Exam 2: Cardiac Muscle Flashcards
Unique structure of cardiac muscle:
intercalated discs
- cardiac muscle cells have one to two nuclei that are centrally located
- they are striated and use the sliding filament mechanism to contract
- They are branching cells with intercalated discs with desmosomes and gap junctions. The gap junctions are critical to the heart’s ability to be electrically coupled.
- they have large mitochondria that produce the energy needed and prevent the heart from fatiguing
- The node cells have the ability to stimulate their own action potentials. This is called automaticity or autorhythmicity.
- The absolute refractory period is about 250 ms. This prevents tetanic contractions which would interfere with the heart’s ability to pump.
Characteristics of the heart
- Spontaneous
- Gap junctions
- e.g., Vertebrate heart
- Pacemaker
- Cells that depolarize fastest
- Unstable resting membrane potential
Myogenic
- Excited by neurotransmitters
- e.g., Vertebrate skeletal muscle
- Can have multiple (tonic) or single (twitch) innervation sites
Neurogenic
What is the SA node?
the “pacemaker” of the heart
Pacemaker cells-transmit their electrical signal throughout the heart and cause other cardiomyocytes to .
depolarize and contract
Unstable resting potential due to an unusual ion channel, the funny channel or f-channelà permeable to both Na+ and K+
- Open-Na+ influx and K+ efflux leads to slow depolarization
- Reaches threshold-Ca++ voltage-sensitive channels open
- Hyperpolarization reactivates f-channels.
understand the anatomy of the human heart.
a double walled sac covering the heart
Pericardium
is loose and superficial
Fibrous pericardium
is deep to the fibrous pericardium and composed of two layers
Serous membrane
Next to heart; also known as the epicardium
Visceral pericardium
Outside layer that lines the inner surface of the fibrous pericardium
Parietal pericardium
Serous fluid fills the space between the layers of pericardium
pericardial fluid
Layers of the heart:
- Outside layer
- This layer is the visceral pericardium
- Connective tissue layer
Epicardium
The general route of the blood through the body
- Four valves
- Atrioventricular (AV) valves—between atria and ventricles
- Bicuspid (mitral) valve (left side of heart)
- Tricuspid valve (right side of heart)
- Semilunar valves—between ventricle and artery
- Pulmonary semilunar valve
- Aortic semilunar valve
- Atrioventricular (AV) valves—between atria and ventricles
The right and left (mitral) AV valves are normally during diastole and during systole.
- open
- closed
