Chapter 6 Flashcards
Basic muscle types found in body
Skeletal
Cardiac
Smooth
Which muscle cells are elongated?
Skeletal and smooth
Muscle cell is AKA
Muscle fiber
What causes the contraction and shortening of muscle?
Movement of microfilaments
Myo-
Muscle
Mys-
Muscle
Sarco-
Flesh
Only consciously controlled muscle
Skeletal muscle
Most skeletal muscles are attached by ___ to bones
Tendons
Large, cigar shaped, stritrated, multinucleate
Skeletal muscle
Speed of contraction of skeletal muscles
Slow to fast
Speed of contraction of cardiac muscle
Slow
Speed of contraction of smooth muscle
Very slow
What controls cardiac muscle contractions?
Involuntary, pacemaker, nervous system, hormones
What controls smooth muscle contractions?
Involuntary, nervous system, hormones, chemicals, stretch
Rhythmic contractions (skeletal)?
No
Rhythmic contractions (cardiac)?
Yes
Rhythmic contractions (smooth)?
Yes, in some
Endomysium
Encloses single muscle fiber
Perimysium
Wraps around bundle of muscle fibers
Fascicle
Bundle of muscle fibers
Epimysium
Covers entire skeletal muscle
Fascia
Outside of epimysium
Epimysium blends into connective tissue attachments which are
Tendons
Aponeuroses
Tendon
Cord-like
Mostly collagen
Cross joints
Tough and small
Aponeuroses
Sheet like
Attach muscles indirectly to bone, cartilage or connective tissue coverings
Smooth muscle
No striations
Found in hollow organs
Uninucliate
Cardiac muscle
Striations
Only walls of heart.
Uninucliate
Intercalated discs
Additional roles of skeletal muscle
Maintain muscle and body position
Stabilize joints
Generate heat
Sarcolemma
Surround muscle fibers
Special plasma membrane
Myofibrils
Myofibrils
Long organelles in muscle cell
Has light and dark bands
I Bands
Light bands
only thin filaments
Z disc is midline interruption
A Bands
Dark bands
Entire length of thick filaments
H zone is a lighter central area
M Line is in center of H zone
Actin
Thin myofilament
Myosin
Thick myofilament
Structural and functional unit of skeletal muscle
Sarcomere
Sarcomere
Contractile unit of a muscle fiber
Parts of sarcomere
Myosin and actin
Which filaments have ATPase?
Myosin filaments aka thick filaments
Myosin heads
Projections
Cross bridges
Link thick and thin filaments during contraction
Actin is anchored to
Z DISC
Which zone in the A band lacks actin filaments at rest?
H zone
What happens to H zones during contraction?
They disappear because actin and myosin overlap
____area between two neighboring Z discs
Sarcomere
Sarcoplasmic reticulum
Special smooth ER
Surrounds myofibril
Stores and releases calcium
Functional properties of skeletal muscles
Irritability
Contractility
Extensibility
Elasticity
Irritability
Receiving and responding to stimuli
Contractility
Ability to forcibly shorten
Extensibility
Ability to stretch
Elasticity
Ability to resume resting length after stretching
Skeletal muscles must be stimulated by a _____ ____ to contract
Motor neuron
Nerve cell
Motor unit
One motor neuron + all muscle cells stimulated by that neuron
Neuromuscular junction
Associates axon terminal of motor neuron and sarcolemma of a muscle
Neurotransmitter
Chemical
Released when nerve impulse gets to axon terminal
Acetylcholine (ACh)
Neurotransmitter
Stimulates skeletal muscle
Synaptic cleft
Gap between nerve and muscle
Filled with interstitial fluid
Nerve and muscle don’t make eye contact
What happens when a nerve impulse reaches the axon terminal of the motor neuron step 1
- Calcium channels open, calcium ions enter axon terminal
What happens when a nerve impulse reaches the axon terminal of the motor neuron step 2
- Acetylcholine is released because calcium ions entering causes the synaptic vesicles to release ACh
What happens when a nerve impulse reaches the axon terminal of the motor neuron step 3
- ACh diffuses across synaptic cleft and attaches to receptors on the sarcolemma of the muscle cell
What happens when a nerve impulse reaches the axon terminal of the motor neuron step 4
- If enough ACh is released, sarcolemma becomes temporarily more permeable to sodium ions.
What happens after sarcolemma is more permeable to Na+ ?
- Potassium diffuses out
- More Na+ enters than potassium ions leave
- Establishes imbalance where interior has more positive ions (depolarization) opening more Na+ channels
Depolarization
Shift in electric charge distribution
Inside has more positive ions
step 5: depolarization opens more Na channels that let sodium ions enter the cell
Action potential is created
Action potential is unstoppable once created
Conducts electrical impulses from one end of the cell to the other
AChE
Acetylcholinesterase
Step 6: AChE breaks down ACh into acetic acid and choline
AChE ends muscle contraction
Single nerve impulse produces only one contraction
Cells return to resting state when
- K+ diffuses out of cell
- NaK pump moves Na and K ions back to original position
(Higher Na+ outside)
Action potentials
Nerve impulses
What causes filaments to slide step 1.
Ca2+ binds regulatory proteins on thin filaments and exposes myosin binding sites allowing myosin heads on thick filaments to attach
What causes filaments to slide step 2.
Each cross bridge pivots
Making thin filaments slide toward center of the sarcomere
What causes filaments to slide step 3
Contraction occurs and cell shortens
What causes filaments to slide step 4.
During a contraction, cross bridge attaches and detaches several times
What causes filaments to slide step 5.
ATP provides the energy for sliding process which continues as long as calcium ions are present
In relaxed muscle fiber, regulatory proteins making actin myofilaments prevent
myosin binding
When AP (action potential) excited muscle fiber _____ ions are released from intracellular storage areas. (Sacs of sarcoplasmic reticulum).
Ca2+
Flood of Calcium acts as final trigger for
Contraction
As calcium binds to regulators on actin, proteins undergo change in their
Shape and position
Change in actin proteins exposes
Myosin binding sites on actin
Myosin heads can attach to
Myosin binding sites.
Heads immediately seek out binding sites
Free myosin heads are
Cocked like oars ready to be pulled for rowing
Myosin attachment to actin causes myosin heads to pivot towards
Center of sarcomere in a rowing motion
When heads “row” towards center, thin filaments are
Slightly pulled towards center of sarcomere
_____ provides energy needed to release and recock each myosin head so that it is ready to attach to a binding site farther along the thin filament
ATP
Graded responses
Different degrees of skeletal muscle shortening
Different combinations of muscle fiber contractions may give
Differing responses
Within whole skeletal muscle not all fibers may be stimulated during the same
Interval
Muscle fiber contraction is “all or none” meaning it will
Contract to it’s fullest when stimulated adequately
How are graded responses produced
Changing frequency of stim
Changing number of muscle cells being stimmed at once
Muscle twitch
Single, brief, jerky contraction
Not normal muscle function
Stress, caffeine, excercise
Muscle twitch common in
Eyelids
Calves
Thumb
Nervous tics are aka
Muscle twitches
Summed contractions
One contraction immediately followed by another
Most types of muscle activities, impulses delivered at ____ rate
Rapid
When stimulations become more frequent, muscle contractions get ____& ____
Stronger and smoother
Causing muscle to exhibit unfused (incomplete) tetanus
Complete tetanus
Achieved when muscle stimmed so rapidly that no evidence of relaxation is seen
How are contractions in complete tetanus (fused)
Smooth and sustained
Muscle force depends on
of fibers stimulated
Contraction of more fibers results in
Greater muscle tension
When all motor units are active and stimulated, the muscle contraction is
As strong as it can get
Only energy source that can be used to directly power muscle contraction
ATP
What is stored in muscle fibers in small amounts that is quickly used up?
ATP
Pathways to make ATP
- Direct ADP phosphorylation
- Aerobic pathway
- Anaerobic glycolysis and lactic acid formation
Fastest way to regenerate ATP
Direct phosphorylation by creatine phosphate (CP)
Explain CP direct phosphorylation
- Muscle cells store CP
- After ATP is depleted, ADP remains
- CP transfers phosphate to ADP
CP supplies exhausted in less than ___ seconds
15
ATP produced per CP molecule
1
Supplies ATP at rest and during light/moderate excercise
Aerobic respiration
Explain aerobic respiration
1.Oxidative phosphorylation happens in mitochondria
- Glucose broken down to CO2 and water releasing 32 ATP approx
- Slower. Requires continuous O2 and nutrients
Explain anaerobic glycolysis
- Gluc. broken to pyruvic acid to make about 2 ATP
- Pyruvic into lactic acid, causes muscle soreness
Which ATP process is fast but inefficient ?
Anaerobic glycolysis
Which ATP process requires huge amounts of glucose
Anaerobic glycolysis
When does muscle fatigue occur?
Strenuous and prolonged muscle activity
Suspected factors that contribute to muscle fatigue
1.Ca2+, K+ muscle imbalances
- O2 deficits & lactic acid accumulation
- Decrease in ATP supply
O2 deficit repaid by
Rapid, deep breathing
Isotonic contractions
1.Myofilaments slide past each other during contractions
2.Muscle shortens and movement occurs
Examples of isotonic contractions
Bending knee; lifting weights, smiling
Isometric contractions
Muscle filaments try to slide, but muscle is against immovable object
Tension increases, muscles don’t shorten
Example of isometric contractions
Pushing palms together in front of you
Muscle tone
Continuous partial contractions
Muscle remains firm, healthy and constantly ready for action
Result of different motor units stimulated in a systematic way
Muscle tone
What does excercise do to the body?
Increases muscle size, strength and endurance
Aerobic (endurance) effect
Stronger, more flexible muscles w/ greater resistance to fatigue
What do aerobics improve?
metabolism, digestion, coordination
Isometric excercise (resistance) (weight lifting)
Increases muscle size and strength
Muscle fibers enlarge
