1. Neuroscience and Behavior
Chapter 2
Neuroscience and Behavior

2. Neurons and Synapses Types of Neurons Sensory Motor Interneurons
Key words: Types of neurons; sensory neurons; motor neurons; interneurons; afferent nerves; efferent nerves

3. Sensory Neurons INPUT From sensory organs to the brain and spinal cord
Drawing shows a somatic neuron
Sensory
Neuron
Spinal
Cord
Key words: sensory neurons; afferent nerves; types of neurons
Graphic from Hockenbury slides

4. Motor Neurons
OUTPUT From the brain and spinal cord to the muscles and glands
Spinal
Cord
Brain
Sensory
Neuron
Motor
Key words: Motor neurons; efferent nerves; types of neurons
Graphic from Hockenbury slides

5. Interneurons
Interneurons carry information between other neurons only found in the brain and spinal cord
Spinal
Cord
Brain
Sensory
Neuron
Motor
Key words: interneurons; types of neurons
Graphic from Hockenbury slides

6. Parts of a Neuron Key words: Neuron; structures of neurons
Graphic From Image and lecture gallery

7. The Cell Body Contains the cell’s nucleus
round, centrally located structure
contains DNA
controls protein manufacturing
directs metabolism
no role in neural signaling
Graphic from Hockenbury slides
Key words: Cell body; soma; cell nucleus
Interesting facts:
The DNA in the nucleus of the cell has lost its ability to divide. therefore, when a neuron dies,for the most part, the adult brain cannot simply grow new neurons. (Note there are a few exceptions to this rule.)
The relative inability to grow new neurons leads to two interesting questions:
Q1: How do brain tumors (cancer) occur?
A: Unlike neurons, glial cells can divide and grow new cells throughout one's lifetime. Most brain tumors are limited to glial cells, not neurons.
Q2: If a person cannot grow new neurons, how does the brain change in order to accommodate new learning?
A: One mechanism by which the brain adapts to help you learn new information involves the structure on the next slide: the dendrites.

8. Dendrites Information collectors
Receive inputs from neighboring neurons
Inputs may number in thousands
If enough inputs, the cell’s AXON may generate an output

9. Dendritic Growth Mature neurons generally can’t divide
But new dendrites can grow
Provides room for more connections to other neurons
New connections are basis for learning

10. Axon The cell’s output structure One axon per cell, 2 distinct parts
tube-like structure
branches at end that connect to dendrites of other cells
Hockenbury slides (Schulman)
Key words: axon; action potentials
Interesting facts:
- The diameter of an axon may vary from approximately 1mm-20mm.
- An axon may travel long distances to reach it's destination (longest axon is approximately 3 feet in humans and 10 feet in giraffes).

11. Myelin Sheath White fatty casing on axon
Acts as an electrical insulator
Not present on all cells
When present, increases the speed of neural signals down the axon
Graphic from Hockenbury slides
Key words: myelin sheath; action potentials; axon
Interesting facts:
- The myelin sheath is NOT a part of the axon. The myelin sheath is actually formed of glial cells (oligodendricytes and Schwann cells) that wrap around the axon.
- You may have often heard the brain referred to as either white matter or gray matter. The myelin sheath appears white in nature. Hence, the term white matter refers to areas of the brain that are myelinated. Gray matter refers to areas of the brain that are unmyelinated.
- When you accidentally cut yourself, you often visually notice that you've cut yourself before you actually feel any pain from the cut. The reason for this is that visual information uses myelinated axons; whereas, pain information uses unmyelinated axons.
- The loss of myelin is a significant factor in the disease multiple sclerosis (MS). When myelin is lost, the high-speed transmission of information is slowed down or blocked completely, which could lead the person with the inability to walk, write or speak.

12. How Neurons Communicate
Neurons communicate by means of an electrical signal called the action potential.
Action potentials are based on movements of ions between the outside and inside of the cell.
When an action potential occurs, a molecular message is sent to neighboring neurons.

13. Action Potential Within a Neuron

14. Resting Potential
Graphic, Hockenbury slides
At rest, the inside of the cell is at -70 microvolts.
With inputs to dendrites, the inside becomes more positive.
If resting potential rises above threshold, an action potential starts to travel from cell body down the axon.
Figure shows resting axon being approached by an AP.

15. Depolarization Ahead of AP
Graphic from Hockenbury slides
AP opens cell membrane to allow sodium (Na+) to enter.
Inside of cell rapidly becomes more positive than outside.
This depolarization travels down the axon as leading edge of the AP.

16. Repolarization follows
Graphic from Hockenbury slides
After depolarization, potassium (K+) moves out restoring the inside to a negative voltage.
This step is called repolarization.
The rapid depolarization and repolarization produce a pattern called a spike discharge.

17. Finally, Hyperpolarization
Graphic from Hockenbury slides
Repolarization leads to a voltage below the resting potential, called hyperpolarization.
Now, the neuron cannot produce a new action potential.
This is the refractory period.

18. Neuron to Neuron
Axons branch out and end near dendrites of neighboring cells.
Axon terminals are the tips of the axon’s branches.
A gap separates the axon terminals from dendrites.
The gap is called the synapse.
Key words: axon terminal
Graphic from Hockenbury slides .

20. Neurotransmitter Release
Action potential causes vesicle to open.
Neurotransmitter released into synapse.
Neurotransmitter locks onto receptor molecule in postsynaptic membrane.

21. Excitatory and Inhibitory Messages
Excitatory message — increases the likelihood that the postsynaptic neuron will activate
Inhibitory message — decreases the likelihood that the postsynaptic neuron will activate.

22. Locks and Keys Neurotransmitter molecules have specific shapes.
Receptor molecules have binding sites.
When NT binds to receptor, ions enter.
Graphic from Hockenbury slides

23. Some Drugs Work on Receptors
Some drugs are shaped like neurotransmitters.
Antagonists: fit the receptor but poorly and block the NT
e.g., beta blockers
Agonists: fit receptor well and act like the NT
e.g., nicotine
Graphic from Hockenbury slides

24. Types of Neurotransmitters
Acetylcholine
Dopamine
Serotonin
Norepinephrine
GABA
Endorphins

25. Found in neuromuscular junctions Involved in muscle movements
Acetylcholine (Ach)
Found in neuromuscular junctions
Involved in muscle movements
Involved in learning and memory
Graphic, Hockenbury slides

26. Disruption of Acetylcholine Functioning
Curare — blocks ACh receptors
paralysis results
Nerve gases and Black Widow spider venom — too much ACh leads to severe muscle spasms and possible death

27. Disruptions in ACh Functioning
Cigarettes — nicotine works on ACh receptors
can artificially stimulate skeletal muscles, leading to slight trembling movements

28. Alzheimer’s Disease
Deterioration of memory, reasoning, and language skills
Symptoms may be due to loss of ACh neurons

29. Dopamine
Involved in movement, attention, and learning
Dopamine imbalance also involved in schizophrenia
Loss of dopamine-producing neurons is cause of Parkinson’s disease

30. Parkinson’s Disease
Results from loss of dopamine-producing neurons in the substantia nigra
Symptoms include
difficulty starting and stopping voluntary movements
tremors at rest
stooped posture
rigidity
poor balance
key words: Basal ganglia; Parkinson's disease; dopamine

31. Parkinson’s Disease Treatments L-dopa
transplants of fetal dopamine-producing substantia nigra cells
adrenal gland transplants
electrical stimulation of the thalamus has been used to stop tremors
L-Dopa facts: The purpose of this drug is to increase the amount of dopamine in the system. L-dopa is a precursor to dopamine. It will eventually be converted into dopamine.
Question: Why not just give the patient dopamine?
Answer: Dopamine cannot cross the blood brain barrier. If you take a dopamine pill, you will see increased levels of doapmine in the body, but not in the brain. L-dopa can enter the brain.

32. Involved in depression
Serotonin
Involved in sleep
Involved in depression
Prozac works by keeping serotonin in the synapse longer, giving it more time to exert an effect

33. “Fight or flight” response
Norepinephrine
Arousal
“Fight or flight” response

34. Endorphins Control pain and pleasure Released in response to pain
Morphine and codeine work on endorphin receptors; involved in healing effects of acupuncture
Runner’s high— feeling of pleasure after a long run is due to heavy endorphin release

35. GABA Inhibition of brain activity
Huntington’s disease involves loss of neurons in striatum that utilize GABA
Symptoms:
jerky involuntary movements
mental deterioration

36. Summary Neuron structure Action potentials Synapse Neurotransmitters
Receptors and ions
Agonists and antagonists
Graphic from Hockenbury p.42 figure 2.2

37. Parts of the Nervous System
Central Nervous System (CNS)
Brain and spinal cord
Peripheral Nervous System (PNS)
Carries messages to and from CNS

38. Central nervous system
Bloom, Nelson, and Lazerson, Brain, Mind, and Behavior
Introduction to the Nervous System Figure 1.03
Peripheral nervous system

39. Discovering PSY p. 55 Figure 2.11

40. Sympathetic and parasympathetic divisions of the nervous system
Kolb & Whishaw, An Introduction to Brain and Behavior
How is the Brain Organized? Figure 2.29
Sympathetic and parasympathetic divisions of the nervous system

41. Endocrine System
Pituitary gland — attached to the base of the brain, hormones affect the function of other glands
Adrenal glands — hormones involved in human stress response
Gonads — hormones regulate sexual characteristics and reproductive processes; testes in males, ovaries in females.

42. Brain Images Brainstem Forebrain Hindbrain Midbrain Limbic system
Cortex
Discovering PSY p Figure 2.16

44. Developing Brain
Neural tube — beginning of nervous system develops at 2 weeks after conception
Neurogenesis — development of new neurons

45. Hindbrain Structures Cerebellum Brainstem medulla reticular formation
pons
Discovering psy p 63 fig 2.14

46. Cerebellum Coordinated, rapid voluntary movements
e.g., playing the piano, kicking, throwing, etc.
Lesions to cerebellum
jerky, exaggerated movements
difficulty walking
loss of balance
shaking hands
Hockenbury slides

47. Medulla Breathing Heart rate Digestion Other vital reflexes swallowing
coughing
vomiting
sneezing
Gray, 3e fig 5.6

48. Reticular Formation Network of neurons in the brainstem (and thalamus)
Sleep and arousal
Attention
Myers, Exploring psy 4e Figure 2.10

49. Pons Helps coordinate movements on left and right sides of the body
e.g., postural reflexes which help you maintain balance while standing or moving
Gray, 3e fig 5.6

50. Forebrain Structures Thalamus Limbic System Cortex
Bloom, Nelson, and Lazerson, Brain, Mind, and Behavior Introduction to the Nervous System
Figure 1.07r

51. Thalamus Relay station in brain
Processes most information to and from higher brain centers
Gray, 3e fig 5.6

52. The Limbic System Hypothalamus Amygdala Hippocampus
Discovering Psy p. 67 Fig 2.18

53. Hypothalamus Contains nuclei involved in a variety of behaviors
sexual behavior
hunger, thirst
sleep
water and salt balance
body temperature regulation
circadian rhythms
role in hormone secretion
The hypothalamus is made up different subregions or nuclei. These nuclei generally differ in terms of gross anatomy and function.
Sexual behavior: The medial preoptic and medial anterior hypothalamic nuclei of the hypothalamus are heavily involved in mating behaviors of animals. Damage to these areas results in a loss of mating behaviors. Electrical stimulation of these areas (or insertion of sex hormones in these areas) can elicit sexual behaviors.
Hunger: Lesions to the hypothalamus can lead to severe obesity or extreme weight loss, depending upon the region damaged.
Thirst: Electrical stimulation of the hypothalamus can cause an animal to start drinking even in animals that have plenty of water in their systems. Neurons in the supraoptic nucleus of the hyopthalamus are sensitive to changes in the osmolarity of blood. These neurons control the secretion of vasopression, which is more commonly known as "anti-diuretic hormone" or ADH. ADH acts in the kidney to increase fluid retention.
Sleep:
Temperature regulation: Your body tries to keep the same body temperature regardless of how hot or cold it is outside. The hypothalamus helps maintain a constant body temperature. Hypothalamus contains temperature-sensitive neurons. Neurons in the posterior hypothalamus become active when you are cold; whereas, heat activates the anterior hypothalamus. Changes in body temperature can cause the hypothalumus to initiate such behaviors as shivering, hunger, adrenaline secretion and fever to help you get back to the proper body temperature.
Circadian rhythms: the suprachiasmatic nucleus (or SCN) of the hypothalamus is thought to be involved in regulating the body's natural 24 hour rhythms.

54. Hypothalamus and Hormones
Hypothalamus releases hormones or releasing factors which in turn cause pituitary gland to release its hormones
Gray, psychology 3e fig 5.27

55. Amygdala and Emotion Identify emotion from facial expressions
Amygdala damage makes this task difficult
From Hockenbury slides
(click on picture to advance photos)

56. Cortical Specialization
Localization — notion that different functions are located in different areas of the brain
Lateralization — notion that different functions are processed primarily on one side of the brain or the other

57. Lobes of the Cortex
Frontal lobe — largest lobe, produces voluntary muscle movements, involved in thinking, planning, emotional control
Temporal lobe — primary receiving area for auditory information
Occipital lobe — primary receiving area for visual information
Parietal lobe — processes somatic information

60. Language and the Brain
Aphasia — partial or complete inability to articulate ideas or understand language because of brain injury or damage
Broca’s area — plays role in speech production
Wernike’s area — plays role in plays role in understanding and meaningful speech

61. Discovering PSY 2e p74 table 2.2

62. Split brain operation—procedure used to reduces recurrent seizures of severe epilepsy
Corpus callosum—thick band of axons that connects the two cerebral hemispheres