chapter 9 Muscular system
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Name the three types of muscle tissue?
What is the definition of skeletal muscle tissue?
Pulls on bones
Define smooth muscle tissue?
- Pushes fluids, & solids
Define cardic muscle tissue?
Name the four characteristics of all muscle tissue?
What is contractibilty?
What is purpose of excitability?
Respond to a stimulus
What is the purpose of extensibility?
- Extend beyond its original
- Lenght & still contract
What is the purpose of elasticity?
Rebound to its original length
How many skeletal muscles are there?
Each muscle is what type of tissue?
What type of muscles are skeletal?
Name the functions of skeletal muscles?
- Produce skeletal movement by pulling on muscles
- Maintain body posture, tension continual in some muscles
- Support soft tissue, abdominal wall
- Guard orifices, voluntary control over swallowing, defection, urination
- Heat production, homeostasis (body temp.)
Define muscle fiber?
A long cylindrical "cell"
How long are huge fused "cells"?
Name the three connective tissue wrappings of the skeletal muscles?
What are muscle fibers arranged into?
Where is endomysium?
Around single muscle fiber
Where is perimysium?
Around a fascicle (bundle) of fibers
Where is epimysium found?
Covers the entire skeletal muscle.
What function does the epimysium serve? What is it made of?
- Dense irregular tissue
- Blood vessels & nerves
- Epimysium continous with tendon
What is the funciton of perimysium? What is it made of?
- Divides muscle into compartments called fascicles
- Blood vessels & nerves; collagen &
- Elastic fibers
What is the function of the endomysium? What is it made of?
- Surrounds each muscle fiber (fused cells)
- Delicate network with capillaries;
- Recticular fibers
- Myosatellite cells
What is aponeuroses?
Flat broad tendons
What are characteristics of connective tissue sheaths?
- Endomysium and perimysium are interwoven
- All sheaths continous with muscle tendon &
- Aponeuroses. Take force of contraction
- To bone, muscle or skin
What is muscle fiber? Name some characteristics.
- Muscle fiber is formed during development
- From the fusion of several undifferentiated
- Immature cells known as myoblasts into long,
- Cylindrical, multi-nucleanated cells.
What are myofibrils?
- Cylindrical organelles found within
- Muscle cells
What is the sarcolemma?
- Plasma membrane of a muscle cell
- Invaginates into the cytoplasm of the muscle cell,
- Forming membranous tubules called
- Transverse tubules (T-tubules).
What is the scaroplasma? What does it contain?
- The cytoplasm of the muscle cell
- Myofibrils with myofilaments (protein fibers)
- Multinucleated (pushed to cell membrane)
- Mitochondria (more than any other cells of the body)
What is the sarcoplasmic reticulum? Where is it located? What else about it is important?
- Corresponds to smooth endoplasmic reticulum
- Sits as a sleeve around myofibrils
- Has terminal cisternae which holds
- And releases Ca++ ions
What fills the myofibril?
Beginning with skeletal muscle what is the are next layers contained?
- Skeletal muscle contains muscle fascicle
- Muscle fascicle contains muscle fibers
- Muscle fiber contains myofibrils
- Myofibrils surrounded by sarcoplasmic
- Reticulum consits of sacromeres
- Contains thin and thick filaments
What is actin?
Thin strands of protein
What is myosin?
Thick filaments of protein
- Bundle of thin and thick filaments
- Repeating units formed of actin
- And myosin
Which area of the muscle cell does the actual contracting?
- Contracts to 1/3 of
How many sacromeres/myofibrils are there?
10,000 linearly arranged
On a microscopic slide of muscle what is indicated by the light and dark bands?
- Zones of actin
- & Myosin overlap
What is the length of a relaxed sacromere?
What is muscle contraction?
- Muscle fiber shorten in length (exerts a pull)
- Result of interatcions between action &
- Myosin filaments
- (Sliding filament theory)
What has been observed about the sliding filament theory (of muscle contraction)?
- The H band & I band
- Get smaller the Z lines
- Get closer together
When we use the word bands to describe the lines of myosin and actin filaments what is meant? Why?
- They are actually discs
- As the structure is cylindrical
Describe the sliding filament theory.
- Myosin heads attache to actin & pull
- It toward the M line myosin head is
- The crossbridge myosin head binds,
- Pulls, detaches, re-sets, repeats
- Sarcomere shortens
When muscles contract what is the ration of myosin to actin?
3 myosin to 1 actin filament
What is tropomyosin molecules?
- An actin binding protein that forms
- A long chain that covers the active sites
- Preventing actin-myosin interaction
What is function of troponin?
Holds the tropomyosin in place
What does sarkos mean?
What does lemma mean?
What happens in the zone of over lap?
- The thin filaments pass between
- The thick filaments
What is the triad area?
- Combination of the terminal cisternae
- & trasverse tubules
What does the A band contain?
Area containing thick filaments
What is region from the Z line to the A band?
- I band
- Which contains thin filaments
What does the amount of tension depend on?
- Number of cross bridge
- Interactions that occur
- In the sarcomeres
- Individual structure
When does contraction stop?
- When Ca++ are returned &
- Stored in sacroplasmic reticulum
- Uses ATP
What does myosin need to detach from actin during contraction? What position does it return to?
- Require ATP and returns
- To "cocked" position
Define Rigor Mortis
- Circulation ceases with death
- Skeletal muscles can not produce ATP without oxygen
- Fiber can not recapture Ca++ to SR, contraction continues
- No ATP to release myosin head from actin filament
- Muscle locks in contracted position
- "stiff as a board" lasts 15-20 hrs.
- Tell time of death
What is each muscle controlled by?
A motor neuron
What is each muslce fiber controlled by?
A motor neuron
Where can a motor neuron's cell body by found?
In the spinal cord
What do a motor neuron and muscle fiber make up?
What is the axon? Where is it located?
- Long process of the motor neuron
- Extends to the fiber
What is the motor end plate and synaptic terminal separated by?
What is the synaptic terminal?
- The expanded tip of the axon
- At the neuromuscular synapse
Where is the ACh (acetylcholine) released?
- At the synaptic terminal
- Of the nerve
What is the action potential?
- An electrical impulse (excitibilty) that sweeps over
- The suface of the sarcolemma
- & into each T tubule
What generates the action potential?
- ACh is released into the synaptic cleft
- The ACh released then binds to receptor sites
- On the motor end plate, initiating a change in the
- Local transmembrane potential.
What is the result of the action potential?
What enzyme breaks down the ACh molecules?
Define the motor unit?
- All of the muslce fibers
- Controlled by a single motor neuron
Where are small motor units found? What is there function?
- Found in fingers
- For fine control
What is fine control defined as?
- Fewer fibers controlled by one
What does all or nothing mean?
- Each fiber contracts completely
- Or not at all
What does the amount of tension depend on?
- Frequency of stimulation
- Number of motor units involved
What gives the precise control of muscle tension?
Define muscle twitch?
A single momentary contraction
How is the amount of force determined?
- Depends of how many motor units
- Are activated (recruitment)
Within a muscle are bundles of muscle fibers called what?
How do muscle fibers arrange themselves within the fascicle?
They lie paralle to one another
What are the four basic types of fascicle arrangements? What do they affect?
- Power, range, & speed
What is defined as a parallel muscle?
- Fibers run the length of the muscle
- (maximum shortening 1/3 of length)
What type of muscle are most muscles in the body?
What is the shape of parallel muscles?
Strap-like or spindle shaped
Define convergent muscles?
- Muscles having a broad origin;
- Fibers converge on a single insertion from
- Multiple directions
What is the shape of convergent muscles?
Triangle or fan-shaped
Define versatile? What muscle type is versatile?
- Direction of pull can be changed
Define pennate muscles.
- Short fibers attach at oblique angles to a central
What muscle types are the most powerful & have more tension?
What is unipennate?
All fibers on the same side of the tendon
What is bipennate?
Muscle fibers on both sides of the tendon
What is multipennate?
Tendon branches within the muscle
Define circular muscles?
- Concentric rings around external body openings
- Usually sphincters or valves
What do circular muscles guard?
Entrances/exits by contracting
What is the minimum of points that every skeletal muscle is attached to bone or connective tissue?
- Two points
- If it's from bone-bone
- Always crosses articulation
Where is the muscles origin attached to?
To the immovable bone
Where does a muscle begin?
At an origin
Where does a muscle end?
At the insertion
Where is the insertion attached to?
The movable bone
How does action occur?
As the insertion moves towards its origin
Name the three primary actions?
- Prime movers (Agonists)
Define Agonists? Give examples.
- Cheifly responsible for producing a
- Particular movement
- Flexion at the elbow
- Contracts, it assists the prime mover in
- Performing that action
- Provide additonal pull near the insertion
- Or stabilize the point of origin
Give an example of a synergist.
- Latissimus dorsi assisted by
- Teres major pull the arm inferiorly
Define antagonist? Give example.
- Oppose the action of the agonist (prime mover)
- If the agonist produces flexion, the antagonist
- Will produce extension
What are fixators?
- Synergists that assist an agonist by preventing
- Movement at a joint and thereby stablizing
- The origin of the agonist.
What is idea behind the principal of levers?
- Skeletal muscles do not work in isolation
- Muscles working with bone
- Simple machines make it easier to do work (with bone)
Name the simple machines?
Define lever? Name the parts of the body that correspond to lever system.
- A rigid bar (bones) that moves on a fulcrum (joint)
- (Fixed point) when a force (effort) (muscle contraction)
- Is applied to it to move a resistance (load)
What is the first class lever? Give example.
- See saw
- They are rare in the body
- Occipital condyle & C1
What is the second class lever? Give example
- Wheel barrow
- Force is magnified
- Resistance covers a shorter distance & is slower
- Plantar flexion
How common are the third class levers in the body? Name the characteristic of this type. Give examples
- Most skeletal muscle of the body
- Speed and distance increased at the expense of force
- Biceps brachii
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