Transcript Heart Rate cycle

Dr. Jagdish Kaur
P.G.G.C., Sector 11,
Chandigarh
Humans
have a closed circulatory system,
typical of all vertebrates, in which blood is
confined to vessels and is distinct from the
interstitial fluid.
The
heart pumps blood into large vessels
that branch into smaller ones leading into the organs.
Materials
are exchanged by diffusion between the
blood and the interstitial fluid bathing the cells.
Three
Major Elements –
Heart, Blood Vessels, &
Blood
1.
The Heart- cardiac
muscle tissue
highly interconnected cells
four chambers
Right atrium
Right ventricle
Left atrium
Left ventricle

Superior
Vena Cava
Right Atrium
Right Ventricle
Lungs
Pulmonary Vein
Left auricle
Bicuspid Valve
Left Ventricle
Aorta
To the bodies organs & cells
Pulmonary
circuit
The
blood pathway
between the right side of
the heart, to the lungs,
and back to the left side of
the heart.
Systemic
The
circuit
pathway between the
left and right sides of the
heart.
2. Blood Vessels -A network of tubes
Arteriesarterioles
move away from the heart
Elastic Fibers
Circular Smooth Muscle

Capillaries
– where gas exchange takes place.
One cell thick
Serves the Respiratory System
VeinsVenules
moves towards the heart
Skeletal Muscles contract to force blood back from legs
One way values
When they break - varicose veins form
3. The Blood
A.
Plasma
Liquid portion of the blood.
Contains clotting factors,
hormones, antibodies,
dissolved gases, nutrients and
waste
The
Blood
B. Erythrocytes - Red
Blood Cells
Carry
hemoglobin and
oxygen. Do not have a
nucleus and live only
about 120 days.
Can
not repair
themselves.
The
Blood
C. Leukocytes – White Blood
cells
Fight
infection and are
formed in the bone marrow
Five
types – neutrophils,
lymphocytes, eosinophils,
basophils, and monocytes.
 Generating
blood pressure
 Routing blood

Heart separates pulmonary and systemic
circulations
 Ensuring

one-way blood flow
Heart valves ensure one-way flow
 Regulating

blood supply
Changes in contraction rate and force match
blood delivery to changing metabolic needs
 Three



layers of tissue
Epicardium: This serous membrane of smooth outer
surface of heart
Myocardium: Middle layer composed of cardiac
muscle cell and responsibility for heart contracting
Endocardium: Smooth inner surface of heart
chambers
Atrioventricular
Tricuspid
Bicuspid
or mitral
Semilunar
Aortic
Pulmonary
Prevent
blood from flowing back
 Resting
membrane potential present
 Action potentials


Rapid depolarization followed by rapid, partial early
repolarization. Prolonged period of slow repolarization which
is plateau phase and a rapid final repolarization phase
Voltage-gated channels
 Absolute:
Cardiac muscle cell completely
insensitive to further stimulation
 Relative: Cell exhibits reduced sensitivity to
additional stimulation
 Long refractory period prevents tetanic
contractions
Action potentials through myocardium
during cardiac cycle produces electric
currents than can be measured
Pattern
P wave
Atria depolarization
QRS complex
Ventricle depolarization
Atria repolarization
T wave:
Ventricle repolarization
 Tachycardia:
Heart rate in excess of 100bpm
 Bradycardia: Heart rate less than 60 bpm
 Sinus arrhythmia: Heart rate varies 5% during
respiratory cycle and up to 30% during deep
respiration
 Premature atrial contractions: Occasional
shortened intervals between one contraction
and succeeding, frequently occurs in healthy
people
 Heart
is two pumps that work together, right
and left half
 Repetitive contraction (systole) and
relaxation (diastole) of heart chambers
 Blood moves through circulatory system from
areas of higher to lower pressure.

Contraction of heart produces the pressure
 First

heart sound or “lubb”
Atrioventricular valves and surrounding fluid vibrations as
valves close at beginning of ventricular systole
 Second

Results from closure of aortic and pulmonary semilunar
valves at beginning of ventricular diastole, lasts longer
 Third

heart sound or “dupp”
heart sound (occasional)
Caused by turbulent blood flow into ventricles and detected
near end of first one-third of diastole
 Average
blood pressure in aorta
 MAP=CO x PR
CO is amount of blood pumped by heart per minute

CO=SV x HR
 SV: Stroke volume of blood pumped during each heart beat
 HR: Heart rate or number of times heart beats per minute
Cardiac reserve: Difference between CO at rest and maximum
CO



PR is total resistance against which blood must be
pumped

Intrinsic regulation: Results from normal functional
characteristics, not on neural or hormonal regulation


Starling’s law of the heart
Extrinsic regulation: Involves neural and hormonal
control
 Parasympathetic stimulation
 Supplied by vagus nerve, decreases heart rate,
acetylcholine secreted
 Sympathetic stimulation
 Supplied by cardiac nerves, increases heart
rate and force of contraction, epinephrine and
norepinephrine released
 Effect

Baroreceptors monitor blood pressure
 Effect

of extracellular ion concentration
Increase or decrease in extracellular K+ decreases
heart rate
 Effect

of pH, carbon dioxide, oxygen
Chemoreceptors monitor
 Effect

of blood pressure
of body temperature
Heart rate increases when body temperature
increases, heart rate decreases when body
temperature decreases
 Gradual
changes in heart function, minor
under resting condition, more significant
during exercise
 Hypertrophy of left ventricle
 Maximum heart rate decreases
 Increased tendency for valves to function
abnormally and arrhythmias to occur
 Increased oxygen consumption required to
pump same amount of blood
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