Anat and Phys Exam 2

Contraction

Function of the muscle, to move the body and things within the body

3 types of muscles

Smooth, skeletal, and cardiac

Smooth muscle

Involuntary, not striated ; gut, glands, organs, eye chamber, hair; central located nucleus; regulated by ANS

Skeletal

Voluntary, striated; bones; do not branch and lack intercalated disks, multinucleated cells, require nerve impulse for stimulous

Cardiac

Involuntary, striated; found in heart, regulated by ANS; elongated branching cells

Intercalated disks

Highly specialized cell membranes that join cardiac muscle cells, facilitates transmission of electrical impulse (basically makes sure muscle fibers beat in unison thus heart beat)

Fiber

One muscle cell

Sarcolemma

Plasma (cell) membrane of a muscle cell/fiber

Sarcoplasm

Cytoplasm of muscle cell/fiber

Sarcoplasmic reticulum

Smooth ER of muscle cell, storage area for fiber

Sacro and Myo

Prefixes meaning muscle

Origin

Closest to body trunk, least movable attachment, usually proximal and/or medial

Insertion

Most movable attachment, usually distal and/or lateral

Contraction of the muscle brings what together

Origin and Insertion, only way for a muscle to exert force

Extensors

Muscles extend or increase angles between body parts; forearm

Flexors

Flex or decrease angle between body parts; underam

Adductors

Pulls limb towards median plane

Abductors

Pulling limb away from median plane

Constrictors (sphincters)

Surround circular opening, closes when they contract (decreases lumen of something, like iris or sphincters in digestive glands)

Dilators

Surround circular opening, opens when contracts (increases size of lumen, uncommon in mammals)

Agonists

Muscles that promote a given movement, like 4 muscles of the quad

Antagonists

Muscles that inhibit a given movement, prevent hyperextension, etc

Red muscle fibers (dark meat)

Used for endurance; more myoglobin, glycogen, and mitochondria, slow twitch (slower to contract but fatigue slowly)

White muscle fibers (light meat)

Not made for endurance, fast twitch (contracts quickly but fatigues faster)

Myoglobin (mb)

Oxygen storage, in red muscle fibers

Glycogen

Glucose storage, in red muscle fibers

Mitochondria

ATP production, in red muscle fibers

Muscle fiber arrangements in muscle

Parallel, Pennate, Fleshy, and Oblique

Parallel muscle fibers

Tendon that comes off at end of fibers and attach to bones (all muscles of tendons); pectoralis muscle

Pennate

Feather-like fibers with central tendon, wide at the top and converges at the tendon, biceps

Fleshy

Appears to attach directly to bone (no gross tendon), but has short microscopic tendons between muscle fibers and bones, brachialis

Oblique

Circular or convergent, abdomen, at an angle

Connective Tissue (CT) harnessing muscles

Endomysium, Perimysium, Epimysium; All meet at ends (or center for pennate muscles) to attach to bones which transfers movement and energy of contraction to bones

Endomysium

Loose CT around every muscle cell

Perimysium

Loose CT around bundles (fascicles) of muscle cells

Epimysium

Dense irregular to regular CT around whole muscle

Myofibrils

Strands that make up muscle cells, composed themselves of myofilaments, which were arranges in units called sarcomeres along these

Myofilaments of Myofibrils

Myosin and actin

Myosin

Thick filament

Actin

Thin filament

Sarcomeres

Functional and contractile unit of striated muscle tissue (microfibers), made up of actin and myosin, extend from one z line to the next, each tube contracts itself

Striations

Banding patterns of muscle fibers

Parts of the sarcomere

A band, I band, H band, Z line, M line (A band always stays same length, H and I get smaller)

A band

Length of myosin filament, includes overlap with actin, stains dark, yellow in graph

I band

Actin only, does not include area of overlap with myosin, stains light, purple in graph

H band

Myosin only without actin overlap, dark blue

Z line

Ends of sarcomere, connects actin filaments, teal

M line

Middle of sarcomere, connects myosin filaments, green

Myosin filament

Thick protein filaments that grabs onto actin and pull, heads target g-actin molecules

Actin filaments

Protein myofilament (thin), has 3 parts (tropomyosin, troponin, g-actin molecules)

G-actin molecules

Globular molecules that fit like beads on a string, two twist around to make actin filament (red)

Tropomyosin

Groove of actin filament (between actin strands) that have a different strand protein,

Troponin

Globular protein of tropomyosin that is spaced along it, what calcium binds to that. causes tropomyosin to relax, exposing bonding cite to myosin, causing contractions.

Actin bonding and calcium

Actin has binding sites for myosin heads along filament. in relaxation tropomyosin covers these binding sites so that actin and myosin do not interact. Calcium binds to troponin -> relaxes tropomyosin -> exposes binding sites on actin for myosin to bind

Muscle fiber organelles (on outside)

Nuclei, mitochondria, sarcoplasmic reticulum (SR), terminal cisterna, sacrolemma, T-tubules

Mitochondria (muscle fibers)

Some between myofibers

Sarcoplasmic reticulum

Organelle with terminal cisternae at the end stores fibers and calciums

Terminal Cisternae

At end of SR and A-band, actually store fibers and calcium

T-tubule

One between 2 TC (the ends of SR), electrical impulse propagates through line, free up impulse for calcium for contraction, has many CHAMBERS and bumps

Sarcotubular sytem

Includes Terminal Cisternae, Sarcoplasmic Reticulum, and T-tubules. Help control muscle contractions and electrical signals

Synapse

Junction between nerve/muscle, do not physically touch but filled with fluid, 1 nerve can synapse thousands of muscle fibers

Motor unit

The motor neuron and all skeletal muscle fibers it innervates (causes to move)

Ventral Root

Motor neuron with synapses at the motor end plate

Motor endplate

Folded region of muscle cell membrane (sarcolemma) that makes “contact” with motor neuron

Synaptic Bulb

Nerve impulse (electrical) in motor neuron travels down axon to this, causing the voltage gated gate to open up and let calcium into axon

Voltage gated gate

Opens in synaptic bulb after protein channel reaches threshold, lets calcium enter axon

Acetylcholine (ACH)

Released from synaptic bulb, diffuse across cleft, binds to sacroemma receptor on muscle cell, lets Na+ channels enter and K+ leaves cell, increase voltage across sarcolemma, triggers action potential

Action potential

Electronic impulse released across sacrolemma and down T-tubules once voltage threshold reached, releases calcium, binds to muscle, causes contractions

Action potential initiating contraction

T-tubules next to terminal cisternae of S.R (triad, calcium stored in SR), act as copper wiring like with calcium channels, AP causes them to open in terminal cisternae, release calcium into sacroplasm, lets it contract

Sliding filament theory of muscle contraction (calcium)

Calcium binds to troponin and undergoes conformation change, unlocks tropomyosin by pulling it off binding sites, actin-binding sites exposed to myosin heads, pulls to center and contracts, uses energy ATP → ADP; initiated by Ca++ release into sarcoplasm

Sliding filament theory (ADP and ATP steps)

Heads release ADP and bind to New ATP → heads detach from actin → heads attach to new actin binding site further along; continues as long as calcium and ATP available

ATP

From glycolysis and krebs cycle, more efficient aerobic (reserves used up first) but can be anaerobic but can result in lactic acid build up

Red vs White muscle fibers

Red has more oxygen

Creatine Phosphate (CP)

Can be used to regenerate ATP from ADP by adding phosphate group

Contracture vs Contraction

(1) muscle shortening in absence of impulse; happens because ATP runs out and filaments release actin Ca++ (2) normal muscles shorten

Rigor mortis

CONTRACTURE after death, 12-24 hours

When impulse stops…

Ca++ re-sequenced into SR terminal cisternae → tropomyosin re-shields actin → muscle relax

What do H and I band do during contraction

Get narrower as sarcomere shortens with more overlap of actin and myosin

What do H and I band do during relaxation

Slide back apart

Muscle twitch

Contraction of one motor unit (motor neuron and all muscle fibers it sends singles to)

Muscle contraction phases

Latent, Contraction, Relaxation

Latent phase

No tension or movement, cross-bridges (myosin and actin) are interacting

Contraction phase

Rising part of graph, tension developed, myosin moves actin filaments closer together, muscle fibers get shorter

Relaxation phase

Calcium released back out to SR, K leaves cell, cross bridges become inactive, tension decreases, returns to latent phase

What grades contraction strength

Frequency of stimulus and strength of stimulus

Strength of stimulus

Stimulating one motor unit leads to weak contraction, while stimulating lots makes a large contraction (number of motor units)

Frequency of contractions

Faster nerves fires the more strength you get in contractions (like with lifting heavy things), if muscle stimulated to contract before muscle has relaxed strength of subsequent contraction increases, if goes past threshold muscle twitched becomes fused in SINGLE PROLONGED CONTRACTION

Tetany

Maximum Contraction Strength

Treppe

Muscles “warm up” to max contraction state through the application of stimuli of equal intensity a few seconds apart from the muscle, each twitch slightly stringer that the pervious one, successive stimulations increase calcium concentration in sarcoplasm, can lead to fatigue if too much

Fatigue

Decrease ATP, weakens contraction; Decrease oxygen, lactic acid buildup

Cardiac Contraction

Striated with myosin and actin, has same sarcomere arrangement and sliding muscle contraction mechanism as skeletal (differs in sarcotubular arrangement and number of triads), AP originates in HEART ITSELF, sinoatrial node acts as a pacemaker by contracting at intervals, ANS controls it involuntary, intercalated discs spread action potential cell to cell, Purkkinje fibers in heart spread it very fast

Smooth Muscle Contraction

Not striated (no sacromere or bands), actin/myosin perpendicular in long cells, helps move things, more actin to myosin, has DENSE BODIES where actin attached to

Purkinje fibers

In cardiac muscle contractions (heart), spreads AP very fast

Dense bodies

In smooth muscle tissue, actin attached to the, corresponds to Z-lines of skeletal muscle, connected by proteins and surrounds myosin making contractile unit

Acetylcholinesterase

Enzyme that recycles acetylcholine by breaking it down. Important since it needs to go to away after it binds or else constant contraction

Acetylcholinesterase inhibitors

Prevents ACH from being broken down, muscle keeps contracting until runs out of ATP (muscle sparms and parasympathetic effects, death caused to to respiratory system contracting without relaxation)

Acetylcholinesterase inhibitors examples

Nerve gas, insecticides, venom, black widows, sea kraits, poison (too much Ca+)

Botulism Toxin

Cleaves specific proteins so that synaptic vesicles cannot release acetylcholine at motor endplates, leads to flaccid paralysis

Flaccid paralysis

Limp

Tetanus Toxin

Absorbed by nerves and is transported to the spinal cord, spasmodic tonic contraction of voluntary muscles by interfering with inhibitor release, constant nerve firing, spasms, cause respiratory failure