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Physio Block-2 Gems-1
N/A
16
Physiology
Graduate
06/12/2011

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Term
Pharmacology of NMJ
Definition
Physostigimine, DFP: Inhibits
Acetylcholineesterase

AChR channel inhibitors:
tubucurarine, bungarotoxin
Term
Muscle Spindle
Definition
Primary endings: spiral terminals on
nuclear bag and nuclear chain.
Innervated by 1a fiber. Dynamic and
static response

Secondary: Spray like terminals on
nuclear chain fibers. (group 2 fibers)
Static response.

Static - muscle length
Dynamic - rate of stretch
Term
y motor neurons(gamma)
Definition
Provide motor innervation of muscle spindles.

Dynamic y motor neurons: enhance dynamic response of primary endings.

Static y motor neurons: enhance static
response of primary and secondary
endings.
Term
Golgi Tendon Organs
Definition
Supplied by afferent 1b nerve fibers


Terminals interdigitate with bundles of collagen fibers.
Term
Stretch(myotatic)
Definition
Phasic Stretch reflex: stretching the muscle quickly, detected by primary endings.(patellar tendon reflex)

Tonic Stretch reflex: slower stretch of
muscle. Important in maintenance of
posture. Group 2 afferent fibers (secondary endings)
Term
Reflex Arc
Definition
Group 1a afferent fibers from primary
endings of muscle spindles

Monosynaptic excitatory connections of these afferents with motor neruons

disynaptic inhibition pathway.
Term
Inverse myotatic reflex
Definition
Group 1b afferent fibers from golgi tendon organs, act on extensors.
Term
Troponin Complex
Definition
Troponin T: attaches troponin complex to tropomyosin

Troponin I binds to actin and inhibits contraction.

Troponin C: binds to Ca++, promotes
movement of tropomyosin on actin
filament casing myosin binding sites
to be exposed.
Term
Thick Filament
Definition
Essential light chain: stabilizes
myosin head region

Regulatory light chain: can be
phosphorylated and regulates ATPase
activity.
Term
Sarcomere Structure
Definition
Z-disc: Zigzag protein that serve as attachment for thin filaments

I Bands: region occupied only by thin filaments

H zone: Central region occupied by just thick filaments

M line: proteins that anchor thickfilaments
Term
Alignment of Sarcomere
Definition
Titan: stabilizes position of contractile filaments. returns contracted sarcomeres to resting length

Nebulin: Inelastic, attaches to Z-disc
Lies along and helps align actin
filaments
Term
Cross Bridge Cycle
Definition
State A: resting state. Partially hydrolyzed ATP. stabilizes cocked position

State B: Exposure of binding sites allows myosin heads to bind. Releases ADP and Pi

State C: Power stroke. Pulls actin toward center of sarcomere

State D: binding of ATP to myosin decreases affinity of myosin for actin.
Term
Length-tension relationships
Definition
Optimal Length 2.0um to 2.3 um

Too long and not many cross bridges will form.

Too short: thick filaments run into Z discs and myosin can't find new binding sites.
Term
Length-Force relationships
Definition
The force-length relationship depicts a steady state behavior that exists between initial sarcomere length, and force that can be generated.

Passive tension: Elastic recoil of cytoskeleten

Total tension: force from myosin/ actin plus passive tension.

Active Tension: The difference between total tension and passive tension.
Term
Recruitment of motor units
Definition
Neurons with lowest thresholds are type 1
slow twitch

Next is Type IIa fibers

Highest thresholds activate Type IIB
Term
Summation of twitches
Definition
Unfused Tetanus: stimulation is not at maximum value, muscle fiber relaxes slightly between stimuli.

Complete tetanus: Stimulation is fast
enough and fibers do not relax.
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