla oblongata
Synapses with vagal nucleus
Vagus

Synapses in cardiac plexus
Parasympathetic post ganglionic fibres

Forms plexus in front and behind heart

Decreased HR, decreased strength of contraction
Target SAN

Question 9

Relations of the vagus nerve

Answer 9

Between jugular vein and common carotid

Question 10

Sympathetic ganglia and head and neck that can innervate heart

Answer 10

Sup cervical ganglion => sup cardiac nerve
Middle cervical ganglion => middle cardiac nerve
Inf cervical ganglion => inf cardiac nerve

Question 11

Phrenic nerves, where do they come from and what do they innervate

Answer 11

C3-5

Innverate diaphragm but pass by heart

Question 12

Right coronary branch and vessels

Answer 12

Coronary osteum on aorta
R coronary branch starts on ant side
R coronary branch => SAN branch
R coronary branch => R marginal

AV nodal branch and post interventricular comes off R coronary vessel on posterior side of heart

Question 13

Left coronary branch and vessels

Answer 13

Coronary osteum on aorta
L coronary branch starts behind aorta and comes onto ant side

L coronary moves onto ant face

Circumflex goes around and to post side

Ant interventricular comes off L coronary vessel, passes down to apex and behind

Circumflex => L marginal

Question 14

What does each coronary artery supply

Answer 14

SAN branch, SAN

R marginal, R ventricles
Circumflex, back of heart to crux
L marginal, L ventricles

Ant interventricular, supplies bundle branches and septum
Post interventricular, supplies septum

AVN branch, AVN

Question 15

Explain what coronary dominance is

Answer 15

Most people have R coronary dominance where R supplies posterior interventricular

L coronary dominance, L supplies posterior interventricular

Some people have mixed dominance

Question 16

Nervous innervation of a heart attack

Answer 16

Sympathetic nerve synapse in dorsal root
Impulse sent up to brain

Somatic sensation nerve sent back down dorsal root, ganglion to T1-4

Pain felt in sternum and inside of left arm
Caused by death of heart muscle

Question 17

Describe the structure of the valves

Answer 17

Pulmonary valve (ant, L, R semilunar cusp)
Aortic valve (post, L, R semilunar cusp
Tricuspid valve (septal, ant, post)
Bicuspid valve (ant, post)

Question 18

Describe the structure of the aortic valve and how the coronary osteums function

Answer 18

R and L semilunar cusps have coronary osteum
Nodule on ends of valve prevents back flow of blood into ventricles

When aortic valves closed due to atrial systole, back flow of blood from aorta gets caught in cusps and flows into coronary system

Question 19

How to auscultate heart valves

Answer 19

Place stethoscope in intercostal space where the blood will flow to, having passed the valve

Sounds carried in blood in outflow