Psychology 100 Biological Foundations Lecture 3 PDF

Psychology 100: Biological Foundations  Where is the Mind? Ar ist o tle H i p p o c ra t e s The mind is in the heart! The mind is in the brain! Phrenology Phineas Gage (c. 1848)  Touch Movement Perception...

Psychology 100: Biological Foundations  Where is the Mind? Ar ist o tle H i p p o c ra t e s The mind is in the heart! The mind is in the brain! Phrenology Phineas Gage (c. 1848)  Touch Movement Perception Thinking, Planning & Morality Vision FRONT Language (typically on left) Fine Memory Motor Vital & Emotion Control Hearing Functions  Neurons & Neurotransmitters  Neurons 1. Contains the cell nucleus and all of the material that the neuron needs for its life processes S o ma (“cell body”) 2.Processes that Dendrites serve to receive incoming signals from other neurons A xo n 3. (inside the Axon 4. myelin Terminals sheath) M ye l i n Sites of Process that sheath neurotransmitter transmits a signal to (fatty synthesis and insulation) another neuron release (e.g., (typically covered in chemical a fatty substance transmission to called myelin) other neurons)  Voltage A Neuron at ‘Rest’ Oscilloscope Recording Electrode -70 mV Dendrites Cross-section through axon Neuron Membrane Inside the Axon Outside the Axon " " " " "" " " " " "" " " " " "" ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! !! ! " """ """" " !" " " " "" "!"" " "!""! "" ! ! ! !! ! ! ! "! " "" ""!""" """"! "" !" """" "" " ! ! ! !! ! ! ! """""" ! " " " """" """ !"""!" !" Axon Cell body ! ! ! ! !! ! ! ! " " " """"!""! "!" ! ! ! !"!"! ""! " " " " " " "" ! ! ! !!! ! " "" !" !" " """ "!" " ""! "" " " """ " ! ! ! ! !! ! " "" " !" ! "! " ! " "" " """"" " " " Terminal !! ! ! ! ! ! ! !! ! ! ! ! ! ! !! ! ! ! ! !! ! ! ! ! !! ! ! ! ! !! ! ! ! " " " " "" " " " " "" " " " " "" Axon hillock Axon At rest, the inside of a neuron is negatively charged relative to the outside; in this state, the neuron is said to be polarized  The “Resting Potential” Why is the inside of the neuron negatively charged (relative to the outside)? The resting potential is maintained by a balance between 2 physical forces: – The Force of Dif fusion: Between areas of different concentration; particles want to evenly distribute (move from higher to lower concentration) – The Electrostatic Force: Between charged particles; differently charged particles (e.g., positive and negative) are attracted to each other  Ions Across the Membrane + (in a Neuron at Rest) High Low Concentration Outside of the Concentration Cl- Na+ Neuron Force of Diffusion Electrostatic Force K+ Force of Diffusion Electrostatic Force Electrostatic Force Force of Diffusion Low - Concentration Negatively Cl- Na+ charged Inside of the proteins K+ At rest, the only ion that feels These can not High compelled to move across the Neuron leave the neuron (e.g., they are too big! Concentration membrane by both forces is Na+!  Types of Ion Channels in a Neuron’s Membrane Cell Membrane Ligand of the Neuron Binding site Closed ion Open ion channel channel “Voltage-gated” “Ligand-gated” ion channel These channels are normally ion channel closed, but they open at a These channels open when a specific membrane potential specific chemical messenger binds to them. (e.g., a specific voltage). “Leaky” ion channel These channels are slightly permeable to ions at all times.  Creating the Resting Outside Membrane Potential of the Neuron Low Concentration Cl- Na+ + Electrostatic Force Force of Diffusion Force of Diffusion High Electrostatic Force K+ Concentration K+ LEAKY LEAKY Electrostatic Force Force of Diffusion − Electrostatic Force Force of Diffusion Cl- Na+ Negatively charged Voltage-gated Na+ and K+ proteins K+ channels are closed Inside These can not leave the neuron K+ (inactive) at the of the (e.g., they are Neuron too big! High resting potential! Concentration  The Sodium-Potassium Transporter (a.k.a. the “Sodium-Potassium Pump”) Outside Neurons Are Constantly Pumping Na+ Three Na+ Na+ ions are of the Neuron Na+ + Na+ Ions Out of the Cell! pumped out Neurons use an enormous amount of energy to move sodium against its − + ATP gradients and to maintain ‘rest’! Inside (cellular of the energy) K+ Two K+ ions Neuron K+ are pumped in  + Na+ (versus a neuron at rest) A neuron A Toilet at Rest! at ‘rest’ is ful l of pot ent i al - energy, Na+ just like a full toilet! A Mouse Trap at ‘Rest’! Energy is energy! Neurons Communicate With Other Neurons!  The Action Potential The neuron remains at rest (e.g., remains polarized) until it is “excited” by other neurons If a neuron is excited enough by other neurons, a threshold of excitation is reached – At threshold 1) Na+ ion channels open and 2) Na+ ions begin to flow into the neuron As Na+ ions rush into the neuron, the neuron becomes depolarized – More positive on the inside relative to the outside This initial depolarization begins a chain of events called the action potential  Initiating the Action Potential Outside (It’s all about sodium!) of the Na+ Low Concentration Cl- Neuron Electrostatic High Na+ Diffusion + Force of Force Electrostatic K+ Diffusion Force of Concentration Force Na+ Na+ Na+ LEAKY LEAKY - Electrostatic Cl- Na+ Diffusion Force of Force Na+ Na+ Negatively charged Voltage-gated sodiumNa+ + + NaNa Na+ Na+ Inside proteins K+ channels OPEN at theNa+ Na+ Na+ of the These can not High threshold of excitation Neuron leave the neuron Concentration Na+ Na+ (e.g., they are (and sodium enters)! too big! Na+ A Toilet at Threshold! The toilet (versus a neuron at threshold) Na+ + does not flush until the handle is pu s h ed, but once it’s pushed Na+ - enough the valve opens and the water flows into the bowl! A Mouse Trap at Threshold! The trap will spring only when there’s sufficient pressure on the cheese!  The Action Potential: Sodium vs. Potassium K+ K+ Outside Low K+ K+ of the Concentration Cl- Na+ K+ Neuron K+ + K+ High K+ Electrostatic Electrostatic Diffusion Force of Diffusion Force of Force Concentration Force K+ Na+ LEAKY LEAKY K+ - Electrostatic Voltage-gated potassiumNa+ Na+ Diffusion Force of Electrostatic Cl- Force Diffusion Force of Force Negatively channels open a fraction Na+ + Na+ charged K of a second after sodium + Na K+ Inside proteins High channels open Na+ of the (and potassium leaves, driven out Concentration These can not by the accumulation of positively Neuron leave the neuron (e.g., they are charged Na+ inside the neuron) too big!  The Action Potential Resting (in Real Time) – Optional! Potential Action Potential Return to Resting Potential Membrane Potential (millivolts) Na+ rushes Sodium channels into the close neuron The “sodium-potassium (depolarizing ion Re p K+ rushes pumps” work to restore a r i z at the cell) out of the ola neuron the resting potential r iza (see slide #13) D ep o l (repolarizing Sodium tion the cell) channels Potassium channels open open Threshold of Excitation Polarized “Refractory Period” Resting Potential Time (milliseconds) The resting potential is restored by actively pumping Na+ out and K+ back in! Movement of the Action Potential Excitatory signals from neighboring neurons The opening of sodium 1. channels at the axon hillock initiates the action potential! (There’s a large concentration of voltage-gated sodium channels in this region) Na+ + + Action potential NaNa Na+ Cell body D De Dep Depolarized ep epola ola l riz riz ri i ed Depolarizeded Still polarized Polarized Polarized Still polarized NaNa Na+ + + +++++ + ----- ----- Na+ (Na flows in) 2. As Na+ ions enter the neuron, the region of the axon closest to the axon Excitatory signals hillock becomes from neighboring neurons depolarized Movement of the Action Potential 3. As positive current spreads inside the axon, the next segment of the axon depolarizes (e.g., enough to reach threshold and initiate a new action potential!) Na+ Na+ Action potential Na + Na+ Repolarizing Depolarized Polarized - - - - -NaNaNa +++++ ----- + + + Na+ (Na+ flows in) 4. Previously depolarized regions of the axon repolarize (e.g., they return to the resting potential or “re-set”) Movement of the Action Potential And so on…the action 5. potential flows all the way down the axon to the axon terminals Na+ Na+ Action potential Na+ Na+ Polarized Repolarizing Depolarized ----- ----- Na+ Na+ +++++ Na+Na+ (Na+ flows in) Flow of positive current Once the action potential starts it does not stop!  Neurotransmitters As the action potential arrives at the axon terminal, it opens calcium (Ca2+) ion channels – This allows Ca2+ to flow into the terminal The entry of Ca2+ ions into the terminal triggers the release of chemical messengers called neurotransmitters Neurotransmitters diffuse across the synapse to interact with receptors on the postsynaptic membrane – These receptors are associated with ion channels!  The Synapse & Synaptic Transmission “Presynaptic Pre- synaptic neuron Action potential When the action potential reaches its terminal (end bulb) at the pre-synaptic Neuron” (sending neuron) Vesicle neuron, calcium (Ca2) ion channels open, flooding (sends the containing the terminal with calcium neurotrans- ions. The terminal vesicles mitters Ca2+ open, spilling neurotrans- signal) Action potential Ion mitter molecules into the synapse. channel Post- Some of these neurotran- “Postsynaptic synaptic neuron (receiving mitter molecules bridge the synaptic gap and bind to specialized receptors in Synaptic Neuron” neuron) gap the dendrites of the postsynaptic neuron. (receives the Receptor sites on receiving signal) neuron After neural transmission has occurred, most of the neurotransmitter molecules are reabsorbed by the pre-synaptic neuron Presynaptic (reuptake) or are converted by enzymes into inactive Neuron chemicals. The synapse is a physical space between Synapse Synaptic gap Diffusion of neurons where synaptic Na + neurotransmitters transmission (e.g., Neurotransmitter across the synapse (and communication from Receptor Ion channel binding to postsynaptic one neuron to another Postsynaptic receptors) neuron) takes place Receptor Neuron  A ct io n Po t en tia l https://www.youtube.com/watch?v=dSkxlpNs3tU  P re s y n a p t i c Neuron Ac tio nP ot Terminal en Synaptic tia l Vesicles Ions (in blue) Ca2+ Neurotransmitters (in red; released into the synapse) Receptors Postsynaptic Neuron (closed)  P re s y n a p t i c Neuron Terminal Ions Neurotransmitters (in red; bound to receptors) Receptors Postsynaptic Neuron (open!)  P re s y n a p t i c Neuron Terminal Ions Ion Flow! Postsynaptic Neuron (into postsynaptic neuron)  Postsynaptic Effects The binding of neurotransmitter to receptors on the postsynaptic neuron causes ions to flow into (or out of) that neuron Ion flow creates 2 types of changes in the postsynaptic neuron’s level of excitability: – Excitatory postsynaptic potentials (EPSPs) – these are changes that depolarize the neuron (make it more excited and an action potential more likely) – Inhibitory postsynaptic potentials (IPSPs) – these are changes that hyperpolarize the neuron (make it less excited and an action potential less likely)  Classical Neurotransmitters Glutamate Major excitatory neurotransmitter in the brain and spinal cord; always excitatory GABA Major inhibitory neurotransmitter in the brain; always inhibitory Dopamine Involved in arousal, pleasure, reward; generally excitatory Norepinephrine Involved in arousal, fight or flight, stress; generally excitatory Serotonin Involved in arousal, mood, sleep, appetite; can be excitatory or inhibitory Acetylcholine Involved in arousal, sleep, muscle movements, learning & memory; generally excitatory  Glutamate vs. GABA Glutamate makes neurons more excited by binding to receptors that open sodium (Na+) ion channels, allowing more positive current to flow into the receiving neuron (creating EPSPs) GABA makes neurons less excited by binding to receptors that open chloride (Cl-) ion channels, allowing more negative current to flow into the receiving neuron (creating IPSPs)  The Glutamate Receptor Cl- Na+ Cl- Glutamate Synapse Glutamate binding site on the receptor Na+ Na+ Cl- Cl- Na+ Cl- Na+ Na+ Na+ The glutamate Na+ Postsynaptic receptor is a l i ga n d - gat e d Neuron ion channel (it opens only when glutamate binds to it) Cl- Na+ Na+ Na+ Na+ Na+ Glutamate depolarizes neurons! (it makes them more positive on the inside)  The GABA Receptor Cl- Na+ Cl- GABA Synapse GABA binding site on the receptor Na+ Na+ Cl- Cl- Cl- Na+ Na+ Na+ The GABA Cl- receptor is a Postsynaptic l i ga n d - gat e d Neuron ion channel (it opens only when GABA binds to it) Cl- Cl- Cl- Cl- Cl- Cl- GABA hyperpolarizes neurons! (it makes them more negative on the inside)  + D ep o l a r i ze d Excitation Threshold Influx of The influx of positively charged Excitatory Na+ ions sodium ions makes the neuron Transmitters EPSPs more excited & more likely to (e.g., glutamate) reach threshold POLARIZED (Negative Resting state) Influx of Inhibitory Cl_ ions The influx of negatively charged Transmitters IPSPs chloride ions makes the neuron more inhibited & less likely to (e.g., GABA) - reach threshold H y p e rp o l a r i ze d  A Neuron’s Only ‘Decision’ Neurons receive inputs from both ‘excitatory’ neurons (that produce EPSPs) and ‘inhibitory’ neurons (that produce IPSPs) EPSPs and IPSPs are added together in the postsynaptic cell as they travel toward the axon hillock If the sum of EPSPs and IPSPs at the axon hillock is greater than the threshold of excitation, then an action potential will be triggered If it is not greater, then nothing will happen! The action potential is “all-or-none”!  Here, the neuron is only receiving excitatory i nput Axon Excitatory Hillock EPSP Neurotransmitter Glutamate ACTION Release of glutamate If the axon hillock reaches POTENTIAL! creates EP SP s (RED) in the threshold of excitation, then an action potential will postsynaptic neuron be generated In this scenario, the neuron’s threshold of excitation is reached, and the neuron fires an action potential!  Inhibitory Release of GABA creates Neurotransmitter IP SP s (BLUE) in the postsynaptic neuron GABA Here, the neuron receives both excitatory and i nhi bi tory i nputs IPSP Axon Hillock EPSP Excitatory Neurotransmitter Glutamate NO ACTION Release of glutamate IPSPs counteract EPSPs, POTENTIAL creates EP SP s (RED) in and the axon hillock the postsynaptic neuron does not reach threshold In this scenario, the neuron’s threshold of excitation is NOT reached, and the neuron does not fire an action potential The Nervous System  Multiple Nervous Systems! Peripheral Nervous System Central Nervous System T h e N e rv o u s S ys t e m Peripheral C e n t ra l (Everything outside brain (The brain and and spinal cord) spinal cord) A utonom ic S o m at i c (Controls activity of (Relays skin senses and internal organs and controls muscle glands) movements) S y m p at h e t i c Parasympathetic (Arousing) (Calming)  The Cerebral Cortex Parietal Lobe Frontal (Perception) Lobe (Thinking, Occipital Planning & Movement) Lobe (Vision) Temporal Lobe (Memory & Emotion) Sensory & Motor Areas  The Limbic System Hypothalamus Critical for life-sustaining drives (thirst, hunger); plays a role in sexual & aggressive behavior; links the nervous system to the endocrine system Hippocampus Involved in memories of everyday events (e.g., declarative memories) Nucleus Accumbens Amygdala Involved in threat detection, The “reward center” of the fear, and for encoding the brain; critical for the sense of emotional aspects of pleasure memories  The Autonomic Nervous System (ANS) The ANS is made up of 2 major divisions – both project to all major organ systems of the body The sympathetic division is concerned with activities associated with energy expenditure in the body – activated during arousal, fight or flight The parasympathetic division is concerned with vegetative (e.g. non-arousing) states of the body – activated during digestion, waking relaxation, deep sleep, etc – opposes the activity of the sympathetic division  The ANS The Sympathetic N e r vo u s S ys t e m arouses us (It’s the “flight or fight” arm of the ANS) The Parasympathetic N e r vo u s S ys t e m calms us (It’s the “rest and digest” arm of the ANS) The Endocrine System  Hormones & Behavior Hormones are chemical messengers in the body that are released from endocrine gl a n d s – Hormones are typically released and circulate throughout the entire body (via the blood stream) Hormones affect the activity of target tissues by binding to specialized receptors on the cells of those tissues Hormones can also enter the brain, where they bind to receptors on neurons – Hormones can thus influence behavior! The Pituitary (a.k.a. “The Master Gland”) The Hypothalamus The hypothalamus Anterior sends signals to the pituitary Posterior pituitary gland to gland pituitary gland trigger the release of pituitary hormones into the body’s circulation Release of posterior Release of anterior (blood) pituitary hormones pituitary hormones The Endocrine Glands Pituitary hormones trigger the release of other hormones from the endocrine glands!  Some Classic Hormones Hormone Release Site Function Adrenaline Adrenal gland Arousal, flight or flight Cortisol Adrenal gland Stress Metabolism; body Insulin Pancreas weight regulation Male-typical sexual Testosterone Testes behavior; aggressive behavior Female-typical sexual Estrogen Ovaries behavior