Notes From Reading
C HAPTER 3: THE BIOLOGICAL B ASIS OF BEHAVIOR
I. Communication in the Nervous System
A. Nervous Tissue: The Basic Hardware
1. 2 Major Categories for Cells in Nervous System
a. Glia – cells found throughout the nervous system that provide structural
support and insulations for neurons. Help maintain the chemical
environment of the neurons
b. Nuerons- the individual cells in the nervous sytem that receive,
integrate, and transmit info. Permit communication (mostly within other
neurons) – only sensory organs revieve signals from outside the nervous
2. Parts of a Neuron:
a. Soma (cell body) – contains the nucleus and muc of the chemical
machinery common to most cells.
b. Rest of neuron dedicated to handling info.
c. Dendrites – parts of the neuron that are speacialized to receive info.
d. Axon – info travels from dendrites to axon, which are the long thin fiber
that transmit signals away from the soma to other neurons or muscles
e. Myelin sheath – many axons wrapped in cells with a high concentration
of myelin. Insulating material, from glial cells, that encases some
neurons. Speeds up transmissiono of info.
i. Multiple Scleroris due to deterioration of myelin sheath.
f. Terminal buttons – small knobs that secrete chemicals called
neurotransmitters. At end of axons in clusters.
g. Synapse – point at which neurons connect. Junction where info is
transmitted from one neuron to another.
B. The Neural Impulse: Using Energy to Send Information
1. The Nueron at Rest: A Tiny Battery
a. Neural impulse is a complex electrochemical raction.
b. The resting potential of a neuron is it’s stable, negative charge when the
cell is inactive. (Potential Energy of a Nueron).
2. The Action Potential – brief shift in a nueron’s electrical charge that travels
along an axon.
a. Absolure Refractory Period – the minimum length of time after an action
potential during which another action potential can not begin (down
3. The All or None Law
a. Either the neuron fires or it doesn’t, and its action potentials are always
the same. i.e. weaker stimuli don’t produce smaller action potentials.
b. However, they can change the rate of action potentials. A stronger
stimulus will make for more rapid action potentials in a shorter period of
C. The Synapse: Where Nuerons Meet
1. Sending Messages: Chemicals as Couriers
a. Synaptic Cleft – a microscopic gap between the terminal button of one
neuron and the cell membrane of another neuron.
1/5 Oct/6/2003 CHANAPS
Notes From Reading
C HAPTER 3: THE BIOLOGICAL BASIS OF B EHAVIOR
b. Presynaptic Neuron – sends the signal, postsynaptic neuron receives the
c. Neurotransmitters – chemicals that transmit info from one neuron to
2. Receiving Signals: Postsynaptic Potentials
a. Postsynaptic Potential (PSP) – a voltage change at a receptor site on a
postsynaptic cell membrane.
i. Graded – vary in size and increase/decrease the possibility of a
neural impulse in the receiving cell in proportion to the amount of
b. 2 Types of Signals:
i. Excitatory PSP is a positive voltage change that increases the
likelihood that postsynaptic neuron will fire action potentials.
ii. Inhibitory PSP negative voltage change that decreases the likelihood
that the postsynaptic neuron will fire action potentials.
c. Reuptake – process in which neurotransmitters are sponged up from the
synaptic cleft by the presynaptic membrane.
3. Integrating Signals: A Balancing Act
a. State of a Neuron is the weighted balance between excitatory and
D. Neurotransmitters and Behavior
Good Table 3.1 – Common Nuerotransmitters and Their functions
1. Acetylcholine (ACh)
a. Only transmitter between motor neurons and voluntary muscles.
b. Contribute to attention, arousal, memory.
c. Agonist – chemical that mimics the action of a neurotransmitter –
PRODUCE PSP after binding to receptor sites (i.e. Nicotine).
d. Antagonist – opposes the action of a neurotransmitter. Bind to receptor
sites but DO NOT PRODUCE PSP, but instead block action of normal
2. Monoamines – regulate everday behavior such as voluntary movements
a. Includes 3 nuerotransmitters – dopamine (DA), norepinephrine, and
b. Serotonin releasing neurons appear to play a role in regulation of sleep
and wakefulness. may control aggressive behavior in animals.
c. Abnormal levels of monoamines has been linked to psych disorders –
depression from lower levels.
d. Abnormalties in activity linked to schizophrenia
3. Endorphins – family of internally produced chemicals that resemble opiates
(morphine, opium) in structure and effect
II. Organization of the Nervous System
A. The Peripheral Nervous System
Those nerves that lie outside the brain and spinal cord.
1. Nerves are bundles of neron fibbers (axons) that are routed together in the
peripheral nervous system.
2/5 Oct/6/2003 CHANAPS
Notes From Reading
C HAPTER 3: HE BIOLOGICAL B ASIS OFB EHAVIOR
2. Somatic Nervous System – nerves that connecet to voluntary skeletal muscles
and to sensory receptors. (skin, muscles, joints
a. Afferent Nerve fibers are axons that carry info INWARD to the central
nervous system from the periphery of the bod