Muscles

Question 1

Name the different level of muscle organisation from smallest to largest

Answer 1

myofilaments ( thick and thin protein filaments) –> myofibrils (individual fibres) —->along with Myocytes form muscle fibers)—>Muscle bundle (Fascicle)–> muscle tissue

Question 2

Name the fibrous OUTER COVERINGS of muscle levels

Answer 2

Epimysium (over entirel muscle organ)
Perimysium (around a fascicle(bundle) of muscle fibers)
Endomysium (around individual cell/fibres)

Question 3

Muscles can be …… OR ……
……. OR …….

Answer 3

Voluntary OR Involuntary
Striated (multinucleated) OR non striated (mononucleated )

Question 4

What is a striated muscle

Answer 4

MULTI nucleated muscle cells (Striped appearance)
Skeletal and cardiac muscle

Question 5

What is a non-striated muscle?

Answer 5

Smooth muscle

Question 6

Name the types of muscles (3 main types) with an example

Answer 6

Skeletal-orbicularis iris
Cardiac-heart only
Smooth- vessel/gland linings eg ducts of glands

Question 7

Describe a skeletal muscle and 5 important features

Answer 7

most common-found all over body limbs/head etc
Striated ( multinucleated ) muscle
Voluntary control- somatic nervous system
no gap junctions
Contractile unit = sarcomere

Question 8

what is the contractile unit of a skeletal muscle

Answer 8

sarcomere

Question 9

Describe a cardiac muscle and 5 distinguishing features

Answer 9

Found only in the heart
- Striated muscle (multinucleated)
involuntary control
Gap junctions between sarcomeres
self excitatory (syncytium ) -ie act as 1 muscle to allow coordinated pump

Question 10

Describe a smooth muscle and 6 distinguishing features

Answer 10

Involuntary control
Non- striated
mono nucleated cells
No sarcomere structure
No t tubules
Calcium enters from OUTSIDE cell and binds CALMODULIN not troponin
2 types 1. single unit eg in gut lining
2. multi unit -eg pupil muscle

Myofilaments more free of movement (from lack of sarcomeric structure)

Question 11

Name the 2 types of smooth muscle and differences

Answer 11

Single unit - eg lining gut
In sheets for peristalsis
self excitatory
Gap junctions - to allow impulse cell to cell

Multi unit ( pupil eye muscles)
Single units that act INDEPENDENTLY
NO Gap junctions
Not self excitatory -respond nervous stimuli

Question 12

Name and describe 3 function of skeletal muscles

Answer 12

• Movement - by Muscle Contractions
• Heat production -e.g. shivering)
• Posture - continuous partial muscle contractions allow stability (e.g. standing, sitting)

Question 13

What is the cell membrane of muscle called?

Answer 13

Sarcolemma

Question 14

What is the cytoplasm of muscle called?

Answer 14

Sarcoplasm

Question 15

What is the function of the Sarcoplasmic reticulum ?

Answer 15

Store calcium ions

Question 16

Name the basic makeup of a skeletal muscle from start to the muscle tissue

Answer 16

Myofilaments - thin and thick protein filaments form a myofibril

1000s of myofibrils form a muscle fiber

Muscle fibers bundled to form a muscle fascicle (bundle)

Muscle bundles Form muscle tissue

Question 17

Explain the basic contractile unit and its components

Think (Muscle alphabet (HIT ZAM)

Answer 17

A sarcomere is the basic contractile unit of a muscle fiber

Made up of myofilaments ( thin and thick filaments made up of 4 protein filaments
Thick filament = myosin
Thin filament - actin/troponin/tropomyosin
( troponin and tropomyosin are blocking proteins that stop when muscle relaxed the joining of the actin and myosin )

Heller (H )band - segment of the thick filament NOT overlapping the thin filament

Isotropic(I ) band - segment often filament NOT overlapping the thick filament

T tubules - infolding of the sarcolemma allowing impulse to travel - found between A and I band junction

Z disc - anchoring point t for myofilaments ( 1 sarcomere is from Z disc to next Z disc)

Anisotropic( A ) band - entire length of the thick filament

M line - middle line of thick filament ( m-orotein here anchors the thick filament )

Question 18

What 3 requirements are needed for a skeletal muscle contraction

Answer 18

Nerve impulse
Calcium flooding
ATP ( energy ) from mitochondria

Question 19

Explain how muscles are contracted.

Answer 19

1. Nerve impulse travels down T tubule to sarcoplasmic reticulum
2. Calcium channels open
3. Calcium floods into the sarcolemma
4. calcium binds to troponin unblocking the actin ACTIVE site
5. Myosin ( thick filament ) and actin ( thin filament ) bind
6. Actin “pulled along” past the thick filament
   .(the muscle contraction)
7. Calcium Channels close up immediately
8. Calcium ACTIVELY pumped back into Sarcoplasmic reticulum for storage

Question 20

What is the sliding filament theory

Answer 20

Explains the mechanism of muscle contraction , the myosin (thick filaments) of muscle fibers slide past the actin (thin filaments) during muscle contraction, while the two groups of filaments remain at relatively constant length.- if need to can explain how the muscle contracts via Calcium etc

Question 21

What is a sarcomere

Answer 21

The basic contractile unit of skeletal muscle

Question 22

What is the T tubule and where is it found

Answer 22

T ( transverse ) tubule is an inward fold of the sarcolemma of a skeletal muscle ) and allows electrical impulses to travel deep into the muscle cell.
Found between the A and I band of the sarcomere

Question 23

Name the four proteins that make up myofilaments and which filament they are found in

Answer 23

• Myosin (thick)
• actin (thin)
• Troponin (thin)
• Tropomyosin (thin)

Question 24

Name the protein filament (s ) in thick filaments

Answer 24

Myosin

Question 25

Name the protein filament in thin filaments

Answer 25

Actin Troponin tropomyosin

Question 26

Which are the blocking proteins in myofilaments

Answer 26

Troponin and tropomyosin ( block myosin from binding to actin)

Question 27

Are cardiac muscles non-striated / striated and voluntary / involuntary

Answer 27

striated and involuntary (smooth muscle)

Question 28

Where are cardiac muscle found?

Answer 28

Only found in heart wall

Question 29

What’s the primary function of cardiac muscles?

Answer 29

Pump blood

Question 30

How do cardiac muscles maintain a coordinated pumping action?

Answer 30

Self-exciting and act as a whole continuous electrically-coupled muscle mass thru gap junctions between sarcomeres

Question 31

In smooth muscles, calcium ions come from the outside of the cell/fibre and bind to what?

Answer 31

Calmodulin protein

Question 32

What are the 2 types of smooth muscles and an example?

Answer 32

Single unit (visceral-intestine lining) Multi unit (pupil muscles )

Question 33

how are the smooth muscle cells/fibres connected?

Answer 33

By gap junctions

Question 34

In single unit smooth muscles, how is contraction initiated?

Answer 34

By nerve fibres and nerve impulses which pass through gap junctions from muscle to muscle

Question 35

Is the single unit smooth muscle self excitatory?

Answer 35

Yes (like cardiac muscles) And acts as a single contractile unit

Question 36

Are multi unit smooth muscles self excitatory?

Answer 36

NO Respond to nervous stimulation

Question 37

Describe a muscle related genetic DISORDER. (Cause and symptoms)

Answer 37

Duchenne Muscular Dystrophy (DMD) In males only -genetic Cause: faulty dystrophin protein- fails to anchor cytoskeleton to sarcolemma (membrane) in muscle cells Symptom: Muscle wasting, motor skill difficulty, skeletal deformities, death in 20s No cure

Question 38

Describe a muscle related INFECTION.

Answer 38

Tetanus (lockjaw ) Toxin produced by bacterium clostridium tetani Overstimulates nervous system Causes painful muscle spasms -ususally starts in the head

Question 39

What is the treatment tetanus

Answer 39

Antibiotics but there is also a vaccination of inactive toxin