Module 4 Notes
-- Biology, Behavior, and Mind--
Franz Gall proposed “phrenology,” that studying the bumps on a person’s head revealed their
mental abilities and character traits.
Phrenology succeeded in focusing attention on “localization of function,” that different brain
areas serve different functions.
Biological perspective: concerned with the links between biology and behavior.
Humans are biopsycho-social systems.
Neuron: Nerve cell; basic building block of the nervous system
Neurons are composed of a cell body and its branching fibers.
Dendrites: fibers that receive information and pass it to the cell body.
Axons: fibers that pass the information through terminal branches to adjacent neurons.
Myelin sheath: Layer of fatty tissue that insulates axons and speeds their impulse.
As myelin sheath is laid down until age 25, neural efficiency, judgment and self-control grows.
Multiple Sclerosis: degeneration of myelin sheath causes muscle communication to slow and
eventual loss of muscle control.
Neurons transmit messages when stimulated by signals from our senses, or when triggered by
chemical signals from adjacent neurons.
Action Potential: neural impulse; brief electrical charge travelling down an axon
Brain is more complicated than a computer, but takes longer to execute simple responses.
Axons generate electricity from chemical events.
Resting potential: state in which the outside of an axon contains cations, and the inside contains
Axon membrane is selectively permeable.
When a neuron fires, the first section of the axon temporarily allows sodium ions to pass into
the membrane, creating an internal positive charge, and external negative charge. This reversal
of charge is called depolarization. Depolarization in one section creates a domino effect, with
each depolarization causing the subsequent gate to open. This creates a wave of depolarization.
Resting pause/Refractory period: Sodium ions pumped back outside of the cell. Then the neuron
can fire again.
Neural signals can be excitatory or inhibitory
If the excitatory signal minus the inhibitory signals exceed a threshold, ( minimum stimulation
required for a neural impulse) then the neuron will generate an action potential.
All or none response: Increasing stimulation to a neuron above threshold will not increase
We detect intensity of a stimulus by more/less neurons firing.
How Neurons Communicate
Synapse: Space between the axon and dendrite of adjacent neurons.
Neurotransmitters: chemical messengers that cross the synaptic cleft. When an action potential reaches the terminal branches of the neuron, it triggers the release of
neurotransmitters in vesicles. The vesicles fuse into the membrane of the terminal branches and
release the neurotransmitter across the synaptic cleft. The neurotransmitters bind to receptor
sites on the adjacent neuron. At this receiving site, the neurotransmitters unlock tiny channels
allowing for sodium ions to rush into the membrane at that receiving site, thus action potential
is generated again.
Reuptake: Sending neuron reabsorbs excess neurotransmitters.
How Neurotransmitters Influence Us
Acetylcholine is present at every motor neuron-skeletal muscle junction.
If Ach binds to muscle cell receptors, our muscle can contract. If Ach doesn’t bind, our muscles
cannot contract and are paralyzed.
Endorphins (morphine within): natural, opiate-like neurotransmitters linked with pain control
How Drugs and other Chemicals Alter Neurotransmission
Those people addicted to opiates such as heroin, their bodies stop making natural opiates
themselves. Thus when the drug is withdrawn, the body has no opiates to cope with pain,
resulting in severe discomfort.
Agonists: Similar in structure to the neurotransmitter so they can bind to receptor sites. They
also have the ability to unlock the tiny channels in the receptor site as the original
neurotransmitter would. Opiates are agonists that make a “high” by amplifying sensations of
pleasure or arousal.
Antagonists: Are similar in structure to the neurotransmitters so they can bind to the receptor
sites. However, they cannot unlock tiny channel to generate a neural impulse, and at the same
time, block the original neurotransmitter from doing so.
Botulin blocks Ach and causes paralysis.
-- The Nervous System—
Central Nervous System: consists of brain and spinal cord; body’s decision maker.
Peripheral Nervous system: sensory and motor neurons that connect the CNS to the rest of the
body. Relays information to the CNS, and carries CNS decisions to rest of body.
Nerves: Bundled axons that form neural cables, connecting the CNS to muscles, glands, and
Sensory neurons: carry incoming information from sensory receptors to the CNS
Motor neurons: carry outgoing information from the CNS to muscles and glands.
Interneurons: neurons in the CNS that communicate internally and intervene between sensory
input and motor output.
Our complexity resides in our interneuron systems.
--The Peripheral Nervous System—
Somatic Nervous System: enables voluntary control of skeletal muscles.
Autonomic Nervous System: Controls our glands and muscles of our internal organs, with
functions such as glandular activity, heartbeat and digestion. This system operates
autonomously. Sympathetic nervous system: arouses the body and mobilizes energy for stressful situations. It
dilates pupils, increases heart rate, increase blood pressure and blood sugar, slows digestion
and causes perspiration. Parasympathetic nervous system: calms the body and conserves
energy. Pupils contract, heart rate is slower, blood pressure and sugar is slower, digestion
returns to normal.
--The Central Nervous System—
Neural network: neurons clustered into workgroups
Spinal cord connects brain to PNS; ascending fibers carry sensory information to the brain, and
descending fibers carry motor information to the rest of the body.
Reflex: simple, automatic response to a sensory stimulus
Simple Reflex Pathway: Sensory neuron carries information from external receptor to a motor
neuron via an interneuron in the spinal cold. The motor neuron delivers the message to muscle
or gland and it generates an appropriate response.
^ Brain DOES NOT receive the message.
--The Endocrine System—
Endocrine System: Is the body’s slow chemical messaging system, composed of glands that
secrete hormones into the blood stream.
Hormone: Chemical messenger produced in a gland and secreted direction into the bloodstream
to affect other body parts.
Some hormones are chemically similar to neurotransmitters.
Endocrine messages are longer lasting than neural messages. For example, upset feelings linger
far longer than our awareness of what upset us.
In moments of danger, ANS signals adrenals glands above kidneys to release epinephrine and
norepinephrine to raise blood sugar levels and increase heart rate.
The pituitary gland is controlled by the hypothalamus.
Pituitary releases oxytocin, used in muscle contractions during childbirth, and growth hormone.
Feedback System: Brain Hypothalamus Pituitary Gland Endocrine Glands Hormones