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Unformatted text preview: Drugs and Behavior
and Drugs – part I
PSY 291 PSY number
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to internal and external
system and the
changes in the
endocrine system =
environment by Homeostasis This process uses endogenous chemicals to maintain
both the body’s physiological and psychological stability.
By understanding mechanisms regulating homeostasis, we may be able
to better identify drug treatments that are effective. Introduction to Nervous Systems
All nervous systems consist of specialized
nerve cells called neurons and glia
(supporting cells). Neurons receive and send information Communication by both chemical and
electrical Homeostatic functions of the nervous systems
is achieved through the activity of neurons CNS Support Cells
CNS Glia (neuroglia, glial cells) – supporting cells of
the CNS. Surround neurons and hold them in place
Supply nutrients and oxygen to neurons
Insulate one neuron from another, preventing neural
messages from getting scrambled
messages Form the myelin sheath around axons
Form Destroy pathogens and remove dead neurons
Destroy Nerve cell (neuron) specializations
Basic Structure Soma – cell body of a neuron which contains the
nucleus. Dendrite – branched, treelike structure attached to the
soma; receives information from other neurons.
soma; Synapse – junction between the terminal button of an
axon and the membrane of another neuron.
axon Axon – long, thin, cylindrical structure that conveys
information from the soma of a neuron to its terminal
buttons. Terminal Buttons – bud at the end of a branch of an
axon. A typical neuron 1. Carries impulses toward or away from
2. Communicates with other neurons or
target cells by releasing the
3. Has cell body with the nucleus.
4. Has cell processes:
a. axon – carries signals away from
the cell body. Could be myelinated or
b. dendrites – carry signals toward the
cell body. Unmyleinated. Transfer of messages by neurons
Transfer Dendrite- receiving region of neuron
receiving affected by a chemical messenger (NT) either excites or inhibits If excited, electrical impulse moves down the
axon to the…
axon Terminal- the sending region
the NTs (chemical messengers) are released Sending Messages by Neurons
Each neuron in the central nervous system
is in close proximity with other neurons.
is Although they are close, neurons never
Synapse – the point of communication
between one neuron and another
between Synaptic cleft – the gap between neurons at
the synapse (~20 nm)
the Synaptic vesicles transport NTs to the
terminal membrane at the synapse
terminal By fusing with the terminal membrane they
release contents into the cleft
release Synapses The axon terminal (presynaptic element) contains: Mitochondria that provide energy for axon
Synaptic vesicles (round objects) that contain
neurotransmitter. Presynaptic Membrane – membrane of a terminal
button that lies adjacent to the postsynaptic
membrane and through which the neurotransmitter
Postsynaptic Membrane – cell membrane opposite
the terminal button in a synapse. Synapse Synapses
Synapses Excitatory synapse—initiates an impulse in
the receiving neuron when stimulated,
causing release of neurotransmitters or
increasing activity in target cell
increasing Inhibitory synapse—diminishes likelihood
of an impulse in the receiving neuron or
reduces the activity in other target cells
Neurons can send discrete excitatory or
inhibitory messages (# of vesicles) to their
target A receiving neuron or target cell may have
many excitatory and inhibitory synapses.
many Final cellular activity is a summation of
these many excitatory and inhibitory
synaptic Excitatory neuron Inhibitory neuron Target neuron Communication Between Neurons
Communication Neural Integration – process by which inhibitory
and excitatory postsynaptic potentials summate
and control the rate of firing of a neuron.
and Types of Neurons
Types Sensory Neuron – neuron that detects
changes in the external or internal
environment and sends information about
these changes to the CNS.
these Motor Neuron – neuron that controls the
contraction of a muscle or the secretion of a
gland. Interneuron – neuron located entirely
within the CNS, connecting other neurons.
within Reflex Arc – Withdrawal Reflex
Withdrawal Reflex Arc – Withdrawal Reflex
Withdrawal Can be modulated by brain.
Brain signals inhibitory interneuron to prevent
muscle contraction. Patella reflex (stretch reflex) Crossed
reflex Transfer of messages by neurons
Transfer Neurotransmitters travel and attach to large
proteins in the membrane of the target cells.
proteins The proteins are called receptors.
receptors Activation of receptors causes a change in the
activity of the target cell; the target cells can
be other neurons or cells that make up organs,
muscles, or glands.
muscles, Receptors only interact with molecules that
have specific configurations
have Lock & Key hypothesis Agonists—substances or drugs that activate
receptors Antagonists—substances or drugs that
attach to receptors and prevent them from
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- Fall '11