Muscles and Motor control

Question 1

List and describe the characteristics if the three muscle types.

Answer 1

SKELETAL - Long, stated cells. Multinucleated, close to periphery. Moves, stabilises, generates heat and stores nutrients.
SMOOTH - Small, spindle shaped cells with tapered ends. Single, centrally located nucleus. Non-striated. Located in the walls of blood vessels, around hollow organs and linings of most tracts.
CARDIAC - Small, branched cells. Interconnected to other cardiomyocyes via selectively porous junctions. Centrally located nucleus. Striated.

Question 2

Explain how each type of muscle is innervated.

Answer 2

Skeletal - Voluntary

Cardiac and Smooth - Involuntary

Question 3

Describe the physiological properties of muscle tissue.

Answer 3

Muscle tissue has four main properties: Excitability (ability to respond to stimuli), Contractibility (ability to contract), Extensibility (ability of a muscle to be stretched without tearing) and Elasticity (ability to return to its normal shape).

Question 4

Draw a labelled diagram of the neuromuscular junction and summarise the events that occur here.

Answer 4

Normal synapse. Always causes a response. ACh as neurotransmitter

Question 5

Describe how skeletal muscles contract (sliding filament theory).

Answer 5

ATP binds to myosin causing it to detach from actin. ATP -> ADP releases energy to convert myosin heads into the ‘cocked’ state. Calcium binds to troponin which exposes sites on actin that myosin attaches to. Actin-Myosin cross bridge forms. Myosin then completes a power stroke.

Question 6

Define the term motor unit and explain how the size of a motor unit relates to its function.

Answer 6

Motor unit - One somatic efferent neurone and all the muscle fibres it innovates.
Type 1 muscle fibres have small motor units, slow contraction. Endurance. Aerobic
Type 2A muscle fibres have bigger motor units, fast contraction wit a medium force. Medium endurance
Type 2B muscle fibres have large motor units. Fast contraction, high force, low endurance and anaerobic metabolism.

Question 7

Distinguish between muscle fibres and muscles.

Answer 7

A muscle is a collection of muscle fibres

Question 8

Describe the anatomical arrangement of a muscle (muscle fibres, endomysium, perimysium, epimysium etc).

Answer 8

EPIMYSUIM - Dense collagen layer surrounding the muscle, separating it from nearby tissue
PERIMYSIUM - Divides muscles into fascicles. Contains collagen, elastic fibres, nerves and blood vessels
ENDOMYSIUM - Flexible layer inside fascicles. Contains fine capillaries and nerves alimenting each fibre.

Question 9

ORIGIN

Answer 9

Where the fixed end of a muscle attaches to bone

Question 10

INSERTION

Answer 10

Where the moveable end of a muscle attaches to bone

Question 11

AGONIST

Answer 11

The muscle contraction that is responsible for producing a particular movement

Question 12

FLEXORS

Answer 12

A muscle whose contraction bends a limb or other part of the body

Question 13

EXTENSORS

Answer 13

A muscle whose contraction extends/straightens a limb or other part of the body

Question 14

Distinguish between Ligaments and Tendons.

Answer 14

Tendon - Muscle to bone

Ligament - Bone to bone

Question 15

Discuss the role of muscles in the tendon jerk reflex.

Answer 15

Muscles are the effectors of the reflex arc, causing the movement to occur.