In this chapter we will examine: What are the components of the nervous system? How does the Brain create mental processes and behavior?
“What we understand least is why brain activity produces experience at all.” Kalat
Explanations for behavior
The best theories in psychology explain behavior in terms of evolution, development or psychology.
Evolutionary explanations relate behavior to the history of the species.
Developmental explanations describe changes during the life of an organism.
Explanations for behavior
Physiological explanations describe mechanisms that produce behaviors.
We try to explain behavior in terms of the activity of the cells of the nervous system.
We will start by with how scientists measure brain activity.
You experience yourself as a single entity.
Neuroscientists have demonstrated that experience is the product of a nervous system made up of an enormous number of discrete cells.
The cells that make up your nervous system are called neurons.
Neurons and communication
Neurons are cells that receive and transmit information electrochemically.
Sensory neurons carry information from sense organs to the central nervous system.
Neurons in the CNS process information interpret it and send commands to muscles, glands, and organs.
Nervous system cells
The best estimate is that the human nervous system has nearly 100 billion neurons.
They aren’t the only type of cell in the system.
Glia supports the neurons in many ways.
They provide insulation, and remove waste products and foreign bodies.
They are 1/10th the size of the neurons but about 10 times as numerous.
Anatomy of a neuron
Neurons have a variety of shapes, but they all have 3 basic parts
A cell body that contains the nucleus and most of the organelles.
The dendrites- branching structures that receive transmissions from other neurons.
The axon- a single, long, thin fiber with branching tips.
The axon sends electrochemical messages to neighboring cells.
Most axons transmit information to the dendrites or cell bodies of neighboring neurons.
Many axons have a coating of myelin sheath, which speeds up transmission.
Nerve cell growth
Neurons do not have a fixed anatomy.
Researchers have found that neurons constantly grow and lose branches to dendrites and axons.
This growth is related to new experiences and learning.
Axons convey information by a combination of electrical and chemical processes.
This combination is called an action potential.
An action potential is a signal that travels along the axon at a constant strength no matter how far it travels.
The all-or-none law
An action potential is al all or nothing process-its either happening or not; there’s no “sort of” action potential.
This message reaches the brain at full strength, but more slowly than regular electrical conduction.
How an action potential works:
An un-stimulated axon has resting potential.
Resting potential is an electrical polarization across the membrane covering the axon.
A polarized axon is charged negatively (-70 millivolts) relative to the outside.
Resting potential is maintained by the sodium-potassium pump.
Sodium is mostly concentrated outside the neuron and potassium mostly inside, and they are held in place by the…