ch.3

• Franz Gall - proposed that phrenology, which studies the bumps on the skull, could reveal a person's underlying brain size and associated mental abilities and characteristic traits
• neurons - nerve cells; basic building blocks of the nervous system
• cell body (soma) - part of neuron that contains the nucleus; the cell's life-support center because it assesses messages before passing them along
• dendrites - bushy, branching extensions of a neurons that receives and integrates messages, conducting impulses towards the soma
• axon - the extension of a neuron that send neural impulses to other neurons or to muscles or glands
• dendrites listen, axons speak
• myelin sheath - fatty tissue layer that segmentally protect and insulate the axon and the electrical signal; it speeds neural impulses
• glial cells (glia) - cells in the nervous system that support, nourish, and protect neurons; play a role in learning, thinking, and memory
• nodes of ranvier - gaps between the myelin sheath along the axon that enable ion exchange resulting in the action potential jumping across gaps in what is called salutatory conduction
• multiple sclerosis - deterioration of the myelin sheath that leads to loss of muscle control and numbness
• action potential - a neural impulse; a brief electrical charge that travels down an axon
• ions - electrically charged ions
• in the neuron's chemistry-to-electricity process, ions are exchanged
• the fluid outside an axon's membrane has mostly positively charged sodium ions
• a resting axon's fluid interior has a mostly negative charge
• the axon's surface is selectively permeable
• resting potential - axon gets energy from charged ions
• genotype - an organism's genetic makeup; the blueprint of what an organism is
• phenotype - an organism's physical characteristics
• genes - biochemical units of heredity that make up chromosomes; segments of DNA that are capable of synthesizing proteins
• dominant gene - a gene that actively controls the expression of a trait
• recessive gene - a gene that influences the expression of a trait only when paired with an identical gene
• turner's syndrome - when an individual has a single X chromosome in 23rd pair
• klinefelter's syndrome - an individual has an extra X in their 23rd pair of chromosomes - XXY
• down syndrome - an individual has an extra chromosome on the 21st pair
• nervous system works quickly, endocrine system works slowly
• neurons perform 3 tasks - receives, carries, and passes information
• 3 types of neurons - sensory, inter, motor
• sensory neurons - afferent neurons; carry incoming info from body's tissues and sensory receptors to the brain and spinal cord
• interneurons - neurons within the brain and spinal cord; communicate internally and process info between the sensory inputs and the motor outputs
• motor neurons - efferent neurons; carry outgoing info from the brain and spinal cord to the muscles and glands
• absolute threshold - the minimum amount of stimulus required to produce a response
• if excitatory signals exceed the inhibitory signals by a minimum intensity, or threshold, the combined signals trigger an action potential
• refractory period - neural processing; a brief resting pause that occurs after a neuron has fired; after the refractory period, the neuron is capable of firing another action potential
• absolute refractory period - time right after an action potential when another action potential cannot occur
• relative refractory period - period after the absolute refractory period when a neuron will only respond to a stronger than normal impulse
• all-or-none response - a neuron's reaction of either firing or not
• depolarization - describes an axon firing; causes the next section of axon channels to open
• polarization - describes an axon that is not firing
• excitatory signals are like pushing a neuron's gas pedal, inhibitory signals are like pushing its brake