Physiology Chapter 14 (EXAM 3)

Dr. KOKA

How is the heart a pump

atria receives blood returning to heart

ventricles pump blood out

septum

divides left and right halves

what do blood vessels consist of

veins arteries and capillaires

pulmonary and systemic circulation

portal system joins two capillary beds in series

blood

cells and plasma

transport of material

gases, nutrients, waste, communication

defense against pathogens and temperature homeostasis

the heart is mostly composed of ___________

myocardium

what are the twos sets of heart valves

atrioventricular and semilunar

atrioventricular valves

between atria and ventricles

tricuspid and bicuspid/mitral valve

where is the tricuspid valve located

on the right side

where is the bicuspid/mitral valve located

on the left side

Semilunar valves

between ventricles and arteries

aortic valve

pulmonary valve

ventricular contraction

the AV valves remain closed to prevent backward blood flow

ventricular relaxation

the SL valves prevent blood that has entered the arteries from flowing back into the ventricles

contractile cells

striated fibers organized into sarcomeres

autorhythmic cells (pacemaker)

signal for contraction

smaller and fewer contractile fibers compared to contractile cells

do not have organized sarcomeres

myocardial muscle cells

branched, single nucleus, connected to each other by intercalated disks

intercalated disks

contains desmosomes that transfer force from cell to cell

gap junctions that allow electrical signals to pass rapidly from cell to cell

cardiac vs skeletal muscle

smaller

single nucleus

branched

ic disks

t tubules are larger and branched

sarcoplasmic reticulum is smaller

mitochondria takes 1/3 of volume

muscle twitch in diff types of muscle

myocardial autorrhythmic cells

unstable membrane potential (pacemaker potential)

depolarization due to CA2+ channels opening

Myocardial contractile cells

depolarization due to Na+ entry

Repolarization due to K+ exit

long AP (plateau) due to Ca2+ entry in the cell prevents tetanus

AP of cardiac contractile cell

0. Na+ channels open

1. Na+ channels close

2. Ca2+ channels open; fast K+ channels close

3. Ca2+ channels close; slow K+ channels open

4. resting potential

tetanus

sustained contraction

the ____ myocardial action potential helps prevent tetanus

longer

importance of preventing tetanus

heart musckles must relax between contractions so the ventricles can fill with blood

relaxation

calcium removed from cytoplasm: back into the SR with Ca2+ ATPase and out of the cell through Na+ - Ca2+ exchanger

force generated is ___________ to the number of active cross bridges

Proportional

(determined by how much calcium is bound to troponin)

sarcomere length affects force of ____________

contraction

Cardiac Muscle AP

voltage-gated L-type Ca2+ channels int the cell membrane (extracellular calcium contributes 10%)

ryanodine receptors open in the SR

calcium binds to troponin

cross-bridge cycle as in skeletal muscle

extracellular coupling in cardiac muscle

1. AP enters from adjacent cell

2. Voltage-gated Ca2+ channels open. Ca2+ enters the cell

3. Ca2+ induces Ca2+ release through ryanodine receptor channels (RyR)

4. local release causes Ca2+ spark

5. Summed Ca2+ sparks create a Ca2+ signal

6. Ca2+ ions bind to troponin to initiate contraction

7. relaxation occurs when Ca2+ unbinds from troponin

8. Ca2+ is pumped back into SR for storage

9. Ca2+ is exchanged with Na+ by the NCX antiporter

   1. Na+ gradient is maintained ny the Na+-K+-ATPase

conducting system of heart steps

1. sa node depolarizes

2. electrical activity goes rapidly to AV node via internodal path

3. depolarization moves more slowly across atria. conduction slows through AV

4. depolarization moves rapidly through ventricular conducting system to apex of heart

5. depolarization wave spreads upward from apex

three waves

P, QRS, T

P wave

depolarization of the atria

QRS complex

wave of ventricular depolarization

T wave

repolarization of the ventricle

heart rate

time between two P waves or two Q waves

rhythm

regular

waves analysis

presence and shape

segment length

constant

ECG and electrical events

1. P wave (atrial depolarization)

2. P-Q/P-R segment (conduction through AV node/bundle

3. Q wave (depolarization of the septum

4. r wave (atrial repolarization)

5. s wave (ventricle contraction)

6. s-t segment (

7. t wave (ventricular repolarization

8. qrs

normal ECG

third degree block

missing T, relaxation is missing

atrial fibrillation

contracting more, depolarize more

ventricular fibrillation

do not have the qrst

diastole

cardiac muscle relaxes

systole

cardiac muscle contracts

beginning of cycle

heart at rest

mechanical events if cardiac cycle

1. late diastole: both sets chambers and ventricles are relaxed and fill passively (end diastolic volume)

2. atrial systole: first contraction; atrial contraction forces a small amount of additional blood into ventricles

3. isovolumic ventricular contraction: first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves

4. ventricular ejection: as ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected (end systolic volume)

   1. Isovolumic ventricular relaxation: ventricles relax, pressure in ventricles fall. blood flows back into cusps of semilunar valves and snaps them closed

first heart sound, “lub”

vibration following closure of the AV valves

second heart sound, “dub”

vibrations created by closing of semilunar valve

auscultation

listening to the heart through chest wall using stethoscope

driving pressure is created by…

ventricles

if blood vessels dilate, blood pressure ________

decreases

if blood vessels constrict, blood pressure ________

increases

flow through a tube is inversely proportional to resistance

1/R

if resistance ________, flow decreases

increases

if resistance ________, flow increases

decreases

Resistance is proportional to length of tube

resistance increases as length increases; vice versa

resistance is proportional to viscosity

resistance increases as viscosity increases; vice versa

resistance is inversely proportional to tube radius to the 4th power

resistance decreases as radius increases; vice versa

vasoconstriction

decrease in blood vessel diameter/radius and decreases blood flow

vasodilation

increase in blood vessel diameter/radius and increases blood flow

flow of blood is

directly proportional to pressure gradient

inversely proportional to resistance to flow

flow rate = flow rate

the volume of blood thats passes a given point per unit time

velocity of flow

distance a fixed volume of blood travels in a given period of tiem

end diastolic volume

volume of blood present in ventricle at the end of diastole

end systolic volume

voluem of blood in the ventricle at the end of systolic ejection phase

stroke volume

amount of blood pumped by one ventricle during contraction

volume before contraction - volume after contraction

EDV-ESV

average - 70 mL

cardiac output

volume of blood pumped by one ventricle in a given period of time

CO=HRxSV

average is 5L/min

ejection fraction

percentage of EDV ejected with one contraction

average is 52%

Left ventricle fractional shortening

the fraction the left ventricle shortens during a cardiac cycle

average= 30-45%

Preload

force load acting to stretch the LV fibers at the end of diastole

amount of blood returning to heart

afterload

the force that must generate in order to overcome vascular resistance and eject blood out of the left ventricle

combined load of EDV and arterial resistance during ventricular contraction

force of contraction is affected by:

length of muscle fiber (dependent on volume of blood)

contractility of heart

as stretch of the ventricular wall increases, so does stroke volume

preload is the degree of myocardial stretch before contraction

chemical that affects contractility

inotropic agent

chemicals that have positive inotropic effects

epinephrine, norepinephrine, and digitalis

chemicals with negative inotropic effects ________ contractility

decrease

frank-starling law of heart

SV increases as EDV increases

increases the volume of blood in the ventricles

EDV is determined by what?

venous return

venous return is affected by

skeletal muscle pump

respiratory pump

sympathetic innervation of veins

parasympathetic innervation causes

lower rate of depolarization in autorhythmic cells

sympathetic innervation and epinephrine causes

higher rate of depolarization in autorhythmic cells