Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Spring 2014 > Physiology - Exam 3, Deck #1 - Muscles > Flashcards

Physiology - Exam 3, Deck #1 - Muscles Flashcards

1
Q

What are Smooth Muscles?

A
  • Slower, more sustained contractions;
  • Involuntary;
  • No clear filament organizations (NO sarcomeres);
  • Stomach, arteries, etc.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are Cardiac Muscles?

A
  • Heart;
  • Short, branches muscle fibers connected by INTERCALATED DISCS;
  • Striated
  • Forms a “mesh”;
  • When one-cell contracts they all do because the action potential is propagated from one cell t the next through intercalated discs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are Skeletal Muscles?

A
  • *Voluntary and Striated;
  • Comprise 90% of our total muscles mass;
  • Voluntary muscles arranged in ANTAGONISTIC pairs;
  • Muscles are attached to tendons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How are skeletal muscles attached to bones?

A
  • By TENDONS on each end of the bone;
  • Contracting muscles cause tension on tendons which move bones at a joint;
    1. INSERTION = the more movable attachment;
    2. Insertion is pulled toward the ORIGIN = less moveable attachment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Flexors vs. Extensors

A
  • Flexors DECREASE angle of joint;

- Extensors INCREASE angle of joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is Agonist Muscle?

A
  • Prime mover of any skeletal movement;

- ANTAGONISTIC muscles are flexors & extensors that act on the same joint to produce OPPOSITE actions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the Epimysium of muscles?

A

Sheaths of fibrous connective tissue from tendons that extend around and into skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are Fascicles of muscles?

A

Inside the muscle this connective tissue divides muscle into columns called FASCICLES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the Perimysium of muscles?

A

Connective tissue around fascicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are skeletal muscles composed of?

A
  • Numerous muscles fibers (cells) ranging from 10 to 80 microns in diameter;
  • In most muscles the fibers extend the entire length of the muscle;
  • All but about 2% of the fibers are innervated by on ONE nerve ending located near the middle of the fiber;
  • Muscle fibers are similar to other cells except are MULTINUCLEATE & STRIATED
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the Sarcolemma?

A

The plasma membrane surrounding muscle fibers;

-Consistes of a cell membrane and an outer coat that fuses with a tendon fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are Tendon Fibers

A

Tendon fibers are collected into bundles to form muscle tendons that are inserted into bones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are Myofibrils?

A
  • Found with muscle fibers and contain numbers FILAMENTS;
  • Myofibrils are 1 moron in diameter & extend length of fiber;
  • Composed of Actin and Myosin Filaments
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are Myofilaments?

A

Myofilaments are composed of thick & thin filaments lying side-by-side that give rise to bands which underlie STRIATIONS;

  1. ~ 1500 Myosin filaments = THICK;
  2. ~ 3,000 Actin filametns - THIN
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the function of Myofilaments?

A

Filaments are large polymerized protein molecules that are responsible for MUSCLE CONTRACTIONS;
-Filaments partially interdigitate and cause the myofibrils to have alternate light and dark bands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are “A Bands”?

A

“A band” is DARK;

-Contains thick filaments = mostly MYOSIN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the “H band” or “H zone”?

A

-Light/clear area at center of A band is “H band” = area where actin & myosin don’t overlap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are “M Lines”?

A

M lines are structural proteins in the middle of A bonds;

-Join thick myosin filaments together and anchor them during contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are “I Bands”?

A

I band is LIGHT;

  • Contains thin filaments = mostly ACTIN;;
  • At center of I band is Z line/disc where actions attach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a “Z Disc”

A

Z-discs run perpendicular to actin filaments and attaches to the enter of each molecule;
-Serve as the boundaries for Sarcomeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are Sarcomeres?

A

Are contractile units of skeletal muscle consisting of components between 2 Z discs ;
-Sarcomeres are joined to together by ACTIN molecules that are located in 2 adjacent sarcomeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is Titin?

A
  • ELASTIC large, protein attaching MYOSIN to Z disc that contributes to elastic recoil of muscle;
  • Begin at the M-Lines and end at the Z discs;
  • Stabilize the position of Myosin (thick) in each sarcomere and elasticity helps muscle return to resting length
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are Cross-Bridges?

A
  • Small projections (heavy meromyosin) from the sides of myosin filaments;
  • Are formed by heads of myosin molecules that extend toward & interact with actin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is produced by the movement of Cross-Bridges?

A
  • *Interactions between cross bridges on myosin heads and actin that yield CONTRACTIONS;
  • Sliding of filaments is produced by actions of cross bridges
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What happens to H-Zones when a sarcomere contracts?

A

H-zones DISAPPEAR;

  • Relaxed muscle = myosin only;
  • Contracted muscle = disappears
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the Sarcoplasma?

A

AKA: Cytoplasm;

  • It is the matrix for the myofibrils in the muscle fibers;
  • Includes a rich supply of mitochondria and an extensive SARCOPLASMIC RETICULUM (endoplasmic reticulum)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the function of the Sarcoplasmic Reticulum?

A

SR has a special organization that is very important in the control of muscle contraction;

  • The special organization of the SR forms the Transverse (T-tubule)-Sarcoplasmic Reticulum System;
  • Also serves as a Ca2+ reservoir in muscle!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the Sliding Filament Theory of Muscle Fiber Contraction?

A

Muscle contraction invokes the sliding of ACTIN and MYOSIN myofilaments past each other to SHORTEN the length of each sarcomere (Z disc to Z disc);
-Results from making/breaking chemical bonds between cross bridges of myosin filaments and G-actin molecules of the actin strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What happens during a muscle contraction?

A
  • *Occurs because thin filaments slide over & between thick filaments towards center =
    1. A bands (containing actin) move closer together, DON’T shorten;
    2. I bands shorten because they define distance between A bands of successive sarcomeres;
    3. H bands (containing myosin) shorten
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is ATPase?

A
  • Alass of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion;
  • Each myosin head contains an ATP-binding site which functions as an ATPase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the role of ATPase in initiating a muscle contraction?

A
  • Myosin CAN’T bind to actin unless it is “cocked” by ATP;
  • After binding, myosin undergoes conformational change (POWER STROKE) which exerts force on actin;
  • After power stroke myosin detaches
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What happens as a result of a Power Stroke?

A

Myosin will be released and the energy from the PO4 bond will be released and pull the Actin thread through the myosin yield a contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the Cross-Bridge Cycle?

A
  1. Resting fiber = cross bridge not attache to actin;
  2. Cross-bridge attaches to actin;
  3. PO4- is released, causing conformation change in myosin;
  4. Power stroke causes filaments to slide — ADP is released;
  5. New ATP binds to myosin head releasing it from actin;
  6. ATP is hydrolyzed and cross-bridge returns to resting state
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What controls Cross-Bridge to Actin attachment?

A
  • Control of cross bridge attachment to actin is via TROPONIN-TROPOMYOSIN SYSTEM;
  • Serves as a switch for muscle contraction & relaxation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is Tropomyosin?

A

The filament tropomyosin lies in grove between double row of G-actins (that make up actin thin filament)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is Troponin?

A

Troponin complex is 3 globular proteins that are attached to tropomyosin at intervals of every 7 actins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is the state of the troponin-tropomyosin system in a RELAXED muscle?

A
  • In relaxed muscle, tropomyosin BLOCKS binding sites on actin so crossbridges can’t occur;
  • This occurs when Ca++ levels are low (<10-6 M);
  • Contraction can occur only when binding sites are exposed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

How does Troponin initiate a contraction?

A

The strong affinity of TROPONIN for calcium ion initiates contraction of each sarcomere by altering the blocking of actin binding sites by the myosin cross-bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What happens to start a contraction?

A
  • When Ca2+ levels rise (>10-6 M), Ca2+ binds to TROPONIN causing conformational change which moves tropomyosin & exposes binding sites;
  • Allowing crossbridges & contraction to occur;
  • Cross-bridge cycles stop when Ca2+ levels decrease (<10-6 M)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What happens as Ca2+ levels decrease?

A
  • Ca2+ levels decrease because it is continually pumped BACK INOT the sarcoplasmic reticulum (SR - a calcium reservoir in muscle);
  • Most Ca2+ in SR is in TERMINAL CISTERN;
  • Running along terminal cisternae are T TUBULES
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is Excitation-Contraction Coupling?

A
  • Skeletal muscle sarcolemma is excitable;
  • Conducts APs just like axons;
  • Release of ACh at NMJ causes large depolarizing end-plate potentials & APs in muscle;
  • APs race over sarcolemma & down into muscle via T tubules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

How do the T-Tubules transit the APs?

A
  • T tubules are extensions of sarcolemma;
  • T-tubules have very high concentration of Ca2+;
  • Ca2+ channels in SR are mechanically linked to channels in T tubules;
  • APs in T tubules cause release of Ca2+ from cisternae via V-gated Ca2+ release channels = ELECTROMECHANICAL RELEASE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What causes the initiation of a muscle contraction?

A

Begins with action potentials from the neuromuscular junction that spread over the muscle fibers;

  • APs generate electrical currents that spread to the interior of the muscle fiber by the T-Tubulue-Sarcoplasmic Reticulum System;
  • Currents then cause the release of Ca2+ from SR to sarcoplasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What happens at the Cross-Bridge during excitation-contraction coupling?

A
  • ATPase binds ATP to TROPONIN;

- A POWER STROKE is produced

45
Q

What is the purpose of ATP?

A

New ATP has to be present for the cross-bridge to DETACH;

-A lack of ATP produces rigor mortis

46
Q

How long do muscle contractions continue?

A
  • Contraction wil continue as long as the Ca2+ remains HIGH in the sarcoplasmic fluid;
  • BUT, a continually active calcium pump in the walls of the SR pumps Ca2+ back into the SR
47
Q

What causes muscles to relax?

A

-When APs cease, muscle relaxes = Because Ca2+ channels close & Ca2+ is pumped back into SR

48
Q

What is a Motor End Plate?

A

Place on sarcolemma where the neuromuscular junction occurs

49
Q

What is a Motor Unit?

A
  • A motor unit includes each motor neuron & all fibers it innervates;
  • Each motor neuron branches to innervate a variable number of muscle fibers;
  • The average number of muscle fibers to a motor unit it 150
50
Q

What happens when a motor unit is activated?

A
  • When a motor neuron is activated, all muscle fibers in its motor unit contract;
  • Number of muscle fibers in motor unit varies according to degree of fine control capability of the muscle
51
Q

What is an Innervation Ratio?

A

Number of motor neuron to muscle fibers

52
Q

What is Fine Control?

A

Fine control occurs when motor units are SMALL

— 1 motor neuron innervates small number of fibers

53
Q

Since individual motor units fire “all-or-none,” how do skeletal muscles perform smooth movements?

A

RECRUITMENT is used:

  1. Brain estimates number of motor units required & stimulates them to contract
  2. It keeps recruiting more units until desired movement is accomplished in smooth fashion
  3. More & larger motor units are activated to produce greater strength
54
Q

What is a Muscle Twitch?

A
  • A single rapid contraction & relaxation of muscle fibers;
  • Accomplished by instantaneously exciting the nerve to a muscle with an electrical stimulus through the muscle itself, giving rise to a single, sudden contraction for a fraction of a second
55
Q

What is Summation?

A
  • Means the adding together of individual muscle twitches to make strong and concert muscle movements;
  • If 2nd stimulus occurs before muscle relaxes from 1st, the 2nd twitch will be greater
  • Types =
    1. Multiple Motor Unit or Spatial Summation;
    2. Wave or Temporal Summation
56
Q

What are Graded Contractions?

A
  • Contractions of carrying strengths;
  • Obtained by stimulation of varying numbers of fibers;
  • Increasing frequency increase strength of subsequent contractions!
57
Q

What is a Multiple Motor Unit or Spatial Summation?

A

Summation due to increasing the number of motor units contracting SIMULTANEOUSLY

58
Q

What is a Wave Summation or Temporal Summation?

A

-Summation due to increasing the frequency of contraction of individual motor units

59
Q

What is Treppe?

A

AKA: Staircase Effect;

  • If muscle is repeatedly stimulated with maximum voltage to produce individual twitches, successive twitches get larger;
  • Caused by accumulation of intracellular Ca2+
60
Q

What is Tetanization?

A

-At even higher frequencies of stimulation (> 35 stimuli per second) the successive contractions fuse together and cannot be distinguished from one another

61
Q

What is Critical Frequency?

A

The lowest frequency at which tetanization occurs

62
Q

What is an Incomplete Tetanus?

A

If muscle is stimulated by an increasing frequency of ELECTRICAL SHOCKS, its tension will increase to a maximum

63
Q

What is a Complete Tetanus?

A

If frequency is so fast NO relaxation occurs, a smooth sustained contraction results

64
Q

What is an ISOTONIC Contraction?

A

= Same strength;

  • Force remains CONSTANT throughout shortening process;
  • The muscle shortens while the tension of the muscle remains constant
65
Q

What are ISOMETRIC Contractions?

A

= Same length of muscle;

  • Exerted force does not cause load to move & length of fibers remains constant;
  • The muscle does NOT shorten during contraction but the tension varies;
  • Isometric contraction in different skeletal muscles can last for different periods of time
66
Q

What are ECCENTRIC Contractions?

A

-Load is greater than exerted force & fibers lengthen

67
Q

What is the Series-Elastic Component of muscles?

A
  • Tendons & connective tissue are elastic & absorb tension as muscle contracts;
  • They recoil as muscle relaxes & spring back to resting length
68
Q

What is the respiration of SLOWER fibers?

A

-Slow fibers are AEROBIC because of many capillaries, more myoglobin, and mitochondria

69
Q

What is the respiration of FAST fibers?

A

Fast fibers are ANAEROBIC

70
Q

How are skeletal muscle fibers be divided?

A

-On the basis of contraction and resistance to fatigue;
— SLOW twitch fibers fatigue slowly = Type 1 Fibers;
— FAST twitch fibers fatigue rapidly = Type IIA and IIX Fibers

71
Q

What causes the differences in twitch speed?

A

Twitch speed due to different myosin ATPases that are slow or fast

72
Q

What determines muscle fiber type?

A
  • Genetic inheritance determines relative percentages of fast twitch to slow twitch fibers in a muscle;
  • This in turn dictates to an extent the sport in which an athlete best performs
73
Q

What are the differences in fast and slow twitch fibers?

A
  1. FAST are about twice the diameter of slow twitch fibers;
  2. Enzymes that promote the rapid release of energy of the phosphagen and glycogen-lactic acid energy systems are 2-3x as active in fast twitch fibers — maximal power than can be achieved by fast twitch fibers as great as 2x that of slow;
  3. SLOW twitch fibers are mainly organized for ENDURANCE — aerobic energy = more mitochondria, myoglobin and aerobic enzymes;
  4. Number of capillaries per mass of fibers is greater in SLOW than fast fibers
74
Q

Fast vs. Slow Fibers

A
  • FAST can deliver extreme amounts of power for a few seconds to a minute or so;
  • SLOW can produce ENDURANCE, delivering prolonged strength or contraction over many minutes to hours
75
Q

What are Type 1 Fibers?

A
  • Also called RED SLOW OXIDATIVE;
  • Adapted to contract SLOWLY without fatiguing;
  • Uses mostly AEROBIC respiration;
  • Rich capillary supply, many mitochondria, & aerobic enzymes;
  • Has lots of myoglobin (O2 storage molecule) = red color;
  • Have small motor neurons with small motor units
76
Q

What are Type IIX Fibers?

A
  • Type IIX fibers also called WHITE FAST GLYCOLYTIC;
  • Adapted to contract fast using anaerobic metabolism;
  • Has large stores of glycogen, few capillaries & mitochondria, little myoglobin
77
Q

What are Type IIA Fibers?

A

-Type II A fibers also called WHITE FAST OXIDATIVE;
-Adapted to contract fast using aerobic metabolism
Intermediate to Type I & Type IIX;
-Have large motor neurons with large motor units

78
Q

What is the respiration of skeletal muscles?

A
  • Skeletal muscles respire anaerobically 1st 45-90 sec of moderate-to-heavy exercise ;
  • Cardiopulmonary system requires this time to increase 02 supply to exercising muscles;
  • If exercise is moderate, aerobic respiration contributes majority of muscle requirements after 1st 2 min
79
Q

What is Maximum oxygen uptake (aerobic capacity)?

A
  • Maximum rate of oxygen consumption (V02 max);

- Determined by age, gender, & size

80
Q

What is the Lactate (anaerobic) threshold?

A
  • Percentage of max 02 uptake at which there is significant rise in blood lactate levels;
  • In healthy individuals this is at 50– 70% V02 max
81
Q

What do muscles use for energy during LIGHT exercise?

A

During light exercise, most energy is derived from AEROBIC respiration of plasma free fatty acids

82
Q

What do muscles use for energy during MODERATE exercise?

A

During moderate exercise, energy derived equally from fatty acids & glucose

83
Q

What do muscles use for energy during HEAVY exercise?

A
  • During heavy exercise, glycogen supplies 2/3 of energy;
  • Liver increases glycogenolysis;
  • GLUT-4 carrier is moved to muscle cell’s plasma membrane
84
Q

What is Oxygen Debt?

A
  • When exercise stops, rate of oxygen uptake does not immediately return to pre-exercise levels;
  • Oxygen debt accumulates during exercise;
  • When oxygen is withdrawn from hemoglobin & myoglobin;
  • & because of 02 needed for metabolism of lactic acid produced by anaerobic respiration
85
Q

What is the Phosphocreatine System?

A
  • During exercise ATP can be used faster than can generated by respiration;
  • Phosphocreatine (creatine phosphate) is source of high energy Ps to regenerate ATP from ADP;
  • Phosphocreatine levels are 3X ATP = refuels ATP pool
86
Q

What is Muscle Fatigue?

A
  • Exercise-induced reduction in ability of muscle to generate force;
  • Sustained muscle contraction fatigue is due to accumulation of extracellular K+ = From K+ efflux during AP
87
Q

When does Muscle Fatigue occur?

A
  • Occurs in moderate exercise as slow-twitch fibers deplete glycogen stores;
  • Fast twitch fibers are then recruited, converting GLUCOSE TO LACTIC ACID which interferes with Ca2+ transport
88
Q

What is Central Fatigue?

A

Central fatigue occurs as BRAIN is less able to activate muscles even when muscle is not fatigued

89
Q

How does the muscle adapt to exercise?

A

-AEROBIC training improves aerobic capacity (by 20%) & lactate threshold (by 30%);
-Weight training increases muscle size by increasing NUMBER of MYOFIBRILS/FIBER
& in some cases fibers can split

90
Q

What are the effects of endurance training on skeletal muscles?

A
  1. Imprpoved ability to obtain ATP;
  2. Increased size/number of mitochondria;
  3. Less lactic acid produced;
  4. Increased myoglobin content;
  5. Increased intramuscular triglyceride;
  6. Increased lipoprotein lipase’s (enzyme needed to use lipids in blood);
  7. Increased proportion of energy derived from fat; less from CHO;
  8. Lower rate of glycogen depletion;
  9. Improved efficiency if extracting O2 from blood;
  10. Decreased number of type IIX (fast glycolytic) fibers; Increased type IIA (fast oxidative fibers)
91
Q

Where are motor neurons of skeletal muscle located?

A
  • Lower Motor Neurons — a neuron cell bodies are in VENTRAL HORN OF spinal cord;
  • Axons leave in VENTRAL ROOT = Lower Common Pathway
92
Q

What influences the activity of the lower motor neurons?

A
  • Activity influenced by sensory feedback from muscles & tendons;
  • & facilitory & inhibitory activity from upper motor neurons
93
Q

Where do the neurons receive sensory feedback form?

A
  • To control skeletal muscle movements, neurons must receive continuous sensory feedback;
  • Info comes from tension from GOLGI TENDON ORGANS;
  • & on length of muscle from MUSCLE SPINDLE APPARATUS
94
Q

What makes up Muscle Spindle Apparatus?

A
  • Intrafusal Fibers;
  • Extrafusal Fibers
  • Spindles are arranged in parallel with extrafusals inserting into tendons at each end of muscle
95
Q

What are Intrafusal Fibers?

A
  • Modified thin muscle cells;

- Have nuclei in central region instead of contractile filaments

96
Q

What are the different arrangements of nuclei in the muscle spindle apparatus?

A
  1. NUCLEAR BAG FIBERS have nuclei arranged in loose aggregate;
  2. NUCLEAR CHAIN FIBERS have nuclei arranged in rows
97
Q

What are Extrafusal Fibers?

A

-Regular muscle fibers

98
Q

What is the Golgi Tendon Organ Reflex?

A
  • Involves 2 synapse in the CNS = DISYNAPTIC REFLEX;

- Sensory axons from Golgi tendon organ synapse on interneurons

99
Q

What is the function of the Golgi Tendon Organ Reflex?

A
  • Sensory axons synapsing on interneurons makes INHIBITORY synapses on motor neurons;
  • Prevents excessive muscle contraction or passive muscle stretching
100
Q

What is the cellular structure of Cardiac Muscle?

A
  • *Myocardium;
    1. Contractile apparatus similar to skeletal;
    2. STRIATED like skeletal;
    3. INVOLUNTARY like smooth;
    4. Forms two functional sancta = ATRIA and VENTRICLES;
    5. Branched muscle fibers are electrically coupled and joined by INTERCALATED DISKS (gap junctions) = Allow APs to spread throughout cardiac muscle
101
Q

What is the cellular structure Smooth Muscle?

A
  • Has NO sarcomeres
  • Has gap junctions;
  • Contains 16X more actin than myosin = Allows greater stretching & contracting;
  • Actin filaments are much longer and anchored to DENSE BODIES
102
Q

What controls Smooth Muscle Contractions?

A
  • Controlled by Ca2+ but different from striated muscle;

- Has little sarcoplasmic reticulum & NO troponin/tropomyosin

103
Q

What initiates a Smooth Muscle Contraction?

A
  1. Ca2+ enters thru channels in plasma membrane;
  2. Binds with CALMODULIN;
  3. Ca2+-calmodulin complex activates MYOSIN LIGHT CHAIN KINASE (MLCK) = Which phosphorylates & activates myosin;
  4. Myosin forms crossbridges with actin
104
Q

What causes Smooth Muscle to Relax?

A
  1. Relaxation occurs when Ca2+ concentration DECREASES;
  2. Myosin is dephosphorylated by MYOSIN PHOSPHATASE;
  3. Myosin can no longer form cross bridges
105
Q

Why are Smooth Muscle Contractions slower than striated muscles?

A
  • Smooth muscle has slower contractions than striated;
  • Can form a state of prolonged binding of myosin to actin (latch state);
  • Maintains force using little energy
106
Q

What is the mechanism for a Smooth Muscle Contraction?

A

1 APs caused depolarization of the plasma membrane;

  1. Voltage-gate Ca2+ channels in the membrane open;
  2. Ca2+ enter the membrane and binds with CALMODULIN to create the Ca2+-Calmodulin complex;
  3. Activates MLCK;
  4. MLCK activates Myosin Light Chain by phosphorylation;
  5. Cross-bridge forms and contraction occurs;
  6. Dephosphorylation of myosin by MYOSIN PHOSPHATASE breaks the cross-bridge;
  7. Muscle relaxes
107
Q

What is a Single Unit Smooth Muscle?

A
  • Single unit is SPONTANEOUSLY active = MYOGENIC;
  • Some cells are pacemakers;
  • Has gap junctions to spread electrical activity
108
Q

What is a Multiunit Smooth Muscle?

A
  • Multiunit requires NERVE STIMULATION by ANS;

- Neurotransmitters are released along a series of synapses called VARICOSITIES

109
Q

What are Synapses en Passant?

A

Synapses in passing;

-The release of neurotransmitter along a series of varicosities in a multiunit smooth muscle

Spring 2014 (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions