Cells to systems > Lecture 19 > Flashcards

Lecture 19 Flashcards

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1
Q

What is summation of twitches

A
  • Process by which individual twitches combine
  • Produces sustained contractions
  • Can lead to tetanic contractions
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2
Q

What does Recruitment of Motor Units mean

A
  • increase in the number of motor units activated
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3
Q

What can recruitment do

A

• Whole muscle composed of many motor units
• More precise movements are produced with fewer muscle
fibers within a motor unit
• As intensity of stimulation increases, recruitment of motor units
continues until all motor units are activated

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4
Q

What muscles are recruited first followed by which

A
  1. Motor unit one :slow-oxidative fibers
  2. Motor unit 2 : fast-oxidative fiber
    3: Motor unit three : fast-glycolytic fibers
  • Smaller motor units (smaller diameter axons) - recruited first
  • Larger motor units (larger diameter axons) - recruited later
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5
Q

What is muscle tone

A

continuous state of partial contraction

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6
Q

What is going on during • Slow-twitch fibers (Type I)

A
  • Always oxidative
  • Resistant to fatigue
  • Red fibers
  • Most myoglobin
  • Good blood supply
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7
Q

What is Fast-twitch fatigue-resistant

fibers (Type IIa)

A 
• Intermediate fibers
• Oxidative
• Intermediate amount of
myoglobin
• Pink to red in color
• Resistant to fatigue
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8
Q

What is • Fast-twitch glycolytic fibers (Type IIb)

A
  • White fibers (less myoglobin)
  • Poorer blood supply
  • Susceptible to fatigue
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9
Q

What is the difference between the cardiace muscle and skeletal muscle for how it works

A

• Differences in cardiac muscles

  • Not initiated by neuronal input
  • All cells are electrically coupled
  • Long action potential
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10
Q

What is the general structure of cardiac muscle

A 
• Uni-nucleate cell
• Z lines, M lines, A
bands, I bands
• Relatively short
• Branching and
interdigitate
• Arranged in series and
parallel
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11
Q

Where are the location of intercalated disk in cardiac muscles

A 
• 2 regions
• Transverse portion,
aligned with Z line,
desmosomes,
mechanical cohesion
• Lateral portion, parallel
to myofilaments, rich in
gap junctions, low
resistance pathway
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12
Q

What are the three types of heart muscle cells

A
  1. Cells of myocardium
  2. Rhythmically active self
    excitatory “pacemaker”
    cells
  3. Purkinje fibres,
    specialised conducting
    pathways which
    enhance spread of
    localised excitation
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13
Q

How does cardiac receive signal

A 
• AP spreads along
plasma membrane and
invades T tubules
• This opens voltage
sensitive Ca++ channels
in T-tubule membrane
• Diffusion of extracellular calcium
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14
Q

How Excitation contraction coupling work in cardiac muscle

A
  1. Excitation/depolarization
  2. opening of voltage-sensitive plasma membrane C2+ channels
  3. Flow of Ca2+ into cell
  4. Stimulation of Ca2+, release from sarcoplasmic reticulum
  5. increase cytosolic Ca2+ concentration
  6. contraction
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15
Q

What does the extracellular Ca2+ do

A

Extracellular Ca++
stimulates release of Ca++
from SR

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16
Q

What is the contraction of the cardiac muscle called

A

systole

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17
Q

What does the strength of contraction depend on

A

dependent on presence
and concentration of
extracellular Ca++

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18
Q

What is the contractility influence by

A 
• Ca++ levels
• Hormones (epinephrine)
• Nervous (autonomic)
• Extent of stretch
• Cardiac muscle operates in a range of lengths shorter
than optimal
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19
Q

What is contraction of smooth muscle mediated by

A

Contraction mediated by actin and myosin

cross-bridge cycling

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20
Q

Is smooth muscle sarcomere obvious

A

Undefined sarcomere struct

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21
Q

What are the smooth muscle bound together by

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A

basement

membrane and transmits force

22
Q

Do smoother muscle have T-tubules

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A

no, • Small membrane invaginations called caveoli

• SR if rudimentary

23
Q

what is the dense body attached to

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A

actin filament and membrane

24
Q

What are the dense bodies linked by

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A

Linked by diagonal
network of
intermediate filaments
(desmin)

25
Is there troponin present in smooth muscle
no
26
Is there myosin heads in smooth muscle
yes
27
are smooth muscle connected together
no, they are individual cells
28
What are in between Multi-unit smooth muscles
autonomic neuron varicosity
29
Is smooth muscle responsive to stretch
no
30
Is smooth muscle responsive to hormones
Minimal response to | hormones
31
What are the connect the smooth muscle in single-unit smooth muscle
linked electricall by gap junction
32
where are the autonomic neuron varicosity in single-unit smooth muscle
on the outside
33
What is a single-unit smooth muscle
``` • Network of closely opposed cells acting as a single unit • Direct stimulation of only a few ```
34
What is desmosomes
a structure by which two adjacent cells are attached, formed from protein plaques in the cell membranes linked by filaments.
35
How many adherence | points (desmosomes) are there in single-unit smooth muscle
multiple
36
What does Single-Unit Smooth Muscle respond to
``` • Neural signals • Hormones • Mechanical stretch • Local “pacemaker” potentials ```
37
Where are Single-Unit Smooth Muscle used
• Muscles of uterus, intestinal tract, bile duct, small blood vessels
38
What are 3 types of innervation
• Extrinsic: both sympathetic and parasympathetic • Intrinsic: short neurons forming plexuses (networks) with tissue • Afferent sensory: autonomic reflexes
39
What are the branching of fibres from in smooth muscle fibre
postganglionic sympathetic neuron
40
What does the fibres of postganglionic sympathetic neuron have
Branching of fibres with “varicosities” that contains vesicles with neurotransmitter (both acetylcholine and norepinephrine)
41
How are the innvervation of muscle cells placed
• Modulatory rather than | inducing
42
What inputs does the postganglionic sympathetic neuron give
Potential for both sympathetic | and parasympathetic input
43
How does Non- neural activation work
• Hormones can open and/or close ion channels changing membrane potential • Chemical stimuli can cause release of Ca++ from SR without a change in membrane potential • Other influences • Decreased oxygen, pH, body temperature
44
What is the regulation of contraction in smooth muscle compared to skeletal muscle
• Ca++ regulates cross bridge formation and thus cycling • BUT different from skeletal muscle • Control of Ca++ levels • Influence on cross bridge formation (myosin)
45
How are the cytosolic Ca2+ controlled in order to supply Ca2+ to smooth muscle
- receptor mechanisms like neurotransmitter or hormone - Membrane potential-dependent channels - Ca2+ released from sarcoplasmic reticulum upon receptor activation - Ca2+ removed
46
What is smooth muscle cross bridge controlled by
Cross bridge binding modulated by Ca++ dependent phosphorylation of myosin
47
What are the steps for relationship between crossbridge and Ca2+in smooth muscle
1. increase in cytosolic Ca2+ 2. Ca2+ binds to calmodulin in cytosol 3. Ca2+ - calmodulin complex binds to myosin 4. Myosin light-chain kinases uses ATP to phosphorylate myosin cross bridges 5. Phosphorylated cross bridge bind to actin filaments 6. Cross-bridge cycle produces tension and shortening
48
When can strength be exerted optimally
in an optimal length
49
What does tetanic contraction mean
maintaining the contraction
50
Where does the calcium from cardiac muscle come from
diffusion of extracellular calcium, not SR
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