A&P Fall25 > Lecture 4 9/17- E-C Coupling > Flashcards

Lecture 4 9/17- E-C Coupling Flashcards

exam 2 (82 cards)

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1
Q

What are Myofibrils?

A

Cylinder tubes- Contractile elements inside skeletal cell.

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2
Q

Ligaments are?

A

Bone to bone connection; connective tissue

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3
Q

Examples of ligaments are..?

A

Patellar, ACL, MCL

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4
Q

Tendons are?

A

Muscle to bone connections

97-98% fastens muscle to bone

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5
Q

Explain how tendons are placed within the body.

A

Normal tendon in healthy muscle- when in normal position; fastened appropriately placement of tendon takes entire skeletal muscle and stretches out to an optimal length

**in order for muscles to work best, must be stretched enough but not too far (kind like frank starling law)

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6
Q

If you cut a tendon what would happen?

A

Muscle would ball up/ recoils; muscle on its own is not stretched unless held in place by normal tendon

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7
Q

Explain how tendons can not be muscle to bone?

A

Can join couple of muscular segments together; separates two sections of skeletal muscle (bodies)

In long muscles - tendon separates two parts of muscle; ends of muscle= tendons that fasten muscle into bone

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8
Q

What is the arrangement of muscles from outer most to inner most layer?

A

1) Muscle
2) Fasciculous: Muscle fasciculi (groups of muscle fibers/cells= aka motor unit)
3) Individual muscle fibers/cells
4) MYOfibrils (cylindars) inside of individual muscle cells; tubes within cell
5) Sarcomere- myofibrils are sarcomeres lined up end to end (enough together and around makes up myofibril)

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9
Q

How many myofibrils do muscles have?

A

Hundreds to thousands

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10
Q

What are in between myofibrils?

A

Mitochondria

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11
Q

What are myofibrils made of?

A

Primarily actin & myosin

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12
Q

Where are the myofibrils?

A

Live under cell wall

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13
Q

Which is smaller mitochondria or nuclei?

A

Mitochondria

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14
Q

If looking in between CELLS and see big circular oval shape, what is that? If you see a small one what is that?

A

Big: Nucleus

Small: Mitochondria

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15
Q

Identify these structures. What is this a structure of?

A

Sarcomere anatomy

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16
Q

Dark areas of filament have what?

A

Contain myosin; thick/ myosin filament

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17
Q

Areas that are lighter in filaments have what?

A

Have no myosin; actin= thin filament

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18
Q

What makes the striated appearance of a sarcomere?

A

Alternation of thick (myosin) and thin (actin) filaments

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19
Q

A bands

A

Heavy bands; mostly myosin (thick filaments)

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20
Q

I band

A

Light bands; actin (thin filaments)

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21
Q

What is the function unit of the skeletal muscle?

A

Sarcomere

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22
Q

What are Myosin filaments composed of?

A

Myosin filaments are made up of lots of myosin molecules that are wrapped by their tails to make thick filaments.

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23
Q

How many chains do the myosin filaments have?

A

6 chains
- Tail: Two heavy chains coiled around each other bend off creating two heads
- 2 Heads: each contain 2 light chains (on each side of head)

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24
Q

What are the types of light chains on the heads of the myosin filament?

A

Essential Light Chain

Regulatory Light Chain

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25
What happens at the essential light chain?
ATPase activity- cycles ATP; allows head to move around
26
What does the regulatory light chain control?
Determines what activity level the myosin head is going to have (speed) / how active head is some can cycle quicker/slower than others
27
Do skeletal muscles allow for manipulation from outside sources?
No
28
What muscle allows for manipulation of the myosin heads?
Smooth muscle; allows regulation of regulatory light chain
29
Do all types of muscle have myosin and actin filaments?
Yes
30
How does smooth muscle regulate activity of the myosin head?
Through phosphorylation and dephosphorylation of myosin head = to pick up cycling speed
31
What is the cross bridge?
Interaction of myosin filament heads with actin/thin filament
32
What are the components of the sarcomere?
Myosin/Thick filaments- dark red Actin/Thin Filaments- thin
33
What do the actin/thin filaments contain?
1) 4 strands that are two different types of molecules 2) Troponin complexes 3) Active sites
34
What are the two molecules that make up the 4 strands of the actin filament?
F-actin- 2 strands Tropomyosin - 2 strands Each are wrapped around each other
35
At rest, are the active sites of the actin filament exposed in skeletal muscle cells?
No, at rest the tropomyosin covers the active sites **Myosin heads cannot bind when covered by tropomyosin
36
What are the function of the troponin complex?
Regulation used to "unhide" active sites on actin filament
37
What are the 3 parts of the troponin complex?
Troponin- C: Binds Ca++ here; attaches Trop T and Trop I Troponin T: Binds tropomyosin and Trop C Troponin I: Binds Actin and Trop C
38
Explain how the myosin head is able to bind to the active site of the actin filament.
When Ca++ binds to Trop C= unwinds/allows tropomyosin to unfold= revealing active site
39
Explain the cross bridge cycling.
Ca++ present binds to Trop C= Active site open & Myosin head w/ADP+ Pi (has tension) binds= head pulls (takes tension off; brings end of sarcomere closer together)= ADP+Pi falls off= head has nothing on it TO release Head: - ATP binds to myosin head= releases from active site= ATP metabolized= myosin head w ADP+Pi= restarts
40
How does rigor mortis work?
Myosin heads bound, but no available ATP to unbind= muscles are stiff when protein falls apart= rigor falls apart
41
What is the H band/zone?
Present in any sarcomere where there is an area of only myosin (no overlap with actin)
42
What is the M line?
Line in the middle of the myosin band; middle of H band/zone 2 pieces of titin meet at this point
43
What are the z discs?
Structures at the border of each sarcomere; Z- one sarcomere- Z
44
What do the Z discs anchor?
Anchors actin directly; ***anchoring points for myofibrils/ myofilaments to neighboring ones Uses Titin to connect to myosin/thick filaments
45
Titin anchors what?
Anchors myosin into Z-disc so sarcomere can't fall apart Runs through myosin to connect to M line/converges with other side of titin (has a lot of elasticity)
46
When a sarcomere contracts what happens?
Z discs move closer together/disappear = sarcomere gets shorter; H bands disappear, I bands shrink A band does not change
47
Why are cardiac sarcomeres under stretched ?
Blood returning to heart has low pressure/inadequate filling= heart at resting conditions is under stretched = stretched more- pumps more (frank starling) when stretched more than normal= inc in force= inc SV= pumps more blood
48
When you workout, what is making the muscle bigger?
Working out= adding myofibrils into muscle cells (cells are getting larger)
49
What happens during a period of disuse of muscles?
Lose myofibrils and at some point will loose skeletal muscle cells (very difficult to get back)
50
What is type 1 skeletal muscle?
Redder; darker muscle, has lots of myoglobin Slower; more efficient; lots of mitochondria
51
What is myoglobin?
Oxygen transfer protein helps pull oxygen out of the blood Found inside Type 1 skeletal muscle cells
52
What is an example of type 1 muscles?
Legs Muscles carry a lot of weight/ heavy lifting
53
Explain Type 2 skeletal muscle
White; Faster twitch Very little myoglobin fewer mitochondria
54
Give an example of type 2 skeletal muscle
Eye muscles, don't carry weight
55
What gives the red color in myoglobin?
Iron in myoglobin & hemoglobin
56
Why are iron supplements not recommended for men or in high diet amounts?
Iron is an oxidizing compound; it rusts ; don't need extra iron
57
Which one is a type 1 muscle or type 2 based on the contraction graph?
Type 2- ocular muscle = fast twitch Type 1- Soleus muscle ; longer=slow contraction
58
Explain what happens when an action potential comes into a skeletal muscle cell.
1) Ca++ is released from sarcoplasmic reticulum 2) Ca++ binds to Trop-C; revealing active sites for myosin head to bind and pull= contraction
59
How does the muscle relax after an action potential?
Ca++gets put back into SR
60
Where does the action potential originate from that stimulates the skeletal muscle to contract?
Originates from motor neuron sent through NMJ; nACh release allowing Fast Na channels to open= depolarize and send action potentials down to length of skeletal muscle cell
61
How does the action potential extend down into the the skeletal muscle?
T-tubules contain fast Na channels that send the action potential from NMJ
62
What are the DHP receptors?
Dihydropyridine Receptors: Voltage sensor= w/in T tubules; opens door for Ca++ to release from SR Stimulated by depolarization
63
DHP is physically attached to what?
Ryanodine Receptor
64
What is the Ryanodine receptor?
Ca+ release channel in skeletal muscle cell Caa++ channel with door on it ; Ca++ release channel in SR
65
How does Ca get put back into the SR?
SERA pump Sarcoplasmic Endoplasmic-Reticulum ATPase
66
SERCA pump uses what kind of transport?
Primary Active transport 1ATP= 1Ca+
67
Why do skeletal muscles need so much energy?
1) ATP w Na/K pumps to pump ions back to place within action potential (down myelin shealth) 2) Myosin head ATP metabolism 3) SERCA pumps
68
What causes the ACh to be released from the motor neuron?
Ca+ influx
69
Explain the skeletal muscle Excitation Contraction coupling steps
1) Motor neuron depolarizes 2) Ca++ into motor neuron 3) ACh vesicle fuse @ presynaptic cell wall 4) ACh release into synapse 5) ACh binds to nACh 6) Na++ comes in through fast channels; some Ca++ comes in 7) Fast Na++ cells = local depolarization down skeletal muscle = EPP 8) Spread to muscle fibers & T-tubules 9) DHP receptors trigger= Ryanodine receptors open 10) Ca++ into sarcoplasm 11) Ca++ binds to Trop C- active sites open= bind to myosin head= contraction
70
Are nACh permeable to K as well?
Yes, some K can leave; but since so much Na+ is coming in makes it so not a lot of K leaves
71
Define EPP
1st change in polarity on skeletal muscle caused by ACh; Local depolarization before action potential Starts action potential; result of Na+ coming in from nACh
72
EPP happens where?
Local potential that happens at NMJ
73
EPP generates?
Source/generates action potential will always cause an action potential (threshold)
74
Why will there always be an action potential after the EPP in a healthy muscle?
Tons of ACh released then what is needed Tons of ACh receptors available
75
What is Calsequestrin?
Big Ca+ storage protein; hangs out in sarcoplasmic reticulum
76
How is Calsequestrin useful?
Stores Ca+ = helping SERCA by binding to Ca= decreasing free Ca+ concentration within container (makes SERCA job easier)
77
What is AChesterase?
Enzyme at NMJ that can terminate the contraction; degrades ACh into inactive parts breaks ester bond
78
How does Ca+ leaving the SR effect the calsequestrin?
Makes SR Ca+ even lower= so calsequestrin releases the bound Ca+ to rebuild within SR
79
What are the inactive parts of ACh?
Achetyl group (Co-A) and choline
80
How is a stronger force generated?
Faster stimulate a skeletal muscle= more force it will generate
81
What drugs affect Achesterase?
-Stygmines
82
Explain the length-tension relationship
Too much shortening= not good contraction (A) Over stretched= very will tension/contraction (D) B & C are best; optimal stretch= optimal
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