Heart Anatomy (External and Internal)

mrs. garcia said the nervous system was the hardest but ts is definitely the hardest unit like why tf is the heart so GODDAMN COMPLICATED GRRRRRR

Heart Location and Other Facts

the heart is a hollow muscular organ about the size of a closed fist located between the lungs

the apex (tip) of the heart is pointed towards the left hip

contracts about 72 times per year

Pericardium

a protective layer of tissue protecting the heart

Layers of Pericardium (Superficial to Deep)

Fibrous Pericardium - provides protection and anchors the heart in place

Serous Pericardium - provides lubricating fluid which collects in the pericardial cavity to reduce friction of the heart against other tissues

• Parietal Pericardium (superficial to the pericardial cavity)

• Visceral Pericardium (deep to the pericardial cavity)

2 Cardiovascular Circuits

Pulmonary Circuit (oxygenating blood)

Systemic Circuit (distributing to body tissues)

Pulmonary Circuit

carries blood from the heart to the lungs and back

picks up O2 and released CO2

Major Blood Vessels involved in this Circuit:

• pulmonary trunk (splits into right and left pulmonary arteries)

• pulmonary veins

Systemic Circuit

carries blood from the heart to the body tissues and back

drops of O2 and picks up CO2

Major Blood Vessels involved in the Circuit:

• Venae Cavae (superior and inferior)

• Aorta

Chambers of the Heart

4 chambers:

• 2 atria (right and left atriums) (receive blood) (on top)

• 2 ventricles (right and left ventricles) (pump blood out) (on bottom)

Left Side of the Heart: receives oxygenated blood from the pulmonary veins

Right Side of the Heart: receives de-oxygenated blood from the body tissues

Septum

The barrier in the middle to prevent the oxygenated and de-oxygenated blood from mixing.

Superior Vena Cava

returns blood to heart from the upper body (blue)

Inferior Vena Cavae

returns blood to heart from lower body (blue)

Right Atrium

receives de-oxygenated blood from body tissues

covered by auricle (the blobby tissue you actually see)

Left Atrium

receives oxygenated blood from the lungs

covered by auricle (the blobby tissues you actually see)

Pulmonary Veins

brings oxygenated blood from lungs

although it transports oxygenated blood (making it show up as red on a heart diagram), it is classified as a vein as it is bringing blood to the heart which is what veins do

Pulmonary Arteries

carries de-oxygenated blood to the lungs to pick up oxygen

although it transports deoxygenated blood (making it show up as blue on a heart diagram), it is classified as an artery because it is moving blood away from the heart

Coronary Blood Vessels

provide oxygen to the heart itself

veins (blue), arteries (red)

Right Ventricle

receives de-oxygenated blood from the right atrium

Left Ventricle

receives oxygenated blood from the left atrium

Aorta

takes oxygenated blood to the body tissues

Apex

tip of the heart (pointed to the left hip)

Valves

flaps of tissue that prevent blood from flowing backwards

like a set of swinging doors

the opening and closing of these things are what make the heartbeat sound

Atrioventricular Valves

• between atria and ventricles

• tricuspid and bicuspid/mitral valves

Tricuspid Valve

valve that have 3 flaps of tissue

can be found in between right atrium and right ventricle

Bicuspid Valves

valve that have 2 flaps of tissue

can be found in between left atrium and left ventricle

Semilunar Valves

• prevents backwards flow into the heart

• pulmonary valve: between left ventricle and pulmonary vein

• aortic valve: between right ventricle and aorta

Systole

contraction of heart chambers (atrim and ventricle)

Diastole

relaxation of heart chambers (atrium and ventricle)

The Cardiac Cycle

• changes in pressure in heart chambers opens and closes valves, which create the cycle

Atrial Systole

• Movement of Blood: into the ventricles

• Ventricles are relaxed, Atria are contracted

• AVs are open, SLs are closed

Atrial Diastole/Ventricle Systole

Movement of Blood: from ventricles into the pulmonary vein/aorta

Atria are relaxed, Ventricles are contracted

AVs are closed, SLs are open

Isovolumentric Contraction

this is the step between atrial systole and ventricular systole

this is when the ventricles contract to increase pressure to open the semilunar valves, but they do this in a way that dosent affect blood volume (so not actually squeezing anything out)

Cardiac Conduction System

• the heart is autorhythmic, meaning that it contracts by itself without external nervous system stimulation

• the heart contains specialized cells that generate and distribute cardiac cell impulses

SA Node (Sino-Atrial Node)

• Pacemaker of the heart (since it starts the cardiac impulses)

• located in the right atrium (ONLY THE RIGHT ATRIUM) near the superior vena cava

• it initiates rhythmic contractions and contracts the atria

• (the impulse travels to the left atrium through interatrial pathways called Bachmann’s bundles and contracts the left atrium at the same time as the right atrium)

AV Node (Atrio-Ventricular Node)

• located in the superior part of the septum

• controls timing of contraction between atria and ventricles

• delays signal

• (delaying the signal is important because this delay allows the ventricles to be filled up with blood (after the atria contract) before they contract and send the blood to their respective locations)

AV Bundle

• connects the atria to the ventricles

Bundle Branches

travel through the septum to the left and right sides of the heart

basically when the AV bundle splits, it splits into the right and left bundle branches

Purkinje Fibers

branched network that stimulates the myocardium to contract the ventricles

EKG

• a measurement of electrical activity and impulses created by the heart

• EKG or ECG

• electrodes are placed on the chest and each impulse is translated into a wave pattern

What do the EKG Lines mean?

• flat lines: no electrical activity

• upward spikes: depolarization

• downward spikes: repolarization

P Wave in EKG

depolarization of the atria (which causes the atria to contract)

Gap Between P Wave and Q Spike

This is the delay in electrical signal caused by the AV Node

QRS Wave/Complex

• caused by the depolarization of ventricles and repolarization of atria

• this wave is much bigger than the P wave because the ventricles are bigger than the atria

Gap Between QRS Complex and T Wave

the completion of ventricle depolarization

T Wave

this is caused by the repolarization of ventricles (resting of ventricles)

Video Review!!

review the video notes in my onenote page about the cardiac cycle

Types of Blood Vessels

arteries, veins, capillaries

Branching out of the Blood Vessels

• Arteries are huge and carry blood away from the heart to the body

• the arteries pass the blood onto smaller arterioles

• the arterioles pass the blood to even smaller capillaries

• in the tiny capillaries, the walls of the capillaries are so thin that gases (O2 and CO2) in the blood can be exchanged with tissues in these capillaries

• after dropping off O2 and picking up CO2, the capillaries collect blood into larger venules

• the venules collect into larger veins which return the blood to the heart

Structural Differences between Arteries and Veins (and Capillaries i guess….)

Capillaries only have 1 layer of cells surrounding them, allowing for easy exchange of gases

Arteries and Veins are both bigger than capillaries and both have 3 layers: (superficial to deep)

• Tunica Externa (or Tunica Adventitia): fibrous connective tissue to protect and support the blood vessel

• Tunica Media: thicker layer of muscle

  • Arteries have much thicker layers of tunica media than veins, letting them retain their circle shape much better than veins

• Tunica Intima: slippery, thin layer

Arteries are more flexible than veins because they receive blood from the heart at high pressures

Veins have thinner walls and receive blood from tissues in low pressures

3 Ways Veins Maintain Blood Flow under Low Pressues

• Muscular Pumping: as muscles contract, blood is squeezed through the veins

• Respiratory Pumping: the expansion of the chest during inhalation causes blood in the veins to move

• Valves: larger veins have valves inside to prevent backflow of blood

Capillary Structure

Capillaries contain of two portions:

• Shunt: a shortcut from the artery to the vein (the highlighted portion)

• True Capillaries: all the tiny portions that exchange gases with the tissues

Between the arterioles and the shunt are sphincters which can restrict the flow of blood to the tissues when blood is needed elsewhere (like if you are in fight or flight mode)

Pulse

expansion of the heart wall

Pulse = rate of contraction of the left ventricle

Normal Rate: 60-100 bpm

Pulse Measurement

Commonly at radial (near wrist), brachial (near elbow), or carotid (near neck) arteries

use index and middle finger for pulse not thumb (bc you can feel your thumb’s pulse and it might mess up the count)

Normal Systolic and Diastolic Values

Systolic: max 120

Diastolic: max 80

Hypertension

above 140/90

tension can cause tears in the blood vessels which will accumulate cells that can block blood flow in the heart (coronary) or brain (stroke).

symptoms: (although sometimes not visible) headache, dizziness, shortness of breath, feeling of pulsations in the head or neck

caused by: high sodium intake, arteriosclerosis, atherosclerosis, obesity, renal problems

results in: damage to arterial walls (aneurysm) , damage to coronary arteries, left ventricular hypertrophy, heart failure, stroke

Medications for Hypertension

Angiotensin - Converting Enzyme Inhibitors/Blockers: angiotensin-2 is a hormone that narrows blood vessels. this treatment inhibits this hormone, which lets blood vessels not be constricted, reducing blood pressure

Calcium Channel Blockers: this keeps calcium from coming into the muscle cells of your heart, allowing blood vessels to relax, lowering your BP

Diuretics: increases urine output, lowers blood volume

Hypotension

Less that 90/60

Symptoms: lightheadedness, dizzyness, fainting (syncope), angina (pressure/pain in heart), shock

Caused by: change my body position, decreased blood volume, medications

Results in: low blood volume to the organs, brain/heart/kidney damage

Blood Pressure and Arterioles

BP dramatically decreases in the arterioles

Perfusion

french verb perfuser: pour over or through

passage of blood through circulatory system to an organ or tissue

measured at the rate which blood is delivered to tissue

Factors that Affect Blood Pressure

• blood volume

• cardiac output

• peripheral resistance

Blood Volume Factor

greater blood volume → more fluid to press on the walls of the arteries → resulting in greater pressure

sweating/blood loss/dehydration: temporarily reduces blood volume/pressure

high sodium/salt diet: increases water retention → increases blood volume therefore increase in BP

Stroke Volume

volume of blood ejected from each ventricular contraction

average SV for a male: 70mL

Cardiac Output

volume of blood ejected per minute

Cardiac Output: SV x BPM = mL/BPM

Sympathetic and Parasympathetic NS

Sympathetic - increases HR, cardiac output, and SV

Parasympathetic - decreases HR, cardiac output, and SV

Sympathetic NS and Systolic BP

SNS controls proprioceptors (stretch/tension) in joints or muscles send signals which cause an inc in HR

causes an increase in systolic BP ONLY, not diastolic

also causes vasodilation of blood vessels in the muscles and the skin to increase blood flow

Cardiac Hypertrophy

increase in heart muscle and enlargement of the muscle fibers

benefits of exercise: increases SV and allows the heart to pump more slowly

Trained Athletes: 60% greater ventricular mass than normal people

Hypertrophic Cardiomyopathy

enlargement of the muscle fibers → ventricle walls thicken → blocks blood flow out of the ventricle

can be inherited, develop (due to high BP), or caused by a disease (thyroid, diabetes)

Peripheral Resistance

• blood vessel diameter

• blood viscosity

• vessel elasticity

Blood Vessel Diameter

larger diameter = less pressure

vasoconstriction vs vasodilation

regulated by sympathetic nerve fibers

Blood Viscosity

thickness of the blood

the greater the viscosity, the more difficult to get the blood moving

greater pressure needed to pump same amount of viscous blood

Arteriosclerosis

“hardening of the arteries”

decreases elasticity of the arteries

Atherosclerosis

lipid (plaque) deposits on the artery walls producing blockages

Stages of Diastole

atrial contraction - ventricles fill with blood

AV valves close - making the first heartbeat sound “lub”

Stages of Systole

Isovolumetric Contraction - ventricles are contracting with all the valves closed

Ejection Phase - pressure in the ventricles builds up until the semilunar valves open and blood is released into the blood vessels. blood is also refilling the atria during this phase.

Semilunar valves close - making the second heartbeat sound “dub”

isovolumetric relaxation - ventricles relax with all valves closed

Stroke Volume Changes

Exercise: additional blood return from muscles brings in more volume to the ventricles

Rapid Blood Loss: decreases blood returning to the heart

Heart Rate Changes

Stress: sympathetic and parasympathetic NS causes rate to increase or decrease

Hormones: epinephrine and thyroxine increase HR

ions: electrolyte imbalances affect the ability for the heart to contract

physical factors: age, body temperature, and overall health