Muscle contraction
نص القصة المصورة
- الانزلاق: 1
- Hey Sam, I'm having some trouble with understanding muscle contraction.
- ....Really? Alright Chad. I will explain to the best of my abilities.
- الانزلاق: 2
- So the brain's the boss?
- Alright, Chad. Muscles don’t work on their own. They need instructions from the nervous system.
- Exactly! The brain sends a signal to the muscle through a neuron, and that signal is called an action potential
- الانزلاق: 3
- The action potential travels down to the neuromuscular junction(NMJ) – where the neuron meets the muscle.
- The NMJ consists of the synapse, the connection between the neuron and muscle cell.
- And that's what makes the muscle contract?
- Not quite yet. This is just the start!
- الانزلاق: 4
- When the action potential reaches the end of the neuron, voltage-gated calcium channels open, letting calcium enter
- Voltage what?...
- voltage gated channel, its a channel that only opens when the electric charge reaches a certain level from the action potential.
- الانزلاق: 5
- so calcium gets things moving?
- Exactly!
- it triggers the release of a neurotransmitter, a chemical by which signals are moved across the synapse.
- In this case, that neurotransmitter is the acetylcholine(ACh)
- الانزلاق: 6
- ACh moves through the synapse and binds, to receptors on the muscle cell
- When ACh binds, chemically gated channels open and allow sodium in and potassium out.
- And that exchange of sodium and potassium creates an action potential in the muscle, right?
- Yes and that's what makes the muscle finally contract.
- الانزلاق: 7
- So? Do you understand?
- Hmm... I already forgot.
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