Midterm unit 6

Question 1

functions of skeletal muscle

Answer 1

move the body, maintain posture, protect and support, regulate elimination of material, produce heat

Question 2

contractible

Answer 2

Can shorten in length. Cells slide past one another.

Question 3

Extensible

Answer 3

extend or stretch. This is possible because the contractile proteins slide past one another to decrease their degree of overlap

Question 4

Elastic

Answer 4

return to original shape. This is dependent on the release of tension in the springlike protein associated with contractile proteins

Question 5

Skeletal muscle contain

Answer 5

Epimysium and fascicle

Question 6

Epimysium

Answer 6

a layer of dense irregular CT. PROTECTS AD SUPPORT IT LIKE A TOUGH LEATHER SLEEVE

Question 7

Perimysium

Answer 7

a layer of dense irregular tissue that provides protection over each bundle of muscle fibres (goes around each fascicle)

Question 8

Fascicle

Answer 8

a bundle of skeletal muscle fibers

Question 9

What is fascicle composed of

Answer 9

Muscle fibre and perimysium

Question 10

Sarcolemma

Answer 10

-This is the plasma membrane. The deep invagination are called T-Tubules. These channels include both na+ and k+. Contain volatge-gated sodium and k+. Extend into the skeletal muscle fibre as a network of narrow membranous tubules

Question 11

Myofibrils

Answer 11

-* 80% is composed of long cylindrical structures termed myofibrils
* Composed of bundles of contractile proteins called myofilaments and enclosed in portions of sarcoplasmic reticulum
* a skeletal muscle fibre is composed of myofibrils, myofibrils are composed of myofilaments enclosed within segments of the sarcoplasmic reticulum
* Hundreds of thousands
* Composed of bundles of myofilaments and is enclosed in portions of the sarcoplasmic reticulum

Question 12

Sarcoplasmic Reticulum:

Answer 12

is the internal membrane complex that is similar to the smooth endoplasmic reticulum of other cells.
* Portions of SR fit around each myofibril like a sleeve of membrane
* At the end of individual sections the sarcoplasmic reticulum are blind sacs called terminal cisternae
* Together 2 terminal cisternae and a centrally located T-tubule form a structure called a triad which contains voltage sensitive calcium which are responsive to electrical signals
* Also embedded in is calcium channels from the cytosol into the sarcoplasmic reticulum where it is bound to specialized protein callled calmodulin

Question 13

Sarcoplasm

Answer 13

this is the continuation of the sarcolemma

Question 14

Sarcomeres

Answer 14

the basic contractile unit of a myocyte (muscle fibre). A sarcomere is composed of two main protein filaments (thin actin and thick myosin filaments) which are the active structures responsible for muscular contraction. (the muscle contraction)

Question 15

Thin filament

Answer 15

1/2 diameter
-2 strands of actin twisted together’-F-actin resembles 2 beaded necklaces with G as the individual beads
-Each has a myosin binding site
-attaches during contraction
-Tropomyosin and troponin are regulatory proteins associated with thin filaments. Together they form the troponin-tropomyosin complex.
-Tropomyosin is a short thin twisted filament that is a string like protein
-Troponin is a globular or ball like protein attached to troponin, contains binding sites for Calcium

Question 16

thick filament

Answer 16

-200-500 myosin proteins
-each has 2 strands
-each strand has a globular head and an elongated tail
-Head contains a binding site for actin also has a catalytic ATPase site where ATP attached and is split into ADP and Phosphate
-tails are intertwined

Question 17

I band

Answer 17

Extends from both directions of the Z disc. The end region contains only thin filaments. can only be viewed with a microscope.

Question 18

A bands

Answer 18

central region of sarcomere that contains the entire thick filament. Thin filament partially overlap the thick filaments on each end. Appears dark. Does not lengthen during contraction.

Question 19

H zone

Answer 19

The most central portion of the A band. No thin filament overlap. Disappears when at full shortening

Question 20

M line

Answer 20

transverse protein meshwork in the center of H zone. Serves as a sit for thick filaments and keeps the thick filaments during contraction and relaxation events

Question 21

Z disc

Answer 21

COMPOSED OF SPECIALIZED PROTEINS THAT ARE POSITIONED PERPENDICULAR TO THE MYOFILAMENTS AND SERVE AS ANCHORS FOR THE THIN FILAMENTS

Question 22

ACTIN

Answer 22

MADE UP IN THIN FILAMENTS

Question 23

Myosin

Answer 23

made up of thick filaments

Question 24

Regulatory proteins

Answer 24

Troponin
Tropomyosin

Question 25

Troponin

Answer 25

A ball like protein attached to tropomyosin. Troponin contains the binding site for calcium

Question 26

Tropomyosin

Answer 26

a short, thin, twisted filament that is a stronglike protein. Consecutive molecule cover small region of the actin strands including the myosin binding

Question 27

Structural proteins

Answer 27

Connective, nebula, dystrophin

Question 28

connective (Titian)

Answer 28

• is a cable like protein that extends from the Z discs to the M line through the core of each thick filament maintains thick filament.
  
  • Stabilizes thick filament.
  • Spring like

Question 29

Dystrophin

Answer 29

• Anchors myofibrils that are adjacent to proteins
  
  • Genetic disorder called muscular dystrophy is caused by abnormal structure or amounts of dystrophin protein

Question 30

Nebulin

Answer 30

n addition to a major role in thin-filament length specification, nebulin also functions in the regulation of muscle contraction, as indicated by the findings that muscle fibers deficient in nebulin have a higher tension cost, and develop less force due to reduced myofilament calcium sensitivity and altered

Question 31

Neuromuscular junction

Answer 31

the specific location, usually in the mid-region of the skeletal muscle fibre where it is innervated by a motor neuron

Question 32

Synaptic knob

Answer 32

• Expanded tip of an axon
  
  • Where the axon nears the sarcolemma of a muscle fibre the synaptic knob enlarges and flattens to cover relatively large surface area
  • Houses numerous synaptic vesicles (small membrane sacs) filled with the neurotransmitter acetylcholine (Ach) repelllled from the synaptic knob
  • Ca2+ pumps are embedded in the plasma membrane of the synaptic knob. Prior to arrival of nerves the plasma knob pumps Ca2+ and establishes a concentration gradient with more Calcium outside then inside
  • Voltage gated Ca2+ channels are embedded in the membrane of the synaptic knob. Opening these channels allows Ca2+ to flow down the concentration gradient from the intersitial fluid into synaptic knob which triggers exocytic of Acetylcholine from vesicles

Question 33

Motor endplate

Answer 33

• Large plate like
  
  • Numerous flods and indentations
  • Has vast numbers of Ach receptors
  • Chemically gated ion channel
  • Binding of Ach opens these channels allowing Na+ to enter into the muscle fibre and K= exits
    ACh is the key to opening doors

Question 34

Synaptic cleft

Answer 34

• Extremely narrow fluid filled space separating the synaptic knob and the motor end plat
  
  • Filled with fluid that separates the synaptic knob and the end plate
  • Acetylcholinesterase (AChE) resides within the synaptic cleft
  • It breaks down the Ach molecules and follows them into their release into the synaptic cleft

Question 35

Acetylcholine (ACh)

Answer 35

found in the synaptic knob. They are normally repelled from the synaptic knob plasma membrane (ACH) channel chemically gated ion channels. Binding of ACH allows sodium to enter muscle fibre and K+ to exit

Question 36

Acetylcholinesterase (