Lecture 4: The Nervous System - PDF

The nervous system -- continue X.Liu PSYC2190 First Exam 8:45 am Sharp, 10 Feb 2024 Optional online review session: 8:00 pm, 9 Feb X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 Presynaptic Events...

The nervous system -- continue X.Liu PSYC2190 First Exam 8:45 am Sharp, 10 Feb 2024 Optional online review session: 8:00 pm, 9 Feb X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 Presynaptic Events X.Liu PSYC2190 In the Synaptic Cleft X.Liu PSYC2190 Postsynaptic Events Neurotransmitter molecules fit the binding sites of receptors like keys fit into locks. Neurotransmitter binding conveys the neural message to the postsynaptic cell. X.Liu PSYC2190 Ionotropic Receptors The ion channel opens when a molecule of a neurotransmitter attaches to the binding site. For purposes of clarity the drawing is schematic; molecules of neurotransmitters are actually much larger than individual ions. X.Liu PSYC2190 Ionic Movements During Postsynaptic Potentials X.Liu PSYC2190 Metabotropic Receptors When a molecule of neurotransmitter binds with a receptor, a chain of chemical events is initiated. The end result of the chain of events is to indirectly open an ion channel or produce another intracellular change in the cell. X.Liu PSYC2190 Activation of Receptors X.Liu PSYC2190 Termination of Postsynaptic Potentials Termination by Two Mechanisms Reuptake: an extremely rapid removal of a neurotransmitter from the synaptic cleft by the terminal button Enzymatic deactivation: accomplished by enzyme that destroys molecules of the neurotransmitter Acetylcholinesterase (AChE) deactivates acetylcholine (ACh) X.Liu PSYC2190 Termination of Postsynaptic Potentials X.Liu PSYC2190  Neurotransmitters and drugs Some Examples X.Liu PSYC2190 Psychoactive Drugs alter mood, thought, or behavior used to manage neuropsychological illness. have an effect on the brain. X.Liu PSYC2190 Psychoactive Drugs To be psychoactive, the drug must reach and influence the nervous system Not all drugs are psychoactive because of the BLOOD BRAIN BARRIER X.Liu PSYC2190 The Blood–Brain Barrier Small molecules such as oxygen and CO2 are not ionized and are fat soluble – can pass right through. Glucose, amino acids and other components can be carried across by ACTIVE TRANSPORT SYSTEMS. It is like a pump. BB Barrier halts more substances than it lets through… X.Liu PSYC2190 Why Have a Barrier Electrical activity of neurons depends upon rather precise extracellular concentrations of ions. If ions could cross freely, would upset the balance. Protects from toxic and infectious substances X.Liu PSYC2190 A Clinical Example Treating Parkinson's disease Dopamine Small enough Chemical composition is wrong - not lipid soluble L-DOPA Slightly different composition Can pass through active transport X.Liu PSYC2190 Effects of Psychoactive Drugs Mostly at the synapses Increase effectiveness - AGONIST Decrease effectiveness – ANTAGONIST Stimulate the release of Dopamine Block the reuptake of Dopamine Block the inactivation of Dopamine All are Dopamine agonists X.Liu PSYC2190 Alcohol as an Example X.Liu PSYC2190 Alcohol: A Tale of Two Neurotransmitters Glutamate Excitatory NT: When active, encourages APs, increases firing Widespread throughout the brain GABA Inhibitory NT: When active, inhibits APs, decreases firing Also widespread throughout the brain Alcohol affects both Alcohol prevents glutamate from acting (antagonist) Alcohol makes GABA even more inhibitory (agonist) Biggest effect in frontal brain regions Impulse control, decision making, memory… X.Liu PSYC2190 GABA - Major inhibitory NT of CNS Influences chloride channels Excitation of the receptor by GABA produces an influx of Cl- ions Influx of Cl- increases the concentration of negative charges on the inside of the cell membrane Hyperpolarizing it and making it less likely to propagate an action potential. X.Liu PSYC2190 Alcohol Acts like GABA Produces greater inhibition in CNS. Not as quickly reabsorbed as GABA – long lasting X.Liu PSYC2190 Rohypnol (Roofies) + Alcohol = Very Bad Rohypnol is a benzodiazepine that is used in the short-term treatment of insomnia and as a sedative-hypnotic medication. X.Liu PSYC2190 X.Liu PSYC2190 X.Liu PSYC2190 Another Example -- where does the “high” come from? X.Liu PSYC2190 The “Reward” Circuit When dopamine is released, feeling of pleasure/satisfaction Natural rewards or “drives” Food, sex, thirst Less natural drives play on this system, too Gambling Drugs X.Liu PSYC2190 A “Natural High” We have natural opiate receptors that serve a natural painkilling role under circumstances of extreme pain. Ordinarily, GABA actively inhibits Dopamine release. pink = dopamine receptor blue = dopamine (released from neuron on left) X.Liu PSYC2190 Heroin When an NT binds to an opiate receptor Decrease in GABA More dopamine released Heroin mimics very effectively, too effectively Other opiate-like drugs – opioids oxycodone (OxyContin), hydrocodone (Vicodin), methadone, Fentanyl X.Liu PSYC2190 X.Liu PSYC2190 Cocaine Also works on Dopamine receptors. Inhibits reuptake of dopamine from the synaptic cleft into the pre-synaptic axon terminal X.Liu PSYC2190 Cocaine Also works on Dopamine receptors. Inhibits reuptake of dopamine from the synaptic cleft into the pre-synaptic axon terminal X.Liu PSYC2190  The Nervous System on a Large Scale X.Liu PSYC2190 The Structure of the NS Two basic divisions: Central nervous system (CNS) Brain and spinal cord Peripheral nervous system (PNS) Outside the brain and spinal cord CNS communicates to the rest of the body via nerves X.Liu PSYC2190 The Central and Peripheral Nervous Systems X.Liu PSYC2190 Nerves A nerve consists of a membrane sheath encasing bundles of axons. Several (or millions of) axons running together outside the brain Inside the brain…referred to as a TRACT X.Liu PSYC2190 Anatomical Directions X.Liu PSYC2190 X.Liu PSYC2190 X.Liu PSYC2190 X.Liu PSYC2190 X.Liu PSYC2190 Examples dorsolateral prefrontal cortex ventromedial hypothalamus X.Liu PSYC2190 2d --> 3d X.Liu PSYC2190 Surface Features Meninges (not Mannings!) Tough material that covers the brain Three layers of meninges Dura mater is the outer layer Arachnoid membrane is the middle layer Pia mater is around every surface (they P.A.D. the brain…) Gap called the subarachnoid space, filled with cerebrospinal fluid (CSF) X.Liu PSYC2190 Three layers of meninges Dura mater is the outer layer Arachnoid membrane is the middle layer Pia mater is around every surface (they P.A.D. the brain…) Gap called the subarachnoid space, filled with cerebrospinal fluid (CSF) X.Liu PSYC2190 Meninges X.Liu PSYC2190 https://youtu.be/UkffBv4sh4U X.Liu PSYC2190 Ventricles & CSF Ventricles, a series of hollow, interconnected chambers Produce and contain the CSF X.Liu PSYC2190 Brain is fragile Brain is very soft and jellylike Needs protection Around the brain… Bath of Cerebrospinal Fluid Shock absorption Reduces net weight, less pressure on base X.Liu PSYC2190 Concussion and CTE Chronic Traumatic Encephalopathy (CTE) a brain condition thought to be linked to repeated head injuries and blows to the head. It slowly gets worse over time and leads to dementia. X.Liu PSYC2190 https://youtu.be/VB1Bos0LUnE X.Liu PSYC2190 Concussion and CTE Chronic Traumatic Encephalopathy (CTE) a brain condition thought to be linked to repeated head injuries and blows to the head. It slowly gets worse over time and leads to dementia. X.Liu PSYC2190 https://youtu.be/GyatkcVn9xo X.Liu PSYC2190 Resting Potential & Action Potential X.Liu PSYC2190  Resting Potential & EPSP Action Potential IPSP X.Liu PSYC2190  Resting Potential & EPSP Action Potential Synaptic IPSP Transmission X.Liu PSYC2190  Resting Potential & Neurotransmitter EPSP Action Potential Synaptic IPSP Transmission Drug Effects Millions of such loops NS at large scale (CNS, PNS) X.Liu PSYC2190  Resting Potential & Neurotransmitter Sensory System EPSP Synaptic Motor Action Potential Drug Effects IPSP Transmission System X.Liu PSYC2190 https://youtu.be/XujOMf2hlRA X.Liu PSYC2190 Homework Read the chapters about brain structure and fill in the blanks on the handout. Make sense of the song. X.Liu PSYC2190