Introduction to psychology
Chapter 3: Biology and Behavior
3.1 How Does the Nervous System Operate?
LEARNING OBJECTIVES:
Distinguish between the two basic divisions of the nervous system.
Distinguish between the functions of distinct types of neurons.
Describe the structure of the neuron.
Describe the electrical and chemical changes that occur when neurons communicate.
Identify the major neurotransmitters and their primary functions.
The nervous system is responsible for everything we feel, think, and do. The basic units of
this system are the nerve cells called neurons.
Neurons: the basic units of the nervous system; cells that receive, integrate, and
transmit information in the nervous system. They operate through electrical
impulses, communicate with other neurons through chemical signals, and form
neural networks.
The Nervous System Has Two Basic Deviations
The entire nervous system is divided into two basic units:
Central Nervous System (CNS): the brain and the spinal cord.
Peripheral Nervous System (PNS: all nerve cells in the body that are not part of the
central nervous system. The peripheral nervous system includes the somatic and
autonomic nervous systems.
Both nervous systems are anatomically separate but interdependent PNS transmits
information into the CNS CNS organizes and evaluates the information then directs the
PNS to perform specific behaviors or make bodily adjustments.
,Neurons Are Specialized for Communication
Unlike other cells in the body, nerve cells are excitable: they are powered by electrical
impulses and communicate with other nerve cells through chemical signals. Three phases:
RECEPTION: neurons take in the chemical signals from neighboring neurons.
INTEGRATION: incoming signals are assessed.
TRANSMISISON: they pass their own signals to yet other receiving neurons.
Types of Neurons
Sensory neurons: detect information from the physical world and pass that
information to the brain.
Somatosensory nerves: provide the information from the skin and muscles.
Motor neurons: direct muscles to contract or relax, thereby producing movement.
Interneurons: communicate with local or short-distance circuits.
Integrate information in a single area rather than transmitting it to the brain
or organs.
Neuron Structure
A typical neuron has four structural regions that participate in communication functions:
Dendrites: branchlike extensions of the neuron that detect information from other
neurons.
Cell body: the site where information from thousands of other neurons is collected
and integrated (via dendrites).
, Axon: a long narrow outgrowth of a neuron by which information is transmitted to
other neurons.
Terminal buttons: at the ends of axons, small nodules that release chemical signals
from the neuron into the synapse.
Synapse: the gap between the axon of a “sending” neuron and the dendrites of a
“receiving” neuron; the site at which chemical communication occurs between
neurons.
A neuron is covered with a membrane, a fatty barrier that does not dissolve in the watery
environment inside and outside the neuron.
Membrane is semipermeable
On the membrane there are ion channels, specialized pores that allow ions to pass in and
out of the cell when the neuron transmits signals down the axon.
Ions are molecules, some charged positively and some negatively. By controlling
ion movements, the membrane is important for the communication between
neurons.
- Regulates the concentration of charged molecules that are the basis of
the neurons electrical activity.
The Resting Membrane Potential Is Negatively Charged
Resting membrane potential: the electrical charge of a neuron when it is not active.
- A neuron at rest is polarized, greater negative charge inside than outside.
Roles of Sodium and Potassium Ions
Two types of ions that contribute to a neuron’s resting membrane potential: sodium ions and
potassium ions. The passage of ions in and out the membrane is regulated by ion channels
(like those located at the nodes of Ranvier).
Each channel matches a specific type of ion: sodium channels allow sodium ions
but not potassium to pass through the membrane and vice versa.
Flow of ions controlled by a gating mechanism.
Ion flow also affected by the cell membrane’s selective permeability, allows some
ions to pass through more easily than others; as a result, there is more potassium
than sodium inside the neuron.
Chapter 3: Biology and Behavior
3.1 How Does the Nervous System Operate?
LEARNING OBJECTIVES:
Distinguish between the two basic divisions of the nervous system.
Distinguish between the functions of distinct types of neurons.
Describe the structure of the neuron.
Describe the electrical and chemical changes that occur when neurons communicate.
Identify the major neurotransmitters and their primary functions.
The nervous system is responsible for everything we feel, think, and do. The basic units of
this system are the nerve cells called neurons.
Neurons: the basic units of the nervous system; cells that receive, integrate, and
transmit information in the nervous system. They operate through electrical
impulses, communicate with other neurons through chemical signals, and form
neural networks.
The Nervous System Has Two Basic Deviations
The entire nervous system is divided into two basic units:
Central Nervous System (CNS): the brain and the spinal cord.
Peripheral Nervous System (PNS: all nerve cells in the body that are not part of the
central nervous system. The peripheral nervous system includes the somatic and
autonomic nervous systems.
Both nervous systems are anatomically separate but interdependent PNS transmits
information into the CNS CNS organizes and evaluates the information then directs the
PNS to perform specific behaviors or make bodily adjustments.
,Neurons Are Specialized for Communication
Unlike other cells in the body, nerve cells are excitable: they are powered by electrical
impulses and communicate with other nerve cells through chemical signals. Three phases:
RECEPTION: neurons take in the chemical signals from neighboring neurons.
INTEGRATION: incoming signals are assessed.
TRANSMISISON: they pass their own signals to yet other receiving neurons.
Types of Neurons
Sensory neurons: detect information from the physical world and pass that
information to the brain.
Somatosensory nerves: provide the information from the skin and muscles.
Motor neurons: direct muscles to contract or relax, thereby producing movement.
Interneurons: communicate with local or short-distance circuits.
Integrate information in a single area rather than transmitting it to the brain
or organs.
Neuron Structure
A typical neuron has four structural regions that participate in communication functions:
Dendrites: branchlike extensions of the neuron that detect information from other
neurons.
Cell body: the site where information from thousands of other neurons is collected
and integrated (via dendrites).
, Axon: a long narrow outgrowth of a neuron by which information is transmitted to
other neurons.
Terminal buttons: at the ends of axons, small nodules that release chemical signals
from the neuron into the synapse.
Synapse: the gap between the axon of a “sending” neuron and the dendrites of a
“receiving” neuron; the site at which chemical communication occurs between
neurons.
A neuron is covered with a membrane, a fatty barrier that does not dissolve in the watery
environment inside and outside the neuron.
Membrane is semipermeable
On the membrane there are ion channels, specialized pores that allow ions to pass in and
out of the cell when the neuron transmits signals down the axon.
Ions are molecules, some charged positively and some negatively. By controlling
ion movements, the membrane is important for the communication between
neurons.
- Regulates the concentration of charged molecules that are the basis of
the neurons electrical activity.
The Resting Membrane Potential Is Negatively Charged
Resting membrane potential: the electrical charge of a neuron when it is not active.
- A neuron at rest is polarized, greater negative charge inside than outside.
Roles of Sodium and Potassium Ions
Two types of ions that contribute to a neuron’s resting membrane potential: sodium ions and
potassium ions. The passage of ions in and out the membrane is regulated by ion channels
(like those located at the nodes of Ranvier).
Each channel matches a specific type of ion: sodium channels allow sodium ions
but not potassium to pass through the membrane and vice versa.
Flow of ions controlled by a gating mechanism.
Ion flow also affected by the cell membrane’s selective permeability, allows some
ions to pass through more easily than others; as a result, there is more potassium
than sodium inside the neuron.
