Biological Basis of Behaviour (Part I) Ch3 PDF

1 Psychology is actually biology, Biology is actually chemistry, Chemistry is actually physics, Physics is actually math. From: The Lighter Side of Psychology 2 1  PART I Cells of the Nervous System 3 P...

1 Psychology is actually biology, Biology is actually chemistry, Chemistry is actually physics, Physics is actually math. From: The Lighter Side of Psychology 2 1  PART I Cells of the Nervous System 3 PART I Learning Objectives By the end of this section, you will be able to: Identify the basic parts of a neuron Describe how neurons communicate with each other Explain how drugs act as agonists or antagonists for a given neurotransmitter system 4 2  ¡ Glia (green) ¡ Neurons (yellow) 5 1. ‘Glia’- means glue in Greek 2. More numerous than neurons – 90% in the CNS 3. Do not fire action potentials ¡ Provide nutrients to nerve cells (neurons), guide neuron growth during development, remove debris after injury, and remove neuroactive substances from synapses. 6 3  ¡ Fires action potentials! ¡ Major components: 1. Dendrites 2. Soma (cell body) 3. Axon 7 Dendrites act like antennas, receiving messages from other neurons and transmitting to the soma Dendrites have a ‘tree-like’ structure with bumpy protrusions called spines Not myelinated (like axons) 8 4  ¡ Contains the nucleus of the cell (directs the manufacture of proteins) Axon hillock ¡ Contains other structures necessary for survival of the cell ex. mitochondria, ER, ribosomes ¡ ‘Axon hillock’- area in which the action potential initiates 9 ¡ Most neurons have only a single axon ¡ Electrical events generated in axons are called “action potentials” (not all axons are myelinated) ¡ Action potentials are generated at the axon hillock (where axon joins the soma) ¡ Action potentials travel between 1 to 100 m/sec ¡ Larger the diameter of the axon, the faster the transmission of the action Axon hillock potential 10 5  Presynaptic cell ¡ Neurons do no touch each other- they are separated by a small space (synaptic cleft or ‘gap’) Postsynaptic cell ¡ After an action potential is initiated § Neurotransmitter is released (into the synaptic cleft) § This is how communication takes place with the next cell 11 12 6  ¡ Lipid bilayer ¡ Proteins are embedded in the membrane 1. Channel proteins 2. Receptor proteins ¡ Membrane is selectively permeable to ions – Some ions can go through the channels, if they’re open Cytoplasm (inside cell) 13 Neurons can exist in two states Neurons can exist in two states: RESTING ACTIVE BOTH states are equally important! 14 7  Understanding the Neuron at Rest THE RESTING NEURON 15 When the neuron is at rest, the inside of the neuron is electrically negative relative to the outside (-70 mV) cell Due to the distribution of charged particles (ions) across the membrane Typical RMP: –70 mV 16 8  Substance Symbol potassium K+ sodium Na+ chloride Cl– - proteins A- IONS Concentrations at Rest 1. More Na+ and Cl- outside the cell 2. More K+ and A- inside 17 18 9 19 What causes ions to move across the cell membrane? Electrochemical Gradients Diffusion (Concentration Gradient) Electrostatic Gradient THESE ARE PASSIVE PROCESSES (require no energy) 20 10  http://psych.hanover.edu/Krantz/neural/actionpotential.html ¡ Ions will move from an area of high concentration to low concentration 21 Opposites attract: Attract Negatively charged ions are attracted to positively charged ions Repel Like a magnet 22 11  ¡ Active (requires energy) transport of ions across the membrane ¡ Stabilizes ion concentrations for the resting membrane potential 1. K+ back into cell 2. Na+ out Cytoplasm (inside cell) 23 PART II Understanding the ACTIVE NEURON THE ACTIVE NEURON 24 12  Na+ (sodium) K+ -70 mV (potassium) 25 Action Potential Summary 26 13  Na+ (sodium) K+ +30mV -70 mV (potassium) 27 1. If there is a depolarizing event at the axon hillock and the threshold for initiating an action potential is reached (-50 mV) 2. Voltage-sensitive sodium channelsopen Na+ is driven into cell by concentration & electrochemical forces 3. Next: Voltage sensitive potassium channels open ▪ K+ is driven out of cell by concentration (diffusion) & electrochemical forces 28 14  Action Potential Summary 29 ¡ Travels in one direction down the axon ¡ Both active and passive process ¡ All-or-none: - threshold 30 15  ¡ “Saltatory conduction” Jumps from Node of Ranvier to Node of Ranvier (where channel proteins are) 31 Unmyelinated vs Myelinated axons? 32 16  ¡ “Saltatory conduction” Jumps from Node of Ranvier to Node of Ranvier (where channel proteins are) Saltatory conduction is faster! 33 34 17  Action Potential 35 SYNAPSE 36 18  Neurotransmitters are stored in vesicles. Released into the synaptic cleft after action potential arrives at terminal Bind to receptors to initiate events in new neurons 37 38 19  Either excites (excitatory) OR inhibits (inhibitory) the next cell. 39 40 20 41 Examples of NTs 1. Acetylcholine 2. Dopamine 3. Serotonin 4. Adrenaline and noradrenaline Others: Glutamate and GABA endorphins 42 21  Muscle action, Cognitive function, memory, emotion Depletion of the neurotransmitter ACh is most often associated with the cognitive decline in Alzheimer’s Disease 43 Curare poison used in hunting by native South Americans - blocks ACh receptors - paralyzes victim (asphyxia) Botox (botulism) - blocks ACh release 44 22  Nicotiana tabacum 45 Voluntary movement, reward, learning, attention and emotion. Too much dopamine: schizophrenia Too little dopamine: Parkinson’s Disease Michael J Fox 46 23  Mood, hunger, sleep and arousal. Too little serotonin: - Depression - Seasonal Affective Disorder 47 - a.k.a. adrenaline and noradrenaline - epinephrine synthesized from norepinephrine Heart rate, learning and memory, arousal, attention, waking, emotion. Too little norepinephrine: DEPRESSION 48 24  GABA- Major inhibitory neurotransmitter Glutamate- Major excitatory neurotransmitter 49 OPIUM POPPY ¡ Naturally occurring opiate- like substances ¡ Naturally released: fear, pain, exercise (runner’s high), CHOCOLATE ¡ Opiate receptors: Discovered while doing research on morphine (Pert and Snyder, 1973) ¡ Opium, morphine, heroin 50 25