Muscular System (Review & Comprehension)

Question 1

What are the functions of the Muscular System?

Answer 1

1. Movement of the body
2. Maintainance of posture
3. Respiration
4. Production of body heat
5. Constriction of organs and vessels
6. Communication
7. Constraction of the heart

Question 2

Define the Contractility, Excitability, Extensibility, and Elasticity.

Answer 2

Contractility - ability to shorten with force

Excitability - Capacity to respond to a stimulus

Extensibility - ability to be stretched to their normal resting length

Elasticity - ability to recoil to their original form

Question 3

List the connective tissue layers associated with muscles

Answer 3

• The endomysium
• The perimysium
• The epimysium

Question 4

What are muscle fasciculi?

Answer 4

numerous visible bundles that make up the muscle

Question 5

what is muscle fiber?

Answer 5

several muscle cells that compose a fasciculus

Question 6

Explain the irrelevance of the structural relationship among sarcomeres, T tubules, and the sarcoplasmic reticulum.

Answer 6

The sarcomere is going to form myofibrils through end-to-end connections. During muscle contraction, the T tubules are stimulated by the action potential to further deliver this stimulus to the sarcoplasmic reticulum to release “divalent calcium” ions.

Question 7

What is sarcomere?

Answer 7

highly ordered, repeating units of actin + myosin myofilaments; joined end to end to form myofibril

Question 8

Explain the resting membrane potential and how it is produced.

Answer 8

What generates the resting membrane potential is the K+ that leaks from the inside of the cell to the outside via leak K+ channels and generates a negative charge in the inside of the membrane vs the outside. At rest, the membrane is impermeable to Na+, as all of the Na+ channels are closed.

Question 9

Describe the composition of a myofibril.

Describe the structure of actin and myosin myofilaments.

Answer 9

The myofibrils are made up of thick and thin myofilaments, which help give the muscle its striped appearance.

The thick filaments are composed of myosin, and the thin filaments are predominantly actin, along with two other muscle proteins, tropomyosin, and troponin.

Question 10

Describe the production of an action potential.

Answer 10

A skeletal muscle action potential is generated when the motor endplate potential is sufficient to raise the surrounding sarcolemmal potential above the threshold for activation of the voltage-gated Na+ channels that are abundant throughout the sarcolemma.

Question 11

What is the neuromuscular junction and what happens there?

Answer 11

A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.

Question 12

Describe the sliding filament model of muscle contraction

Answer 12

The sliding filament model describes the process used by muscles to contract. It is a cycle of repetitive events that causes actin and myosin myofilaments to slide over each other, contracting the sarcomere and generating tension in the muscle.

Question 13

Explain how an action potential results in muscle contraction.

Answer 13

A Muscle Contraction Is Triggered When an Action Potential Travels Along the Nerves to the Muscles. The chemical message, a neurotransmitter called acetylcholine, binds to receptors on the outside of the muscle fiber. That starts a chemical reaction within the muscle.

Question 14

Define muscle twitch, tetanus, and recruitment.

Answer 14

A muscle twitch is an involuntary contraction of the fibers that make up a muscle. There are 3 phases; Lag/Latent, Contraction and Relaxation Phase

Tetanic contraction (tetanus) occurs when stimulation frequency is so rapid that there’s no relaxation.

Recruitment - the no. of muscle fibers contraction is increased by the increasing no. of motor units stimulated + muscle contracts with more force.

Question 15

Describe two ways energy is produced in skeletal muscle.

Answer 15

Aerobic respiration - which produces ATP and breaks down glucose; requires oxygen

Anaerobic respiration - no oxygen; breaks down glucose to yield ATP and lactic acid

Question 16

Explain fatigue

Answer 16

Fatigue is often thought of as the state of feeling very tired, weary, or sleepy resulting from various sources such as insufficient sleep, prolonged mental or physical work, or extended periods of stress or anxiety.

Question 17

Compare isometric, isotonic, concentric, and eccentric contraction

Answer 17

Isometric - A muscular contraction in which the length of the muscle does not change; equal distance

Isotonic - A muscular contraction in which the length of the muscle changes; equal tension

Eccentric - isotonic contraction where the muscle lengthens.

Concentric - An isotonic contraction where the muscle shortens

Question 18

What is muscle tone?

Answer 18

• constant tension produced by body muscles over a long period of time
• Responsible for keeping the back and legs straight, the head in an upright position, and the abdomen from bulging

Question 19

Compare the slow twitch and fast twitch

Answer 19

Slow Twitch - contains type I myosin; contracts slowly and is resistant to fatigue respiration

Fast Twitch

• Type IIa: intermediate speed; more fatigue resistant than type IIb.
• Type IIb: contract 10x faster than type I

Question 20

How do smooth muscles and cardiac muscles differ from skeletal muscles?

Answer 20

Cardiac and skeletal muscle are both striated in appearance, while the smooth muscle is not. Both cardiac and smooth muscle is involuntary while the skeletal muscle is voluntary.

Question 21

Define origin

Answer 21

head; most stationary end of the muscle

Question 22

Define Insertion

Answer 22

end of the muscle attached to the bone undergoing the greatest movement

Question 23

Define Agonist

Answer 23

muscle that accomplishes a certain movement

Question 24

Define Antagonist

Answer 24

muscle acting in opposition to an agonist

Question 25

Define Synergists

Answer 25

a group of muscles working together to produce movement

Question 26

Define Prime Mover

Answer 26

the muscle that plays a major role in accomplishing desired movement

Question 27

Define Fixators

Answer 27

muscles that holds one bone in place relative to the body

Question 28

Describe the muscles of facial expression

Answer 28

The muscles of facial expression are located in the subcutaneous tissue, originating from bone or fascia, and inserting onto the skin. By contracting, the muscles pull on the skin and exert their effects. They are the only group of muscles that insert into the skin.

Question 29

What is mastication? What muscles are involved?

Answer 29

The primary muscles of mastication (chewing food) are the temporalis, medial pterygoid, lateral pterygoid, and masseter muscles. The four main muscles of mastication attach to the rami of the mandible and function to move the jaw (mandible).

Question 30

What is intrinsic tongue muscle?

Answer 30

located within the tongue and change its shape

Question 31

What is extrinsic tongue muscle?

Answer 31

attached to and move the tongue

Question 32

What muscles are involved in swallowing?

Answer 32

Intrinsic Muscles
Extrinsic Muscles
Hyoid muscles
Pharyngeal elevators
Pharyngeal constrictors

Question 33

What muscles are involved in respiration?

Answer 33

• Linea alba
• Rectus abdominis
• Tendinous intersections
• External / Internal Abdominal Oblique
• Transversus Abdominis

Question 34

Describe the functions of the muscles of the anterior abdominal wall.

Answer 34

The majority of the anterior abdominal wall is formed by the rectus abdominis muscle.

The muscles of the anterior abdominal wall are largely involved in protecting the contents of the abdominal cavity.

Function to move the trunk and assist in other bodily functions.

Question 35

What is primarily responsible for attaching the upper limb to the body?

Answer 35

The Pectoralis major and Latissimus Dorsi.

Pectoralis Major - adducts the arm and flexes the shoulder; extend the shoulder from a flexed position

Latissumus Dorsi - swimmer’s muscle; medially rotates and adducts the arm and powerfully extends the shoulder

Question 36

Describe, by muscle groups, movements of the arm

Answer 36

Arm Movements
1. Pectoralis major – adducts the arm and flexes the shoulder; extend the shoulder from a flexed position

2. Latissimus dorsi – swimmer’s muscle; medially rotates and adducts the arm and powerfully extends the shoulder
3. Rotator cuff muscles – attached the humerus to the scapula and forms a cuff/cap over the proximal humerus
4. Deltoid – attaches the humerus to the scapula and clavicle; major abductor of the upper limb

Question 37

Describe, by muscle groups, movements of the forearm

Answer 37

1. Triceps brachii – primary extensor of the elbow
2. Biceps brachii & brachialis – primary flexors of the
   elbow
3. Brachioradialis – posterior forearm muscle; helps flex the elbow
4. Supinator – supination of the forearm or turning the flexed forearm so that the palm is up
5. Pronator – pronation, turning other forearm so that the palm is down

Question 38

Describe, by muscle groups, movements of the hand

Answer 38

Retinaculum (fibrous connective tissue that covers the flexor & extensor tendons and holds them in place around the wrist)

Flexor carpi (flex the wrist)

Extensor carpi (extend the wrist)

Flexor digitorum (flexor of the digits/fingers)

Extensor digitorum (extension of the fingers)

Intrinsic hand muscles (19 muscles located within the hand)

Interossei (responsible for abduction and adduction of the fingers)

Tennis elbow (inflammation and pain due to forceful, repeated contraction of the wrist extensor muscles)

Palmus longus (tightens palm skin)

Question 39

Describe, by muscle groups, movements of the thigh

Answer 39

Iliopsoas – flexes the hip

Tensor fasciae latae – helps steady the femur on the tibi when a person is standing

Gluteus maximus – extends the hip; adducts and laterally rottes the thigh; contributes most of the mass

Gluteus medius – extends the hop when the thigh is flexed at a 45O angle; common site for injections in the buttocks (sciatic nerve lies deep to the g. maximus)

Question 40

Describe, by muscle groups, movements of the leg

Answer 40

Quadriceps femoris – primary extensors of the knee

Sartorius – tailor’s muscle; longest muscle in the body; flexes the hip and knee; rotates the thigh laterally for sitting cross-legged

Hamstring muscles – flexing the knee Adductor muscles – adducting the thigh

Question 41

Describe, by muscle groups, movements of the foot

Answer 41

Gastrocnemius & Soleus – form the bulge of the calf

Calcaneal tendon – Achilles tendon; flexors and are
involved in plantar flexion of the foot

Fibularis muscles – primary everters of the foot; aid in plantar flexion

Intrinsic foot muscles – flex, extend, abduct, and adduct the toes

Extensor digitorum longus – extends 4 lateral toes, everts foot

Extensor halluces longus – extends great toe; inverts foot

Tibialis anterior – inverts foot Fibularis tertius – everts foot

Flexor digitorum longus – flexes 4 lateral toes, inverts foot

Flexor halluces longus – flexes great toe, inverts foot

Tibialis posterior – inverts foot

Fibularis brevis – everts foot

Fibularis longus – everts foot