13.9 Voluntary & Involuntary Muscles

Question 1

What are the 3 types of muscle?

Answer 1

• SKELETAL
  
  • make up bulk of body muscle tissue
  • for movement
• CARDIAC
  
  • found only in heart
  • myogenic - contract without need for nervous stimulus
• SMOOTH
  
  • walls of hollow organs, blood vessels, digestive tract etc
  • constrict/dilate pathways

Question 2

Describe the properties of the different types of muscle:

Answer 2

• SKELETAL
  
  • striated
  • voluntary
  • cells/fibres regularly arranged >> unidirectional muscle contraction
    
    • tubular & multinucleated
  • rapid contraction speed & short duration of contraction
• CARDIAC
  
  • striated (fainter)
  • involuntary
  • cells branch >> simultaneous contraction
    
    • branched & uninucleated
  • intermediate contraction speed & duration
• SMOOTH
  
  • non-striated
  • involuntary
  • no regular arrangement >> different cells can contract in different directions
    
    • spindle-shaped & uninucleated
  • slow contraction speed but long contraction duration

Question 3

Describe the properties of skeletal muscle:

Answer 3

• striated
• voluntary
• cells regularly arranged >> unidirectional muscle contraction
• rapid contraction speed, short duration
• fibres are tubular & multinucleated

Question 4

Describe the properties of cardiac muscle:

Answer 4

• striated (fainter than skeletal)
• involuntary
• branched >> simultaneous contraction
• intermediate contraction speed & duration
• fibres are branched & uninucleated

Question 5

Describe the properties of smooth muscle:

Answer 5

• non-striated
• involuntary
• irregular
• slow contraction speed but long duration
  *

Question 6

Describe the properties of smooth muscle:

Answer 6

• non-striated
• involuntary
• no regular arrangement >> different cells can contract in different directions
• slow contraction speed but long duration
• fibres are spindle shaped & uninucleated

Question 7

Compare the structure of fibres of skeletal, cardiac & smooth muscle tissue:

Answer 7

• skeletal: tubular & multinucleated
• cardiac: branched & uninucleated
• smooth: spindle-shaped & uninucleated

Question 8

Compare the arrangement of cells within skeletal, cardiac & muscle tissue & link it to their function:

Answer 8

• SKELETAL
  
  • regular
  • unidirectional contraction, for movement of limb in 1 direction
• CARDIAC
  
  • branched
  • simultaneous contraction, for contracting heart chambers
• SMOOTH
  
  • irregular arrangement, spindle shaped

Question 9

How are muscle fibres formed?

Answer 9

fusion

of individual embryonic muscle cells

Question 10

What is sarcoplasm?

Answer 10

shared cytoplasm

within a muscle fibre

(cytoplasm is shared by cells due to fusion of muscle cells)

Question 11

What is a sarcolemma?

Answer 11

plasma membrane

which envelops muscle fibres

of skeletal muscle

Question 12

What are T tubules?

Answer 12

sections of sarcolemma which fold inwards

helps spread electrical impulses throughout sarcoplasm

so that whole fibre contracts simultaneously

Question 13

What is the sarcoplasmic reticulum & its function?

Answer 13

modified endoplasmic reticulum found in skeletal muscle cells

contains calcium ions for muscle contraction

Question 14

Skeletal muscles are made from bundles of ____ ____ enclosed in the ____.

Answer 14

muscle fibres

sarcolemma

Question 15

What are myofibrils?

Answer 15

long, cynlindrical organelles

found in muscle

made of protein

& specialised for contraction

Question 16

Describe the structure of myofibrils:

Answer 16

Made from 2 types of protein filaments:

• ACTIN
  
  • thinner filament
  • consists of 2 strands twisted around each other
• MYOSIN
  
  • thicker filament
  • long rod-shaped fibres with bulbous heads

Question 17

Which protein filaments form myofibrils?

Answer 17

ACTIN & MYOSIN

Question 18

What causes the presence of light bands on skeletal muscle fibres?

Answer 18

absence of myosin

/ areas where only actin is present

(not myosin, the thicker filament)

Question 19

What causes the presence of dark bands in skeletal muscle fibres?

Answer 19

presence of myosin

(the thicker protein filament)

Question 20

label the diagram:

Answer 20

Question 21

What is a sarcomere?

Answer 21

functional unit of the myofibril

Question 22

Voluntary & Involuntary Muscles

What is the A-band?

Answer 22

section of sarcomere

which contains myosin

Question 23

Voluntary & Involuntary Muscles

What is the H-zone?

Answer 23

section of sarcomere

which contiains myosin without actin

Question 24

Voluntary & Involuntary Muscles

What is the I-band?

Answer 24

section of sarcomere

which contains no myosin

Question 25

Describe the structure of a sarcomere:

Answer 25

• z-line to z-line = sarcomere
• H-zone = myosin without actin
• I-band = no myosin
• A-band = myosin
• z-line = middle of light band

Question 26

Describe & explain which sarcomere section each image is taken from:

Answer 26

small dots are actin, since thinner

large dots are myosin, since thicker

1. LIGHT BAND - only actin present
2. H-zone - only myosin present
3. DARK BAND - actin & myosin present