BIOL125 Lecture Notes - Lecture 5: Endomysium, Ultimate Tensile Strength, Epimysium

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- Muscle cells (like neurons) have excitability/irritability due to a polarised membrane

 ability to contract/shorten and relax/lengthen  movement in body

- Note: muscle cell = muscle fibre; contractile proteins known as (myo)filaments

- Muscle cells tend to have prefix “sarco” ie.

oSarcolemma = plasma/cell membrane

oSarcoplasm = cytoplasm

oSarcoplasmic reticulum = endoplasmic reticulum – like organelle

- Three types: skeletal, cardiac and smooth muscle cells (and tissues)

- Each have different locations in the body; all create movement by shortening upon

contraction and lengthening upon relaxation

- Cardiac and smooth cells have a single nucleus in contrast to skeletal cells

- Smooth muscle twists upon contraction while cardiac and skeletal muscles directly

shorten

- All 3 types of muscle cells contain protein myofilaments: actin and myosin (with

varying arrangement) that interact to produce contraction and relaxation

- Skeletal muscle cells are multinuclei

Properties of Skeletal Muscle

- Both voluntary and autonomic

(involuntary) control

- Contraction under control of somatic

motor neurons

- Somatic = body

- Multinucleate ie. Formed from

multiple myoblast cells fusing

together

- Multiple nuclei  large numbers of

enzymes and structural proteins

needed for contraction

- Many mitochondria; lots of ATP

needed for contraction 

mitochondria on and around the

contractile filaments

- Striated arrangement: myofibrils arranged in sarcomeres

- Q. Provide examples of involuntary/autonomic contraction of skeletal muscle 

protective type of responses eg: eye twitch; autonomic control of regulating of

breathing at night

- Striations  thin filaments =

- Intercolated disc  allows rapid transfer of ions through cells

- Cardiac cells have intercolated discs – bottom picture on slide 7

- Q. What capacity for regeneration do they have? Depends on ability to perform

mitosis

oCardiac muscle cells have limited capacity for regeneration. Cells become

hypertrophic to generate extra force

oSkeletal muscle cells cannot undertake mitosis – ability to repair and

regenerate because of myosatellite cells?

oSmooth muscle cells – when we have enough cells, they will stop dividing. But

this can be reactivated to replace damaged smooth muscle cells

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Origin and insertion of a Skeletal Muscle

- Muscles attach to bones via tendons in two places: a fixed point and a moveable

point

- Origin  point of tendon attachment to the less moveable bone; ie. Bone does not

change position during muscle contraction; typically proximal to insertion

- Insertion  point of tendon attachment on the more moveable bone, ie. Moves bone

during contraction; located across the other side of the joint from the origin

- When a muscle contracts, the insertion point moves towards the point of origin

- Muscles can only pull bones, not push them, so they work in antagonistic pairs or

sets

- Have to have crossing over a joint to allow flexion and extension

Skeletal muscle attachment to bone

- Skeletal muscles attach to bone via:

1. Tendons

2. Flat/broad sheets (aponeuroses)

- These attachments are primarily collagen fibres (as in ligaments) which extend into

the bone providing a firm attachment (collagen fibres have high tensile strength)

- Tendon: extension of collagen fibres of the epimysium, perimysium and endomysium

which together form a bundle

- Aponeurosis: collagen fibres forming a flat/broad sheet

- Attachment points on bones are rough to allow strong attachment

- Muscle is made up of bundles (fascicles) of muscle fibres surrounded by perimysium

for protection

- Each muscle cell is surrounded by endomysium which isn’t as tough as perimysium

to allow blood vessels to get through to muscle cell

- How the fascicles are arranged determines the type of movement

- Myofilaments (actin and myosin) arranged into sarcomeres

Internal Organisation of a skeletal muscle fibre/cell

- Myofibrils: run entire length of cell; organised in repeating end-to-end

structural/contractile units (sarcomeres); attached to sarcolemma at both ends of

muscle fibre; external part of

sarcolemma attached to

collagen fibres of tendon

- When myofibril

shortens/contracts, entire

muscle fibre shortens so pulls

on tendon  movement

- Myofibrils surrounded by

mitochondria and glycogen

(reserve for ATP formation)

- Myofibrils = 2 contractile

myofilaments/proteins;

actin/thin filament and

myosin/thick filament; plus other proteins (titin, troponin and tropomyosin)

- Myofibrils regulate how much contraction is needed

- If actin side is covered, no contraction can occur

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Document Summary

Muscle cells (like neurons) have excitability/irritability due to a polarised membrane. Ability to contract/shorten and relax/lengthen movement in body. Note: muscle cell = muscle fibre; contractile proteins known as (myo)filaments. Muscle cells tend to have prefix sarco ie. sarcolemma = plasma/cell membrane: sarcoplasm = cytoplasm, sarcoplasmic reticulum = endoplasmic reticulum like organelle. Three types: skeletal, cardiac and smooth muscle cells (and tissues) Each have different locations in the body; all create movement by shortening upon contraction and lengthening upon relaxation. Cardiac and smooth cells have a single nucleus in contrast to skeletal cells. Smooth muscle twists upon contraction while cardiac and skeletal muscles directly shorten. All 3 types of muscle cells contain protein myofilaments: actin and myosin (with varying arrangement) that interact to produce contraction and relaxation. Multinucleate ie. formed from multiple myoblast cells fusing together. Multiple nuclei large numbers of enzymes and structural proteins needed for contraction.

Related Questions

Hello everyone, i'm working on thesepractices multiple choices for my finals. If you know any of theseanswer, please help. i appreciate your time and your help. Thankyou!!!

1. ___ Which of thefollowing statements about the cytoskeleton is false?

(a) The cytoskeletonis made up of three types of protein filament.

(b) The bacterialcytoskeleton is important for cell division and DNAsegregation.

(d) The cytoskeleton of acell can change in response to the environment.

2. ___ Which of thestatements below about intermediate filaments is false?

(a) They can stayintact in cells treated with concentrated salt solutions.

(b) They can befound in the cytoplasm and the nucleus.

(d) Each filament is about10 ?m in diameter.

3. ___ Keratins,neurofilaments, and vimentins are all categories of intermediatefilaments. Which of the following properties below is nottrue of these types of intermediate filaments?

(a) They strengthencells against mechanical stress.

(b) Dimers associateby noncovalent bonding to form a tetramer.

(d) Phosphorylation causesdisassembly during every mitotic cycle.

4. ___ Which of thefollowing statements about microtubules is true?

(a) Motor proteinsmove in a directional fashion along microtubules by using theinherent structural polarity of a protofilament.

(b) The centromerenucleates the microtubules of the mitotic spindle.

(d) ATP hydrolysis by atubulin heterodimer is important for controlling the growth of amicrotubule.

5. ___ Thehydrolysis of GTP to GDP carried out by tubulin molecules________________.

(a) provides theenergy needed for tubulin to polymerize

(b) occurs becausethe pool of free GDP has run out

(d) allows the behavior ofmicrotubules called dynamic instability

6. ___ The microtubulesin a cell form a structural framework that can have all thefollowing functions except which of the following?

(a) holding internalorganelles such as the Golgi apparatus in particular positions inthe cell

(b) creating longthin cytoplasmic extensions that protrude from one side of thecell

(d) moving materials fromone place to another inside a cell

7. ___ Which of thefollowing statements about organellar movement in the cell isfalse?

(a) Organellesundergo saltatory movement in the cell.

(b) Only themicrotubule cytoskeleton is involved in organellar movement.

(d) Organelles areattached to the tail domain of motor proteins.

8. ___ Which of thefollowing statements is correct?

Kinesins and dyneins____________________.

(a) have tails thatbind to the filaments

(b) move along bothmicrotubules and actin filaments

(d) derive their energyfrom GTP hydrolysis

9. ___ Cell movementinvolves the coordination of many events in the cell. Which of thefollowing phenomena are not required for cell motility?

(a) Myosin-mediatedcontraction at the rear of the moving cell.

(b) Integrinassociation with the extracellular environment.

(d) Release ofCa²⁺ from the sarcoplasmic reticulum.

10. ___Which of the followingstructures shorten during muscle contraction?

(a) myosinfilaments

(b) flagella

(d) actin filaments

7. ___ Referring to Figure Q16-29,which of the following statements below is false?

(a) A constitutivelyactive mutant form of PKA in skeletal muscle cells would lead to adecrease in the amount of unphosphorylated phosphorylasekinase.

(b) A constitutivelyactive mutant form of PKA in skeletal muscle cells would notincrease the affinity of adrenaline for the adrenergicreceptor.

(c) A constitutivelyactive mutant form of PKA in skeletal muscle cells would lead to anexcess in the amount of glucose available.

(d) A constitutivelyactive mutant form of PKA in skeletal muscle cells would lead to anexcess in the amount of glycogen available.

8. ___ Match the targetof the G protein with the appropriate signaling outcome.

adenylyl cyclase________ A. cleavageof inositol phospholipids

ion channels_________ B.increase in cAMP levels

phospholipase C_________ C. changes in membranepotential

azureprairie-dog165

QUESTION 30

The function of centrosome is:

	1.	Microtubule initiation and organization in animal cells
	2.	Organization of thin filaments
	3.	Depolymerization of microtubules
	4.	Organization of intermediate filaments

2.5 points

QUESTION 31

The destinations of proteins synthesized on "free" ribomsomes include:

	1.	Endoplasmic reticulum
	2.	Nucleus
	3.	Mitochondria
	4.	Lysosomes

2.5 points

QUESTION 32

Microtubules can be assembled and disassembled quickly in response to the cellular changes is because:

	1.	Cells synthesize tubulin proteins very fast.
	2.	Cells can turn other cytoskeletal filaments into microtubules
	3.	Microtubules have an instable plus end and microtubules are probably organized by weak non-covalent interactions
	4.	The motor proteins of microtubules can organize the microtubules in response to the cellular changes

2.5 points

QUESTION 33

Both signal recognition particle and a translocon in rough endoplasmic reticulum membrane can recognize and bind to the signal sequence of a secretory protein, so they play the exact same role during protein co-translational translocation.

True

False

2.5 points

QUESTION 34

Rough endoplasmic reticulum is so named is because:

	1.	It has many proteins associated with its surface.
	2.	It has ribosomes associated with its cytosolic surface.
	3.	It is associated with nuclear membrane.
	4.	It has vesicles budding off its surface.

2.5 points

QUESTION 35

The membrane vesicles that transport materials between membrane compartments have a protein coat. The protein coat has similar functions in different vesicles. These functions include:

	1.	Help the enclosed material fold correctly.
	2.	Help degrade the protein in the vesicles
	3.	Maintain the internal pH of the vesicles
	4.	Function as mechanical device to form a vesicle and select the components to be carried by a vesicle.

2.5 points

QUESTION 36

Lysosomes are important for:

	1.	Receptor-mediated endocytosis.
	2.	Breaking down foreign particles brought into the cells by endosomes
	3.	Regulating the process of organelle turnover.
	4.	Protein trafficking between membrane compartments

2.5 points

QUESTION 37

Which of the following is correct about membrane biosynthesis?

	1.	Membranes are synthesized in Golgi Complex.
	2.	Membranes arise from preexisting endoplasmic reticulum membranes.
	3.	Membranes are synthesized on ribosomes.
	4.	Membranes of all organelles have the same composition of proteins and lipids, since they all originate from endoplasmic reticulum.

2.5 points

QUESTION 38

During skeletal muscle contractions, the shortening of the muscle fibers is because of:

		The shortening of the thin and thick myofilaments.
		The shortening of the cytoskeletal filaments.
		The kinesin proteins moving over microtubules.
		The actin and myosin filaments sliding over each other.

2.5 points

QUESTION 39

The assembly and disassembly of microtubules is regulated by rate of growth and shrinkage of the plus end.

True

False

2.5 points

QUESTION 40

The functions of Golgi complex include:

	1.	O-linked oligosaccharides and most of a cellâs complex polysaccharides are assembled in Golgi complex
	2.	Cis Golgi complex sorts proteins
	3.	Trans Golgi complex segregates proteins in different types of vesicles for dilevery.
	4.	N-linked oligosaccharides are further processed in Golgi complex

ochrecoyote721

Question 1. Increased peripheral edema could be caused by:

a. blocked lymph vessels

b. decreased capillary blood pressure

c. increased concentration of albumin in the blood

d. slowed heart rate

Question 2. The pulse pressure of a healthy student is most likely to be:

a. 5 mm Hg

b. 30 mm Hg

c. 95 mm Hg

d. 120 mm Hg

Question 3. beta-blockers inhibit the activity of beta-adrenergic receptors and change the function of the heart by:

a. increasing heart rate and increasing contractility

b. increasing heart rate and decreasing contractility

c. decreasing heart rate and increasing contractility

d. decreasing heart rate and decreasing contractility

Question 4. In cardiac pacemaker cells, the L-type calcium channels:

a. open during diastole

b. close when the membrane potential rises above threshold

c. are located in the cell membrane

d. pump Ca2+ ions into the sarcoplasmic reticulum

Question 5. Dr. Campbell used an elliptical trainer for 40 minutes at the gym. Although the workload remained constant, Dr. Campbellâs heart-rate rose to 150 beats per minute during the first 5 minutes, stayed at that level for the next 25 minutes and then started to rise. It was 180 beats per minute at the end of the exercise period.

What was the time interval between QRS complexes when Dr. Campbellâs heart rate was 180 beats per minute?

a. 3.3 ms

b. 33 ms

c. 333 ms

d. 3333 ms

Question 6. In the question 5 above, Dr. Campbellâs heart rate is most likely to have risen during the last 10 minutes of exercise because his:

a. lungs were becoming congested

b. atrial cells were fatigued

c. extracellular Ca2+ concentration had increased

d. hematocrit increased due to sweating

Question 7. A Physiology student is sitting still in a cold igloo. After 30 minutes, she stands up, walks slowly around the igloo, and suddenly starts to shiver.

The student preserved their core temperature while they were sitting by:

a. depressing their Frank-Starling mechanism

b. decreasing the extracellular Ca2+ concentration

c. relaxing smooth muscles in their peripheral circulation

d. increasing the resistance of arterioles in their arms and legs

Question 8. In the question 7 above, the student started to shiver soon after walking because:

a. their atria started to fibrillate

b. their ventricles started to fibrillate

c. blood moved to the periphery, became cold, and chilled the core when it returned to the chest

d. the ATP concentration in their skeletal muscles had dropped to zero

Please use the following scenario for answering the questions 9 and 10.

A newly discovered drug binds to myosin molecules in cardiac muscle (and nowhere else) and increases the probability that myosin molecules in ventricular cells will bind to actin filaments when the intracellular Ca2+ concentration rises. The drug is being tested as a potential therapy for patients with heart failure.

Question 9. This drug might help people who have low cardiac output by:

a. increasing peripheral resistance

b. increasing the force developed by ventricular cells

c. increasing the isovolumic contraction time

d. increasing heart rate

Question 10. The increased binding of cardiac myosin molecules to actin might prevent the drug from being a useful treatment by:

a. slowing ventricular relaxation

b. decreasing the duration of systole

c. decreasing resistance of capillaries

d. slowing heart rate

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BIOL125 Lecture Notes - Lecture 5: Endomysium, Ultimate Tensile Strength, Epimysium

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