SPPA 2050 Speech Anatomy & Physiology 1 Neuronal Function Goal: electrochemical communication Requirement: Electrochemical signal generation Electrochemical signal propagation Electrochemical signal transmission

SPPA 2050 Speech Anatomy & Physiology 2 Neuronal Function

SPPA 2050 Speech Anatomy & Physiology 3 Neuronal Function

SPPA 2050 Speech Anatomy & Physiology 4 Electrochemical Signal generation

SPPA 2050 Speech Anatomy & Physiology 5 Establishing Membrane Potential (V m ) Intracellular space Cell membrane Extracellular space

SPPA 2050 Speech Anatomy & Physiology 6 Establishing Membrane Potential (V m ) Na: Sodium K: Potassium Cl: Chloride Ca: Calcium +: positive ion -: negative ion

SPPA 2050 Speech Anatomy & Physiology 7 Establishing Membrane Potential (V m ) Active Transport: Na-K pump Transports 3 Na + ions out of the cell Transports 2 K + ions into the cell Net effect –Electrostatic gradient –Concentration gradient Requires energy

SPPA 2050 Speech Anatomy & Physiology 8 Resting membrane potential (V m ) V m = ~ -70 millivolts V m more positive → depolarization V m more negative → hyperpolarization

SPPA 2050 Speech Anatomy & Physiology 9 Changing V m Receptor mediated

SPPA 2050 Speech Anatomy & Physiology 10 Changing V m Voltage Gated Channels

SPPA 2050 Speech Anatomy & Physiology 11 Changing V m Physical change in permeability

SPPA 2050 Speech Anatomy & Physiology 12 Postsynaptic Potentials (EPSP & IPSP) Local Passive Graded

SPPA 2050 Speech Anatomy & Physiology 13 Summation of PSP

SPPA 2050 Speech Anatomy & Physiology 14 Temporal Summation Spatial Summation

SPPA 2050 Speech Anatomy & Physiology 15 Reaching a Threshold -70 mV epsp ipsp epsp threshold depolarization hyperpolarization Time

SPPA 2050 Speech Anatomy & Physiology 16 Electrochemical Signal Propagation

SPPA 2050 Speech Anatomy & Physiology 17 Time course ↑ depolarization (~ +100 mV) Brief (~ 1 msec) Repolarization Hyperpolarization Return to V m Other features Active All-or-none Refractory period –Absolute –Relative Action Potential

SPPA 2050 Speech Anatomy & Physiology 18 Action Potential: Propagation

SPPA 2050 Speech Anatomy & Physiology 19 Action Potential: Propagation

SPPA 2050 Speech Anatomy & Physiology 20 Action potential: Saltatory Conduction Conduction velocity Conduction velocity increased by presence of –Myelin - insulates the axon –nodes of Ranvier – AP “skips” from node to node

SPPA 2050 Speech Anatomy & Physiology 21 Clinical Note Multiple Sclerosis – a demyelinating disease

SPPA 2050 Speech Anatomy & Physiology 22 Electrochemical Signal Transmission

SPPA 2050 Speech Anatomy & Physiology 23 The Synapse Secretory potential Pre synaptic neuron Post synaptic neuron Synaptic cleft Synaptic Vesicles Neurotransmitters Receptors Neuromuscular junction

SPPA 2050 Speech Anatomy & Physiology 24 Neurotransmitters Features Excitatory Inhibitory Direct 2 nd Messenger Common NT Acetylcholine Dopamine Serotonin Glutamate GABA Glycine

SPPA 2050 Speech Anatomy & Physiology 25 Receptor Action

SPPA 2050 Speech Anatomy & Physiology 26 Synaptic Modulation: Glutamate

SPPA 2050 Speech Anatomy & Physiology 27 Clinical Note: Parkinson’s Disease Loss of dopamine Causes movement disorder Can cause dysarthria

SPPA 2050 Speech Anatomy & Physiology 28 Clinical Note: Botulinum Toxin (BOTOX)

SPPA 2050 Speech Anatomy & Physiology 29 Clinical Note: Botulinum Toxin (BOTOX) Spasmodic dysphonia Excess contraction of laryngeal muscles BOTOX temporarily paralyzes the muscles

SPPA 2050 Speech Anatomy & Physiology 30 Stretch Reflex: Simple Neuromuscular Circuit Also known as –Patellar tendon reflex –Knee-jerk reflex

SPPA 2050 Speech Anatomy & Physiology 31 Stretch Reflex: Components Sensory receptor (muscle spindle) Afferent nerve fibers CNS neurons (interneurons) Efferent nerve fibers Muscle

SPPA 2050 Speech Anatomy & Physiology 32 Stretch Reflex

SPPA 2050 Speech Anatomy & Physiology 33