Muscle-Mace (exam 2) Flashcards
1
Q
Striations=
A
Alternating light and dark bands
2
Q
What muscle tissue is associated with striations?
A
skeletal muscle tissue (and cardiac muscle tissue)
3
Q
Skeletal muscle tissue is mostly ______ muscle tissue, consciously controlled
A
voluntary
4
Q
Describe skeletal muscle tissue:
- fibers? how are they arranged?
- Nuclei?
A
Long, unbranched, cylindrical cells (skeletal muscle fibers), arranged in parallel bundles that run length of the entire muscle
- Multinucleated (many nuclei adjacent to cell membrane)
5
Q
Where is skeletal muscle located?
A
locations:
attach to bone, skin, surrounds distal end of digestive and urinary tracts as sphincters
6
Q
Skeletal muscle contraction moves:
A
bones, causes facial expression, controls defecation or urination
7
Q
Describe cardiac muscle tissue:
- ___ _____ cardiac muscle cells
- # of nuclei?
- mitochondria?
- striations?
- branched or unbranched?
A
- Short, branched cardiac muscle cells
- 1 or 2 centrally located nuclei, mitochondria-rich
- Striated, branched
- Cells closely packed in one direction
8
Q
Describe the function of intercalculated discs and which muscle type they are located in
A
- located in cardiac muscle tissue
- Intercalated Discs= junction between cells (strengthens attachments between cells and promotes rapid conduction of electrical activity through cardiac cells)
9
Q
Locations of cardiac muscle tissue
A
heart
10
Q
T/F: cardiac muscle tissue is involuntarily controlled
A
True.
**Syncytium!
11
Q
Describe Smooth Muscle tissue:
- ____-shaped cells
- branched or unbranched?
- nuclei? location?
A
Spindle-shaped cells - short, closely packed in one direction, unbranched, single nuclei, centrally located
12
Q
Does smooth muscle tissue have striations?
A
NO! *Lacks striations, appears smooth
13
Q
Locations of Smooth muscle tissue
A
Walls of digestive, respiratory, & urinary tracts; ***skin (erector pili), surrounds the blood vessels, digestive tract, urinary tract, reproductive tract, respiratory tract as sphincters
14
Q
Is smooth muscle voluntarily or involuntarily controlled?
A
Involuntarily controlled
15
Q
List the functions of smooth muscle tissue (list 5)
A
- Moves substances along internal passages (peristalsis)
- Erects hairs
- Controls blood flow and blood pressure
- Regulates airflow in lungs
- Controls urination and defecation
16
Q
Functions of Skeletal Muscle (5)
A
- Body movement: Muscular contraction moving bone
- Maintenance of posture: Stabilizes joints and helps maintain the body’s posture
- Protection and support: Muscles along the walls of abdominal and pelvic cavity protect the internal organs and support normal position
- Storage and movement of materials:
- -Contract and relax sphincters to regulate passage of material.
- Allow voluntary expulsion of feces and urine
- Heat production: Heat is released as a byproduct of muscle contraction
- –**Main source of the heat produced in the body
17
Q
Describe the gross anatomy of skeletal muscles:
- each muscle is composed of?
- muscle cells are organized into____
- each muscle contains?
A
- Each muscle is composed of thousands of muscle cells
- Muscle cells are organized into bundles, termed fascicles
- Each muscle contains connective tissue, blood vessels, nerves
18
Q
Gross anatomy of skeletal muscle:
- name the 3 ______ layers of CT
- what is their function? (list 3 functions: hint “PSM”)
A
-3 concentric layers of connective tissue: epimysium(superficial), perimysium, endomysium(inner)
- Function:
- -Protection
- -Sites for blood vessel and nerve distribution
- -means of attachment to skeleton or other structures
19
Q
Describe the epimysium
A
layer of dense irregular CT, surrounds whole skeletal muscle
20
Q
Describe the Perimysium
A
dense irregular CT surrounding the fascicles, contains extensive blood vessels and nerves supplying fibers
21
Q
Describe the endomysium
A
areolar CT, surrounds and electrically insulates each muscle fiber
“think E in endomysium for Electrical”
22
Q
Describe a Tendon:
- structure?
- formed by?
- attaches ____ to bone
A
- cordlike structure composed of dense regular CT
- formed by the three CT layers
- attaches **muscle to bone, skin or another muscle
23
Q
Describe aponeurosis:
- describe it
- it’s formed from the ___ CT layers
- Holds muscles together for ____?
A
- thin, flattened sheet of tendon with wide area of attachment
- formed from the three connective tissue layers
- Holds muscles together for functional enhancement
24
Q
Describe Deep Fascia
A
- additional sheet of dense irregular CT
- external to the epimysium
- separates individual muscles
- binds together muscles with similar functions
- contains nerves, blood vessels, and lymph vessels
- fills spaces between muscles
25
Muscle hypertrophy= a greater # of _______
contractile elements**
26
There are less _____ _____ in muscle atrophy
contractile elements
27
T/F: muscle hypertrophy= muscle hyperplasia
FALSE. Muscle hypertrophy IS NOT muscle hyperplasia
28
Describe Fascia of Skeletal muscles:
- what kind of CT?
- Separates neighboring _____
- separates muscles from the ______
- Intermuscular septum=
=dense irregular CT
3 main things:
- Separates neighboring muscles (organs) or muscle groups from each other
- Separates muscles from hypodermis
- Intermuscular septum - fascia separating muscles
29
Endomysium, peri-, and epimysium continue into _____
tendons
30
When muscle cells contract, they pull on these CT wrappings (endo-,peri-, and epimysium), which in turn pull on the tendon, and therefore move the _____
bones they attach to
31
If the muscle gets a pump– vasodilation is occurring within the muscle itself– and then it stops contracting– you lose ____
the pump
32
When muscles contract– it pulls on endomysyium which pulls on perimysium which pulls on epimysium and that pulls on ______
tendons
33
Describe multinucleated muscle cells:
-in which muscle type?
and contains _____ proteins
(in skeletal muscles)
| -dominant cells in the muscle, contain contractile proteins
34
Describe Satellite cells
(in skeletal muscles)
**No contractile proteins, may be stimulated to differentiate for repairing the injured muscle multinucleated muscle cells
35
Describe the sarcolemma
=muscle cell membrane
36
Describe T-tubules
aka transverse tubules
| =Deep invaginations of sarcolemma, for transmitting nerve impulses from sarcolemma inward
37
Describe the Sarcoplasmic reticulum:
- a ______ network around ______ proteins
- modified _____ endoplasmic reticulum
- stores ______ ?
- what structure is at the end of the SR?
-a tubular network around contractile proteins
-modified smooth endoplasmic reticulum
-stores calcium which is released into sarcoplasm during muscle contraction
-**Terminal cisternae
(SR= network around contractile proteins that releases Ca 2+ into the Terminal cisternae)
38
What is a terminal cisternae?
- serve as reservoirs for ______ ions
- they can combine with _____ to form triads
- dilated ends of sarcoplasmic reticulum, serve as reservoirs for calcium ions, combine with T-tubule to form triads (middle of triad= t tubule, and on each side you have a terminal cisternae)= triad!!! KNOW
39
Go over slide 13
slide 13
40
Describe the microscopic anatomy of skeletal muscles
- multinucleated cells
- satellite cells
- sarcolemma
- T-tubules
- Sarcoplasmic Reticulum (contains Terminal cisternae)
- myoglobin
- Myofibrils
- thick filaments
- thin filaments
- sarcomere (Z discs, I bands, A bands)
- H zone
- M line
41
Myoglobin=
- _____ protein located in the?
- allows the muscle cells to store ____
=Reddish golobular protein in sarcoplasm (the cytoplasm of muscle cells)
-allows the muscle cells to store oxygen
-gives the muscle the red color, the redder the muscle , the more myoglobin it contains
(skel muscle has lots of myoglobin)
42
Myofibrils=
- located in the _______
- the _____ proteins
- account for ___% of cell volume
- each myofibril is composed of a ______
- Located in sarcoplasm (the cytoplasm of muscle cells)
- The contractile proteins (the special organelles that allow the muscle to contract)
- account for 80% of cell volume
- Each myofibril is composed of a bundle of thin and thick myofilaments, interactions b/w the thin & thick filaments of are responsible for muscle contraction
43
Thick filaments=
- are assembled from?
- describe each myosin protein
- each strand with a globular head and ________ tail
- Assembled from bundles of protein molecules, myosin
- each myosin protein with two intertwined strands
- each strand with a globular head and elongated tail
44
Thick filaments:
- tails point toward?
- heads point toward?
- Myosin head contains ___
- tails pointing toward center of thick filaments
- heads pointing toward edges of thick filaments
***head with a binding site for actin (thin filaments)
45
actin= _____ filament
- myosin head contains the actin ____ _____
- thick filament= entirely ______
- thin filament=
Actin= thin filament
-Myosin head with actin binding site
Thick filament= entirely myosin
Thin filament= different types of actin and tropomyosin and troponin
46
Thin filaments are composed of (3 things?)
actin, tropomyosin, troponin
47
Describe Thin filaments
- Primarily composed of two strands of protein, actin, twisted around each other
- Each strand of actin is composed of many small spherical molecules called G-actin (globular actin)
- Each G-actin has a myosin binding site where myosin head attaches during contraction
48
Tropomyosin=
twisted “stringlike” protein, **covers myosin binding sites in a noncontracting muscle
49
Troponin=
- globular protein attached to tropomyosin
| - binding site for Ca2+
50
Sarcomere= repeating functional units of _______. That contains ___ and ____ bands
myofilaments
- contains I bands
- and A band
51
Sarcomere:
| -the repeating functional units of myofilaments are separated by: _______. Which are used as _____ for thin filaments
separated from one another by Z discs (specialized proteins perpendicular to myofilaments, anchors for thin filaments)
52
Describe I bands
-region containing only thin filaments
-appear *light under a microscope
-disappear at maximal muscle contraction
(in sarcomere)
53
Describe A band:
- located in the ______
- contains the entire ____ filament
- contains partially overlapping ____ filaments
- appears ____ under the microscope
(in sarcomere)
- *contains entire thick filament,
- contains partially overlapping thin filaments
- *appears dark under a microscope
54
The H zone of skel muscles:
=the ______ portion of the __ Band
-____ filaments ONLY
-disappears during _____ muscle contraction
=central portion of A band
thick filaments only; no thin filament overlap
-disappears during maximal muscle contraction
55
Describe the M line (in skeletal muscles):
- protein ________ structure at the center of the H zone
- attachment site for ______ filaments
- protein meshwork structure at center of H zone
| - attachment site for thick filaments
56
____= is everything between 2 Z discs
sarcomere
57
Thin filaments are acted on by the ____
myosin heads and pulled toward the center toward the m line, and this pulls z discs together= muscle contraction
A band= dark
I band= z discs and thin filaments (appears lighter)
58
In relaxed muscle, overlap is _____
minimal
59
As you begin to contract muscle, the distance b/w myosin filaments and _____ is smaller
z line
60
Contracted muscle will have ALL _____ muscle banding
dark (cuz there is no open actin binding)
61
Neuromuscular Junctions:
- location?
- each muscle cell has __ neuromuscular junction
- includes?
Location: where somatomotor neuron innervates muscle
- Each muscle cell has 1 neuromuscular junction
- Includes: synaptic knob, motor end plate, synaptic cleft
62
Describe the synaptic knob:
- synaptic knob= the expanded tip of the _____
- houses _____
- has ___ pumps in the plasma membrane which establish a _______
- has _____ ______ channels, and the opening of these channels is triggered by _____
=the expanded tip of the axon
- Houses synaptic vesicles (small membrane sacs filled with neurotransmitter, acetylcholine (ACh))
- Has Ca2+ pumps in plasma membrane, establish calcium gradient, with more outside the neuron
- Has voltage-gated Ca2+ channels, opening of these channels is triggered by nerve signals
63
Motor end plate= a specialized region of the _______ covered by synaptic knob
-has ___ receptors
sarcolemma covered by synaptic knob
| -Has ACh receptors
64
Review slide 23
review
65
Synaptic Cleft=
=Narrow fluid-filled space
- Separates synaptic knob and motor end plate
- Contains Acetylcholinesterase,
66
Acetylcholinesterase=
enzyme that breaks down ACh molecules after their release into synaptic cleft
**(if you want to stop muscles from contractin-> you might increase the activity or abundance of acetylcholinesterase )
67
Skeletal Muscle Contraction: 1st Event: Excitation of a Skeletal Muscle Fiber (list 3 steps)
(at the neuromuscular junction: excitation of a skel muscle fiber)
1. Ca2+ entry at synaptic knob:
- -Nerve signal propagated down motor axon, triggers opening of voltage-gated Ca2+ channels
- -Movement of Ca2+ down concentration gradient from interstitial fluid into synaptic knob
- -Binding of Ca2+ with synaptic vesicles
2. Release of ACh from synaptic knob:
- -Merging of synaptic vesicles with synaptic knob membrane triggered by binding of Ca2+
- -Exocytosis of ACh into synaptic cleft
3. Binding of ACh at motor end plate:
- -ACh binds with ACh receptors within motor end plate
- -Causes excitation of muscle fiber
68
Skeletal Muscle Contraction2nd Event: Excitation-Contraction Coupling (3 steps)
1. Development of an end-plate potential at the motor end plate:
- -Binding of ACh to ACh receptors on motor end plate results in the generation of end plate potential (EPP)
2. EEP triggers action potential which propagates along sarcolemma and T-tubules
3. Release of calcium from the sarcoplasmic reticulum
- -Opening of Ca2+ channels in terminal cisternae, triggered by action potential
- -Diffusion of Ca2+ into sarcoplasm
(End plate potential (EEP) as the result of Ach release once these end plate potentials reach -55 mV this will trigger an action potential= threshold voltage(the voltage sufficient thats needed to trigger an action potential)
- action potential is all or nothing- which propagates down the sarcolemma to the t tubules and depolarize the membrane on the inside of the t tubules
- this opens up Ca 2+ channels in ternminal cisternae
- This voltage mediated change in confirmation between the t tubule membrane and terminal cist is going to open ca channels and the SR is the storage facility for HUGE amounts of Ca 2+
- so Ca 2+ channels ALL open at once which causes an explosion of Ca into the SR and then it diffuses down into the
69
Events in Skeletal Muscle: Contraction3rd Event: Binding of Ca2+ and Cross-bridge Cycling (2 things)
1. Calcium binding
| 2. Crossbridge cycling
70
Describe calcium binding in the 3rd event of Skel. muscle contraction
(Sarcomere: crossbridge cycling)
- Binding of Ca2+ to troponin, induces conformation change in troponin
- Troponin-tropomyosin complex moved, myosin binding sites of actin exposed
71
Describe crossbridge cycling in the 3rd event of skel muscle contraction (4 things)**
(Sarcomere: crossbridge cycling)
-Crossbridge formation ("attach"): myosin heads in the ready position attach to exposed myosin binding sites on actin, this forms a crossbridge
- Power stroke ("pull"): swiveling of the myosin head (power stroke) pulls thin filaments past thick filaments, ADP and Pi released
- Release of myosin head ("release"): binding of ATP to binding site of myosin head, causes release of myosin head from actin
- Reset myosin head ("reset"): ATP split into ADP and Pi by ATPase (enzyme on myosin head), providing energy to “cock” the myosin head
72
How long does muscle contract for? (ie what is it dependent on?)
Continues as long as Ca2+ present, keeping myosin binding sites exposed, results in sarcomere shortening into a contracted state, disappearance of H zone, narrowing or disappearance of I band, Z discs move closer together
73
Describe Relaxed skeletal muscle
myosin heads on the thick filament will bind on the actin sites and pull thin filaments to the m line
- as contraction occurs, the I band disappears. Since the. Fully contracted muscle DOES not have striations. Relaxed muscle does
- natural elasticity of the muscle fiber is mediated by connectin the I band of the sarcomeres– this acts as a spring to return the thick filament back to the stretched position
Contracted muscle: sarcomere shortens and the thin filaments overlap
74
Events in Skeletal Muscle Relaxation (list 7)
- Hydrolysis of ACh at receptor (acetylcholinesterase), closure of ACh receptor channel
- No further action potential generated
- Closure of Ca2+ channels in SR
- Released Ca2+ continuously returned by Ca2+ pumps back into SR
- Return of troponin to its original shape
- Tropomyosin now moving over myosin binding sites on actin, preventing cross-bridge formation
- Returns to original relaxed position through natural elasticity of muscle fiber
(hide no closure, RR TR)
75
Dantrolene=
(notable drug)
- Interferes with SR Ca2+ release
- helps treat Spasticity in cerebral palsy, stroke, multiple sclerosis
76
Succinylcholine (Anectine)
| =
- Neuromuscular blocking drug (NMBD)
- Binds acetylcholine receptor at motor endplate, insensitive to AchE (actylcholinesterase)
- Maintained depolarization of the motor endplate= sustained flaccid skeletal muscle paralysis
-this drug is great for endotracheal intubation, surgery, or mechanical ventilation (note: no pain control)
77
Drugs used for Mysasthenia gravis and LES:
MG= results in weakness and rapid fatigue. This is a dysfunction that occurs at the NM junction. It either blocks alters or destroys the Ach receptors. SO this stops the ability to create an AP
-1 drug for Mysasthenia gravis is pyrostigmine (this drug is an acetylcholinesterase inhibitor) this will increase ACH in the cleft and allow for stimulation
-LES= lambardt eaton syndrome= an autoimmune dz- you have antibodies against voltage gated ca channels on the knob. This happens to ppl over 40 yo, you can treat with drugs similar to MG, like pyridostigmine!! KNOW
78
List ways to supply Adenosine Triphosphate (ATP):
Grouped by substrate:
-Immediate (phosphagen system, 5-6s): anaerobic,
utilizes available ATP, myokinase, and creatine phosphate
- Short term (anaerobic cellular respiration)
- Long term (aerobic cellular respiration)
79
Describe the 3 methods of immediate ways to supply ATP:
Phosphagen system is anaerobic– it utilizes available ATP and certain enzymes
- 1st way: uses ATPase to break down ATP into ADP and Pi
- @nd way: use myokinase and take 2 ADP--> transfer the inorganic phosphate to create ATP and AMP (adenosine monophosphate)
-3rd way: ADP and CP (creatine phosphate (uses the inorganic phosphate from it))--> converts it to Creatine and ATP (via the enzyme creatine kinase)
80
Describe Short term (method of supplying ATP in skel. muscle metabolism)
=glycolysis - anaerobic cellular respiration, ~50-60 seconds long
-Glycolysis uses glucose as the substrate
-Glucose is stored in the muscle fiber or delivered by the blood
-Breakdown of 1 glucose molecule results in the production of
2 ATP + 2 pyruvate + NADH
-Efforts lasting 50-60s use both phosphagen system and glycolysis
-**Oxygen Debt
81
Describe the Long term (method of supplying ATP in skel. muscle metabolism)
Long Term (oxidative phosphorylation - aerobic cellular respiration, >5-6min):
- Uses pyruvate produced in glycolysis
- Occurs in mitochondria
- **Requires oxygen
- **Produces 34 ATP per glucose
**produces the MOST ATP
82
Skeletal Muscle Fiber Types: List the 2 classification methods
- type of contraction
| - Energy source
83
Describe the characteristics of "Type of contraction"
- Power – primarily based on muscle fiber diameter
- Speed – slow- or fast-twitch muscle fibers
- Duration of Contraction – conduction/EC-coupling speed
84
Describe the energy source (in different skel muscle fibers)
-Oxidative fibers?
vs
-Glycolytic fibers?
-glycolysis (no O2) or oxidative phosphorylation (uses O2)
- Oxidative fibers – use aerobic metabolism, high endurance
- -Extensive capillaries
- -High number of mitochondria
- -High concentration of myoglobin (oxygen source)
- Glycolytic fibers – use **AN-aerobic, easily fatigued
- -Large glycogen reserves
85
Review Slide 37!!
skel muscle fiber types
86
Slow oxidative fibers (type 1)=
slow ATP use, high/Aerobic capacity to make ATP, extensive concentration of capillaries, Red fiber color, SMALLEST fiber diameter. slow contraction velocity, HIGHEST resistance to fatigue. High # of mitochondria, LARGE amount of myoglobin.
- Endurance muscles (maintaining posture, marathon runner)
- Location: trunk and calf muscles
87
Fast oxidative (FO): type 2a fibers=
- ATP use: fast
- capacity to make ATP: moderate, aerobic
- conc. of capillaries: moderately extensive
- fiber color: light red
- contraction velocity: fast
- resistance to fatigue: high
- Fiber diameter: intermediate
- # of mitochondria: many
- myoglobin: medium amount
- primary fiber function: Medium duration, moderate movement (ie walking, biking)
- muscles with large abundance: leg muscles
(This one has the advantage of being aerobic and being really quick (fast contraction). Medium resistance to fatigue (intermediate). Leg muscles (think biking, walking)
88
Fast Glycolytic (FG) Fibers (Type 2b fibers)
- ATP use: fast
- capacity to make ATP: limited, ANaerobic
- conc. of capillaries: sparse
- fiber color: white
- contraction velocity: fast
- resistance to fatigue: LOW
- Fiber diameter: LARGEST
- # of mitochondria: few
- myoglobin: small amount
- primary fiber function: short duration, intense movement (ie sprinting, lifting weights)
- muscles with large abundance: UPPER LIMB muscles
89
List 2 types of skeletal muscle contraction
- isometric
| - isontonic (2 types- concentric and eccentric)
90
Isometric (skel. muscle contraction)=
muscle tension is insufficient to overcome the load, no movement at the joint. Muscle contracts and shortens while tension increases but the angle of the joint does not change
91
Isotonic (skel muscle contraction) =
muscle tension is greater than the load, movement of the joint occurs. Tension remains constant; muscle length and joint angle change
--concentric contraction= Isotonic contraction with muscle length decreasing
--Eccentric contraction= Isotonic contraction with muscle length increasing
92
Skeletal muscle contraction: Length-tension relationship
Horizontal axis= sarcomere length
Vertical axis= muscle tension %
(review slide 40!!)
Ex: arm is extended at the elbow (= at your max length for biceps brachii or brachialis muscle) and in this circumstance the sarcomere is as long as it can be. Just the beginnings of myosin heads overlapping to be able to interact with actin in the thin filament. As you begin contraction you have greater overlap of thin and thick filaments allowing you to produce more tension
-with optimal overlap= you have the greatest possible tension
-takeaway: goes from very lil overlap with thick and thin filaments going to z discs being so close together that
93
Muscle twitch=
single, brief contraction in response to a single stimulation of sufficient intensity (voltage)
94
Threshold=
minimum voltage necessary to activate a muscle (stimulate a contraction)
(=threshold= minimum voltage needed to create a muscle twitch)
95
Latent period=
after stimulus is applied, before contraction begins (EPP, CICR (calcium induced calcium release), ECC)
96
**Muscle tension is dependent on___ (2 things)
stimulus intensity and frequency of stimulation
97
Intensity=
=voltage
- motor unit sensitivity varies
- -Only the most sensitive are activated at threshold.
- All-or-Nothing
- Force
98
Low percentage of the total number of units activated=
LOW tension
99
All-or-nothing=
– Individual muscle fibers contract (activate)
| or they do not (based on stimuli)
100
Force (of contraction) is determined by the ____
number of muscle fibers activated
101
Force produced by the whole muscle is determined by the number of muscle fibers activated. As you increase the stimulus (voltage)-->you increase the # of activated motor units--> And increase the _____
**tension (until MAX tension is achieved )
1. Increased stimulus intensity (voltage)
2. Increased # of activated motor units
3. Increased tension (until max is achieved)
102
Measuring Skeletal Muscle Contraction (slide 43)
After 2 mv is reached, you have a latent period, and this causes a small # of motor units that were responsive to the stimuli will produce the tension. As you increase the intensity, you get more motor units with different thresholds being activated and so on until you have a high enough voltage that all the muscle fibers have been activated
-once you get to 6 mV you are at your limit (and max contractions)-past 8 mV you CANT engage more!!!
Muscle tension= y axis
Voltage increments= X axis
103
Frequency-- given sufficient time for relaxation, developed muscle tension will remain_____ for a given stimulus intensity
```
the same
(as long as you have less than 10 stimuli per second, you should be able to go all the way up to maximum amount of voltage and back down to relaxation (baseline) and back up to the same muscle tension and force produced over and over as long as intensity or voltage stays the same)
```
104
Treppe=
(The muscle tension increases in a graded manner that to some looks like a set of stairs. This tension increase is called treppe, a condition where muscle contractions become more efficient. It's also known as the “staircase effect”)
- **frequency= 10-20 stimuli per second)
1. Insufficient time for Ca2+ removal by Ca2+ pumps
2. More crossbridges form w/ additional stimulation
3. Increased muscle heat = increased efficiency of molecular interactions
(If you increase frequency to 10-20 per second and SAME stimulus intensity), you increase the muscle tension and this causes increased muscle heat= increased efficiency of molecular nteractions. You will be able to produce greater tension in the muscle= (as compared to less than 10 stimuli per second) this is called Treppe
)
105
Wave/Temporal Summation (4 things)
Frequency= 20-50 stimuli per second
1. Insufficient time for Ca2+ removal
2. More crossbridges form w/ additional stimulation
3. Incr. muscle heat = incr. efficiency of molecular interactions
4. Time is NOT sufficient for complete relaxation
(20-50 stimuli per second--> decreases the amount of relaxation and increase muscle heat
- this causes a wave summation (temporal summation) 2nd stimulation arrives before you have complete relaxation SO you have greater maximum force of muscle contraction as you have this summation
- at the point where you stimulate the muscle so much that there is not relaxation= tetany (this is frequency mediated) tetany you still have cross bridges cycling and enough Atp to pump things back and you still have CA 2+ and release of the myosin head from actin
106
Note that tetany and ___ do not have the same mechanism
rigor
Rigor= driven by lack of ATP, ie production cant keep up with demand or rigor mortis (no ATP pumping Ca 2+ back into the SR, muscles cant relax since myosin cant disengage from actin so you have continuous contraction
107
Cardiac muscle:
| -similarities to skeletal muscle?
-Striated, t-tubules, CICR (calcium induced calcium release)
108
Cardiac muscle:
| -list dissimilarities to skeletal muscle
- Less extensive SR network with **no terminal cisternae
- Almost entirely aerobic (~25% of vol = mitochondria)
- Optimal thick/thin filament overlap - during stretch
- Intercalated discs
109
Describe the Fx of intercalculated discs (4)
(connect the cardiac muscle cells)
-Increased stability
- Incr. communication/conduction btwn cardiomyocytes
- Desmosomes – at intercalated discs to anchor cardiomyocytes together (prevents heart from tearing)
- Gap junctions – low resistance conduction btwn cardiomyocytes (create a functional syncytium)
110
Smooth muscle: locations?
- Cardiovascular (blood vessels)
- Respiratory
- Digestive
- Urinary
- Reproductive
- Specialized: iris of eye, erector pili
111
Smooth muscle: structure?
- Smaller than skeletal (diameter is 10x smaller, length: is 1000x smaller than skel muscle)
- **Endomysium only (made of areolar CT)
- Tapered ends
- *No T-tubules, limited SR
- Ca2+ transport at SL(sarcollema) (can be sarcolemma voltage gated, cehm gated or modality gated channels)
- -V-gated
- -Chem-gated
- -Modality-gated (thermal, stretch, hyperglycemia, etc.)
112
Smooth muscle:
| -contains which kind of proteins?
-**Anchoring proteins – cytoskeleton, dense bodies, dense plaques
Cytoskeleton – network of filaments (intermediate filaments)
Dense bodies= bind the intermediate filaments into an array in the sarcoplasm
Dense plaques= bind the intermediate filaments to the SL (located on the surface of smooth muscle)
113
Smooth muscle: contractile mechanism
- which proteins are used?
- arrangement?
- Contractile proteins – arranged between dense bodies along cytoskeleton (NO sarcomeres, No Z-discs)
- Spiral arrangement/longitudinal arrangement – facilitates contraction in multiple directions (twisting)
114
Describe the entire contractile mechanism of smooth muscle
- Thick filaments have myosin heads along entire axis
- Thick filaments have a “latch” mechanism that allows the muscle to stay shortened without using additional ATP
- Thin filaments – actin and tropomyosin, but no troponin (so no Ca2+ binding site)
- Myosin head itself is phosphorylated which brings it into binding conformation with actin
- Phosphorylation of the myosin head is completed with Calmodulin and myosin light chain kinase (MLCK)
- Relaxation occurs via breakdown of MLCK by myosin light chain phosphorylase
(note: There is NO calcium binding site in smooth muscle. Instead we phosphorylate the myosin head. actin is always available but the myosin head must be phosphorylated in order for it to bind to actin. This is done by calmodulin and myosin light chain kinase (MLCK)
115
Describe the steps of smooth muscle contraction (5 steps)
1. opening of voltage-gated Ca 2+ channels-->Stimuli (ie action potential, stretch of the muscle) triggers opening of voltage-gated Ca 2+ channels. Ca 2+ enters the sarcoplasm, primarily from interstitial fluid.
2. Binding of Ca 2+ to calmodulin--> Ca 2+ binds to calmodulin to form a Ca 2+-calmodulin complex
3. Activation of myosin light-chain Kinase (MLCK)--> Ca 2+-calmodulin complex activates MLCK (a phosphorylating enzyme)
4. Activation of myosin head--> Activated MLCK phosphorylates (adds phosphate to) myosin head, activating myosin--- a relatively slow process.
5. Crossbridge formation, power stroke, reattachment--> Activated myosin heads bind to thin filaments to form crossbridges. Mysosin ATPase hydrolyzes ATP, providing the energy for a power stroke. This process is repeated, the force generated is transferred to the anchoring filaments, and the Smooth muscle cell shortens.
