Module 4 Page 1
Neural and Hormonal Systems
Biology, Behaviour & Mind
German physician Franz Gall proposed phrenology; studying bumps on the skull can reveal one's
mental abilities and character traits. It succeeded in focusing attention on the localization of
function - the idea that various brain regions have particular functions
Biological Perspective - concerned with the links between biology and behaviour includes
psychologists working in neuroscience, behaviour genetics, and evolutionary psychology.
They have discovered that, the body is composed of cells, these cells conduct electricity and
communicate through sending messages between tiny gaps, specific brain systems serve specific
functions, we integrate these various brain systems to construct our experience of
sights/sounds/meanings/memories/pain/passion, and our adaptive brain is wired by our
We realize we are a system composed of smaller and smaller subsystems
Neurons - a nerve cell; the basic building block of the nervous system
Dendrites - a neuron's bushy, branching extensions the receive messages and conduct impulses toward
the cell body
Axon - the neuron extension that passes messages through its branches to other neurons or to muscles
or glands. Can extend several feet though the body.
Myelin Sheath - a fatty tissue layer segmentally encasing the axons of some neurons; enables vastly
greater transmission speed as neural impulses hop from one node to the next. Laid down up until age
25. If this degenerates, multiple sclerosis occurs as communication to muscle slows with eventual loss of
Action Potential - a neural impulse; a brief electrical charge that travels down an axon. The speed the
neural impulse travels depends on the type of fibre.
In the neuron's chemical-to-electricity process, ions (electronically charged atoms) are
The fluid outside an axon's membrane has mostly positive charged ions, while the fluid inside
the axon's membrane has mostly negative charged ions. This is called Resting Potential.
The axon's surface is selective in what it allows through, calling it Selectively Permeable.
When a neuron fires, the first section of axon opens its gates & positively charged ions flood
through the cell membrane. This depolarizes that axon section causing another to open and so
on, like a line of dominos. Module 4 Page 2
During the Refractory Period (resting pause), the neuron pumps positively charged ions back
Threshold - the level of stimulation required to trigger a neural impulse. (If excitatory signals
minus inhibitory signals exceed a minimum intensity).
A strong stimulus can trigger more neurons to fire or fire more often, but it cannot affect the
action potential's strength or speed it travels down an axon.
How Neurons Communicate
British physiologist Sir Charles Sherrington noticed the brief interruption in the transmission of a signal
down a neural pathway. The meeting point between neurons is a Synapse - the junction between the
axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this
junction is called synaptic gap/synaptic cleft.
When action potential reaches the knob-like terminals at the axon's end, it triggers release of chemical
messengers called Neurotransmitters - chemical messengers that cross the synaptic gaps between
neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to
the receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a
Reuptake - a neurotransmitters re-absorption by the sending neuron