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Ch. 11 Muscular Tissue
Types and Characteristics of Muscle, Flaccid Paralysis
44
Anatomy
Undergraduate 1
11/16/2009

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Cards

Term
Universal Characteristics of Muscle- Responsiveness
Definition
Capable of response to chemical signals, stretch or other signals and responding with electrical changes across the plasma membrane
Term
Universal Characteristics of Muscle- Conductivity
Definition

Sharing

 

local electrical charge triggers a wave of excitation that travels along the muscle fiber

Term
Universal Characteristic of Muscle- Contractility
Definition

Force


Shortens when stimulated

Term
Universal Characteristics of Muscle- Extensibility
Definition

Relaxation

 

Capable of being stretched

Term
Universal Characteristics of Muscle- Elasticity
Definition

reoil/resume

 

returns to its original resting length after being stretched

Term
Skeletal Muscle- Muscle Fiber
Definition

voluntary, striated muscle attached to bones

 

muslce fibers (myofibers) as long as 30 cm

 

alternating light and dark transverse bands/striations

 

striations reflect overlapping arrangement of internal contractile proteins (myofilaments) actin and myosin

Term
Skeletal Muscle- Connective Tissue
Definition

Parallel Elastic Components

Series Elastic Components

 

  • Found between muscle fiber and bone or other attachment
  • Not excitable or elastic, but are somewhat extensible and elastic
  • stretches slightly under tension and recoils when released
  • Not contractile or physically able to change length
Term
CT of Muscle Tissue- Parallel Elastic Components
Definition

surrounds contractile parts

 

connected to each other in linear series

  • Endomysium-> Perimysium->epimysium

 

Term
CT of Muscle Tissue- Series Elastic Components
Definition

Joined at end

  • Tendon, periosteum, bone matrix

help return muscles to their resting lengths

 

adds significantly to power output and efficiency of muscles

Term
Skeletal Muscle Fibers
Definition

Multinucleated-- multiple nuclei against inside of Plasma Membrane

 

Sarcolemma

 

Sarcoplasm

 

Sarcoplasmic Reticulum

Term
Skeletal Muscle Fibers- Sarcolemma
Definition

lemma = husk

 

plasma membrane

 

has tunnel-like infoldings or transverse (T) tubules that penetrate the cell

 

carry out electric current to cell interior

Term
Skeletal Muscle Fibers- Sarcoplasm
Definition

Cytoplasm


  • filled with long protein bundles called myofibrils
  • myofibrils = bundles of parallel protein microfilaments called myofilaments
  • myofilaments = actin and myosin
  • glycogen stored for energy
  • myoglobin = unit inside muscle cell that is receptive to oxygen
Term
Skeletal Muscle Fibers- Sarcoplasmic Reticulum
Definition

Smooth Endoplasmic Reticulum

 

Interconnected network

 

Ca++ resovoir (collecting and distributing Ca++)

Term
Sarcomere
Definition

1 functional contractile unit of muscle fiber

 

sarco = muscle

mere = segment

 

Contractile Proteins: Actin and Myosin

 

1 myosin surrounded by 6 actin

Term
Sarcomere- Actin
Definition

Thin Filaments

 

Contractile Protein

  • 2 intertwined strands of fibrous (F) actin
  • each subunit is a globular (G) Actin with an active site (most F actin, few G)
  • Groove holds Tropomyosin molecules, each blocking the active sites of Actin
  • One small, calcium-binding troponin molecule stuck to each tropomyosin

 

Term
Sarcomere-Myosin
Definition

Thick Filaments

 

Contractile Protein

  • made of 200-500 myosin molecules
  • 2 entwined polypeptides (Golfclubs)
  • Arranged in a bundle of with heads (cross bridges) directed outward in a spiral array around the bundled tails
  • strategically placed heads to aid in muscle interaction, heads must be lined up in order
  • middle = bare zone (no heads, only tails) where there is no interaction
Term
Tropomyosin
Definition

Regulatory Protein

 

blocks active sites of Actin so that it cannot bind with myosin

Term
Troponin
Definition

Small, Calcium binding molecule that is stuck to each Tropomyosin molecule

 

 

Highly sensitive to calcium

 

contains a Tropin complex

Term
Elastic Filaments
Definition

Huge springy protein called titin 

 

runs through core of each thick filament

 

connects thick filament to Z disc structure

 

 

Term
Titin
Definition

Elastic Filament

 

Functions: keep thick and thin filaments aligned with each other

 

resist overstretching

 

help the cell recoil to its resting length (elasticity)

Term
Regulatory Proteins
Definition

Troponin + Tropomyosin = on/off switch

 

act like a switch that starts and stops shortening of muscle cell

 

*Ca++ is key*

the release of calcium into sarcoplasm and its binding to troponin activates contraction

 

Troponin moves the Tropomyosin off the actin active sites

Term
Contractile Proteins
Definition

Myosin and Actin

 

bond if they crossbridge

 

crossbridging = binding

 

myosin head binds with actin binding site

Term
Striations
Definition

dark band regions alternating with lighter band regions

 

 

Term
A- Band
Definition

thick filament region

 

myosin filament

 

center of filament

Term
H- Band
Definition

area contains no think filament

 

no actin, only myosin

Term
I- Band
Definition

thin filament region

 

bisected by Z disc protein called connectin

 

one at each end of sarcomere

 

no myosin, only actin

Term
Connectin
Definition

makes up the actual Z line

 

anchors elastic and thin filaments

 

Z line = Z disc

Term
Single Sarcomere
Definition

from one Z disc (Z line) to the next

 

hundreds of myosin and actin make up one sarcomere

Term
Contracted Sarcomere
Definition

Muscle cells shorten because their individual sarcomeres shorten

 

Z discs are pulled closer together

 

Thick and Thin filaments don't change length during shortening

They overlap (sliding filament theory)-crossbridging

 

Z discs approximate one another

Term
Contracted Sarcomere- H Zone
Definition

only myosin

 

SHRINKZ gets shorter

Term
Contracted Sarcomere- I band
Definition

only actin

 

SHRINKZ gets shorter

Term
Contracted Sarcomere- Z line
Definition

ends

 

SHRINKZ gets shorter

Term
Contracted Sarcomere- A band
Definition

anywhere there is myosin

 

SAME do not change shape

Term
Nerve-Muscle Relationships
Definition
  • Skeletal muscle must be stimulated by a nerve or it will not contract
  • Cell bodies of somatic motor neurons are in brainstem or spinal cord
  • Axons of somatic motor neurons are called somatic motor fibers
  • each branches into 200 terminal branches that supply 1 muscle fiber each
  • each motor neuron and all the muscle dibers it innervates are called a MOTOR UNIT
Term
Motor Unit
Definition

a motor neuron and the muscle fibers it innervates

 

dispersed throughout muscle

 

works in shifts- 1 motor unit stimulates 1 type of muscle fiber; when fatigued, other parts that have been resting can kick in

 

small motor unit

large motor unit

Term
small motor unit
Definition

contain as few as 20 muscle fibers per nerve fiber

 

means less fibers per nerve

 

in fingers and fine detailed movements

Term
large motor unit
Definition

more muscle fibers per nerve

 

able to accomplish larger tasks

 

gastrochemius muscle has 1,000 fibers per nerve fiber

Term
Neuromuscular Junction (Synapse)
Definition

region where a nerve fiber makes a functional connection with its muscle (NMJ)

 

Neurotransmitter (achetlycholine/ACh) released from the nerve fiber causes stimulation of the muscle cell

 

neuro = nerve

transmitter = meaning to propogate/transmit

Term
Components of a synapse- synaptic knob
Definition

swollen end of nerve fiber (contains ACh)

 

 

has synaptic vesicles with neurotransmitter

Term
Components of a synapse- Motor End Plate
Definition

specialized region of muscle cell surface

 

has ACh receptors on membrane which bind ACh released from nerve; receptors are just waiting to receive ACh

 

AChase is an enzyme that breaks down ACh and causes relaxation

Term
Components of a synapse- synaptic cleft
Definition
tiny gap between nerve and muscle cells
Term
Components of Synapse- Sarcolemma
Definition

plasma membrane/husk that covers muscle fiber

 

attaches at all points to increase surface area

Term
Spastic & Flaccid Paralysis
Definition
  • Pesticides contain inhibitors that bind to AChase and prevent it from degrading ACh--> spastic paralysis and possible suffocation
  • Tetanus or lockjaw is spastic paralysis caused by toxin of Clostridium bacteria- blocks glycine release in spinal cord and causes over stimulation/constant contraction of muscles
  • Flaccid Paralysis with limp muscles unable to contract b/c currare takes up space where ACh should be ACh--> respiratory arrest
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