A&P Test 4 Flashcards
How are cardiac cells set up that is similar to smooth muscle?
Connected via gap junctions
where are gap junctions within the heart?
on the borders of heart cells
how are the borders of the heart cell different than in other areas of the body?
they are convoluted/curvy. This allows for an increase in the number of gap junctions by increasing surface area
Because the transmission of impulses in the heart is so important, it has way more gap junctions than are really ________
necessary
what is the term that is used to describe the high surface area connecting point between 2 cells in the heart? This term is only used in the heart
intercalated disc
the heart muscles have what kind of pattern and why?
striated- alternating dark and light bands
because of the way myosin and actin are oriented
How many nuclei does one cardiac muscle cell have?
1
which muscle is multinucleated?
only skeletal muscle
a sarcomere in the heart looks like the sarcomere in the
skeletal muscle
stem cells in the heart can repair and replace damaged tissue but does this very ______
slowly
if someone could figure out how to increase heart cell proliferation quickly they would be
rich and famous
fibroblasts are what?
cells that are able to lay down scar tissue.
if the stem cells in the heart are overwhelmed what happens?
fibroblasts come in and lay down scar tissue
what happens when you have fibroblasts laying down scar tissue that isn’t necessary?
it can lead to congestive heart failure
excessive scar tissue messes with the_____
Why?
electrical transduction system within the heart.
scar tissue doesn’t connect to other cells in the same way like through Gap junctions so the scar tissue doesn’t contract with the rest of the muscle
what drug do you give to prevent unnecessary scar tissue in the heart? (this leads to HF)
ACE inhibitors
how do ace inhibitors work?
block angiotensin 1 from turning into angiotensin 2.
if you’re pregnant you don’t want to be around what drugs that are used for the heart? why?
ace and arbs
they mess with growth and development via blocking angiotensin 2 and could harm the baby
syncytial or syncytium connections are what?
the arrangement of heart muscle
This refers to how they are able to act as a unit while maintaining their individuality
ventricular muscle is designed how?
2 different layers that squeeze in different directions. They squeeze and twist “ringing” out like a wet towel. Helps pump blood out at high pressure. It is highly efficient.
what is the top half of the heart?
both atria
what is the lower half of the heart?
below the AV node.
both ventricles
sometimes the syncytial connections refer to what?
top or bottom half of the heart
muscle tissue achieves a lot of force by
having a lot of myofibrils and sarcomeres within each muscle cell
conduction tissue doesn’t really produce any
force
conduction tissue does not have any ____ in them. Why?
myofibrils.
They are specialized to send AP quickly and need a big space to do so. They are the same size as a cardiac muscle fiber but they are wider by removing all of the inside “stuff”
how do we describe the layers of the heart?
endocardium-
1 layer thick endothelial layer
Myocardium: deep cardiac layer that makes up the myocardium bulk of cardiac muscle wall
epicardium. most superficial.
major blood vessels are superficial to the epicardium
pericardial space filled with mucus and fluid -prevents friction during contraction
Pericardium: a connective tissue sac that encloses the heart
parietal pericardium (inner layer)
fibrous pericardium (outside layer)
what is almost as bad of a pain as a bad heart attack?
friction within the cells of the heart. This happens by inflammation of the heart or loss of the fluid/mucous in the pericardial space
what are the two layers of the pericardium?
parietal pericardium- stretchy
fibrous pericardium- stiff like leather. difficult to expand.
What is the subendocardium?
that is the muscle layer very very deep in the wall of the heart either deep in the myocardium or within the endocardium
where are MI going to happen? Why?
deep in the cell well (subendocardium)
d/t there being more pressure deep in the wall of the heart
the heart under normal conditions when relaxed, is not relaxed to an _____ degree?
optimal
the heart us usually a little under stretched
what is the conduction tissue within the ventricular muscle?
Purkinji fibers
what is the resting membrane potential of the Purkinje fiber?
-90
what is the plateau phase?
an extension of the action potential
at rest, the purkinje and ventricular muscle tissue is going to be slightly more permeable to_______ compared to other muscles
sodium
because the heart is more permeable to Na+ it has the potential to
spontaneously depolarize
why is the resting membrane potential in the heart drawn at a slope?
because Na+ is leaking in making the cell more positive over time
the rate at which the purkinje fibers are depolarizing on their own takes ____________ therefore,
“forever”
an AP upstream (pacemaker) takes care of depolarizing the purkinje fibers
like in a complete heart block at the AV node:
if there isn’t an AP from the nodal tissue in the heart, the Purkinje fibers has the ability to____________
self depolarize after a longer period of time.
how long does it take for the Purkinje conduction system in the ventricular muscles to finally contract for the first contraction after a block?
30 + seconds
the reflex for the manipulation of muscles in the eye socket is called the
V + X
(five and dime)
it operates with pressure sensors in the eye socket
trigeminal nerve is nerve number
Vagus nerve is nerve number
V 5
X 10
if you poke around in the eye the patient’s heart rate can go down to ______ but then it comes back up after about ______
0
30 seconds
How many distinct phases are there in ventricular tissue?
5
4, 0,1,2,3,
phase 4 in the cardiac action potential is
resting membrane potential drawn at a slope d/t Na+ leaking in
What starts an action potential in the heart?
Na+ coming in from the cells that’s immediately upstream via gap junctions
phase 0 in the cardiac action potential is
rapid Na+ upstroke. Fast Na+ channel dependent.
when do K+ channels close? (A&p)
during a fast action potential from the end of phase 0 through phase 1 and 2
phase 1 in the cardiac action potential is
fast Ca++ current through T type Ca++ channels
phase 3 in the cardiac action potential is
slow L type Ca++ channels closing and K+ channels opening
length of cardiac AP is much ______ than skeletal muscle and neurons
longer
how long is the cardiac action potential?
Why is this helpful?
200ms
It allows the heart to have time to have a coordinated contraction.
The length of time that a slice of tissue is going to be contracting is shown in what part of the action potential graph?
phase 2
under no circumstances will K+ go
inside the cell
why doesn’t the cardiac cell get more positive in phase 2?
the proportion of Ca++ channels opening and K+ channels closing is no where near the amount of Na+ current that comes in during phase 0-1
what is the abbreviation for current?
i
ohms law is
V=IR
voltage is dependent on current crossing over a resistance
what does ionic current depend on?
how many ion channels are opened
electrochemical gradient of those ions
angiotensin 2 besides being used in the RAAS system, is an important __________ that a log of things in our body depend on.
growth factor
fibroblasts are kind of controlled by how much activity the
angiotensin 2 system has in the heart.
phase 2 in the cardiac action potential is
The end of T type fast Ca++ channels being open and the beginning of slow L-type Ca++ opening
Purkinje conduction system and the ventricular muscles threshold potential is
-70
The pressure that sensors detect in the eye socket takes what route to decrease the HR?
Sent to the CNS through trigeminal nerve (nerve V) found on the side of the face
goes to
brainstem and brainstem sends info via the
vagus (nerve X) nerve which prevents transmission of action potentials at the AV node
what is the resting membrane potential of the ventricular muscle tissue?
-80
