BIO304H5 Lecture Notes - Lecture 9: Cardiac Muscle, Pacemaker Current, Depolarization
Document Summary
No hyperpolarization because competing sodium current for. Transmit signals just in the form of graded potentials. Signals degrade over length: shorter axon helps prevent loss, therefore non-spiking neurons are smaller: otherwise they would loose current as it leaked out the membrane. Produced in result to: chemical, photo (light, receptor protein ion channels are activated by change in structure. Cant carry signal over long distance cause current is lost. Its graded: magnitude and duration is proportional to strength of stimulus: action potentials are all or none. Stronger threshold stimulus produces stronger frequency of aps. Subthreshold stimulus will not produce any aps. Graded potential decreases in magnitude as you move away. Graded potential has to be strong enough to exceed threshold from source of stimulus. High density of vg ion channels: cell body = 1 na vg channel/ mm2, axon hillock = 100-200 vg na channel/ mm2. If graded potential exceeds threshold then ap will proceed down axon.
