Lecture 10/14: Cardiac Flashcards
Test 4
What type of muscle is cardiac muscle?
Visceral/unitary smooth muscle
Cardiac muscle contracts as a _______
unit
Describe the borders of cardiac cells
They are called intercalated discs
The are convoluted to increase surface area to allow for more gap junctions
Where are intercalated discs?
ONLY IN THE HEART
How many nuclei do cardiac cells have?
1
What does the striation pattern represent?
actin & myosin
Cardiac & ______ sarcomeres are similar
skeletal
What is the role of stem cells in cardiac muscle?
SLOWLY fix other cells that die off
_______ cells lay down scar tissue
Fibroblasts
What happens if stem cells get overwhelmed?
Fibroblasts will lay down scar tissue
What is a condition where fibroblasts unneccessarily lay down scar tissue? How does this affect the heart? What medication can we give to combat this?
CHF
Scar tissue doesn’t contract normally and it disrupts the electrical transduction system of the heart
ACE inhibitors (-prils)
What is an important growth factor in our body?
Angiotensin 2
Why do you NOT want to take ACE inhibitors or ARBs while pregnant?
They block RAA system and angiotensin 2 is an important growth hormone factor. Blocking angiotensin 2 would prevent the proper development of the fetus.
ACE inhibitors has what effect on after load?
reduces after load
Describe the different types of Syncytial connections
“Syncytiums”
- Referring to 2 ventricular layers (endocardium & epicardium) oriented in 2 different directions.
-This allows for a twisting mechanism to get blood out of the ventricles (like twisting water out a towel) - Top/Bottom of heart referring to atria = top & ventricles = bottom
What is the vast majority of cardiac cells?
Muscle tissue
Why is the heart able to produce so much force?
The vast majority of the heart is a muscle tissues. It’s has lots of myofibrils in muscle cells to produce force from action potentials.
Describe Conduction tissue
Transmits AP faster than muscle tissue bc it doesn’t have myofibrils (slows down AP)
Doesn’t produce much force
What are the layers of cardiac muscle from deep to superficial?
Endocardium
Myocardium
Epicardium
Pericardial space
Parietal pericardium
Fibrous pericardium
What are the layers of cardiac muscle from superficial to deep?
Fibrous pericardium
Parietal pericardium
Pericardial space
Epicardium
Myocardium
Endocardium
The ______ endocardium layer is the ________ cardiac muscle
Thick
Deepest
What layer makes up the bulk of the cardiac muscle wall?
Myocardium
What does the pericardium consist of? Describe them
connective tissues that from a sac and enclose the heart
- Pericadial space: fluid/muscous filled area; reduces friction with beating and moving of heart
-Superior to the epicardium - parietal pericardium: inner area; closest to pericardial space; easily expands
- fibrous pericardium: outer area; stiff & difficult to expand.
T/F: Alot of extra fluid can fit in the pericardial space
F
Fibrous pericardium is stiff and difficult to expand
What helps reduce friction in the pericardium?
Fluid/mucus in the pericardial space
You think you’re having a heart attack… What could this be?
Friction in the pericardium d/t inflammation or loss of fluid/mucus in pericardial space
Where is the subendocardium?
Deep Endocardium or deep myocardium
Where do infarcts/MIs normally happen? Why?
Subendocardium in L ventricle
Ventricular wall pressures are highest here
Cardiac sacromeres are naturally _________ the actin & myosin _________
under stretched
slightly overlap
Myosin touches Z-disc
What is the Vrm of the purkinje fibers?
-90 mV
What is the threshold potential of the purkinje fibers?
-70 mV
What is the Vrm of the ventricular muscles?
-80 mV
What is the conduction system within the ventricles?
Purkinje fibers
T/F: Purkinje fibers contract
F
T/F: Purkinje fibers are last to fire an AP
T
Rate of conduction is very slow; before they are depolarized, another area in the heart (SA/AV node) has already fired another AP
Whats the difference between Ventricles and purkinje fibers?
Ventricles: permits AP and contracts in response
Purkinje: permits AP only
How long does it take for purkinje fibers to fire 1st AP after escaping from complete heart block?
30 seconds
Subsequent ones dont take this long
What is a lag?
Time is takes to get from Vrm to threshold potential
Why is there a slope at phase 4 in the ventricles?
Increasing permeability to Na+ at rest
Describe how eye procedures cause heart blocks
Pressure sensors in the eye trigger reflexes from manipulation –> V & X reflex = 5 & dime reflex
pressure into is sent to CNS from cranial nerve-V (trigeminal nerve on the side of the face) which is then sent to cranial nerve-X (vagus).
This causes massive vagal output from CNS
HR may go to 0 but Purkinje fibers should kick in at about 30 seconds
What should we be cautious of in eye procedures?
People with heart problems
5 & dime reflex
Need to take extra precatious
What is a ventricular muscle cell?
Ventricular myocyte
Ventricular AP: Describe phase 4
Resting
Small slope d/t increasing Na+ permeability
Ventricular AP: When are K+ channels closing?
Phase 0-2
Ventricular AP: Describe phase 0
Rapid upstroke
Fast Na+ channels open/close
Ventricular AP: Describe phase 1
Fast T-type Ca++ channels open
Ventricular AP: Describe phase 2
Plateau phase
Slow L-type Ca++ channels open (takes over from T-type Ca++)
Ventricular AP: Describe phase 3
K+ channels open
Ventricular AP: Where is the Na+ coming from?
Cells immediately up/down stream via gap junctions
Ventricular AP: How long is the AP? Why?
200 milliseconds
allows for coordinated contractions betweens syncytiums
What is Holmes law?
Voltage (V) = Current (I) x Resistance (R)
Ventricular AP: Where are K+ channels open?
Phase 3-4
