honors anatomy & physiology. 3 types: 1. skeletal striated & voluntary 2. cardiac striated...
TRANSCRIPT
3 types:1. Skeletal
striated & voluntary
2. Cardiac striated & involuntary
3. Smooth Smooth & involuntary
Types of Muscle Tissue
found only in walls of heart chambersheart has a pacemaker that initiates each
contractioncalled autorhymicitycontrolled by hormones &
neurotransmitters
Cardiac Muscle Tissue
in walls of hollow organsattached to hair folliclessome autorhythmic (wall of intestines)regulated by ANS motor neuron&
hormones
Smooth Muscle Tissue
2. stabilizing body positionskeletal muscles stabilize joints &
halp maintain body positionspostural muscles hold sustained
contractions (holding head up all day)
Functions
3. storing & moving substances w/in bodystoring: accompanied by sustained
contractions of ringlike bands of smooth muscle called sphincters (hold material in organ)
contraction/relaxation of smooth & cardiac muscle moves material thru bld vessels heart bld vessels
Functions
4. generating heatprocess called thermogenesismost of heat generated by muscle
contraction maintains normal body temp of 37°C
shivering: involuntary contraction of skeletal muscle increases heat production
Functions
1. electrical excitabilityability to respond to certain stimuli
by producing electrical signals called action potentials
2 main types stimuli:1. autorhythmic electrical signals2. chemical stimuli (neurotransmitters)
released by neurons
Properties of Muscle Tissue (#4)
2. contractilityability of muscle fibers to contract
forcefully when stimulated by an action potential
muscle fiber shortens & pulls on whatever it is attached toif force > resistance of object,
movement occurs
Properties
3. extensibilityability of muscle tissue to stretch
w/out being damagedsmooth muscle fibers are stretched
every time your stomach or bladder is really full
Properties
4. elasticityability of muscle tissue to return to
original length & shape after contraction or extension
Properties
fascia: sheet or broad band of fibrous CT that supports & surrounds muscles or other organs2 layers: superficial & deep
CT Components
2. 3 layers of CT extend from deep fascia deeper into muscle tissue1. epimysium: outermost layer,
encircles entire muscle2. perimysium: surrounds groups of 10
– 100 muscle fibers = a fascicle3. endomysium: surrounds individual
muscle fibers
CT Components
3. tendon: extension of epimysium, perimysium, & endomysium beyond muscle that attaches the skeletal muscle to another structure (bone or another muscle)
CT Components
hypertrophy: enlargement of existing muscle fibersex: muscle growth in newborn
hyperplasia: increase in # of muscle fibersex: growth hormone causes increase in
#s from childhood adultfibrosis: replacement of muscle by
fibrous scar tissuesatellite cells: stem cells in muscle
tissue; limited capacity
Muscle Histology Terms
sarcolemma: plasma membrane sarcoplasm: cytoplasmmyofibril: contractile organelles;
thread-like structures; each extends length of muscle fiber
Terms for Muscle Fiber Organelles
T tubules: (transverse) invaginations of sarcolemma into sarcoplasma; increasing surface areafilled with interstitial fluidensures action potentials excites all
parts of muscle fiber
Terms for Muscle Fiber Organelles
sarcoplasmic reticulum: (SR) endoplasmic reticulum that encircles individual myofibrilsdilated end sacs called terminal
cistern T tubule + 2 terminal cisterns = triadin relaxed muscle fiber SR stores
Ca++release of Ca++ triggers contraction
Terms for Muscle Fiber Organelles
3 kinds proteins in myofibrils:1. contractile proteins
myosin make up thick filaments, golf-club shape (myosin head)
actin thin filaments
2. regulatory proteins tropomyosin & troponin: both in thin
filaments
3. structural proteins ~12 different ones function in alignment,
stability, elasticity, & extensibility of myofibrils
Muscle Proteins
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120104/bio_b.swf::Sarcomere%20Shortening
http://www.wiley.com/college/pratt/0471393878/student/animations/actin_myosin/actin_myosin.swf
http://brookscole.cengage.com/chemistry_d/templates/student_resources/shared_resources/animations/muscles/muscles.html
Review to do @ home
http://bcs.whfreeman.com/thelifewire/content/chp47/4702001.html
http://www.sumanasinc.com/webcontent/animations/content/muscle.html
https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__breakdown_of_atp_and_cross-bridge_movement_during_muscle_contraction.html
Muscle Contraction Animations
1. ATP hydrolysis ATP attached to myosin head
2. attachment of myosin head to actin to form cross bridges
3. power stroke cross bridges rotate center slides
thin filament past thick filament
4. detachment of myosin from actin ATP binds to myosin head & cross
bridges released
Contraction Cycle Steps
synapse: functional junction between 2 neurons or between a neuron & an effector (muscle or gland); may be electrical or chemical
1st side of synapse: end of axon of motor neuron called synaptic end bulb
then synaptic cleft (the space)lastly, motor end plate: part of
sarcolemma that has receptors for neurotransmitter acetylcholine (ACh)
NMJ
1. release of ACh2. activation of ACh receptors3. production of muscle action
potential4. termination of ACh activity
Steps in Nerve Action Potential Muscle Action Potential
ACh stored in vesicles in synaptic end bulb
action potential travels down axon reaches synaptic end bulb induces exocytosis of neurotransmitter from synaptic vesicles
ACh diffuses across synaptic cleft toward motor end plate
Release of ACh
2 molecules of ACh bind to ACh receptors embedded in sarcolemma opens ion channel allows Na+ diffuse across membrane
Activation of ACh receptors
inflow Na+ makes inside of muscle fiber more + charged
this change in membrane potential triggers a muscle action potential propagates along sarcolemma T tubules
this causes SR to release Ca++ sarcoplasm contraction
Production of Muscle Action Potential
effect of ACh binding short because ACh is rapidly broken down by enzyme acetylcholinesterase (AChE)
Termination of ACh Activity
@ midpoint of muscle fiber:muscle action potential propagate
both ends of fiberallows simultaneous activation & so
contraction of all parts of muscle fiber
NMJ
South American plant derivativecauses paralysis by binding to &
blocking ACh receptors on motor end plates
curare-like drugs used in general anesthesia to relax skeletal muscles
Curare
disease caused by Clostridium botulinum toxin that blocks exocytosis of synaptic vesicles so no ACh released so no muscle contractiontoxin one of most lethal chemicals knowncauses death by paralyzing skeletal
muscles: breathing stops when diaphragm & intercostal muscles stop contracting
Botulism
“equal tension”force of contraction developed by
muscle remains almost constant while muscle changes its length
used for body movements & for moving objects
2 types:1. concentric isotonic contraction2. eccentric isotonic contraction
Isotonic Contractions
when tension generated is enough to overcome resistance of object being moved …muscle shortens & pulls on another structure (tendon) ….producing movement that reduces angle at a joint
Concentric Isotonic Contraction
tension exerted by the muscle resists movement of the load (whatever was lifted up) slowing the lengthening process
Eccentric Isotonic Contraction
tension generated by the muscle is < tension needed to overcome resistance of the object
muscle does not change its length
Isometric Contraction
http://www.youtube.com/watch?v=jKygojJgFQE
Contraction Animations to Try @ Home
same arrangement actin/myosin: striations
muscle fibers branched*intercalated discs: unique to cardiac
muscleautorhymicity alone: 75 bpmremains contracted 10-15 x’s longer than
skeletal muscle after 1 action potentialdue to prolonged delivery of Ca++ (SR +
interstitial fluidlarger & more #s of mitochondria
Cardiac Muscle Tissue
Development of Musclefrom mesodermstarts ~4 wkscardiac muscle
forms tubes bends & folds to form heart
spasm: sudden involuntary contraction of a single muscle is a large group of muscles
Medical Terminology
tic: an involuntary twitching by muscles that are normally under voluntary control
Medical Terminology
tremor: rhythmic, involuntary, purposeless contraction that produces a quivering or shaking movement
Medical Terminology
fasiculation: involuntary, brief twitch that is visible under the skin; occurring irregularly & not ass’c with movementseen in MS or ALS
Medical Terminology
fibrillation: spontaneous contraction of single muscle fiber that is not visible under skin but can be recorded by EMG (electromyograph) signals destruction of motor neurons
Medical Terminology
muscle strain: tearing of muscle due to forceful impact + bleeding +painmost often affect quadraceps femoristx‘d RICE (rest, ice, compression ie a
wrap, elevation)
Medical Terminology