edexcel Sliding Filament Theory

SFT

• There are 4 main stages to muscle contraction

• 1. Detachment

• 2. Hydrolysis

• 3. Cross Bridge

• 4. Power Stroke

Multiple Choice

What does the sliding filament theory explain?

• How muscles contract at the molecular level

• How muscles grow in size

• How muscles generate heat

• How muscles store energy

Multiple Choice

Thick filaments within a myofibril are:

• ATPase

• Sarcoplasmic reticulum

• Actin

• Myosin

Multiple Choice

Thin filaments in a myofibril are

• Sarcomeres

• Sarcoplasm

• Actin

• Myosin

Multiple Choice

The energy needed to perform a muscle contraction comes directly from

• ATP

• Oxygen

• Glucose

• Calcium

Multiple Choice

The neurotransmitter stored in the axon terminal identified as #3

• Calcium Ion (Ca²⁺)

• Protein Channel

• Acetylcholine

• Synaptic Cleft

Multiple Choice

The gap between a neuron and a muscle cell: (#4 in the diagram)

• synaptic cleft (synapse)

• sarcolemma
• vesicle
• Ca²⁺ ion

Multiple Choice

The plasma membrane of a skeletal muscle cell is called the:

• sarcomere
• myofilament
• sarcolemma
• sarcoplasm

Multiple Choice

What state is the sarcomere in #1

• Relaxed
• Contracting
• Fully Contracted
• None of the above

Multiple Choice

What state is the sarcomere in #2

• Relaxed
• Contracting
• Fully Contracted
• None of the above

Fill in the Blanks

During Action Potential an influx of calcium ions are produce which then bind with

?

Multiple Choice

What are the repeating units called in myofibrils?

• Muscle fibers

• Sarcomeres

• Cylindrical structures

• Myofibrils

Fill in the Blanks

The myosin heads bind to the exposed myosin-binding sites on

, causing the actin filaments to slide over the myosin filaments in a power stroke.

Fill in the Blanks

ATP is required for the myosin heads to detach from actin, and myosin hydrolyzes ATP to ADP and Pi to return to its

position.

Multiple Choice

What triggers the release of calcium ions in muscle contraction?

• Action potential

• Troponin

• Tropomyosin

• Myosin-binding sites

Fill in the Blanks

The cross-bridge cycle repeats as long as

ions are available, resulting in the shortening of the sarcomere and muscle contraction.