Muscular System

Question 1

what are the types of muscles

Answer 1

Smooth muscle
Cardiac muscle
Skeletal muscle

Question 1

Smooth muscle

Answer 1

• Present in organ, airways blood vessels
• involuntary
• 1 nucleus per cell
• not striated (does not contains Sarcomeres)

Question 2

Cardiac Muscle

Answer 2

• Present in the heart
• involuntary
• 1 nucleus per cell
• striated (contains Sarcomeres)
• contains intercalated disc which are made up of Desmosomes). and gap junction that connect the cytoplasm of cells together to allow ion exchange and coordinated electrical impulse propagation.

Question 3

Skeletal muscle

Answer 3

• Present around bone
• voluntary
• many nuclei per cell
• Striated (contains Sarcomeres)

Question 4

What is the skeletal muscle composed of?

Answer 4

Muscle → Muscle fascicles → Muscle fibers (muscle cells) → Myofibrils (contractile protein)

Question 5

Sarcolemma

Answer 5

is the muscle fibers cellular membrane and it protects each muscle fiber
- Contains T-tubules

Question 6

Sarcoplasm

Answer 6

is the cytoplasm of the muscle fiber and holds the myofibrils

Question 7

Epimysium

Answer 7

• the most superficial sheath
• covers the muscle itself

Question 8

Perimysium

Answer 8

Covers the muscle fascicles

Question 9

Endomysium

Answer 9

• the deepest sheath
• cover the muscle fibers

Question 10

what movement does all muscles do to move a body part?

Answer 10

they Contract (pull), They never push

Question 11

Sarcomeres

Answer 11

inside of myofibrils are the functional unit of muscle fibers and shorten to cause muscle contraction

Question 12

Myofilaments

Answer 12

contained with sarcomeres, divided into tin actin filaments and thick myosin filaments

Question 13

Sarcoplasmic Reticulum

Answer 13

is the endoplasmic reticulum of muscle fibers that release stored calcium ions into the sarcoplasm through voltage-gated calcium channels when triggered by the depolarization of the muscle

Question 14

Cross bridge cycling:

Answer 14

1. Initiation: Calcium ions expose the
   myosin-binding-sites on actin.
2. A cocked back, high energy myosin head
   (containing ADP and Pi) forms a cross bridge with the actin.
3. The myosin head contracts and the power stroke occurs, bringing the myosin head back to a low energy state and releasing ADP and
   Pi. As a result, the sarcomere shortens.
4. A new ATP molecule binds to myosin, causing
   detachment of the myosin head from the actin filament.
5. The myosin head is an ATPase, and it
   hydrolyzes the ATP into ADP and Pi. This
   causes the myosin head to re-enter a cocked back, high energy state. (Return to Step 2 if calcium ions present).
6. Termination: Neuronal signaling from motor neurons ends. The sarcoplasmic reticulum pumps calcium back into itself, and troponin
   brings tropomyosin back to cover myosin-binding sites on actin.

Question 15

Rigor mortis

Answer 15

occurs in dead animals where there is no ATP available to release myosin from the actin

Question 16

Z-line

Answer 16

-are the ends of the sarcomeres
- Thin actin filaments branch from the Z-lines towards the middle of the sarcomere

Question 17

M lines

Answer 17

are the midpoints of the sarcomeres
- thick myosin filaments branch from the M lines towards the ends of the sarcomere

Question 18

I band

Answer 18

is the area in the sarcomere where only actin filaments are present

Question 19

A band

Answer 19

is the area in the arcomere where actin and myosin overlap

Question 20

H zone

Answer 20

is the area in the sarcomere where only myosin is present

Question 21

Motor unit

Answer 21

make up muscles; refers to all the muscle fibers innervated by a single neuron

Question 22

Small motor units

Answer 22

include only a few muscle fibers and are used in precision movement

Question 23

large motor units

Answer 23

includes many muscle fibers that are innervate by a single neuron and are used in powerful movements

Question 23

twitch contraction

Answer 23

is the contraction of a muscle fiber through motor unit stimulation
- each twitch is the same size ad duration
- follow all-or-none principle

Question 24

all-or-none principle

Answer 24

that a depolarization will cause all the muscle fibers to twitch if it is above threshold potential but will not cause any twitching if the depolarization is below threshold potential

Question 25

what are the three phases of a twitch

Answer 25

Latent, Contraction, relaxation

Question 26

Latent

Answer 26

action potential spreads over sarcolemma and T-tubules, signaling to sarcoplasmic reticulum to release calcium

Question 27

Contraction

Answer 27

formation of cross bridges as a result of calcium ions binding to troponin.
- H zones shrink and muscle tension increases

Question 28

Relaxation

Answer 28

Calcium is pumped back into the sarcoplasmic reticulum, ending cross bridge cycling and decreasing muscle tension

Question 29

Summation

Answer 29

a process by which twitch add up to create a larger overall contraction

Question 30

what are the two types of summation

Answer 30

• Wave summation (temporal summation)
• motor unit summation

Question 31

Wave summation (temporal summation)

Answer 31

depolarizing a motor unit again during the relaxation phase
- may cause tetanus
-Twitches blend together during tetany, eventually causing fatigue (loss of muscle contraction).

Question 32

tetanus

Answer 32

is when the muscle fibers cannot be further stimulated due to a lack of relaxation

Question 33

motor unit summation

Answer 33

• different motor units are stimulated at different times to produce the intended amount of muscle contraction
• also known as Size principle of motor unit recruitment because smaller motor units are stimulated first before larger motor units come in to
  help.

Question 34

muscle
tone (muscle tonus)

Answer 34

Weak and involuntary twitches in small motor unit groups contribute to maintaining