Unit III:Biological Bases of BehaviorMs. Justice

AP Psychology

2014-2015

Unit III - Overview

9 – Biological Psychology & Neurotransmission

10 – The Nervous & Endocrine Systems

11 – Studying the Brain & Older Brain Structures

12 – The Cerebral Cortex

13 – Brain Hemisphere Organization & the Biology of Consciousness

14 – Behavior Genetics: Predicting IndividualDifferences

15 – Evolutionary Psychology

Unit III:Biological Bases of BehaviorModule 9

Biological Psychology & Neurotransmission

Biology, Behavior, and Mind 9-1

Biology, Behavior, and Mind

• Phrenology - Franz Gall was correct in his

assumptions that different parts of the brain

do control different aspects of behavior…

but that’s about it

• Biological psychology - study the

links between biological activity

and psychological events

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Neurons 9-2

Neurons

The body’s information system is built from billions of interconnected cells called neurons.

Hi! I’m a neuron… some of my friends call me “nerve

cell”

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Neuron

A nerve cell, or a neuron, consists of many different parts:

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Parts of a Neuron

Cell Body: Life support center of the neuron.

Dendrites: Branching extensions at the cell body. Receive messages from other neurons.

Axon: Long single extension of a neuron, covered with myelin [MY-uh-lin] sheath to insulate and speed up messages through neurons.

Terminal Branches of axon: Branched endings of an axon that transmit messages to other neurons.

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Action Potential

A neural impulse. A brief electrical charge that travels down an axon and is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane.

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Action Potential 9-2

Threshold

Each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity (threshold) the neuron fires an action potential… or if the excitatory party animals outvote the inhibitory party poopers, the party’s on.

threshold: the level of stimulation required to trigger

a neural impulse

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How Neurons Communicate 9-3

Synapses

Synapse [SIN-aps] - a junction between the axon tip of the sending neuron and the dendrite or cell body

of the receiving neuron.

This tiny gap is called the synaptic gap or cleft (which is less than a millionth of an inch wide!)

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Neurotransmitters

Neurotransmitters are chemicals released

from the sending neuron that travel

across the synapse and bind to receptor sites on

the receiving neuron, thereby influencing it to

generate an action potential.

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Reuptake

Excess neurotransmitters in the synapse are reabsorbed

into the sending neurons through the process of

reuptake.

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9-3How is a flushing toilet like a neuron firing?

•All-or-nothing principle – the toilet either flushes completely or not at all; it doesn’t

flush a little or a lot

•Direction of impulse – the toilet only flushes one way, the impulse can’t come the

other direction (you hope!)

•Refractory period – after you flush the toilet, it won’t flush again for a certain period

of time, even if you push the handle repeatedly

•Threshold – you can push the handle a little bit, but it won’t flush until you push the

handle past a certain point (this corresponds to the level of excitatory

neurotransmitters that a neuron must absorb before it will fire)

•Resting potential –the toilet is waiting to fire, and the water in the tank represents

the overall negative charge inside the neuron waiting for depolarization

•Action potential – opening the flap in the tank and the water rushing through the

pipes

How is a flushing toilet like a neuron firing?

9-3

How Neurotransmitters Influence Us

9-4

Table 9.1, p. 82

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Agonist versus Antagonists 9-4

Figure 9.6, p. 83