DOC PREVIEW
UT Knoxville BCMB 230 - Skeletal Muscle
Type Lecture Note
Pages 4

This preview shows page 1 out of 4 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 4 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 4 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

BCMB 230 1st Edition Lecture 13 Outline of Last Lecture I.Components of the Inner EarII.ChemosensesIII.Looking at the EyeIV.MusclesOutline of Current Lecture I.Contraction of Skeletal MuscleII.Cross Bridge CycleIII.Muscle Twitch ResponseIV.RelationshipsV.Skeletal Muscle ATP ProcessVI.FatigueVII.Controlling ContractionCurrent LectureSkeletal MuscleI. Contraction of Skeletal Muscle-use a somatic motor neuron-action potential travels down neuron -Ca2+ enters voltage-gated channels-Acetylcholine is released-an action potential is created in the muscle cell (all or none; no graded potential-this is only in neurons)-action potential follows the T tubules which have a DHP receptor-DHP receptors are associated with protein in the sarcoplasmic membrane-membranes are so close together that they interact with each other-DHP receptor responds to action potential and pulls on the ryanodine receptor (on the sarcoplasmic reticulum)-ryanodine receptor is also a Ca2+ channel; opens up and Ca2+ is released into the cytoplasm-Ca2+ binds to troponin which moves tropomyosin out of the wayThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-tropomyosin no longer blocks the binding sites (actin) so a myosin cross bridge is formed-get a repetitive action called a cross-bridge cycle, which is the key to muscle contraction-voltage-gated calcium channels—ones we look at on the synaptic bulb-both DHP receptor and Ryanodine receptor are in the family in voltage-gated calcium channels but they are NOT voltage-gated calcium channels-DHP is voltage-gated but not a calcium channel-Ryanodine is a calcium channel but is not voltage-gatedII. Cross Bridge Cycle Four steps:1. Make a cross bridge-bond between actin and myosina. When bonding, ADP and phosphate come off which initiates a shape change (a little bit of sliding, relative movement)2. Move cross bridge3. Break cross bridgea. ATP binds to myosin and breaks the cross bridgeb. Myosin ATPase activity-not actually phosphorylating the myosin4. Re-energize myosina. Breakdown ATP—goes back to energized form (where you first started)Signal to start cross bridge cycling: calcium. As long as there is calcium in the cell, this process repeats itself.Two roles of ATP: break the bond and energize the myosin-ATP is not used up; need a different ATP for the calcium pumpIII. Muscle Twitch ResponseHave a single stimulus on an isolate muscle-latent period-for first few milliseconds, seemingly nothing happens; see no change-contraction period-time period of rapidly increasing tension -relaxation period-gradually decreasing tensionMore cross-bridges you have, the more tension you haveQuestion to think about: Why is isometric twitch contraction graph not symmetrical, why does ittake less time to get the contraction than relaxation?IV. RelationshipsFrequency-Tension RelationshipsTreppe-little bit of increase in tension with repeated stimulation even if you let it completely relax-this is due to a change in conditions-change temperature, change ion availabilityUnfused tetanus-stimulate muscle before it is completely relaxed, get another muscle twitch-getan additive effect-get a little more contraction because of stimulating it before you let it relax-faster frequency of stimulationFused tetanus-put a stimulus in the contraction period and never let it relaxCramps-uncontrolled reaction that could occur because of an unbalanced ion concentration-increase circulation to balance ion concentrationLength-Tension Relationship-a stretched sarcomere has decreased tension-amount of overlap between actin and myosin is reduced-decreases tension produced-optimal length is the best overlap of actin and myosin-skeletal muscle is attached to the bone, so most skeletal muscle is at optimal lengthLoad –Velocity Relationship-as the load gets heavier, the muscle contracts slowerV. Skeletal Muscle ATP ProcessesMuscle contraction requires energy.-energy comes from ATP which drives the cross-bridge cycle-we don’t store ATP, we have to make it up all the time-muscles have a new way of making ATP-have creatine phosphate—add an ADP and make ATP and creatine-creatine becomes a waste byproduct-run through oxidative phosphorylation, Krebs Cycle, Glycolysis-make ATP and carbon dioxide-can do this aerobic respiration as long as we have oxygen-also possible to go into anaerobic respiration—produces lactic acid-run out of ATP-cross bridge becomes locked-only see this after deathVI. Fatigue-fatigue-protective mechanism that helps keep us from running out of ATP-with fatigue-get a reduced response for the same stimulus-changed the conditions in some way1. lactic acid buildup-happens when forced into an anaerobic situation and there is a high demand for ATP-can only use this for a short amount of time2. cross bridge inhibition-have ADP buildup which changes affinity of ADP binding site; ADP stays on myosin longer so a cross bridge is not produced 3. conduction failure-T-tubules are more susceptible to ion imbalances because there is less cellular fluid in them; action potential does not reach DHP receptor; long buildup, long recovery4. central command fatigue: failure to stimulate motor neuron appropriately so not enough acetylcholine released; ex. being tired but then changing the situation so you are no longer tiredVII. Controlling ContractionMotor unit-somatic motor neuron plus multiple muscle cells-each muscle made up of hundreds/thousands of motor units-level of contraction depends on number of motor unitsMuscle recruitment-add more motor units if you don’t have enough on hand to do the action (or take motor units away)Three major types of skeletal muscle cells-largely dependent on two enzymes (two versions):-myosin ATPase activity-low-slow contracting fiber-high-fast contracting fiber-influence speed of contraction, the way muscle is hooked to the bone (give more speed or give more strength)-load-arrangement of muscle with bone-glycolytic enzyme activity-glycolysis or oxidative


View Full Document

UT Knoxville BCMB 230 - Skeletal Muscle

Type: Lecture Note
Pages: 4
Download Skeletal Muscle
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Skeletal Muscle and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Skeletal Muscle 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?