Lab 7 Abductor Digiti Minimi Muscle Contraction 2011

Lab 7 Abductor Digiti Minimi Muscle Contraction 2011 - Bio...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Bio 335 - Lab 7 Abductor Digiti Minimi Muscle Contraction 1 Abductor Digiti Minimi Muscle Contraction Craig Evinger Introduction The only reason that we have a nervous system is so that we can move. All organisms face the same problem of respiring, reproducing, and taking in energy. If energy comes to you, such as occurs for plants, you don’t have or need a nervous system. Organisms that have to go out and collect energy possess some sort of nervous system. One organism illustrating this point is a tunicate that begins life swimming in search of food has a full nervous system. When tunicates reach an adult stage and attach themselves to a rock to live out a largely immobile life, they digest most of their nervous system. I would argue that all of the things we do with our nervous system arise from the necessity of controlling movement. This lab explores some of the properties of muscles and motor units in controlling movement. You’re about to explore in a lab why you have a nervous system. Stimulating a motoneuron to produce one action potential causes one motor unit to ‘twitch’, a contraction of all of the muscle fibers of that motor unit (Fig. 1, upper left panel, red arrow). The twitch characteristics of a motor unit are measured by: 1) maximum force generated by the twitch; 2) twitch speed, the time required to achieve maximum force; 3) ½ relaxation time, time required to relax to ½ of the peak force; 4) the summation of muscle twitches with multiple motoneuron action potentials; 5) the fusion frequency, the frequency of action potentials required to produce fusion of twitches (tetanus); 6) maximum force at fusion frequency (Fig. 1, lower right panel); and 7) fatigability, the time the motor unit can maintain maximum force at fusion frequency. In this lab, you will measure some of these characteristics in the human abductor digiti minimi muscle ( ADM ) whose electromyographic ( EMG ) activity you measured in the last lab. There are two general types of motor units, Type I and Type II. The ADM has approximately equal numbers of Type I and Type II motor units. Type I motor units contract more slowly and generate less force than Type II motor units. The muscle fibers of Type I motor units contain high levels of myoglobin, but low Figure 1. Modified from Bear et al., Exploring the Brain, 3 rd ed, 2007
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Bio 335 - Lab 7 Abductor Digiti Minimi Muscle Contraction 2 levels of glycogen and ATPase. These muscle fibers are surrounded by blood vessels, whereas Type II muscle fibers are not richly vascularized. The muscle fibers of Type II motor units contain high levels of glycogen and ATPase, but low levels of myoglobin. This pattern means that Type I motor units are fatigue resistant and use aerobic metabolism, whereas Type II motor units use anaerobic metabolism and fatigue more quickly than Type I motor units. Isometric Contraction
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 7

Lab 7 Abductor Digiti Minimi Muscle Contraction 2011 - Bio...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online