1. Biological Bases of Behavior
Unit III

2. Neural processing and the endocrine system

3. Neurons: The Origin of Behavior
Neurons: cells in the nervous system that communicate with one another to perform information-processing tasks
Components of neurons:
Cell body – coordinates information-processing tasks and keeps the cell alive
Dendrites – receive information from other neurons
Axon – transmits information to the other neurons, muscles and glands

5. Glial cells – support cells found in the nervous system
Some digest parts of dead neurons
Some provide physical and nutritional support for neurons
Myelin sheaths – an insulating layer of fatty material around the axons of some neurons
Formed by some glial cells
Synapse: junction or region between the axon of one neuron and the dendrites or cell body of another

6. The synapse

7. Types of Neurons
Sensory neurons – receive information from the external world and convey it to the brain via the spinal cord
Motor neurons – carry signals from the spinal cord to the muscles to produce movement
Interneurons – connect sensory neurons, motor neurons and other interneurons
Most common

8. Communicating information within a neuron
Communication happens in two stages:
Conduction of an electric signal over relatively long distances within neurons
Transmission of electric signals between neurons over the synapse

9. Communication -cont-
Neuron’s cell membrane is porous and allows ions (small electrically charged molecules ) to flow in and out of the cell
When at rest, channels that allow small, positively charged potassium ions (K+) to pass are open
Channels that allow the flow of other molecules are normally closed
There are more potassium ions inside the neuron, so some K+ ions flow out leaving the neuron with fewer positively charged molecules on the inside relative to the outside
Resting potential – difference in electric charge between the inside and outside of a neuron’s cell membrane

10. Communication -cont-
Action potential – electric signal that is conducted along the length of a neuron’s axon to the synapse
Occurs only when an electric shock reaches a certain level, or threshold
When an electric charge is raised to the threshold value, the K+ channels briefly shut down and other channels that allow the flow of sodium (Na+), another positively charged ion, are opened
When an electric current passes down the length of a myelinated axon, the charge “jumps” from node to node instead of travelling down the entire axon

11. Refractory period – time following an action potential during which a new action potential can’t be initiated
After action potential reaches it’s maximum, K+ flows out until the axon returns to resting potential
Eventually an active chemical “pump” in the cell membrane moves Na+ back outside the axon and K+ inside

12. Action Potential

13. The Action Potential

14. Synaptic transmission between neurons
Terminal buttons – knoblike structures that branch out from most axons
When the action potential reaches the terminal button, it stimulates the release of neurotransmitters – chemicals that transmit information across the synapse to a receiving neuron’s dendrites
Neurotransmitters float across the synapse and bind to sites on the dendrites of the receiving neuron called receptors – parts of the cell membrane that receive the neurotransmitter and initiate a new electric signal
Activation of receptors on the receiving neuron can cause a new electric potential to be initiated, called synaptic transmission

15. Neurotransmitters left in the synapse are cleared up through one of three processes:
Reuptake – neurotransmitters are reabsorbed by the terminal buttons of the presynaptic neuron’s axon
Enzyme deactivation – specific enzymes break down and destroy specific neurotransmitters
Autoreceptors – detect how much of a neurotransmitter has been released into a synapse and signal the neuron to stop releasing the neurotransmitter when too much is present

16. Synaptic Transmission

17. Types of Neurotransmitters

18. How Drugs Mimic Neurotransmitters
Agonists – drugs that increase the action of a neurotransmitter
Prozac blocks reuptake of serotonin

19. Antagonists – drugs that block the function of a neurotransmitter

20. The Organization of the Nervous System

21. Made up of two divisions:
Nervous system – interactive network of neurons that conveys electrochemical information throughout the body
Made up of two divisions:
Central nervous system (CNS) – brain and the spinal cord
Peripheral nervous system (PNS) – connects the CNS to the body’s organs and muscles
Also composed of two parts:

22. Somatic nervous system – set of nerves that conveys information into and out of the CNS
Autonomic nervous system (ANS) – set of nerves that carries involuntary and automatic commands that control blood vessels, body organs and glands
Sympathetic nervous system – set of nerves that prepares the body for action in threatening situations
Parasympathetic nervous system – helps the body return to a normal resting state

23. The Human Nervous System

24. Sympathetic and parasympathetic systems

25. Components of the CNS: The Spinal Cord
Some behaviors do not require input from the brain to the spinal cord
Spinal reflexes – simple pathways in the nervous system that quickly generate muscle contractions

26. Components of the CNS: The Brain

27. The Hindbrain
Hindbrain – area of the brain that coordinates information coming into and out of the spinal cord
Sometimes called the brain stem – includes:
Medulla – extension of the spinal cord into the skull that coordinates heart rate, circulation and respiration
Reticular formation – brain structure that regulates sleep, wakefulness and levels of arousal
Cerebellum – large structure that controls fine motor skills
Thalamus – directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla
Pons – relays information from the cerebellum to the rest of the brain

28. The Hindbrain

29. The MIdbrain

30. The forebrain Highest level of the brain
Controls complex cognitive, emotional, sensory and motor functions
Divided into two main parts:
Cerebral cortex – outermost layer of the brain
Subcortical structures – areas of the forebrain housed under the cerebral cortex near the center of the brain

31. Subcortical structures
Limbic system – located below the cerebral hemispheres
Associated with emotions and drives
Amygdala – involved in many emotional processes, particularly the formation of emotional memories
Hippocampus – plays a role in the storage of memories

32. Subcortical structures -cont-
Thalamus – sits on top of the brain stem and serves as a relay station
Like a server in a computer network
Hypothalamus – regulates body temperature, hunger, thirst and sexual behavior
Basal ganglia – large neuron clusters that work with the cerebellum and cerebral cortex to control and coordinate voluntary movements

34. The forebrain

35. The cerebral cortex Divided into two hemispheres
Each controls the opposite side of the body
Corpus callosum – thick band of nerve fibers that connects large areas of the cerebral cortex on each side of the brain and supports communication of information across the hemispheres
Hemispheres are subdivided into four areas/lobes
Occipital lobe – processes visual information
Parietal lobe – processes information about touch
Temporal lobe – hearing and language
Frontal lobe – has specialized areas for movement, abstract thinking, planning, memory and judgment

37. Motor cortex – area at the back of the frontal lobe that controls voluntary movements
Sensory cortex – area at the front of the parietal lobes that registers and processes body touch and movement sensations
Association areas – areas of the cerebral cortex that are composed of neurons that help provide sense and meaning to information registered in the cortex
Are usually less specialized and more flexible than neurons in the primary areas

38. The brain and language
Aphasia – impairment of language, usually caused by left hemisphere damage either to Broca’s area or to Wernicke’s area
Broca’s area – controls language and expression
Usually in the left frontal lobe
Directs muscle movements involved in speech
Wernicke’s area – controls language reception
Usually in left temporal lobe

39. Plasticity – the brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience

40. Our divided brain
Split brain – results from surgery that isolates the brain’s two hemispheres by cutting the fibers connecting them
Left visual field
Right half of each eye
Right hemisphere
Right visual field
Left half of each eye
Left hemisphere

41. Some things to remember about the brain’s hemispheres:
There is no activity to which only one hemisphere makes a contribution
Logic is not confined to the left hemisphere and creativity and intuition are not exclusive properties of the right hempishere
It is impossible to educate one hemisphere at a time
There is no evidence that people are purely “left-brained” or “right-brained”

42. How we study the brain
Brain lesioning – abnormal disruption in the tissue of the brain resulting from injury or disease
Is done with laboratory animals to determine the function of different parts of the brain
Strokes and brain injuries create lesioned areas in the brain

43. Electrical activity within the brain is measured with an electroencephalogram (EEG)
Multiple electrodes are attached to the outside of the head
Advantages:
Can detect very rapid changes in electrical activity, allowing analysis of stages of cognitive activity
Disadvantages:
Provides poor spatial reasoning of the source (cells, brain region) of electrical activity

44. Neuroimaging techniques
PET (positron mission tomography) scan – indicates specific changes in neuronal activity by detecting where a radioactive form of glucose goes while the brain performs a given task
Advantage – provides visual image corresponding to anatomy
Disadvantages:
Requires exposure to low levels of radioactivity
Not as clear as an MRI
Cannot follow changes faster than 30 seconds

45. CT (computed tomography) scan – series of X-rays taken from different angles and combined by computer into a composite representation of a slice through the body
MRI (magnetic resonance imaging) – show brain anatomy
fMRI (functional MRI) – can reveal brain’s functioning and structure

46. fMRI scan of a concussion

47. Genetics, evolutionary psychology and behavior

48. Behavior genetics
Chromosome – strands of DNA wound around each other in a double-helix configuration
DNA – complex molecule containing the genetic information that makes up the chromosomes
Genes – biochemical units of heredity that make up the chromosomes

49. Twin and adoption studies
Identical twins – develop from a single fertilized egg that splits in two
Also called monozygotic twins
Share 100% of their genes
Fraternal twins – develop from separate fertilized eggs
Also called dizygotic twins
Share about 50% of their genes
Likelihood increases with use of fertility treatments and genes