name two pecularities of cardiac muscles?

Answer 1

- All-or-none Law of cardiac muscle: When 1 cell contracts, they all contract in all or none fashion.

The refractory (recovery period before contraction can happen again) period is long: 300msec
(lasts as long as the contraction itself).

Longer contraction period (300msec for cardiac vs. 100msec for skeletal muscle).

Cardiac cells cannot be stimulated to contract again until the previous contraction is almost over.

Has large amounts of mitochondria & depends on a larger supply of oxygen for its metabolism than skeletal muscle.

Some cardiac muscle cells (SA, AV node, AV bundle, & Purkinje fibers) are self-excitable and can initiate their own depolarization
Results from the fact that cell membranes of these cardiac cells are more "leaky" than those of skeletal muscle.
Can trigger rhythmic beating without any nervous stimulation.

The ability of the heart muscle to depolarize and contract is intrinsic (inside heart), that is, it is a property of the heart muscle itself and does not depend on extrinsic (outside heart) nerve impulses. In fact, even if all nerve connections to the heart are severed, the heart will continue to beat.

Answer 2

1) Cardiac muscles are not voluntarily controlled (i.e. we don't have to "think" about contracting our heart muscles to pump blood through our bodies and we can't stop them from contracting whenever we might feel like trying). The insisent contracting / relaxing of our hearts doesn't even require a signal from our brain to function (although our brain CAN signal the heart to slow down or speed up); the basic heartbeat is essentially built-in the actual muscle tissue. This phenomenon is witnessed every year by many horrified high school biology students as it is not uncommon to remove a beating heart from a frog that is being disected; in fact, a beating heart can be kept "alive" and will continue beating for quite a few minutes given proper treatment and fluids.

2) For greatest efficiency, cardiac muscles contract and relax in unison. Bring together two samples of "living" cardiac tissue that are beating at different rates (or are beating out of phase with the other) - after a very short time they will automatically "synchronize" and beat as a unit instead of individual pieces.

Answer 3

Involuntary contraction
Its building blocks are cells with one nucleus compared to skeletal muscle fibers which are fusions of many cells and thus have multiple nuclei in a syncytium.

Answer 4

Automaticity
Conductivity
or/and
Contractabilty

Answer 5

Excitability and contractibility

Answer 6

they have "automaticity" i.e. they contract on their own
they have some recepor cells that other muscles do not

Answer 7

Uhh...they're working all the time?

Answer 8

THEY ACCEPT ALL THE ABUSE WE GIVE THEM AND THE KEEP ON PUMPING.STRESS THEM AND THEY WORK BETTER