Heart Anatomy and Physiology Flashcards
T or F
Blood pressure is highest in the aorta
T
The steepest drop in blood pressure happens in the ….
arterioles
The source of the pressure in the arteries comes from their proximity to the …
heart
Arterial blood pressure is determined by what two factors?
- Elasticity of the arteries close to the heart
- Volume of blood forced into the arteries at any time
T or F
Blood pressure near the heart is pulsatile
T
What is systolic pressure?
Pressure exerted in the aorta during ventricular contraction
What is a pulse?
Rhythmical throbbing of the arteries caused by the heart propelling blood through them
What is the lowest lvl of aortic pressure when the heart is at rest called?
Diastolic pressure
What is pulse pressure?
The difference between diastolic and systolic pressure
T or F
The heart spends more time in systole than diastole
F
It spends more time in diastole
Mean arterial pressure is calculated by adding … to …
pulse pressure to 1/3 pulse pressure
What two types of controls can regulate blood pressure in the short-term?
Neural and hormonal controls
What type of control can regulate blood pressure in the long-term?
renal controls
What factors increase peripheral resistance?
- Increased blood viscosity (doesn’t change in healthy individuals)
- Increased blood vessel length (can’t be changed)
- Decreased diameter of blood vessels
What factors increase cardiac output?
- Increased stroke volume
- Increased heart rate
What two factors increase mean arterial pressure (MAP)?
- Increased cardiac output
- Increased peripheral resistance
T or F
Blood viscosity does not change in a healthy individual
T
What type of receptors are baroreceptors?
mechanoreceptors
The medullary cardiovascular centre can be subdivided into what two sections?
cardiac and vasomotor centre
What is the pericardium?
is a
double-walled sac containing
the heart and the roots of the
great vessels.
What is the purpose of the pericardium?
- maintains the hearts position
- prevents heart from overfilling
The pericardial cavity is between the 2 …
serouslayers
The pericardium consists of what two serous layers?
- parietal layer of serous pericardium
- visceral layer of serous pericardium
The … arteries are the arterial blood vessels which transport oxygenated blood to the heart muscle.
coronary
T or F
The right ventricle is thicker than the left
F
T or F
There is no connection
between any of the heart
chambers other than via the heart valves.
T
Why does the left side of the heart have a bicuspid valve?
A bicuspid valve works better on the high pressure side
because with only two sides to the valve, the muscles and ligaments are able to
spring back from the high pressure on the left side of the heart.
The papillary muscles attach to the cusps of the atrioventricular valves via the chordae tendineae and contract to prevent … or … of these valves during … contraction.
nversion or prolapse
ventricular
The semilunar valves permit blood to be …., but prevent ….
forced into the arteries
backflow from
the arteries into the ventricles
T or F
Semilunar valves don’t have papillary muscles
T
Left Heart = … Circulation (high pressure)
Right Heart = … Circulation (low pressure)
Systemic
Pulmonary
T or F
In the pulmonary circulation all the blood flows only through the lungs.
T
T or F
In systemic circulation O2 is low in the arteries and high in the veins
F
T or F
In pulmonary circulation O2 is low in the arteries and high in the veins
T
What is the role of the venules?
to collect blood from the capillaries
Which component of the cardiovascular system am I?
I control resistance to flow, thus, the distribution of
flow to different organs and tissues.
arterioles
Define End diastolic volume (EDV)
Volume of blood in the ventricle IMMEDIATELY before contraction
Define End systolic volume (ESV)
Volume of blood in the ventricle IMMEDIATELY after contraction
What is the formula for stroke volume?
Stroke volume = EDV - ESV
Define stroke volume
Volume of blood pumped out of each ventricle during a single contraction
Define cardiac output
- Volume of blood pumped by each ventricle per minute
What does cardiac output indicate?
blood flow through peripheral tissues
What is the formula for cardiac output?
Cardiac output (CO) = Heart rate (beats/min) x stroke volume (ml/beat)
Define preload?
Volume of blood received by the heart/amount of stretch during diastole
Define afterload?
Pressure or resistance the heart has overcome to eject blood
T or F
More stretch of the cardiac muscle = greater force of the cardiac contraction
T
T or F
Primary determinant of preload = left ventricular end diastolic volume (EDV)
T
T or F
Greater the ESV, greater the cardiac contraction
F
EDV
WHat is the Main determinant of afterload?
resistance in the blood vessels
Define venous return?
The volume of blood returning back to the heart each minute
T or F
Increased venous return increases EDV
T
T or F
Venous return causes heart muscle to stretch
T
T or F
As cardiac muscle stretches, the next contraction will be weaker
F
stronger
What is the Frank-Starling law of the heart?
The greater the end diastolic volume, the greater the force of
contraction during systole (within limits!). Stretching the cardiac muscle cells produces a more optimum overlap between
thick & thin filaments, leading to a stronger contraction
T or F
Parasympathetic stimulation enhances the
contractile strength of the heart
F
sympathetic
Parasympathetic nervous system does not extensively innervate the ventricles
and has minimal effect on stroke volume
T or F
Sympathetic activity doesn’t directly effect EDV
T
It effects EDV by increasing venous return
The action of …. prevents the backflow of blood when veins bring blood to the heart
venous valves
Increased stroke volume and heart rate leads to an increase in…
Cardiac output
Heart failure is defined as…
failure of the heart muscle to eject blood either due to a stiff heart (trouble filling in diastole) and/or a weak heart muscle (trouble pumping blood
during systole).
Explain sympathetic nerve activity in heart failure
Sympathetic nerve activity increases in heart failure to increase muscle
contraction and to preserve cardiac output. In the short term, this can improve
cardiac function to an extent.
In the long run, chronic overactivation of the sympathetic nervous system injures
the cardiac muscle, further reducing cardiac function contributing to heart failure.
The heart what 2 types of cells?
contractile and non-contractile
T or F
Almost all of the cardiac cells are non-contractile cardiac muscle cells
F
contractile
T or F
Pacemaker cells are non-contractile cells
T
T or F
Pacemaker cells can spontaneously depolarize without any neural input
T
Contractile cells are …% responsible for contraction
99
… cells generate action potentials that drive contractile cells
Autorhythmic/Pacemaker
Contractile cells are composed of many …
tubular myofibrils
What are myofibrils?
Myofibrils are repeating sections of sarcomeres which are contractile units with actin
and myosin.
… account for 25-35%of volume of cardiac cells
Mitochondria
What is the contractile unit of the heart?
Myofibrils
The myofibrils are made up of thick and thin …
myofilaments
What is an Intercalated disk?
A junction between cardiac cells
Match the following:
A. Desmosomes
B. Gap Junctions
C. Intercalated disk
- Tunnels connecting cells and allows the passage of ions and transmission of action potentials
- Mechanical anchors
- Junction between cardiac cells
B1, A2 C3
Sarcoplasmic reticulum: releases … in response to action potentials
calcium
The presence of calcium allows … and … to bind contracting the cells
actin and myosin
Heart cells are electronically joined
together by …
gap junctions
Gap junctions tie …. cells together to form a functional unit.
cardiac muscle
Contraction of all …. ensures effective pumping by the heart
cardiac myocytes
What am I called?
I am the the process whereby an electrical stimulus is converted to a mechanical response.
Excitation contraction coupling
How does an action potential lead to heart muscle contraction in contractile cells?
– Action potential travels down T tubules; causes sarcoplasmic reticulum (SR)
to release Ca2+
– Ca2+ leads to binding of actin and myosin filaments
leading to contraction of the cardiomyocyte.
aka excitation contraction coupling
Cardiac pacemaker cells are mainly located in
the ….
sinoatrial node
T or F
PACEMAKER CELLs generate action potentials spontaneously
T
T or F
Pacemaker cells “Resting” membrane potential is stable
F
not stable
drifts slowly toward threshold for action potential
Why do pacemaker cells undergo slow depolarisation?
gradual closure of K+ channels together with inward leak of Na+ and Ca2+
What is the sino-atrial node?
A small group of cells in right atrium near entry of superior vena cava
T or F
SA node cells have the fastest inherent rhythm
T
T or F
conducting tissues in the heart are not nerves
T
The cardiac conduction system consists of what autorhythmic cells?
– Sinoatrial node (SA node)
– Atrioventricular node (AV node)
– AV bundle
– Bundle branches
– Purkinje fibres
Spread of excitation through the heart must
meet 3 criteria:
- Each heart chamber must pump as a unit
- Atria should contract together; ventricles should
contract together - Atrial excitation & contraction must complete
before ventricular contraction
Name the primary, secondary and tertiary pacemakers of the heart
Sino-atrial node
Atrioventricular node
Purkinje fibres
Impulse is delayed at the AV node to ensure…
contraction of the atria is completed prior
to contraction of ventricles.
Important for co-ordinated contraction activity in the heart.
T or F
Cardiac cells are mechanically coupled to one another
F
electrically
The Pacemaker with the …. will drive the whole heart under normal circumstances.
fastest rhythm
What isolates the atria from the
ventricles.?
Fibrous skeleton of the heart
T or F
AV node and Bundle of His are the only electrical connection between the atria and ventricles.
T
T or F
Propogation through the AV node is fast
F
Slow
Introduces a delay, allowing contraction of the atria to finish before
the ventricles contract.
T or F
Conduction along the Bundle of His and Purkinje fibres is fast
T
Ventricular contraction ‘commences’ at the …
apex
What prevents action potentials from travelling directly from atria to ventricles?
directly
from atria to ventricles
T or F
Action potentials must travel through the AV node to reach
ventricles
T
T or F
Cardiac action potentials are different to neural/skeletal muscle action potentials
T
What are the two roles of the plateau phase?
1) Increases the length of muscle contraction for optimal chamber emptying
2) Increases the refractory period to avoid tetanus
T or F
The heart is innervated by
sympathetic and
parasympathetic neurons
T
The … nervous system can change the rate of
depolarisation in the SA node
autonomic
T or F
When is heart rate slower than SA node speed?
When the parasympathetic nervous system is in effect
How does the PNS decrease HR?
– Opens K+ channels
– Causes hyperpolarisation, so increases time to reach
threshold
– Slower depolarisation
How does the SNS increase HR?
– Opens Na+ channels
– Causes rapid depolarisation
Which hormone sympathetically stimulates the SA node?
Noradrenaline (adrenaline)
Which neurotransmitter parasympathetically stimulates the SA node?
Acetylcholine (vagus nerve)
An Electrocardiograph can detect…
electrical currents generated by heart
On an ECG what does a P wave represent?
Atrial
depolarization
On an ECG what does a QRS complex represent?
Ventricular
depolarization
On an ECG what does a T wave represent?
Ventricular
repolarization
On an ECG what does the section between the P and Q waves represent?
With atrial depolarization complete,
the impulse is delayed at the AV node
T or F
Blood always flows from a region of low pressure to higher pressure.
F
vice versa
T or F
Heart valves are either open or shut depending on the relative
pressures on either side of the valve.
T
Mean arterial blood pressure is determined by two factors:
1) The Cardiac Output (CO), and
2) The Total Peripheral Resistance (TPR)
How do you calculate mean arteriole pressure?
Cardiac Output x Total peripheral resistance
changes in TPR are mainly brought about by changes in…
the state of constriction or dilation of arterioles.
Define systolic pressure
pressure
exerted in aorta during ventricular
contraction
Define diastolic pressure
lowest level of
aortic pressure when heart is at rest
Define pulse pressure
difference between
systolic and diastolic pressure
T or F
Flow is nonpulsatile with a
steady MAP pressure
T
T or F
Pulse pressure and MAP both increase with increasing distance
from heart
F
decrease
T or F
Korotkov sounds are distinct from heart sounds associated with valve closure
T
Two main neural mechanisms control peripheral resistance:
- MAP is maintained by altering blood vessel diameter,
which alters resistance
* Example: If blood volume drops, all vessels constrict
(except those to heart and brain) - Can alter blood distribution to organs in response to
specific demands
Short-term control of MAP mainly occurs via the ….
baroreceptor reflex
Long-term control of MAP mainly occurs via ….
a regulation of blood volume
The pressure detectors of the cardiovascular system are the ….
ARTERIAL
BARORECEPTORS
The MEDULLARY
CARDIOVASCULAR
CENTRE controls the HEART ARTERIOLES
VEINS via the…
efferent nerves of the ANS
…. monitor blood flow to the brain
Carotid sinuses
The …. monitors blood flow to systemic circulation
Aortic arch
Where are Arterial Baroreceptors located?
Located in aortic arch and carotid sinus
Why is Rate of action potential firing
proportional to arterial pressure?
if pressure rises rate of
baroreceptor firing increases
if pressure falls rate of
baroreceptor firing decreases
Increased blood pressure
stimulates baroreceptors to increase input to the ….
vasomotor center
What actions does the vasomotor centre perform when stimulated by barororeceptors?
- Inhibits vasomotor and
cardioacceleratory centers - Stimulates cardioinhibitory
center
The Medullary Cardiovascular Centres can be sibdivided into…
Cardiac Centre (controls the heart)
and a
Vasomotor Centre (controls blood vessels – arterioles & veins)
Where are the Medullary Cardiovascular Centres located?
in the medulla oblongata
