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BIO 162 > Chapter 8 - Skeletal Muscle and Electromyography > Flashcards

Chapter 8 - Skeletal Muscle and Electromyography Flashcards

1
Q

Skeletal Muscle

A
  • Makes movement, breathing, speech, and facial expression possible
  • Almost completely under voluntary control
  • Cells are very large and have visible stripes called striations (which are made up of organized units of contractile proteins)
  • Cells are organized end-to-end and facilitate muscle shortening (or lengthening) to make movement possible
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2
Q

All types of muscle have the following characteristics in common…

A

Excitability (muscle cells produce action potentials), contractility (muscle cells can shorten), extensibility (muscle cells can be stretched or lengthened), elasticity (muscle cells will return to their original length after being stretched)

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3
Q

Muscle fibers

A

Individual muscle cells

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4
Q

Fascicles

A
  • The bundles of muscle fibers
  • Many make up one whole muscle and are wrapped in an outer membrane called the fascia
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5
Q

Fascia

A
  • Holds the fascicles as well as blood and nerves together in one large unit
  • Connect to the connective tissue making up tendons
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6
Q

Tendons

A

Anchor muscle tissue to the bones they work to move during contraction

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7
Q

Sarcolemma

A

The cell membrane that surrounds the muscle fiber (“sarco-“ = flesh)

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8
Q

Sarcoplasm

A

Cytoplasm in the sarcolemma

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9
Q

Myofibrils

A

Bundles of protein within the sarcoplasm

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10
Q

Myofilaments

A

Many individual overlapping protein strands that make up each myofibril

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11
Q

Sarcoplasmic Reticulum

A

The complex network of membranous sacs and tubes within the sarcoplasm that is full of calcium ions and surrounds each myofilament

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12
Q

Terminal Cisternae

A

The large sacs formed by the ends of the sarcoplasmic reticulum

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13
Q

Transverse Tubules (t-tubules)

A

The narrow tubes that the terminal cisternae of the sarcoplasmic reticulum

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14
Q

Thick & Thin Filaments

A
  • The two types of myofilaments contained within the myofibrils of the muscle fiber
  • Slide past one another and shorten the muscle cell during contraction
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15
Q

Sarcomere

A

The functional unit of a muscle cell and is formed by repeating units of thick and thin filaments that run end-to-end along the length of the muscle cell

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16
Q

Actin, Tropomyosin & Troponin

A

The different proteins that make up the thin filaments of the sarcomere

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17
Q

Actin (the thin filament)

A

A long string of globular proteins and looks like a strand of beads

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18
Q

Myosin

A
  • The protein that mostly makes up thick filaments
  • The head of the molecule is hinged and can move back and forth during muscle contraction
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19
Q

Active Site

A

In each molecule of actin and it allows the myosin to interact by attaching or binding to that specific site

20
Q

Tropomyosin

A

The long chains of a regulatory protein that cover the active sites on actin when the muscle is relaxed

21
Q

Troponin

A

Another smaller regulator protein that is attached along the lengths of the tropomyosin chains

22
Q

Cross-Bridge Formation

A

The myosin heads attach to the active site on actin

23
Q

Power Stroke

A
  • The action that is caused by the myosin heads pivots immediately after cross-bridge formation
  • Forces the actin filament to slide toward the the center of the sarcomere
24
Q

Attached Phase

A

The ADP and phosphate (P) left over from the original ATP molecule are released form the myosin

25
Q

Cross-Bridge Detachment

A

Allowed by the new ATP binding from the myosin remaining in a flexed attach position until a new ATP molecule binds to the myosin head

26
Q

Motor Unit

A
  • Consists of one motor neuron and all of the individual muscle cells it controls
  • Changing the number of these activated at a given time allows you to control how many muscle fibers contract within a single muscle
27
Q

2 reasons why not all motor units of a muscle are active at the same time

A
  1. Motor units allow muscles to modulate the strength of a contraction
  2. Motor units protect our muscles against fatigue
28
Q

Recruitment

A

The activation of additional motor units to increase muscle strength and force of contraction

29
Q

Fatigue

A
  • Not being able to sustain an expected force from a muscle
  • Fitness, age, psychology and physiology play a role in determining it
30
Q

Central Fatigue

A
  • Caused by the CNS and psychological mechanisms
  • Manifests as feeling “tired” or not wanting to go on
31
Q

Peripheral Fatigue

A
  • Defined as problems with the neuromuscular junction between the motor nerve and muscle or problems within the muscle cell at the level of the sarcomere
  • The calcium or ATP stores of the muscle cell may have been used up
  • Physiologically you cannot go on
32
Q

Maximal Grip Force

A
  • The amount of force that can be maintained by squeezing an object as hard as possible, can also be a useful diagnostic test
  • Inability to muster strength often happens late in life and is a predictor for senescent decline (end of life)
33
Q

3 types of muscle contraction

A

Isometric, concentric, and eccentric

34
Q

Isometric Contraction

A
  • A muscle may contract but not change length
  • If you hold a load in your hand and do not raise or lower it, just hold it still, then your biceps brachii muscle is in a state of …
  • The total force produced by the active sarcomeres is exactly balanced by the force of the load in the hand, and the length of the muscle does not change
35
Q

Concentric Contraction

A
  • A muscle will shorten in length
  • If you hold a load in your hand and raise it, then your biceps brachii muscle is in a state of …
  • The thick and thin filaments will slide past one another and the muscle will shorten
  • The total force produced by the active sarcomeres is greater than the force of the loaf in the hand, and the length of the muscle shortens
36
Q

Eccentric Contraction

A
  • A muscle may contract and actually become longer
  • If you hold a load in your hand and actively lower it (not just drop it), then your biceps brachii muscle is in a state of …
  • The total force produced by the active sarcomeres is less than the force of the load in the hand, and the length of the muscle becomes greater
37
Q

Antagonistic Pairs

A

Pairs that muscles can be arranged in

38
Q

Agonist

A

Sometimes called the prime mover and can be thought of as the muscle performing the desired action

39
Q

Antagonist

A

Capable of the opposing action

40
Q

Coactivation

A
  • When the motor units in both the agonist and antagonist are active at the same time
  • Is a common phenomenon and usually must occur to perform a controlled movement or stabilize a joint
41
Q

Flexion

A

Describes a decrease in the angle between body parts

42
Q

Extension

A

Increases the angle between adjacent body parts

43
Q

Abduction

A

Describes the movement of a body part away from the midline

44
Q

Adduction

A

Movement of a body part toward the midline (“adding” the limb back to your trunk)

45
Q

Electromyography (EMG)

A

Used to examine electrical activity generated by muscles

BIO 162 (2 decks)

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