Biological bases of cognition and behavior Part 1 How your “wetware” works... Biological (Physiological) Psychology (Neuroscience) Neuron a nerve cell the basic building block of the nervous system Communication Highway!!! How we work... Neurons Neurons do the “talking” The human brain has about 100 billion neurons, interconnected at 100 trillion synapses. Here’s what a trillion pennies looks like: How it works... Neurons come in 3 basic flavors… Sensory neurons (“afferent” neurons) senses to brain for processing Motor neurons (“efferent” neurons) brain to muscles/glands for reaction Interneurons connectors; only in brain and spinal cord Example: Water temp in shower The Neuron Neural communication down the axon Dendrite the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body Axon the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands Neural communication down the axon Myelin [MY-uh-lin] Sheath a layer of segmented fatty cells encasing the fibers of many neurons greater transmission speed of neutral impulses (Duct Tape) Made from glial cells At rest, the neuron is polarized (at “resting potential”) Sodium (Na+) and chloride (CL-) outside and potassium (K+) inside “Sodium pump” – Ion pump, resets to resting potential When does a Neuron “Talk” Dendrite acts as a NET and grabs the chemical messages, sending info to the cell body/nucleus Nucleus or the “Office Executive” assesses and decides whether to command Neural communication: down the axon Action Potential a neural impulse; a brief electrical charge that travels down an axon positively charged ions in and out of channels in the axon’s semi-permeable membrane Threshold the level of stimulation required to trigger a neural impulse The “All or None” law; coded by firing rate Neural communication: down the axon Cell body end of axon Direction of neural impulse: toward axon terminals Rapid influx of positive charge triggering electrical message: “RELEASE THE MESSAGE!!” Neural communication: down the axon Graded Potentials Small changes that make a neuron more or less likely to fire (i.e., change the threshold) Depolarization = more sensitive Hyperpolarization = less sensitive Nucleus Message comes in as either a excitatory (Fire) or inhibitory (Don’t Fire) neurotransmitters (chemicals) Neural Communication at the synapse Synapse [SIN-aps] Junction/gap between the axon end bulb and the dendrite “net” tiny gap at this junction is called the synaptic gap or cleft Neurotransmitters chemical messengers that traverse the synaptic gaps between neurons (leave the axon) when released, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron (dendrite part) This produces a graded potential in the receiving neuron! Neural Communication: at the synapse Neurotransmitters Excitatory neurotransmitters: FIRE!!!!! Inhibitory neurotransmitters: Don’t FIRE!!! Modulatory neurotransmitters (“neuromodulators”) A shopping list of neurotransmitters... Acetylcholine Learning & memory, but also triggers muscle contraction (botulism = Ach receptor blocker) Dopamine Influences movement, learning, and attention. May be linked to schizophrenia & Parkinson’s disease A shopping list of neurotransmitters... Serotonin Affects mood, hunger, sleep, and arousal. Prozac/Zoloft raises serotonin levels. Norepinephrine and epinephrine Affects alertness and arousal; also anxiety A shopping list of neurotransmitters... Gamma-aminobutyric acid (GABA) Inhibitory neurotransmitter. May be involved in eating and sleep disorders. Note that the effects of neurotransmitters depend on the receptor A given neurotransmitter can trigger different types of receptors with different results! Neural Communication Dopamine pathways Neural Communication Serotonin pathways Fun with neuromodulators... Endorphines “morphine within” natural, opiate-like neurotransmitters linked to pain control and to pleasure Drugs and Neural Communication Neurotransmitter molecule Receptor site on receiving neuron Receiving cell membrane Just write down what agonist and antagonists do Agonist mimics neurotransmitter Antagonist blocks neurotransmitter The Nervous System configured Nervous system Central (brain and spinal cord) Peripheral Autonomic (controls self-regulated action of internal organs and glands) Skeletal (controls voluntary movements of skeletal muscles) Sympathetic (arousing) Parasympathetic (calming) The Nervous System The body’s speedy, electrochemical communication system consists of all the nerve cells of the peripheral and central nervous systems Central Nervous System (CNS) the brain and spinal cord Peripheral Nervous System (PNS) the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body The Peripheral Nervous System – part A Autonomic Nervous System controls the glands and the muscles of the internal organs (such as the heart) Sympathetic Nervous System arouses the body, mobilizing it in stressful situations Parasympathetic Nervous System calms the body, conserving its energy The Peripheral Nervous System – part B The skeletal nervous system Lots of efferent neurons (Motor) But also afferent (sensory) for the kinesthetic sense http://findarticles.com/p/articles/mi_g2699/is_0001/ai_2699000193/ The peripheral nervous system The peripheral nervous system An example of neural communication: Reflex: a simple, automatic, inborn response to a sensory stimulus Brain Sensory neuron (incoming information) Muscle Skin receptors Motor neuron (outgoing information) Interneuron Spinal cord How your brain is “wired” Neurons in the brain connect with one another to form networks Inputs The brain learns by modifying certain connections in response to feedback Neural Networks interconnected neural cells with experience, networks can learn, as feedback strengthens Outputs or inhibits connections that produce certain results computer simulations of neural networks show analogous learning