* Motor Units

What is required for skeletal muscle to contract?

• A) A chemical impulse from the digestive system

• B) An electrical impulse from the central nervous system

• C) A mechanical impulse from the skeletal system

• D) A thermal impulse from the circulatory system

Match the following terms with their descriptions:

• The connection between a nerve and muscle

• A) Motor unit

• The motor neuron and its muscle fibers

• B) Muscle junction

• Gap between the motor end plate & muscle

• D) Neurotransmitter

• A chemical messenger

• C) Synaptic Cleft

What is the role of acetylcholine (ACh) in muscle contraction?

• A) It blocks the nerve impulse

• B) It helps the nerve impulse cross the synaptic cleft

• C) It deactivates the motor neuron

• D) It strengthens the muscle fibers

What happens if the electrical charge is above the threshold?

• A) The muscle fiber will not contract

• B) The muscle fiber will contract

• C) The muscle fiber will relax

• D) The muscle fiber will become inactive

What is the 'all-or-none law' in muscle contraction?

• A) All muscle fibers will contract partially

• B) All muscle fibers will contract completely or not at all

• C) Only some muscle fibers will contract

• D) Muscle fibers will contract in a graded manner

Match the following parts of a neuron with their functions.

• junction between two neurons

• dendrites

• transmits information to other neurons

• axon

• receives information from other neurons

• synapse

• insulates and speeds up neural impulses

• myelin sheath

Gaps in the myelin sheath are called this.

• Nodes of Ranvier
• Axon terminals 
• Synapses
• Neurotransmitters