Chapter Nine: Muscular System Flashcards
What kind of Muscle Tissue?
- Responsible for locomotion, facial expressions, posture respiratory movements, other types of body movement
- voluntary
Skeletal Muscle Tissue
What kind of Muscle Tissue?
- walls of hollow organs, blood vessels, eye, glands, skin
- some functions: propel using, mix food in digestive tract, dilating/constricting pupils, regulating blood flow
- controlled involuntarily by endocrine and autonomic nervous systems
- autorhythmic in some locations
Smooth Muscle Tissue
What kind of Muscle Tissue?
- heart: major source of movement of blood
- authorhythmic
- controlled involuntarily by endocrine and autonomic nervous systems
Cardiac Muscle Tissue
What are the seven functions of the Muscular System?
- Movement of the body
- Maintenance of posture
- Respiration
- Production of body heat
- Communication
- Constriction of organs and vessels
- Contraction of the heart
Ability of a muscle to shorten with force
Contractility
Capacity of muscle to respond to an electrical stimulus (from our nerves)
Excitability
Muscle can be stretched beyond its normal resting length and still be able to contract
Extensibility
Ability of muscle to recoil to original resting length after stretched
Elasticity
____________ Muscle Anatomy
- composed of muscle cells (fibers), connective tissue, blood vessels, nerves
- fibers are long, cylindrical, multinucleated
- striated appearance due to light and dark banding
Skeletal
What is the layer of connective tissue that surrounds a whole muscle?
Epimysium
What is the layer of connective tissue that surrounds a group of muscle fibers?
Perimysium
Each group of muscle fibers is called a…
fascicle
What is the layer of loose connective tissue with reticular fibers?
Endomysium
The connective tissue sheet is also known as the…
Muscular Fascia
The Muscular fascia goes from external to epimysium and holds muscles together as well as separates them into…
Functional Groups
Motor neurons stimulate muscle fibers to…
Contract
Motor neurons: nerve cells with cell bodies in brain or spinal cord; ________ extend to skeletal muscle fibers through nerves
Axons
Axons branch so that each muscle fiber is…
Innervated
Motor neurons: contact is __________________ junction
Neuromuscular Junction
Skeletal Muscle Fiber Anatomy: several nuclei just inside…
Sarcolemma
Invaginations that connect extracellular environment to interior of muscle fibers
Transverse Tubules (T-tubules)
Skeletal Muscle Fiber cells are packed with _________ within cytoplasm (sarcoplasm)
Myofibrils
Myofibrils are composed of myofilaments: thin filaments (_________) and thick filaments (____________)
actin
myosin
Highly ordered repeating units of myofilaments in skeletal muscle fiber
Sarcomeres
Calcium regulation and storage within skeletal muscle fibers
Sarcoplasmic Reticulum
Actin (thin) Myofilaments:
Two strands of _______ actin form a double helix extending the length of the myofilament; attached at either end of the sarcomere to the Z disc
fibrous actin
Actin (thin) Myofilaments:
Composed of G (__________) actin monomers, each of which has an active site
globular
Actin (thin) Myofilaments:
Active site can binds ________ during muscle contraction
myosin
an elongated protein winds along the groove of the F actin double helix
Tropomyosin
Troponin has three subunits, each subunit binds to one of these three…
- Actin
- Tropomyosin
- Calcium Ions
Troponin holds tropomyosin over the active sites on…
actin
The tropomyosin/troponin complex regulates the interaction between what two things?
Actin and Myosin
Myosin (thick) Myofilament:
Many elongated ____________ molecules shaped like golf clubs
myosin
Myosin (thick) Myofilament:
Molecule consists of myosin heavy chains wound together to form a ______ portion lying parallel to the myosin filament and _______ heads that extend laterally
rod
two
Myosin heads can bind to active sites on the actin molecules to form…
cross-bridges
Myosin heads are attached to the _____ portion by a hinge region that can bend and straighten during contraction
rod
Myosin heads are ATPase enzymes: break down _____, releasing energy
adenosine triphosphate (ATP)
Basic functional unit of muscle fiber
Sarcomere
Filamentous network of protein; serves as attachment for actin myofilaments
Z disk
Elastic chains of amino acids; make muscles extensible and elastic
Titin filaments
What four things create the striated appearance in Sarcomeres?
- I Bands
- A bands
- H zone
- M. Line
Sarcomeres Striated Appearance:
form Z disks to ends of thick filaments
I bands
Sarcomeres Striated Appearance:
length of thick filaments
A bands
Sarcomeres Striated Appearance:
region in A band where acting and myosin do not overlap
H zone
Sarcomeres Striated Appearance:
middle of H zone; delicate filaments holding myosin in place
M line
Sliding Filament Model:
actin myofilaments sliding over myosin to shorten…
sarcomeres
Sliding Filament Model:
what two things do not change the length?
actin and myosin
Sliding filament model:
shortening sarcomeres responsible for skeletal muscle…
contraction
During relaxation, ______________ lengthen because of some external force, like contraction of antagonistic muscles
sarcomeres
Muscles that produce the opposite effect of lengthening during relaxation due to external force
Antagonistic muscles
axon terminal resting in an invagination of the sarcolemma
Synapse
What are the three parts of a neuromuscular junction?
- Presynaptic Terminal
- Synaptic Cleft
- Postsynaptic Membrane
What part of the neuromuscular junction?
- axon terminal with synaptic vesicles
- synaptic vesicles contain neurotransmitters
Presynaptic terminal
What part of the neuromuscular junction?
- space
Synaptic cleft
What part of the neuromuscular junction?
- sarcolemma of the muscle cell
Postsynaptic membrane
What are the four parts of the “Big Picture”
- Action Potential in Neuron
- Stimulation of muscle fiber at the Neuromuscular Junction
- Action Potential in Muscle
- Sarcomere Contraction via Cross-Bridge Movement
All excitable cells are…
polarized
Polarized cells possess a difference in _________ between inside and outside
charge
Charge difference between inside and outside of the cell is known as a…
Membrane Potential
Nervous system controls muscle contractions through…
action potentials
Resting Membrane Potentials:
Membrane voltage difference across membranes (_________)
polarized
Resting Membrane Potentials:
Inside cell is more ___________ due to accumulation of large protein molecules
negative
Resting Membrane Potentials:
More ______ on inside than outside
K+
Resting Membrane Potentials:
______ leaks out but not completely because negative proteins hold some back
K+
Resting Membrane Potentials:
Outside of cell is more positive and more ______ on outside of the cell than the inside of the cell
Na+
What two kinds of pumps maintains resting membrane potentials?
Na+ and K+ pumps
What type of ion channel?
- gate is closed until neurotransmitter attaches to receptor molecule
- EX: neurotransmitters
Ligand-gated
molecules that bind to receptors
Ligands
Protein or Glycoprotein with a receptor site
Receptor
What type of ion channel?
- open and close in response to small voltage changes across plasma membrane
Voltage-gated
What inside the plasma membrane is higher than that outside the plasma membrane?
K+
What outside the plasma membrane is higher than that inside the plasma membrane
Na+
Plasma membrane is more permeable to what?
K+
More leaky ____ channels than leaky Na+ channels, so ____ diffuses out of the cell -> inside becomes even more negative
K+
________ __________ of Na+ and K+ maintains the uneven distribution of Na+ and K+ across plasma membrane
Active Transport
What are the six steps of action potential?
- Excitation
- Ion channels open
- change in membrane permeability
- ions diffuse through channels
- change in charge across plasma membrane
- action potential
What are the two phases of action potential?
Depolarization and Repolarization
What phase of action potential?
- inside of plasma membrane becomes less negative
- if change reaches threshold, depolarization occurs
Depolarization
What phase of action potential?
- return to resting membrane potential
Repolarization
What principle?
- if threshold is reached, a full action potential is generated; if not, no signal is produced?
All-or-none principle
What part of action potentials?
- spread from one location to another
- action potentials does not move along the membrane: new action potentials at each successive location
Propagate
What part of Synaptic vesicles?
- substance released from a presynaptic membrane that diffuses across the synaptic cleft and stimulates (or inhibits) the production of an action potential in the postsynaptic membrane
- EX: Acetylcholine
Neurotransmitter
What part of Synaptic vesicles?
- a degrading enzyme in synaptic cleft that prevents accumulation of ACh
Acetylcholinesterase
The first function of neuromuscular junction:
Action potential arrives and opens voltage-gated _______ channels
Ca2+
The second function of neuromuscular junction:
Ca2+ initiates release of ___________ __________
synaptic vesicles
The third function of neuromuscular junction:
______ released into synapse
Ach
The fourth function of neuromuscular junction:
Ach opens ligand-gated _______ channels
Na+
The fifth function of neuromuscular junction:
Na+ enters cell —> depolarization —> ____________ _____________
action potential
The sixth function of neuromuscular junction:
Ach detaches and NA+ channels…
close
The seventh function of neuromuscular junction:
Acetylcholinesterase breaks down…
Ach
The eighth function of neuromuscular junction:
___________ transported to presynaptic terminal
Choline
The ninth function of neuromuscular junction:
Ach is reformed from recycled choline and packaged into…
synaptic vesicles
What disease of the neuromuscular junction?
- muscles contract and cannot relax
- can be caused by poisons that inhibit acetylcholinesterase
Spastic Paralysis
What disease of the neuromuscular junction?
- caused when Ach cannot bind to receptors
- muscle is incapable of contracting
- EX: Myasthenia Gravis
Flaccid Paralysis
Mechanism where an action potential causes muscle fiber contraction
Excitation-Contraction Coupling
Excitation-Contraction Coupling involves what seven things?
- Sarcolemma
- Transverse (T) tubules
- Terminal Cisternae
- Sarcoplasmic Reticulum
- Triads
- Ca2+
- Troponin
invaginations of sarcolemma
Transverse (T) tubules
sarcoplasmic reticulum near T tubule
Terminal Cisternae
What part of excitation-contraction coupling goes with the smooth ER?
Sarcoplasmic Reticulum
What part of excitation-contraction coupling is T tubule, two adjacent terminal cisternae
Triad
Action potential produces at the ______________ ____________ is propagates along sarcolemma (including T tubules)
neuromuscular junction
Depolarization of ____ ___________ opens voltage-gated Calcium channels in sarcoplasmic reticulum and Ca2+ diffuses into sarcoplasm
T tubule
Calcium ions bind to _______ —> ________ molecules bound to actin are released —> tropomyosin is moved —> active sites on actin are exposed
troponin
_______ ________ bind to exposed active sites on actin to form cross bridges
Myosin heads
Muscle Relaxation:
Ca2+ moves back into the __________ _________ by active transport (requires energy)
sarcoplasmic reticulum
Muscle Relaxation:
_________ moves away from troponin-tropomyosin complex
Ca2+
Muscle relaxation:
complex re-establishes its position and blocks…
binding sites
Muscle _________
- muscle contraction in response to a stimulus that causes an action potential in one or more muscle fibers
Muscle Twitch
What are the three phases of a muscle twitch?
- Lag/latent
- Contraction
- Relaxation
a single motor neuron and all muscle fibers innervated by it
Motor Units
Large muscles have motor units with _________ muscle fibers
many
Small muscles that make delicate movements contain motor units with _____ muscle fibers
few
what law for muscle fibers?
- individual muscle fibers contract with equal force in response to each action potential
All-or-none
What stimulus?
- no action potential; no contraction
Sub-threshold stimulus
What stimulus?
- action potential; contraction
Threshold stimulus
What threshold?
- action potential; contraction equal to that with threshold stimulus
Stronger than threshold
Strength of whole muscle contraction is graded: ranges from ________ to _________ depending on stimulus strength
weak to strong
strength of contraction depends upon recruitment of motor units
Multiple Motor Unit Summation
What kind of stimuli?
- increasing number of motor units responding
Submaximal Stimuli
What kind of stimuli?
- all motor units respond
Maximal Stimulus
What kind of stimuli?
- all motor units respond; same as maximal stimulus
Supramaximal Stimuli
Trapped is a ________ response
graded
Treppe occurs in muscle ___________for prolonged period
rested
Each subsequent contraction is __________ than previous until all equal after few stimuli
stronger
More and more Ca2+ remains in ____________ and is not all taken up into the sarcoplasmic reticulum
Sarcoplasm
As the frequency of action potentials increase, the frequency of contraction…
increases
What kind of tetanus?
- muscle fibers partially relax between contraction
Incomplete Tetanus
What kind of tetanus?
- no relaxation between contractions
Complete Tetanus
What kind of summation?
- muscle tension increases as contraction frequencies increase
Multiple-wave summation
force applied to an object to be lifted when a muscle contracts
Active Tension
what kind of muscle with active tension: not enough cross-bridging
stretched muscle
what kind of muscle with active tension: myofilaments crumpled, cross-bridges can’t contract
Crumpled muscle
tension applied to load when a muscle is stretched but not stimulated
Passive Tension
Active tension + Passive tension
Total tension
What type of muscle contraction?
- no change in length but tension increases
EX: postural muscles of body
Isometric
What type of muscle contraction?
- change in length but tension constant
Isotonic
What type of Isotonic muscle contraction?
- overcomes opposing resistance and muscle shortens
Cocentric
What type of Isotonic muscle contraction?
- tension maintained but muscle lengthens
Eccentric
What type of muscle fiber?
- contract more slowly, smaller in diameter, better blood supply, more mitochondria, more fatigue-resistant than fast-twitch, large amount of myoglobin
- postural muscles, more in lower than upper limbs, dark meat of chicken
Slow-twitch oxidative (Type 1)
What type of muscle fiber?
- respond rapidly to nervous stimulation, contain myosin that can break down ATP more rapidly than that in Type 1, leads blood supply, fewer and smaller mitochondria than slow-twitch
- lower limbs in sprinter, upper limbs of most people, white meat
- comes in oxidative (Type 2a) and glycolytic (Type 2b) forms
Fast-twitch (Type 2)
Hypertrophy: increase in…
muscle size
Hypertrophy has an increase in what 4 things other than muscle size?
- Myofibrils
- Nuclei due to fusion of satellite cells
- Strength due to better coordination of muscles
- Production of metabolic enzymes, better circulation, less restriction by fat
Atrophy is the decrease in…
muscle size
Atrophy is reversible except in severe situations where…
cells die
During exercise, both the metabolic rate and heat production…
increase
Post exercise, metabolic rate stays _______ due to oxygen debt
high
Excess heat is lose because of vasodilation and…
sweating
Uncoordinated concentration of muscle fibers resulting in shaking and heat production
Shivering
ATP provides immediate energy for muscle contractions; produced from what three sources?
- Creatine Phosphate
- Anaerobic Respiration
- Aerobic Repsiration
What ATP producer?
- during resting conditions stores energy to synthesize ATP
Creatine phosphate
What ATP producer?
- occurs in absence of oxygen and results in breakdown of glucose to yield ATP and lactic acid
Anaerobic respiration
What ATP producer?
- requires oxygen and breaks down glucose to produce ATP, carbon dioxide and water
- more efficient than anaerobic
Aerobic Respiration
Decreased capacity to work and reduced efficiency of performance
Muscle fatigue
What are the two types of muscle fatigue?
Psychological and Muscular
What type of muscle fatigue?
- depends on emotional state of individuals
Psychological
What type of muscle fatigue?
- results from ATP depletion
Muscular
Muscular muscle fatigue: Acidosis and aTP depletion due to either an increased ATP consumption or a…
decreased ATP production
Muscular muscle fatigue: Oxidative stress, which is characterized by the build-up of excess reactive…
oxygen species
Muscular muscle fatigue: local _______________ reactions
inflammatory
state of fatigue where due to lack of ATP neither contraction nor relaxation can occur
Physiological Contracture
Development of rigid muscles several hours after death
Rigor Mortis
Rigor mortis: Ca2+ leaks into sarcoplasm and attaches to ___________ _________ and cross bridges form
myosin heads
Rigor mortis: absence of _________ —> cross bridges cannot be broken down
ATP
Rigor mortis: rigor ends as tissues start to…
deteriorate
insufficient oxygen consumption relative to increased activity at the onset of exercise
Oxygen Deficit
Oxygen taken in by the body, above that required for resting metabolism after exercise
- repays the oxygen deficit
Recovery Oxygen Consumption
