A&P 2.3 - Muscle Tissue Flashcards
Types of Muscle Tissue
List the types of muscle tissue
- Cardiac
- Smooth
- Skeletal
Types of Muscle Tissue
Describe cardiac muscle
- Located in the walls of the heart
- Striated
- Involuntary
Types of Muscle Tissue
Describe smooth muscle tissue
- Located in walls of internal organs and blood vessels (vasoconstriction/dilation)
- Non-striated
**more flexible with when and how they contract
**can move unidirectionally or in waves (peristalsis) - Involuntary
Types of Muscle Tissue
Describe skeletal muscle
- Attached to bones by tendons
- Striated
- Voluntary
Functions of Skeletal Muscle
List the functions of skeletal muscle
- Producing movement
- Maintaining posture
- Stabilizing joints
- Generating heat
Functions of Skeletal Muscle
Describe skeletal ms function of: producing movement
- Skeletal system and skeletal muscles work together acting on a system of levers
** Skeletal ms pulls on bone -> creating movement at or around a joint
Functions of Skeletal Muscle
Describe skeletal ms function of: maintaining posture
- in a constant state of semi-contraction to help in holding skeleton up against gravity
Functions of Skeletal Muscle
Describe skeletal ms function of: stabilizing joints
- skeletal ms surrounds joints -> lends support to ligaments when contracted
Functions of Skeletal Muscle
Describe skeletal ms function of: generating heat
- skeletal ms makes up ~40-50% of body mass
- when contracting, makes up to 80% of body heat (i.e. why we shiver when cold to rapidyl contract => produce heat)
Properties of Skeletal Muscle
List the different properties
- Excitability
- Extensibility
- Contractility
- Elasticity
Properties of Skeletal Muscle
Describe the property of: excitability
- ability to respond to electrical or chemical signal
- all skeletal muscle can do this
Properties of Skeletal Muscle
Describe the property of: contractility
- skeletal muscle displays the ability to shorten up to 60% of its resting length
Properties of Skeletal Muscle
Describe the property of: extensibility
- ability to be stretched beyond resting length
- allows for range of motion
Properties of Skeletal Muscle
Describe the property of: Elasticity
- ability to return to resting length after being stretched
Gross Anatomy of Skeletal Muscle
List the 6 main structures of skeletal muscle
- Muscle fiber
- Fascicle
- Muscle belly
- Tendon
- Aponeurosis
- Musculotendinous (MT) junction
Gross Anatomy of Skeletal Muscle
Describe muscle fibers
- smallest unit
- striated
- multinucleated
- elongated strands of mostly protein
- store myoglobin (stored form of O2) and glycogen (stored form of glucose)
- contain many mitochondria
- may be microscopic or up to 1ft long
- covered in endomysium
AKA muscle cell / myofiber
Gross Anatomy of Skeletal Muscle
Describe the endomysium
CT layer wrapped around/surrounding each muscle cell & continuing into the tendons
Gross Anatomy of Skeletal Muscle
Describe fascicles
a group of muscle cells wrapped in CT
Gross Anatomy of Skeletal Muscle
Describe perimysium
CT covering wrapped around a fascicle
Gross Anatomy of Skeletal Muscle
Describe the muscle belly
a group of fascicles
Gross Anatomy of Skeletal Muscle
Describe the epimysium
CT covering wrapped around a muscle belly
Gross Anatomy of Skeletal Muscle
Describe a tendon
- dense, irregularly arranged CT that attaches ms-bone
- endomysium, perimysium, and epimysium all join to form a strong attachment of ms-bone
Gross Anatomy of Skeletal Muscle
Describe aponeurosis
Broad, sheet-like tendon attaching ms-ms, ms-bone, ms-skin
Gross Anatomy of Skeletal Muscle
Describe MT junction
” Musculotendinous junction”
- where muscle meets tendon
- weakest point of a muscle
Action Potential & nerve Stimulus of Skeletal Muscle
List the structures involved
- Motor unit
- Axon
- Axon terminal
- Neuromuscular junction
- Synaptic cleft
- Neurotransmitter
- Motor end plate
- Action potential
Action Potential & nerve Stimulus of Skeletal Muscle
Motor unit
a motor neuron and all muscle fibers it supplies
Action Potential & nerve Stimulus of Skeletal Muscle
Axon
an extension off of a motor unit which carries action potential to muscle cell
Action Potential & nerve Stimulus of Skeletal Muscle
Axon terminal
terminal end of axon which carries electrical energy to muscle cell
AKA synaptic knob
Action Potential & nerve Stimulus of Skeletal Muscle
Neuromusclar junction
Union of nervous & muscular systems
Action Potential & nerve Stimulus of Skeletal Muscle
Synaptic Cleft
microscopic space between axon terminal and muscle cell where neurotransmitters are released
Action Potential & nerve Stimulus of Skeletal Muscle
Neuortransmitter
Chemical released into synaptic cleft which allows for perpetuation of electrial energy to muscle cell
(Acetylcholine)
Action Potential & nerve Stimulus of Skeletal Muscle
Motor End Plate
region of sarcolemma where axon terminal comes in close contact
- Has receptor sites for neurotransmitters
Action Potential & nerve Stimulus of Skeletal Muscle
Action Potential
A rapid change in electrical signal that transmits current to an effector cell
Microscopic Anatomy of Muscle Cell
List the different structures involved
- Sarcoelmma
- Sarcoplasm
- Myofibrils
- Z disc/line
- Sarcomere
- Actin
- Blocking proteins
- Binding sites on actin
- Myosin
- Myosin cross bridges
- Sarcomplasmic reticulum
- T-tubules
- Elastic filaments
Microscopic Anatomy of Muscle Cell
Sarcolemma
- Plasma membrane of muscle cell
- Deep to endomysium
“sarco” = flesh
Microscopic Anatomy of Muscle Cell
Sarcoplasm
Cytoplasm of muscle cell
Large amounts of glycogen, myoglobin & mitochondria doe tu muscle needs
Microscopic Anatomy of Muscle Cell
Myofibrils
- Rod-like protein structures which extend the loength of the muscle cell
- Make up 80% of muscle cell volume
- Chains of sarcomeres line up end to end
Microscopic Anatomy of Muscle Cell
Z disc/line
Coin shaped disc of protein which anchors thick and thin filaments => connecting adjacent sarcomeres
Microscopic Anatomy of Muscle Cell
Sarcomere
- smallest unit of contractile region
- Contains a collection of actin and myosin
- Sarcomeres lined up end to end to form myofibrils
- ” z-disc to z-disc”
Microscopic Anatomy of Muscle Cell
Actin
- “thin filaments”
- Made of protein actin
- Anchors to z-disc and extends into venter of sarcomere
Microscopic Anatomy of Muscle Cell
Blocking Proteins
- Present on actin filaments
- Block binding sites on actin filaments to prevent myosin from binding
- Change shape in presence of calcium to allow binding
Microscopic Anatomy of Muscle Cell
Binding sites on actin
- Allow myosin to attach
- When blocking proteins change shape in presence of calcium, these are uncovered
Microscopic Anatomy of Muscle Cell
Myosin
- “thick filaments”
- Made of protein myosin
- Cenetered in sarcomere
- Attached to z-disc by elastic fibers
Microscopic Anatomy of Muscle Cell
Myosin Cross Bridges
- Paddle-like extensions on myosin fiers which attach to binding sites on actin => creating a “power stroke”
Microscopic Anatomy of Muscle Cell
Sarcoplasmic Reticulum
- Sleeve-like arrangement of tubes surrounding myofibrils
- store calcium that’s released for muscle contraction
Microscopic Anatomy of Muscle Cell
T-tubules
- Inward extension of sarcolemma which serve to carry action potential into cell
- filled w/ extracellular fluid
Microscopic Anatomy of Muscle Cell
Elastic Filaments
- made of protein titin
- anchor actin and myosin filaments to z-disc and allow for sarcomere to return to normal resting length after being stretched
Skeletal Muscle Contraction
List the step-by-step process
- Action potential (AP) transmitted along the neuron’s axon to axon temrinal (synaptic knob) -> stimulates release of ACh neurotransmitter into synaptic cleft
- ACh binds with receptor sites on motor end plate -> Na+ channels open and Na+ floods into cell which has a more negative charge => initiates AP to run length of sarcolemma until it reaches T-tubules
- AP travels down T-tubules to reach sarcoplasmic reticulum (SR) => stimulates Ca channels to open
- Calcium ions bind to blocking proteins on actin filament -> blocking proteins change shape => expose binding sites for myosin cross bridges
- Myosin cross bridges attach to actin binding sites -> pull actin filaments toward center of sarcomere => muscle contract (“power stroke”)
- Meanwhile, ACh is being removed from synaptic cleft => stops AP
- Calcium is transported from sarcoplasm back to SR
- Blocking proteins return to cover crossbridge binding sites so that myosin can no longer attach and actin releases back to resting position (sarcomere lengthens and muscle relaxes)
- ATP provides energy for this mechanism to occur
