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LSB142 Anatomy and Physiology > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

(65 cards)

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1
Q

Why do we need muscle tissue?

A

➢ Locomotion – movement of the body
➢ Stability – maintenance of posture
➢ Movement of substances internally (e.g. blood, food)
➢ Heat production

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2
Q

What does muscle tissue do to organs?

A
  1. Pull on a body structure
    e.g. A skeletal muscle organ can pull 2 bones closer together.
  2. Alter its’ internal volume
    e.g. Contraction of cardiac muscle forces blood out of the heart
    chambers.
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3
Q

What in muscle cells allow contraction?

A

Muscle cells contain networks of protein filaments (actin &

myosin) that facilitate the contraction process.

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4
Q

What are the 3 types of muscle tissue in the human body and what are their features?

A

➢ Skeletal- Striated,
long fibres
➢ Cardiac - Striated,
branched fibres, endomysium attached to the fibrous skeleton of the heart, slow and rhythmic contraction
➢ Smooth - Non-striated,
spindle-shaped long
cells, endomysium, very slow contractions. some are rhythmic

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5
Q

What do these root words mean?

  1. mus
  2. myo
  3. sarco
  4. plasm
  5. lemma
  6. mere
A
  1. muscle
  2. muscle
  3. flesh
  4. form or mould
  5. sheath or husk
  6. segment
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6
Q

Skeletal muscles functions

A
  • Skeletal muscles integrate with bones &
    joints to form lever systems that facilitate
    movement.
    ➢ Move from place to place (locomotion)
    ➢ Manipulate objects
    ➢ Communicate & breathe
    ➢ Maintain body posture
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7
Q

What are skeletal muscle fibres surrounded by?

A
  • Bundles (10-100) of skeletal muscle fibres are wrapped by

connective tissue & are called fascicles

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8
Q

Structure of skeletal muscle cells

A

Skeletal muscle cells (fibres) are;
➢ Long cylinders (up to 30cm long)
➢ Striated (striped)
➢ Multinucleated (100+ nuclei in one fibre)
A skeletal muscle fibre contains these structures;
➢ Sarcolemma - muscle fibre plasma membrane
➢ Sarcoplasm - muscle fibre cytoplasm
➢ Myofibrils – long rod-like structures that contain contractile
proteins (make up ~80% cell volume).

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9
Q

Skeletal muscle tissue structure

A

Muscle fibres posses many myofibrils which contain contractile
units (sarcomeres) which generate movement.

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10
Q

What are myofibrils?

A

Myofibrils contain repeating contractile units called

sarcomeres which facilitate muscle movement

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11
Q

What are sarcomeres?

A

➢ Contain interlocking actin (thin) & myosin (thick) filament
proteins.
➢ Contract when a stimulated by a signal from a neurone
(somatic motor).

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12
Q

Thick Myosin filaments

A 
Made up of 200 to 500 myosin molecules.
➢ Attached to the M line in a sarcomere
Each myosin molecule consists of rod-like tail terminating at 2
globular heads.
➢ Heads contain sites that bind to actin
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13
Q

Thin Actin Filaments

A

Fibrous (F) actin filaments are composed of globular (G) actin
subunits
➢ Stiffened by tropomyosin protein strand
➢ Actin filaments are attached to the Z disc in a sarcomere
Myosin heads bind to G actin subunits
➢ Troponin is a molecule attached to tropomyosin that helps
regulate the myosin – actin binding

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14
Q

Sarcomere Contraction

A

When a skeletal muscle cell is stimulated, actin
filaments in the sarcomere slide over myosin filaments.
The sarcomeres shorten & the muscle contracts.

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15
Q

What tissues do skeletal muscles contain?

A
  1. Connective tissue
    Layers of connective tissue wrap & reinforce muscle fibres
  2. Nerve cells (neurones)
    Supply signals that stimulate muscle cells to contract
  3. Epithelial tissue
    Lines inner surface of blood vessels
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16
Q

What are the connective tissue layers?

A

epimysium, perimysium

& endomysium.

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17
Q

Features of connective tissue layers

A

➢ are continuous with one another
➢ provide structural reinforcement for the muscle
➢ provide access for nerves & blood vessels

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18
Q

Explain the 4 connective tissue layers

A
  1. Deep Fascia: Lines the body wall & separates muscles into
    functional groups.
  2. Epimysium: Surrounds an individual muscle organ & blend
    with tendons or deep fascia.
  3. Perimysium: Bundles together 10 - 100 individual muscle
    fibres into structures called fascicles.
  4. Endomysium: The connective tissue wrapping of an individual
    muscle fibre
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19
Q

Where is the primary motor cortex located?

A

Posterior aspect of the frontal lobe

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20
Q

Motor neurons cross over in which parts of the body

A

➢ Medulla, or

➢ Spinal cord.

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21
Q

What is a motor unit?

A

A neurone and all the muscle fibres it innervates

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22
Q

What are fascicles?

A

Bundles of 10-100 skeletal muscle fibres wrapped by connective tissues

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23
Q

What are the components of a skeletal muscle fibre model?

A
  • Myofibril
  • Sarcomere
  • Motor end plate
  • Motor Neurone
  • Synaptic Knob
  • Schwann cell
  • Node of Ranvier
  • Nucleus
  • Sarcoplasmic reticulum
  • Sarcolemma
  • Endomysium
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24
Q

What is Motor Homunculus?

A

Different regions of the motor cortex control muscle contraction in specific areas of the body

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25
What is contralateral control?
Motor cortex controls skeletal muscle contraction on the opposite side of the body
26
How do neurons communicate with muscle fibres?
At neuromuscular junctions | - a small gap separates the 2 cells (synaptic cleft)
27
How many skeletal muscles are in the body?
600
28
Major Anatomical features of Skeletal Muscles
Origin: Attachment points of muscle to a location which does not move during muscle contraction Belly: Thicker, middle region of muscle Insertion: Attachment points of muscle to a location which will be moved by contraction of muscle
29
How does skeletal muscles attach to the body?
Via a tendon or tendon sheet (aponeurosis)
30
Criteria of naming muscles (7)
1. Direction of muscle fibres 2. Relative size of muscle 3. Location 4. Number of origins 5. Location of origin and insertion 6. Shape 7. Action
31
What is a movement initiated by a muscle called and how does it do it?
Action, it is done by the muscles pulling on a bone
32
Antagonists
Oppose of reverse a particular movement
33
What is a tendon?
▪ Mostly collagen fibers ▪ Often cross a joint because of their toughness and small size
34
What is aponeuroses
Attach muscles indirectly to bones, cartilages, or | connective tissue coverings
35
Skeletal muscle fibre types
▪ Slow-twitch (type I) fibres ▪ Fast-twitch (type II) fibres ▪ Type IIa fibres ▪ Type IIb fibres
36
2 components of the smooth muscles
Mucosa, Submucosa
37
Types of muscle contraction
1. Isotonic Contractions Myofilaments are able to slide past each other during contractions ▪ The muscle shortens, and movement occurs ▪ Example: bending the knee; lifting weights, smiling 2. Isometric Contraction ▪ Muscle filaments are trying to slide, but the muscle is pitted against an immovable object ▪ Tension increases, but muscles do not shorten ▪ Example: pushing your palms together in front of you
38
I band
light band ▪ Contains only thin filaments ▪ Z disc is a midline interruption
39
A band
dark band ▪ Contains the entire length of the thick filaments ▪ H zone is a lighter central area ▪ M line is in center of H zone
40
What is a neuromuscular junction?
Association site of axon terminal of the motor neuron | and sarcolemma of a muscle
41
Neurotransmitter
Chemical released by nerve upon arrival of nerve | impulse in the axon terminal
42
Synaptic cleft
Gap between nerve and muscle filled with interstitial fluid | ▪ Although very close, the nerve and muscle do not make contact
43
Events at the neuromuscular junction
CHECK PIC - 6 steps
44
What leaves the muscle fibre and what enters the muscle fibre during contraction?
Potassium ions leave the fibre, sodium ions enters through permeable synaptic cleft created by Ach
45
Why do filaments slide (steps)?
▪ Calcium ions (Ca2+ ) bind regulatory proteins on thin filaments and expose myosin-binding sites, allowing the myosin heads on the thick filaments to attach ▪ Each cross bridge pivots, causing the thin filaments to slide toward the center of the sarcomere ▪ Contraction occurs, and the cell shortens ▪ During a contraction, a cross bridge attaches and detaches several times ▪ ATP provides the energy for the sliding process, which continues as long as calcium ions are present
46
Cross bridge cycle
1. Cross bridge formation. The activated myosin head binds to actin forming a cross bridge. Inorganic phosphate is released. Bond between myosin and actin becomes stronger 2. Power stroke. ADP is released and the activated myosin head pivots, sliding the thin myofilament toward the centre of the sarcomere 3. Cross bridge detachment: When another ATP binds to the myosin head, the link between myosin head and actin weakens and the myosin head detaches
47
Functional properties of skeletal muscle cells
▪ Extensibility—ability of muscle cells to be stretched ▪ Elasticity—ability to recoil and resume resting length after stretching ▪ Irritability (also called responsiveness)—ability to receive and respond to a stimulus ▪ Contractility—ability to forcibly shorten when an adequate stimulus is received
48
Three pathways to regenerate ATP
▪ Three pathways to regenerate ATP 1. Direct phosphorylation of ADP by creating phosphate 2. Aerobic pathway 3. Anaerobic glycolysis and lactic acid formation
49
What is flexion and extension?
Flexion - Decreases angle in joint, common in hinge and ball and socket joins Extension - Increases angle between two bones Greater than 180 degrees is called hyper extension
50
Rotation
▪ Movement of a bone around its longitudinal axis | ▪ Common in ball-and-socket joints
51
What is Dorsiflexion?
``` ▪ Lifting the foot so that the superior surface approaches the shin (toward the dorsum) ```
52
What is Plantar Flexion?
Pointing the toes away from the head
53
What is inversion and eversion?
Inversion ▪ Turning sole of foot medially Eversion ▪ Turning sole of foot laterally
54
What is Supination and Pronation?
Supination ▪ Forearm rotates laterally so palm faces anteriorly ▪ Radius and ulna are parallel Pronation ▪ Forearm rotates medially so palm faces posteriorly ▪ Radius and ulna cross each other like an X
55
Opposition
▪ Moving the thumb to touch the tips of other fingers on | the same hand
56
What are the three things can happen when muscles have tension?
1. Shorten 2. Stay the same 3. Lengthen
57
Agonist
muscle with the major responsibility for | a certain movement
58
What is a synergist?
muscle that aids a prime mover in a | movement or reduces undesirable movements
59
What is a fixator?
specialized synergists that hold a bone | still or stabilize the origin of a prime mover
60
Fascicle Arrangement (4)
Circular Convergent Parallel Pennate
61
What is a pennate muscle and types?
one or more tendons extending through body. Large feather like oblique angled arrangements of fascicles. 3 types (Multipenate, bipennate and unipennate)
62
What is a graded response?
▪ Muscle fiber contraction is “all-or-none,” meaning it will contract to its fullest when stimulated adequately ▪ Within a whole skeletal muscle, not all fibers may be stimulated during the same interval ▪ Different combinations of muscle fiber contractions may give differing responses ▪ Graded responses—different degrees of skeletal muscle shortening
63
How can graded response be produced?
By changing the frequency of muscle stimulation By changing the number of muscle cells being stimulated at one time
64
Muscle response to increasingly rapid stimulation
▪ Muscle twitch ▪ Single, brief, jerky contraction ▪ Not a normal muscle function ▪ In most types of muscle activity, nerve impulses are delivered at a rapid rate ▪ As a result, contractions are “summed” (added) together, and one contraction is immediately followed by another ▪ When stimulations become more frequent, muscle contractions get stronger and smoother ▪ Fused (complete) tetanus is achieved when the muscle is stimulated so rapidly that no evidence of relaxation is seen ▪ Contractions are smooth and sustained
65
Muscle response to strong stimuli
▪ Muscle force depends upon the number of fibers stimulated ▪ Contraction of more fibers results in greater muscle tension ▪ When all motor units are active and stimulated, the muscle contraction is as strong as it can get

LSB142 Anatomy and Physiology (15 decks)

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