Physiology 208 Muscles PART 2

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Lecture 5

Question Answer
what is the difference between single twitch and summation?ST muscles relax between stimuli and summation does not allow muscle to relax
what is the size principle?As stimulus onto motor neuron pool increases; larger motor neurons are recruited
Rm is high and conduction velocity is low, which type of twitch fiber is used?Slow l
Rm is low and conduction velocity is high, which type of twitch fiber is used?Fast ll
Put in order of motor unitsSlow oxidative - fast oxidative glycolytic - fast glycolytic
Asynchronous recruitmentduring submax contraction, CNS modulates firing rates of upper motor neurons; prevent fatigue
Isotonic contractionMuscle contracts & shortens; creates force to move load
Isometric contractionMuscle contracts & not shorten; creates not enough force to move load
Concentric contractionMuscle shortens while generating force
Excentric contractionMuscle lengthens while generating force
Two proposed mechanisms by which muscle mass may be increasedhypertrophy or hyperplasia
Which cells are involved in muscle repair and may form new muscle fibres?myosatellite
During muscle hypertrophy, what components are increased?Contactile proteins, sacromeres and glycogen
Several studies show a greater rate of myofiber hypertrophy for type ___ fibers in comparison to type ___ fibersll and l
Studies have shown that astronauts experience up to a ____% loss of muscle mass on spaceflights lasting five to 11 days20
Cachexiaweakness and/or wasting due to chronic disease

Lecture 6

Question Answer
How does the CNS respond sensing change?Contraction (motor neurons) - Relaxation (inhibitory interneurons)
Skeletal muscle reflexes 4 components1. Sensory receptor. 2. Integrating center. 3. Efferent neurons. 4. Effectors
Monosynaptic reflexSingle synapse between afferent and efferent
Polysynaptic reflex2+ synapses; both synapses in CNS
Proprioceptorsposition of our limbs in space, movements, and the effort exerted by skeletal muscle
Where are joint receptors foind?capsules and ligaments around joints
How are joint receptors stimulated?mechanical distortion that accompany changes in the position of bones
What are muscle spindles made up of?Sensory neurons wrapped around intrafusal muscle fibres
extrafusal muscle fibres are regular muscle fibres innervated by?alpha motor neurons
Spindles are ____ tonically active and firing even when muscle is relaxedTonically
Does extrafusal OR intrafusal muscle fibres maintain a certain level of tension at rest?Extrafusal
Without gamma motor neuros, muscle contraction causes spindle diring rate to?Dcerease
Alpha-gamma coactivationmaintains spindle function when muscle contracts
What is the golgi tendon organ location?Neuron interwoven in collagen fibres inside connective tissue
What does the golgi tendon organ do?control force in muscles and stability around joints
What does the golgi tendon reflex do?Protects muscle from excessively heavy loads by causing muscle to relax and drop load
Knee jerk reflex illustratesmonosynaptic and reciprocal inhibition
Effernt path 1 for knee jerkSomatic motor neuron - Quadriceps contract
Effernt path 2 for knee jerkInterneuron inhibition - Hamstring
Afferent path for knee jerkSensory neuron neuron - Spindles stretch and fire
Reciprocal inhibitionSensory receptor stimulus causes 1 muscle contraction & 1 antagonistic muscle inhibition
Crossed extensor reflex Flexion reflex in 1 limb causes extensions in opposite limb - Balance
What are cardiac muscles intercalted disks by?desmosomes (mech) & gap junctions (electric)
Between skeletal and cardiac muscle: Which has less abundant but larger T-Tubules?Skeletal
Between skeletal and cardiac muscle: Which has smaller amounts of sarcoplasmic reticulum?Cardiac
In cardiac muscles, how much abundance of mitochondria are there?1/3 of cell volume
Cardiac muscle cells may contract almost ________ times in an average life span without resting3 billion
Approximately ____% of myocardial cells are specialized non-contracting autorhythmic cells1
Depolarization of cardiac muscles begin at?sinotrial node
Autorhythmic myocardial cells have an unstable resting membrane potential of?-60mV
IfHyperpolarization-activated cyclic nucleotidegated (HCN) channels
At which potential HCN channels open?-60 to nearly -40mV and allow a net influx of Na+
At which potential does HCN channels close and T-type Ca2+ channels open?Just before -40mV
Explain the 4 steps of HCNsHCN channels open - T-type Ca2+ channels open - L-type Ca2+ - K+ channels open
AP’s in contractile myocardial cells graph (5)Na+ opens - Na+ closes - Ca2+ opens; fast K+ close - Ca2+ close; fast K+ open - Rest

Lecture 7

Question Answer
In cardiac muscle L-type Ca2+ channels (DHP receptors), why Ca2+ entry is necessary for contraction?As they are NOT mechanically coupled to RyR
EC coupling in cardiac muscle stepsCa2+ enters inducing Ca2+ through RyR - Release causes summation Ca2+ signal - Ca2+ bnds to troponin initiating contraction
An increase in [Ca2+]i triggers contraction by removing?the inhibition of cross bridge cycling
A relaxed state of CBC is? (3)Myosin cocked - Tropomyosin blocks binding site on actin - Myosin weakly binds actin
What is the primary mechanism of cardiac muscle?Ca2+ reuptake into the SR
In cardiac muscle the SERCA pump is regulated by?phospholamban
in dephosphorylated state, what does PLN inhibit?SERCA
In cardiac muscle, what regulates force?increase in intracellular Ca2+
In skeletal muscle, what regulates force?summation in individual fibres
Cardiac muscle is capable of ____ single twitch contractionsgraded
if cytosolic Ca2+ is low, what happens to some actin?remains covered by tropomyosin
Explain the length tension relationshipcardiac muscle generates a greater force when slightly stretched
The sympathetic ____ heart rate/conduction and contractilityincreases
The parasympathetic ____ heart rate/conduction (increases/decreases)decreases
The sympathetic controls autorhythmic or contractile?both
The parasympathetic controls autorhythmic or contractile?autorhythmic
Sympathetic modulation of contraction: Phosphorylation of Ca2+ channels causes?Calcium channels to remain open
Sympathetic modulation of contraction: Phosphorylation of RyR causes?Increasing release of Ca2+
Sympathetic modulation of contraction: Phosphorylation of SERCA causes?increases the speed of Ca2+ re-uptake
Heart rate is under ____ control (tonic/phasic)Tonic
-with no autonomic stimulation autorhythmic cells of the SA node have an intrinsic firing rate of ~____ action potentials per minute90
at resting heart rate of 70-72 BPM ____ is dominant (parasympathetic/sympathetic)parasympathetic
Parasympathetic neurons containing ACh mainly innervate which nodes?SA and AV
When parasympathetic neurons contains ACh, does it increase or decrease heart rate?decrease
What happens when ACh acts on muscarinic cholinergic receptors?Opens K+ channels and closes T-type Ca2+ and HCN channels
Beta1 adrenergic receptors can be activated by?NE from sympathetic neurons/epinephrine
NE released from sympathetic neurons or epinephrine comes from where?from adrenal medulla
Increased Na+ conductance through HCN channels and Ca2+ through T-type channels causes?Rapid threshold - decreased repolarization
What kind of nucleous does smooth muscles have?Unicleated
Which muscles lack troponin & T-tubules?Smooth
In smooth muscles, what forms cytoskeletons?non-contractile, Intermediate filaments
In smooth muscles, what forms cytoskeletons?Intermediate filaments (non-contractile) and protein dense bodies
In smooth muscles: ___ attaches to dense bodies & ___ is surrounded by ___Action-Myosin-Actin

Lecture 8

Question Answer
Smooth muscle location groups (6)Vasc - Gas - Urinary - Resp - Reproduct - Ocular
Smooth muscle contraction patternsSmooth vs. Phasic
A phasic smooth muscle that is relaxed is...Esophogus
A phasic smooth muscle that cycles between contraction and relaxation is...Intestine
A tonic smooth muscle that is usually contracted is...Sphincter relaxes; letting things pass
A tonic smooth muscle whos contraction is varied as needed...vasc
Smooth muscle communication with neighboring cells are?Unitary - Multiunit
Unitary (single unit) smooth muscle (3)gap junction - coordinates contraction - Visceral smooth muscle
Unitary (single unit) smooth muscle (3)not electrical - iris and uteral reproducton prior to delivary
Smooth muscle may contract in response to?synaptic transmission or electrical coupling
Smooth muscle is usually innervated by which nervous system?autonomic
Receptor subtype differences in musclesα-adrenergic and β-adrenergic
What do α-adrenergics do?Vessel constriction
What do β-adrenergics do?Airway dilation
Action Potentials of Smooth Muscle can be initiated by?Neural, hormonal or mechanical
Action Potentials of Smooth Muscles' spike is similar to?Skeletal muscles
Action Potentials of Cardiac Muscles' plateu is similar to?Cardiac muscles
Smooth muscles upstroke slower because?Ca2+ channels propagate the AP instead of Na+
Smooth muscles repolarization is slower because?Ca2+ inactivates slowly & delayed voltage gated K+
Spontaneous AP: When do slow wave potentials fire action potential?When they reach threshold
Spontaneous AP: Pacemaker potentials always depolarize to?Threshold
In some smooth muscle Vm oscillations leads to?tonic contractions in the absence of action potentials
Action potentials usually do not occur in ____ smooth musclemultiunit
Are graded potentials multunit or single unit?Multi
Are Spontaneous AP multunit or single unit?Single
Are Autonomic AP multunit or single unit?Single
Autonomic AP initiation has which type of electrical activity? Spikes or plateaus
Autonomic AP initiation has which type of electrical activity?Slow wave - Pacemaker
Contraction due to electrical signaling is known as?electromechanical coupling
Ca2+ activated contraction is increased by? (3)Ca2+ entry through voltage gated/ligand channel
Ca2+ activated contraction is increased by? (3)Ca2+ entry through voltage gated/ligand channel - Ca2+ release from the SR - Ca2+ entry through voltage-independent channels
Ca2+ release from the SR results in?Ca2+ induced Ca2+ release from RyR - IP3 Ca2+ release from IP3R
Ca2+ entry through voltage-independent channels results in?store operated Ca2+ channels and stretch activated channels
Out of skeletal, cardiac and smooth muscles, which has the least SR?Smooth
GCPR-Phospholipase C signal transductionG protein → PLC → Phospholipid to DAG → IP3 diffuses into cytoplasm →DAG activates PKC → Ca2+ signal from IP3
Depletion of Ca2+ in the SR causes activation of which channels?Store operated; Ca2+ influx
Ca2+ release from SR via IP3 pathway (IP3 binds to IP3 receptor) and entry of Ca2+ via store operated channels are voltage independent and known as?pharmacomechanical coupling
Stretch activated ion channels in the cell membrane of some smooth muscle that when activated lead to depolarizationCa2+ , Cl-, TRPV4, TRPC1, TRPC6
In smooth muscles, stretch has been shown to cause phosporylation of the myosin light chain leading to?contraction
Ca2+ signal in smooth muscle4 Ca2+ ions bind to calmodulin
How does smooth muscles compare to skeletal and cardiac muscle ATPase activity of myosin?MLCK phosphorylates the MLC ll changing conformation; in the other muscles its always held high
Initiating cross bridge cycling in smooth muscle primarily activates which thick filaments? Caldesmon and Calponin
In smooth muscles how does relaxation work?Ca2+ moved back to SR and extracellular space - MLC ll dephosphorylated by MLCP
smooth muscle can maintain force for an extended period of time with little ATP during relaxationlatch state
Neurotransmitters, hormones and paracrine molecules alter smooth muscle Ca2+ sensitivity by modulating?MLCP
Contractile force in smooth muscle largely depends on? MLC phosphodylation and dephosphorylation
MLC phosphorlyation is regulated by?the Ca2+-CaM complex
Out of skeletal, cardiac and smooth muscles, which can regulate Ca2+ over the widest range?Smooth

Lecture 9

Question Answer
Role of innervation (Skeletal, Cardiac, Smooth)Initiate / Modify / Initiate+ modify
tiation of contraction (Skeletal, Cardiac, Smooth)Neural / Myogenic / Myogenic, neural, hormonal, local
Innervation and level of control (Skeletal, Cardiac, Smooth)Somatic, conscience / Autonomic / Autonomic
electrically coupled? (Skeletal, Cardiac, Smooth)No / Yes / Varies
Presence of troponin / tropomyosin? (Skeletal, Cardiac, Smooth)Yes / Yes / Only Tropomyosin
Presence of T-tubules (Skeletal, Cardiac, Smooth)Yes / Yes / No
Crossbridges cycling thick vs. think filament (Skeletal, Cardiac, Smooth)Thin, Thin, Thick
Source of cytosolic calcium (Skeletal, Cardiac, Smooth)SR / SR+EF / SR+EF
Nature of “calcium sensor” for contraction: (Skeletal, Cardiac, Smooth)Troponin / Troponin / Calmodulin
Termination of contraction (Skeletal, Cardiac, Smooth)Breakdown of Acetylcholine; re-uptake of Ca in SR / Repolarization; decrease Ca / Decrease sarcoplasmic Ca; MLCp
Metabolism (Skeletal, Cardiac, Smooth)oxidative/glycolytic / dominatly oxidative / dominantly glycolytic
Regulation of Force (Skeletal, Cardiac, Smooth)Motor unit summation / Calcium entry / MLCK & Phosphatase activity
Contraction speed (Skeletal, Cardiac, Smooth)FAST=20% BMR / Intermediate=10% BMR / SLOW=1-2% BMR (economical)
Primary Roles of the circulatory systemNutrition - Repair - Cellular wastes
Secondary Roles of the circulatory systemHormones/Neurotransmitters - Heat - Antibodies
What did Dr. William Harvey prove?in 1 hour heart pumped entire body weight of blood
According to Dr. William Harvey, blood in right side of heart is pumped through ___ before entering left sidelungs