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Muscle Tissue
Chapter 10
45
Anatomy
Undergraduate 1
05/04/2009

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Term
muscle tone
Definition

Normal healthy muscles.Not weak or overly bulgy. resting tension in a skeletal muscle.

 muscle with low tone is limp and flaccid. Moderate toned muscles is firm and solid.

Term
tetany
Definition

muscles stiffness tightening muscles, contraction

 

Incomplete tetanus: almost at peak tension cycling btwn contraction and relaxation.

 

Complete tetanus: continuous contraction.

Term
treppe
Definition

increase in peak tension with each successive stimulus delivered shortly after completion of the relaxation phase of the preceding twitch.

 

warming up process

ex:warming up b4 exercise

staircase like rise

Term
Recruitment
Definition

smooth but steady increase in musclur tension produced by increasing the the number of active motor units.

 

mental decision about how many muscles fibers are required for a task

Term
Wave summation
Definition

when succesive stimuli arrive b4 relaxation phase has been completed, then a more powerful powerful contraction occurs. Contractions build on one another in waves

 

adding to load withouth resting in btwn

Term
superficial fascia
Definition
a sheet or band of fibrous tissue such as lies deep to the skin. Blends into reticular layer of the skin.  Also called hypodermis,the layer of areolar tissue and fat
Term
deep fascia
Definition

dense irregular connective tissue

in and around muscles packages

include epi-,peri-, and endomysium

Term
epimysium
Definition

outermost layer of connective tissue around entire muscle.

 

dense layer of collagen fibers that seperates the muscles from surrounding tissues

 

connected to deep fascia

 

Term
perimysium
Definition

divides muscle fibers into fascicles

 

possesses collagen and elastic fibers and blood vessles and nerves that branch out for each fascicle

Term
endomysium
Definition

delicate connective tissue that surrounds individual skeletal muscle cells or fibers and loosely connects with adjacent muscle fibers

 

flexible elastic network contains capillaries and myosatellite cells

Term
motor unit
Definition

all the muscle fibers controlled by a single motor neuron.

 

size of motor unit is an indication of how fine the control of movement is. The fewer the # of fibers per neuron the finer the control. ie eye muscles (4-6)vs leg muscles(1000-2000).

Term

neuromuscular junction

NMJ

Definition

connection and  btwn nervous system and skeletal muscle fiber that occurs at specialized intercellular connection---actually little space btwn called synapse.

Term
synapse
Definition

narrow space btwn nerve cell and muscle cell

 

more specifically space btwn motor end plate on nerve cell  and sacrolemmal surface of muscle cell

 

 

Term
motor endplate
Definition

spot on muscle cell where nerve cell touches it.

ex: door bell on door.

 

contains membrane receptors for acetylcholine

Term
sarcomere
Definition
Term
Muscle cell features
Definition

nucleus toward outside

mitochondia: randomly scattered

ER also on outside of cell

 

Term
sarcolemma
Definition
membrane of muscle cell
Term
T-tubules or Transverse tubules
Definition

narrow tubes that are continuous with the sarcolemma and extend into the sarcoplasm at right angles to the cell surface.

 

conducts electrical impulses into cell interior

has same properties as sarcolemma

Term
sarcomere
Definition

single repeating contractile unit of muscle filamentsfrom Z line to Z line

 

I-band: only thin filaments, light colored band

A-band:thick filaments,has thin in zone of overlap in contracted state

H-band: central A band in resting state that contain only thick filaments

 

Term
actin
Definition

thin myofilaments

do the moving

 

Term
myosin
Definition

thick myofilaments

do the pulling

myosin molecule:head,hinge,tail

Term
titin
Definition

elastic myofilaments associated with myosin/thick filaments

coiled spring

Term
sacroplasmic reticulum
Definition

membrane complex related to smooth ER

tubular network around each individual myofibril

Term
cross bridge
Definition

when myosin heads interact with thin filaments of actin during a contraction only in the presence of calcium

 

Term
power stroke
Definition

physical movement of the myosin head toward the M line after the cross bridge is fomed

the myosin is the doing the work but the actin is doing the moving

ATP is required

 

Term
neurotransmitter
Definition
a chemical released by a neuron to change the permeability or other properties of another plasma membrane.
Term
acetylcholine (Ach)
Definition

made by nerve cell at motor endplate

changes permeability of sarcolemma and triggers the contraction of the muscle fiber

Term
Acetylcholinesterase (Ach-ase)
Definition

breaks down Ach

found in synaptic cleft and ssarcolemma

Term
triad
Definition

combination of a pair of terminal cisternae (bulges) of sacroplasmic reticulum  (SR) on either side of a T-tubule

 

function to release calcium

Term
calsequestrine
Definition

a protein that reversibly binds Calcium

 

sequesters the calcium

 

collects the calcium gets it away from the thin filament and puts it back in the SR until the next contraction

Term
calcium
Definition

stored in SR

released Ca binds to troponin to expose actin active sites

gets reabsorbed by SR

Term
Aerobic Respiration
Definition

takes place in mitochondria

glucose + O2 yields CO2 +H2O +36 (17) ATP

via Krebs cycle

resting muscles use aerobic process

Term
anaerobic respiration
Definition

glucose (no oxygen)yields CO2 +lactic acid

incomplete breakdown of glucose

also called glycolysis

lactic acid irratates muscles,nerves

produces 2 ATP

(yeast produces CO2 +alcohol by fermentation)

 

Term
fatigue
Definition

when muscles run out of oxygen

rising lactic levels lower tissue pH levels then muscles can no longer function normally

 

muscles needs enough energy supplysupplies,blood flow, normal oxygen levels,and normall pH levels

Term
lactic acid
Definition

by-product of anaerobic respiration

 

build up lowers pH and interferes with contraction

 

recycled back to pyruvic acid when O2 available

 

Term
creatinine phosphate (CP)
Definition

during a contraction, each myosin head breaks down ATP producing ADP and a phosphate group. Energy stored in CP is used to "recharge" ADP back to ATP

 

ADP +CP --> ATP + creatine

Term
myogram
Definition

graphic illustration of muscle contraction

 

gap:latent period

rising slope:contraction phase

decling slope:relaxation phase

resting phase: flat line b4 stimulus

 

 

 

Term
Latent period
Definition

Latent period:gap after stimulus and before contraction when Na+ changes permeability of membrane,action potential sweeps across sarcolemma,SR releases Ca and diffuses to thin filament

Term
Contraction phase
Definition

Contraction phase: occurs in 5 steps

 

1.exposure of active sites as Ca binds to troponin

 

2.formation of cross-bridges--myosin head binds active site on actin

 

3.pivoting of myosin heads toward M line requiring ATP--ie power-stroke

4.cross-bridge detachment

5.myosin reactivation--re-cocking of myosin head away from M-line. Requires ATP.

 

process repeats if suffient ATP and Ca ions

 

Term
Relaxation phase
Definition

Relaxation phase: Ca levels fall,active site covered, cross-bridges detach,tension falls

 

myogram line has downward slope

Term
refractory period
Definition

period after contraction that muscles is busy and can't be stimulated again

 

UNLESS the second signal is so much stronger

Term

General characteristics of:

 

Skeletal Muscle Tissue

Definition

largest type of muscle cell

striated:alternating thin and thick filaments

multinucleated,nuclei on outside

voluntary

Term

General characteristics of :

 

Smooth Muscle Tissue

Definition

found in respiratory,digestive,urinary,repro sys

relatively long n slender:spindle-shaped

non-striated..no myofibrils or sacromeres

thick filaments scattered in cytoplasm

involuntary: can't control

not striated

has actin,myosin organized in criss-cross pattern

single nucleus in center

Term

General characteristics of:

 

Cardiac Muscle

Definition

myofibrils  in sacromeres like skeletal muscle

striated like skeletal muscle

relatively small cell size

single cental nucleus like smooth muscle

joined to intercalated discs at Zlines to give strength and stability

contracts w/o neural stimulation:automaticity

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