×
Log in to StudySoup
Get Full Access to AU - BIOL 2500 - Class Notes - Week 8
Join StudySoup for FREE
Get Full Access to AU - BIOL 2500 - Class Notes - Week 8

Already have an account? Login here
×
Reset your password

AU / Biology / BIOL 2500 / multipennate

multipennate

multipennate

Description

School: Auburn University
Department: Biology
Course: HUMAN ANATOMY AND PHYSIOLOGY I
Professor: Zachary farris
Term: Fall 2016
Tags: anatomy, and, and Physiology
Cost: 25
Name: BIO 2500 Exam 2 Lecture 8-10
Description: These notes cover the remainder of the exam 2 material as well as the beginning of muscle physiology for exam 3
Uploaded: 03/04/2017
20 Pages 180 Views 1 Unlocks
Reviews



How do muscles contract?




****Asks when/what kind of channel opens?




How do muscles contract?



BIO 2500  Pennate Muscles • Pennate – action at an angle to contraction  • Heavy load, short distance o Ex. Obliques, rectus femoris, temporalis, subscapularis,  gastrocnemius, soleus • 3 Types: o Unipennate, bipennate, or multipennate  Arrangement of Fascicles (continued) 1. Fusiform – spindle-shaped a. Ex. Biceps brachii 2. Pennate – fascicles attach to central tendon at an angle a. Unipennate i. Ex. Extensor digitorum longus b. Bipennate i. Ex. Rectus femoris c. Multipennate i. Ex. Deltoid ****Know definition, picture, and example Circular Muscles • Sphincters • Orbicularis oris, Orbicularis oculi2 Muscle Types *****Be able to identify these  Lever Systems • Muscle acting with bones that form lever systems  o Lever – rigid bar (bones) that moves about a fixed point  o Fulcrum – fixed point (joints) o Effort – force applied by a muscle on the insertion point o Load – resistance (bone itself + associated tissues)3 Mechanical Advantage  • “Power levers” o Load is closer to fulcrum than effort applied, small effort can  move large load  • “Speed levers” o Load is farther from fulcrum that effort applied, effort must be  greater than the load to move it 4 ****Know these pictures  Bone-Muscle Lever Systems • Change insertion changes mechanics  • If inserted near the point of rotation, the muscle favors speed; if distal,  it favors strength • Speed vs. Strength • Distance  First-Class Levers • Effort applied at one end of the lever • Load at the other end of the lever • Fulcrum is in between effort & load • Operate at mechanical advantage or disadvantage 5 Second-Class Levers • Effort applied at one end of lever • Fulcrum at the other end of lever • Load is in between effort & fulcrum • Always at mechanical advantage 6 Third Class Lever • Load is at one end of lever • Fulcrum is at the other end of the lever • Effort is in between load & fulcrum • Always at a mechanical disadvantage • In conclusion, differences in the positioning of the three elements  modify muscle activity with respect to speed of contraction, range of  movement, and weight of the load that can be lifted. • In lever systems that operate at mechanical disadvantage (speed  levers), force is lost but speed and range of movement are gained. • Systems that operate at a mechanical advantage (power lever) are  slower, more stable and used where strength is a priority (pg. 326)7 Muscle Physiology • There are 2 sets of intracellular tubules in skeletal muscle fibers that  are important for muscle contractions o Sarcoplasmic reticulum – smooth endoplasmic reticulum – stores and regulates Intracellular Calcium that is necessary for  contraction o Has interconnecting tubules that surround each myofibril  o Moat tubules run longitudinally along myofibril • Terminal cisternae – 2 larger tubules that run perpendicular to  myofibril at junction of A band and I band • Also associated with Sarcoplasmic reticulum are mitochondria and  glycosomes to provide energy for contraction • T (Transverse) tubules – found at each A band/I band junction, are  elongated tubes ***** • Invaginations of sarcolemma • Lumen of t-tubule continuous with extracellular space • A t-tubule runs between the 2 terminal cisternae forming the triad • Allow electrical impulses to be transmitted deep into muscle fiber and  to every sarcomere! Stimulate adjacent terminal cisternae of SR to  release Ca needed for muscle contraction!! • ***AND THEY ARE responsible for contraction of myofibrils at  virtually the same time 8 • Sarcoplasmic reticulum – stored & regulates intracellular Ca o Terminal cisternae – at each A band/I band junction • T tubules – invaginations of sarcolemma  Form  triads**1. Integral proteins protruding t-tubule into space between t-tubule and  terminal cisternae act as voltage sensors 2. Also integral proteins in terminal cisternae that form Ca channels 9 Sliding Filament Model of Contraction  1. Thin filaments slide past thick filaments a. Due to cross-bridge formation 2. The I-bands shorten 3. Sarcomeres shorten 4. H-zones disappear 5. A-bands move closer together but length is same How do muscles contract? 1. Muscle fiber stimulated by nerve ending 2. Generate & propagate electrical impulse 3. Increase in intracellular Ca • Stimulation by nerve ending causes a change in membrane potential • An electrical impulse has to be generated and propagated along the  muscle fibers  • Increase in intracellular Ca is the trigger for contraction to occur • So it takes both the nervous and the muscular system for contraction  to occur o Each muscle fiber has a single neuromuscular junction*****10 Neuromuscular Junction • Where axon terminal meets a muscle fiber • Consists of: a. Axon terminal – end of neuron o Synaptic vesicles – contain acetylcholine (ACh) b. Synaptic cleft – space between axon terminal and sarcolemma [Asks  question about this] c. Motor end plate – specialized area of muscle fiber that synapses with  axon terminal or makes contact with axon terminal  o Junctional folds – folds IN SARCOLEMMA at motor end plate  that contain acetylcholine receptors11 Channels • Channels formed from the integral membrane proteins (specifically,  transmembrane integral proteins) 1. Voltage gated channel – open when membrane potential changes 2. Chemically (Ligand) gated channel – opens when a chemical binds a. Ex. Ca or P; Na or K 3. Mechanically gated channel – opens in response to mechanical  movement  *****Be able to draw and label picture ****Asks when/what kind of channel opens? Stage 2; Voltage-gated channel *****Could switch exocytosis with endocytosis in step 312 How do muscles contract? 1. Muscle fibers are stimulated by nerve ending 2. Generate & propagate electrical impulse  3. Increase in intracellular Ca • Membrane potential – difference in electrical charge across the  plasma membrane • Resting membrane potential – at rest; ~-70 mV o Inside the cell has overall negative charge relative to outside • **Muscle & nerve cells are “excitable”, meaning they can receive and  respond to stimuli; in other words, resting membrane potential can  change!13 • Depolarization – membrane potential becomes less negative • End plate potential – initial depolarization of motor end plate • Repolarization – after a wave of depolarization passes one area, the  sarcolemma there changes permeability again & K channels open  while N channels close Action Potential • Large, transient depolarization event, including polarity reversal, that  is conducted along the plasma membrane of a muscle or nerve fiber • Action potential only generated if stimulus strong enough • Refractory period – occurs during repolarization ****Graph is always on the test Excitation-Contraction Coupling**** • Sequence of events whereby action potential propagation leads to  sliding of myofilaments o All events from stimulus to binding of myosin & actin, forming  cross-bridges14 • Action potential is generated and propagates to t-tubules and them  down the t-tubules  • AP propagates down t-tubule causes voltage sensitive proteins of t tubule to change shape, which mechanically opens Ca channels of  terminal cisternae • Calcium: more highly concentrated in Sarcoplasmic Reticulum than in  Sarcoplasm so Ca passes through the channel out of SR & into the  sarcoplasm15 THIS IS THE END OF EXCITATION CONTRACTION  COUPLING.Finally…Contraction! • Repetitive cyclical process of cross bridge formation, myosin  propelling thin filaments toward M line, and cross bridge detachment  • Requires ATP and Calcium • Hydrolysis of ATP provides energy for contraction o Myosin bridges alternately attach to actin and detach (pulls actin  myofilaments toward center of sarcomere) • Release of energy by hydrolysis of ATP powers cycling process o Hydrolysis – ATP cleaved into ADP and inorganic phosphate 16 * Myosin heads energized 1. Crossbridge formation = ATP already hydrolyzed into ADP and Pi, mysoin head attaches to actin forming cross-bridge3317 ****These pictures will be in the 3rd exam18 Relaxation**** • When the stimulus (AP from neuron) ceases: 1. Voltage-regulated channels on axon close 2. Acetylcholinesterase break down ACh in synaptic cleft 3. Ca2+ is pumped back into the Sarcoplasmic  Reticulum via active transport 4. Ca2+ unbinds from troponin  5. Myosin binding sites on actin molecules are covered by tropomyosin  (actin and myosin no longer bind) ***Know these steps Calcium*** Rigor Mortis • Muscles stiffen after death • Due to changes in Ca2+ permeability and lack of ATP synthesis after  death • Dying cells more permeable to Ca, so Ca enters cell causing cross  bridge formation19 • Also ATP synthesis stops after death, so cross bridges forming but  detachment not possible due to lack of ATP • Eventually cross bridges detach when muscle proteins begins to break  down.  Myasthenia gravis • Autoimmune disease resulting in fewer (80% fewer) ACh receptors  • Body makes antibodies to Ach receptor, so body destroys its own  receptors • Muscles weaker b/c Ach doesn’t bind to enough Ach receptors.  • Drooping eyelids • Difficulty swallowing and talking • General muscle weakness Motor Unit • 1 motor neuron and all the muscle fibers it innervates o An axon can branch and have many axon terminals, so a single  axon can innervate multiple muscle o When a motor neuron transmits AP to muscle fiber it will cause  all the muscle fibers it innervates to contract o Muscle fibers per motor unit may be just a few or more than a  hundred20

Page Expired
5off
It looks like your free minutes have expired! Lucky for you we have all the content you need, just sign up here