Unit 1 Neuro: Cardiovascular and Respiratory System - IFS 2 Study Material

what kind of system is the heart

closed circulatory system

function of cardiovascular system

- transport of material (gases, nutrients, water, hormones, waste)

- pathogen defense (antibodies and WBC)

- Temperature control (vasodilation and vasoconstriction)

where is the heart located

central aspect of the thoracic cavity

apex of the heart

lower point of the heart that's positioned toward the left

base of the heart

superior part of heart positioned behind the sternum

endocardium

inner layer of the heart

myocardium

middle layer of cardiac muscle in the heart

epicardium

external layer of the heart

pericardium

tough membranous sac filled with pericardial fluid encasing and lubricating the heart

what are the 4 chambers of the heart

right atrium, right ventricle, left atrium, left ventricle

what is the septum in the heart

divides the heart into right and left halves

atrioventricular valves

Valves located between the atrial and ventricular chambers on each side of the heart

tricuspid valve

valve between the right atrium and the right ventricle

bicuspid valve (mitral)

valve between the left atrium and the left ventricle

semilunar valves

between ventricles and arteries

aortic valve

The semilunar valve separating the aorta from the left ventricle that prevents blood from flowing back into the left ventricle.

pulmonary valve

valve positioned between the right ventricle and the pulmonary artery

what causes the first heart sound

atrioventricular valves close

what causes the second heart sound

semilunar valves close

Blood flow process

- superior and inferior vena

- right atrium

- tricuspid valve

- right ventricle

- pulmonary valve

- lungs

- pulmonary veins

- left atrium

- mitral (bicuspid valve)

- left ventricle

- aortic valve

- systemic arteries

- capillaries

- veins

Properties of contractile heart cells

- straited fibers organized in sarcomeres

- branched

- single nucleus

- attached by intercalated discs to create specialized junctions

properties of autorhythmic cells

- generate electrical signal for contraction

- smaller and fewer contractile fibers

- No organized sarcomeres

how much of the heart cells are contractile and autorhythmic

99% contractile

1% autorhythmic

what does the heart being myogenic mean

signal for contraction originates from the heart itself

why is the heart myogenic

the autorhythmic cells create spontaneous action potential which are connected to contractile cells to produce a contraction

what does a pacemaker potential mean in autorhythmic cells

unstable membrane potential that spontaneously drift towards less negative values

what causes the resting membrane potential of pacemaker tissue to drive from -60 to -40 mv (pacemaker potential)

influx of Na+

what causes depolarization to occur in authorhythmic cells

closure of Na2+ channels and openings of Ca2+ channels resulting in Ca2+ influx

what causes repolarization of authorhythmic cells

closure of Ca2+ channels and opening of K+ channel resulting in K+ outflux

what causes depolarization of myocardial contractile cells

Na+ entry

what happens after depolarization of myocardial contractile cells

very brief initial repolarization due to closure of Na+ channels

what occurs after the initial repolarization in myocardial contractile cells

plateau phase

decreased K+ permeability and increased Ca2+ entry to cell

what occurs after plateau phase in myocardial contractile cells

rapid repolarization caused by Ca2+ channels closing and K+ permeability increase

what are the similarities between myocardial contractile cells and autorhythmic cells electrical signaling

Ca2+ and Na+ is required for each

in autorhythmic cells CA2+ influx causes depolarization

in contractile cells Ca2+ is responsible for plateau phase after Na+ influx (depolarization)

what are the differences in resting membrane potential for autorhythmic and contractile cells

autorhythmic resting membrane potential is more positive (-60 mv) compared to contractile cells (-90 mv)

what is the cardiac muscle contraction process

- action potential begins with pacemaker cells

- voltage gated Ca2+ channels open

- Ryanodine receptors open in sarcoplasmic reticulum

- Calcium binds to troponin

- crossbridge cycle

what is the relaxation process of cardiac muscle contraction

- calcium removed from cytoplasm beck to sarcoplasmic reticulum with Ca2+ and ATPase

- Calcium removed from cell through Na+ Ca2+ exchanger in cell membrane

what affects the amount of force generated in cardiac muscle contraction

- how much calcium binds (number of crossbridge)

- sarcomere length

SA node

the pacemaker of the heart

first point of depolarization

where is the SA node located

superior and posterior walls of the right atrium, near the opening of the superior vena cava and deep to epicardium

what is the process of electrical conduction in the heart

- autorhythmic cells in the SA node depolarize

- send the signal via an internodal pathway to the AV node

- depolarization moves through ventricular conducting system to the apex of the heart

- depolarization wave spreads upward from the apex

where is the AV node located

floor of the right atrium

why is the SA node the pacemaker of the hear compared to the AV node or purkinje fibers

the SA node discharge rate is 60-100 times/min which is faster then the AV ode (40-60 times/min) and purkinje fibers (15-40 times/min)

ECG/EKG definition

sum of multiple action potentials taking place in many heart cells

wave in ECG

parts of the trace that go above or below the baseline

segment in ECG

section of the baseline between 2 waves

interval in ECG

combination of waves and segments

what occurs during the P wave

atrial depolarization (contraction)

what occurs during the QRS complex

ventricular depolarization (contraction)

what occurs during the T wave

ventricular repolarization (diastole)

what occurs during the PQ segment

conduction through the AV node

what occurs during PR interval

time from the start of atrial depolarization to the start of ventricular depolarization

what occurs during ST segment

isometric line before ventricular repolarization

what does contraction do to pressure

increases

what does relaxation do to pressure

decreases

what occurs during late diastole in the cardiac cycle

both chambers relaxed, ventricles fill passively (70%)(semilunar valve closed, AV valve open)

what is the cardiac cycle process

- Late diastole:

- Atrial systole

- isovolumic ventricular contraction

- ventricular ejection

- isovolumic ventricular relaxation

what occurs during atrial systole during cardiac cycle

atrial contraction forces additional 30% of blood to ventricles (semilunar valves closed AV valves open)

what occurs during isovolumic ventricular contraction

1st phase of ventricular contraction (AV valve closed=first heart sound)

End diastolic volume here

what occurs during ventricular ejection

ventricular pressure rises resulting in opening of semilunar valves and blood ejecting

amount is stroke volume

what occurs during isovolumic ventricular relaxation

- ventricles relax

- blood flows back into semilunar valves to close them (second heart sound)

- End systolic volume is here

end diastolic volume

volume of blood in ventricles after diastole (about 135 ml)

stroke volume

the amount of blood ejected out of one ventricle during systole (end diastolic- end systolic) (70 ml)

end systolic volume

volume of blood in ventricle after ventricular systole (135-70= 65 ml)

ejection fraction

percentage of blood that leaves the ventricle with each contraction (Stroke volume/ end diastolic volume) x 100 (50-70%)

cardiac output

volume of blood pumped by each ventricle per minute 5-6 L/min

what factors influence stroke volume

preload, contractility, afterload

what determines contractability

length of muscle fiber

amount of calcium

volume of blood at beginning

as stretch increases so does contraction

what is preload

the degree of stretch on myocardium before contraction (depends on end diastolic volume)

what determines end diastolic volume

venous return

what contributes to venous return

skeletal muscle pump

respiratory pump

sympathetic innervation of veins

what is afterload

the resistance against which blood is expelled from the ventricles

what does parasympathetic innervation do to heart rate

decreased heart rate through acetylcholine release on muscarinic receptor

what does acetylcholine binding to muscarinic receptors do

increases K+ permeability and decreases calcium influx which reduces rate of depolarization

what does sympathetic innervation do to heart rate

increase heart rate and contractibility through release of epinephrine and norepinephrine on beta receptors

what does norepinephrine binding to beta receptors do

increases sodium ad calcium permeability to increase depolarization rate

what contributes to resistance of flow

diameter

length

viscoscity

what layers do arteries have

endothelium

elastic tissue

smooth muscle

fibrous tissue

what layers do arterioles have

endothelium

smooth muscle

what layers do capillaties have

endothelium

what layers do venules have

endothelium and fibrous tissue

what layers do veins have

endothelium

smooth muscle

elastic tissue

fibrous tissue

how does blood flow

down a pressure gradient (areas of high pressure to low pressure)

what increases resistance to blood flow (slows flow)

increase in length

increase in viscosity

decrease in radius

what increases flow of blood

increased pressure gradient

decreased length

decreased viscosity

increased radius

what happens with decreased red blood cells in blood

viscosity decreases so resistance decreases and blood flow is increased

pulse pressure

difference between systolic and diastolic blood pressure

mean arterial pressure

value representing the driving pressure of the heart

mean arterial pressure formula

diastolic pressure + 1/3 pulse pressure

why is mean arterial pressure important

vital organs need a minimum MAP of 60 mmHg

what influences mean arterial pressure

blood volume

cardiac output

resistance to blood flow

distribution of blood between arteries and veins

what is the response for increased blood volume and pressure

vasodilation and decreased cardiac output

fluid excretion by kidneys

what artery is used for taking blood pressure

brachial artery

how does local control regulate blood flow

- precapillary sphincters can open or close capillaries depending on need

- paracrine control can increase blood flow

active hyperemia

vasodilators are released in reaction to increased tissue metabolism

reactive hyperemia

occurs in response to decreased blood flow by dilatating arterioles and removing occlusion

what hormones regulate blood flow

atrial natriuretic peptide (vasodilator)

angiotension II (vasoconstrictor)

vasopressin (antidiuretic hormone) (Vasoconstrictor)

how do neurotransmitters regulate blood flow

tonic control

norepinephrine cause vasoconstriction

where is the central cardiovascular control center

medulla oblongata

where is the peripheral cardiovascular control center

carotid and aortic baroreceptor