1.1-1.3 Evolution, Nervous System, Neurons

nature-nurture issue

the longstanding controversy over the relative contributions that genes and experience make to the development of psychological traits and behaviors

natural selection

the principle that the inherited traits enabling an organism to survive and reproduce in a particular environment will most likely be passed on to succeeding generations

evolutionary psychology

the study of the relative power and limits of genetic and environmental influences on behavior

mutation

a random error in gene replication that leads to a change

environment

every nongenetic influence, from prenatal nutrition to our experiences of the people and things around us

heredity

the genetic transfer of characteristics from parents to offspring

identical twins

individuals who developed from a single fertilized egg that split in two, creating two genetically identical organisms (monozygotic)

fraternal twins

individuals who developed from separate fertilized eggs, genetically no closer than ordinary siblings, but shared a prenatal environment

nervous system

the body's speedy, electrochemical communication network, consisting 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 to the rest of the body

sensory neurons

neurons that carry incoming information from the body's tissues and sensory receptors to the brain and spinal cord

motor neurons

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

interneurons

neurons within the brain and spinal cord; they communicate internally and process information between sensory inputs and motor outputs

somatic nervous system

the division of the peripheral nervous system that controls the body's skeletal muscles; also called the skeletal nervous system

autonomic nervous system (ANS)

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs, with its sympathetic division arousing and its parasympathetic division calming

sympathetic nervous system

the division of the autonomic nervous system that arouses the body, mobilizing its energy

parasympathetic nervous system

the division of the autonomic nervous system that calms the body, conserving its energy

reflex

a simple, automatic response to a sensory stimulus, such as the knee-jerk reflex

neuron

a nerve cell; the basic building block of the nervous system

cell body

the part of a neuron that contains the nucleus; the cell's life-support center

dendrites

a neuron's often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body

axon

the segmented neuron extension that passes messages through its branches to other neurons or to muscles or glands

myelin sheath

a fatty tissue layer segmentally encasing the axons of some neurons, enabling vastly greater transmission speed as neural impulses hop from one node to the next

glial cells (glia)

cells in the nervous system that support, nourish, and protect neurons; they may also play a role in learning, thinking, and memory

action potential

a neural impulse; a brief electrical charge that travels down an axon

threshold

the level of stimulation required to trigger a neural impulse

refractory period

in neural processing, a brief resting pause that occurs after a neuron has fired; subsequent action potentials cannot occur until the axon returns to its resting state

all-or-none response

a neuron's reaction of either firing with a full-strength response or not firing

synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

neurotransmitters

chemical messengers that cross the synaptic gap between neurons, influencing whether a neuron will generate a neural impulse

reuptake

a neurotransmitter's reabsorption by the sending neuron

endorphins

natural, opioid-like neurotransmitters linked to pain control and pleasure

agonist

a molecule that increases a neurotransmitter's action

antagonist

a molecule that inhibits or blocks a neurotransmitter's action

endocrine system

the body's slow chemical communication system, consisting of glands and fat tissue that secrete hormones into the bloodstream

hormones

chemical messengers manufactured by the endocrine glands, traveling through the bloodstream to affect other tissues

psychoactive drug

a chemical substance that alters the brain, causing changes in perceptions and moods

depressants

drugs that reduce neural activity and slow body functions

tolerance

the diminishing effect with regular use of a drug, requiring larger doses for the same effect

addiction

compulsive substance use despite harmful consequences

withdrawal

the discomfort and distress following discontinuation of an addictive drug or behavior

opioids

opium and its derivatives that depress neural activity, lessening pain and anxiety

stimulants

drugs that excite neural activity and speed up body functions

hallucinogens

psychedelic drugs that distort perceptions and evoke sensory images without sensory input