Lecture Chapter 3 Biology of Behavior Neuron Structure Dendrites receive messages from other cells Soma cell body the cells life support center Terminal buttons form junctions with other cells Myelin sheath covers axon of some neurons and helps speed neural impulses o Neural impulses electrical signal traveling down axon Axon inside myelin sheath passes messages away from cell body to other neurons muscles glands 85 billion neurons in adult brain Neuron Classification Schemes Number of axon processes o Unipolar o Bipolar o Multipolar most common Function o Sensory neurons carry messages toward brain o Motor neuron carry messages to muscles o Interneurons connect cells Neurotransmitter NT used by neuron Effects of NT excititatory vs inhibitory CNS PNS Support Cells o Astrocytes most common o Oligodendroglia CNS o Schwann cells PNS Electrochemical Conduction Neuroglia glue provide physical support control nutrient flow and are involved in phagocytosis Nerve cells are specialized for communication neurons conduct ELECTROCHEMICAL signals o Dendrites receive chemical message from adjoining cells o Chemical messengers activate receptors on dendritic membrane o Receptor activates open ion channels which can alter membrane potential o Action potential can result and is propagated down the membrane o Action potential causes release of transmitter from axon terminals Ion Channels Channels allow for entry efflux of ions o Ligand gated o Voltage gated o Stretch gated mechanically gated Impact of ion channel will depend on charge direction of flow Lecture Chapter 3 Biology of Behavior Measuring Resting Membrane potential of a Neuron Giant axon from squid is placed in seawater in a recording chamber Glass microelectrode is inserted into axon o Voltage measures 70mV inside with respect to outside Action potential are generated in the initial segment axon hillock when the RMP rises above the threshold The Action Potential AP o Initial segment has high density of voltage gated sodium channels AP is stereotyped charge in membrane potential o If RMP moves past threshold membrane potential quickly moves to 40mV and then returns to resting Ionic basis of the AP o Na in upswing of spike Diffusion electrostatic pressure K out downswing of spike Synapses Synapse is the physical gap between pre post synaptic membranes 20 30nM o Presynaptic membrane is typically an axon Axon terminal contains Mitochondria Synaptic vesicles Postsynaptic membrane can be A dendrite axondendritic synapse A cell body axonsomatic synapse Another axon axonaxonic synapse Postsynaptic thickening ICS under the axon terminal and contains receptors for transmitters Termination of Postsynaptic Potentials The binding of NT to a postsynaptic receptor results in PSP Termination accomplished by o Reuptake NT molecule is transported back into the cytoplasm of presynaptic membrane NT molecule can be reused Vesicular transporters can move NT into vesicles o Enzymatic deactivation an enzyme destroys the NT molecule o Diffusion away from receptor sites Synaptic Transmission Transmitter substances are o Synthesized stored released terminated o Susceptible to drug manipulation Lecture Chapter 3 Biology of Behavior Definitions o Agonist will activate receptors o Antagonist will bind but prevent activation Acetylcholine arousal selective attention sleep memory Acetycholinergic neurons distributed across the brain Acetylcholine release is generally facilitatory Drugs act at multiple levels to facilitate or inhibit acetylcholine activity o Botulinum toxin Botox ITSP can kill entire campus o Black widow spider venom prevents NT being stored agonist o Atropine prevent respirator inflammation o Curare blocks acetycholoine from affecting Monoamines Dopamine plays critical role in reward sex food gambling o Cocaine o Amphetamine o Methylphenidate o MAO inhibitors prolong DA activity Norepinephrine adrenaline arousal and stimulus response Found in neurons in the autonomic nervous system Cells project through brain Serotonin 5 HT mood sleep wake temperature control aggression o cell bodies located in brain stem and project to cortex LSD MDMA o Amino acids Glutamate Enhanced learning and memory Principal excitatory NT in CNS Excitotoxicity GABA Suppresses overactive brain areas o Primary inhibitory NT in CNS o Distributed throughout brain o Alcohol Anandamide Eating memory motivation sleep o Marijuana THC Endorphins Reduce pain Endogenous opioids Lecture Chapter 3 Biology of Behavior Glycine Neural Plasticity Growth Synaptogenesis Pruning Myelination The Two Nervous Systems Central Nervous System brain spinal cord Perphiral Nervous System cranial spinal nerves and peripheral ganglia o PNS nerves project to target organs and to muscles efferent exit o These nerves also carry sensory information to brain afferent add Cerebrospinal Fluid Brain floats in pool of cerebrospinal fluid CSF 4 brain ventricles CSF is produced by choroid plexus of each ventricle Brain ventricles can expand when the brain cells are lost Cerebral Cortex sulci small grooves fissures large grooves Cerebral cortex forms outer surface of cerebral hemispheres gray appearance 4 lobes o Frontal controlling planning Broca s Area speech production o Parietal touch pain temperature how to locate object o Occipital vision o Temporal hearing Wernicki s Area speech comprehension