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Biological Psychology
Communication in the Nervous System
Distribution of the estimated
100 billion neurons in the adult
central nervous system.
Communication in the Nervous System
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Neurons – electrochemical communication
(1) Soma – cell body
(2) Dendrites – receive transmissions
(3) Axon – transmit away
Myelin sheath – speeds up transmission
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Terminal Button – end of axon;
secretes neurotransmitters
Neurotransmitters – chemical
messengers
Synapse – point at which neurons
interconnect
Transmissions
between
neurons
Figure 2.6 When a section of a neuron is stimulated by other neurons, the cell membrane becomes permeable to
sodium ions so that an action potential of about 40 millivolts is induced. This action potential is transmitted along the
axon. The neuron fires according to the all-or-none principle.
Figure 2.2
FIGURE 2.2 Electrical probes placed inside and outside an axon measure its activity. (The
scale is exaggerated here. Such measurements require ultra-small electrodes, as described
later in this chapter.) The inside of an axon at rest is about -60 to -70 millivolts, compared
with the outside. Electrochemical changes in a neuron generate an action potential. When
positively charged sodium ions (Na+) rush into the cell, its interior briefly becomes positive.
This is the action potential. After the action potential, positive potassium ions (K+) flow out of
the axon and restore its negative charge (see Fig. 2.3 for further explanation).
How many?
How fast?
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Let’s find out ourselves…
Neurotransmitters
Human Nervous System
The primary motor cortex
The Cerebrum:
Two Hemispheres, Four Lobes
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Four Lobes
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Occipital
Temporal
Frontal
Parietal
The Cerebrum:
Two Hemispheres, Four Lobes
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Cerebral Hemispheres
two specialized halves
connected by the
corpus collosum
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Left hemisphere
verbal processing:
language, speech,
reading, writing
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Right hemisphere
nonverbal
processing: spatial,
musical, visual
recognition
In the human visual system
(viewed here from above), light
from either half of the world
crosses through the pupils to
strike the opposite side of each
retina. Axons from the left half
of each retina travel to the left
hemisphere of the brain; axons
from the right half of each retina
travel to the right hemisphere of
the brain.
Experience and the brain
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The two halves of the brain
Work with individuals who have had the “splitbrain” operation (severing the corpus callosum)
to control seizures provides evidence that the
two hemispheres are highly specialized.
 The right hemisphere needs to communicate
with the left in order to name the objects in its
visual field.
 The left hemisphere needs the right in order to
synthesize details into a whole picture (the parts
of a face into a whole recognizable image).
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Brain Plasticity
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http://www.youtube.com/watch?v=TSu9HGnlMV0
Sympathetic and parasympathetic branches of the autonomic nervous system. Both branches
control involuntary actions. The sympathetic system generally activates the body. The
parasympathetic system generally quiets it. The sympathetic branch relays its messages through
clusters of nerve cells outside the spinal cord.
Sympathetic and parasympathetic branches of the autonomic nervous system. The parasympathetic
branch of the ANS generally acts to replenish stores of energy in the body. The sympathetic
branch is the most active during activities that expend energy. The two branches of the ANS
frequently have antagonistic effects on the organs they service.