1. Biological Bases of Behavior
Chapter 3

2. Biological Explanations of Behavior
Genes
DNA or genes that code for physical and psychological characteristics
Neurons
Electrical and chemical wiring of the body and brain
Nervous System
Combination of genes and neurons that handles information and communication

3. Mirror Neurons

4. Structure of the neuron

5. Neurons
Hardware:
Glia (means glue) – provides structural support and insulation to promote more efficient signaling
Neurons – nerve cells that constitute the basic building blocks of nervous system (100 billion in brain and spinal cord)
Soma – cell body
Dendrites – receive information
Axon – transmit away
Myelin sheath covers axons to increase speed of transmission
Terminal buttons – secrete neurotransmitters
Synapse – junction where information is transmitted

6. Electrical Activity of Neurons
Neurons do 2 things:
Generate electricity
Release chemicals
Both inside and outside the neuron are electrically charged atoms and molecules called ions
Positively charged sodium and potassium ions and negatively charged chloride ions flow back and forth across cell membrane
Higher concentration of negative ions on inside (-70 millivolts) means neuron is at rest (resting potential)

7. The Action Potential
If you sufficiently stimulate an axon, the cell membrane opens up briefly
Potassium ions then enter through the cell membrane openings
the interior voltage shifts from -70 to +40 millivolts
This brief shift in a neuron’s electrical charge is called an action potential
Can occur very quickly
All-or-none principle
Neurons either fire or they don’t
The rate of firing determines strength of stimulus
Thicker neurons transmit info quicker than thinner neurons
Ex. Local anesthetics attach to sodium ions to prevent passage of sodium into the cell membrane restricting firing potential

8. The neural impulse

9. How Neurons Communicate
Synaptic space
Tiny gap between axon terminal and the next neuron
Neurons do not touch one another…then how do they communicate???
Arrival of action potential at axon’s terminal button triggers release of neurotransmitters
Chemical substances that carry messages across the synapse either to excite other neurons or inhibit their firing
Neurotransmitters cross synaptic cleft and attach to receptor sites
Receptor sites and neurotransmitters fit like a lock-and-key

10. Overview of synaptic transmission.

12. How neurons are like toilets
The all-or-none principle: Toilet either flushes or not
Resting potential: Water in the represents the 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
Threshold: Toilet won’t flush properly until you push past a critical point
Direction of impulse: toilet only flushes one way; the impulse only travels one direction (you hope!)
Refractory period: after you flush, toilet won't flush again for a certain period of time, even if you push the handle repeatedly
Action potential: Represented by the water flowing down the pipe.
*/Written by Rob McEntarffer, Lincoln Southeast High School/* /Adapted from an idea by Jan Daniel/

14. Peripheral nervous system
Somatic (voluntary)
Autonomic (involuntary)
Sympathetic (increased heart rate, increase in respiration, increase in blood circulation, pupil dilates, digestion stops, etc.)
Parasympathetic (heart rate decreases, respiration decreases, digestion restarts, pupil constricts, blood circulation decreases, etc.)

15. Understanding the Brain
Neuropsychological tests
Measure verbal and nonverbal behaviors of victims of brain damage
Lesions
Specific nervous tissue is destroyed with electricity or chemicals or surgically remove portions of the brain
Electrical Recording
Electroencephalograph (EEG)
Brain Imaging
Computerized axial tomography (CAT scans): X-rays
Position Emission Tomography (PET scans): measures levels of glucose in brain
Magnetic Resonance Imaging (MRI): structures and functions

16. CAT scan
Brain of stroke victim
Lesioned
(damaged)
areas

17. PET scans
Normal brain
Alzheimer’s brain

18. MRI and fMRI scans
Standard MRI
functional MRI

19. Structures and functions of the brain
Brain is separated into two cerebral hemispheres connected by the corpus callosum
Neural bridge that acts as a major communication link between two hemispheres

20. The left and right brains
Lateralization: relatively greater localization of a function in one hemisphere or the other
Left hemisphere (verbal abilities and speech, mathematical and logical abilities, more active with positive emotions)
Right hemisphere (spatial relationships, mental imagery, musical and artistic abilities, more active with positive emotions

21. Four lobes Occipital lobe (vision) Parietal Lobe (touch)
Temporal lobe (hearing)
Frontal lobe (movement of the body)

25. The Endocrine System
Consists of glands that secrete chemicals into the bloodstream that help control bodily functioning
Mostly controlled by hypothalamus
Uses hormones (chemical substances released into the bloodstream by endocrine glands)
Pituitary gland: master gland
Gonads: sexual glands that release sex hormones

26. Evolution and Behavior
Based off of Darwin’s work on natural selection
Characteristics that increase likelihood of survival and ability to reproduce will be more likely preserved in population and become more common in species over time
THUS…Natural selection acts as a filter
Adaptation is product of natural selection
Changes that allow organisms to meet recurring environmental challenges so their survival and increases reproductive ability
Can be physical or behavioral
Woodpeckers long, strong beak allows to puncture hole in trees and eat insects
Chameleon’s blend into their environment to avoid predators
Rats won’t eat 2 unfamiliar foods at a time

27. Tips on evolutionary theory
Acknowledge the role of remote and proximate causes that influence behavior
There is only adaptation to environmental demands
Example
Male violence is a good adaptation in a time of war
Male violence is not such an adaptive trait in a time of peace

28. Genetic Influences on Behavior
Genotype
Specific genetic makeup of person
Ex. Commands of a computer program
Phenotype
Individual’s observable characteristics
Chromosomes: double-stranded molecule of DNA carrying genetic information
Every cell has 46 chromosomes in pairs (23 from each parent)
All genes encoded in various combinations of 4 chemical bases

29. Genetic relatedness and familial relatedness

30. Dominant, Recessive, or Polygenic Effects
Some genes are dominant, while other are recessive
Brown eyes dominant over blue eyes
Child has blue eyes only if both contribute a recessive gene for eye color
Polygenic
A # of gene pairs combine their influences to create a single phenotypic trait
Between 2 parents there are over 70 million chromosomal combinations

31. Is it Heredity or Environment?
Family Studies
Twin Studies
Compare trait similarities in identical and fraternal twins
Monozygotic and dizygotic
Adoption Studies
People who were adopted are compared on some characteristic with both their biological (share genetic info) and adoptive parents (share no genes)
Ex. schizophrenia

32. Twin studies of intelligence and personality