Muscle Function and Electromyography

Muscle Function and Electromyography

• Muscles maintain electrical potentials across cell membranes, which are a form of stored energy.
• Activation, like a nerve impulse, allows ions to cross muscle cell membranes, generating electrical activity that causes muscle contraction.
• Electromyography (EMG) is a graphical recording of electrical activity within muscles.
• EMG is useful in diagnosing disorders affecting muscles and their supplying nerves.

Applications of Electromyography

• EMG studies help diagnose disorders of muscles and nerves, like muscular dystrophies, Huntington’s disease, and diabetic neuropathy.
• EMG also investigates normal muscle function, analyzing electrical activity in muscles during movements like forearm extension.

The Experiment: Analyzing Forearm Extensor Muscle Activity

• Purpose: Examine the differences in muscle activity when the hand position is changed.
• Materials: Chromebook/computer, Graphical Analysis 4 app, Go Direct EKG, electrode tabs, ruler, and a weight.
• Procedure:
  • One person is selected as the subject, ensuring no hand, wrist, forearm, or elbow conditions.
  • Set up the Go Direct EKG with the EMG Rectified channel in Graphical Analysis 4.
  • Three electrode tabs are placed on the dominant arm:
    • two on the dorsal forearm, 5 cm and 10 cm from the lateral epicondyle.
    • one on the upper arm.
  • EKG clips are connected to the tabs, with red/green on the forearm and black on the upper arm.
  • Subject stands with fingertips resting on the table, palm facing up and forearm in line with the palm.
  • Stable baseline is recorded for 5 seconds, then the subject extends their hand as far as possible for 5 seconds.
  • Subject relaxes the hand back to the starting position for another 5 seconds, repeating the cycle.

Understanding Lateral Epicondylitis

• Lateral epicondylitis (tennis elbow) is inflammation of the tendons at the elbow.
• It results from repetitive gripping motions, commonly between the thumb and first two fingers.
• This experiment examines how muscle activity changes with hand position, potentially relating to conditions like tennis elbow.

Introduction to Electrocardiography

• An electrocardiogram (ECG or EKG) is a graphical recording of the heart's electrical activity.
• The sinoatrial node, the heart's natural pacemaker located in the right atrium, initiates an electrical sequence.
• This impulse travels through the atria via conduction pathways to the atrioventricular node, then to both ventricles.
• This process ensures coordinated contraction of the atria and then the ventricles.
• Each electrical event creates unique deflections on the EKG, providing insights into heart function and health.
• The placement of electrodes on the chest and extremities enables the electrical activity to be viewed from various angles.
• A positive deflection on the EKG indicates electrical activity moving towards the active lead.
• Five components of a single heartbeat are labeled P, Q, R, S, and T, each representing a specific electrical event.

EKG Components

• The P wave signifies the initiation of the electrical journey as the impulse spreads from the sinoatrial node through the atria and to the ventricles.
• The QRS complex represents ventricular activation.
• The T wave represents the ventricular repolarization, the recovery of the ventricular muscle tissue to its resting state.
• The length of each interval in the EKG can provide information about the electrical pathway.

Abnormal EKG Patterns

• Abnormalities in the EKG can signify heart disorders such as slow heart rate, fast heart rate, irregular rhythms, injury to muscle tissue, and death of muscle tissue.
• A long interval suggests a slowed impulse or a longer pathway.
• A short interval implies an impulse following a shorter route.
• An absent complex indicates a blocked electrical impulse or the absence of normal depolarization.
• An absent P wave signifies a lack of normal atrial depolarization.
• An absent QRS complex following a normal P wave indicates a blockage before the electrical impulse reaches the ventricles.
• Abnormally shaped complexes indicate abnormal impulse spread through the muscle tissue, such as in myocardial infarction.

EKG Applications

• EKGs are used to diagnose and monitor various heart conditions.
• The analysis of EKG waveforms helps doctors identify abnormalities and monitor the effectiveness of treatments.
• Physicians can use EKGs to assess the health of the heart, diagnose heart conditions, and manage cardiovascular disease.

Myocardial Infarction (Heart Attack)

• A myocardial infarction is a serious condition where the heart muscle is damaged by a lack of blood flow.
• This often results in abnormal EKG patterns due to the impaired electrical activity in the damaged area.
• EKGs are crucial for diagnosing myocardial infarctions and guiding treatment decisions.

Explore the role of muscles in generating electrical activity and the significance of Electromyography (EMG) in diagnosing muscle disorders. This quiz covers the fundamentals of muscle function, applications of EMG, and the experiment analyzing forearm extensor muscle activity. Test your knowledge on how muscle activity varies with hand position.