The Neuromuscular Junction

Question 1

What is the synapse?

Answer 1

The junction where an action potential (electrical signal) is transmitted from one neuron to another or from a neuron to a muscle.

Question 2

Why is the synapse crucial?

Answer 2

for neural communication and execution of bodily functions.

Question 3

Briefly name the 5 steps of how neurons communicate.

Answer 3

1. Action potential initiation.
2. Transmission Across the synapse.
3. components of a synapse.
4. One-way transmission
5. Role of neurotransmitters

Question 4

Describe the action potential initiation.

Answer 4

The communication between neurons begins with an action potential travelling along the axon of the first neuron (presynaptic neuron) until it reaches the axon terminals.

Question 5

describe the transmission across the synapse.

Answer 5

The synapse is where the action potential is transmitted from the axon terminals of the presynaptic neuron to the dendrites or soma of the postsynaptic neuron.
Chemical synapse is the most common type, where the electrical signal is converted into a chemical signal at the synapse and back into an electrical signal in the postsynaptic neuron.

Question 6

What are the components of a synapse.

Answer 6

1. Presynaptic terminals - the ends of the axon where neuro transmitters are stored in synaptic vesicles.
2. Synaptic cleft - the narrow gap between the presynaptic terminals and the postsynaptic receptors.
3. postsynaptic receptors - located on the dendrites or soma of the postsynaptic neuron, where neurotransmitters bind to receptors on the postsynaptic neuron.

Question 7

What is the role of neurotransmitters?

Answer 7

Neurotransmitters are chemical compounds released by synaptic vesicles in response to an action potential. The diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic neuron.
If sufficient neurotransmitters bind to the postsynaptic receptors, it causes a depolarization, potentially leading to a new action potential in the postsynaptic neuron

Question 8

What is the neuromuscular junction?

Answer 8

It is a specialized synapse where a motor neuron communicates with a muscle fiber, leading to muscle contraction.

Question 9

What are the 3 steps in the neuromuscular junction?

Answer 9

1. Action potential at the neuromuscular junction.
2. Depolarization and muscle contraction.
3. Repolarization and refractory period.

Question 10

Describe the action potential at the neuromuscular junction.

Answer 10

When an action potential reaches the axon terminals of a motor neuron, it releases neurotransmitters (primarily acetylcholine, ACh) in the synaptic cleft.

Question 11

Describe depolarization and muscle contraction.

Answer 11

1. ACh binds to receptors on the muscle fiber’s plasmalemma (cell membrane), causing sodium ion channels to open and sodium ions to enter the muscle fiber, leading to depolarization.
2. If this depolarization reaches the threshold, an action potential is generated, spreading across the muscle fiber and initiating contraction.

Question 12

Describe repolarization and refactory period.

Answer 12

After depolarization, the muscle fiber undergoes repolarization, during which it cannot respond to another stimulus, limiting the firing frequency of the motor unit.