Muscle Contraction Electrical

Experiment 5: Muscle Structure and Function

Introduction

Muscles are found almost any parts of our body. They can be classified in to 2 types (smooth muscle and striated muscle) based on their morphology and functions. The function unit of muscle cells is called sarcomere. The mechanism of all muscles’ contraction is generally the same that is based on the sliding-filament theory involving the interaction of the contractile proteins actin and myosin.

Muscles are very important in locomotion, eating process, sound production and etc. different types and patterns of electrical signals will result in different muscle contraction.

The aim of this experiment is to study the muscle contractions when applying electrical signal to a nervous system. The sciatic nerve of the frog was electrically stimulated to mimic the physiological trains of action potentials traveling down the nerve and its innervated muscle. When sciatic nerve was stimulated electrically, it depolarized and generates an action potential which passing along the nerve to gastrocnemius muscle through neuromuscular junction. Gastrocnemius muscle depolarized by the incoming electrical signal and contracted in respond. As a result, the gastrocnemius muscle that located on the upper legs of frog will contract. By adjusting the intensity and frequency of stimulation, the contraction pattern of a single twitch, temporal summation, tetanus and fatigue of muscle were examined.

Procedure

Please refer to the lab manual P.54- P.62, except

• In part C, students are not required to do single twitch.

2. P.62 Part D Step 8 = stimulate the muscle with electrode (not the clamp)

Precaution

1. Don’t touch the nerve with metal (use the glass rod instead), otherwise, no electrical current

• Rinse nerve and muscle with Ringer water regularly to keep them alive.

• Leave enough muscle for femur clamp to hold the sample.

• Don’t damage the nerve.

Result

Part A: Single muscle twitch