BIOD27H3 Lecture Notes - Anaerobic Respiration, Sarcomere, Cramp

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11 Aug 2010

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Chapter 12- Muscles

Introduction

x Three types of muscle tissue occur in the human body: skeletal muscle, cardiac muscle, and smooth muscle

x Most skeletal muscles are attached to the bones of the skeleton, enabling these muscles to control body movement

x Cardiac muscle is found only in the heart and is responsible for moving blood through the circulatory system.

x Skeletal and cardiac muscles are classified as striated muscles b/c of their alternating light and dark bands under the

light microscope

x Smooth muscle is the primarily muscle of internal organs and tubes, such as the stomach, urinary bladder, and blood

vessels

x Its primary function is to influence the movement of material into, out of, and within the body

x Skeletal muscles are often described as voluntary muscles, and smooth and cardiac muscle as involuntary

x Skeletal muscles can contract w/o conscious direction, and we can learn a certain degree of conscious control

over some smooth and cardiac muscle

x Skeletal muscles are unique in that they contract only in response to a signal from a somatic motor neuron; they cannot

initiate their own contraction, nor is their contraction influence directly by hormones

x Although their primary extrinsic control arises through autonomic innervation, some types of smooth and cardiac

muscle can contract spontaneous, w/o signals from the CNS

x In addition, the activity of cardiac and some smooth muscle is subject to modulation by the endocrine system

Skeletal Muscle

x Skeletal muscles make up the bulk of muscle in the body and constitute about 40% of total body weight and they are

responsible for positioning and moving the skeleton

x Skeletal muscles are usually attached to bones by tendons made of collagen; the origin of muscle is the end of the

muscle that is attached closest to the trunk or to the more stationary bone; the insertion of the muscle is the more distal

or more mobile attachment

x When the bones attached to a muscle are connected by a flexible joint, contraction of the muscle moves the skeleton

x If the centres of the connected bones are brought closer together when the muscle contracts, the muscle is called a

flexor, and the movement is called flexion

x If the bones move away from each other when the muscle contracts, the muscle is called an extensor, and the

movement is called extension

x Most joints in the body have both flexor and extensor muscles, b/c a contracting muscle can pull a bone in one direction

but cannot push it back

x Flexor-extensor pairs are called antagonistic muscle groups b/c they exert opposite effects

x When the biceps muscle contracts, the hand and forearm move toward the shoulder but when the triceps contracts, the

flexed forearm moves away from the shoulder

Skeletal Muscles Are Composed of Muscle Fibres

x A skeletal muscle is a collection of muscle cells, or muscle fibres (Fig 12-3 pg. 400)

x Each skeletal muscle fibre is a long, cylindrical cell w/ up to several hundred nuclei on the surface of the fibre.

x Skeletal muscles fibres are the largest cells in the body, created by the fusion of many individual embryonic

muscle cells

x The fibres in a given muscle are arranged w/ their long axes in parallel and each skeletal muscle fibre is sheathed in

connective tissue

x Groups of adjacent fibres are bundled together into units called fascicles with collagen, elastic fibres, nerves, and blood

vessels are found b/w the fascicles

x The entire muscle is enclosed in a connective tissue around the muscle fibres and fascicles and w/ the tendons holding

the muscle to underlying bones

Muscle Fibre Anatomy

x The cell membrane of a muscle fibre is called the sacrolemma and the cytoplasm is called the sarcoplasm

x The main intracellular structures in striated muscles are myofibrils, highly organized bundles of contractile and

elastic proteins that carry out the work of contraction

x Skeletal muscles also contain extensive sarcoplasmic reticulum (SR), a form of modified endoplasmic reticulum

that wraps around each myofibril like a piece of lace

x The sarcoplasmic reticulum consists of longitudinal tubules, which release Ca2+ ions, and the terminal cisternae,

which concentrate and sequester CA2+

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x A branching network of transverse tubules (t-tubules) is closely associated w/ the terminal cisternae; one t-

tubule w/ its two flanking terminal cisternae is known as a triad

x The membranes of t-tubules are a continuation of the muscle fibre membrane and this makes the lumen of the t-

tubules continuous w/ the ECF

x T-tubules rapidly move APs that originate at the neuromuscular junction on the cell surface into the interior of

the fibres

x W/o t-tubule, the AP could reach the centre of the fibre only by the diffusion of +ve charge through the

cytosol, a slower process that would delay the response time of the muscle fibre

x The cytosol b/w the myofibrils contains many glycogen granules and mitochondria

Myofibrils Are the Contractile Structures of a Muscle Fibre

x One muscle fibre contains a thousand or more myofibrils that occupy most of the intracellular volume, leaving little

space for cytosol and organelles

x Each myofibril is composed of several types of proteins: the contractile proteins myosin and actin, the regulatory

proteins tropomyosin and troponin, and the giant accessory proteins titin and nebulin

x Myosin is the motor protein of the myofibril

x 9DULRXVIRUPVRIP\RVLQRFFXULQGLIIHUHQWW\SHVRIPXVFOHDQGKHOSGHWHUPLQHWKHPXVFOH¶VVSHHGRI

contraction

x Each myosin molecule is composed of protein chains that intertwine to form a long tail and a pair of tadpolelike

heads

x In a skeletal muscle, about 250 myosin molecules join to create a thick filament; each filament is arranged so

that the myosin heads are clustered at the ends of the filament, and the central region of the filament is a bundle

of myosin tails

x The rodlike core of the thick filament is stiff, but the protruding myosin heads have an elastic hinge region

where the heads join the rods and this hinge allows the heads to swivel around their point of attachment

x Actin is a protein that makes up the thin filaments of the muscle fibre

x Usually multiple G-actin molecules polymerize to form long chains or filaments called F-actin

x In skeletal muscle, two F-actin polymers twist together like a double strand of beads, creating the thin filaments

of the myofibril

x Most of the time, the parallel thick and thin filaments of the myofibril are connected by crossbridges that span

the space b/w the filaments and these crossbridges form when myosin heads of the thick filaments bind loosely

to actin in the thin filaments

x The arrangement of thick and thin filaments in a myofibril creates a repeating pattern of alternating light and

dark bands

x One repeat of the pattern forms a sacromere, a unit or segment which has the following elements: (Fig 12-5

pg.402)

1. Z disks: One sarcomere is composed of 2 Z disks and the filaments found b/w them. Z disks are zigzag

protein structures that serve as the attachment site for thin filaments

2. I band: These are the lightest colour bands of the sarcomere and represent a region occupied only by thin

filaments. A Z disk runs through the middle of every I band, so each half of an I band belongs to a different

sarcomere

3. A band: This is the darkest oIWKHVDFURPHUH¶VEDQGVDQGHQFRPSDVVHVWKHHQWLUHOHQJWKRIDWKLFNILODPHQW

At the outer edges of the A band, the thick and thin filaments overlap. The centre of the A band is occupied

by thick filaments only. The protein fibres in this region scatter light unevenly

4. H zone: This central region of the A band is lighter than the outer edges of the A band b/c the H zone is

occupied by thick filaments only

5. M line: This band represents proteins that form the attachment site for thick filaments, equivalent to the Z

disk for the thin filaments. Each M line divides an A band in half

x The proper alignment of filaments within a sarcomere is ensured by two types of proteins: titin and nebulin

x Titin is a huge elastic molecule and the largest known protein, composed of more than 25 000 AA.

x A single titin molecule stretches form one Z disk to the neighbouring M line

x Titin has two functions: (1) it stabilizes the position of the contractile filaments and (2) its elasticity returns

stretched muscles to their resting length

x Titin is helped by nebulin, an inelastic giant protein that lies alongside thin filaments and attaches to the Z disk

x Nebulin helps align the actin filaments of the sarcomere

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Related Questions

Review the process of smooth muscle contractions and compare with skeletal muscle contraction.

This term does not apply to skeletal muscles at all ?

a. visceral

b. voluntary

c. striated

d. sarcoplasmic reticulum

e. calcium

periwinklebuffalo881

[email protected]

Tue 9/19/2017 4:17 PM

To:

[email protected];

Here is the exam review for our next major lecture exam which will be on Monday. Notice that there are a few things missing, such as endochondral ossification. These will be added so just because it does not show up on this exam review doesn't mean you shouldn't study it. That being said, the details of each and every bone which I've gone over in lecture will be on the lab practical rather than the written lecture exam.

Anat 1, Exam 2. Spr 2016 LASC Name:____________________________________________________

1) A synarthrosis: a) is filled with synovial fluid. b) allow for a wide range of movement. c) includes the squamosal suture. d) is exemplified by the shoulder. e) all of the above.

2) Bursae: a) are located in the right atrium. b) are like elastomeric shock absorbers. c) are found in skeletal muscle fibers. d) form the sarcoplasmic reticulum. e) none of the above.

3) Irregular bones: a) can act like cams. b) can provide sites for muscle attachment. c) can protect soft-tissue organs. d) can act as levers. e) all of the above.

4) Condyles: a) are smooth articular surfaces. b) allow blood vessels to enter the bones. c) occur beneath the nail body after an injury. d) are produced by infected sebaceous glands. e) none of the above.

5) A head: a) is where you will find hyaline cartilage. b) is a smooth articular surface. c) is where a bone meshes with another bone. d) all of the above. e) none of the above.

6) Which of the following is the proper sequence of things following a bone fracture: a) hematoma, fibrous callus, bony callus, remodeling. b) hematoma, bony callus, fibrous callus, remodeling. c) hematoma, remodeling, fibrous callus, bony callus. d) hematoma, remodeling, bony callus, fibrous callus. e) fibrous callus, bony callus, remodeling, hematoma.

7) A diaphysis: a) contains yellow bone marrow. b) contain a lot of spongy bone tissue. c) occurs at the ends of long bones. d) all of the above. e) none of the above.

8) Short bones: a) protect underlying soft tissue organs. b) include the ribs. c) include the cranial bones of the skull. d) transfer mechanical forces. e) all of the above.

9) Fibrous joints: a) contain cruciate ligaments. b) include the pubic symphysis. c) are typically found in third class levering systems. d) include the lambdoid suture. e) all of the above.

10) Which of the following doesnât belong? a) tibiofibular joint. b) dentino-alveolar joint.
c) intervertebral disc. d) radioulnar articulation. e) cartilage.

11) Which of the following doesnât belong? a) atlanto-occipital joint. b) humero-ulnar joint. c) frontal suture d) acromio-humeral joint. e) tibiotarsal joint.

12) Hyaluronic acid: a) forms the extracellular matrix. b) is found in fibrous joints. c) keeps cartilage soft and pliable. d) is found in synostoses. e) none of the above.

13) First class levers: a) include the tibio-tarsal joint. b) have the effort between the fulcrum and the load. c) are like a teeter-totter. d) all of the above. e) none of the above.

14) Synchondroses: a) are typically synovial joints. b) allow for very limited movement. c) include sutures and gomphoses. d) are encased in synovial capsules. e) none of the above.

15) Parallel muscles: a) have long excursions. b) include the abdominal muscles. c) have excellent endurance. d) have low strength. e) all of the above.

16) Sphincteral muscles: a) enclose openings or passageways. b) are used when you talk.
c) surround the eyes. d) include the orbicularis oculi. e) all of the above.

17) Pennate muscle architecture: a) is typified by the pectoralis major. b) have high endurance.
c) generates high strength. d) has a longer excursion. e) all of the above

18) Endomysium: a) consists of dense fibrous connective tissue. b) surrounds each fasciculus.
c) surrounds bundles of muscle cells. d) all of the above. e) none of the above.

19) Cartilage: a) heals quickly if it is damaged. b) forms the lining of blood vessels. c) is found on the articular surfaces of bones. d) is a type of epithelial tissue. e) none of the above.

20) A tuberosity: a) is a hollow opening. b) is a shallow smooth articular surface. c) is a raised area that adjoins a condyle. d) is a larger outwardly curved articular surface. e) is a raised, rough-textured area.

21) Which of these doesnât belong? a) tuberosity b) trochanter c) condyle d) tubercle e) lunula

22) Epimysium: a) wraps around the entire muscle. b) is made of dense fibrous connective tissue. c) is continuous with tendons. d) all of the above. e) none of the above.

23) Which of the following is more likely to be an insertion rather than an origin? a) ulna.
b) cervical vertebra. c) thoracic vertebra. d) rib. e) Ischium.

24) Which of the following is more likely to be an origin rather than an insertion? a) clavicle.
b) tibia. c) radius. d) ulna. e) metatarsal.

25) Myofibrils: a) are composed of many muscle fibers. b) are composed of many muscle cells.
c) are composed of many sarcomeres. d) form the endomysium. e) all of the above.

26) Myosin: a) helps keep muscle cells from overstretching. b) is a protein. c) joins thin filaments together. d) forms part of the z-disc. e) all of the above.

27) Sarcolemma: a) surrounds the entire muscle organ. b) surrounds the endomysium.
c) is the cell membrane of a muscle fiber. d) surrounds the epimysium. e) none of the above.

28) Thin filaments: a) are made of titin. b) are pulled on by the thick filaments during contraction.
c) create the molecular âpower-strokeâ. d) all of the above. e) none of the above.

29) A second class lever: a) is like a wheel barrow. b) is like a teeter-totter. c) describes the humeroulnar joint. d) describes the atlanto-occipital joint. e) none of the above.

30) A sarcomere: a) is the basic unit of muscle function. b) is made mostly of proteins. c) shortens during a contraction. d) delivers an âall or noneâ response. e) all of the above.

31) Fast glycolytic fibers: a) have excellent endurance. b) deliver lots of power.
c) are more reddish in color than oxidative fibers. d) none of the above. e) all of the above.

32) Which of the following doesnât belong? a) Vastus lateralus. b) Vastus intermedius. c) Vastus medialis. d) Rectus Femoris. e) Gluteus minimus.

33) Which of the following doesnât belong? a) Teres major. b) Teres minor. c) subscapularis.
d) infraspinatus. e) supraspinatus.

34) Tendon sheaths: a) are filled with synovial fluid. b) can be likened to brake and shifter cable sheathing on a bike. c) are found around the carpal bones. d) really make life unpleasant if they get inflamed. e) all of the above.

35) Epithelial tissues: a) function in movement. b) conduct electrical impulses. c) form a structure for attachment of other organs. d) form barriers and walls. e) all of the above.

36) Elastic connective tissue: a) is found in bone. b) lines the inside of the trachea. c)Is found in small blood vessels like capillaries. d) is found in large arteries. e) all of the above.

37) Cartilage: a) heals quickly if it is damaged. b) forms the lining of blood vessels. c) is found on the articular surfaces of bones. d) is a type of epithelial tissue. e) none of the above.

38) Dense regular connective tissue: a) is poorly vascularized. b) heals slowly if at all. c) forms tendons and ligaments. d) can look a lot like smooth muscle under the microscope. e) all of the above.

39) Transitional epithelium: a) lines the urinary bladder. b) lines the blood vessels. c) contains cilia. d) joins the epidermis to the dermis. e) none of the above.

40) Skeletal muscle: a) responds to conscious thought. b) is found in the heart. c) is found in the walls of blood vessels and the GI tract. d) is composed of very small cells. e) all of the above.

For the following matching questions, each choice is used only once.

41) Fibroblast a) maintains bone tissue
42) Mast Cell b) secretes mucus
43) Chondrocyte c) responsible for inflammation response
44) Osteocyte d) makes collagen fibers
45) Goblet Cell e) maintains cartilage

For the following true-false questions, mark âAâ for true and âBâ for false.

46) Simple cuboidal epithelium is lines the trachea and Fallopian tubes/oviducts.
47) Elastic cartilage joins the ribs to the sternum.
48) An insertion is the more movable point of muscle attachment.
49) Tendons connect muscle to muscle or bone to bone.
50) Ligaments connect muscle to bone.
51) Transverse tubules allow nutrients to be dispersed throughout very large muscle cells.
52) Muscle twitch occurs when only a few muscle cells in the entire muscle are fully contracted.
53) Slow oxidative fibers have poor strength but excellent endurance.
54) Muscles can lengthen under their own power as well as contract.
55) Pottâs fracture is typical of skateboarders.
56) An incomplete fracture is a complete break through the entire bone.
57) Tetanus is the recruitment of additional fibers during muscle contraction.
58) Menisci are like elastomeric shock absorbers.
59) Diarthrotic joints allow for little to no movement.
60) A belly is the contractile portion of a muscle.
61) Synergistic muscles work with each other.
62) Muscle tissue, like your lab instructorâs evil twin before his morning coffee, is irritable.

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BIOD27H3 Lecture Notes - Anaerobic Respiration, Sarcomere, Cramp

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