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BIOL1046 Human Biology II > Unit 4A: Muscle Tissue and Muscle Physiology > Flashcards

Unit 4A: Muscle Tissue and Muscle Physiology Flashcards

1
Q

What is muscle tissue?

A

Muscle tissue is distributed almost everywhere in the body

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2
Q

What is the general function of muscle tissue?

A

Movement

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3
Q

How does muscle tissue conduct movement?

A
  • Moves food along gastrointestinal tract
  • Expels waste we produce
  • Moves air into and out of the lungs
  • Moves blood to and from body tissues
  • Moves the body and its parts
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4
Q

What are the 5 characteristics of muscle tissue?

A

Excitability, Conductivity, Contractility, Extensibility, Elasticity

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5
Q

What makes muscle tissue excitable?

A

Ability to respond to a stimulus by changing electrical membrane potential

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6
Q

What makes muscle tissue conductible?

A

Involves sending an electrical chnage down the length of the cell membrane

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7
Q

What makes muscle tissue contractile?

A
  • Exhibited when filaments slide past each other
  • Enables muscle to pull on bones and cause movement
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8
Q

What makes muscle tissue extensible?

A

Ability to be stretched

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9
Q

What makes muscle tissue elastic?

A

Ability to return to original length following a lengthening or shortening

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10
Q

What are the 3 types of muscle tissue?

A

Skeletal, Cardiac, and Smooth

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11
Q

The Muscular System

A
  • Made up of 700 skeletal muscles
  • Includes ONLY skeletal muscle
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12
Q

Skeletal Muscle

A
  • Muscle tissue used for movement
  • Attached to bones
  • Crosses over joints in order to cause movement
  • Voluntary muscle - under conscious control
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13
Q

Skeletal Muscle Cells

A
  • Long cylindrical cells
  • Multinucleate
  • Layers of proteins (actin and myosin)
  • Striated (striped) appearance due to layering of proteins
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14
Q

Cardiac Muscle Cells

A
  • Found only in the heart (cardiovascular system)
  • Small compared to skeletal muscle
  • Striated
  • Uni or binucleate
  • Branching
  • Joined by intercalated discs (desmosomes, gap junctions)
  • Involuntary muscle - autorhythmic
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15
Q

Smooth Muscle

A

Smooth muscle is found in a variety of organ systems with a variety of roles
(e.g. intestines of the digestive system)

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16
Q

Smooth Muscle Cells

A
  • Small compared to skeletal muscle
  • Uninucleate
  • Spindle shaped
  • Actin and myosin arranged differently (fishnet) so no striations
  • Involuntary muscle - controlled by ANS
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17
Q

Functions of the Muscular System

A
  1. Body Movement
    - Due to contraction of muscles attached to bones
    - Moves bones, make facial expressions, speak, breathe, swallow
  2. Maintain Posture
    - Stabilize joints, maintain body position
  3. Protect and Support
    - Abdominal and pelvic muscles protect internal organs and hold them in place
  4. Regulate Elimination of Materials
    - Circular Sphincters control passage of material at orifices
  5. Produce Heat
    - Help maintain body temperature
    - Heat produced by energy required for muscle contraction
    - Shivering to maintain homeostasis
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18
Q

How is each skeletal muscle an organ?

A
  • Multiple types of tissues working together: skeletal muscle fibres, connective tissue, blood vessels, and nerves
  • Each skeletal muscle consists of thousands of muscle cells (fibres)
  • Typically as long as the entire muscle
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19
Q

Fascicle

A
  • A whole muscle contains many fascicles
  • A fascicle consists of many muscle fibres
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20
Q

What are the 3 layers of connective tissue surrounding skeletal muscle?

A

Epimysium
Perimysium
Endomysium
*These 3 layers of connective tissue come together at the end of a muscle to form tendons, which attach muscle to bone

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21
Q

Epimysium

A

Dense irregular connective tissue wrapping while muscle

22
Q

Perimysium

A
  • Dense irregular connective tissue wrapping fascicle
  • Houses many blood vessels and nerves
23
Q

Endomysium

A
  • Aerolar connective tissue wrapping individual muscle fibres
  • Delicate layer for electrical insulation, capillary support, binding of neighbouring cells
24
Q

Tendon

A

Cordlike structure of dense regular connective tissue

25
Q

Aponeurosis

A

Thin, flattened sheet of dense irregular tissue

26
Q

Deep fascia

A
  • Dense irregular connective tissue superficial to epimysium
  • Seperates individual muscles; binds muscles with similar functions
27
Q

Superficial Fascia

A

Areolar and adipose connective tissue superficial to deep fascia
- Separates muscles from skin

28
Q

Blood Vessels and Nerves

A
  • Skeletal muscle is vacularized, has extensive blood vessels
  • Deliver oxygen and nutrients, removing waste products
  • Skeletal muscle in innervated by somatic motor neurons
  • Axons of neurons branch, terminate at neuromuscular junctions
  • Considered voluntary muscle, because contraction is voluntarily controlled
29
Q

Sarcoplasm (cytoplasm)

A
  • Has typical organelles plus contractile proteins and other specializations
  • Many mitochondria
30
Q

Sarcolemma (plasma membrane)

A
  • Sarcolemma has voltage-gated ion channels that allow for conduction for electrical signals
  • Has T-tubules (transverse tubules) that extend deep into the cell
  • Contain voltage-sensitive calcium channels
31
Q

Sarcoplasmic Reticulum

A
  • Internal membrane complex similar to smooth ER
  • Contains calcium pumps that import calcium
32
Q

Sarcomere

A

functional unit of a muscle cell

33
Q

Myofilament

A

fibrous protein of a muscle cell

34
Q

Myofibrils (hundreds to thousands per cell)

A

bundles of myofilaments enclosed in sarcoplasmic reticulum

35
Q

Myoglobin

A

haemoglobin in a muscle cell

36
Q

Myoblast

A

muscle building cell

37
Q

A muscle fibre is a

A

muscle cell

38
Q

Multiple Nuclei (individual cells are multinucleated)

A
  • Cell is formed in embryo when multiple myoblasts fuse
  • Some nearby myoblasts become undifferentiated satellite cells for support and repair of muscle fibres
39
Q

Myofilaments are contractile proteins within myofibrils; two types:

A

Thick Filaments
Thin Filaments

40
Q

Thick Filaments

A
  • Consist of bundles of many myosin protein molecules
  • Myosin heads point toward ends of the filament
41
Q

Thin Filaments

A
  • Twisted strands of actin
  • Tropomyosin and troponin are present; regulatory proteins
42
Q

Organization of a Sarcomere

A
  • Myofilaments arranged in repeating units called sarcomeres
  • Composed of overlapping thick and thin filaments
  • Delineated at both ends by Z discs
  • Specialized proteins perpendicular to myofilaments
  • Anchors for thin filaments
  • Connectin; Extends from Z disc to M line
  • Stabilizes thick filaments and has “springlike” properties (passive tension)
43
Q

The Positions of Thin and Thick filaments give rise to alternating I-bands (appear light) and A-bands (appear darker)

A
  • Alternating A-bands and I bands result in a striped or striated appearance
  • This is why skeletal muscle is also called striated muscle
44
Q

Sliding Filament Theory

A
  • Muscles contract when the thick and thin filaments slide over each other towards the M-line of a sarcomere.
  • When a muscle contracts the whole myofibril shortens because the individual filaments of each sarcomere slide across one another (*thick and thin filaments themselves do hot shorten!!)
  • Shortening does not always occur during contraction
  • Consider isometric contraction (holding a dumbbell at a constant position requires muscle contraction, but not muscle shortening)
45
Q

Explain the events of muscle relaxation?

A
  1. Termination of nerve signal and ACh release from motor neuron
  2. Hydrolysis of ACh by acetylcholinesterase
  3. Closure of ACh receptor casues cessation of end plate potential
  4. No further action by potential generation
  5. Closure of calcium channels in sarcoplasmic reticulum
  6. Return of Ca to sarcoplasmic reticulum by calcium pumps
  7. Return of troponin to original shape
  8. Return of tropomyosin blockade of actin’s myosin binding sites
  9. Return of muscle to original position due to its elasticity
46
Q

Rigor Mortis - Stiffness in the body after death

A
  • Cellular respiration ceases at the time of death and ATP is no longer produced
  • No ATP to keep calcium pumps going in Sarcoplasmic Reticulum
  • Causes calcium slowly leaks out of the sarcoplasmic reticulum within 2-4 hours
  • The calcium binds to troponin and moves the tropomyosin, exposing the active sites on the actin
  • Energized myosin heads bind to the actin and a power stroke occurs
  • No ATP is being produced
  • Therefore, the myosin heads cannot detach from the actin, and the muscles remain contracted - the body is in rigor (stiff)
  • Once decomposition begins, the myosin heads are broken down and the muscle begins to relax
  • Rigor mortis reaches its peak about 12-13 hours after death, and ends approx. 30 hours after death (depending on environmental conditions)
47
Q

Tendon

A

Attaches muscle to bone, skin, or another muscle

48
Q

Aponeurosis

A

Thin, flattened sheet-like tendon

49
Q

Most muscle cross at least one mobile joint

A
  • Upon contraction, one bone moves while other is fixed
  • Fixed bone attachment formerly called “origin”
  • Moveable bone attachment formerly called “insertion”
  • Action of the muscle occurs upon contraction
  • Muscles PULL, they never push
50
Q

Attachments for Axial Muscles

A

Superior attachment (usually more moveable)
Inferior attachment (usually less moveable)

51
Q

Attachments for Appendicular Muscles

A
  • Proximal Attachment (usually less moveable)
  • Distal Attachment (usually more moveable)
52
Q

Muscles Cross Joints

A
  • Proximal Attachments of biceps brachii are on scapula
  • Distal attachment of biceps brachii is on radius
  • Contraction pulls radius toward scapula, flexing the elbow

BIOL1046 Human Biology II (14 decks)

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