2 The Biology Of Mind Flashcards
(28 cards)
although long ago dismissed, what did phrenology succeed in doing?
focusing our attention on the localization of function - the idea that various brain regions have particular functions.
why do scientists study animal brains if they’re interested in human brains?
the information systems of human and other animals operate similarly. this similarity allows researchers to study relatively simple animals to discover how our neural systems operate. animals differ, yet their nervous systems operate similarly.
what is a neuron?
a nerve cell; the basic building block of the nervous system
what are dendrites?
a neuron’s bushy, branching extensions that receive messages and conduct impulses toward the cell body.
what are axons?
the neuron extension that passes messages through its branches to other neurons or to muscles or glands.
dendrites___, axons ___
dendrites listen, axons speak.
what is a main difference between axons and dendrites?
dendrites are short while axons have the potential to be very long
what is a myelin sheath?
a fatty tissue layer segmentally encasing (insulates) the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node tot he next.
what happens as myelin is laid down and up to about what age does this happen?
- neural efficiency, judgment, and self-control grows.
what happens if the myelin sheath degenerates?
multiple sclerosis results: communication to muscles slows, with eventual loss of muscle control.
when do neuron transmit messages?
when stimulated by signals from our senses or when triggered by chemical signals from neighboring neurons.
what is an action potential?
a neural impulse; a brief electrical charge that travels down an axon.
describe how neurons generate electricity from chemical events
in the neurons chemistry-to-electricity process, ions (electrically charged atoms) are exchanged. the fluid outside an axon’s membrane has mostly positively charged ions; a resting axon’s fluid interior has mostly negatively charged ions. this positive outside/negative inside state is called he resting potential. the axon’s surface is very selective about what it allows through its gates. we say the axon’s surface is selectively permeable.
what happens when a neuron fires?
the first section of the axon opens its gates and positively charged sodium ions flood through the cell membrane. this depolarizes that axon section, causing another axon channel to open up, and then another like a line of falling dominos, each tripping the next.
what happens during a resting pause between neuron firing?
the neuron pumps the positively charged sodium ions back outside. then it can fire again.
what happens to the action potential in myelinated neurons?
it speed up by hoping from the end of one myelin “sausage” to the next.
how is each neuron a miniature decision-making device?
by performing complex calculations as it receives signals from hundreds, even thousands, of other neurons.
what are most neural signals?
most signals are excitatory; somewhat like pushing a neuron’s accelerator.
what are the other neural signals?
the other signals are inhibitory; more like pushing its brakes.
when speaking of neurons, what is a threshold?
the level of stimulation required to trigger a neural impulse.
how do signals and threshold combine to create action potentials?
if excitatory signals minus inhibitory signals exceed a minimum intensity, or threshold, he combined signals trigger an action potential.
what do we mean when we say a neuron’s reaction is an all-or-none response?
increasing the level of stimulation above the threshold will not increase the neural impulse’s intensity. like a gun, neurons either fire or they don’t.
if neurons exhibit all-or-none responses, how can we detect the intensity of a stimulus?
a strong stimulus ca trigger more neurons to fire, and to fire more often. but ti does not affect the action potential’s strength or speed.
what is a synapse?
the junction between the 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.
