exam 4 Flashcards
term to describe the cardiac muscle
syncytium
atrial and ventricular
cell membranes that separate individual cardiac muscle cells from one another
intercalated discs
curvy cell boarders allows for more surface area/gap junctions
cardiac centric term
sagital
left vs right
vertical
front vs back
limb leads
axial
top vs bottom
unipolar leads
precordial
what muscle is multinucliated
skeletal muscle
another name for smooth muscle
how it contracts
visceral (unitary) contractions
what lays down scar tissue in the the heart
fibroblasts
- controlled rate
- occurs in CHF
what medication slows down fibroblast activity
ACEi
- angiotensin 2 is a growth hormone
- no ACEi or ARB in pregnancy
whats majority of the heart muscle
myofibrils
what does conduction tissue not have
myofibrils
need to send action potentials quickly
layers of the heart
endocardium
- deep one layer thick
myocardium
- bulk of muscle
epicardium
- superficial
major blood vessels on top
pericardial space
- low mucus, little water
pericardium
- connective tissue sac
- visceral: thin/stretchy/clear
- parietal: physically attached to fibrous pericardium. partial pain = tissue
- fibrous… similar to dura in CNS
what term normally describes the LV
subendocardium
- deep within the endocardium and myocardium
- MI
how to heart muscle squeeze
2 layers
perpendicular
what does the heart look like when relaxed
a little under strectched
actin filaments overlap
no H band
how does muscle contract
myosin moves to Z disk
purkinje
RMP and threshold
threshold -70
RMP -90
don’t contract, just send action potentials
ventricle
RMP and threshold
threshold -70
RMP -80
how long does it take for the first action potential for AV block
30+ seconds
CHB reflex for eye procedures
five and dime
- cranial nerve 5 (trigeminal)
- vagus
- prevents action potential transmission at the AV node
fast action potential phases
4: slight slope
- not many HCN, Na/Ca leak channels
0: fast Na+
-via gap junctions coming from upstream
1: fast T-type Ca+
2: slow L-type Ca+
K+ closes end phase 0 -> end phase 2
K+ opens end phase 2 -> 3
how many milliseconds of a fast action potential
200 milliseconds
ohms law
voltage= ionic current x resistance
slow action potential phases
4: HCN, Ca+ and Na+ leak channels
0: L-type Ca+
3: L-type Ca+ close
voltage gated K+ close
threshold: -40
VRM: -55
AV node VRM compared to SA
less HCAN, leaky Na+ and Ca+
lower VRM
lower HR
what does HCN stand for
ions
hyperpolarized and cyclic nucleotide medicated channels
open when VRM reached (repol. or hyperpol)
Na, Ca, K
calcium effects on threshold
high calcium
- increase threshold
- decrease HR
only works in cardiac tissue
what phase do some books say the slow act potentials have
phase 2 “platue”
beta agonist
increase adenyl cyclase
increase CAMP
more HCN channels open, same VRM
Beta antagonist
atenolol
less HCN channels open
reduced phase 4
MACh-R
inhibitory alpha subunit
lower adenyl cyclase
lower CAMP
more K open
lower VRM
lower HR
potassium effects
increase VRM
increase HR
REALLY HIGH
- reduces conduction speed
- loose Na+ and Ca++
refractory period
stimulation before cell is rest
can see or not see an action potential
relative refractory period
cell reset enough to produce a weaker action potential
absolute refractory period
can’t regenerate an action potential
HR if no vagus/SNS
110
HR if SNS
120
HR if vagus
60-62
AV node HR
40-60
Perkinji HR
15-30
pathway from SA to AV
internal pathway
anterior
middle
posterior
pathway of SA to LA
interatrial
Bachmens bundle
- comes off the anterior internodal pathway
p wave time
0.09 seconds
SA to AV time
0.03 seconds
SA to posterior lateral RA
0.07 seconds
SA to bottom LA
0.09 seconds
what causes the AV node delay
decreased gap junctions
fat
PR interval
0.16
SA -> bundle branches
