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Biological Psychology Key Point for this Unit: Everything psychological is simultaneously biological!! NEURON Dendrites Dendrites – receive messages from other cells and conduct impulses toward the cell body NEURON Dendrites Cell Body Cell Body – the cell’s life-support center NEURON Dendrites Cell Body Axon Axon – the extension of a neuron through which messages are sent to other neurons or to muscles or glands NEURON Dendrites Cell Body Axon Myelin Sheath Myelin Sheath – a layer of fatty cells covering the axon, helps speed neural impulses NEURON Dendrites Terminal branches of axon Cell Body Axon Myelin Sheath Terminal branches of axon – form junctions with other cells Biological Psychology It is all about the body!!!! Concerned with the links between biology and behavior (also called Neuroscience) The Nervous System It starts with a NEURON: an individual nerve cell; the basic building block of the nervous system How does a Neuron fire? • Resting Potential: slightly negative charge. • Reach the threshold when enough neurotransmitters reach dendrites. • Threshold: level of stimulation required to trigger a neural impulse; excitatory signals minus inhibitory signals must equal a minimum intensity • Go into Action Potential; a neural impulse (brief electrical charge) that travels down an axon. • All-or-none response. Neurons – How do they work? • Neurons send messages to other neurons – this is what keeps every part of our body in communication with every other part. • Neurons “fire” – send an impulse (message) down their length – or they don’t “fire” Action Potentials Watch “The Action Potential” movie at home: http://brainu.org/files/movies /action_potential_cartoon.swf • This “firing” of impulse messages is called the action potential. • An action potential is a brief electrical charge that travels down the axon of the neuron. Play Animation What causes an impulse to fire or not fire? • When a neuron is at rest and capable of generating an action potential, it is called the resting potential • There are fluids inside and outside of the neuron, filled with electrically charged particles (ions) • When the neuron is at rest, there is a negative charge on the inside of the neuron compared to the outside. • At rest, the inside of the cell is at -70 millivolts Neuron Communication Resting Potential Action Potentials, cont. • Stimulation from inputs to dendrites causes the cell membrane to open briefly • Positively charged sodium ions flow in through the cell membrane • If resting potential rises above threshold, an action potential starts to travel from the cell body down the axon – Threshold - Each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity (threshold) the neuron fires an action potential. Figure 2.3 Action potential Myers: Psychology, Ninth Edition Copyright © 2010 by Worth Publishers Action Potential, cont. • The shift in electrical charge travels along the neuron • The intensity of an action potential remains the same throughout the length of the axon • Refractory period - The “recharging phase” when a neuron, after firing, cannot generate another action potential To help a mad scientist make a “mad, mad, mad neuron” in a cartoon game, see http://learn.genetics. utah.edu/content/add iction/reward/madneu ron.html For more information on action potentials, see http://faculty.washington.edu/chudl er/ap.html For an interactive game/demo to help you learn about action potentials, see http://outreach.mcb.harvard.edu/a nimations/actionpotential_short.swf Neuron Communication All-or-None Principle • The principle that if a neuron fires it will always fire at the same intensity • A strong stimulus can trigger more neurons to fire, and to fire more often, but all action potentials are of the same strength and speed. • A neuron does NOT fire at 30%, 45% or 90% but at 100% each time it fires. Just like a gun, there is no “part-way” firing How is a neuron firing similar to a toilet flushing? • Consider the following concepts: – Depolarization – All-or-none principle – Direction of impulse – Refractory period – Threshold – Resting potential – Action potential How about a school bus? See “The School Bus Story” ppt. here: http://ap-psychology1st.grandblanc.high.schoolf usion.us/modules/locker/fil es/group_files.phtml?gid= 1316804&parent=4425886 &sessionid=8b85e917de89 43dc49c835c286f82aff The School Bus Story A tale of ionic influence on action potentials Setting the stage • Imagine a school bus, filled with unhappy kids on their way to school… Meanwhile… • Outiside, it’s a BEAUTIFUL day! – Sun is shining – Birds are chirping – Everything is happy The point is… • The unhappy (negative) kids, sealed inside their impermeable school bus, cannot get to the happiness (positivity) outside! All of a sudden… • The bus driver opens the door! Yay! The bus is now permeable… but only in a selected place. Area of selective permeability And then? • Sunlight, happiness, butterflies, and positivity fill the negative kids on the bus with deep inner joy. Yay, happy kids! • If enough kids go from sad to happy when the beautiful air whooshes in, they have reached the “threshold.” If/when this threshold is reached, they start getting rambunctious ("action potential"). • After having wasted their energy being rambunctious, there's a short time ("refractory period") before they can start it up again. How does this relate? • • • • The kids = negative ions. The bus = an axon. The sunlight = positive sodium ions. The bus pre-open door = a polarized neuron in its resting potential. • The driver = cell nucleus. • The opened door = selectively permeable gates. • The happy kids = an action potential… but only if enough of them become happy! What happens when an action potential reaches the end of the axon and enters the terminal buttons? TYPES OF NEUROTRANSMITTERS Chemical messengers that that traverse the synaptic gap between neurons REVIEW… remember agonists and antagonists??? Agonist – mimic neurotransmitters **Example: Morphine mimics endorphins Antagonist – block neurotransmitters **Example: Poison blocks muscle movement Did you know? Botox is an antagonist that paralyzes facial muscles! Acetylcholine (ACH) • Involved with voluntary muscle movement, learning and memory • Lack of ACH has been linked to Alzheimer’s disease. Dopamine • Deals with motor movement and alertness. • Lack of dopamine has been linked to Parkinson’s disease. • Too much has been linked to schizophrenia. Serotonin • Involved in mood control. • Lack of serotonin has been linked to clinical depression. Endorphins Did you know? The word “endorphin” literally means “morphine within”! • Involved in pain control. • Many of our most addictive drugs deal with endorphins. “Runner’s High” occurs when your brain signals the release of endorphins to reduce pain! The Nervous System The Nervous System - body’s speedy, electrochemical communication network consisting of nerve cells Central Nervous System (CNS) • The Brain and spinal cord • Neural networks – interconnected neural cells; more connections made as experience gained Peripheral Nervous System (PNS) • All nerves that are not encased in bone. • Sensory and motor neurons that connect the CNS to the rest of the body • Is divided into two categories….somatic and autonomic. Somatic Nervous System • Controls voluntary muscle movement. • Uses motor neurons. Autonomic Nervous System • Controls the automatic functions of the body. • Divided into two categories…the sympathetic and the parasympathetic Sympathetic Nervous System • Arouses the body • Fight or Flight Response. • Automatically accelerates heart rate and breathing, dilates pupils Parasympathetic Nervous System • Calms the body • Automatically slows the body down after a stressful event. • Heart rate and breathing slow down, pupils constrict Sympathetic and Parasympathetic Types of Neurons • Sensory Neurons – sends receptors to CNS • Interneurons – internal communication neurons • Motor Neurons – CNS to muscle and glands • Normally, sensory neurons take info up through spine to the brain. • With reflexes though, some reactions occur when sensory neurons reach just the spinal cord. • Automatic response to sensory stimulus; interneurons react to sensory neurons w/o going to brain Reflexes