Normal Structure And function Flashcards
Cardiac muscle is unstriated - TRUE OR FALSE
False - it is striated
Cardiac myocytes are electrically coupled by…
Gap junctions
Desmosomes have what function within cardiac muscle?
Provide mechanical adhesion between adjacent cardiac cells
Contractile unit of muscle
Myofibril
Actin filaments form the light/dark appearance of myofibrils?
Light
Within each myofibril, actin and myosin are arranged into….
Sarcomeres
Muscle tension is produced by ___ of actin filaments over myosin filaments
Sliding
Force generation depends upon ________ interaction between myosin and actin filaments
ATP-dependent
Requirements for muscle contraction (2)
ATP
Calcium
Role of calcium in muscle contraction
Binds to troponin, moving the tropomyosin away from the actin myosin binding site
Calcium is released from the _______ _______ in cardiac muscle
Sarcoplasmic reticulum
TRUE OR FALSE - the release of calcium from the sarcoplasmic reticulum is dependent on the presence of extra cellular calcium
True
Calcium induced calcium release is
The release of calcium in response to the release of calcium
Where does the CIcR start in cardiac muscle?
The calcium influx during ventricular muscle action potential through L-type calcium channels - travels down T-tubules increasing the release from SR
Channel that removes calcium from the cell back to the SR
Ca-ATPase
Excitation of the heart normally originations in the ________ cells of the ___ ____ ____
pacemaker cells of the SAN
The heart is normally under the control of the ___
SAN
TRUE or FALSE - the cells in the SAN have a resting membrane potential
False
The SAN constantly drifts towards depolarisation
The pacemaker potential is due to what 3 ion currents?
Na influx and K influx (funny current)
Transient Ca influx
Decreased K efflux
Ion channel responsible for the rising phase of the action potential in the SAN?
LTCC
Ion channel responsible for the falling phase of the action potential in the SAN?
K channel –> K efflux
LTCC inactivation
Why is conduction is delayed within the AVN?
to allow for atrial systole
Phase 0 of ventricular AP
Na influx
Phase 1 of ventricular AP
closure of Na, transient K efflux
Phase 2 of ventricular AP
LTCC balanced with transient K efflux
Phase 3 of ventricular AP
Ca channels close but delayed rectifier K channels remain open
Phase 4 of ventricular AP
resting membrane potential
Nerve which exerts continuous control over the heart?
Vagus nerve
Autonomic predominant control over the heart?
Parasympathetic
Ach from parasympathetic system acts on which receptor in the heart?
M2 muscarinic
NA from sympathetic system acts on which receptor in the heart?
B1 adrenoceptors
NA has a positive/negative chronotropic effect on the heart?
positive
ACh has a positive/negative chronotropic effect on the heart?
negative
P wave represents…
atrial depolarisation
QRS complex represents…
ventricular depolarisation
T wave represents…
ventricular repolarisation
Drug that can be used in extreme bradycardia
Atropine
Atropine works as…
competitive antagonist of ACh
Two requirements for cardiac muscle contraction
ATP and Calcium
requirement for cardiac muscle relaxation
ATP
Calcium binds to ______ to move the ______ out of the vicinty of the actin-myosin binding site
troponin, tropomyosin
Calcium is released from the _______ _______ during ventricular contraction
sarcoplasmic reticulum
T-tubules ensure…
that calcium gets to all levels of the cell to maximise contraction
What is the purpose of the refractory period in cardiac muscle?
it prevents tetanic contraction within the heart muscle.
Calcium is taken back into the sarcoplasmic reticulum by…
the Ca-ATPase
SV =
EDV - ESV
EDV is determined by…
the venous return to the heart
EDV determines the….
preload
diastole
the heart ventricles are relaxed and fill with blood
systole
the heart ventricles contract and pump blood into the aorta and pulmonary artery
5 phases of cardiac cycle
- passive filling
- atrial contraction
- isovolumetric ventricular contraction
- ventricular ejection
- isovolumetric ventricular relaxation
What phase during the cardiac cycle is the P wave seen?
during phase 2 - atrial contraction
The ventricles are 80% full by the end of passive filling - true or false
true
The atria contract between the ____ and the ____ _____
P wave and the QRS complex
Where is the QRS complex seen in the cardiac cycle?
Phase 3 - the isovolumetric ventricular contraction
The first heart sound occurs when?
during isovolumetric ventricular contraction
What causes the first heart sound?
the pressure in the ventricles exceeding that of the atria
T wave signals…
ventricular repolarisation
What happens during ventricular ejection?
valves open and the SV is ejected
what causes the second heart sound?
the ventricular pressure falling below the aortic and pulmonary artery pressure
Auscultation for aortic valve
right sternal edge, 2nd intercostal space
Auscultation for pulmonary valve
left sternal edge, 2nd intercostal space
Auscultation for tricuspid valve
inferior left sternal margin, 4th intercostal space
auscultation for mitral valve
5th intercostal space in mid-clavicular line
during diastole the ventricles are _______ and ____ with blood
relaxed and fill with blood
During systole the ventricles ____ and ____ blood into the ____ and _____ _____
contract and pump blood into the aorta and pulmonary artery
At a heart rate of 75bpm, ventricular diastole lasts (0.5/0.3) secs and ventricular systole lasts (0.5/0.3) secs
0.5, 0.3
5 stages of the cardiac cycle
- Passive Filling
- Atrial Contraction
- Isovolumetric Ventricular Contraction
- Ventricular Ejection
- Isovolumetric Ventricular Relaxation
Events during passive filling of the heart
Pressure in atria and ventricles is nearly 0, AV valves are open allowing venous return to flow into ventricles, Ventricles fill about 80%
Events during atrial contraction
P wave signals depolarisation of atria, End diastolic volume of ~130ml
Events during isovolumetric ventricular contraction
Ventricular contraction starts QRS of ECG, pressure rises, first heart sound as ventricular pressure rises over atria, tension rises rapidly
Events during ventricular ejection
aortic and pulmonary valves open, aortic pressure rises, ESV left behind
Events during isovolumetric ventricular relaxation
T wave signals ventricular repolarisation, ventricles relax and pressure falls, aortic and pulmonary valves shut leading to second heart sound
When might splitting of the heart sound be heard?
at inspiration as the inspiratory pressure is not high enough to promote pulmonary valve closure at the exact same time as the aorta.
When does the JVP occur in relation to the atrial pressure wave?
right after atrial pressure waves
Systolic blood pressure is…
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts
Systolic blood pressure should be maintained between ____ and ____ and not exceed ____mmHG
90 and 120, not exceed 140mmHg
Diastolic blood pressure is…
the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes
Diastolic pressure should not reach or exceed…
90mmHg
Blood normally flows in the arteries in a laminar fashion - True or false?
True
Korotkoff sounds are heard when…
The cuff pressure is between the systolic and diastolic blood pressure
Where is diastolic pressure recorded according to korotkoff sounds?
when no sounds are heard any more
1st korotkoff sound
the first sound is heard at peak systolic pressure
Pressure gradient =
MAP - Central Venous pressure
The right atrial pressure is…
close to zero
5th Korotkoff sound
no sound is heard because of uninterrupted smooth laminar flow
The MAP is the average _____ blood pressure during a single ____ ____
arterial, cardiac cycle
MAP =
[(2xdiastolic) + systolic] / 3
How much MAP is required to perfuse the coronary arteries, brain and kidneys?
60 mmHg
MAP is also equal to?
CO x TPR
SV is…
the volume of blood pumped by each ventricle of the heart per heartbeat
Parasympathetic system has an effect on the arteries and arterioles - True or False?
False - the sympathetic stimulation causes vasoconstriction
What effect does sympathetic stimulation have on the veins?
increased vasoconstriction –> increased venous return and greater SV
Where do the baroreceptors originate?
aortic arch
carotid sinus
How do the aortic baroreceptors send signals to the medulla?
CN X - the vagus nerve
How do the carotid sinus baroreceptors send signals to the medulla?
CN IX - the glossopharyngeal nerve
Foramen where the CN X exits the skull
the jugular foramen
Foramen where CN IX exits the skull
the jugular foramen
The baroreceptor reflex is important in acute and chronic situations - true or false?
False - the baroreceptor reflex becomes desensitised in chronic high blood pressure and thus only adapts to acute changes
Action of sympathetic nervous system in baroreceptor reflex
Causes vasoconstriction when the MAP decreases; MAP decrease causes reduced firing of baroreceptors decreasing vagal tone and increase sympathetic tone
Sympathetic effect on TPR
causes an increase in TPR
Long term control of MAP is largely controlled by…
blood volume
Around ___% of body weight in men is water
60%
Total body fluid =
Intracellular fluid (2/3rd) + Extracellular fluid (1/3rd)
ECF =
plasma volume + interstitial fluid
What two main factors affect ECF volume?
Water excess or deficit
Na excess or deficit
Hormones that regulate ECF volume (3)
RAAS
ANP
ADH
Renin is released from…
the kidneys
Renin stimulates the release of?
angiotensin I
Angiotensin I is produced from?
angiotensinogen from the liver
AngI is converted to Ang II by?
Angiotensin converting enzyme
ACE is produced by?
pulmonary vascular endothelium
AngII stimulates the release of?
aldosterone
Aldosterone is produced
in the zona glomerulosa of the adrenal cortex
AngII causes (2)
systemic vasoconstriction, ADH release
Aldosterone is a steroid hormone - True or false
True
Aldosterone acts ont eh kidneys to?
increase sodium and water retention
Increasing sodium and water retention causes?
increase in plasma volume
Renin is released from where in the kidney?
the juxtaglomerular apparatus
3 things which stimulate renin release
(1) renal artery hypotension
(2) stimulation of renal sympathetic nerves
(3) decreased Na in renal tubular fluid
Cells responsible for sensing Na in the renal tubules
Macula densa cells
Type of cells that release renin
granular cells
Where is atrial naturietic peptide produced?
atrial myocytes
What stimulates production of ANP?
atrial distension
ANP causes…
excretion of salt and water from the kidnyes
ANP acts to ________ the RAAS system
counteract
ADH is also known as?
Vasopressin
ADH is synthesised by the _______ and stored in the ________
hypothalamus, posterior pituitary
What two things stimulate the release of ADH?
- reduced ECF volume
2. Increased ECF osmolarity
Normal osmolarity of ECF is…
280mosml/l
AD acts on the kidney tubules to…
increase the reabsorption of water
ADH acts on the blood vessels to…
cause vasoconstriction
The actions of ADH on the blood vessels is important in…
hypovolaemic shock
Pulse pressure =
SBP - DBP
Resistance = (Pouiseilles law)
[n.L]/r^4
What has the greatest effect on resistance?
radius
Extrinsic control of vascular smooth muscle involves which two factors?
hormones
nerves
Which nerves supply the vascular smooth muscle?
sympathetic
Sympathetic nerves supply _____ to the vascular smooth muscle
noradrenaline
Noradrenaline acts on __ ________ in the vascular smooth muscle
a-adrenoceptors
True or False - blood vessels are partially constricted at rest to maintain blood pressure
True - this is called vasomotor tone
What causes the vasomotor tone?
the tonic discharge from sympathetic fibres
Adrenaline is released from…
the adrenal medulla above the kidneys
Adrenaline acts differently depending on the organ and receptor - True or False?
True
Adrenaline acts on a adrenoceptors in the cardiac and skeletal muscles to vasodilation - True or False
False - acts on B2 adrenoceptors to cause vasodilation
What adrenoceptors does adrenaline act on in the skin, gut and kidney arterioles? What is the effect?
a-adrenoceptors, causes vasoconstriction
Why does adrenaline have alternating effects in different organs?
allows for strategic distribution of blood flow
Angiotensin II and ADH cause _______
vasoconstriction
Intrinsic controls of vascular smooth muscle are…
local metabolic changes which can override extrinsic effects
Effect of increased PO2 on vascular smooth muscle
constriction
Effect of increased PCO2 on vascular smooth muscle
vasodilation
Effect of increased H+ on vascular smooth muscle
vasodilation
Effect of increased EC K+ on vascular smooth muscle
vasodilation
Effect of decreased osmolality on vascular smooth muscle
constriction
Humoral agents which increase relaxation of vascular smooth muscle
histamine, bradykinin, Nitric oxide
Humoral agents which increase vasoconstriction of vascular smooth muscle
serotonin, thromboxane A2, leukotrienes, endothelin
Endothelin is produced by…
endothelial cells
What factors can damage endothelial health? (4)
high BP, hypercholesterolaemia, diabetes, smoking
Endothelial produced vasodilators have what effects? (3)
Anti-thrombotic; anti-inflammatory; anti-oxidants
Effect of cold temperature on vascular smooth muscle?
vasoconstriction
Nitric oxide is produced from?
L-Arginine
Nitric oxide has a long half-life - T or F?
False, it has a short half life of a few seconds
Calcium is released from the endothelial wall in the presence of…
shear stress - leads to activation of NOS –> NO
NO activates ____ which aids vascular smooth muscle relaxation
cGMP
Four factors which influence venous return
Increased blood volume
Increased vasomotor tone
Increased skeletal muscle pump
Increased respiratory pump
What does increasing venous return do?
increases atrial pressure and thus EDV and SV
Are venous smooth muscles supplied by nerves?
yes sympathetic nerves
An increase in CO increases DBP - true or false?
false - increases SBP
Metabolic hyperaemia causes a decrease in what two things?
TPR and DBP
Exercise causes an increase in…
pulse pressure
Likely effects of chronic exercise on CVS (6)
reduction in sympathetic tone; increases parasympathetic tone to the heart; cardiac remodelling; reduction in plasma renin levels; improved endothelial function; decreased arterial stiffening
Sympathetic stimulation increases HR by exerting what two effects?
increasing rate of SAN firing
decreases AV nodal delay
condition where the pericardial cavity fills with blood preventing contraction
cardiac tamponade
Coronary arteries branch of at…?
the ascending aorta, almost instantly after leaving the ventricle
Vein that drains blood back into the right atrium from the myocardium
coronary sinus
Vagus nerve descends where?
lateral to the trachea, behind the hila of the lungs, medially by the heart
Where does the phrenic nerve descend?
down the lateral side of the heart
The left coronary artery splits into what three branches?
circumflex, left marginal and left anterior descending
the left anterior descending artery has what extra branch?
the lateral branch
The right coronary artery splits into which 2 arteries?
right marginal artery anteriorly;
posterior interventricular artery
mitral stenosis can be heard when?
during diastole (without pulse)
mitral regurgitation can be heard when?
during systole (with pulse)
What germ layer is the heart derived from?
visceral part of the lateral mesoderm
during cranio-caudal folding the heart moves from where to where?
the cervical to thoracic area
there are initially how many pairs of the aortic arches?
6
the 3rd arch of the aorta develops into…
the common carotid artery and the first part of the internal carotid artery
The 4th aortic arch develops into…
the right subcalvian artery and part of the aortic arch
the 6th aortic arch becomes…
the sprout branches that form the pulmonary arteries and ductus arteriosus on the left
the ductus arteriosus becomes what post-birth?
the ligamentus arteriosum
What is the function of the Vitelline veins?
drain the yolk sac - important in development of gut and portal system
What is the function of the umbilical veins?
oxygenated blood from the placenta - right vein degenerates
Which umbilical vein degenerates?
right umbilical
What does the left umbilical vein become?
the definitive umbilical vein
What do the cardinal veins give rise to?
the systemic venous system
The anterior cardinal veins give rise to…
the jugular and left brachiocephalic vein, and the SVC
the posterior cardinal veins give rise to…
the azygous and hemiazygous systems, gonadal and renal veins, iliac veins, IVC
What two systems are involved in the circulatory systems?
the cardiovascular system, the lymphatic system
What are the roles of the circulatory system? (5)
transport of oxygen and nutrients; transport of CO2 and metabolic waste; temperature regulation; distribution of hormones; penile erection in males
where is most of the blood held in the circulatory system?
veins ~60%
What are the 3 basic layers to the blood vessels?
Tunica intima, tunica media, tunica adventitia
What makes up the tunica intima?
single layer of squamous epithelial cells attached to a basal lamina and a thin layer of connective tissue
What makes up the tunica media?
smooth muscle and elastic tissue
What makes up the tunica adeventitia?
connective tissue
true or false - large arteries can get all the nutrients from the lumen of their vessel?
false - only the inner half - the rest can receive nutrients from the vaso vasorum
What is the vaso vasorum?
the vascular supply to the large arteries.
what cells in the basal lamina may help capillaries constrict to control blood flow?
pericytes
what are the 3 types of capillary?
continuous, fenestrated, sinusoidal (discontinuous)
which type of capillary is most common?
continous
Where are continuous capillaries found?
skin, lung, muscle, connective tissue, nerves
What feature determines fenestrated capillaries?
they have pore in their walls
where are fenestrated capillaries found?
in the mucosa of the gut, endocrine glands, glomeruli of the kidney
What feature determines sinusoidal capillaries?
lack a basal lamina and have large gaps throughout
where are sinusoidal capillaries usually found?
liver, spleen, bone marrow
3 layers of the heart
endocardium, myocardium, epicardium
Where does the endocardium extend to?
the valves
What is included in the endocardium structure? (4)
endothelium, basal lamina, collagen fibres, denser connective tissue
what is the sub-endocardium?
extension of the endocardium (loose connective tissue) which contains small blood vessels, nerves and impulse conducting system
Features of the myocardial cells
one central nucleus (maybe 2), irregularly placed intercalated discs
What feature is likely found in the epicardial layer of the heart?
large branches of the coronary blood vessels
lymphatic capillaries begin as…
blind sacs
most of the excess interstitial fluid returns to…
the venous system
The passing of lymph through lymph nodes provides opportunities for…
immunological surveillance
Things that aid the movement of lymph (2)
hydrostatic pressure, muscles around the lymph vessels, valves within the vessels
The lymphatic system helps to deliver fats to the _____ from the _____ _____
liver, small intestine
What is shock?
an abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation
What affects Stroke Volume (3)?
Preload, Myocardial contractility, Afterload
What is hypovolaemic shock?
where a loss in blood volume –> decreased venous return –> decreased EDV and SV –> Decreased CO and MAP –> inadequate perfusion
The heart can compensate for what loss in blood volume?
30%
What is cardiogenic shock?
Sustained hypotension caused by decreased cardiac contractility
How does cardiogenic shock lead to inadequate tissue perfusion?
Decreased cardiac contractility –> decreased SV –>Decreased CO and MAP –> Inadequate tissue perfusion
Example of obstructive shock?
Tension Pneumothorax
How does a tension pneumothorax lead to inadequate tissue perfusion?
Increased intrathoracic pressure –> decreased venous return –> decreased end diastolic volume & decreased SV –> Decreased CO and MAP –> Inadequate tissue perfusion.
What can cause neurogenic shock?
Spinal Cord injury
How does a spinal cord injury lead to inadequate tissue perfusion?
Loss of sympathetic tone –> massive venous and arterial vasodilation –> decreased venous return and TPR –> Decreased CO and MAP –> Inadequate tissue perfusion
Steps in treatment of Shock?
ABCDE
High flow oxygen
Volume replacement
Extra step in treatment of Cardiogenic shock…
ABCDE, high flow oxygen, volume replacement, inotropes
Extra step in treatment of shock due to tension pneumothorax…
ABCDE, high flow oxygen, volume replacement, Immediate chest drain
Extra step in treatment of anaphylactic shock
ABCDE, high flow oxygen, volume replacement, adrenaline
Extra step in treatment of septic shock
ABCDE, high flow oxygen, volume replacement, vasopressors
If someone is suffering from haemorrhagic shock, how would you expect to find their pulse?
Fast and thready, potentially weak
If someone is suffering from haemorrhagic shock, how would you expect to find their peripheries?
cool and potentially clammy
In the presence of blood loss, the baroreceptor reflex sends signals to…
the medulla in the CNS
The medulla (increases/decreases) vagal tone during haemorrhagic shock?
decreases
The medulla (increases/decreases) sympathetic activity during haemorrhagic shock?
increases
An increase in constriction of the veins during haemorrhagic shock leads to….
increased stroke volume
An increase in constriction of the arteries during haemorrhagic shock leads to….
increased TPR
Effect of sympathetic NS on the heart?
increased HR and contractility
Effect of parasympathetic NS on the heart?
decrease HR
Where do visceral afferent fibres travel?
alongside sympathetic nerves
Visceral reflex afferents from baroreceptors travel mainly in the…
vagus nerve (CN X)
Where are the sympathetic ganglia held?
sympathetic chain in the thoracolumbar region
What are splanchnic nerves?
pairs of visceral efferents or afferents that carry fibres of the autonomic nervous system
Which set of splanchnic nerves are not sympathetic?
pelvic
Where are the cardiopulmonary splanchnic nerves are predominantly sided where?
the left side
Where is the cardiac plexus found?
At the level of the carina, around the pulmonary trunk
WHere are the ganglia for the parasympathetic nerves found?
on the target organ
Where are the parasympathetic outputs?
cranial and sacral regions
what 4 cranial nerves have their ganglia in the head?
Vagus nerve (CN X), Occulomoter (III), Facial (VII), Glossopharyngeal (IX)
CN III
Occulomotor
CN VII
Facial
CN XI
Glossopharyngeal
What is pain?
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Somatic sources of chest pain (6)
muscle; joint; boney; intervertebral disc; fibrous; nerve
Visceral sources of chest pain (4)
Heart and great vessels, trachea, oesophagus, abdominal viscera
Somatic pain is typically described as…
well localised, typically sharp and stabbing pains
Visceral pain is typically described as…
dull, aching, nauseating and poorly localised
Radiating pain is described as…
pain felt in the centre of chest AND spreading from there
Referred pain is described as…
pain only felt at a site remote from the area of tissue damage
Where does referred pain tend to travel?
along the dermatomes
Which dermatome would herpes zoster most likely cause a sharp somatic chest pain?
T4/5
Common radiations of cardiac chest pain?
Jaw, arm, neck, back
What is a myocardial infarction?
irreversible death of part of the myocardium due to the occlusion of its arterial blood supply
3 surfaces of the heart affected by an MI
Anterior, Inferior, Anterolateral
Where do 40-50% of MIs occur?
the LAD
where do 30-40% of MIs occur?
the right coronary artery
where do 15-20% of MIs occur?
the circumflex artery
Commonly used vessels in the revascularisation/bypass grafting of the heart?
radial/internal thoracic artery and the great saphenous vein
What may occur if the ischaemia affects the SAN or AVN?
arrhythmias
AVN damage during MI can result in…
complete heart block
Bundle branch damage during an MI can result in…
bundle branch block
decreased PO2 causes ______ of the coronary arterioles
vasodilation
Adenosine is naturally produced from?
ATP
sympathetic vasoconstriction around the coronary arterioles is overridden by ______ ______ during exercise
metabolic hyperaemia
coronary arterioles are supplied by sympathetic vasoconstrictor nerves which act via __-adrenoceptors
a-adrenoceptors
peak left coronary blood occurs during (systole/diastole)
diastole - the contraction of the heart during systole constricts the movement of blood in to the coronary arterioles
Which arteries anastamose to form the circle of willis?
carotids and basilar arteries
which arteries supply the brain?
internal carotids and vertebral arteries
which particular part of the brain is very sensitive to hypoxia?
grey matter
What types of stroke can occur?
ischaemic or haemorrhagic
arterial pressure range within the brain?
60-160mmHg
autoregulation of brain arterial pressure fails when…
MABP is outwith 60 - 160mmHg
an increase in PCO2 within the brain causes vaso_______
dilation
why can hyperventilation lead to fainting?
causes a decrease in PCO2 which causes vasoconstriction within the brain.
three things which cross the blood brain barrier?
oxygen, carbon dioxide, glucose
average intracranial pressure
8-13mmHg
Cerebral perfusion pressure =
MABP - ICP
How does glucose cross the BBB?
facilitated diffusion
pulmonary BP is typically a (high/low) pressure system
low pressure system - approx 10% of that of the systemic
how do the lungs protect against pulmonary oedema?
the absorptive forces exceed the filtration forces
hypoxia causes vasoconstriction of the pulmonary arterioles - why?
helps direct blood flow to areas of the lung where the ventilation is better
circulating adrenaline causes vasodilation in the skeletal smooth muscle via __adrenoceptors
b2-adrenoceptors
the one way venous valves and the skeletal muscle pump allows ?
blood to flow back towards the heart
Blood pools in the limb veins if…
venous valves become incompetent
What is the result of blood pooling in the limbs?
varicose veins
why don’t varicose veins lead to a reduction in cardiac output?
there is chronic compensatory increases in blood volume
