Muscles And Muscle Tissue (Part A)

Front 1

What are the four general functions of the muscle system?

Back 1

Producing movement - locomotion, manipulation of body, movement of materials into/out of/within body
Maintaining posture - " anti-gravity" oriented up and down
Stabilizing joints - esp. at shoulder and knee where not very stable
Generating heat - thermogenesis; inefficient metabolism, 40% of body mass; maintain core temp

Front 2

Classiby the three types of muscle tissue (according to location, appearance, and type of nervous system control).

Back 2

Skeletal - Attatched to skeleton; striated, voluntary
Smoth - in walls of hollow organs and errector pilli muscles, smooth, involuntary control
Cardiac - most of the heart, striated, involuntary

Front 3

Name and describe the four functional characteristics of muscle.

Back 3

Excitability - respond to stimulus (neurotransmitter, hormone, pH change); electrical current causes muscle contraction; second most excitable
Contractility - create tension b/w ends; able to do work; unique to muscle
Extensibility - can be stretched by force w/o damage; muscles set in opposing pairs
Elasticity - muscle fiber returns to normal length after being stretched; elastic fibers

Front 4

Which of the four functional characteristics of muscle is the most distinguishing or unique characteristic?

Back 4

Contractility - capacity to procude tension b/w its ends

Front 5

Which of the functional characteristics of muscle are protective?

Back 5

Extensibility
Elasticity

Front 6

Name the CT sheath that surrounds individual muscle fibers. Of what type of CT is this sheath composed?

Back 6

Endomysium
Thin layer of areolar CT
Anchored to attatchment points of sarcolemma(membrane of muscle cell) to transfer contraction forces

Front 7

Name the CT sheath that surrounds a fasicle. Of what type of CT is this sheath composed?

Back 7

Perimysium
Fibrous CT (dense irregular CT containing collagen and elastic fibers)
protects blood vessels and nerve fibers that supply the fasicle from contractions

Front 8

Name the CT sheath that holds bundles of fascicles together to create a muscle. Of what type of CT is this sheath composed?

Back 8

Epimysium
Dense irregular CT; thicker than perimysia
Often blends with deep fascia which compartmentalizes regions of body and separates muscles into functional groups

Front 9

Series elastic elements (SEE)

Back 9

endo, peri, and epimysium
Continuous with eachother and ends of muscle fiber
Intertwine with tendons aponeruoses, fibers of periosteum

Front 10

What is the location of the blood vessels and nerves which suply the muscle tissue?

Back 10

Enter and exit muscle near center, one nerve, one vein, one artery, but they branch extensively
Pass w/in CT wrappings
Contained and protected by perimysium

Front 11

Describe the difference between indirect and direct muscle attatchment.

Back 11

Direct - epimysium fused to periosteum of bone or perichondrium of cartilage (tibialis posterior/calf)
Indirect - attatch through tendon or aponerurosis (broad/flat); more common; CT of indirect attatchments intertwines with sharpeys fibers in the bone's periosteum

Front 12

Relative to muscle function, what is the significance of Sharpey's fibers?

Back 12

- project into bones periosteum
- Intertwine with CT of indirect attatchments
- very strong attatchment
- Pull distributed over larger area of the bone

Front 13

In indirect attachments, what tissues are involved in transmitting pulling (i.e. contraction) forces from the muscle fiber to the bone?

Back 13

Tendon - narrow and cord-like
Aponeurosis - broad and flat
CT wrappings of muscle - they intertwine with sharpey's fibers in the periosteum

Front 14

Name and describe the four arrangements of fascicles/fibers within skeletal muscles.

Back 14

Parallel - longitudinal axis; contracts over greatest distance (rectus abdominus, sartorius, biceps brachii
Convergent - fan shape, higher total number of fibers can attatch (pectoralis major, gluteus medius)
Pennate - looks like feather; short fivers, fascicles at angle to tendon; (sememembranosis; rectus femoris, deltoid, gluteus maximus)
Circular - fascicles arranged in circle around external body openings (orbicularis oris around mouth, orbicularis oculis around eyes)

Front 15

What is the advantage of the parallel type of fibers? of the pennate arrangement? the convergant?

Back 15

Parallel - contract over greater distance = greatest ROM and speed
Pennate - limited contraction; favors power/strength
Convergant - powerful, contracts over shorter distance

Front 16

Describe the chemical composition of muscle fibers.

Back 16

75% H2O bye weight
20% protein - some contractile, some enqymes
5% salts (inorganic ones like Ca), pigments, substrates

Front 17

What is the function of myoglobin?

Back 17

Pigment with high affinity for O2
O2 drawn from hemoglobin in blood, through sarcoplasm, into mitochondria

Front 18

What is the most prevalent chemical compound (by weight) in muscle?

Back 18

Water - 75%

Front 19

Describe how the following organelles are modified or adapted for function in skeletal muscle tissue: nucleus, mitochondria, smooth endoplasmic reticulum.

Back 19

Nucleus - multinucleated; 100+ nuclei, just under sarcolema instead of in the center, formed by fusing mesodermal cells
Mitochondria - many, in rows near contractile proteins
Smooth ER - "sarcoplasmic reticulum"; tubular network around individual myofibrils like a sleeve; Ca stored here and released when the signal occurs

Front 20

What gives skeletal muscle fibers a striated appearance?

Back 20

Myofibrils = made of myofilaments = two types: thin and thick filaments
Striations occur where thin and thick filaments overlap each other (in the A band of the sarcomere)

Front 21

What causes each of the bands, zones and lines in a myofibril?

Back 21

A band - dark area where thick and thin fillaments overlap
I band - light area with only thin filaments
H zone - narrow light region within an A band; only thick filaments; only seen in relaxed muscle
M line - divides H zone in 1/2; protein filaments connect filaments + stabilize them
Z disk/line - dark line through I; edge of sarcomere; ancors thin filaments; connects w/ z lines in adjacent muscle fibers

Front 22

What is a sarcomere?

Back 22

Smallest contractile unit of muscle
Makes up the myofiril
Thick filament surrounded by 6 thin filaments
Thin filament surrounded by 3 thick filaments; maximizes contractile ability

Front 23

What is the function of the Z disc?

Back 23

Dark line through I band
Ancors thin and connects to adjacent z lines in other fibers
Elastic filaments made of titin extend from a Z to M
Stabilize myofilaments; enhance elasticity of fibers

Front 24

Identify the two primary types of myofilaments found in myofibrils.

Back 24

Thick filaments - myosin; 2 twisted golf clubs with hinge at head;
Thin filaments - actin; G actin (with active site for myosin heads) made into F actin; anchored to Z, extend towards M

Front 25

Describe the structure of a myosin molecule. How are myosin molecules arranged to make up a thick filament?

Back 25

2 golf clubs w/ handles intertwined; heads on hinge; tails towards M, heads towards Z; heads project in spiraling fashion, head oriented towards thin filament

Front 26

Identify the proteins which make up thin filaments.

Back 26

Actin - G actin polymerized into F actin
Nebulin - stabalize G-actin subunits
Tropomyosin - covers active site
Troponin - holds tropomyosin over active site

Front 27

Which of the proteins that make up thin filaments are regulatory proteins?

Back 27

Tropomyosin
Troponin

Front 28

Describe the structure of an actin molecule. How are individual actin monomers arranged to make up a thin filament?

Back 28

G actin polymerized into helical chain of F actin (a long filament)
Stabalized by Nebulin, a rod-like protein
Active site covered by tropomyosin, which twists around actin filaments
Troponin - 3 subunits; binds to tropomyosin, G actin, and Ca ion

Front 29

Which protein covers up the active sites on the actin filament in a resting muscle fiber?

Back 29

Tropomyosin - held in place by troponin
When Ca low in sarcoplasm
Ca high = it binds to troponin, changing it's shape, pulling tropomyosin and making active site open

Front 30

Describe the location of the sarcoplasmic reticulum (SR) with respect to the myofibrils.

Back 30

SR forms tubular network around individual myofibrils; like a sleeve
On either side of T tubule, enlarged chambers/terminal cisternae form

Front 31

What is the function of the SR and terminal cisternae?

Back 31

Reservoir for Ca2+
T tubules pass signals of voltage change to terminal cisternae to release Ca

Front 32

What is the significance of the Ca2+ release channels and the Ca active transport pumps in the SR?

Back 32

Release channels - Ca goes out of SR into sarcoplasm very fast, triggers muscle contraction
Pumps - brings the Ca ions back into the SR for the next contraction signal

Front 33

What are the T tubules? Where are they located?

Back 33

Tunnel-like invaginations of sarcolemma into sarcoplasm at right angles
Continuous with sarcolema; filled with extracellular fibers
At A band-I band junction
Composition: extracellular fluid

Front 34

What is the function of the T tubules?

Back 34

All muscle fibers contract simultaneously
A way to internally conduct elecrical events

Front 35

Why is the triad of functional significance?

Back 35

- T tubule and 2 terminal cisternae
- Integral proteins of T tubule = voltage sensors, pass signal
- Integral proteins of terminal cis receptors and Ca release regulators
Both extend into intermembrane space

Front 36

Describe the anatomy of a muscle, beginning with myofibrils

Back 36

Myofibrils - repeating sarcomeres made up of thin and thick filaments, with active heads regulated by troponin and tropomyosin
Surrounded by sarcoplasmic reticulum and T tubules
Many mitochondria and nuclei, wrapped in endomesium to form muscle fiber
Bundles of fibers = fascicles surrounded by perimysium
Whole muscle surrounded by epimysium and deep fascia, which lines body walls and wraps limbs

Front 37

Muscle contraction is currently best described by the sliding filament theory. Why is this name appropriate for the contraction process?

Back 37

Thin filaments pulled past thick, creating sarcomere contraction
Proposed by Huxley and Hanson

Front 38

What happens to the A band, I band, Hzone, and Z disks during contraction? To sarcomere length?

Back 38

H zone + I bands get smaller
A bands don't change, but do get closer together
Maximal contraction - H band disappears
Z disks/lines get closer together
Sarcomere shortens

Front 39

Which myofibril structures or regions change length during the contraction process?

Back 39

H zone and I bands get smaller
Sarcomere shrinks overall

Front 40

What is the role of Ca2+ and the regulatory proteins in the sliding filament mechanism?

Back 40

Ca binds to troponin when it's in high conc. in the sarcoplasm
Troponin changes shape, pulling tropomyosin away from active sites on G actin
Active site can interact with the myosin heads now

Front 41

Specifically, how do troponin and tropomyosin help regulate the contraction process?

Back 41

Tropomyosin is a rod shaped protein; twists around actin strands, covering active sites
Troponin has 3 globular subunits; binds to G actin, Tropomyosin; Ca; can pull tropomyosin away from active binding site when Ca is bonded

Front 42

What is the role of ATP and the myosin crossbridge in the sliding filament mechanism?

Back 42

ATP hydrolysis moves myosin head to high e/cocked position
When G actin active site is open, head latches on, releasing ADP + P1; this release causes shape change/power stroke towards center of sarcomere

Front 43

At what point in crossbridge cycling does ATP become hydrolyzed, and provide energy for activation of the myosin head?

Back 43

Step 1 and 4
ATP has bound to myosin head, making it let go of the active site, now it hydrolyzes and cocks head back again
the "reactivation of myosin head"

Front 44

At what point in crossbridge cycling does the power stroke occur?

Back 44

Step 2: power stroke
Myosin attatches to active site, causing ADP +P1 to be released
Release changes shape, pivoting head towards center

Front 45

When is the (ADP + P1) which fueled the power stroke in crossbridge cycling released?

Back 45

At the beginning of the power stroke - it's release induces the shape change in the myosin head

Front 46

What causes myosin to detach from actin after the power stroke is completed?

Back 46

New ATP binds to head, making crossbridge detatch from active site on actin
Still in low e state but w/ATP attatched to head

Front 47

Describe the structure of the neuromuscular junction.

Back 47

Functional, not physical contact
B/w axonal endings/synaptic terminals of alpha-motor neuron and muscle fiber
Gated Ca ion channels in membrane; synaptic terminals = mitochon. and synaptic vesicles with acetylchoine/neurotransmitter
Motor end plate/sarcolema - many invaginations w/ACH receptors associated with ligand-gated Na+ channels

Front 48

What specializations of the muscle fiber (at the motor end plate) enable it to resp to signals from the motor neuron?

Back 48

Invaginatinos = surface area
ACH receptors associated with ligand/ACh-gated Na+ channels
ACh binds = channels open and Na floods into sarcoplasm

Front 49

What is the synaptic cleft?

Back 49

Space b/w motor end plate and synaptic terminals
Filled with acetylcholinesterase (AChE), which breaks down ACh quickly

Front 50

What is acetylcholine? What role does it play at the neuromuscular junction?

Back 50

- Neurotransmitter
- Nerve impulse/action potential triggers release into synaptic cleft
- Diffuses + opens ligand-gated Na+ channels;
Na rushes in triggering muscle action potential, which makes Ca flood into sarcoplasm

Front 51

Describe the process of signal transmission at the neuromuscular junction (i.e., communication of nerve AP to the muscle fiber).

Back 51

Nerve impulse/AP triggers ACh release into synaptic cleft
ACh opens ligand gated receptors on motor end plate
Na+ rushes into muscle fiber, triggering muscle action potential
MAP triggers Ca release from terminal cisternae into sarcoplasm

Front 52

What prevents prolonged stimulation of the muscle fiber by acetylcholine (ACh)?

Back 52

AChE - acetylcholinesterase
In synaptic cleft
Breaks down ACh quickly
1 nerve impulse = 1 contraction

Front 53

What two factors permit relaxation?

Back 53

When Ca2+ levels are not elevated in sarcoplasm - ATP depemdent Ca pumps in SR re-sequester Ca
ATP runs out, so myosin head can't detatch anymore or be cocked back

Front 54

Describe the entire process of excitation-contraction coupling, beginning with a nerve impulse in a motor neuron.

Back 54

Synaptic vesicles release ACh into synaptic cavity; opens Na+ channels in motor end plate
Na floods in creating muscle action potential; sweeps along sarcolema and T tubules
Ca - out of terminal cisternae into sarcoplasm fast b/c of calsequestrin/high conc.
Ca binds to troponin, pulls tropomyosin away from active actin site, head latches on, ADP released = shape change; ATP = let go, hydrolysis = cock again
Ca conc falls as pumps re-sequester Ca; tropomyosin covers sites again; stops

Front 55

Identify two ways in which ATP is used to directly power muscle contraction events.

Back 55

ATP hydrolysis cocks myosin head
Release of ADP changes shape and creates power stroke
ATP attatchment makes head let go

Front 56

Physiologically speaking, what is the value of ATP's high energy phosphate bonds?

Back 56

Hydrolysis - breaking bond releases energy
Used to perform cellular work, eg. crossbridge cycling

Front 57

Where is most of the cell's ATP produced?

Back 57

Mitochondria - aerobic respiration

Front 58

Which of the avenues of ATP production is/are anaerobic? aerobic?

Back 58

Anaerobic - ATP from creatine phosphate; ATP from anaerobic glycolysis and lactic acid formation
Aerobic - ATP from aerobic respiration

Front 59

Which of the avenues of ATP production provides energy to fuel brief, high intensity activity?

Back 59

Anaerobic glycolysis
In cytoplasm; initial series in glucose breakdown
Forms pyruvic acid and if if a lot is formed, converted into lactic acid

Front 60

Which of the avenues of ATP production provides energy to fuel prolonged, submaximal activity?

Back 60

Aerobic respiration
Uses fats, proteins and carbs
60-80% of energy released as heat

Front 61

What happens to pyruvic acid when there is not enough O2 present to completely catabolize it?

Back 61

Converted to lactic acid
Used as fuel by liver, skeletal and cardiac muscle, kidney; converted back to glucose in liver and kidney
Accumulates = acidic pH interferes w/enzyme activity

Front 62

What is muscle fatigue?

Back 62

Physiological inability to contract despite continued neural stimulation

Front 63

What factors contribute to onset of muscle fatigue?

Back 63

Depletion of fuel reserves
Lactic acid accumulation
Insufficient O2 supply
Changes in central nervous system
Decreased signal effectiveness at NMJ

Front 64

What is meant by the term recovery O2 uptake?

Back 64

Higher than normal O2 consumption during recovery
"Excess postexercise oxygen consumption" - EPOC
Not just attributed to metabolic events during exercise

Front 65

What physiologic factors are associated with recovery O2 uptake?

Back 65

Body temp. elevation - increases body metabolic rate
Increased rate/depth of breathing, higher heart rate - support high metabolic rate
Sweating - get rid of heat
Replenishing muscle e. stores
Tissue repair

Front 66

Name and describe the muscle fiber's three avenues of ATP production.

Back 66

ATP from creatine phosphate (CP) - most rapidly available; 10 sec cont.; creates ATP and Creatine; enzyme = creatine kinase (CK); after exercise reverses
From anaerobic glycolysis + lactic acid formation - initial series of rxns in glucose breakdown; forms pyruvic acid (taken into mitochondrial respiratory chain), too much builds up = converted into lactic acid
From aerobic respiration - High ATP yield; in mitochondria, releases lots of heat