1Listen to the audio lecture while viewing these slidesPsychology 311Abnormal Psychology1Neurons2Psyc 311 – Abnormal PsychologySomaAxon HillockAxonTeleodendriaCollateralMyelin SheathNode of RanvierPresynaptic ElementNeurons3Psyc 311 – Abnormal PsychologyStructuresSoma or cell body• Is where cell metabolism takes place• Has places where messages from other neurons can be received called a Post Synaptic Element)• Contains many other structures related to metabolism • Mitochondria• Endoplasmic Reticulum• Golgi apparatus• Other structures•These structures are not important for this class.4Psyc 311 – Abnormal PsychologyAxons and Related Structures• Axons are structures that send information to other neurons or muscle cells.• Have many structures5Psyc 311 – Abnormal PsychologyAxon Hillock• Is at the base of the axon• Is the place where neurons decide to send a signal (called an action potential) to another neuron6Psyc 311 – Abnormal PsychologyBody of the Axon• This structure can branch (called a collateral)• Branching continues into smaller and smaller branches called Teleodendria27Psyc 311 – Abnormal PsychologyPresynaptic Element• Also called terminal buttons, terminal boutons, and other names) • We will call it presynaptic element8Psyc 311 – Abnormal PsychologyContains Several Structures• Synaptic Vesicles (sacks) • Sacks contain chemicals called neurotransmitters• Presynaptic Membrane• Autoreceptors• Reuptake channels• Receptors from other neurons• Calcium Channels9Psyc 311 – Abnormal PsychologyXXXXXXXXXXXXXCalcium ChannelsSynaptic VesiclesReuptake ChannelsAutoreceptorsPresynaptic Element10Psyc 311 – Abnormal PsychologyAxons can be one of two types• Myelinated• Myelin is a fatty covering over the axon• Helps to increase the speed of the action potential• The more myelin there is, the faster the speed of the action potential11Psyc 311 – Abnormal PsychologyNon Myelinated axons• Many axons do not have myelin• Are slower than myelinated axons• However, the fatter the axon is, the faster the action potential will go.12Psyc 311 – Abnormal PsychologyDendrites• Some neurons do not contain this structure.• only have soma’s and axons• Generally only receive information• Contain a post synaptic element• Has a post synaptic membrane• Have receptor sites to receive neurotransmitters313Psyc 311 – Abnormal PsychologyDendrites• So, both Dendrites and Soma’s can receive information. Both contain a post synaptic element.14Psyc 311 – Abnormal PsychologySynapse and Related Structures15Psyc 311 – Abnormal PsychologySynapse16Psyc 311 – Abnormal PsychologyHow Neurons Work• Based on concentration gradients of four ions• Sodium (Na), Potassium (K), Chloride (Cl), and Structures inside the axon called Anions (A)• Sodium and Potassium are positively charged and are balanced out by chloride and anions17Psyc 311 – Abnormal PsychologyHow Neurons Work• Normally some sodium leaks into the axon. • But cells don’t like sodium, so they have pumps that remove sodium called sodium potassium pumps. • The pumps remove sodium to the outside.18Psyc 311 – Abnormal PsychologyHow Neurons Work• The inside of axons have lots of potassium and anions and are negatively charged.• The outside of axons have lots of sodium and chloride and are positively charged.• So when an axon is at rest, the outside of the axon is positively charged and the inside is negatively charged.419Psyc 311 – Abnormal PsychologyWhen a Stimulus Occurs 1. When a stimulus enters a receptor on a dendrite, it causes a small electrical charge (change in polarity) on the receptor in a dendrite.2. Causes a change in the chemical concentration gradients.3. Allows sodium to enter in small amounts and thus makes the neuron more positive.4. The change from negative to positive travels down the dendrite to the soma and to the axon hillock. If the charge is strong enough, it results in an action potential.• If the charge is not strong enough, the signal stops. • Reason why it is called all or nothing 20Psyc 311 – Abnormal PsychologyWhen a Stimulus Occurs1. If the signal is strong enough, it causes sodium gates in the axon to open.2. When the gates open, sodium pours into the inside of the axon.3. Result, the axon goes from negative on the inside to positive on the inside.4. This change goes down the axon like a wave.After the sodium enters, the sodium potassium pumps turn on and begin removing sodium. 21Psyc 311 – Abnormal PsychologyWhen a Stimulus Occurs• So we have two waves going down the axon, • The sodium entering the axon• The sodium being pumped out• Ultimately the result is a negative undershoot22Psyc 311 – Abnormal Psychology+80+60+55+40+200-20-40-45-60-80MEMBRANEPOTENTIAL0 1 212345687Na GateK Gate Ca Gate9 10Action Potential23Psyc 311 – Abnormal PsychologyProcess of an Action Potential1. Stimulation Begins2.K begins to leave by passive channels. Na enters by passive channels.• Get a change in concentration gradients• Amount that leaves depends on the strength of the stimulus, temporal summation, etc.• Begins depolarization.3. If depolarization is reaches 15mV, voltage gated Na channels open.• Get Na influx4.Na K ATPases start• Removes Na and brings in K• Three Na per Two K• K also leaves through passive channels.• K voltage gated channel begins to open about ½ millisecond after Na voltage gated channels open24Psyc 311 – Abnormal PsychologyProcess of an Action Potential (cont.)5. Na voltage gated inactive channel finally closes, • Action Potential begins to fall6. K inactive gate finally closes• K is still leaving by passive channels• Na is leaving by Na K pump• Action potential continues to fall• Get a negative undershoot from resting state.7. Ca voltage gated channel begins to open8. Still do not have enough K so get Ca influx9. Finally enough K so Ca inactive channel begins to close10.Ca channel finally closed 11.Process Repeats525Psyc 311 – Abnormal PsychologyWhen the axon potential reaches the presynaptic element1. It causes calcium (Ca) to enter the presynaptic element. • Calcium causes the synaptic vesicles to bind with the presynaptic membrane • The neurotransmitter is then released into the synaptic cleft. • The neurotransmitter crosses the cleft and binds on receptors in the post synaptic element on either the dendrite or