The Heart and CV system Flashcards
Functions of CV system
- Transport- delivery of O2, hormones and nutrients etc, waste removal
- Maintenance- body temp, pH, vasodilation, baroreceptors (dehydration)
- Protection- wbc delivery
name of two circuits
Systemic and Pulmonary
Pulmonary artery function
deoxygenated blood from heart to lungs
Systemic artery function
oxygenated blood from heart to body
systemic vein function
deoxygenated blood from body to heart
pulmonary vein function
oxygenated blood from lungs to heart
Pulmonary circuit carries blood…
to and from lungs
Systemic circuit carries blood…
to and from rest of the body
Factors influencing heart size
height, weight, age, sex, training status
Right side of heart used by
systemic circuit
pulmonary circuit uses which side of the heart
left side
blood route from S circuit
S circuit- RA, RV, P circuit
blood route from P circuit
P circuit- LA, LV, S circuit
Location of heart
Thoracic cavity anterior mediastinum, posterior to the sternum for protection. Between lungs.
Base of heart location
sits posterior to sternum at level of 3rd costal cartilage. average heart starts at 1st costal cartilage. Centre of base sits left of midline
Apex of heart location
average 5th intercostal space
Pericarditis symptoms
inflammation resulting in increased production of pericardial fluid causing cardiac tamponade
Cardiac Tamponade
restricted movement of heart due to increased fluid in pericardial cavity. Caused by trauma or pericarditis
Right atria receive blood from
S circuit via SVC and IVC
Left atria receive blood from
P circuit via 2 L and 2 R Pulmonary veins
What is special about the openings leading into the atria?
no valves
Characteristics of atria
thin walls, highly expandable
Expandable extension of atria
auricle
Anterior wall and inner auricle of atria contain
pectinate muscles
pectinate muscles
prominent muscular ridges on anterior wall and inner auricle of atria
R ventricle sends blood
P circuit
L ventricle sends blood
S circuit
How does RV differ from LV?
‘Moderator band’ and LV thicker muscular wall
Structural feature of ventricles
trabeculae carnae- series of muscular ridges
Function of moderator band
Delivers stimulus for contraction to pap muscles so can tense chordae tendinae before ventricle contracts.
What is the moderator band
muscular ridge extending horizontal from inferior interventricular septum, connect to anterior papillary muscle.
How does the LV contract?
apex closer to base, diameter decreases for max contraction to open SL valves
Function of septa
separate chambers
Septa of heart
Interatrial septum, interventricular septum
conus arteriosus
Superior R ventricle tapers into cone-shaped pouch which ends at pulmonary SL valve
Valve function
permit blood flow in one direction. Prevent backflow/ regurgitation.
Valve structure
Fold of fibrous tissue (cusps) extending btwn openings.
chordae tendinae
CT fibres that originate at papillary muscles. Free edge of cusps of valves attach to ch.t
Papillary muscles
conical muscular projections arising from inner surface of right ventricle
Function of papillary muscles
prevents inversion of AV valves by pulling closed during contraction
Valves of atria
Atrioventricular (tricuspid and mitral/ bicuspid)
Valves of ventricles
Semilunar (pulmonary and aortic)
Valvular Heart Disease
disfunctional valves following Carditis
Carditis
Inflammation of heart
Causes of Carditis
Strep infection result in rheumatic fever- inflamm autoimmune response
Passage of blood through aorta
Blood from LV through aortic SL valve into ascending aorta
Aortic sinuses
sac-like extension of base of asc aorta, adj to each cusp of valve
sac-like extension of base of asc aorta, adj to each cusp of valve
aortic sinuses
structures of aorta
asc aorta, aortic arch, desc aorta
fibrous band left over from fetal blood vessel once linking P and S circuits
Ligamentum Arteriorum
Ligamentum Arteriorum
fibrous band left over from fetal blood vessel once linking P and S circuits
Superior vena cava
- opens into posterior, superior portion of R atrium
* delivers blood from head, neck, upper limbs, chest
Inferior vena cava
- opens into posterior, inferior portion of R atrium
* blood from trunk, viscera, lower limbs
deep groove marking border of artia and ventricles
coronary sulcus
grooves mark boundary of left and right ventricles
Anterior interventricular sulcus and posterior interventricular sulcus
coronary sulcus
deep groove marking border of artia and ventricles
Anterior interventricular sulcus and posterior interventricular sulcus
grooves mark boundary of left and right ventricles
Foramen Ovale
In fetus, opening penetrating ineratrial septum, connecting L and R atria of fetal heart. Permits blood flow from R to L atrium whilst lungs developing. Closes at birth, Fossa Ovalis remains at the site.
avg BPM
70
avg cardiac output at rest
5L/min
avg CO during exercise
15-20L/min
Cardiac output definition
volume of blood pumped by LV in 1 min
Cardiac Output equation
HR x SV
Stroke volume definition
amount of blood pumped out of V during each contraction
stroke volume equation
EDV-ESV
EDV definition
EDV (end-diastolic volume) – amount of blood in V at end of diastole
ESV definition
(end-systolic volume) – amount of blood in V after contraction
Frank-Starling principle
Increasing EDV = increase SV => ‘more in, more out’
Factors of EDV
filling time and VR. Filling time- duration of V diastole, faster HR shorter filling time.
VR variable responds to changes in COutput, blood vol, peripheral circ.
Preload (SV EDV)
degree of stretching in V muscle cells, directly proportional to EDV.
avg EDV in resting adult
around 130ml
Heart wall layers
Epicardium, Myocardium, Endocardium
Epicardium features
Covers surface of heart. Consists of exposed mesothelium and underlying areolar tissue att to myocardium
Pericardium- Outer fibrous layer, 2 layer parietal layer cont pericardial fluid, 1 layer visceral layer of epicardium.
Function of Epicardium
Collagen dense network. Stabalises heart- att to sternum, diaphragm and vessels of heart
Myocardium features
Cardiac muscle tissue. Layer contains cardiac muscle cells, CT, BV, nerves.
Thickness depends on function of chamber
Seperate blood supply
Atrial myocardium features
Atrial myocardium cont muscle bundles wrap around atria and encircle great vessels
Cardiac muscle cells features
- Cardiac muscle cell- short and wide, Y-shaped branched.
- Intercalated discs* connect cells and decrease resistance pway of impulse btwn cells and ensure sychronicity and coordination
Invol contraction- pacemaker cells via ANS and EC system (autorhythmicity)
Nucleus and large no mitochondria
superficial ventricular muscle structure
wraps around both ventricles, deeper muscle spiral around and between ventricles towards apex.
Endocardium features
Covers inner surfaces including heart valves. Simple squamous epithelium and underlying areolar tissue. SS epithelium (Endothelium) continuous with that of great vessels.
Communication btwn myocardial cells
intercalated discs as junction btwn cells as well as gap junction- depol to pass btwn cells and synch muscle contraction
desmosomes- bind adj myocytes, strong; not pulled apart by contraction.
Types of CT in heart
collagen and elastic
Cardiac muscle cell wrapped in
elastic sheath
Struts function
tied together Adj cells via fibrous cross links
Fibres interwoven into sheets separating deep and superficial muscle layers
Function of cardiac CT
o Physical support for muscle fibres, blood vessels, and nerves of myocardium
o Distribute forces of contraction
o Add strength and prevent overexpansion of the heart
o Provide elasticity helps return heart to original size and shape following contraction
Cardiac skeleton structure and function
- Four dense bands of elastic tissue
- Encircles heart valves and base of pulmonary trunk and aorta
- Stabilise position of heart valves and ventricular muscle cells
- Electrically insulate ventricular cells from atrial cells
Coronary artery origin
L+R arteries orginate at base of Aa, at aortic sinuses.
Aortic sinuses BP
highest BP in S circuit
What mechanism allows blood flow into S circuit and A.sinuses
Elastic recoil
Elastic recoil
pushes blood both forward into S circuit and backward through aortic sinuses into coronary arteries
R Coronary Artery
follows coronary sulcus,
supplies RA, portions of L+RV, portions of electrical conducting system.
Gives rise to marginal arteries- extend across surface of RV.
Supplies posterior interventricular artery which runs toward apex in post intervent sulcus, which supplies intervent septum and ventricles.
L coronary artery
supplies LV, LA, intervent septum. Gives rise to circumflex artery which curves around coronary sulcus, and anterior intervent artery which wraps around pulmonary trunk and runs along ant intervent sulcus.
anterior intervent artery supplies
small tribularies continuous with those of PIA
Arterial anastomoses
interconnections btwn arteries
AIA continuous with PIA allows
constant blood supply to muscle despite pressure fluctuations in L+R CA
structure following anterior surface of ventricles along intervent sulcus and coronary sulcus.
Great cardiac vein
Great cardiac vein
Drains blood from the region supplied by AIA (LCA). Cardiac veins return to coronary sinus
coronary sinus
large, thin-walled vein, opens into RA near IVC.
Posterior vein of LV
drains circumflex artery region
Middle cardiac vein
drains PIA region
small cardiac vein
receives blood from post surface of RA+RV
Anterior cardiac veins (ant veins of right ventricle)
drain ant surface of RV, empty into RA.
What initiates contraction of heart chambers
Electrical impulses of conducting system
types of cardiac cell
contractile and conducting (PM)
Pacemaker cells function
autorhythmicity
Establish normal HR
Interconnect SA and AV nodes, distribute contractile stimulus throughout myocardium.
Distribute stimulus to cardiac muscle cells
PM cell location
internodal pways in atrial walls
Ventricles- bundle of His and P-fibres
Bundle of His and P Fibres function
distrib stimulus to ventricular myocardium
‘Pacemaker potential’
no stable resting membrane potential
anytime cell repol, drifts towards threshold as result of slow flow of Na without compensating outflow of K
What directly influences PM cells
Venous return
Venous return impact
Bainbridge reflex
VR increases- more blood in A- more stretch. PM stretched so more rapid depol => increase HR.
Bainbridge reflex
adjustments in HR in response to increased VR
Regulation of Pm cells
SA node, AV node and Purkinje fibres
Cardiac pacemaker
SA node
SA node location
posterior wall of RA near SVC
AV node location
junction btwn A and V near coronary sinus
SA node mechanism
periodic electric impulses, depol cardiac muscle L and R atria
Fastest depol at SA node. Establishes basic heart rhythm/ sinus rhythm
AV node mechanism
stim by SA node, delay for empty of A before V contraction due to PM cells less efficient at relaying impulse, conducting cells in AV node quicker- coordination.
AV node depol impulse travel down intervent septum AV bundle of His to P-fibres.
P fibres function
contract LV and RV
max bpm of AVnode and ventricles
230bpm
why is 230 max bpm?
reduced pumping efficiency due to mechanics over 180 bpm
230 bpm only occur when stim by drugs or damage occurred.
How does the cardiac skeleton help coordination of heartbeat
isolates atrial myocardium from ventricular myocardium so that impulse of SA node only stim A
HR regulators
ANS control
Catecholamines
Chemoreceptors
Baroreceptors
Hormonal control of HR
Effect SA node
Epinephrine from adr.medulla after active symp nerves innervating tissue. Increases HR and contractility (inotropy). Binds to adrenergic receptors on the heart.
Norepinephrine initial inotropy but longer exposure so overall decline in inotropy. Released by adr.medulla but mostly spillover from symp nerves innervating blood vessels. Bind to adrenergic receptors on heart.
ANS control
Cardiac plexus
Cardiac centers in MObl
Postganglionic symp neurons located in cervical and upper thoracic ganglia. Vagus nerves carry psymp pregang fibres to small ganglia in cardiac plexus
Sympathetic NS increase HR
Psympathetic NS (Vagus Nerve) decrease HR
Both innervate SA and AV node
More symp fibres in V contractile cells
At rest PSNS dominates, exercise SNS dom.
P/Symp divisions alter HR change ionic permeability of conducting cells esp SA node.
nerve network how ANS innervates heart
cardiac plexus
Cardiac centres in medulla oblongata
Cardioacceleratory centre = sympathetic neuron control (increase HR)
Cardioinhibitory center control Psymp neurons (decrease HR). Receive input from P/Symp centers in hypothalamus
Chemoreceptors
Monitor chem characteristics- regulate function of CV and respiratory systems.
Respond to levels of CO2 and pH of blood.
Types of chemorec
Peripheral CR- Cartoid bodies and aortic bodies
Central CR- Medulla
Regulating mechanism of CR
High CO2/ Low pH = increased breathing rate to offload CO2, increased HR
Low CO2/ high pH = decreased breathing rate, decreased HR
Baroreceptors mechanism
• Mechanical, sense change in blood pressure beat-to-beat
Bainbridge reflex
BR structures
Cartoid sinus senses increase and decrease
Aortic arch senses increase only
Cardiac centers in brain respond to
Cardiac centres in brain respond to change in BP and CO2/o2 conc from barorec and chemorec
Atria systole
First step CC
Atria contract, via AV valve fill ventricles 70%, systole ‘tops off’ remaining V space
Blood cannot flow into A from veins due to A pressure exceeding vein pressure at this time. V little backflow due to blood taking path of least resistance
End of AS- EDV
- Ventricular systole/ atrial diastole
2nd step CC
begin at same time
Early VS contraction but not enough pressure to open SL valves. Contract isometrically isovolumetric contraction rising pressure in V but no volume changes.
When pressure in V exceeds arterial trunks, SL valves pushed open, blood into pulmonary and aortic trunks.
Blood ejected= Stroke vol
V pressure falls, SL valves close
VS lasts 270 msec
- Ventricular diastole/ whole heart relax
3rd step in CC
VD lasts 430 msec, filling occurs passively, cycle restarts
What happens to CC when HR increases?
phases shorter
Diastolic portions reduced by up to 75% when HR climbs to 200 bpm
