Neuroscience and Behavior

1. Neuroscience and Behavior

2. Objectives • Gain a general understanding of the nervous system • Gain knowledge of the structure and function of the neuron • Navigate your way around the major brain areas and understand their function

3. Nervous System Hierarchy

4. Central nervous system • Brain • ~2% of body weight, uses ~20% of resources • Composed of bunches of neurons, which form nerves • Spinal cord • Complex tangle of nerves that stretch from brain to tailbone • Collects & transmits info between brain and peripheral nervous system • Also initiates reflexes: automatic responses to an event

5. Peripheral Nervous System • PNS links the CNS to the organs, muscles, and glands of the body • PNS has two parts • Somatic (SNS): nerves controlling voluntary muscle movements • Autonomic (ANS): controls glands, organs, blood vessels • ANS has two parts • Sympathetic: arouses body to prepare for action (fight or flight) • Parasympathetic: slows down body to reserve energy

6. Sympathetic and Parasympathetic

7. The Neuron • All brain activity originates with the neuron • The messengers of the brain-world • These cells receive signals from neurons or sense organs, process the signals, and send them to other neurons, muscles, or organs • Three types • Sensory: respond to sensory organ input • Motor: send signals to muscles to control movement • Interneurons: the go-between of sensory and motor neurons • We have about 100 billion neurons • Most, but not all, can be re-grown (severe spinal cord injury vs. cutting your finger)

8. The Neuron

9. The Neuron: Structure • Cell body: houses nucleus • Cell Membrane: skin of the cell • Axon: cable extending from the cell body • Impulse from cell body travels along axon to its end, where terminal buttons release neurotransmitters (chemical messengers), received by other neurons • Axon is covered by myelin sheath, which is composed of a fatty substance that helps impulses travel the length of the axon • Dendrite • Branches extending from cell membrane that receive neurotransmitters from other neurons

10. The Dendrite • Increases receptive surface of the neuron • Contacts occur along surface of dendrite

11. The Axon • Axon hillock • Myelin sheath • Nodes of Ranvier • The points just between the myelin sheaths

12. The Neuron in Action • When a neuron receives impulses from other neurons, the cell membrane allows open exchange of positively and negatively charged ions • Action potential (change in electrical charge) runs down axon to terminal buttons • This all starts with the axon hillock – the gatekeeper of the neuron • Terminal buttons release neurotransmitters • Neurotransmitters cross the synaptic cleft to the dendrite of the receiving neuron

13. The Neuron in action

14. Communication in the Neuron • All-or-nothing • The action potential either happens or it doesn’t • Non-decremental • Action potentials don’t change in amount (voltage) as they travel • Refractory period • Neurons need 2ms to recover before they can transmit again • Threshold • The minimum level of stimulation required to trigger a neural impulse • Once you reach the threshold, the action potential doesn’t get bigger

15. Several Neurotransmitters • Acetylcholine (Ach) • Slows down the body, memory, and attention (involved in Alzheimer’s disease) • Dopamine (DA) • Voluntary movement, attention, and learning; high levels are associated w/ schizophrenia • Endorphin • Reduce sensitivity to pain; linked with pleasure (opiate-like) • Serotonin • Arousal, sleep; Prozac increases levels of serotonin • Norepinephrine • Helps control alertness and arousal; low levels can depress mood

16. History of Studying the Brain • Franz Joseph Gall (1758 – 1828) • Phrenology • The study of the structure of the skull to determine a person’s character and mental capacity • 26 ‘organs’ on the surface of the brain

17. History of Studying the Brain Phrenological Map of the Skull

18. History of Studying the Brain • Flourens (1794 – 1867) • Emphasized the importance of experimental research of the brain • Carefully controlled experiments on animals to determine localities of brain and their functions • Moved the field of brain research into a more scientific arena

19. The Brain • Three main parts • Brain Stem • Limbic System • Cerebral Cortex

20. Areas of the Brain

21. Brain Stem • Region of the brain where the spinal cord enters the skull and swells • Medulla • Regulates heart-rate, breathing, blood pressure, and motor movements • Cerebellum • Controls skilled motor movements

22. Brain Stem • Pons • Connects the two hemispheres of the cerebellum • Reticular formation • Sleep (Moruzzi & Magoun, 1961) • Attention • Thalamus • Relay center • Filters & organizes information from senses

23. Limbic System • Hypothalamus • Feeding • Reproductive behavior • Temperature (Barbour, 1912) • Hippocampus • Memory • H.M. • Amygdala • Feeding • Memory • Emotion

24. Cerebral Cortex • Two halves, four lobes • Frontal lobe • Motor cortex • Parietal lobe • Sensory cortex • Prosopagnosia • Unilateral neglect • Temporal lobe • Auditory areas • Occipital lobe • Visual areas

25. Two Cerebral Hemispheres • Contralateral arrangement • Corpus callosum • Thick band of nerve fibers connecting the hemispheres • It’s how the 2 hemispheres communicate • Right-brained vs. left-brained? OR

26. Left & Right Functions