Lecture 2 theme B Flashcards
What are the types of hypertrophy the heart can experience?
Physiological hypertrophy is reversible.
Pathological hypertrophy results in fibrosis and leads to a deficient capacity for heart cell to pump blood.
How does the ventricle contract?
Ventricle contracts from the bottom to up direction.
What are the components of cardiomyocytes that allow them to communicate?
cardiomyocytes contain intercalated disks. These disks contain desmosomes and gap junctions
What are the components of a cardiac myocyte?
striated with nulei, mitochondriae, intercalated disks
What is the function of the desmosomes of the intercalated disk?
Transfer force from one cell to another (end to end)
What is the function of gap junctions of the intercalated disk?
allow ion movement from cell to cell which allows rapid spread of electrical signal.
How big is a cardiomyocyte?
about 100 microns long and about 20 microns wide
What is the length-tension relationship like in the cardiomyocyte?
Cardiomyocytes exhibit length-tension relationship. However, they are always on the ascending part of the curve.
What do end diastolic volume and stroke volume indicate about the ventricle?
End diastolic volume determines how stretched the ventricle is. Stroke volume shows how strong the contraction is.
Why is the sarcoplasmic important for cardiomyocytes?
Calcium is important for contraction and it is stored in the sarcoplasmic reticulum.
What is the difference in cell composition between cardiac myocytes and skeletal myocytes?
Skeletal muscles are almost entirely composed of myofilaments (84% of volume) with less mitochondria and sarcoplasmic reticulum.
Cardiac muscles contain 50% myofilaments and 35% mitochondria.
What are the steps involved in excitation-contraction coupling?
- calcium enters cell during AP plateau
- Triggers calcium release from SR
- Ca binds to troponin
- Cross-bridge cycling
- Cell shortens
- Most calcium is pumped back to the SR
- Some calcium exits cell by Na-Ca exchanger and Ca pump on sarcolemma
How is calcium returned to the SR?
most calcium is returned to the sarcoplasmic reticulum by SERCA.
What are the differences between skeletal muscle and cardiac musle?
skeletal muscles require many spikes of action potentials to create a contraction. Cardiac muscle is modulated by one peak.
Excitation occurs in skeletal muscle to a motor unit at a time, cardiomyocytes rely on gap junctions which spread the action potential.
Skeletal muscle rely on AP frequency and summation to modulate force. Cardiomyocytes rely on calcium entry.
Skeletal muscles rely on oxidative and glycolytic metabolism whereas cardiac cells rely on oxidative metabolism only.
What is the different response observed by the L-type receptor in skeletal muscle cells and heart cells?
excitation of skeletal muscles relies on L-type channels. In skeletal muscle no calcium flows through this channel. In heart cells 15 - 20% of the activator calcium flows through this channel.
