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Anatomy fall semester > chapter 9 muscle and muscle tissue > Flashcards

chapter 9 muscle and muscle tissue Flashcards

1
Q

what are the four muscle functions?

A
  • movement (voluntary or involuntary)
  • Body posture and body position (muscles work to hold us up against gravity)
  • Joint stability (muscles and tendons reinforce joints)
  • Maintaining body temperature (muscle contraction produces heat)
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2
Q

what are the types of muscle tissue?

A
  • skeletal muscle tissue
  • smooth muscle tissue
  • cardiac muscle tissue
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3
Q

skeletal muscle tissue

A
  • voluntary muscle tissue (movement of body parts)
  • attaches to and uses skeleton
  • creates the most force (Strongest), but needs the most rest
  • adaptable (change amount of force)
  • jaw muscle
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4
Q

smooth muscle tissue

A
  • involuntary muscle tissue
  • moves fluid and substances through body
  • found in the hollow organs of body except for heart
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5
Q

Cardiac muscle tissue

A
  • involuntary muscle tissue (found in heart)
  • function: moves blood through body
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6
Q

innervation

A
  • each muscle receives 1 motor nerve(has a lot of neuron in it)
  • function: nerve ending controls activity whether its contracting or relaxing (motor neuron stimulates muscle fibers to contract)
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7
Q

vascularization

A
  • each muscle recieves 1 artery, 1+ vein (need 1 artery to bring nutrient blood so skeleton muscle can use to provide energy it needs)
  • brings nutrients and oxygen, remove waste (CO2, lactic acid)
  • ATP
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8
Q

skeletal muscle attachments

A
  • for muscle to produce movement, it must attach to bone (or naother tough structure)
  • our muscle use our bones like levers
  • when a muscle contracts, it pulls (or pushes) on a bone to produce movement
  • attachment can be direct or indirect
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9
Q

direct

A

muscle fuses directly to bone or cartilage

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10
Q

indirect

A
  • involves tendon
  • more common because tendons are tougher and more stable
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11
Q

tendon

A

a band of dense fibrous connective tissue that connects a muscle to a bone (tough to break, don’t heal as well)

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12
Q

what are the longest and largest cells in the body?

A
  • Skeletal muscle cells
  • Myocytes, muscle fibers
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13
Q

sarcolemma

A

plasma membrane of muscle fibers (Synapse of motor neuron and muscle fiber to activate an AP to stimulate a muscle tendon)

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14
Q

sarcoplasm

A
  • cytoplasm of muscle fibers
  • contains high numbers of Glycosomes and myoglobin
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15
Q

glycosomes

A
  • organelles that store glycogen
  • glycogen is a polysaccharide that is converted to glucose for ATP production in skeletal muscle (found in meat)
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16
Q

Myoglobin

A

red pigment organelle that stores oxygen in muscle fibers (oxygen is needed for atp production)

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17
Q

myofilaments

A
  • protein filaments in muscle tissue
  • thick filament (myosin) and thin filament (actin)
  • actin an myosin interact during muscle contraction. They both need to interact to generate force and muscle contraction–> their molecular structure is important for that to happen
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18
Q

myosin filaments

A
  • composed of 6 chains–>4 light chains and 2 heavy chains
  • myosin heads are foun at end of each heavy chain (each myosin head has 2 binding sites: 1 for ATP, 1 for actin)
  • Myosin head uses ATP to link two types of myofilaments during contraction
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19
Q

Actin filaments

A
  • chains of G actin proteins with myosin binding sites
  • myosin head binds to myosin binding site of actin during muscle contraction, however they can’t interact with each other whenever
  • regulatory proteins of actin control if/when myosin head can bind (prevents actin and myosin from interacting with each other when we don’t want them too bc it can produce involuntray muscle contraction which is not what we want)
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20
Q

2 regulatory proteins associated with actin filaments

A
  1. tropomyosin
  2. troponin
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21
Q

tropomyosin

A
  • arranged along length of thin filament
  • blocks mosin binding sites on actin filament when muscle is relaxed
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22
Q

Troponin

A
  • globular protein associated with tropomyosin (helps hold tropomyosin in place during muscle relaxation
  • binds tropomyosin to position it on the actin filament
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23
Q

myofibrils

A
  • rod like organells of muscle cells (one muscle fiber is made up of several myofibrils, one myofibril is made up of bands of myofilaments)
  • myofilaments overlap in some regions of the myofibril to produce dark bands (this is what creates striations of skeletal muscle)
24
Q

myofibrils are composed of alternating…..

A

A bands and I bands

25
Q

A bands

A
  • region of myofibril where actin and myosin filaments overlap
  • H zone at the center of A band has only myosin filaments
26
Q

I band

A
  • region of myofibril with only actin filaments
  • Z disc at center holds the actin filaments in place (prevents them from shifting to they act interact with myosin)
27
Q

sacromere

A
  • A band and I bands create the sarcomere
  • A sarcomere is th region of a myofibril found between 2 successive Z discs
  • the sacromere is the smallest contractile unit of skeletal muscle tissue
28
Q

T-Tubules

A
  • Extensions of the sarcolemma that wrap around deeper myofibrils
  • increase surface area of muscle fiber sarcolemma (changes in membrane potential can reach myofibrils not in direct contact with sarcolemma)
29
Q

Sarcoplasmic reticulum

A
  • smooth endoplasmic reticulum of muscle
  • highly branched, wraps around myofibrils
  • Form terminal cisterns around T-tubules (stores and releases intracellular Ca2+ for muscle relaxation and contraxtion)
  • 2 terminal cisterns surround 1 t-tubule to form a triad
30
Q

The Neuromuscular Junction

A
  • site of synapse between a somatic motor neuron and a muscle fibers
  • neurotransmitter released: acetylcholine (ACh)–> excitatory effect, which stimualr muscle fibers to contract
  • Sarcolemma at Synaptic cleft folded to form junctional folds (folds increase surface area of muscle fiber sarcolemma)
31
Q

For stimulation of muscle fiber to occur, the following steps must take place

A
  1. Events at the neuromuscular junction
  2. generation of action potential across sarcolemma
  3. excitation contraction coupling
  4. cross bridge formation and muscle contraction
32
Q

The neuromuscular junction

Events at the neuromuscular junction

A
  • Review ch11 (transmission of action potential)
  • ACh is released and binds to chemically gated ion channels on the sarcolemma
33
Q

The neuromuscular junction

generation of action potential across sarcolemma

A
  • ACh binds to and opens ion channels on sarcolemma to create end plate potential (EPP)
  • EPP is a graded potential specific to muscle tissue
  • EPP depolarizes sarcolemma (if strong enough–> action potential generated on sarcolemma)
34
Q

The neuromuscular junction

Excitation-contraction coupling

A
  • occurs when action potential spreads from sarcolemma to T-tubules
  • when action potential arrives at T-tubules–>voltage gated proteins in T-tubules change shape
  • When T-tubule proteins change shape–> Ca2+ channels in terminal cistern forced open forces open
  • result: Ca2+ released from sarcoplasmic reticulum and flows into cytosol of muscle fiber
35
Q

The neuromuscular junction

Cross bridge formation and muscle contraction

A
  • once Ca2+ enters cytosol–> interaction between actin and myosin filaments can begin
  • Cross bridge: the attachment of myosin to actin
36
Q

The neuromuscular junction

the process of cross bridge formation

A
  1. Ca2+ binds troponin–> troponin changes shape
  2. change in troponin shape causes tropomyosin to roll on side
  3. when tropomyosin is moved–> myosin binding site on actin is exposed
  4. myosin head splits ATP into ADP + Pi (myosin head binds to actin when bound to Pi)
  5. ADP + Pi is released from myosin head, causing the myosin head to bend (myosin head “pulls” actin filament, this is called the power stroke”
  6. Myosin head binds to another ATP causing myosin head to detach from actin binding site
  7. The myosin head binds to a different actin binding site after it splits the new ATP molecule

Steps 4-7 repeat until muscle contraction ends or ATP/Ca2+ run short

37
Q

Repeated formation/breaking of cross bridges between myosin and actin results in myosin….. along actin filament

A

“walking”

38
Q

Ending cross bridge formation and muscle contraction

A
  • motor impulses no longer sent to muscle fibers (AP to muscle fiber ends)
  • Ca2+ is returned to Sarcoplasmic reticulum
  • When Ca2+ levels in sarcoplasm drop, it can no longer bind to troponin
  • Troponin returns to original shape (tropomyosin moves–> covers actin binding sites)
39
Q

sliding filament model of contraction

A
  • During contraction, actin filaments “slide” over myosin filaments
  • myosin head form and break multiple cross bridges with actin
  • Myosin heads “slide” thin filaments toward center of the A band (filaments do not change length)
  • when the filaments “slide” the sarcomere shortens and generates tension in the muscle (this is wh muscle fibers shorten when they contract!)
40
Q

Motor units

A
  • a single motor neuron can serve multiple muscle fibers
  • BUT–>A single muscle fiber is served by only one motor neuron
  • Motor unit: a single motor neuron and all the muscle fibers it innervates
41
Q

Motor unit rules

A

Rule 1: when the motor neuron fires–> all fibers it innervates will contract
-fibers innervated by a single motor neuron are spread out over entire muscle–> not clumped together!
Rule 2: number of muscle fibers a single motor neuron innervates influences movement
-motor neuron innervating few fibers (less than 12 muscle cells)–> direct message or precise movement such as fingers or face
vs
-motor neuron innervating many fibers (up to 100 of muscle fibers)–> coarse movement or not as precise, such as hamstrings or muscles in back

42
Q

graded muscle contraction

A
  • sustained muscle contraction that is modified by the nervous system to produce varying amounts of force
  • muscle contractions can be graded 2 ways:
    1. temporal summation–> increasing the frequency of stimulation of a muscle
    2. motor unit summation–> increasing the strength of stimulation of a muscle
43
Q

Temporal summation

A
  • increasing the firing rate of a motor neuron can generate more force at the muscle
  • fire stimuli in rapid succession–> the second twitch hits the muscle before the first twitch has ended
  • effect: muscle tension increases
  • start to repolarize but before, we hit it with another AP which generates more tension
44
Q

temporal summation can lead to 2 forms of tetanus:

A
  1. unfused (incomplete) tetanus
  2. fused (complete) tetanus
45
Q

unfused (incomplete) tetanus

A

rate of stimulation creates a sustained and quivering muscle contraction

46
Q

Fused (complete) tetanus

A

rate of stimulation creates smooth, sustained muscle contraction
-no relaxation occurs

47
Q

motor unit summation

A
  • recruitment of additional motor units in a muscle to generate more force during contraction
  • increase the number of motor units used over time during contraction
  • size principal of motor unit summation
  • motor units with smallest muscle fibers recruited first
  • motor units with largest muscl fibers recruited last–> create more force
  • motor units recruited asynchronously–> some contracting, others relaxing
48
Q

Muscle tone

A
  • relaxed muscles are always slightly contracted–> creates muscle tone
  • does not produce movement
  • muscle tone contributes to joint stability, posture, fibers remian responsive
  • muscle tone keeps muscle tissue healthy and responsive, stabilizes joints, maintains posture
  • loss of muscle tone leads to loss of responsiveness (muscle will not respond to stimuli, ex: stroke victims)
49
Q

Energy requirments for contraction

A
  • ATP is necessary for cross bridge formation to occur
  • sources of ATP for muscle contraction:
    1. creatine phosphate
    -creates ATP from ADP + phospahte
    -enough creatine phosphate stored by muscle cell to supply -15s of ATP
    2. Anaerobic respiration
    -glucose used to produce 2 ATP + pyruvic acid
    -some pyruvic acid may be converted to lactic acid
    -Anaerobic repsiration + creatine phosphate= 1 minute of ATP
    3. Aerobic respiration
    -creates 95% of ATP used by muscle for contraction
    -produce 30 ATP per glucose molecule
    -Used for endurance activities (as long as O2 is available)
50
Q

Muscle fatigue

A
  • we can produce ATP–> but it is not unlimited
  • muscle fatigue occurs–> muscle is physiologically incapable of contracting
  • If a muscle cell uses every last molecule of using ATP then it will have no energy for other reactions and it will die. The fatigue prevents the muscle from using all the ATP so they it can stay alive
  • Rate & duration of fatigue depends on activity
  • High intensity exercise
  • Low intensity exercise (muscle cells will fatigue much slowly but the duration/recovery is longer)
  • ^^high is opposite
51
Q

muscle contraction: force

A
  • Force of contraction is determined by the number of cross bridges formed between myosin and actin filaments
  • more cross bridges=more force
52
Q

muscle contraction: force

influenced by 4 factors

A
  1. frequency of stimulation–> temporal summation
  2. Number of muscle fibers recruited–> motor unit summation
  3. Size of muscle fiber
    -bulkier muscle generates more tension, creates more force
    -hypertrophy–> increase size of muscle fibers in muscle to increase force generated
    -rate of hypertrophy dependent on genetics, sex, nutrients, etc
  4. deree of muscle stretch
    -force a muscle creates varies with how much the muscle is stretched
    -length tension relationship: the maximal force produced will differ based on the degree of muscle stretch or contraction (more muscle stretch then less force is generated)
53
Q

Smooth muscle tissue

Gross anatomy

A
  • hollow organs in the body have smooth muscle tissue
  • most organs have 2 layers of smotth muscle tissue thatnever contract simultaneously in the same area:
    1. Longitudinal layer: muscle fibers run the length of the organ
    -more superficial
    2. circular layer: muscle fibers run the circumference of the organ
    -deep to longitundinal layer
54
Q

Differences from skeletal muscle fibers:

A

1.Smooth muscle fibers are short, spindle-shaped
2.Covered only by endomysium
3.No neuromuscular junctions–> innervation forms varicosities
-Autonomic fibers have bulb-like swellings scattered over smooth muscle tissue surface
-Importance: creates diffuse junctions
Wide synaptic clefts that release neurotransmitter to multiple muscle fibers
4. Smooth muscle fibers have no T-tubules & less sarcoplasmic reticulum
-Sarcoplasmic reticulum releases only a small amount of Ca2+
-Caveolae: invaginations of sarcolemma of muscle fiber
-Have Ca2+ ion channels
-Where does most Ca2+ come from? Extracellular fluid
5. Muscle fibers have gap junctions
Depolarization spreads from cell to cell
6. No striations or sarcomeres
-There are still thick and thin filaments, but:
-Fewer thick filaments overall
-Myosin heads found along entire length of thick filament
7. No troponin
-Calmodulin–>protein that acts as Ca2+ binding site
8.Thick and thin filaments arranged diagonally
-Filaments spiral down axis of muscle fiber
-Effect:when a muscle fiber contracts–> it twists

55
Q

Types of smooth muscle

A

1. Unitary Smooth Muscle
* Everything described so far are characteristics of unitary smooth muscle
* Much more commonfound in hollow organs

2. Multi-Unit Smooth Muscle
* Have no gap junctions or spontaneous depolarization
* Muscle fibers are structurally independent
* Forms motor units
* Have graded contractions with recruitment

-Found in arrector pili, smooth muscle of airways, internal eye muscles

56
Q

Regulation of contraction

A

1. Neural Regulation
* Neurotransmitter can excite or inhibit smooth muscle tissue
* Response is dependent on receptor molecules on sarcolemma

2. Hormones & Local Chemical Factors
* Some smooth muscle has no innervationrespond only to local chemicals
* Others spontaneously depolarize
* Act by enhancing or inhibiting Ca2+ entry into sarcoplasm

57
Q

unique features of smooth muscle

A

1. Response to stretch
* Smooth muscle responds to stretch by contracting
* Importance: increases ability to push substances through organ
* Stress-relaxation response: if an organ is filled slowlyit will not contract strongly

2. Length and tension changes
* Smooth muscle can stretch more & can generate more tension while stretched
* Can still contract when stretched 150% its length

Anatomy fall semester (17 decks)

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