anatomy lecture chapter 19- the heart

What is perfusion?

* Delivery of blood to tissues
* It considers the blood volume over a certain amount of time

\

When does adequate perfusion exist?

* Cell tissues receive enough oxygen and nutrients to meet energy demands
* Cells can clear them selves of waste products produced

What does inadequate perfusion result in

* Ischemia
* When oxygen and nutrient deprived tissues that become impaired and die

What is the order in which blood in pumped in the vessels

* Heart → Arteries → Capillaries → Veins → Heart

What are capillaries?

* Site of substance exchange

Where is the mediastinum

* Within the pericardial cavity

Which way is the heart rotated

* slightly right

Where is the base of the heart?

* The superior portion

Where is the apex of the heart

* The inferior portion

What are the layers of the heart’s membrane from superficial to deep

* Fibrous pericardium- keeps the heart in place
* Parietal pericardium- lines cavity
* Pericardial fluid/pericardial cavity
* Visceral pericardium/epicardium- covers the heart itself
* Myocardium
* Endocardium

The right side of the heart pumps blood to where

* The lungs via the pulmonary circuit

The left side of the heart pumps to blood to where

* The rest of the body via the systemic circuit

What is the epicardium?

* visceral pericardium, the outermost layer

What is the myocardium

* Middle thickest layer, has cardiac tissue

what is the endocardium

* Innermost layer, smooth tissue
* Lines the chambers of the heart

What is the pectinate muscle

* the endocardial lining of atria

What is the trabeculae carneae

* The endocardial lining of the ventricles

What are the auricles

* sacs of the exterior of the atria

What are the sulci

* grooves that mark the exterior of the septal walls, which are filled with adipose and blood vessels

What are the three sulci in the heart?

* Anterior interventricular sulcus
* Posterior interventricular sulcus
* Coronary sulcus

What are the four heart vessels in the body?

* Vena cava
* Pulmonary trunk
* Pulmonary veins
* Aorta

Where do the vena cava return blood to

* Deoxygenated blood to the right atrium

Where does the pulmonary trunk carry blood to

* Right and left trunks carry deoxygenated from the right ventricle to the lungs

where does the pulmonary veins return blood to

* Returns oxygenated blood to the left atrium from the lungs

Where does the aorta carry blood away from

* The left ventricle carries oxygenated blood to the systemic circuit

What is the function of valves

* To maintain one way blood flow

What are the four valves in the heart

* Tricuspid/right atrioventricular
* Bicuspid/left atrioventricular
* Pulmonary semilunar
* Aortic semilunar

What is the fibrous skeleton of the heart

* Collagen and elastic tissue network
* It reinforces the myocardium and anchors cardiac muscle fibers and valves

Fuction of the fibrous skeleton

* structural support where the atria and ventricles meet
* Forms supportive rings to anchor the valves
* Rigid framework to which cardiac muscle cells attach
* Blocks direct spread of electrical impulses from atrial to ventricular muscles (allows for impulses to flow through the designated circuit)

what are the three circuits in the heart

* pulmonary
* systemic
* coronary

what are the left coronary arteries?

* left anterior descending (LAD)
* anterior interventricular artery
* Circumflex artery
* “LAC”

What are the right coronary arteries

* Marginal branch
* Posterior interventricular artery
* “RaMP”

What do all cardiac veins converge into

* The coronary sinus

What is anastomoses

* Connection between blood vessels
* Can be used as a backup route for blood flow is a vessel is blocked

Where are gap junctions located

* Intercalated disks

What is ischemia

* Reduction of blood flow
* Can cause cells to die or be damaged
* The heart is very susceptible

Why is the heart susceptible to ischemia

* It has limited ability for glycolysis

What is the SA node

* pacemaker of the heart
* Fires 100 times per minutes (100 BPM)

What is the AV bundle

* brings impulses into ventricles
* runs through the interventricular septum after splitting into right and left branches

What are the Purkinje fibers

* the end of the circuits
* impulses run up the walls of the ventricles and into the papillary muscles

label

* 1. SA node
* 2. AV node
* 3. AV bundle
* 4. Purkinje fibers

What cells cause contractions in the atria

* SA node fires and the impulses spread to atrial cells through gap junctions

How does blood move

* high to low pressure

Electrical circuit pathway of the heart

* Atria contract → blood is pumped into the ventricles → electrical impulses run down the interventricular septum → ventricles contract and pump blood into the great vessels (RV to pulmonary trunk and LV to aorta)

What are the two types of cardiac cells?

* Conducting/rhythmic (1% of cardiac cells)
* Contractile (99% of cardiac cells)

what do conducting cells create?

* Action potentials used for cardiac muscle cells to contract

Why are nodal cells autorhythmic?

* Becuase of the leakiness of cell membranes to Sodium/Na+ ions, which control the heartbeat

What does the number of action potentials equal to in the heart

* the number of heartbeats per minute

Types of cardiac action potentials

* Those created by conducting cells, specifically the SA node
* Those characteristic of the cardiac muscle cells

Nodal cell AP steps

* **Reaching threshold**- Slow VG sodium channels open, and diffuses into the cell, MP goes from -60 to -40
* **Depolarization**- fast calcium VG channels open, and diffuses into cell, MP goes from -40 to-0
* **Repolarization**- Calcium channels close, VG potassium channels open, and diffuse out, Mp goes from 0 to -60, once MP reaches -60, potassium channels close

What is vagal tone

* Heart rate, ACh can slow that rate down

What is the effect of NE/Epi on nodal cells

* causes VG calcium channels to increase the movement of calcium into the cell
* this shortens the pacemaker potential and increases/the heart rate

What is the effect of calcium channel blockers on nodal cells

* Blocks movement of calcium channels
* this creates a longer pacemaker potential and heart rate is lowered
* Moderates contractile mechanisms

Contractile cell AP steps

* **Depolarization**- VG sodium channels open and enters the cell. Mp goes from -90 to +30
* **Plateau**- Calcium channels open, potassium goes out of the cell, slow VG calcium channels open and move into the cell, depolarization is sustained. muscle contraction
* **Repolarization**- VG calcium channels close, VG potassium channels still open and diffuses out. Mp goes from +30 to-90. Potassium channels close at -90. muscle relaxtion

What subdivision of the ANS increases heart rate

* sympathetic nervous system (Epi/NE)

What subdivision of the ANS decrease HR

* Parasympathetic (Ach)

what happens at a P wave

* SA node depolarizes
* Atria contracts
* Blood moves into ventricles

What happens at a PR interval

* Av node delay
* Atria complete contraction
* Ventricles fill w blood

What happens at the QRS complex

* Purkinje/HIS depolarization
* Ventricles contact
* Blood begins to be injected into the great vessels

What happens at the ST segment

* Purkinje/HIS depolarization completes
* Ventricles complete contraction
* Blood is ejected into great vessels

What happens at the T wave

* Purkinje/HIS repolarization
* Ventricles relax
* Blood moves passively from A to V due to P gradient

Label

* 1- P wave
* 2- PR interval
* 3/4- QRS complex
* 5- ST segment
* 6- T segment

What is the cardiac cycle

* repetitive pumping process
* systole and Diastole

What does it mean for the heart to be in systole

* contracting of the heart
* blood is ejected from the contacting chamber

What does it mean for the heart to be in diastole

* Relaxation of the heart
* Chamber refills with blood preparation for the next cycle

How are diastole and systole related

* When atria are diastole, ventricles are in systole

how are pressure and volume related

* When volume is high, pressure is low (vice versa)
* Systole increases chamber size, which causes chambers pressure to decrease

Cardiac cycle steps

1. Atrial contraction (atrial systole)
2. Isovolumetric contraction (ventricular systole)
3. Ventricular ejection (ventricular systole)
4. Isovolumetric relaxation (Atrial Diastole)
5. Atrial relaxation (atrial diastole)

How do you find stroke volume

* EDV-ESV=SV

how do you find cardiac output

* SV \* HR
* Convert to L from mL

What is the ejection fraction

* SV/EDV

whats a normal ejection fraction

50-65%

Whats the normal cardiac output

4-8 L/min

what is chronotropic

* The pace of the heart

what is positive vs negative chronotropic

* Positive means increase in HR
* Negative means decrease i hHR

What is bradycardia

* Resting HR lower than 60 BPM

What is tachycardia

* Resting heart rate more than 120 BPM

What are positive chronotropic agents

* Epi/NE
* Thyroid hormone
* Nicotine (increases release of NE)
* Cocaine (blocks reuptake of NE)
* Caffeine

What are negative chronotropic agents

* Parasympathetic stimulation (potassium leaves cell and hyperpolarizes)
* Beta-blocker drugs (blocks Epi/NE from binding to beta receptors)

What is stroke volume

* Volume of blood ejected during systole

What is venous return

* Amount of blood returning to the heart from the body via the great veins

What is preload

* Load placed on the cardiac myofibers and how much the fibers are stretched by the load

If you have a high EDV, how is stretching fibers and contraction force related

* you will have a high stretch of fibers and high contraction force

If you have a high preload, what will the SV and CO be

* They will both be high
* same is true for the opposite

What are inotropic agents

* external factors that influence the contraction of the heart
* Usually with the amount of calcium in the SR, which influence cross bridge formation

What are positive intropic agents

* Epi/NE
* Thyroid hormones
* Drugs
* These all increase calcium in SR and increase SV

What are negative intropic agents

* electrolyte imbalances
* Drugs

What is afterload

* Resistance in the arteries to bring blood being ejected by the ventricles
* When afterload increases ventricular pressure increases, which causes aortic pressure to increase (since blood moves to high to low pressure)

how does an increased afterload occur

* elevated BP
* loss of compliance/stiffening of arteries
* Reduced lumen size w atherosclerosis

Does body increasing body temp increase or decrease HR

* Increase HR

What is auscultation

* The sue of a stethoscope to listen to various sounds in the body

What are the two sounds heard in the heart and what causes them

* S1/lubb is the closing of the AV valves
* S2/dupp is the closing of the semilunar valves

When are the heart sounds in systole and diastole

* systole between S1 and S2
* Diastole between S2 and the start of S1

What are murmurs

* Abnormalities in the valves

When does the heart develop in an embryo

* 3weeks

When do the atrium, ventricles and septum form

* week 5

What is foramen ovale

* A hole between R and L atrium allows for blood flow R to L atrium to avoid the lungs
* Closes up after birth

When do the great vessels start to form

* 5-8 weeks

what are some things that happen to heart when someone is active

* Bradycardiac response
* increase SV
* Increase in LV size
* Higher arterial size
* Higher vasodilation responsiveness

what do conducting cells do?

\

generate their own AP and stimulate the contractile cells to contract