Lectures 1-3 Flashcards by cindi sirko

How is heart rate determined?

SA node rate of decay
SA>AV>Bundle of His>Purkinje Fibers
Depolarizes independently of any external drive

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Sympathetic Stimulation _____ HR

increases
faster rate of depolarization
inc permeability to NA+

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Parasympathetic stimulation ____ HR

decreases
hyperpolarization
slowed decay

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Base or Apex of heart contracts first?

Apex contracts before heart

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Can Purkinje fibers be seen grossly?

stain with iodine to grossly see

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What are Purkinje cells? Histology?

conducting myocytes

pale central area because of glycogen

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How is the AP propagated in myocytes

adjacent cells have gap junctions

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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

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What has fastest and slowest conduction velocity in heart

fastest purkinje

slowest AV node- delay to allow heart to fully fill

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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+

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Refractory Period

to prevent tetany (special to cardiac myocytes)

VO Na+ channels are inactivated in phase 0 until membrane potential more negative than -65

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Autorhythmicity controlled by what located where?

SA node (R atrium) and AV node (IV septum) if SA node fails

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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

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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

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Aorta
where from
and parts

from L ventricle

Ascending, Aortic Arch, Descending

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Aortic Arch Branches

Brachiocephalic trunk (1st branch), left subclavian artery (2nd Branch)

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Branches of Brachiocephalic trunk

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L common carotid artery
R common carotid artery
R subclavian artery

L and R subclavian arteries give rise to 4 main branches

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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

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mitral valve- bicuspid
aortic valve-3 semilunar valvules
2 papillary muscles- from the outer wall
trabeculae septomarginalis

Left Atrium- openings

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6 pulmonary veins- 2 from left, 4 from right
small coronary veins
left AV orifice-> LV

Muscular IV Septum- 2 components

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Thin membranous portion- site of closure of IV foramen

Thick muscular portion

Right Ventricle
-blood from where to where
-valves
Right ventricular cavity(3)

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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?

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Conus arteriosus

R Atrium
openings (4)
Azygous veins

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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

Lectures 1-3 Flashcards

(41 cards)