1
Q
Types of muscles
A
- skeletal muscle: striated, voluntary, multiple nuclei
- Cardiac muscle: striated, involuntary, intercalated disks
- smooth muscle: nonstriated, involuntary, visceral
2
Q
General functions of muscles
A
Movement: production movement of the body as a whole (locomotion) or its parts
Thermogenesis: Heat production
Posture: maintains body position through partial contractions
3
Q
Skeletal muscle function
A
Excitability: “irritability” the ability to respond to regulatory mechanism, such as a nerve signal
Contractibility: the ability to contract or shorten “pulling the ends together”
Extensibility: the ability to extend or stretch
4
Q
Muscles are named according to what?
A
Location
Function
Shape
Direction of fibers
Number of heads
Points of attachment
Size of muscle
5
Q
Skeletal muscle structure
A
- the structure called skeletal muscles are considered organs
- six muscles shaped are often used to describe and categorize skeletal muscle
6
Q
Parallel
A
- long strap-like muscle with parallel facials
- most typical
7
Q
Convergent
A
Fascicles that radiate out form a small to a wider point of attachment
8
Q
Pennate
A
- “feather-like”
- unipennate -> have fascicles that anchor to only one side of the connective tissue shaft
- bipennate -> have a double-feathers attachment point
- multipennate -> have numerous interconnective quill-like fascicles converging on a common point of attachment
9
Q
Fusiform
A
Have fascicles that may be close to parallel in the center or “belly”, of the muscle but converge to a tendon at one or both ends
10
Q
Spiral
A
Have fibers that twist between their points of attachment
11
Q
Circular
A
“Orbicular”/“sphincters”
Circle body tubes or openings
12
Q
Origin
A
The point of attachment that odes not move when the muscle contracts
13
Q
Insertion
A
- the point of attachment the moves when the muscle contracts
- The insertion bone therefore moves along a “line of force” toward the origin bone when muscle shortens
- although the origin and insertion are convenient terms, the do not always provide the necessary information needed to understand the full functional potential of muscle action
14
Q
Skeletal muscles almost always do what
A
Almost always act in groups rather than singly
15
Q
Agonist
A
“Prime mover”
- used to describe a muscle that directly performs a specific movement
16
Q
Antagonist
A
- muscles that, when contracting, directly oppose the agonists
- important in providing precision and control during contraction of the prime mover
17
Q
Synergists
A
- muscle that contract at the same time as the prime mover
- assist the agonist in to produce a more effective movement
18
Q
Fixator muscles
A
- generally, function as joint stabilizers
- maintains posture or balance during contraction or prime movers acting on joints in the arms or legs
- assist the agonist, which classify them as a type of agonist
19
Q
Myocytes
A
Muscle cells
Often called muscle fibers
These cells are long, thin, thread-like shaped
Multi mucleated
20
Q
Sarcolemma
A
Plasma membrane of a muscle fiber
21
Q
Sarcoplasm
A
The cytoplasm of a muscle fiber
22
Q
Sarcoplasmic reticulum
A
- network of tubules and sacs that temporarily store and release calcium ions (Ca++)
- “muscle cell smooth ER”
23
Q
T-tubules
A
- a system of transverse tubules that cover sarcoplasm, at a right angle to the long axis of the cell
- the tubules allow electrical signals to travel along the sarcolemma and deep into the muscle fiber
24
Q
Triad
A
- structure that allows electrical impulses traveling along a T-tubule to stimulate the membranes of adjacent sacs of the SR
- at rest calcium ion pumps in the SR pump Ca++ into the SR
- during activation after an electrical impulse travels along the sarcolemma and down the t-tubule, the Ca++ gates open in the SR in response to the voltage fluctuation
- flowing the sarcoplasm with Ca++
25
Actin
“Thin filament”
- protein molecules (G-actin) that are strung together like beads to form two fibrous strands (F-actin) that twist around each other to form a thin myofilament
26
Myosin
“Thick filament”
- myosin proteins that are bundles together with doubled “heads” what protrude out of the
- Actin and myosin are chemically attracted to each other, when they are joined together, they form cross-bridges
27
Troponin
- protein molecules attached to tropomyosin, spaced at intervals along the thin filament
- the protein molecule chemically bonds with Ca++
28
Tropomyosin
- protein molecule that forms a very thin string along the active site of the actin
- blocking the chemical bond with myosin
29
Myofibrils
Bundle of very fine myofilaments
30
Myofilaments
- the smallest fibers contained in muscle cells
- the contractile units of the muscle cell
31
Thick and thin filaments
Overlapping thick and thin filaments create sarcomeres
32
Types of sarcomeres
- Z-line: zigzag shape, a dense disk that anchors actin filaments together (one sarcomere = Z-line to Z-line)
- M-line: M-protein molecule in the middle of the sarcomere, anchors and stabilizes myosin filaments together
- A-band: the segment that runs the entire length of the myosin filaments (“anisotropic band”) ONLY MYOSIN
- I-band: the segment that includes the Z-disk and the ends of the actin filaments where they do not overlap the myosin filaments (“isotopic filaments”) ONLY ACTIN
- H-band: the middle region of the myosin filament where they do not overlap the actin filament (“heller” = bright)
33
Elastic filaments
- composed of a protein called titan (connection)
- anchor the myosin filaments to the Z-disk
- believed to give myofibrils elasticity
34
Dystrophin
- a protein that holds the actin filaments to the sarcolemma
- plays a significant tole in muscular dystrophy
35
Motor unit
- composed of a motor neuron and the skeletal muscle fibers innervated by the motor neurons atonal terminals
36
Motor neuron
- specialized type of nerve cells
- connected to the sarcolemma of a muscle fiber at the folded motor endplate
37
Neuromuscular junction (NMJ)
- type of connection called a synapse and is characterized by a narrow gap or synaptic cleft, across with neurotransmitter molecules transit signals
38
Acetylcholine (Ach)
- a neurotransmitter, which is a release via vesicles into the synaptic cleft
- diffuse across the microscopic gap to contact the sarcolemma of the adjacent muscle fiber
- stimulating/signaling the T-tubules to “trigger” the SR release CA++
39
Sliding filament theory
- theory that explains how muscles contract to produce force
- actin and myosin filaments within the sarcomeres of muscle fibers bind to create cross-bridges and slide past one another, creating a contraction
40
Step by step sliding filament theory
1) an electric signal (action potential) down the motor neuron
2) stimulating the motor unit
3) Ach is release within the NMJ
4) depolarizing the sarcolemma
5) action potential travels down the t-tubule
6) stimulating the sarcoplasmic reticulum
7) releases Ca++ ions
8) Ca++ binds with troponin
9) displacing tropomyosin
10) allowing actin and myosin to form a cross-bridge
11) myosin pulls actin down the length of myosin
12) drawing the Z-line, closer to the M-line
- when this happens within sarcomeres the entire muscle belly can contract and shorten
41
Cardiac and smooth muscles have special features
- involuntary
- able to contract entirely on their own in absence of nerve stimulation
- cardiac muscle cells are joined by intercalated disks
- have gap junctions allowing cells to electrically stimulates the next one
- smooth muscle cells joined by gap junctions, allowing cells to activate each other
- cardiac and smooth muscle cells spend to stimulation from autonomic nervous system, which can modify the degree of contraction
42
Muscle fibers types
Type 1: slow twitch, oxidative, aerobic in nature, red in color, endurance type fibers
Type 2: fast-twitch, nonoxidative, anaerobic in nature, pink or white in color, white meat, can be separated into Type IIa (oxidative) and type IIx (glycotic), power type fibers
Type IIA: fast twitch, oxidative/glycolytic
Type IIX: fast twitch, glycolytic
43
Muscle fibers
- most skeletal muscle simultaneously contains all three types of fibers - but motor units only contain one type
- this means there are actually Type I, IIA, and IIX motor units, not just muscle fibers
- each fiber type has different structural, functional, and metabolic aspects
- type 1: small motor unit, oxidative, slow contraction
- type 2: large motor unit, glycolytic, fast contraction
44
Hennemen’s size principle:
- “under load, motor units re recruited from smallest to largest”
- in practice, this means that slow-twitch, low-force, fatigue-resistant muscle fibers are activated before fast-twitch, high-force, less fatigue-resistant muscle fibers
45
Muscle fiber type can be assessed in two ways:
- muscle needle biopsy
- nuclear magnetic resonance spectroscopy
- taking a “snapshot” of the fibers
- by counting the fibers we can estimate a % balance between the fast twitch and the slow twitch. We could also attempt to estimate the diameter of the fibers
46
Fiber typing differences
The fast twitch to slow twitch ratio varies between muscles within individuals and between individuals
Highly dependent on genetics
Average Person:
- typically 50:50 between type 1 and type 2
- no difference between sex
- large variation between individuals
47
Muscular dystrophy
- genetic disease
- modified dystrophy protein enable leakage of Ca++ into cells
- extra Ca++ activates enzymes that destroy muscle proteins
- muscle weakening and wasting
- muscle mass is replaced with fibrous connective tissue
- life expectancy is approximately 30 years
48
Tetanus
- infection of deep wound by bacteria, Clostridium tetani
- bacteria produce tetanus toxin, which causes muscles to contract forcefully
- death due to respiratory failure
- preventable to tetanus vaccine
49
Muscle cramps
Often caused by dehydration and ion imbalances
50
Pulled muscles
Result from overstretching of a muscle, fibers then tear apart
51
Fasciitis
Inflammation of the fascia
- Plantar fasciitis: sole of the foot
52
What is the primary purpose of the Z-line? Of the M-line?
The z-lines primary purpose is to anchor actin
The m-lines primary purpose if to anchor myosin
53
Why is calcium important for the body
Calcium initiates muscle contractions
Human Biology
flashcards
Decks in class (25)
# Cards
-
Chapter 145
-
Chapter 275
-
Chapter 362
-
Unit One Quizzes57
-
Chapter 458
-
Metabolism And Electrolytes33
-
Chapter 549
-
Body Systems And Cardiovascular Disease39
-
Chapter 669
-
Exam 153
-
Chapter 751
-
Chapter 945
-
Unit 2 Quiz Questions39
-
chapter 1042
-
Chapter 1172
-
Chapter 1257
-
Exam 267
-
Chapter 1353
-
Unit 3 Quiz48
-
Chapter 1448
-
Chapter 1536
-
Chapter 1637
-
Exam 345
-
Chapters 24 And 2562
-
Final Exam88
