1Copyright © 2005 Pearson Education Canada Inc.

Evolutionary Psychology

The biological theory of evolution assumes natural selection is a key factor in how a species changes over time

Characteristics that help an organism survive are passed on to future generations

2Copyright © 2005 Pearson Education Canada Inc.

Evolutionary Psychology

Adaptation occurs when a trait has increased in a population

Individuals with the adaptive trait are more likely to survive and reproduce

3Copyright © 2005 Pearson Education Canada Inc.

The Genome

The genome is the total DNA blueprint of traits that can be inherited

Genetic mapping is the dividing the chromosomes into smaller fragments that can be mapped to reflect their respective locations

4Copyright © 2005 Pearson Education Canada Inc.

The Basics of Genetics

Behavioural Genetics is the study of both genetic and environmental contributions to variations in human behaviour

Heritability is the proportion of variation in a trait determined by heredity

5Copyright © 2005 Pearson Education Canada Inc.

The Basics of Genetics

Each human cell contains 23 pairs of chromosomes

Chromosomes are strands of DNA that carry genes

6Copyright © 2005 Pearson Education Canada Inc.

The Basics of Genetics

Genes are the fundamental units of heredity

Genetically determined traits are controlled by pairs of genes

7Copyright © 2005 Pearson Education Canada Inc.

The Basics of Genetics

A genotype is a person’s genetic make-up, which is fixed at birth

The phenotype is a person’s observable characteristics

8Copyright © 2005 Pearson Education Canada Inc.

The Basics of Genetics

Recessive members of gene pairs appear in the phenotype only if both members of the pair are recessive

A dominant gene is always expressed if it is inherited

9Copyright © 2005 Pearson Education Canada Inc.

The Neuron

The neuron is the basic unit of the nervous system

10Copyright © 2005 Pearson Education Canada Inc.

11Copyright © 2005 Pearson Education Canada Inc.

12Copyright © 2005 Pearson Education Canada Inc.

Types of Neurons

Afferent neurons carry messages to the brain and spinal cord

Efferent neurons carry messages from the brain and spinal cord to other structures of the body

13Copyright © 2005 Pearson Education Canada Inc.

Figure 2.2 The Action of Afferent and Efferent Neurons

14Copyright © 2005 Pearson Education Canada Inc.

Types of NeuronsSensory neurons are afferent neurons that carry information from the sense organs to the brainMotor neurons are efferent neurons that carry information from the brain and spinal cord to muscles and glandsInterneurons connect other types of neurons

15Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

The electrical process is created by a thin membrane around the neuron

In the normal resting state, the interior of a neuron carries a negative electrical charge

16Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

Activity within neurons is electrical Activity between neurons is chemical

17Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

The electrical process is created by a thin membrane around the neuron

In the normal resting state, the interior of a neuron carries a negative electrical charge

18Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

The exterior carries a positive electrical charge

The difference in interior and exterior charges creates a state of polarization

19Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

The action potential (or spike charge) is an electrical current that travels down an axon

It is initiated by a rapid reversal of the polarization of a neuron’s cell membrane

20Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

When stimulated to the action potential, gates in a neuron’s membrane open

The action potential occurs in an all-or-none fashion

21Copyright © 2005 Pearson Education Canada Inc.

Figure 2.5 Generation of an Action Potential

22Copyright © 2005 Pearson Education Canada Inc.

Electrochemical Processes

After firing, a refractory period occurs

Normal stimulation will not activate the neuron

23Copyright © 2005 Pearson Education Canada Inc.

Neurotransmitters

When an action potential moves down an axon, it causes the release of neurotransmitters

24Copyright © 2005 Pearson Education Canada Inc.

The Neural Synapse

The synapse is a small space between the axon terminals of one neuron and receptor sites of another

25Copyright © 2005 Pearson Education Canada Inc.

Figure 2.4 The Synapse

26Copyright © 2005 Pearson Education Canada Inc.

Neurotransmitters

Neurotransmitters are chemicals that move across the synaptic space

They communicate with other neurons by binding to receptors

27Copyright © 2005 Pearson Education Canada Inc.

Neurotransmitters

After communicating, the neurotransmitter may be neutralized or taken back by the neuron that released it

The process of taking neurotransmitters back in is called reuptake

28Copyright © 2005 Pearson Education Canada Inc.

Neurotransmitters

A change in the membrane of a neuron after receiving neurotransmitters is called a postsynaptic potential

29Copyright © 2005 Pearson Education Canada Inc.

Neurotransmitters

Sometimes neurotransmitters cause a neuron to fire more easily

They create an excitatory postsynaptic potential

30Copyright © 2005 Pearson Education Canada Inc.

Neurotransmitters

At other times neurotransmitters inhibit a neuron from firing

This is an inhibitory postsynaptic potential

31Copyright © 2005 Pearson Education Canada Inc.

Some Neurotransmitters

GABA Serotonin Acetylcholine Endorphins