![Page 1: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/1.jpg)
Neurophysiology
![Page 2: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/2.jpg)
Regions of the Brain and Spinal Cord
• White matter – dense collections of myelinated fibers• Gray matter – mostly soma and
unmyelinated fibers
![Page 3: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/3.jpg)
Neuron Classification
• Structural: –Multipolar — three or more
processes (99%)–Bipolar — two processes (axon and
dendrite) (eye and olfactory)–Unipolar — single, short process –
ganglia in PNS as sensory
![Page 4: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/4.jpg)
PLAYPLAY InterActive Physiology ®: Nervous System I: Membrane Potential
Resting Membrane Potential (Vr)• potential difference (–70 mV) across the
membrane of a resting neuron• generated by different concentrations of Na+,
K+, Cl, and protein anions (A)• Ionic differences are the consequence of:– Differential permeability of the neurilemma to Na+
and K+
– Operation of the sodium-potassium pump
![Page 5: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/5.jpg)
Resting Membrane Potential
Figure 11.7
![Page 6: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/6.jpg)
Resting Membrane Potential (Vr)
Figure 11.8
![Page 7: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/7.jpg)
Changes in Membrane Potential
–Depolarization – the inside of the membrane becomes less negative –Repolarization – the membrane returns to
its resting membrane potential–Hyperpolarization – the inside of the
membrane becomes more negative than the resting potential
![Page 8: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/8.jpg)
Graded Potentials
• Short-lived, local changes in membrane potential
• Decrease in intensity with distance• Magnitude varies directly with the strength of
the stimulus• Sufficiently strong graded potentials can
initiate action potentials
![Page 9: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/9.jpg)
Action Potentials (APs)• brief reversal of membrane potential with a
total amplitude of 100 mV• only generated by muscle cells and neurons• Do not decrease in strength over distance• principal means of neural communication• action potential in the axon of a neuron is a
nerve impulse
![Page 10: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/10.jpg)
Absolute Refractory Period
• The absolute refractory period:–Prevents the neuron from generating an
action potential– Ensures that each action potential is
separate– Enforces one-way transmission of nerve
impulses
![Page 11: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/11.jpg)
Saltatory Conduction
• only at the nodes of Ranvier• Voltage-gated Na+ channels are concentrated
at these nodes• Action potentials jump from one node to the
next• Much faster than conduction along
unmyelinated axons
![Page 12: Neurophysiology. Regions of the Brain and Spinal Cord White matter – dense collections of myelinated fibers Gray matter – mostly soma and unmyelinated](https://reader033.vdocuments.us/reader033/viewer/2022051620/56649f335503460f94c50afc/html5/thumbnails/12.jpg)
Saltatory Conduction
Figure 11.16