5 Steps to a 5 AP Psychology, 2010-2011 Edition - Laura Lincoln Maitland [41]
The wave of depolarization and repolarization is passed along the axon to the terminal buttons, which release neurotransmitters. Spaces between segments of myelin are called nodes of Ranvier. When the axon is myelinated, conduction speed is increased since depolarizations jump from node to node. This is called saltatory conduction. Chemical neurotransmitters are released into the synapse where they attach to specific receptor sites on membranes of dendrites of your postsynaptic neurons, like a key fitting into the tumbler of a lock (the lock and key concept). Some of your synapses are excitatory, the neurotransmitters cause the neuron on the other side of the synapse to generate an action potential (to fire); other synapses are inhibitory, reducing or preventing neural impulses. The sum of all excitatory and inhibitory inputs determines whether your next neuron will fire and at what rate. The constant flow of these neurochemical impulses gives your behavior its amazing complexity. It regulates your metabolism, temperature, and respiration. It also enables you to learn, remember, and decide.
Reflex Action
The simplest form of your behavior, called a reflex, involves impulse conduction over a few (perhaps three) neurons. The path is called a reflex arc. Sensory or afferent neurons transmit impulses from your sensory receptors to the spinal cord or brain. Interneurons, located entirely within your brain and spinal cord, intervene between sensory and motor neurons. Motor or efferent neurons transmit impulses from your sensory or interneurons to muscle cells that contract or gland cells that secrete. Muscle and gland cells are called effectors. Examples of your reflexes include your pupillary reflex, knee jerk, sneezing, and blinking. Neural impulses travel one way along the neuron from dendrites to axons to terminal buttons, and among neurons from the receptor to the effector.
The Endocrine System
Your endocrine system interacts with your nervous system to regulate your behavior and body functions. Your endocrine system consists of glands that secrete chemical messengers called hormones into your blood. The hormones travel to target organs where they bind to specific receptors. Endocrine glands include the pineal gland, hypothalamus, and pituitary gland in your brain; the thyroid and parathyroids in your neck; the adrenal glands atop your kidneys; pancreas near your stomach; and either testes or ovaries.
Genetics and Evolutionary Psychology
Why do you behave the way you do? To what extent is your behavior determined by your heredity? To what extent is it determined by your life history or environment? The nature-nurture controversy deals with the extent to which heredity and the environment each influence behavior. Evolutionary psychologists study how natural selection favored behaviors that contributed to survival and spread of our ancestors’ genes, and may currently contribute to our survival into the next generations. Evolutionary psychologists look at universal behaviors shared by all people. They look at behaviors conserved across related species to understand how we are adapted to maximize our success in our environments. Charles Darwin pointed out the similarities of the expressions of emotions in people and other animals, suggesting that expressions shared across cultures and species are biologically determined.
Genetics and Behavior
Behavioral geneticists study the role played by our genes and our environment in mental ability, emotional stability, temperament, personality, interests, etc.; they look at the causes of our individual differences. Your genes predispose your behavior. Studies of twins have been helping to separate the contributions of heredity and environment. Identical twins