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Human Physiology > Smooth and Cardiac muscle > Flashcards

Smooth and Cardiac muscle Flashcards

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1
Q

What are sarcomeres and where are they found?

A

Myosin and actin are arranged in sarcomeres in skeletal and cardiac muscle.
Smooth muscle does not have sarcomeres.

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2
Q

Which one hydrolyzes ATP into ADP+Pi?

  • myosin
  • tropomyosin
  • troponin
  • actin
A

myosin

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3
Q

In the theory of contraction what prevents filaments from sliding back to original position when myosin head is released to bind to another actin binding site?

A

The myosin head do not release simultaneously, tension is maintained.

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4
Q

What is isotonic and isometric contraction?

A

Isotonic: muscle contract and shorten creating enough force to move the load.
Isometric: muscle contract but does not shorten, not enough force to move the load. Because you can’t or you don’t wan to (voluntary movement).

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5
Q

Why the muscle doesn’t shorten during isometric contraction even if there is contraction?

A

Because of the elastic elements (tendons, muscle spindles and titin/connectin) in the muscle.

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6
Q

What is proprioception and kinesthesia?

A

Proprioception: knowing where part of the body is at any given time.
Kinesthesia: muscle memory.

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7
Q

What are the 3 types of proprioreceptors and what do they do?

A

Continuous input to coordinate skeletal muscle movement.

  • muscle spindles (stretch)
  • golgi tendon organs (tension)
  • joint capsule receptors (position)
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8
Q

What is the structure of muscle spindles?

A

Small elongated structures parallel muscle fibres.
Each spindle is made of extrafusal fibres wrapped around intrafusal fibres.
Extrafusal fibres are innervated by alpha motor neurons.
Intrafusal fibres have contractile endings and center with no myofibril. The endings are innervated with gamma motor neurons.

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9
Q

What s the structure of intrafusal fibers?

A

Ends are contractile with innervations with gamma motor neurons but centre lack myofibrils and are wrapped with sensory nerve endings stimulated by stretch connected to the spinal cord

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10
Q

What is muscle tone?

A

Tonically active spindles, at rest, the central region of intrafusal fibres is stretched enough to still activate sensory fibres.

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11
Q

What is reflex contraction?

A

Prevent muscle damage when movement increase prevent overstreching of spindle (stretch reflex).

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12
Q

What do gamma motor neurons do?

A

Keep muscle spindles active no matter the length of the muscle. (prevent slowing down of fire power).

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13
Q

What do alpha motor neurons do?

A

Shorten muscle and releases tension on muscle spindle capsule

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14
Q

What is alpha-gamma coactivation?

A

Keep the spindle activated when the muscle is contracted.
Alpha motor neurons contract muscle releasing the tension on the spindle, simultaneously, gamma motor neurons contract the contractile part of the intrafusal fibres which returns the tension on the spindle.

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15
Q

Order the stretch reflex process:

  1. Spinal cord integrates function
  2. The sensory neuron is tonically active
  3. Alpha motor neurons to extrafusal fibres receive tonic input from muscle spindles.
  4. Extrafusal muscle fibres at resting length.
  5. Extrafusal fibres maintain a certain level of tension even at rest.
A

4 2 1 3 5

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16
Q

Location of Golgi tendon organs

A

Found at the junction of tendons and muscle fibres, respond to muscle tension during isometric contraction.
Opposite of reflex contraction

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17
Q

Describe Golgi tendon reflex

A

Protect the muscle from tension damage from the excessive load by relaxing the muscle:

  1. Neuron from Golgi
  2. Alpha motor neuron inhibited
  3. Muscel relaxes
  4. Load is dropped
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18
Q

Activation and function of the Golgi tendon organ?

A

Contraction of muscle activate sensory neuron > synapse with inhibitory interneurons > synapse and inhibit motorneurons > causing muscle relaxation

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19
Q

What do joint capsule proprioceptors do?

A

Location of limbs in space. There are 4 types.

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20
Q

Describe reflex movements.

A

Knee jerk and posture

  • simples movements
  • integrated into spinal cord/ brain stem
  • minimal involvement of higher brain regions (no need to think too much)
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21
Q

Describe voluntary movements.

A

Playing the piano

  • most complex
  • integrated into the cerebral cortex
  • many ascending and descending pathways between thalamus, cerebellum, brain stem and spinal cord
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22
Q

Describe rhythmic movements.

A

Walking and running

  • intermediate complexity
  • combination of voluntary and reflex
  • initiation and termination need cerebral cortex
  • no need for continuous input (CPG - central pattern generator)
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23
Q

What are the 3 phases of voluntary movement? And what are the brain areas involved?

A
  1. Planning movement: basal ganglia, cortical association areas and cerebellum
  2. Initiating movement: motor cortex
  3. Executing movement: cerebellum
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24
Q

Arrange the stages of voluntary movement:

  • Corticospinal tract to skeletal muscle
  • Sensory input
  • Extrapyramidal influence on posture, balance and gait_
  • Planning and decision-making
  • Continuous feedback
  • Coordination and timing: cerebellar input
A
  1. Sensory input
  2. Planning and decision-making
  3. Coordination and timing: cerebellar input
  4. Execution: corticospinal tract to skeletal muscle
  5. Execution: extrapyramidal influence on posture, balance and gait.
  6. Continuous feedback
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25
Arrange the areas of the brain for voluntary movement control. - Thalamus - Spinal cord - Sensory cortex - Basal ganglia - Motor cortex - Prefrontal cortex and motor associations - Muscle contraction - Brain stem + cerebellum
1. Sensory cortex 2. Motor cortex 3. Prefrontal cortex and motor associations 4. Basal ganglia 5. Thalamus 6. Brain stem + cerebellum 7. Spinal cord 8. Muscle contraction
26
What is presynaptic visualization?
The modulation of input increases the release of neurotransmitters.
27
The contractile fibres of skeletal muscle are called? a. alpha motor neurons b. gamma motor neurons c. intrafusal fibres d. extrafusal fibres
d
28
Which of the following statement best describes muscle spindles? a. They are effective detectors of muscle tension. b. They are effective detectors of skeletal muscle stretch and help bring about compensatory changes in muscle length. c. They contain specialized muscle fibers called intrafusal fibers. d. They are found in skeletal muscle.
b
29
Consider different types of contraction in skeletal muscle, and complete the following sentences. In the first stages of a contraction, when the sarcomeres shorten the muscle fibres _________ . The sarcomeres are creating ________. If the muscle can create additional force to move the load, this is an _________ contraction; if they cannot, then the contraction is __________ . Also shorten significantly; tension; isometric; isotonic Maintain a relatively constant length; tension; isotonic; isometric Maintain a relatively constant length; tension; isometric; isotonic Also shorten significantly; elasticity; isometric; isotonic
b
30
What do all 3 muscle types have in common?
- intracellular Ca++ initiate muscle contraction (in differents ways tho) - myosin uses ATP to change conformation
31
Differences between the 3 muscle types?
- cell organization - control: different nerve types, motor units, endocrine - protein isoforms
32
What is troponin absent from?
Smooth muscle (has tropomyosin)
33
What does Smooth and Cardiac muscle have in common that skeletal muscle doesn't have?
Gap junction: electrical communication between the cells.
34
What is the difference between the twitch duration in the 3 muscle types?
They can all develop the same amount of tension Skeletal: fast-twitch Cardiac: fast-twitch Smooth: long-twitch
35
How does a cell to cell communication take place?
Gaps junction
36
What is the difference between cell-cell communication in the 3 muscle types?
Skeletal: no cell-cell junctions | Smooth and cardiac: gap junctions (rapid spread of depolarization)
37
Use the table of comparison between the 3 types of muscles.
Ok
38
Compared to skeletal muscle, smooth muscle __________. a. has specialized motor end plates b. has actin and myosin but not arranged in sarcomeres c. has more troponin d. contracts and relaxes more quickly
b
39
Cardiac muscle and smooth muscle are similar in that they both __________. a. have cells with multiple nuclei b. have t-tubules c. can be electrically linked, one cell to another d. are striated
c - gap junctions
40
Differences between smooth and skeletal muscle?
Colour: skeletal had more myoglobin (need more oxygen) as there is more contraction. Striation: skeletal parallel striations while smooth is jumbo/aggregation of cells.
41
What is the difference in activation between smooth and skeletal muscle?
Activation: both use Ca+ for activation but Ca+ of skeletal muscle comes from sarcoplasmic recticulum. Ca++ of smooth muscle comes from extracellular sources (interstitial fluid)
42
What is the function of calmodulin and where is it found?
Found in smooth muscle is the process in which myosin light chain kinase (MLCK) is activated which activates myosin to start cross bridge cycle.
43
What is troponin and where is it found?
Activated by Ca++ in skeletal muscle, it move tropomyosin away from binding site with shortens sarcomere and initiates cross bridge cycling.
44
What is the difference between skeletal and smooth sarcomeres?
Skeletal: can only move in one direction Smooth: can more in all directions
45
What can smooth muscle do that skeletal and cardiac cannot do?
More variant and can contract for long period of time
46
How re smooth muscles categorized?
- Location: vascular, urinary.. - Contraction pattern: phasic and tonic - Communication: single or multi unit
47
What is the difference between phasic and tonic smooth muscle?
Phasic: relaxed state until needs to be contracted (oesophagus/intestine) Tonic: in a constantly contracted state
48
Another name for single-unit smooth muscle communication?
Visceral smooth-muscle
49
How is the smooth muscle organized?
A cytoskeleton made of intermediate filaments and protein-dense bodies. Each myosin molecule is surrounded by actin filaments attached to the dense bodies.
50
Why can smooth muscle contract in all directions?
Because of the myosin heads facing different directions
51
What is the difference between single-unit and multi-unit communication in smooth muscle?
Single-unit: connected by gap junctions that allow cells to contract as a single unit (neurotransmitters stimulate all cells at the same time) Multi-unit: no electrical linkage each cell contract individually
52
What is the difference between smooth and skeletal muscle contraction?
SM: most of Ca++ comes from extracellular. SK: most of Ca++ from the sarcoplasmic reticulum SM: calmodulin and Ca++ complex activate MLCK SK: no MLCK SM: no troponin
53
Where is calmodulin found and what its function?
Found in smooth muscle and binds Ca++ which activates MLCK
54
What does MLCK do?
Phosphorite light chains of myosin heads in smooth muscle which increases myosin ATPase activity
55
What does an increase of myosin ATPase activity lead to?
Allow myosin to form cross-bridges across actin and form muscle tension (contraction)
56
What is the overall process of smooth muscle contraction?
1. Ca++ from extracellular enters the cell, and some Ca++ released from the sarcoplasmic reticulum 2. Ca++ binds to calmoduin 3. Ca++ and calmodulin complex activate MLCK 4. MLCK phosphorylates light chains in myosin heads and increases ATPase activity 5. ATPase increase allows myosin to form cross-bridges with actin and create muscle tension
57
What is the overall relaxation of smooth muscle?
1. Decrease Ca++ in trough actively pumping it outside the cell or in sarcoplasmic reticulum 2. Law of mass action leads to unbinding of Ca++ from Ca++ calmodulin complex, decreasing the activity of MLCK 3. MLCP removes phosphate from myosin light chain making them less active 4. No binding of myosin with actin thus no tension formation and no contraction
58
What is the difference between smooth and skeletal muscle relaxation?
SM: Ca++ is actively pumped out of the cell by ATPase SK:
59
What is the relation between MLCP and Ca++
Level of Ca++ affects the activity of MLCP. High Ca++ desensitizes myosin. Low Ca++ sensitizes
60
How do changes in phosphatase activity affect myosin Ca++ response?
Low phosphatase levels, myosin in sensitized to Ca++ and is activated at low Ca++ levels. On the other hand, high levels of phosphatase desensitize myosin (more Ca++ is needed for a response)
61
How is a contraction in smooth muscle initiated?
1. Signal ligands interacting with membrane receptors | 2. Depolarization or stretch affecting membrane channels
62
Which of the following statements comparing smooth muscles to skeletal muscles is FALSE? a. Smooth muscles have less myosin than skeletal muscle. b. Smooth muscles have more actin filaments than skeletal muscles. c. Smooth muscles have longer myosin filaments than skeletal muscles. d. Smooth muscles do no have any sarcoplasmic reticulum.
d
63
Which of the following statements is true? a. Skeletal muscles are controlled by autonomic neurons. b. Smooth muscles have calmodulin. c. Skeletal muscle cells are linked by gap junctions. d. Skeletal muscles are autorhythmic.
b
64
Are skeletal muscle auto rhythmic?
nope
65
What type of muscle will be more affected in a disorder affecting ATP metabolic pathway?
Skeletal muscle as it requires more energy to function
66
What toxin is found in tetanus?
tetanospasmin transported to the spinal cord by motor neurons
67
What is particular about relaxation in skeletal muscle?
Relaxation result from absence of excitatory input by somatic motor neurons.
68
What is a myotatic unit?
Collection of pathways controlling a single joint
69
How can movement be classified as?
Reflex, Voluntary and rhythmic
70
What is the function of the corticospinal tract?
Group of neurons controlling voluntary movements run from motor cortex to spinal cord

Human Physiology (2 decks)

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