Biology and Behavior
Chapter 2
Part I
The Biological Perspective
• Psychological approach that emphasizes bodily
events and changes associated with actions,
feelings and thoughts.
• This perspective involves such topics as:
–
–
–
–
–
–
The nervous system
Neurons & neurotransmitters
Hormones
Brain chemistry
Heredity
Evolutionary influences
The Nervous System
• Two parts of a nervous system
– Central nervous system
• The brain and the spinal cord
– Peripheral nervous system
• Connects the central nervous system to all other parts of
the body
The Central Nervous System
• Brain.
• Spinal cord.
– A collection of neurons and
supportive tissue running
from the base of the brain
down the center of the back
– Protected by spinal column.
Central Nervous System
Peripheral Nervous System
• Peripheral nervous system (PNS)
– The nerves connecting the central nervous system
to the rest of the body
– Contains two subdivisions
• Somatic division
• Autonomic division – contains two divisions
– Sympathetic division
– Parasympathetic division
Peripheral Nervous System
Peripheral Nervous System
• Somatic
– Includes the nerves that are connected to sensory
receptors and skeletal muscles.
• Autonomic
– The sympathetic nervous system mobilizes bodily
resources and increases the output of energy
during emotion and stress.
– The parasympathetic nervous system operates
during relaxed states and that conserves energy.
Neurons and the
Neurotransmitters
• Neuron
– A specialized cell that conducts impulses
through the nervous system and contains
three major parts—a cell body, dendrites,
and an axon
Structure of a Neuron
• Dendrites
– receive information from other
neurons and transmit towards
the cell body
• Cell body
– keeps the neuron alive and
determines whether it will fire.
• Axon
– extending fiber that conducts
impulses away from the cell
body and transmits to other
cells.
Structure of a Neuron
• Myelin Sheath
– Fatty insulation that may surround the axon of a
neuron.
How Neurons Communicate
• Axon terminals release
neurotransmitter.
• Neurotransmitter enters
synaptic gap.
• Neurotransmitter binds
to receptors that it fits.
Neurons and the
Neurotransmitters
• Glial cells
– Cells that help to make the brain more efficient by
holding neurons together, removing waste products
such as dead neurons, making the myelin coating
for the axons, and performing other manufacturing,
nourishing, and cleanup tasks
– Synapse
– The junction where the axon of a sending neuron
communicates with a receiving neuron across the
synaptic cleft
Action Potential
• A brief change in electrical voltage which
occurs between the inside and outside of an
axon when a neuron is stimulated. It
produces an electrical impulse.
Action Potential
Neurotransmitters
• Neurotransmitter
– A chemical that is released into the synaptic cleft
from the axon terminal of a sending neuron, crosses
a synapse, and binds to appropriate receptor sites
on the dendrites or cell body of a receiving neuron,
influencing the cell either to fire or not to fire
• Receptors
– Protein molecules on the dendrite or cell body of a
neuron that will interact only with specific
neurotransmitters
Neurotransmitters
• A chemical substance that is released by a
transmitting neuron at the synapse and that
alters the activity of a receiving neuron.
Neurotransmitters
• Action of neurotransmitters
– Excitatory
• Influencing the neurons to fire
– Inhibitory
• Influencing neurons not to fire
Major Neurotransmitters
• Serotonin
– A neurotransmitter that plays an important role in
regulating mood, sleep, aggression, and appetite
• Dopamine
– A neurotransmitter that plays a role in learning,
attention, and movement
• Acetylcholine (ACh)
– A neurotransmitter that plays a role in learning,
memory, and rapid eye movement (REM) sleep and
causes the skeletal muscle fibers to contract
– Glutamate
– Primary excitatory neurotransmitter in the brain
Major Neurotransmitters
• Epinephrine
– A neurotransmitter that affects the metabolism
of glucose and energy stored in muscles to be
released during exercise
• Norepinephrine
– A neurotransmitter affecting eating and sleep
Major Neurotransmitters
• Glutamate
– Main excitatory neurotransmitter in the brain
• Gamma amino butryic acid (GABA)
– Main inhibitory neurotransmitter in the brain
• Endorphins
– Chemicals produced naturally by the brain
that reduce pain and positively affect mood
– “Runner’s high” is attributed to the release of
endorphins