The Muscular System

Question 1

Muscle cells

Answer 1

highly specialized to
convert chemical energy (ATP) into
kinetic energy.

Question 2

Skeletal muscle

Answer 2

-Striated and tubular
-have many nuclei
-contract voluntarily
-are usually attached to the bones of the skeleton

Question 3

SKELETAL MUSCLE FUNCTION

Answer 3

SUPPORT – contraction of muscles opposes force
of gravity.
MOVEMENT – allows for movement of bones
(arms and legs), eyes, face.
Maintain body TEMPERATURE – ATP breakdown
releases heat spread
 PROTECTION – pads bones and cushions organs.
STABILIZE JOINTS – tendons help hold bones to
joints.

Question 4

Smooth muscle

Answer 4

-Non-striated
-have one nucleus
-Contract involuntarily
-are found in the walls of internal organs

Question 5

Cardiac muscle

Answer 5

-striated, tubular, branched
-have one nucleus
-Contract involuntarily
-are found in the walls of heart

Question 6

What is the Order of Components in the skeletal muscles? (Largest to Smallest)

Answer 6

Muscle > Muscle Fiber Bundle > Muscle Fiber > Myofibril > Myofilaments

Question 7

Muscles

Answer 7

An organ surrounded by connective tissue
and composed of several tissues. Largest unit;
attached to bone by tendons.

Question 8

Muscle fibres

Answer 8

organized into larger bundles; up to
20 cm long. Connective tissue wraps fibers

Question 9

Myofibrils

Answer 9

thousands of cylindrical subunits.

Question 10

Myofilaments

Answer 10

protein structures responsible for
muscle contraction; two types.
Actin – thin filament
Myosin – thick filament

Question 11

Sarcomere

Answer 11

-functional
-Composed of myofilaments.

Question 12

MUSCLE FIBRE (MUSCLE CELL)

Answer 12

-Myoglobin
-Sarcolemma
-Sarcoplasm
-Sarcoplasmic reticulum

Question 13

Myoglobin

Answer 13

-stores oxygen for muscle contractions.

Question 14

Sarcolemma

Answer 14

membrane of muscle fibre;
entry and exit of materials.

Question 15

Sarcoplasm

Answer 15

cytoplasm of muscle fibre;
site of metabolic processes; contains
myoglobin and glycogen.

Question 16

Sarcoplasmic reticulum

Answer 16

smooth ER in
muscle fibre; stores calcium ions.

Question 17

MYOFILAMENTS
Actin (thin)

Answer 17

composed of globular actin proteins and ion receptor proteins called troponin and tropomyosin.

Question 18

MYOFILAMENTS
Myosin (thick)

Answer 18

composed of myosin proteins, two polypeptide chains wrapped around each other; ends have
globular heads.

Question 19

MUSCLE CONTRACTION –
SLIDING FILAMENT MODEL

Answer 19

Major Steps:
1. Presence of calcium ions allow myosin
head to attach to actin
2. Myosin head flexes, pulling on the actin
filament
3. Myosin head releases and unflexes via
ATP
4. Myosin reattaches to actin further down
fibre

Question 20

ROLW OF CALCIUM

Answer 20

Muscle relaxed – tropomyosin blocks
myosin binding sites along the actin
molecule.
Muscle contracted – calcium ions bind to
troponin on actin causing tropomyosin to
reposition and expose myosin binding sites.

Question 21

Three mechanisms to make ATP

Answer 21

1. Breakdown of creatine phosphate (no O2 required)
2. Aerobic cellular respiration
3. Fermentation (no O2 required)

Question 22

CREATINE PHOSPHATE BREAKDOWN

Answer 22

A high-energy molecule built up during rest, CANNOT generate muscle contraction. Regenerates ATP by contributing a phosphate to sliding filaments.

Question 23

AEROBIC CELLULAR RESPIRATION

Answer 23

Glucose or fatty acids converted to ATP. Provides majority of energy for muscles.

Question 24

FERMENTATION TO LACTIC ACID

Answer 24

Accumulation of lactate in muscle fibre
makes sarcoplasm more acidic  enzymes
stop functioning!
If fermentation continues longer than 2-3
minutes  cramping, fatigue
Muscles can use glucose OR fatty acids to
make ATP; brain can only use glucose.

Question 25

Atrophy

Answer 25

reduction of size, tone and power of muscle; often caused by disuse.

Question 26

Hypertrophy

Answer 26

exercise-induced increase in muscle mass.

Question 27

MYOGRAMS

Answer 27

force of a muscle contraction IN A SKELETAL MUSCLE with time. When a muscle is not allowed to relax completely between stimuli, the contraction gradually increases in intensity until it reaches a maximum (tetanus), which is sustained until the muscle fatigues

Question 28

Two main muscle fibres:

Answer 28

Slow-twitch (Type I) – dark; contain
myoglobin and have many surrounding
capillaries.
Fast-twitch (Type II) – light; little or no
myoglobin and fewer blood vessels.

Question 29

SLOW TWITCH FIBRES (long term)

Answer 29

Contract slowly, but resist fatigue.
Produce most ATP aerobically,
so tire only when fuel supply is gone.

Question 30

FAST TWITCH FIBRES (short term)

Answer 30

-Produces most energy anerobiacally - putting them at risk of lactate accumulation.
-Adapted for rapid generation of
power, but fatigue quickly.
-Rich in glycogen; large number
of sarcomeres.

Question 31

INTERMEDIATE FIBRES

Answer 31

Fast twitch but high oxidative capacity
(fatigues slowly).
Proportion can be increased by endurance
training and genetics.

Question 32

FORCE & RESPONSE TIMES

Answer 32

Skeletal muscles have different proportions
of fast-twitch and slow-twitch fibres. Thus,
the force and response times of their
contractions differ.