Sliding Filament Theory and Proprioceptors

Question 1

Whole Muscle

Answer 1

Made up of bundles of fascicles

Question 2

Fascicle

Answer 2

Made up of bundles of muscle fibers

Question 3

Muscle Fibre

Answer 3

Made up of bundles of myofibrils. Muscle fibers are usually the diameter of a human hair

Question 4

Myofibril

Answer 4

Made up of bundles of myofilaments. Myofibrils are about 1/100 the diameter of a hair

Question 5

Myofilaments

Answer 5

• Made up of actin (thin) and myosin (thick) protein threads.
• About 1/10,000 the diameter of a hair
• Arranged in sections called a sarcomere.

Question 6

Sarcomere

Answer 6

The smallest contractile unit of skeletal muscle

(In a relaxed muscle there are about 4500 sarcomeres per cm of muscle length)

Question 7

Z discs/lines

Answer 7

The boundaries of the sarcomere

Question 8

Actin

Answer 8

• Filaments are attached to the Z discs/lines.
• Actin is a protein and it is thin

Question 9

M-Line

Answer 9

Where adjacent myosin
filaments attach to each other.

Question 10

Myosin

Answer 10

• Filaments are attached
  to the M line.
• Myosin is a protein and is roughly twice the thickness of actin

Question 11

Concentric Contraction

Answer 11

• Muscle fibers shorten
• Origin and insertion move
  closer together

Question 12

Eccentric Contraction

Answer 12

• Muscle fibers lengthen
• Origin and insertion move
  apart

Question 13

Isometric Contraction

Answer 13

• Muscle fibers do not change in length
• Origin and insertion don’t move

Question 14

Crossbridges

Answer 14

• Form when the myosin heads attach to actin
• The action of myosin cross bridges pulling on the actin filaments is responsible for movement of the actin filament

Question 15

What dictates the force production of a muscle?

Answer 15

The number of crossbridges that are formed between actin and myosin at any instant in time

Question 16

What happens when when more actin and myosin overlap?

Answer 16

Force production of a muscle is increased

Question 17

What happens when when less actin and myosin overlap?

Answer 17

force production of a muscle is decreased

Question 18

Proprioceptors

Answer 18

• Sensory receptors located in joints, muscles and tendons
• They provide information to the body on muscle length and muscle tension.

e.g
* Muscle spindle (located in the belly of the muscle)
* Golgi tendon organs (located in the tendon)

Question 19

Muscle Spindle

Answer 19

• Provides information on muscle length.
• When a muscle is stretched, muscle spindles cause contraction of the stretched muscle to prevent injury.

Question 20

Golgi Tendon Organ

Answer 20

• Provides information on muscle tension
• When a muscle is under excessive tension, GTOs cause a reduction in tension to prevent injury.