Chapter 2 The Biology of Mind Biological psychologists study links between our biology and our behavior Biological psychology is the study of the links between biological genetics neural hormonal and psychological processes Neural Communication Neurons Neurons a nerve cell basic building block of the nervous system DENDRITES receive information and conduct them toward the cell body The neurons bushy branching extensions that receive messages and conduct impulses toward the cell body short Cell body houses the nucleus AXON passes the message along to other neurons or to muscles or glands The neurons extension that passes messages through its branching terminal fibers that form junctions with other neurons muscles or glands Sometimes covered with the myelin sheath that helps speed neural impulses Long projecting several feet through the body Neurons transmit messages when stimulated by signals from our senses or by chemical signals from neighboring neurons fires an impulse called the ACTION POTENTIAL A neural impulse a brief electrical charge down an axon 2 types of signals 1 Excitatory accelerator ES Inhibitory brakes IS 2 ES IS THRESHOLD trigger an action potential The minimum level of stimulation required to trigger a neural impulse Increase in stimulation DOES NOT INCREASE the strength or intensity of the impulse A strong stimulus can trigger more neurons to fire and to fire more often but does not affect the action potential s strength or speed Squeezing the trigger of a gun harder won t make the bullet go faster How Neurons Communicate Neural impulses took a long time to travel a neural pathway brief interruption in the transmission Sir Charles Sherrington called the meeting point between 2 neurons a SYNAPSE The junction between an axon tip of the sending neuron and the dendrite or cell body of the receiving neuron The tiny gap at this junction is called the synaptic gap or synaptic cleft When an action potential reaches the knoblike terminals at an axon s end it triggers the release of chemical messengers called NEUROTRANSMITTERS Chemical messengers that cross the synaptic gaps between the neurons When released by the sending neuron they across the synapse and bind to the receptor sites on the receiving neuron thereby influencing whether that neuron will generate a neural impulse Lock and key model The NT unlocks the tiny channels at the receiving site and electrically charged atoms flow in exciting or inhibiting the receiving neurons readiness to fire Then in a process called reuptake the sending neuron absorbs the excess NTs How do Transmitters Influence Us Dozens of different NTS ACETYLCHOLINE ACH role in learning and memory messenger at every junction between a motor neuron brain and spinal cord body tissues and skeletal muscles release of Ach to our muscle cell receptors muscle contracts blockage of Ach transmission muscles cannot contract and we are paralyzed some kinds of anesthesia Malfunctions Alzheimer s Ach producing neurons deteriorate Morphine Opiate dug elevates mood and eases pain Brain produces its own naturally occurring opiates ENDORPHINS ENDOgenous moRPHINS Natural opiate like NTs linked to pain control and to pleasure Runner s high Painkilling effects of acupuncture Indifference to pain in some severely injured people Malfunctions flooding by artificial opiates results in the brain s inability to produce endorphins causing intense discomfort DOPAMINE Influences movement learning attention an emotion Malfunctions Excess schizophrenia Starved of dope brain produces tremors and decreased mobility of Parkinsons s disease SEROTONIN Affects mood hunger Sleep and arousal Malfunctions levels NOREPINEPHRINE Noradrenalin Controls alertness and arousal Malfunctions Undersupply depression Undersupply depression Prozac and antidepressant drugs raise serotonin Agonist molecules similar to NT and binds to its receptor and mimic its effects Antagonists molecules bind to receptors but their effect is to block a NT s effects Some drugs are agonists and produce a temp high by amplifying normal sensations of arousal or pleasure Curare a poison blocks Ach receptor sites on muscles producing paralysis in animals struck by a poisoned dart The Nervous System The body s speedy electrochemical communication network consisting or nerve cells of the peripheral and central nervous systems The Nervous System CNS PNS CNS brain and spinal cord BSc the body s decision maker PNS sensory and motor neurons connect the CNS with the rest of the body responsible for gathering information and for transmitting CNS decisions to other body parts Nerves are bundled axons that form cables connecting the CNS with the muscles glands and sense organs 3 types of Neurons 1 Sensory carry incoming information from the sensory receptors to the BSc 2 Motor carry outgoing information from the BSc to the muscles and glands 3 Interneurons neurons within the BSc that communicate internally and intervene between the sensory and motor outputs The Peripheral Nervous System PNS 2 components 1 Somatic SNS Enables voluntary control of our skeletal muscles also known as skeletal nervous system Example As u reach the end of a page the SNS will report to your brain the current state of your skeletal muscles and carry instructions back triggering your hand to turn the page 2 Autonomic ANS Controls our glands and the muscles of internal organs influencing functions such as glandular activity heartbeat and digestion Operates on its on autonomously 2 important basic functions 1 Sympathetic Nervous System Arouses the body mobilizing its energy in stressful situations Accelerates your heartbeat raises BP slows digestion raises your blood sugar cools you with perspiration making you alert and ready for action Example when u see a mad dog loose on the street 2 Parasympathetic Nervous System Calms the body conserving its energy Decreasing your heartbeat lowering your blood sugar Example sitting in class Both work together to keep you in a steady internal state The Central Nervous System CNS Brain spinal cord Brain enables our humanity our thinking feeling and acting Brains neurons cluster into work groups called neural networks The spinal cord is an information highway connecting the PNS to the brain
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