Biological Processes

Chapter 3pp. 74-121

Biological Aspects of Psychology

• How does the nervous system communicate internally?

• How does the brain initiate and coordinate behaviour?

• How does the body regulate growth and other internal functions?

• How do we adapt, store, and transmit the genetic code?

• Neuroscience– An interdisciplinary field of study directed at understanding the brain and its relations to behaviour

• Central Nervous System– The brain and the spinal cord

• Peripheral Nervous System– The network of nerves that link the central nervous system with the rest of the body

Neuroscience

The Nervous System

Fig. 2.20

Anatomy of a Neuron

1.Dendrites2.Soma3.Axon4.Nodes of Ranvier5.Terminal buttons6.Synapse

Axons and Dendrites

Communication

Neurons1.Sensory neurons2.Interneurons3.Motor neurons

Afferent and Efferent Signals

Glial Cells(Example: Astrocytes)

“Message” Within a Neuron: Electrical

“Messages” Between Neurons: Chemical

The Composition of Intracellular and Extracellular Fluids

Neuronal Communication: Resting Potential

Polarization: Negative sign indicates that the inside is negative in comparison to the outside

Neuronal Communication: Resting Potential

Fig. 2.25

Myelin Sheath and Nodes of Ranvier

Propagation in Unmyelinated and Myelinated Axons

Generating Action Potentials

• Change in potential, primarily because of messages from other neurons

• Excitatory messages– Depolarization: Cell loses the negative charge

• Inhibitory messages– Hyperpolarization: Cell becomes more negatively charged

Neurotransmitters

• When action potential reaches the end of the axon, it triggers vesicles (sacs) in the terminal buttons to release chemicals called neurotransmitters

• These activate receptors in the postsynaptic membrane

• May be excitatory or inhibitory

Fig. 2.30

Example Neurotransmitters

• Acetylcholine– Involved in triggering muscles to contract

• Dopamine– Inhibitory effects; dampens and “smoothes out” neural messages

• Serotonin– Involved in sleep and dreaming

• Gamma-amino-butyric acid (GABA)– Involved in regulating anxiety

Drugs and the Brain

• Agonists– Mimic the action of neurotransmitters– Example: Nicotine and acetylcholine

• Antagonists– Block the action of neurotransmitters– Example: Curare and acetylcholine

• Neuromodulators– Increase or decrease effectiveness of other neurotransmitters

– Example: Endorphins

The Communication Network: Reflexes

• Reflex–A largely automatic body movement

–Controlled by a simple network of sensory neurons, interneurons in the spinal cord, and motor neurons

A Simple Reflex Pathway

Central and Peripheral Nervous System

• Central Nervous System–Brain and spinal cord

• Peripheral Nervous System–Somatic–Autonomic1. Sympathetic2. Parasympathetic

Central and Peripheral Nervous System

• Automatic system– Nerves that control the more automatic needs of the body, such as heart rate

• Sympathetic system– The division of the automatic nervous system that helps the body respond to emergencies

• Parasympathetic system– The division of the autonomic nervous system that helps the body calm down

Brain Damage

• Studying brain damage is one of the oldest methods for investigating brain function

• To establish structure-function relationship, necessary to observe in a controlled way effects of systematic and localized remove of tissue

Lesion

Recording Electrodes Surgically Implanted in a Rat’s Brain

Talking and Listening to the Brain

• Transcrancial magnetic stimulation (TMS)

• Electroencephalograph (EEG)• Event-related potentials (ERP)• Computerized tomography (CT)• Position emission tomography (PET)

• Magnetic resonance imaging (MRI)

Evoked Potentials

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Transcranial Magentic Stimulation (TMS)

CT Scans

PET Scans Show Patterns of Brain Activation

Will Imaging Technologies Allow Us to “Read” People’s Minds?

Brain Structures

1.Hindbrain

2.Midbrain

3.Forebrain

Hindbrain and Midbrain

Hindbrain and Midbrain

Forebrain

The Cerebral Cortex

The Case of Phineas Gage

• Illustrates effects of damage to the cerebral cortex

• Railroad construction accident, 1848

• Iron rod driven through skull• Frontal lobe damage• Gage survived• Personality changes

– Unpredictable– Crude

Hemispheric Lateralization

• In general, left side of cortex handles information from the right side of body/space, and vice versa– With vision, each half of each eye sends information to different side of the brain

– Information does eventually go to both hemispheres•Corpus callosum transfers information across hemispheres

Visual Processing inThe Two Hemispheres

The hemispheres Can Be Separated

Hemispheric Specialization

• Right hemisphere– Spatial tasks, emotions

• Left hemisphere– Verbal tasks

• Is there any such thing as being “left brained” or “right brained?”– Not according to well-designed studies– Hemispheres normally share information, work together

Endocrine System: Regulating Growth and Internal Functions

• Endocrine system

• Hormones– Like nervous system, a means of communication

– Unlike nervous system, relatively slow, longer-lasting messages

– Coordinate with nervous system

The Endocrine System

http://www.clinica-verde.com/pages/conditions-treated/endocrine-system.php

Flight or Fight Response

Gender, Hormones, and Psychology

• Before birth, hormones are released by pituitary gland and initiate developments in reproductive anatomy, determining sex organs

• Evidence exists that male and female brains differ somewhat anatomically, although such differences are often exaggerated

• Difficult to separate effects of biology (nature) from the ongoing influences of the environment (nurture)

Natural Selection

• Natural Selection– Differential production and survival of offspring by species members with advantageous traits

• Traits are inherited via genes

• Traits can be psychological as well as physical– More likely to be passed to offspring if they aid in finding a mate, increase chance of survival

• Evolutionary Adaptations: Traits that enhance survival, fitness

How Genes Work

• Chromosomes: Strips of DNA– Half come from mother; half from father

• Genes: Segments of chromosomes that influence particular characteristicsExamples: height, hair colour

• Dominant genes may mask recessive ones

• Genes may mutate (spontaneously change)

How Genes Translate into Traits

• Phenotype– What you can observe about the trait– Example: A person’s weight

• Phenotype influenced by– Genotype (genes)– Environment

• So “final product” usually influenced heredity AND environment

Genes and Behaviour

1. Family Studies

2. Adoption Studies

3. Twin Studies

Evolutionary Adaptations and Human Behaviour

• Environment of Evolutionary Adaptedness (EEA)– The environment, or environments, in which a species’ evolutionary adaptations were selected