Brain Function for Law-Neuro “Your brain is a network of neurons, bursting with electrical activity flowing through your synapses. Makes you think, doesn’t it? ” “The brain like other parts of the body is made up of molecules. And the function of any part of the body involves molecular changes, so that when any part of the body is dysfunctional there would be some type of molecular change that would be occurring.” Personality disorders would have disordered molecular processes going on. As Ralph Gerard has said: ‘Behind every crooked thought, there lies a crooked molecule.’ ”

Goals Introduces the types of cells in the nervous system, and summarizes how neurons signal to each other. Situates the brain within its evolutionary history and explains how brain systems produce human behavior. Discusses how drugs can affect brain function.

Review neuroanatomical terms of orientation & location And basic structures

A few facts about neurons Neurons comprised of Soma or cell body Nucleus is where constituents like neurotransmitters are produced Dendrite – input end Axons – output end Some axons covered with myelin sheath produced by glia known as oligodendrocytes Neurons are excitable. They generate and propagate nerve impulses also known as action potentials Nerve impulses are brief (1 ms) electrical event that propagates from soma to axon terminals Conduction speed of 20-50 m/s Speed improved by myelin sheath

A few facts about neurons ~85 billion in human brain Typical neuron connects with 1,000-10,000 other neurons Connections occur at synapse Neurons respond selectively to the inputs they receive. They “interpret” the pattern of inputs Neuroscientists know a great deal about the biophysical process but the general rules of “interpretation”, i.e., neural codes, remain uncertain The brain develops intricate and precise connections during development and education No neurons added after brain matures Synaptic pruning shapes precise connections according to “use it or lose it” principle also known as “neurons that fire together wire together”

Synaptic transmission: Introduction Axon separated from dendrite by synaptic cleft Arrival of nerve impulse at axon terminal causes release of neurotransmitter into cleft Neurotransmitter diffuses in synaptic cleft Some neurotransmitter molecules bind to receptors in the axon membrane This binding causes other processes that change the state of the neuron Membrane can be depolarized (increasing chance of nerve impulse) or hyperpolarized (decreasing chance of nerve impulse) Several processes remove neurotransmitter from the cleft Reuptake Breakdown by other chemical processes Uptake into glia

A few facts about glia Support and enhance neuron function Different kinds of glia One produces myelin sheath Another facilitate synaptic transmission Absorbing neurotransmitters Connecting neurons to blood vessels Glioma is a common and generally lethal form of tumor

Where brains come from Brains enable behavior Nervous systems enable sensitivity to and mobility in the environment to find food and mates and avoid predators Why vs How questions Why – ultimate cause How – proximate cause

Synaptic transmission: More details Three categories of neurons Excitatory Inhibitory Modulatory Each neuron receives connections from each other type of neuron Excitatory neurons Increase probability that post-synaptic neuron produces nerve impulse Glutamate neurotransmitter Depolarize post-synaptic membrane Connect with neurons nearby and in distant brain structures Inhibitory neurons Decrease probability that post-synaptic neuron produces nerve impulse GABA neurotransmitter Hyperpolarize post-synaptic membrane Usually connect only with neurons nearby Modulatory neurons Longer and more subtle influences Tune the balance of excitation and inhibition Variety of neurotransmitters Dopamine Norepinephrine Serotonin Second-messenger mechanisms Cell bodies concentrated in brainstem with axons branching throughout subcortical and cortical structures.

Synaptic transmission: More details Psychoactive drug actions Agonist Presynaptic Postsynaptic Antagonist Example of dopamine function in Parkinson’s disease and schizophrenia L-DOPA Blood-brain barrier Example of Prozac Selective serotonin reuptake inhibitory