The following questions will help you prepare for the online Quiz on the Muscle Tissue.
1. Describe the difference between muscle fibres, myofirils amd myofilaments.
2. What are the main differences between skeletal, smooth and cardiac muscle tissue.
3. What is meant by oxygen debt and the all or none principle?
4. (i) Name a muscle that is identified/named based on: a. its origin and insertion .b. the orientation of the fascicles c. movement d. shape and e. location.
(ii) How do you distinguish between the insertion and the origin of a muscle?
5. Describe the following terms:
a.) motor neuron synaptic bulb
b) synaptic vesicles
c) synaptic cleft
d) motor end plate
e) t-tubules
f) sarcoplasmic reticulum
g) ACh and AChesterase
6.) What is the role of the Tropomyosin and the Troponin on the thin filament?
7.) What is a sarcomere?
8.) Distinguish between a tendon, aponeurosis and raphe. How is a tendon formed?
lets get some discussion going on these topics in preparation for the Trial test.
Thanks
Sophie
Well i'll take a stab at Question 2 regarding the differences between skeletal, cardiac and smooth muscle. From my understanding the microscopic view of skeletal muscle is multi-nucleated and has striations. Skeletal muscle is so named because most skeletal muscles move bones of the skeleton. Skeletal muscles are voluntary, as they can be somewhat controlled. Cardiac muscle is also striated, however is involuntary- beats to it's own drum! As the name suggests, cardiac muscle makes up the wall of the heart. Smooth muscle is also involuntary and said muscles propel food through ones GI tract. Smooth muscle is also non striated. Smooth muscle is located in the walls of hollow internal structures such as blood vessels and airways.
ReplyDeleteWell done Kate.. am excellent answer!!!
DeleteGreat answer Kate!! Really thorough! :)
Delete1. The muscle cell is referred to as muscle cell - it is an elongated multinucleated cell. Inside the muscle fibre/cell are the myofibrils. Myofibrils are organelles which make up most of the cell volume - they are the contractile elements. Each myofibril is made up of myofilaments (think about the great spagetti analogy!!) Myofilaments are thick and thin filaments/strands of contractile proteins (thick=myosin, thin=actin, tropomyosin & troponin)
ReplyDeleteSo basically, myofilaments are bundled together to make up a myofibril which are the contractile element within a musle cell (musle fibre)
2. Skeletal: striated, voluntary, mulitnucleated
Cardiac: striated, involuntary, usually has single nucleus
Smooth: non-striated, involuntary, single nucleus
3. When a muscle is used, lactic acid builds up - oxygen is needed to get rid of accumulated lactic acid. If there isn't enough oxygen the muscles will fatigue (lack of ATP causes muscles to contract less, spasm & tire)
All of none - muscle fibre contraction either go all the way or not at all - the stimuli need to be strong enough to contract the muscle all the way or it wont
contract at all
4. A muscle that is identified/ named based on it's:
a) Origin & insertion : Sternocleidomastoid (origin: sternum, medial portion: clavicle, insertion: mastoid process)
b) orientation of the fasicles: orbicularis oris (fascicles arranged in a circular pattern) ??
c) movement: Flexor carpi ulnaris (muscle in the forearm flexes)
d) shape: Trapezius (triangular)
e) location: Frontal belly (frontal = the forehead)
ii) how to tell the difference between insertion and origin:
Insertion: muscle is attached to a movable bone - it tapers and forms a narrow insertion
Origin: Muscle is attached to an immovable bone - it is a broad attachment EG masseter: origin = zygomatic arch & zygomatic bone (immovable) insertion = angle of the ramus and mandible
5. Describe the following:
a) motor Neuron synaptic bulb: needed to stimulate skeletal muscles. Contains vesicles (Ach) which are release from synaptic bulb into synaptic cleft through exocytosis. Also contains mitochondrion, calcium in ER. It is the site for the neuromuscular Junction
b) synaptic vesicles: within the bulb - contain acetylcholine or Ach (the neurotransmitter)
c) synaptic cleft: the space that separates the axon terminal & motor end plate (on the muscle fibre). Space is filled with gel like extracellulat substance rich in glycoproteins and collagen fibers
d) motor end plate: part of the muscle fibre - its shape increases the surface area & contains Ach receptors (to be able to communicate with the motor neuron though Ach (a chemical translater))
e) T Tubules: (transverse tubules) extension of the muscle cell - increases surface area and allows message to be translated much quicker - communicate with the exterior of the cell
f) sarcoplasmic reticulum: specialized type of smooth ER - stores calcium ions and acts as a calcium pump. Communicates with the t-tubules
g) Ach & Achesterase: Ach is the neurotransmitter which diffuses into synaptic cleft through exocytosis. Ach attaches to Ach receptors on motor end plate, opening ion channels which allow depolarization.
The Ach effects stop when Achesterase (enzyme) breaks down Ach and therefore the channel ions close and stop sending message
Not sure how I went with these first few questions. Please feel free to help me out :)
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ReplyDeleteGo Beth go!
ReplyDelete7) A Sacromere is the contractile unit of a myofibril. The shortening and lengthening of the sacromere occurs as a result of each muscle contraction.
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Well Beth 100% for that attempt!!! How impressive!!
ReplyDeleteThanks for your contribution you two.. now I have to post some more trickier questions to challenge you!
Thanks :)
ReplyDeleteI got a bit stuck with a muscle that is named based on the orientation of the fascicles.... Is the Obicularis oris correct? And also describing the motor neuron synaptic bulb... Is this actually the nerve cell? Is what I said in my answer enough information?
Also any suggestions how to explain Q1 better?!
Thanks for the questions Sophie, they really help to revise and reinforce everything :)
I'll attempt the rest tonight!!
HI Beth
ReplyDeleteYour answers are exactly what I would expect to see in a test. Yes you are right about the obicularis oris as the fascicles are orientated around and orbit! Yes the motor neuron synaptic bulb is the axon part of the motor neuron. Just FYI: a neuron is a nerve cell which has 3 parts to it: its cell body, dendrites and axon. The axon houses the synaptic end bulb. I am so please to see the depth of your understanding!
Sophie
Just to be a complete goob but to help me understand it better:
DeleteNeuron (nerve cell)
- cell body - has the DNA, mitochondria. Ribosomes and ER (all the necessary Components to keep the cell alive)
- axon - Long, cablelike projections in the cell, carries electrical messages
- dendrites (nerve endings) allows communication with other cells
Is the synaptic bulb found in the dendrites??
That is a very intelligent question. There are synaptic end bulbs in both axons and dendrites. In the case of the neuromuscular junction they are in the axon of the motor neuron.
DeleteThank you sophie. Would you mind confirming about upcoming tests? We have one for the ILM (the compulsory check point) but do we have a test next week?
DeleteThanks
Yes Beth.. Checkpoint 2 is compulsory through survey monkey.
DeleteYou do have a test this week on Wednesday, based on the trial questions that Cathy has uploaded on the blog and on MyUni.
6. A thin fiament is made up of 3 contractile proteins: actin, tropomysin & troponin. Troponin are attached to the tropomysin (which bind to the actin) When muscles are at rest, the tropomysin block the active site for myosin (and no contraction from the muscles will occur). If calcium is realeased (from the sarcoplasmic reticulum) it bind with the troponin, which then 'unlocks' the tropomysin from the actin filament - which exposes the myosin active sites. Myosin (from thick fiilament) can now bind to the active sites on the actin resulting in shortening and muscle contraction.
ReplyDeleteBasically, the role of the tropomysin & troponin regulate the actin mechanisms (contraction of muscles) by controlling the exposure of myosin active sites.
To stop the myosin binding to active sites (and to stop muscles contracting), Calcium can be pumped out of the cytoplasm (the sarcoplasmic reticulum acts as a calcium pump) once the calcium is back to
normal levels in the cytoplasm (of the muscle fibre?) the Troposymin binds back to the actin, blocking the myosin active sites and therefore preventing the myosin to bind and stopping muscle contraction.
Not sure if this is 100% and tI know here's alot more biology that goes into it but is this basically the role of these contractile proteins?
Another good answer. Yes you have a test next Wednesday on the Musculoskeletal system. Cathy can clarify tomorrow.
ReplyDeleteThanks
Sophie
Thanks sophie :)
ReplyDeleteI'll check back on the blog later to see if you have added any more questions! Thank you so much for making this available! I find it so helpful to reinforce concepts and revise!
Thanks again :)
A tendon is A dense regular CT (cordlike in shape) and attaches muscle to bone. It is the insertion area of a muscle.
ReplyDeleteAn aponeirosis is quite similar but is more like a flat sheet of CT And can connect muscle to muscle or muscle to bone and is the origin of the muscle (think of it as broader) . Not sure but can the aponeirosis sort of come together to form a tendon?
I couldn't find too much info about raphe but did read: 'A raphe is a band of collagen fibers' . Couldnt find too much more on what they actually do and the main difference between them. Help!
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DeleteAh I had difficulties with that question, but you explain it so well here :) Thanks Beth!
DeleteAnd a raphe is a 'Seam like' join of soft tissues. Not sure if you were able to see the mylohyoid muscle when we were in the anatomy lab last week but there was a really good one where you could clearly see the raphe. It looked like a white line (seam) running vertically down the middle of the mylohyoid
DeleteGood job Beth. I am glad you got to see one!
DeleteHi Sophie,
ReplyDeleteI've gotten to checkpoint 1 but I have already answered these questions! Would you still like me to give them another go?!
Beth :)
No way Beth.. you have done a magnificent job on this blog. Its mainly for the other students to try and benchmark against your answers. Thanks so much for your active learning!
Delete1. Describe the difference between muscle fibres, myofibrils and myofilaments.
ReplyDeleteMyofibrils are made up of many microfilaments and make up the muscle fibre.
2. What are the main differences between skeletal, smooth and cardiac muscle tissue.
Skeletal muscle is the only type of voluntary muscle. Skeletal muscle and cardiac muscle are striated, whereas smooth muscle is non-striated. Skeletal muscle is also attached to the bone where the other muscle groups either line organs or are attached to bone via ligaments.
3. What is meant by oxygen debt and the all or none principle?
When exercising at high intensities the human body is not able to gain enough oxygen to produce muscle contractions and movement aerobically. Therefore anaerobic processes come in to play, the body works without oxygen to form muscle contraction and movements and produces latic acid as a by-product. This anaerobic process causes an oxygen debt. Due to this, after exercise our bodies require more oxygen than that which it would have used if our bodies had had the required amount of oxygen throughout the duration of the high intensity exercise. This is because the body now has to replace the oxygen lost due to the high metabolic rate, breathing and elevated heart rates, which remove CO¬2 and hence requires more oxygen, adrenaline and noradrenaline consumed oxygen as well as replacing the oxygen that the body needed but could not get.
Not entirely sure what the all or none principle refers to but I would think it refers to our body’s inability to operate both anaerobically and aerobically. I think normally from experience when doing long distance sports such as running you start of using the anaerobic system, and then when you ‘hit the wall’ so to speak this is when the body is transitioning from anaerobic muscle exertion to aerobic muscle exertion.
4. (i) Name a muscle that is identified/named based on: a. its origin and insertion .b. the orientation of the fascicles c. movement d. shape and e. location.
Levator Labii Superioris Alaeque Nasi
Origin: From the frontal process of the maxilla
Insertion: Skin tissue of nose and upper lip.
Action: Elevators upper lip and ala, flares nostrils.
Not entirely sure about the other categories.
(ii) How do you distinguish between the insertion and the origin of a muscle?
Origin is the end of the muscle that is attached to the least moveable structure, whereas insertion is the other end of the muscle where it attaches to a movable structure.
5. Describe the following terms:
a.) motor neuron synaptic bulb
b) synaptic vesicles
Within the moundlike axon terminal are synaptic vesicles, which are small membranous sacs containing the neurotransmitter ACh.
c) synaptic cleft
The synaptic cleft is the space that separates the axon terminal and the muscle fiber. It is a gel-like extracellular substance, which is rich in glycoproteins and collagen fibers.
d) motor end plate
Specialised part of the muscle fibre’s sarcomella.
e) t-tubules
The site which action potentials are transferred across in the sarcoplasmic reticulum.
f) sarcoplasmic reticulum
Specialised endoplasmic reticulum of muscle cells.
g) ACh and AChesterase
Ach is a chemical transmitter substance released by some nerve endings. AChE is an enzyme present at the neuromuscular junction and synapses that degrades acetycholine and terminates its action.
6.) What is the role of the Tropomyosin and the Troponin on the thin filament?
Troponin and tropomyosin are regulatory proteins in the thin filament. Troponin blocks actin-active sites in relaxation mode. Tropomyosin creates actin-active sites in active mode?
7.) What is a sarcomere?
The smallest contractile unit of muscle which extends from one Z disk to the next,
8.) Distinguish between a tendon, aponeurosis and raphe. How is a tendon formed?
Hi Vanessa
DeleteGreat effort! 5 (d) spell sarcolemma not 'sarcomella'.
Can someone please help me.....
ReplyDeleteI am slightly confused as when doing the powerpoint, I noticed on one of the slides (slide 10) it says that troponin blocks the actin active sites... However, I thought that it was the tropomyosin that lines up along the actin active sites and blocks them while the muscle fiber is relaxed and the troponin anchors the tropomyosin down...
Hi Julie
ReplyDeleteYou are correct. The troponin does anchor the tropomyosin in place to block the actin active sites. So in a sense the troponin indirectly blocks the actin active sites by keeping the tropomyosin in place. When the calcium combines with the troponin it changes the configuration of the tropomyosin and exposes actin active sites.
Hope this clarifies.
Sophie
On the powerpoint it explains that the Myosin heads contain ATPase and asks why this is important. Is it so the ATP is hydrolyzed back to ADP and Pi in the myosin head allowing it to return to it's pre-stroke position to then start the cross bridge cycle again?
ReplyDeleteJust a little confused :S
You are absolutely correct Louise.
ReplyDelete1. Muscle fibres are muscle cells
ReplyDeleteMyofibrils are the cell’s organelles
Myofilaments and the smaller units contained within each myofibril
2. Skeletal muscle – voluntary movement, striated
Smooth muscle – involuntary movement, smooth/ not striated
Cardiac muscle – involuntary movement, striated
5. a Motor neuron synaptic bulb – Contains ACh in vesicles that when triggered exit the bulb via exocytosis into the synaptic cleft
b. Synaptic vesicles – Containers with ACh inside, found within the synaptic bulb
c. Synaptic cleft – Space between synaptic bulb and motor end plate, in which ions travel across
d. Motor end plate – ACh bonds to the motor end plate as it has ACh receptors
e. T-tubules – Transverse tubules allowing communication between the external part of the cell and sarcoplasmic reticulum
f. Sarcoplasmic reticulum – Main calcium storage, mediates concentration of Ca2+ within muscle fibre
g. ACh and AChesterase – ACh is found within the synaptic cleft allowing the reaction for Na+ channels to open, AChesterase stops the reaction by ‘neutralising’ ACh
6. Tropomyosin is a string like feature on the thin filament covering the Actin active sites. Troponin holds the tropomyosin in place over these sites, and is Calcium ‘sensitive’
7. A sacromere is a contractile unit of muscle fiber that is between two Z lines.
8. Tendon is the joining on muscle to bone
Aponeurosis is joining muscle to muscle
Raphe is the joining of two soft tissues