CH. 6 & 7 - Cardiovascular System and Respiration Flashcards
cardiovascular system function
- > delivers nutrients and O2
- > removes CO2 waste
- > transports hormones
- > immune function
- > acid-base balance
3 major circulatory elements
- Heart
- > generates pressure to drive blood through vessels - Channels (Blood vessels)
- Fluid
- > BF must meet metabolic demands
anatomy of the hear
4 chambers
- > R/L atrium (receiving)
- > R/L ventricles (pumping)
all of which covered in thick sac called pericardium and pericardial fluid (fills the thin cavity between the heart and pericardium)
explain blood flow through R and L heart
R heart (pulmonary circulation)
- > pumps deox blood from body to lungs via…
sup vena cava - > R atrium - > tricuspid valve - > R ventricle - > pulmonary valve - > pul arteries - > lung
L heart (systemic circulation)
- > pumps oxy blood from lungs to body
lungs - > pulmonary veins - > L atrium - > mitral valve - > LV - > aortic valve - > aorta
mycardium
aka cardiac or myocardial muscle
- > myocardial thickness varies according to the amount of stress regularly placed on the myocardium
- > LV has the most myocardial/thickest walls (hypertrophy)
- > only has 1 fibre type (similar to type 1; high mitochondria, striated)
- > connected by intercalated discs
*desmosomes hold cells together and gap junctions rapidly conduct AP
myocardial vs skeletal muscle cells
Myocardial cell
- > continuous, involuntary rhythmic contractions, short, branched and one nucleus
Skeletal
- > large, long, multi-nucleated, intermittent, voluntary contraction, Ca released from SR
myocardial blood supply and their branches
R Coronary Artery
- > supplied R side of heart
- > divided into marginal, post interventricular arteries
L coronary artery (main)
- > supplies L side of heart
- > divides into circumflex and ant descending arteries
artherosclerosis
coronary heart disease
4 main components of the cardiac conduction system
Sinoatrial (SA) node
- > Atrioventricular (AV) node
- > AV bundle
- > Purkinje fibres
arterial and venous O2 content
Arterial
20mL O2/ 100ml blood
Venous
At rest
- > 15-16mL O2/ 100mL blood
Heavy exercise
- > 4-6 mL O2/100mL blood
intrinsic controls of heart activity
cardiac muscle has the ability to generate its own electrical signal, this is called spontaneous rhythmicity
- > electrical signals spread via gap junctions
SA node
initiates contraction signal
- > pacemaker cells in upper post RA wall
- > signal spreads from SA node via RA/LA to AV node
- > stimulates RA, LA contraction
AV Node
delays and relays signals to ventricles
- > in RA wall near centre of heart
- > delay allows for RA,LA to contract before RV and LV (Fill)
- > relays signal to AV bundle after delay
AV bundle
relays signal to RV and LV
- > travels along interventricular septum
- > divides into R and L bundle branches
- > sends signal to apex of hear
purkinje fibres
send signal into RV and LV
- > terminal branches of R and L bundle branches
- > spread throughout ventricle wall; stimulates RV and LV contraction
extrinsic control of heart activity
parasympathetic and sympathetic nervous control
parasympathetic nervous system control over the heart
reaches heart vis vagus nerve (cranial nerve nerve X 10)
- > carries impulse to SA and AV nodes
- > signals the release of Ach
*dec. HR and force of contraction
sympathetic nervous control over the heart
- > opposite effect of Para NS
- > carries impulse to SA and AV nodes
- > releases norepinephrine
*inc HR and force of contraction
- > endocrine system has similar effect
cardiac arrythmias
- > bradycardia (RHR lower than 60bpm) and tachycardia (RHR higher than 100bpm)
cardiac cycle
all mechanical and electrical events that happen during 1 heart beat
- > diastole (fill) is twice as long as systole (pump)
stroke volume (SV)
volume of blood pumped in one heart beat
- > during systole; most (not all) blood ejected
SV = End diastolic volume (EDV) - End systolic volume (ESV)
ejection fraction (ef)
% of EDV pumped out
SD/EDV = EF
- > clinical index of heart contractile function
Cardiac output (Q)
total volume of blood pumped per minute
Q = HR x SV (L/min)
resting Q
around 4.2 - 5.6 L/min
(avg total blood volume is around 5L)
- > total BV circulates once every minute
what is required by all tissues
blood flow
what is pressure; relate it to blood flow
a force that drives flow
- > provided by heart contraction
- > bloods flows from regions of high pressure (LV arteries) to regions of low pressure (veins and RA)
resistance
force that opposes flow
- > provided by physical properties of a vessel
- > radius (r) is the most importnant factor
blood flow formula
p/R
- > pressure/radius
- > easiest way to change BF is to change the radius of the vessel (vasoconstriction/dilation
characteristics of arterioles
- > controls systemic R
- > site of most potent VC and VD
- > responsible for 70-80% of pressure from LV to RA
characteristics of the distribution of blood
it goes to where its needed the most
- > often regions of increased metabolism = increase BF
- > blood flow changes after eating and in heat
describe blood distribution at rest and during heavy exercise
At rest (Q=5L/min)
- > liver and kidneys receive 50% of Q
- > skeletal muscles receive 20ish%
Heavy exercise (Q=25L/min)
- > exercising muscles receive 80% of Q via VD
- > flow to liver, kidneys decrease via VC
intrinsic control of blood flow
Metabolic mechanisms (VD)
- > buildup of local metabolic by-products
- > decrease availability O2, increase CO2, K, H, lactate
Endothelial mechanisms (mostly VD)
- > substances secreted by vascular endothelium
- > Nitric oxide (NO), prostaglandins, EDHF
Myogenic mechanisms (VC,VD)
- > local pressure changes can cause VC and VD
- > increase pressure = increase VC; decrease pressure = increase VD
extrinsic (neural) controls of blood flow
the redistribution of flow at organ system level is controlled by neural mechanisms
- > sympathetic NS innervates smooth muscle in arteries and arterioles
- > it extrinsic because the control comes from outside the specific area
what are the effects of baseline, increased and decreased sympathetic activity
baseline activity
- > vasomotor tone; a constant, moderately contracted state to maintain adequate BP
Increased activity
- > causes increased VC
Decreased activity
- > causes decreased levels of VC (passive VD)
what is the purpose of the respiratory system; what carries out this process
to carry O2 and remove CO2 from all body tissues
carried out by 4 processes…
- > pulmonary ventilation (external resp.)
- > pulmonary diffusion (external resp.)
- > transportation of gases via blood
- > capillary diffusion (internal respiration)
pulmonary ventilation
process of moving air into an out of the lungs
- > transport and exchange zone
- nose, mouth, nasal conchae to pharynx to larynx to trachea to bronchial tree to alveoli*
explain the process of inspiration
- > its an active process that involves the flattening of the diaphragm and the elevation of the ribcage and sternum by the external intercostals
- > this expands thoracic cavity, volume inside thoracic cavity and lungs
- > as lung vol increases intrapulmonary pressure decreases
- > air passively rushes in due to pressure difference
forced vs normal inspiration
forced breathing uses additional muscles
- > scalenes
- > sternocleidomastoid
- > pectorals
- raise ribs even further*
Boyle’s Gas Law
states that pressure and volume are inversely correlated
- > If volume increases, then pressure decreases and vice versa, when the temperature is held constant.
explain the process of expiration
usually a passive process
- > inspiration muscles relax and lung volume decreases, intrapulmonary pressure increases
if it is active (forced breathing)
- > internal intercostal muscles pull ribs down, abdominal muscles force diaphragm back up
types of pulmonary volumes
measure using a technique called spirometry
Tidal Volume
- > amount of air entering and leaving the lungs with each breath
Vital Capacity (VC)
- > the greatest amount of air that can be expired after maximal inspiration
Residual Volume (RV)
- > the amount of air remaining in the lungs after maximal expiration, cannot be measured with spirometry
Total lung capacity (TLC)
- > sum of VC and RV
respiratory membrane
where gas exchange between the air in the alveoli and the blood in the pulmonary capillaries occurs
comprised of…
- > the alveolar wall
- > the capillary wall
- > their respective basement membrane
main 2 functions of pulmonary diffusion
replenish blood O2 supply and remove CO2 from the blood
explain the process of pulmonary diffusion
it’s gas exchange between alveoli and capillaries
- > inspired air path: bronchial tree then goes to alveoli
- > blood path: ventricles - > pulmonary trunk - > pulmonary arteries - > pulmonary capillaries (capillaries surround alveoli)
composition of air
- 04% nitrogen
- 93% O2
- 03% CO2
total air pressure (atmospheric pressure)
760mmHg
total air P = PNitrogen + POxygen + PCO2
P = 600.7 + 159.1 + 0.2mmHg
henry’s law
gases dissolve in liquids in proportion to partial pressure
partial pressure: the individual pressures from each gas in a mixture
why are partial pressure gradients important in determining gas exchange
par. press is the most important factor for determining gas exchange as pp gradients drive gas diffusion
- > without gradient, gases are in equilibrium and there is no diffusion
explain the change of oxygens partial pressure as it goes through the body
outside the body (atmospheric P)
- > 159mmHg
when air is inhaled and enters the alveoli
- > 105mmHg
enters the pulmonary capillary with a PO2
- > 40mmHg
PO2 across respiratory membrane
- > 65mmHg
ficks law
rate of diffusion is proportional to the surface area and partial pressure gas gradient
oxygen diffusion capacity
the rate at which oxygen diffuses from alveoli into the blood
lung O2 diffusion capacity at rest vs during exercise
At rest
- > diffusion capacity is limited to to incomplete lung perfusion
- > only bottom ⅓ of lung is perfused with blood
- > top ⅔ have poor gas exchange due to due to less blood due to gravity and weak contractions
During Exercise
- > O2 diffusion capacity increases due to more even lung diffusion throughout the lung
- > systemic BP increases and opens top ⅔ of lung for perfusion; gas exchange over full lung area
explain the change in PCO2 in the lung
PCO2 in pulmonary artery = 46mmHg
PCO2 in alveoli is 40mmHg
- > although this pressure gradient is small (6mmHg) the gradient still permits for diffusion
- > diffusion is allowed despite the low gradient due to CO2 diffusion constant being 20x greater than O2
oxygen transport capacity of blood
can carry around 3ml of O2/1L of plasma
- > 98% is bound to hemoglobin (Hb) in RBC
- > >2% is dissolved in plasma
Hb +/- O2
Hb + O2 = oxyhemoglobin
Hb alone = deoxyhemoglobin
Hb saturation
- > depends on PO2 and affinity between hemoglobin and O2
High PO2 (in lungs)
- > loading portion of O2-Hb dissociation curve
- > small change in Hb saturation per mmHg change in PCO2
Low PO2 (in body tissues)
- > unloading portion of O2-Hb dissociation curve
- > large change in Hb saturation per mmHg change in PO2
factors that affect Hb saturation
blood pH
- > more O2 unloaded at acidic exercising muscles
blood temp
- > warmer blood promotes tissue O2 unloading during exercise
inc pH and decreased temp will increase O2-Hb saturation; hot and basic will decrease saturation
CO2 transport
CO2 is released as waste from cells
Carried in the blood in 3 ways…
- > as bicarbonate ions (60-70% of CO2 in blood to lungs)
- > dissolved in plasma (7-10)
- > bound to Hb (carbaminohemoglobin; 20-33%)
oxygen transport in muscle
O2 transported in muscle by myoglobin
- > similar structure as Hb but has a higher affinity to O2
arterial-venous oxygen difference
*(a-v) O2 difference
the difference between arterial and venous O2 levels
- > reflects tissue O2 extraction; as extraction inc, venous O2 decreases, (a-v) O2 difference increases
