Cardiac Unit-Human Physiology

Front 1

Mechanism of Cardiac Contraction

Back 1

Heart contains sarcoplasmic reticulum which holds Calcium.
Heart contains calcium induced calcium channels
Rely on calcium in the environment to realease calcium into cardiac muscle
S.R. is the bulk of Calcium source, but not the only source.

Front 2

T-Tubules in heart contain ____ Channels

Back 2

Voltage-Regulated Calcium channels which open at +20mV

Front 3

Sarcoplasmic Reticulum of Heart contains ____ Channels

Back 3

Ligand Regulated Calcium Channels.
Ligand=Calcium!!!

Front 4

Mechanism of Cardiac Relaxation

Back 4

Calcium is pumped back into S.R.
Calcium is pumped back into extracellular fluid.

Front 5

Why are nerves in heart?

Back 5

To control rate of contraction, but not to initiate a contraction

Front 6

Nervous system that controls contraction?

Back 6

Autonomic (Sympathetic & Parasympathetic)
No nervous connections to contractile cells at all. Connections only in autorhythmic cells in the S.A. and A.V. nodes

Front 7

Sympathetic pathway in cardiac conduction

Back 7

Sympathetics-->Norepinephrine (At SA & AV nodes)-->NorE binds to Beta-Receptors-->cAMP (Bind to gates internally)

Front 8

Beta Receptors

Back 8

G-Protein Covered Receptors.
If ligand from GPCR binds, then it activates enzyme that results in phosphoryation to initiate cAMP

Front 9

cAMP-->

Back 9

If Channels (Na/K) open wider.
Calcium Channels open wider.

Front 10

Effects of Norepinephrine on heart

Back 10

1) Sympathetics: increase in conractile cell due to more calcium release from S.R.
(Heart rate up, contractions stronger)
2) Contraction strength is increased
-more cross bridging occurs, power increase
-Contractile Phase, Shorter
-Relaxation Phase, Longer (more blood fill)

Front 11

Parasympathetic Pathway in Cardiac Conduction

Back 11

Parasympathetics--> Acetycholine-->Muscarinic Receptors (GPCR)-->Inositol Triphosphate (IP3)

Front 12

Effects of IP3 (inositol triphosphate)

Back 12

Calcium channels depolarize at lower voltage (take longer to open)
Potassium channels open for longer period of time (depolarize longer)

Front 13

Absolute Autorhythmic Rate
Average Rate

Back 13

100bpm, 72bpm
Parasympathetics (ACh) always working more at rest.

Front 14

Norepinephrine causes a shorter contractile phase-->

Back 14

Allows more time for the SR to suck out more calcium for the next contraction

Front 15

Starlings Law of the Heart

Back 15

Fill Time (UP)--> Blood Volume Before Contraction (UP)-->Cardiac Stretch (UP)--> Contractile Strength (UP)

Front 16

Key for stronger contraction

Back 16

Sarcoplasmic Reticulum.
When cell is stretched, more Calcium channels are opened in SR causing increase in calcium released out of SR

Front 17

Right Atria

Back 17

Superior Vena Cava
Inferior Vena Cava
Pulmonary Trunk

Front 18

Left Atria

Back 18

Pulmonary Veins
Aorta

Front 19

Heart Valves

Back 19

Atrioventricular Valve
Semilunar Valve

Front 20

A-V Valves

Back 20

Open when chambers are filling
Close during contraction
Right A-V Valve (Tricuspid)
Left A-V Valve (Bicuspid, Mitral)
-MVP due to higher pressure on left side of heart

Front 21

Semilunar Valves

Back 21

Open during contraction, close during relaxation
Right-Pulmonary Valve
Left-Aortic Valve

Front 22

Cardiac Cycle (how many/name stages)

Back 22

2 stage cycle of contraction and relaxation
Systole and Diastole

Front 23

Systole

Back 23

Systolic BP
Pressure in heart when contracted.
BP in heart is a maximum at systole

Front 24

Diastole

Back 24

Diastolic Pressue
Pressure in heart during relaxation
Average pressure is dependent on age
High residual pressure will tear at linings of arteries and overwork the heart

Front 25

High Blood Pressure

Back 25

145/90 (over 4 years)
As age increases, BP will increase, vessels lose elasticity over time.
(145/90 for a 70+ year old is perfect)

Front 26

Detailed Cardiac Cycle Components

Back 26

Atrial Systole
Ventricular Systole
-Isovolumetric Contraction
-Ejection Phase (Ventricular Ejection)
-Ventricular Diastole

Front 27

Atrial Systole

Back 27

Atria squeeze blood into ventricles
Results in end diastolic volume

Front 28

Ventricular Systole (isovolumetric contraction)

Back 28

Rise in pressure closes the A-V valves.
'First Heart Sound' (A-V Valves Close)
Can't pump into arteries until pressure is greater than residual pressure in arteries.

Front 29

Residual Pressure (Of arteries closest to heart)

Back 29

Aorta-80mmHg
Pulmonary Trunk-10mmHg

Front 30

Ejection Phase (Ventricular Ejection)

Back 30

Aorta-Greater than 80mmHg
Pulmonary Trunk-Greater than 10mmHg
Semilunar Valves Open
Blood contracted into arteries
Ejected blood is about 54% of End Diastolic Volume (Ejection Fraction)
End Systolic Volume=EDV-SV

Front 31

Ventricular Diastole

Back 31

Muscular Relaxation
A-V Valves Open
Semilunar Valves close, 'Second Heart Sound'

Front 32

Cardiac Output (affected by)

Back 32

Heart Rate
Stroke Volume
HRxSV=CO(mL/min)
72bpm X 70mL = 5liters

Front 33

Parasympathetics on Cardiac Output

Back 33

Parasympathetics-->ACh-->CO (down)

Front 34

Sympathetics on Cardiac Output

Back 34

Sympathetics-->NorE-->HR(UP) -->SV (UP)-->CO(Way Up)

Front 35

Max Norepinephrine

Back 35

90% Ejection Fracture
HR=220-age (MaxHR)

Front 36

Min Stroke Volume

Back 36

54% Ejection Fracture (at rest)

Front 37

Min Heart Rate

Back 37

Requirements of what body needs minimally to stay conscious

Front 38

Ejection Fracture depends on?

Back 38

Age
Physical Fitness