Physiology Flashcards
What muscle function does this describe: Provide pressure for blood circulation
Cardiac
The functions of the muscular system
Movement Maintaince of Posture Stabilization of Joints Generation of Heat
What is the ability to respond to a stimulus?
Irritability
What us the ability to shorten
Contractibility
What is the ability to return to original dimension after shortening or stretching?
Elasticity
When muscle cells differentiate what happens?
They loose their ability to divide
What pathology of muscles is very rare?
Tumors
What us the name of a benign tumor usually found in the uterus but can also be found in arrector pilli, srotum, or nipples?
Leiomyoma
What is the name of a malignant tumor of smooth muscle usually found in uterus or GI tract?
Leiomuosarcoma
What is the name of a highly aggresive malignant tumor that originates in skeltal muscle, said to be derived from mesenchyme
Rhabdomyosarcoma
What type of muscle is found in the walls of hollowed organs?
Smooth muscle
What muscle is found throughout body attached to bones?
Skeletal
What muscle is found in walls of heart?
Cardiac
What muslce structure does this describe: Faintly striated cells, branching cells, 1-2 nuclei, intercalated disc seperate cells
cardiac
What muscle stimulation does this describe? Involuntary, self-exciting (autoryhtmic) can be controlled by ANS
cardiac
What muscle structure does this describe? long thin cells, striated, many nuclei
skeletal
What muscle function does this describe? posture, movement, joint stabilization
skeletal
What muscle stiumulation does this describe? voluntary contraction, stiumlate by somatic NS
skeletal
What muscle function does this describe: moved fluid and other body substances (food through GI)
smooth (peristalsis)
What muscle stimulation does this describe: involuntary, stiumlated by ANS
smooth
What are muscle fibers organized into?
Bundles
What is the dense irregular CT that covers the whole muscle
Epimysium
What is the CT that surrounds the fascicles?
Perimysium
What is the retucular CT that surounds a single muscle fiber within a fascile?
Endomysium
What is the name for the attachment of the muscle to the less movable bone or tissue?
Origin
What is the name for the attachment of the muscle to the more movable bone or tissue
Insertion
What is the plasma membrane of a muscle cell called?
Sarcolemma
What is the cytoplasm of a muscle cell that contains glycogen, myoglobin called?
Sarcoplasm
What is an oxygen binding pigment called?
Myoglobin
What are the large, subcellular structures that extend the length of a muscle fiber called? 80% of cells volume, muscle contraction?
Myofibrils
What is the smooth endoplasmic reticulum that has the abilioty to store CA2+ and release it during periods of contraction, ATP dependant
Sarcoplasmic Reticulum
What are the extensions of the sarcolemma that extend horizontally into the cell and that form triads with terminal cisterane on either side?
Transverse, or T-Tubules
What is the segment of a myofibril that extends between 2 Z discs, aka the functional unit of a muscle?
Sarcomere
What is the resting length of a sarcomere?
2 um
What filament is positioned laterally in the sarcomere and contains actin, troponin, and tropomyosin?
Thin myofilament or thin filament
What is a regulatory protien made of 3 polypeptides TnT, TnC, and TnI
Troponin
TnT does what?
Holds tropomyosin to actin
TnC does what?
binds calcium
TnI does what?
binds to actin
What blocks actin-myosin binding sites when the muscle is resting?
Tropomyosin
What occupies the center of a sarcomere, primarily composed of myosin and contains a “head”, or “cross bridge” where actin binds?
Thick filament
What is made of titin and holds the thick filament in position and helps prevent sarcomeres from pulling apart during contractions
elastic filament
What is the part of the sarcomere that has the thick myofilament and appears as dark band under microscope?
A band, or anisotropic (doubly refractive)
What is the portion of sarcomere that contains thin filament?
I band, isotrpic (singly refractive)
What is the end of the sarcomere that thick and thin filaments attach to?
Z disc
What is a region of A band that contains thick myofilaments only?
H zone
What bisects the H zone and made of proteins that connect thick and thin filaments
M line
What band contains thin filaments only and shortens during contraction?
I band
What band contains thick filaments only and shortens during contraction?
H band
What band contains thick and thin filaments and does not change in length during contraction?
A band
This is when the stiumlation of a muscle lead to a internal change which include shortening of a sarcomere
Coupling/ Contraction
This is when cellular mechanisms stop the contraction process and lead to rest
Relaxation
Where are skeletal muscle stimulated?
Neuromuscular junction or myoneural junction
What is the neurotransmitter that is stored in the vesicles in the motor neuron ending?
Ach, or acetylcholine
What is the highly folded area of the sarcolemma that lies in the area of the synaptic cleft and contains ACH receptors?
Motor End Plate
What is the enzyme associated with the sarcolemma of the motor end plate that is used to degrade ACH
Acetylcholinesterase (Ache)
What is the first step in the excitation mechanism?
The action potential reaches the end of a motor neuron
What is the second step in the excitation mechanism?
The voltage sensitive Calcium channels in the mem. of neuron open and calcium diffuses into neuron
What is the 3rd step of excitation mechanism?
Influx of Ca causes Ach to be released into the gap via exocytosis
What is the 4th step of excitation mechanism?
Ach diffuses across gap and binds to Ach receptors on the motor end plate
What is the 5th step excitation mechanism?
Binding of Ach to receptor initiates the action potential in sarcolemma along the muscle fiber surface and is is transmitted via T-tubules
What happens after Ach is degraded by AChase?
Acetate diffuses into synaptic cleft and choline is taken to motor nerve ending and can be used to make more ach
What is it called when the action impulse spreads into the muscle fiber via the T-tubules and the impulse causes Ca to diffuse?
Coupling/ Contraction
Where do calcium channels open?
Terminal Cisternae of sarcoplasmic reticulum
What happens when calcium binds to troponin?
The troponin/ tropomyosin blockade is removed and myosin cross bridge binds to actin molecules of the thin myofilament
What happens as the cross bridge continues to attach to the actin?
It pulls the center of the sarcomere and then detaches and as a result the sarcomere shortens
This is when the cross bridge activity stops and when calcium is removed from troponin, the calcium is removed by calcium pumps in SR
Relaxation
Used as a medicine in Brazil, blocks neuromuscular movements,causes paralysis,can affect breathing muscles and cause death by respiratory paralysis
Curare
This blocks the release of Ach
Botulinum Toxin
Relases Aplha-Larotoxin that appears to open the motor neuron Ca channels and leads to massive release of Acg and depletes Ach at synapse
Black widow spider
Consists of a single motor neuron plus the muscle cells (fibers) that is innervates
Motor Unit
Motor neuron disease, progressive and fatal, muscle weakness/wasting impaired speaking swallowing and breathing, due to degeneration of motor neurons
Amyotrophic Lateral Sclerosis
What is the average number of muscle fibers per motor unit?
150
What do muscles used for precision movements have?
smaller motor units and few muscle fibers
What do muscles used for large movements have?
large motor units and large number of muscle fibers
Why does the strength of a contraction increase?
When increasing numbers of motor units are activated
What is the process of generating force in a muscle as a result of cross bridge activity, may or may not lead to shortening?
Contraction
What is the force exerted by a muscle on a load?
Tension (Effort)
What is any force that opposes the tension (effort) generated by muscle contraction?
Load( Resistance)
Contraction when muscle shortens as it moves the load
Concentric
Contraction when muscle lengthen to move the load, can result in greater muscle soreness
Eccentric
Contraction when tension is generated in muscle but it does not change in length
Isometric
This involves lifting weights all or part of one body’s weight or moving the body against some externally imposed resistance
Resistance Training
Contraction with limb movement can be concentric or eccentric
isotonic
Contraction without shortening or movment of the muscle occurs at beginning and end of exercise helps stabilize
isometric
Response of a skeletal muscle to a single, brief stimulus
Twitch
Short period of time after stimulation when excitation/ coupling is occurring
Latent (Lag) Period
Cross bridge activity leads to tension development, amount of tension depends on number of motor units recruited (activated)
Contraction Period
Cross bridge activity stops as calcium is pumped back into the SR and muscle tension falls
Relaxation Period
Contractions of a muscle that vary in strength
Graded muscle contractions
What are the 2 ways to produce graded muscle contractions?
Change rate of stimulation and strength or stimulus
This is when a 2nd stimulus is applied to a muscle before it is finished relaxing
Wave (temporal) stimuli
This is when a 2nd stimulus is applied to a muscle before it is finished relaxing, but the stimuli is delivered very frequently
Incomplete Tetanus
This is prolonged, smooth contractions that result from very rapid stimulus
Complete Tetanus
This is when pulses of an increasing voltage are delivered to a recruitment muscle and the result is increased motor units and stronger muscle contractions
Multiple Motor Unit Summation
This is when a strength of a muscle contraction increases with repeated stimulation , the first few contractions cause the muscle to “warm up”
Treppe (staircase effect)
All muscles slightly contracted even when they seem relaxed, maintained by nervous system , prevents atrophy, maintains stability and posture
Muscle Tone
This is the preferred fuel for muscle contraction and needed for relaxation as well
ATP
This is when the cross bridges move from low energy to high energy positions
When ATP fuels the power stroke
How does ATP aid in sarcomere relaxation?
Pumps calcium back into the SR
Muscle cells store very little _____
ATP
THis is when creatine looses a phosphate (creatine kinase) which is added to ADP and forms ATP
Creatine Synthesis
THis takes place in sarcoplasm, little ATP is generated from each glucose used for quick, short term, and vigorous activity
Anaerobic Respiration
This takes place in the mitochondria it is a slower pathway but is used for prolonged activities like jogging
Aerobic Respiration
The length of time that a muscle can continue to contract using aerobic pathways
Aerobic Endurance
The point at which a muscle metabolism switches from aerobic to anaerobic
Anaerobic threshold
A state in which muscle is physiologically unable to contract because ATP production rate is less than ATP consumption
Muscle Fatigue
The amount of oxygen needed to restore muscle to its resting metabolic state
Oxygen debt
What does lactic acid do in the muscle cell?
It combines with oxygen to produce pyruvic acid and then forms ATP carbon dioxide and water
What happens to lactic acid in the liver?
Turns to glucose and than broken down into glycogen
What does strength of a muscle contraction depend on?
of motor units recruited, size of muscle, rate of stimulation, and the starting length of a sarcomere ( degree of muscle stretch)
The greater number of motor neurons stimulated the greater the _____________ (3 words)
Force of Contraction
An increased rate of stimulation allows more ____ to develop
force
An optimum sarcomere length allows for maximum_________( 1 word)
Contraction
What is the optimum length of a sarcomere?
The resting length of a skeletal muscle
How is the rate of a contraction measured?
Velocity
What does velocity depend on?
Characteristics of a load
What are the three types of muscle fibers?
Slow oxidative, fast oxidative, and fast glycolic
The quantity of the three type of muscle fibers determines what about muscle contraction?
the velocity and duration
Name the muscle fiber based on its structure: ATPase responds slowly, aerobic adapted, myoglobin(red), vascular, many mitochondria, small diameter
Slow Oxidative
Name this muscle fiber based on its function: Slow speed of contraction
Slow Oxidative
Name this muscle fiber based on it properties: fatigue resistant, used for endurance and prolonged contraction
slow oxidative
Name this muscle fiber based on its structure: ATPase responds quick, aerobic, pink (less myoglobin), vascular, mitochondrial, intermediate diameter
Fast oxidative
Name these muscle fiber based on its function: fast speed of contraction
Fast Oxidative, Fast Glycolytic
Name this muscle fiber based on it properties: fatigue resistant, used for endurance and rapid contractions
Fast oxidative
Name this muscle fiber based on structure: ATPase responds quick, anaerobic, white, no blood supply, few mitochondria, large
Fast Glycolytic
Name this muscle fiber based on these properties: fatigue easy, not intense for short term movements
Fast Glycolytic
Name this muscle type: small spindle shaped fibers, central nuclei, no striations, little SR and no T-tubules, sarcolemma sequesters calcium
Smooth muscle
Name this muscle type: small spindle shaped fibers, central nucleus, no striations, little SR and no T-tubules, sarcolemma sequesters calcium
Smooth muscle
What is absent in smooth muscle and what is present?
Absent= Troponin, Present= Tropomyosin
How are thick and thin myofilaments arranged in smooth muscles?
Diagonally, when the cell contracts it twist like a corkscrew
What are the fibers that are attached to dense bodies that are attached to the sarcolemma and thin myofilaments in smooth muscle?
Non contractile intermediate filaments
In smooth muscles fibers are not always organized into_______
Fascicles
In most organs smooth muscle fibers are arranged into cellular sheets with ___ or ___ orientation
circular or longitudinal
What is neural regulation of smooth muscle stimulated by?
The ANS
What are the neurotransmitters of smooth muscle?
Ach, norepinephrine
What is some smooth muscle controlled by?
Pacemaker cells, chemical factors
Name this smooth muscle type: contracts as one unit, rhythmically and automatically EX: walls of hollow organs like uterus
Single unit or visceral
Name this smooth muscle type: Lacks synchrony, graded contractions, many nerve endings in muscle Ex: Blood Vessels and Bronchi
Multi unit
A rigid structure that movies about a fixed point, classified as simple machines because they can do work
Lever
What is the fixed point a lever moves around?
Fulcrum
What is the muscle that assists the PM by performing same movement or preventing opps. movement
Synergist
What is the muscle that stabilizes the bone of the muscle?
Fixator
What causes disuse atrophy?
Prolonged bed rest, casting, or local nerve damage
What are the characteristics of disuse atrophy?
Reduction on size of muscle fibers
What are the causes of muscle cramps?
Circulatory Impairment or heart disorders that can lead to electrolyte problems
What are the characteristics of muscle cramps?
Sustained involuntary contractions of a skeletal muscle
What causes muscular dystrophy?
X linked recessive disorder in half of cases, defective gene causes dystrophin to be absent
What muscle pathology does this describe: reduction in muscle fibers, necrosis muscle replaced with CT or fat, delayed sitting, standing and walking
Muscular Dystrophy
What causes myasthenia gravis?
defective transmissions at neuromuscular junction due to decreased ACH receptors
What muscle pathology does this describe? Fatigue, chronic respiratory infections, weakness
myasthenia gravis
what are the functions of the nervous system?
- ) monitors the internal and external environments.
- ) integrates sensory information.
- ) coordinates voluntary and involuntary responses of many organ systems
CNS vs. PNS
CNS= brain and spinal cord PNS= nerves
- the membrane potential of a normal cell under homeostatic conditions (-70mV)
- the membrane potential at which and action potential begins
- chemical compound released to affect the membrane potential of a neuron
- resting potential
- threshold potential
- release of a neurotransmitter
what are the steps at neuromuscular junction
1) action potential arrives at axon terminal 2) voltage gated sodium channels open and sodium rushes in 3) vesicles exocytose acetylcholine 4) neurotransmitters diffuse across synaptic cleft and binds to neurotransmitters receptors on the post synaptic cleft 5) binding of neurotransmitters opens ion channels resulting in a graded potential (change in shape) gives channel for ion to flux and change membrane potential 6) neurotransmitters are terminated
acetylcholinesterase
degrades acetylcholine
how are neurotransmitters classified
by structure and function
Spatial Summation
2 different stimuli at the same time but different place so they are added
Summation
one EPSP cannot cause an action potential however a sum of them can
what are the two types of postsynaptic potential
EPSP and IPSP
EPSP
excitatory (+) pushes membrane potential closer to threshold sodium influx is greater then potassium and causes depolarization
IPSP
inhibitory (-) brings membrane potential further away from threshold neurotransmitter opens channels for K+ to leave and Cl- to come in… removes ability to provide an action potential
what are the 3 ways that neurotransmitters are terminated
1)Reuptake~ most common 2)degraded~ enzymes go into synaptic cleft and chews it up 3) Diffusion~Neurotransmitters bind to receptors and diffuse away
Temporal Summation
rapid impulse sent to the same location at different times closer so the look like they are being added
acetylcholine
first neurotransmitter discovered, degraded by the enzyme acetylcholinesterase, released by all neurons that stimulate skeletal muscle
what are the 6 steps of cross bridge cycling
1) exposure of binding sites on Actin 2) binding of myosin to actin 3) power stroke of the cross bridge that causes sliding of thin filaments 4) binding of ATP to cross bridge head 5) hydrolysis of ATP receptors cross bridge head 6) active transport of ca stops to Sr?terminal cysteine
where do the calcium ions come from to begin this process
terminal cisternae
why don’t you remain in rigamortis
you do not remain in rigor mortis is because myosin, actin, and muscle cells begin to disintegrate, or die
what are the two layers of smooth muscle
longitudinal~ outside circular~ inside
what don’t smooth muscles have
troponin, myosin, T Tubules
what are gap junctions
a gap junction is a junction between two cells that allows ion to transfer from cell to cell, allows action potentials to flow from cell to cell
what are the steps to smooth muscles contraction
1) calcium enters smooth cell 2) calcium binds to and activates calmodulin 3) activated calmodulin activates the myosin light chain kinase enzymes 4) the activated kinase enzymes catalyze transfer of phosphate to myosin activating the myosin ATPases 5) activated myosin forms cross bridges with actin of the thin filaments and shortening begins
contraction mechanism
-actin and myosin interact according to the sliding filament mechanism -the final trigger for contraction is a rise in intracellular calcium -calcium is released from SR and from the extracellular space -calcium interacts with calmodulin and (read final steps above) -very energy efficient (slow ATPase) -Myofilaments may maintain a latch state for prolonged contractions
what does relation require
~calcium detachment from calmodulin ~active transport of calcium into SR and ECF ~dephosphorylation of myosin to reduce myosin ATP activity
duchenne muscular dystrophy
only expressed in males diagnosed between ages 2-10 victims usually don’t live past 20 caused by a lack of cytoplasmic protein dystrophin no cure, some treatments being tested example: myoblast transfer therapy: inject diseased muscle with healthy myoblast cell that fuse with unhealthy ones
disc junctions
anchor cardiac cells
desosomes
prevent cells from separating from contraction
how is the cardiac muscle stimulated
stimulated by nerves and is self-excitable
what is the absolute refractory period
long at about 250ms
syncytium
allow heart to function as one muscle
