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