Skeletal Muscle Tissue - Downing Flashcards Preview

Skin and Musculoskeletal - Week 4 > Skeletal Muscle Tissue - Downing > Flashcards

Flashcards in Skeletal Muscle Tissue - Downing Deck (25):
1

What is the name of a single muscle cell?

myofiber

2

General Features of skeletal muscle:

Striated
T-tubule system
Well developed sarcoplasmic reticulum
multinucleated (can be several hundred)
Nuclei at cell periphery

3

What lines define the sarcomere?

From one Z-line to the next Z-line

4

The a band of the muscle fiber is the:

dark zone

5

The I band the the:

light zone

6

What is the small white zone inside of the A band?

The H band

7

What is the line in the center of the H band?

The M-line

8

What subunits make up mysoin?

4 light chains and 2 heavy chains

light chains are associated with the head regions that forms the cross bridges to actin

heavy chains can be cleaved into heavy and light meromyosin
Heavy has piece that forms head and binds to actin

9

What regions of the myosin has no cross bridges?

The M-line, has no heads

10

What are the regulatory molecules of skeletal muscle and how do they regulate the muscle?

Tropomyosin
-Fibrous; arranged head to tail in a linear series
-Helically wound along grooves of F-actin helix

Troponin complex (3 subunits)
-TnT: binds entire troponin complex to tropomyosin
-TnC: great affinity for Ca++
-TnI: binds to actin, preventing actin-myosin interactions

Calcium
-Binds to TnC
-Binding to TnC induces a conformational shift in tropomyosin, exposing previously blocked active sites on the actin filament

11

What are the three connective tissue coats in skeletal muscle?

Endomysium
Sheath of fine c.t. around individual muscle fibers
Fine reticular fibers and ground substance

Perimysium
Connective tissue sheath around groups of muscle fibers (fasicles)
Continuous with tendon fibers

Epimysium
Outermost sheath of c.t.; surrounds entire muscle

12

What in the clinical presentation of Myasthenia Gravis?

Weakness and easy fatigue of muscles
Caused by autoimmune attack of ACh receptors
ADminstration of AChE inhibitors has diagnostic and therapeutic value

13

What does a motor unit consist of?

One motor neuron and all the muscle fibers it innervates

14

If a motor unit has a 1:1 ratio of motor neurons to muscle fibers, what do you know about this muscle?

It is used for VERY fine motor control

15

How does the muscle spindle work?

you have a small encapsulated group of specialized muscle cells (intrafusal fibers)
Inbedded in a large group of extrafusal fibers (normal muscle)

Within these specialized fibers you have 2 types of fiberss:
Nuclear chain fibers
Nuclear bag fibers

Surrounded by an internal and external capsule

Stretching the muscle spindle fibers will send a signal to contract the muscle

16

How does the golgi tendon organ work?

Sensory endings wedged between collagen fibers of the tendons

Protective to prevent overcontraction of a muscle

17

Tendon primarily continal with the...?

Perimysium

18

When you're working out at the gym, why are your muscles getting bigger?

The fibers are increasing in size

NOT increasing in number of fibers

19

What is the muscle equivalent of the cytoplasm?

Sarcoplasm

20

What is the muscle equivalent of the Smooth ER ?

sarcoplasmic reticulum

21

In a myofibril, where do the myosin anchor, and where do the actin anchor at?

Myosin - the M line

Actin - The Z line

22

What bands get smaller during muscle contraction?

In muscle contraction the H band and I band are going to get smaller

The A band will stay the same length

23

Explain the importance of the sarcoplasmic reticulum and T-tubules:

-Network of cisterns and/or membranous tubules running between and around myofibrils
-Binds and releases Ca ++

-Invaginations along cell surface form the t-tubules
-T-tubule lumen continuous with extracellular space
-Form triads, connected to 2 cisternae of the sarcoplasmic reticulum on either side
-FACILITATE TRANSMISSION OF ELECTRICAL IMPULSE FROM SARCOLEMMA TO INTERIOR DEPTHS OF CELL

24

Two types of actin?

G-type (globular)

F-type (fibrous)

25

What do alpha-actinin, nebulin, and Titin do for the structure?

Alpha-actinin
Component of the Z-disk
Holds actin filaments straight by binding them in parallel array

Titin (connectin)
Helps position myosin filaments precisely within the sarcomere
Extends from each half of a myosin filament to the Z-disk

Nebulin
Long, non-elastic protein
Help anchor thin filament to Z-disk