Cell 23

Front 1

What are the three muscle types?

Back 1

1) skeletal
2) cardiac
3) smooth

Front 2

Histology of skeletal muscles

Back 2

- Longitudinal section: long, multinucleated, nucleus at edge just under sarcolemma, may appear to be different sizes according to section, striated
- Cross: do not see striations, oval, nuclei at edge, visible sarcolemma and sarcoplasm

Front 3

Histology of cardiac muscles

Back 3

- Longitudinal: long, looks cylindrical but is individual cells with central nuclei, intercalated disks, striated
-Cross: central nuclei, striations not apparent

Front 4

Histology of smooth muscles

Back 4

- Longitudinal: appear in sheets, central nuclei, tapered cells, no striations
- Cross: central nuclei (may/may not see), ovalish in varying size according to section

Front 5

What is the motor unit of a skeletal muscle comprised of?

Back 5

- neuron
- axon
- all the muscle fibers it innervates

Front 6

What are the connective tissues of skeletal muscle?

Back 6

- endomysium: delicate, loose connective tissue around each muscle fiber
- perimysium: surrounds bundles of muscle fibers (fascicles)
- Epimysium: dense connective tissue surrounds muscle

Front 7

What is the importance of external lamina/basement membrane in regeneration?

Back 7

- as long as the lamina is fairly intact satellite cells can regenerate damaged muscles

Front 8

What are the 3 types of fibers?

Back 8

1) Red (type I)
2) White (type IIb)
3) Intermediate fibers (type IIa)

Front 9

Red fibers (type I)

Back 9

- high mitochondria
- strong NADH/succinic dehydrogenase enzyme activity
- slow-twitch
- resist fatigue
- less muscle tension
- continuous activity

Front 10

White fibers (type IIb)

Back 10

- low mitochondria
- weak NADH/succinic dehydrogenase reaction
- fast twitch
- fatigue easily
- generate a lot of tension

Front 11

Intermediate fibers (type IIa)

Back 11

- in between red and white fibers

Front 12

Organization of skeletal muscle

Back 12

- muscle fibers contain many myofibrils
- myofibrils are made up of myosin and actin (myofilaments)
- myofilaments are arranged in specific patters in sarcomeres

Front 13

A band of myofilaments

Back 13

-overlapping area of actin and myosin
- middle of sarcomere
- stains dark

Front 14

H band of myofilaments

Back 14

- only myosin
- bisects A band

Front 15

M line of myofilaments

Back 15

- myosin and network protein
- bisects H band

Front 16

I band of myofilaments

Back 16

- only actin
- half is part of sarcomere (the other half is part of a different sarcomere)

Front 17

Z band of myofilaments

Back 17

- bisects the I band
- Z band to Z band is the sarcomere

Front 18

What are the 3 subunits of troponin?

Back 18

C: calcium binding
I: inhibitor
T: troppomyosin binding

Front 19

Where is tropomyosin located?

Back 19

- on top of globular actin chain

Front 20

What configuration is troponin/tropomyosin in when muscle is relaxed?

Back 20

- T subunit of Troponin is bound to tropomyosin
- tropomyosin is on top of actin
- myosin head cannot bind to actin

Front 21

What happens during a muscle contraction?

Back 21

- Ca influx through the sarcoplasmic reticulum and T-tubulues (tria)
- Ca binds to C subunit and induces conformation change
- Myosin able to attach to actin, moves through ATP

Front 22

What happens in the transport of a Nerve Impulse in muscle contraction?

Back 22

- Nerve impulse arrives at motor end plate by motor neuron
- Axon sent to skeletal muscle (branches to several fibers)
- Action potential depolarizes membrane
- Action potential generated in the muscle cell (continues downwards b/c T-tubules)
- Ca released from sarcoplasmic reticulum
- Ca activate contractile proteins (actin/myosin)
- Ca returned to sarcoplasmic reticulum

Front 23

What is the muscle spindle?

Back 23

- receptor unit in muscle that contains special muscle fibers and neuron terminals surrounded by a capsule
- responds to stretch and controls muscle coordination
- provides information on muscle length

Front 24

What are the two types of special muscle fibers within a muscle spindle?

Back 24

- Nuclear bag fibers
- Nuclear chain fibers

Front 25

What is the golgi tendon organs

Back 25

- encapsulated nerve endings in the tendon that respond to stretch
- only contain afferent neurons
- provides information on tension development

Front 26

What are intercalated discs in cardiac muscle?

Back 26

- end to end junctions between each cell

Front 27

What are the 3 types of intercalated discs in cardiac muscle?

Back 27

1) Fascia adherents: sheets
2) Macula adherents: desmosomes
3) Gap junctions: allows electrical passing

Front 28

What comprises a fiber in cardiac muscle?

Back 28

- many mononucleated cells

Front 29

What are some specialized features of cardiac muscle?

Back 29

- cells branch
- mitochondria are very large (could be length of a sarcomere)
- Sarcoplasmic reticulum is well developed and organized into diads at the Z line
- central nuclei, could be binucleated
- cannot regenerate (creates connective tissue)
- Heart will beat without innervation (intrinsic conducting system)

Front 30

How are the contractile proteins of smooth muscles different?

Back 30

- not very organized
- they are anchored at the edges of the cell, called dense bodies
- thin filaments (actin) are attached to the dense bodies that contain the actin binding proteins: alpha-actinin and desmin

Front 31

What do dense bodies contain?

Back 31

-vinculin
-talin
-desmin

Front 32

What shape do smooth muscle cells have?

Back 32

- spindle shaped with a central nuclei that form to cell shape

Front 33

What supplies the energy for contraction in smooth muscle?

Back 33

- mitochondria,usually around the nucleus

Front 34

How does the contraction signal spread in smooth muscle?

Back 34

- through gap junctions (nexus junctions)
- cells function together

Front 35

What are the invaginations in smooth muscle called that control the entry of Ca?

Back 35

- caveoli

Front 36

What do smooth muscle contractions result from?

Back 36

- mechanical impulses
- electrical depolarization
- biochemical stimuli

Front 37

Where is smooth muscle found?

Back 37

- hollow visceral organs
- blood vessel walls

Front 38

Can smooth muscle replace damaged cells?

Back 38

- yes through mitosis

Front 39

Where is the T-tubule located in skeletal muscles, describe its composition.

Back 39

- A/I junction
- Triad: contains 2 terminal cisternae (where sarcoplasmic reticulum joins) and 1 T-tubule (invagination of plasma membrane)

Front 40

Where are satellite cells of skeletal muscle located? what do they do?

Back 40

- between plasma membrane and basement membrane
- dormant stem cells that can proliferate after injury to produce myoblasts

Front 41

What parts of the sarcomere shorten during contraction?

Back 41

- I and H bands

Front 42

What is the motor end plate/neuromuscular junction of skeletal muscle

Back 42

- axonal ending of motor neuron
- receptor region of striated muscle fibers that receives innervation

Front 43

What is the primary cleft in skeletal muscle?

Back 43

- a shallow depression in the muscle cells where the axon terminal lies

Front 44

What are secondary or subneural clefts in skeletal muscle?

Back 44

- narrow folds formed by the sarcolemma
- increase receptor surface area of the muscle
- presence of basement membrane does not interfere with synaptic transmission

Front 45

What is the arrangement of nuclei from nuclear bag fibers within a muscle spindle? (skeletal muscle)

Back 45

- nuclei aggregate in the expanded middle region of the spindle

Front 46

What is the arrangement of nuclei from nuclear chain fibers within a muscle spindle? (skeletal muscle)

Back 46

- nuclei are arranged linearly

Front 47

How are the T-tubules organized in cardiac muscle?

Back 47

- diads foudn at the Z line

Front 48

Is the T-tubule system found in smooth muscles?

Back 48

No, have caveoli to control Ca entrance