KEY CONCEPTS
▪ Overview: information flow through the nervous system
▪ Trace the flow of information through the nervous system and describe the four processes involved in
neural signaling: reception, transmission, integration, and action by effectors.
▪ Neuron - the basic unit of the nervous system
▪ Describe the structure of a typical neuron, give the function of each of its parts.
▪ Neuron communication
▪ Resting membrane potential
▪ Explain how the neuron develops and maintains a resting potential mechanism of nerve action
▪ Compare a graded potential with an action potential, describing the production and transmission of each.
▪ Contrast continuous conduction with saltatory conduction.
▪ Transmission of action potentials between cells (synapse)
▪ Describe the actions of a neurotransmitter
▪ Trace the events that take place in synaptic transmission.
▪ Compare excitatory and inhibitory signals and their effects.
▪ Integration of synaptic potentials
▪ Describe how a postsynaptic neuron integrates incoming stimuli.
▪ Vertebrate nervous system
▪ Describe the two main divisions of the vertebrate nervous system.
▪ Sense organs and sensory reception
▪ Distinguish among five kinds of sensory receptors according to the types of energy they transduce.
Lines of Communications ▪ Neuron structure and Funcrion
→ Communication by neurons largely consists of → Most of a neuron’s organelles, including its
long-distance electrical signals and short-distance nucleus, are located in the cell body.
chemical signals → In a typical neuron, the cell body is studded with
→ Specialized structure of neurons use pulses of numerous highly branched extensions called
electrical current to receive, transmit, and regulate dendrites.
the flow of information over long distances within → Together with the cell body, the dendrites receive
the body. signals from other neurons.
→ In transferring information from one cell to → A neuron also has a single axon ~ an extension
another, neurons often rely on chemical signals that transmits signals to other cells.
that act over very short distances → Axons are often much longer than dendrites
→ The particular connections made by the active → The cone-shaped base of an axon, called the
neuron are what distinguish the type of axon hillock, is typically where signals that travel
information being transmitted. down the axon are generated.
→ In more complex animals, this processing is → Near its other end, an axon usually divides into
carried out largely in groups of neurons many branches.
organized into a brain or into simpler clusters → Each branched end of an axon transmits
called ganglia. information to another cell at a junction~
synapse.
→ The neurons of vertebrates and most → The part of each axon branch that forms this
invertebrates require supporting cells called glial specialized junction is a synaptic terminal.
cells, or glia → At most synapses, chemical messengers called
→ Overall, glia outnumber neurons in the neurotransmitters pass information from the
mammalian brain by 10- to 50-fold. transmitting neuron to the receiving cell.
→ Glia nourish neurons, insulate the axons of → The transmitting neuron as the presynaptic cell
neurons, and regulate the extracellular fluid and the neuron, muscle, or gland cell that
surrounding neurons. TJW NOTES receives the signal as the postsynaptic cell.
,Introduction to Information Processing
→ Information processing by a nervous system occurs
in three stages: sensory input, integration, and
motor output
→ In all but the simplest animals, specialized
populations of neurons handle each stage of
information processing.
• Sensory neurons ~ transmit information about
external stimuli such as light, touch, or smell or
internal conditions such as blood pressure or
muscle tension.
• Interneurons ~ form the local circuits connecting
neurons in the brain or ganglia. Interneurons are
responsible for the integration (analysis and
interpretation) of sensory input.
• Motor neurons ~ transmit signals to muscle cells,
causing them to contract. Additional neurons that
extend out of the processing centers trigger
gland activity.
→ The neurons that carry out integration are
organized in a central nervous system (CNS).
→ The neurons that carry information into and out of
the CNS constitute the peripheral nervous system
(PNS).
→ When bundled together, the axons of neurons form
nerves. TJW NOTES
→ Depending on its role in information processing,
the shape of a neuron can vary from simple to
quite complex
, TJW NOTES
Ion pumps and ion channels establish the resting potential of a neuron
→ In neurons, as in other cells, ions are unequally distributed between the interior of cells and the
surrounding fluid.
→ As a result, the inside of a cell is negatively charged relative to the outside.
→ This charge difference, or voltage, across the plasma membrane is called the membrane potential,
reflecting the fact that the attraction of opposite charges across the plasma membrane is a source of
potential energy.
→ For a resting neuron—one that is not sending a signal— the membrane potential is called the resting
potential and is typically between -60 and -80 millivolts (mV).
→ When a neuron receives a stimulus, the membrane potential changes.
→ These changes, which are known as action potentials
→ An unstimulated cell usually have a resting potential of -70mV.
