Ch 10 Muscular System Flashcards
What is the PRIME function of muscle?
Convert chemical energy (ATP) into mechanical energy in order to:
- generate force
- perform work
- produce movements
What are the types of muscle tissue?
Skeletal Muscle
- striated
- voluntary
- stimulated by nervous system only
Cardiac Muscle
- striated
- involuntary
- stimulated/inhibited by nervous/endocrine system
Smooth Muscle
- non-striated
- involuntary
- stimulated/inhibited by nervous/endocrine system
What are the 5 characteristics of muscle tissue?
- Excitability - stimulated by signal
- Conductivity - membrane carries elec signal
- Contractility - shortens
- Extensibility - Lengthens
- Elasticity - returns to orig shape
What are the 3 GENERAL functions of muscle tissue?
- Motion
- Stabilizing body positions and regulation of organ volume, ie sphincter
- Thermogenesis
What are the types of fascia?
Superficial fascia - hypodermis
Deep fascia - fibrous connective tissue that allows muscle to ove past eachother w/o friction
What are the connective tissues of skeletal muscles?
Epimysium - out layer surrounds entire muscle
Perimysium - surrounds fascicles
Endomysium - surrounds individual muscle cells (fibers). provides insultation to excite one cell but not another.
What is a tendon? What is a tendon sheath? What is aponeurosis?
Tendon - the three types of connective tissue that connect muscle to bone
Tendon sheath - band that surrounds tendons to reduce friction w/ synovial membrane
Aponeurosis - tendon that forms a flat sheet instead of cord
What are the following:
- myofiber
- sarcolemma
- sarcoplasm
- myofibrils
- myofilaments
- sarcomeres
myofiber - muscle cell
sarcolemma - cell membrane of muscle cell
sarcoplasm - cytoplasm of muscle cell
myofibrils - bundle of myofilaments
myofilaments - actin+myosin
sarcomeres - function unit of muscle that contracts/extends
What is a sarcomere?
The functional unit of the muscle within myofibrils composed of thin actin and thick myosin fliaments
Name the segments of the sarcomere pictured.
Go over the anatomy of the thin myofilament. What is the purpose of the interaction of all the different parts of this myofilament?
Each actin molecule on the strand of actin filament has a myosin-binding site
- at rest this binding site is hidden to prevent binding which will cause contraction
- the tropomyosin-troponin complex covers these binding sites
What are the parts of the thick myofilament pictured?
What is the sarcoplasmic reticulum?
Intracellular tubules wrapping the myofibrils
- stores Ca2+ ions at rest
- releases Ca2+ ions into sarcoplasm when stimulated causing tropmyosin-troponin complex to release myosin binding sits on thin actin myofilaments
What are the transverse tubules?
Tunneled extension of the sarcolemma perpendicular to the myofibrils in between the terminal cisternae
-carries electrical signal from the sarcolemma to signal the sarcoplasmic reticulum to open Ca2+ channel
What is a motor unit? What is recruitment?
1 Motor Neuron + ALL of the muscle cells it innervates
- small motor units for precise movements
- large motor units for gross movements
Recruitment is how many motor units you are activating
Name the components of the neuromuscular junction pictured. What oes each of the following component do
Axon terminals
Synapse and synaptic cleft
Motor end plate
Synaptic vesicles
Neurotransmitter = acetylcholine (ACh)
ACh receptors on motor end plate
Axon terminals - end of the neuron that holds synaptic vesicles
Synapse and synaptic cleft - releases neurotransmitter into cleft where it is uptaked by receptors
Motor end plate - part of muscle cell interacting w/ neuron ridged for more surface area
Synaptic vesicles - hold neurotransmitters
Neurotransmitter = acetylcholine (ACh) - activates muscle cell
ACh receptors on motor end plate - bind the ACh
How does the neuromuscular junction work?
- Nerve impulse travels down membrane of neuron causing neuron Ca2+ channels to open
- Synaptic vesicles rupture into synapse
- ACh diffuses to receptors on motor end plate
- ACh binding to receptors starts impulse in sarcolemma by opening Na+ channels causing voltage change
- The voltage change travels along sarcolemma and down T-Tubules causing voltage change in sarcoplasmic reticulum
- Voltage change in sarcoplasmic reticulum causes Ca2+ channels to open and remove tropomyosin-troponin from myosin binding sites on actin
How does the sliding filament theory work for excitation-contraction coupling?
Cross bridges attach to binding sites on thin myofilaments
- The cross bridges tilt
- Thin myofilaments slide across thick myofilaments shortening sarcomeres
What is the power stroke?
Power stroke is the muscle contraction
- Ca2+ channels in sarcoplasmic reticulum open and bind topomyosin-troponin complex and activate ATPase
- Cross bridges bind and swivel
What is the recovery stroke?
Muscle relaxation
- ACh removed from synapse
- Ca2+ pumped back to sarcoplasmic reticulum
- W/ no Ca2+ tropomyosin-troponin complex covers myosin binding sites
- W/ no Ca2+ myosin cross bridges release and thin myofilaments slide back to resting position
Go through excitation-contraction coupling from beginning to end muthafucka.
- Arrival of nerve impulse at axon terminal of motor neuron
- Acetylcholine released
- Acetylcholine binds to receptors on motor end plate
- Electrical message created in sarcolemma
- It travels down T-tubules and throughout sarcoplasmic reticulum
- Ca++ released over the myofibrils
- Ca++ binds to troponin; tropomyosin-troponin complex shifts to expose binding sites
- Energy from ATP activates and “cocks” myosin cross bridges
- Cross bridges attach to binding sites on actin molecules
- Power stroke; thin myofilaments “slide” over thick myofilaments
- Binding of new ATP, breaking cross bridge; repeat steps 9 – 10
- Cessation of nerve impulse and ACh release at motor neuron
- Acetylcholinase breaks down ACh
- Ca++ actively transported back into sarcoplasmic reticulum
- Loss of Ca++ from sarcoplasm allows tropomyosin-troponin to block active sites on actin
- Thin myofilaments “slide” back across thick myofilaments into resting position
How does sarcomere length affect contraction?
Muscle strength depends on how stretched/contracted the muscle is before it is stimulated
- too contracted/stretched=too much/not enough overlap of myofilaments resulting in less force
- there is an optimum resting length
What is muscle tone?
state of partial contraction of a resting skeletal muscle
- a few motor units are contracting while others are at rest
- essential for maintaining posture
- ASYNCHRONOUS FIRING of motor units (take turns)
What enzymes are involved in providing IMMEDIATE energy to skeletal muscle?
Myokinase
-transfers the Pi from ADP→AMP+Pi to ADP+Pi→ATP
Creatine Kinase
-takes Pi from creatine phosphate and donates to ADP+Pi→ATP
Phosphagen system - provides all energy for short intense activity. Around 15 secs
Once the phosphagen system is exhausted, what provides short-term energy?
Anaerobic Metabolism
- switch to anaerobic metabolism once phosphagen system is exhausted b/c O2 in myoglobin is used up
- Need ATP before Aerobic Respiration kicks in and delivers O2 to muscles
- Anaerobic metabolism buys you time until Aerobic metabolism kicks in
- 30-40 secs of maximum activity
What kind of metabolism provides long term energy?
Cardiovascular and respiratory systems ‘‘catch up’’ after about 40 secs and start delivering sufficient oxygen so aerobic respiration meets ATP demand
What will prevent activity once aerobic metabolism kicks in?
Activity will continue until loss of glycogen, blood glucose, fluids and electrolytes coupled with lactic acid buildup
-ie. fatigue
What is oxygen debt?
The difference between O2 consumption at rest and the evated O2 consumption after exercise
-debt repaid to replenish O2 in myoglobin, replenish phosphagen system
What are the types of muscle fibers?
- Slow oxidative, Slow-Twitch, Red, Type I Fibers
- abundant in mitochondria, myoglobin and capillaries
- aerobic respiration
- don’t fatigue easily - Fast Glycolytic, Fast-twitch, White, Type II Fibers
- poor in mitochondria, myoglobin, and capillaries
- Phosphagen pathways
- Anaerobic metabolism
- Fatigue quickly - Intermediate fibers
- characteristics of both
Go through the controlled condition, receptor, control center, effectors and return to homeostasis for body temperature control for decrease in body temp.
Controlled condition - stimulus disrupts homeostasis by causing decrease in body temp
Receptor - thermoreceptors in skin send signals to hypothalamus
Control Center - hypothalamic control center sends nerve impulse to stimulate skeletal muscles
Effectors - skeletal muscles increase their tone involuntarily, ie. shiver
Return to Homeostasis - innefficient use of energy of contracting skeletal muscles generate heat and return to homeostasis
What is the all or none principle?
In order to contract the neuron must meet threshold stimulus
What kind of contraction is this and what are the phases of the contraction?
Twitch Contraction
- One single contraction due to a single electrical impules
- not sustained
What kind of contraction is this?
Treppe contraction
- staircase phenomenon
- multiple stimuli with complete rest in between
- force goes up with each contraction
What are isotonic and isometric contractions?
Isotonic contraction
-length of muscle changes but force stays the same
Isometric contraction
-length of muscle stays the same but force changes
What is wave summation?
Stimulate the muscle after the refractory period but before muscle has a chance to fully relax
-more force with 2nd twitch
What is incomplete tetany (non-fused)?
some relaxation then another stimulus
- 20-30 stim/sec
- daily movement
What is complete (non-fused) tetany?
Experimental only
- no relaxation
- 80-100 stim/sec
- tetanus
What differentiates cardiac muscle?
Striated
Single nucleus/cell
Intercalated discs
Functional syncytium
Involuntary
What differentiates smooth muscle?
Non-striated (has actin/myosin but no sarcomeres)
Single nucleus/cell
Two types
visceral (functional syncytium) - digestive tract
multiunit - blood vessels
How do muscle cells produce movement?
exert force on tendons
the tendons cross joints
the joints act as fulcrum for lever system
What is the origin, insertion, and gaster of the muscle?
Origin
part of muscle with least movement
Insertion
part of muscle with most movement
Gaster
belly of muscle that bulges with flexing
What is the agonist and antagonist for flexion of the elbow?
Agonist or ‘Prime Mover’ is the Biceps brachii
Antagonist is the triceps brachii
