Musculoskeletal system

Question 1

What are the types of muscle cells?

Answer 1

Skeletal muscle cells

• Skeletal 40-50% of total body weight
• Voluntary (Controllable)
• Mostly function as moving body parts
• Stabilizing body positiongs
• Striated
• Multiple nuclei
• Very long, can be 30cm

Cardiac muscle cells

• Involuntary
• Heart only, develops pressure for arterial BF
• Striated and branched
• Joined together with intercalated discs

Smooth muscle cells

• Involuntary
• Grouped in walls of hollow organs
• Nonstriated
• One nucleus
• Thick in the middle
• Sphincters regulate flow in tubes, maintain diameter of tubes
• Move materials in GI tract and reproductive organs
• Contain thick fil, thin fil, intermediate fil, and dense bodies
• Can be either visceral (single unit) or multiunit
• Duration of contraction and relaxation is longer than for skeletal
• Has muscle tone too
• Contract in response to nerve stimuli, hormones, stretching, and local factors

Question 2

Muscular dystrophy

Answer 2

Group of muscle diseases that results in increasing weakening and breakdown of skeletal muscles over time. The disorders differs in affected muscles, degree of weakness and how fast they worsen.

Question 3

Myasthenia gravis

Answer 3

Autoimmune neuromuscular disease where the neurotransmittor function is damaged.

Question 4

Muscle rupture

Answer 4

Muscle rupture, strain, or pulled muscle. Occurs when overstretched or torn. Usually result of fatigue, overuse, or improper usage. More common that tendons rupture.

Question 5

Relative ratio is regarding the ratio of fast glycolytic (FG) and slow oxidative (SO) fibers, how does it change physical performance.

Answer 5

FG strong in intense activity like weight lifting.
SO better endurance like long distance running.

Genetic ratio but can be altered with training.

Question 6

What happens to the muscles during aging?

Answer 6

Progressive loss of mass, just as for the bones.

Ratio SO increases over FG fibers.

Question 7

What are the functions of skeletal muscles?

Answer 7

Movement
Stabilization
Store and move substances
Produce heat, by for ex shivering

Question 8

Sarcolemma

Answer 8

Membrane of muscle fiber (skeletal muscle cell)

Question 9

Sarcoplasm

Answer 9

Cytoplasm in muscle cells

Question 10

What are the three sheets of connective tissue covering different bundles of fibers called?

Answer 10

Endomyosin covers muscle fiber (muscle fibers consists of multiple myofibrils)
Perimyosin covers fascicles of muscle fibers
Epimyosin cover entire muscle where the fascicles are bundled together

Question 11

What is the transverse tubules?

Answer 11

Tunnel from surface to center, permit rapid transmissions of the action potential into the cell. Also helps regulate Ca concentration.

Question 12

What is myoglobin?

Answer 12

Protein that stores oxygen, similar to hemoglobin. Is used when the cell is not getting enough from the blood, must be recharged after use. “Oxygen recovery”

Question 13

What is the sarcoplasmic reticulum?

Answer 13

Network in muscle cell that stores Ca ions

Question 14

What are the two skeletal muscle filaments, and what are they made of?

Answer 14

Thick filament, consists of myosin.

Thin filament, consists of actin, troponin, and tropomyosin.

Question 15

What is the functional unit of the muscle fiber called, and how does it work?

Answer 15

Sarcomere. When Ca ions are released by the sarcoplasmic reticulum, it reacts with the troponin which together with tropomyosin clear the path to the actin. Now the heads of the myosin can react with ATP and bind to the actin molecules and do the power stroke. Contraction. ATP is then used to unbind and relax the sarcomere. Relaxation. The neurotransmittor Acetylcholine (ACh) is then digested by the enzyme acetylcholinestrase to end the signal and the Ca ions are put back into the sarcoplasmic reticulum.

Question 16

What are the different areas of the sarcomere called?

Answer 16

HAII and Z.
H-band between thin filaments.
A-band entire thick filaments.
I-bands are the two remaining areas between the end of the thick fil to the Z-disc.
Z-discs are the ends/connections between the sarcomeres and has a Z like shape.

Question 17

What is a muscle tone?

Answer 17

Muscle tone is the maintenance of partial contraction of a muscle, important for generating reflexes, maintaining posture and balance, and controlling proper function of other organ systems.

Question 18

What is a motor unit?

Answer 18

A neuron plus the triggered fibers. (The more precise movement needed, the fewer fibres are activated)

Question 19

Neurotransmittor ACh is used by all skeletal muscles, what does it stand for? How is it transported?

Answer 19

Acetylcholine, and travels in the active transport vesicles and then diffuses across the synaptic cleft in the neuromuscular junction.

Question 20

What are the three sources of ATP production for the muscle cell?

Answer 20

Aerobic respiration. Ordinary cellular resipration in mitochondria, requires oxygen and glucose. Produces CO2, H2O and heat. By far most efficient alternative, 36 ATP/glucose.

Anaerobic glycolysis. Glucose is converted into pyruvic acid in the reactions of glycolysis, which yield two ATPs without using oxygen. These reactions, referred to as anaerobic glycolysis, can provide enough ATP for about 2 minutes of maximal muscle activity.

Creatine phosphate. The transfer of a high-energy phosphate group from creatine phosphate to ADP forms ATP. This could go on for maximal contraction of about 15 sec before it runs out.

Question 21

What is fatigue, and what are the limiting factors?

Answer 21

Inability to contract forcefully after prolonged
activity.

Limiting factors can include:
Ca2+
Creatine Phosphate
Oxygen
Build up of acid
Neuronal failure

Question 22

What happens in a recovery phase when the cells are filled with lactic acid, are out of creatine phosphate, and out of oxygen in the myoglobin proteins?

Answer 22

Lactic acid is transported to liver where it’s converted into glucose.
Creatine phosphate is resynthesized.
Oxygen is restored to the myoglobin.

Question 23

What are the different periods of a myogram called?

Answer 23

Latent, contraction and relaxation period.

Question 24

What is wave summation?

Answer 24

Is the response in muscle activity to multiple activation potentials in a short time span. The more AP the harder the contraction.

Tetanus is the sustained muscle contraction due to multiple AP of motor nerve. Can be unfused or even fused when it is maximally stimulated.

Question 25

What are the three different muscle fiber classifications?

Answer 25

The classes are recruited in the following order:

1. Slow oxidative (SO)
2. Fast oxidative-glycolytic (FOG)
3. Fast glycolytic (FG)

Question 26

Skeletal muscles are often paired as agonist-antagonist, what are muscles called depending on in which dimension it is moving?

Answer 26

Flexor - extensor.

Abductor - adductor.