Lectures 1-3 Flashcards
How is heart rate determined?
SA node rate of decay
SA>AV>Bundle of His>Purkinje Fibers
Depolarizes independently of any external drive
Sympathetic Stimulation _____ HR
increases
faster rate of depolarization
inc permeability to NA+
Parasympathetic stimulation ____ HR
decreases
hyperpolarization
slowed decay
Base or Apex of heart contracts first?
Apex contracts before heart
Can Purkinje fibers be seen grossly?
stain with iodine to grossly see
What are Purkinje cells? Histology?
conducting myocytes
pale central area because of glycogen
How is the AP propagated in myocytes
adjacent cells have gap junctions
Conduction velocity depends on: (3)
- shape of AP- faster upswing=more rapid conduction
- diameter of muscle fiber- inc diameter= inc conduction
- Disease states change ionic conductance
What has fastest and slowest conduction velocity in heart
fastest purkinje
slowest AV node- delay to allow heart to fully fill
AP in cardiac myoctyes (phases (0-4))(fast)
0: Depolarization with entry of SODIUM
1: early repolarization due to efflux of K+
2: Plateau due to entry of Ca+2
3: Repolarization with entry of K+
4: Restoration with exchange (ATP) of Na+ for K+
Refractory Period
to prevent tetany (special to cardiac myocytes)
VO Na+ channels are inactivated in phase 0 until membrane potential more negative than -65
Autorhythmicity controlled by what located where?
SA node (R atrium) and AV node (IV septum) if SA node fails
Pacemaker AP (slow)
phase 4 decays towards threshhold (more positive) No VO Na+ channels! Slow depolarization shorter plateau and lower amplitude AP Depolarization is from entry of CALCIUM Unstable resting potential
Membrane potential of cardiac pacemaker
K+ is freely permeable- move into cell via electrical gradient and out of cell via [ ] gradient
Cell membrane not permeable to Na+ (actively pushed out for K+ with ATP-Na/K pump)
Na/Ca exchange-Na in Ca out
interior of cell becomes + -> depolarization and because myocytes are all connected the signal is propagated through all cells
Aorta
where from
and parts
from L ventricle
Ascending, Aortic Arch, Descending
Aortic Arch Branches
Brachiocephalic trunk (1st branch), left subclavian artery (2nd Branch)
Branches of Brachiocephalic trunk
L common carotid artery
R common carotid artery
R subclavian artery
L and R subclavian arteries give rise to 4 main branches
1 Vertebral Artery- cervical muscle, spinal cord, brain
2 costocervical artery- 1-3rd intercostal spaces
3 internal thoracic artery- thoracic wall
4 superficial cervical artery-> axillary artery
Left Ventricle (very Fit)
valves
2 other things
mitral valve- bicuspid
aortic valve-3 semilunar valvules
2 papillary muscles- from the outer wall
trabeculae septomarginalis
Left Atrium- openings
- 6 pulmonary veins- 2 from left, 4 from right
- small coronary veins
- left AV orifice-> LV
Muscular IV Septum- 2 components
Thin membranous portion- site of closure of IV foramen
Thick muscular portion
Right Ventricle
-blood from where to where
-valves
Right ventricular cavity(3)
Blood from RA to pulmonary trunk
tricuspid valve and pulmonary valve (3 semilunar valvules)
R ventricular cavity
- R septomarginalis trbecule
-trabecular carne (to reduce turbulence)
-3 papillary muscles- 2 septum, 1 big from outer wall
What directs blood to pulmonary trunk in the RV?
Conus arteriosus
R Atrium
openings (4)
Azygous veins
cranial vena cava
Caudal vena cava
coronary sinus
R AV orifice (venous blood RA-> RV
Right only- carnivores, horse,
Left only- pig
Left and Right- ruminants
Right Auricle muscles called? Fossa ovalis- Intervenous Ridge- one more
pectinate muscles
oval depression on interatrial septum
direct blood from cranial vena cava to ventricle
crista terminalis
Interventricular septum- externally marked (
Left side- paraconal groove
Right side- subsinuosal groove
Left surface of the heart
auricular
Right surface of the heart
atrial
most cranial part of heart?
right auricle
forces influencing fluid movement across capillary wall(4)
capillary BP
plasma colloid osmotic (oncotic) pressure
interstitial fluid hydrostatic pressure
interstitial fluid colloid osmotic pressure
BP gradually decr along length of the capillary therefore..
amount of fluid filtered out decr in 1st half then inc in 2nd half
Characteristic of all cardiac muscle cells (6)
conductivity contractility autorhymicity electrically connected (gap junctions) pacemaker cells conduction pathways
vessels in series
pressure will decrease along network with the biggest pressure drop being in the arterioles
vessels in parallel
within an organ
over R is lower than R in any elements of network
blood flow to one organ can be altered without altering flow to other organs
Determinants of R (poiseuille’s law)
Resistance inversely proportional to radius (power of 4)
According to poisueille’s law, blood flow depends on(3)
Pressure difference= MAP - central venous pressure
TPR- radius
Viscosity- not easily changed
What makes blood flow
pressure difference is the driving force for flow
basic flow equation
Flow Rate (Q)= Pressure difference/ Resistance
Blood flow can be altered by
changing pressure difference across vascular bed
changing vascular resistance (radius)
Circulation of ECF- 2 levels
Bulk transport- substances moved between organs (slowest in capillaries)
Trans capillary solute diffusion- from capillaries into cells
4 factors that determine diffusion rate
[ ] difference
SA for exchange
diffusion distance
Permeability of the wall to diffusing substance
