Muscular System Flashcards Preview

Z Old Anatomy > Muscular System > Flashcards

Flashcards in Muscular System Deck (61):
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Functions of Muscle Tissue

  • Movement
  • Postural Maintenance
  • Joint Stabilization
  • Heat Generation
  • Support Organs
  • Guard Orifices

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Functional Properties of Muscle

Contractility - cells shorten, generating pulling force

Excitability - nerve impulses stimulate contraction

Extensibility - can be stretched back to original length by opposing muscle

Elasticity - can recoil after stretching

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Types of Muscle Tissue

Skeletal, Cardiac and Smooth

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Muscle Fibers

- single cells of skeletal and smooth muscles

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Cardiac Muscle Fiber

long row of joined cardiac muscle cells

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myofilaments

proteinaceous filaments that make up muscle fibers

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sarcolemma

plasma membrane of striated muscle fiber

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sarcoplasm

cytoplasm of muscle cell

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sarcoplasmic reticulum

- smooth ER of muscle cell

- stores and pumps calcium ions for excitation of muscle fiber in terminal cisternae

- meshwork around each myofibril

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myocardium

thick layer of cardiac muscle tissue in heart wall

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intercalated discs

 microscopic identifying features of cardiac muscle, they are the junctions between cells

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Longitudinal Layer of Smooth Muscle

runs parallel to organs long axis

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Circular Layer of Smooth Muscle

runs perpendicular to long axis of organ (around circumference)

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Six Locations of Smooth Muscle

- walls of circulatory vessels

- respiratory tubes

- digestive tubes

- urinary organs

- reproductive organs

- inside the eye

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Smooth Muscle Structure/Function

- non-striated cells without sarcomeres

- thin + thick filaments

- slow sustained contraction

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Single Muscle as Organ

- muscle tissue

- connective tissue

- blood vessels

- nerves

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Epimysium

dense CT around an entire muscle

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Perimysium

fibrous CT around each fascicle

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endomysium

fine sheath of CT (reticular fibers) around each muscle cell

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aponeuroses

- thin flattened sheets of tendon

ex: rectus abdominis

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Skeletal Muscle Structure Overview (from largest unit to smallest)

A muscle is made of bundles of fascicles which are made up of bundles of myofibers (muscle cells) which are made up of bundles of myofibrils which are made up of bundles of myofilaments

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Myosin

protein component of thick myofilaments

- look like braided golf clubs

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Actin

protein component of thin myofilaments

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Myofibrils

- long unbranched rods of myofilaments within sarcoplasm

- specialized contractile organelles

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Sarcomere

section of a myofibril between two Z lines

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Dark segment of a sarcomere that contains the full length of a thick myosin filament

A (anisotropic) band

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light segments of 2 adjacent sarcomeres (split by Z disc) that contains only thin actin filament

I (isotropic) band

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brighter zone of the a band that contains only thick filaments and is the middle of each sarcomere

H band

(german "heller" = brighter)

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very middle of sarcomere, in middle of H zone

M line

(german "Mittelscheibe)

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boundaries of each sarcomere that bisect I bands, occuring where there are only actin filaments

Z disc or line

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troponin

regulatory protein that holds tropomyosin in place on actin filaments, keeping muscle relaxed by preventing myosin crossbridge formation

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tropomyosin

two-stranded alpha-helical coiled coil protein that wraps around actin filaments, preventing myosin crossbridge formation

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crossbridge formation

when heads of myosin molecules bind to active sites on actin molecules causing muscle contraction

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tunnel-like infoldings of sarcolemma that penetrate cell and carry eletric current to its interior

T (transverse) Tubules

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Triad

a T-tubule and 2 terminal cisternae of the sarcoplasmic reticulum

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motor unit

each motor neuron and all the muscle fibers it innervates

fine control = fewer fibers per unit (eyes)

more strength = more fibers per unit (large skeletal muscles)

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synapse

connection between nerve fiber and target cell

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neuromuscular junction

specific name for synapse btwn motor nerve and muscle fiber

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bulbous swelling at end of motor nerve above motor end plate

synaptic knob (terminal or bouton)

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gap between synaptic knob and motor end plate

synaptic cleft

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small packets of neurotransmitters within a synaptic knob before they are exocytotically released into the synaptic cleft 

synaptic vesicles

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Skeletal Muscle Fiber Types

- naming based on speed of contraction and mode of ATP production

- Slow Oxidative (red/ dark-staining)

- Fast Glycolytic (white/ non-staining)

- Fast Oxidative (intermediate/ lighter-staining)

 

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Slow Oxidative Fibers

- stain darkly due to abundant myoglobin

- contract slowly and for longer

ex: back muscles, support muscles

 

seen as dark cells in picture

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Intermediate Fast Oxidative Fibers

- stain less darkly than red

- contract faster/ more powerfully than slow oxidative

- abundant in lower limbs and contract for longer periods

seen as slightly larger/lighter than dark red cells in picture: 

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Fast Glycolytic Fibers

- little myoglobin, don't stain

- largest diameter of three types

- anaerobic glycolysis

- contract rapidly but fatigue easily

- found in upper limbs for large work loads

- most abundant fiber type

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origin

less movable attachment

ex: biceps brachii to humerus

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insertion

more movable attachment

ex: biceps brachii to tibia

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two types of muscle attachments

direct/fleshy attachment - short connective tissue fibers

indirect attachment - CT forms tendon or aponeurosis

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4 Fascicle Arrangments

1. convergent (pec major)

2. parallel (biceps brachii)

3. circular (AKA sphincters, ex: orbicularis oris)

4. pennate ("feather like")

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Convergent Fascicle Arrangement

- broad origin with fascicles converging on tendon at insertion

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Parallel Fascicle Arrangement

- fascicles run parallel to long axis

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Circular Fascicle Arrangement

- arranged in concentric rings

- surround body openings and AKA sphincters

ex: orbicularis oculi

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Pennate Fascicle Arrangement

- feather-like with short fascicles attaching obliquely to tendon

- Unipennate - fascicles in one side of tendon

- Bipennate - fascicles in either side of tendon

- Multipennate - fascicles on all sides of tendon

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4 Functional Groups of Muscle

1. Prime Mover

2. Antagonist

3. Synergist

4. Fixator

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Prime Mover

- primarily responsible for producing a certain movement

ex: diaphragm for inspiration

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Antagonist

- opposes or reverses movement of prime mover

ex: internal intercostals in inspiration (depress rib cage, causing exhalation)

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Synergist

- helps prime mover by adding force and/or reducing undesirable movement

ex: external intercostals in inspiration (elevate ribcage)

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Fixator

- type of synergist that holds a bone firmly in place

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Muscle Naming Criteria

  • Location (intercostal)
  • Shape (deltoid)
  • Relative Size (maximus/minimus, longus/brevis)
  • Direction of Fascicles and Fibers (transversus)
  • Attachment Location (sternocleidomastoid)
  • Number of Origins (bi-, tri-, quadriceps)
  • Action (flexor, extensor)

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