An action potential travels the length of the axon and causes release of neurotransmitter into the synapse. The action potential and consequent transmitter release allow the neuron to communicate with other neurons. Neurotransmitter – A chemical released from a neuron following an action potential.
When an action potential reaches the presynaptic terminal, it causes neurotransmitter to be released from the neuron into the synaptic cleft, a 20–40nm gap between the presynaptic axon terminal and the postsynaptic dendrite (often a spine).
Neuroscientists often refer to action potentials as ‘spikes’, or say a neuron has ‘fired a spike’ or ‘spiked’. The term is a reference to the shape of an action potential as recorded using sensitive electrical equipment.
Because the electrical activity recorded by these leads is relatively small, the ECG machine amplifies [or augments] the electrical potential when recorded. These are all unipolar leads with a single positive electrode that uses the right leg for grounding
Alerting the physician to the presence of an arrhythmia while the patient is still connected to the machine may give the physician the opportunity to observe the patient while the machine is running , or immediately institute some type of therapeutic or prophylactic intervention.
Because the electrical activity recorded by these leads is relatively small, the ECG machine amplifies [or augments] the electrical potential when recorded. These are all unipolar leads with a single positive electrode that uses the right leg for grounding. The precordial, or chest, leads are ...
The purpose of this course is to familiarize the nurse with different types of EKGs and the EKG waveform and to help the nurse to identify both normal and abnormal EKG findings.
An electrocardiogram (EKG, ECG) is a record of the electrical activity of the heart. While the EKG cannot provide information about the mechanical functioning of the heart, it can demonstrate the rate and rhythm and abnormalities in conduction. Additionally, changes in
Assessing the rhythm is relatively easy and can often be determined simply by looking at the R waves on the EKG strip, but both the atrial rhythm (P to P) and the ventricular rhythm (R to R) should be assessed as they may vary with some arrhythmias. The rhythm can be assessed by counting large or small squares between waves or by using calipers or ruler to measure the distances.
2. Ventricular ejection: The pulmonic and aortic valves open, and the ventricles eject blood (ventricular systole). 3. Isovolumetric relaxation: The pulmonic and aortic valves close, the pressure in the ventricles falls, and the tricuspid and mitral valves remain closed. The atria fill (atrial diastole).
The T wave is infrequently inverted in the adult although inversions may occur in V1-V3; however, the inverted T wave may be a normal variation in children and adolescents. T wave inversion is often associated with myocardial ischemia (unstable angina, NSTEMI, sepsis, severe anemia) but is less specific than ST depression.