Chapter 2The Biological Basis of
Behavior
IntroductionThe brain is the control center of
everything that we say and do!Complex organBillons of cellsOverlapping pathways and networks
Plasticity= ability to adapt to new environmental conditions
Psychobiology= biological bases of behavior and mental processes
IntroductionNeuroscience= study of the brain and
nervous systemNeuropsychologists= study brain’s
influence on behavior
NeuronsAka nerve cellsBody contains approximately 100 billionVaries widely in size and shape Specialized to receive and transmit
information
Neuron TypesSensory neurons= carry messages from
sense organs to the spinal cord or brainMotor neurons= carry messages from the
spinal cord or the brain to the muscles and glands
Interneurons= carry messages from one neuron to another
Glial cells= hold neurons in place, provide nourishment, remove waste, prevent harmful substances to passing into the brain
The Neural ImpulseYes-no, on-off electrochemical impulsesIons= electrically charged particles Resting Potential = electrical charge
across a neuron membraneExcess (+) ions on outside, (--) on the inside
Neural Impulse= the firing of a nerve cellPolarization= a resting neuron; (--) on
insideDepolarization= inflow of (+) sodium ions
sets off a chain reaction
The Neural Impulse (cont)Threshold of Excitation= the level the impulse
must exceed to cause a neuron to fireAll-or-none law= the neuron will fire or it won’tAbsolute refractory period= time after a
neuron has fired that it WILL NOT fire not matter what the impulse
The SynapseNeurons are NOT connectedTiny space between called synaptic
spaceTerminal button= end of axon branchSynaptic Vesicles = tiny sacs in
terminal button that release chemicals into the synapse
Neurotransmitters= chemicals release by the synaptic vesicles
Neuron Toilet Worksheet
NeurotransmittersAcetylcholine (Ach)= acts where neurons
meet skeletal musclesRole in arousal, attention, memory, & motivationLinked to Alzheimer’s disease
Dopamine= assoc. with voluntary movement, learning, memory & emotionsParkinson’s disease
Serotonin= “mood molecule” (sets emotional tone)Half empty or half full
Endorphins= turn down neurons that transmit pain messages to the brain.
**review chart on page 54**
NeurotransmittersImbalances have been linked to mental illnessSchizophrenia (over abundance of dopamine)Depression (undersupply of serotonin &
norepinephrine)
Nervous System OrganizationIncludes the brain and the spinal cordContains 90 % of the body’s neurons Peripheral Nervous System= division of
the nervous system that connects the CNS to the rest of the body
The Brain (cont.)
The Brain (cont.)Cerebellum= sense of balance and
coordinating body’s actions
The Limbic System is a doughnut-shaped system of neural
structures at the border of the brainstem and cerebrum, associated with emotions such as fear, aggression and
drives for food and sex. It includes the hippocampus, amygdala, and hypothalamus.
The Limbic System
Amygdala
The Amygdala [ah-MIG-dah-la] consists of two lima bean-sized neural clusters linked to the emotions of fear and
anger.
HypothalamusThe Hypothalamus
lies below (hypo) the thalamus. It directs several maintenance activities like eating,
drinking, body temperature, and
control of emotions. It helps govern the
endocrine system via the pituitary gland.
The Brain (cont.)Midbrain= important for hearing and sight
Pain is registered here (one of many)Thalamus= “relay station” for incoming
messages from the sense receptors (except for smell)
Reticular Formation= ALERT system; network of neurons
Pons- regulate sleep wake cyclesMedulla= regulates respiration, heart rate,
blood pressure
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