I have to say, I was a bit daunted by your post. But after slogging through cardiac action potential and its various phases, the potassium channels, arrhythmia, calcium channels, etc., I think I have a handle on your question. It may not be as detailed as you may like, but I'll try my best.
Nerves are not involved in generating heartbeat, FYI. It is the leaky sodium ion channels housed in the plasma membranes of auto-rhythmic cardiac muscle cells that "generate" action potentials/electric impulses which translate as heartbeat when they are received by cardiac muscle.
Forgive my ignorance. It's been awhile since I've read up on the heart.
I just want to highlight the fact (and this cannot be denied) that action potential will not be produced if one of the parts does not exist/cooperate.
Action potential is the passage of ions through the cell membrane. Although the membrane is semi-permeable, the cell membrane prevents the diffusion of polar solutes across the membrane. This gives the cell the control of movement through the membrane through the pores and gates. Now the ion channels are essentially proteins formed into pores that can control the passage of the small voltage gradient. Wouldn't it be logical to think that a small mutation would have changed some of the pores that allowed some substance to pass through a transmembrane protein into a pore that allowed ions to pass through? And assuming that it provided an evolutionary advantage, it wouldn't be illogical to think that cells would begin to carry this mutation over time.
Whatever the original evolutionary advantage was for action potential, there is an added advantage as it relates to communication between cells. Consider that the first single-celled organisms that grouped together needed a way to communicate, action potential offered a ready option. Communication by action potential is quick, about 1/3 the speed of sound, compared to using alternative methods. For multi-cellular organisms, the evolutionary advantage of action potential in intercellular communication is too great to ignore, which is why nearly all multi-cellular organisms use action potential as a means of communication between cells.
Now, going back to the heart, here are some differences I’ve gathered that make heart muscle structurally and functionally different from skeletal muscle...
First, skeletal and cardiac muscles are very similar with regards to striations and contractions. The primary structural proteins of both skeletal and cardiac muscles are actin and myosin. The difference is that cardiac muscles may be branched rather than linear and longitudinal. Like skeletal muscles, cardiac muscles initiate action potential through the entry of sodium ions across the sarcolemma. Cardiac muscles, however require extracellular calcium ions for contraction to occur. The point is that skeletal muscle and cardiac muscle are similar and cardiac muscle can be seen as the intermediate between skeletal muscle and smooth muscle. In fact, it may be that cardiac muscles are the next evolutionary step between skeletal and smooth muscle but that's just my own thoughts there.
Difference 1. Unlike skeletal muscle cells , heart muscle cells have leaky sodium channels
Ramification 1. Heart muscle cells generate their own action potential rhythmatically
Do you mean "leaky" potassium channels? You never mentioned "leaky" sodium channels.
I'm sorry, I don't see how "leaky" potassium channels create the heart's rhythm. The rhythm of the heart (here, I'm assuming you mean heartbeat) is set by the pacemaker cells which are typically the cells that undergo depolarization the fastest, right? Those cells are typically found in the SA Node, right?
Difference 2. Unlike skeletal muscle, heart muscle cells have less extensive Sarcoplasmic Reticulum and no Cisternae. (for clarification, SR stores and releases Ca++, and Cisternae are balls of SR filled with Ca++)
Ramification 2. Responsible for slow onset of contraction and prolonged contraction phase
This is what you might find if you conjecture that cardiac muscles evolved from smooth muscle. Smooth muscles do not rely on action potential for contraction. Because smooth muscles are ill-suited to work as a heart, there is an evolutionary advantage in a mutation that changes smooth muscle into cardiac muscle as smooth muscles contract slowly and may hold the contraction for prolonged periods. More constant, consistent pumping means nutrients are consistently flowing which allows for sustained physical activity. Cardiac muscles evolving into skeletal muscle would be the next step as endoskeletons began to form.
Difference 3. Desmosomes and gap junctions connect heart cells (none of these occur in skeletal muscle)
Ramification 3. If one heart cell generates action potential, eeevery one else gets the message and guess what, all cells contract in unison. (If skeletal muscle was wired in this fashion, we would never be able to make a precise eye muscle movement)
Again, this takes advantage of the fact that action potential is the fastest way for cells to communicate with each other. Compare that with releasing hormones to begin contractions, there is an evolutionary advantage in mutations that allow cardiac muscles to utilize action potential better than it was previously.
These differences collectively add to the one effect: long refractory period. Why do we need a long refractory period anyway? Well, having a long refractory period prevents conditions like tetanus and treppe where multiple successive contractions result in abnormally strong contractions. Therefore, the heart is not susceptible to such conditions.(How can you not call this intelligent design?)
You are essentially saying that God made the heart the way it is to prevent tetanus but I could just as simply ask: why didn't God not create the bacteria that causes tetanus in the first place?
You are also making a logical fallacy by saying correlation implies causation. Just because tetanus is likely prevented by the way our hearts are constructed does not mean that was the reason for why our hearts are the way it is. The fact that the way the heart is might prevent tetanus would just an additional evolutionary advantage, but the more significant advantages are that our hearts allow for sustained activity, more rapid movement, a larger size, and better nutrient transport. Evolution, in fact, accounts for the development of the heart since any mutation of the heart that confers advantages for an organism that other organisms in a population would not have would make that particular organism better fit than the rest and likely more reproductively successful. Thus we have those advantages simply because the mutations created organisms that survived better in their environment.
It does. If there was no programming, there’s no point in having cardiac muscle. We might as well use skeletal muscle in the heart.
I conjecture that smooth muscle gave rise to cardiac muscle. Consider that modern invertebrates utilize smooth muscle, and considering it is the simplest of all muscle groups, it's likely that the earliest invertebrates also utilized smooth muscle. Mutations that gradually changed smooth muscle into cardiac muscles would give certain invertebrates an evolutionary advantage as they could achieve greater size and sustain longer durations of movement as well as more rapid movement.
This is evidence of design. Design demands intelligence and foreknowledge. God is the source of intelligence since nature cannot program itself.
Nature cannot program itself, but that doesn't mean that there is no underlying order to it. Don't confuse apparent chaos to actual chaos; that's a big problem with many creationists. The Theory of Evolution states the underlying order are the mutations that give rise to variations and the environment which determines which variations are of a stronger fitness, weaker fitness, or of a neutral fitness. That means that while there is no plan, there is a method to the madness. It's similar to the weather systems. At first glance, it may seem like chaos but humanity can predict the weather with relative accuracy (weatherman jokes aside) because we perceive the underlying order beneath the apparent chaos. We understand how the water cycle, ocean temperatures, prevailing wind currents, etc all affect the weather. Evolution is similar in that it explains the underlying order beneath the apparent chaos.
The ultimate programmer is God. He does not require a programmer since He is eternal. I argue that without intelligence, intricacy and complexity cannot be attained.
Yet the weather systems are intricate and complex. Did they happen without a creator? Is God out there right now controlling the weather?
Intricate and complex systems can arise out of the interaction of rather simplistic parts. We understand gravity and its effect on mass and force. We understand and inertia and the conservation of momentum. Yet if a strong wind pushes a teetering rock down a mountain, we can't predict which rocks will be dislodged or how each and every rock will fall in a rockslide. A rockslide is an intricate and complex system that arises because of simplistic parts.
My original comment I can’t see how mutations bring about a positive effect was of pure curiosity
Mutations in the genome aren't inherently positive or negative. It's the environment that determines which mutation is of greatest benefit to an organism. Mutations can create the different parts of a heart, but it is the environment the organism with the mutations is in that determines if the mutation is beneficial to the survival and fitness of the organism.
Anthropomorphism is how humans understand and explain inanimate/non-living entities. It is the basis for the ontological argument for the existence of God.
Anthropomorphism may be how the majority of humans understand and explain inanimate/non-living entities, but it has no place in science. Astrophysicists do not attribute intelligence or emotions to Jupiter. Astrophysicists are not saying that Jupiter is where it is because it wants to be there. They describe the forces involved and how they interact to produce a model which describes the orbit of Jupiter. No anthropomophisizing involved. And if anthropomorphism is the ontological basis for the existence of God, then I can see why scientists reject that argument. After all, if I can conceive of a Flying Spaghetti Monster, and I can, does that mean he exists?
As I've written a lot, I'll just conclude here. The parts that you addressed in your post about the heart can be explained by evolution. Ion channels could have easily mutated from channels that processed other materials. While I couldn't tell you the evolutionary advantage for a single celled organism (I could think about it, I suppose), I can tell you that action potential does confer a great advantage for multi-cellular organisms for inter-cellular communication. Mutations in smooth muscles to create cardiac muscles would increase the fitness of an organism as would an adaptation to take advantage of action potential in producing heart rhythms. As you can see, with each successive mutation, the heart has grown more and more complex. This shoots down the idea that complexity and intricacy require an intelligence. All that is required are small changes that produce an advantage in the environment. The Theory of Evolution, in a nutshell, has no difficulty addressing the evolution of the heart.
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