Unit 3 Flashcards
Describe the structure and functions of the glia cells and neurons.
They are the basic links that permit communication within the nervous system. The vast majority of them communicate only with other neurons. However, a small minority receive signals from outside the nervous system (from sensory organs) or carry messages from the nervous system to the muscles that move the body
What is a neuron?
Neurons are individual cells in the nervous system that receive, integrate, and transmit information.
What is a soma?
The soma, or cell body, contains the cell nucleus and much of the chemical machinery common to most cells (soma is Greek for body).
What is a dendrite?
Dendrites are the parts of a neuron that are specialized to receive information.
What is a axon?
The axon is a long, thin fibre that transmits signals away from the soma to other neurons or to muscles or glands.
What is the myelin sheath?
The myelin sheath is insu- lating material, derived from glial cells, that encases some axons.
What is a terminal button?
terminal buttons, which are small knobs that secrete chemicals called neurotransmitters
What is a synapse?
A synapse is a junction where information is transmitted from one neuron to another (synapse is from the Greek for junction). To summarize, infor- mation is received at the dendrites, is passed through the soma and along the axon, and is transmitted to the dendrites of other cells at meeting points called synapses.
What is a glia?
Glia are cells found throughout the nervous system that provide various types of support for neurons.
What is a neural impulse?
Hodgkin and Huxley (1952) learned that the neural impulse is a complex electrochemical reaction. Both inside and outside the neuron are fluids containing electrically charged atoms and molecules called ions. The cell membrane is semipermeable, permit- ting movement of some ions. Positively charged sodium and potassium ions and negatively charged chloride ions flow back and forth across the cell membrane, but they do not cross at the same rate. The difference in flow rates leads to a slightly higher concentration of negatively charged ions inside the cell.
Describe the “battery-like” features of a neuron at rest. Define the resting potential of a neuron. How many millivolts is the resting potential in most neurons?
The resulting voltage means that the neuron at rest is a tiny battery, a store of potential energy. The resting potential of a neuron is its stable, nega- tive charge when the cell is inactive. As shown in Figure 3.2(a), this charge is about 270 millivolts, roughly one-twentieth of the voltage of a flashlight battery
Define the action potential of a neuron.
An action potential is a very brief shift in a neuron’s electrical charge that travels along an axon.
What is the absolute refractory period?
The absolute refractory period is the minimum length of time after an action poten- tial during which another action potential cannot begin
Describe the all-or-none law of the neural impulse. Explain how neurons convey information about the strength or intensity of a stimulus.
The neural impulse is an all-or-none proposition, like firing a gun. You can’t half-fire a gun. The same is true of the neuron’s firing of action potentials. Either the neuron fires or it doesn’t, and its action potentials are all the same size (Kandel, 2000). That is, weaker stimuli do not produce smaller action potentials.
Describe a synaptic cleft. Define presynaptic neuron and postsynaptic neuron.
syn- aptic cleft, a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron.
