Neural Communication

1. Neural Communication • Biological Psychology • branch of psychology concerned with the links between biology and behavior • some biological psychologists call themselves behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, orbiopsychologists • Phrenology (Franz Gall) • Study of the bumps on your head • Bumps reveal a person’s abilities and traits

2. Phrenology Popular in the 1800s, debunked after knowledge of neural communication grew in the 1900s.

3. Neurons and Synapses Types of Neurons Sensory Motor Interneurons

4. Neural Communication

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

7. 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

8. The cell body • Contains the cell’s Nucleus • Round, centrally located structure • Contains DNA • Controls protein manufacturing • Directs metabolism • No role in neural signaling

9. Myelin Sheath 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.

10. Axon • The cell’s output structure • One axon per cell, 2 distinct parts • tubelike structure branches at end that connect to dendrites of other cells

11. Neural Communication • Action Potential • a neural impulse; a brief electrical charge that travels down an axon • generated by the movement of positively charged atoms in and out of channels in the axon’s membrane • Threshold • the level of stimulation required to trigger a neural impulse

12. Cell body end of axon Direction of neural impulse: toward axon terminals Neural Communication

14. 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

15. Resting Potential • At rest, the inside of the cell is at -70 microvolts • With inputs to dendrites 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

16. Depolarization Ahead of AP • AP opens cell membrane to allow sodium (Na+) in • Inside of cell rapidly becomes more positive than outside • This depolarization travels down the axon as leading edge of the AP

17. Repolarization follows • After depolarization potassium (K+) moves out restoring the inside to a negative voltage • This is called repolarization • The rapid depolarization and repolarization produce a pattern called a spike discharge

18. Finally, Hyperpolarization • Repolarization leads to a voltage below the resting potential, called hyperpolarization • Now neuron cannot produce a new action potential • This is the refractory period

19. REFRACTORY PERIOD

20. Ion concentrations Outside of Cell K+ Na+ Cl- Cell Membrane in resting state K+ Na+ Cl- A- Inside of Cell

21. K+ Na+ Cl- Outside of Cell Cell Membrane at rest Na+ - 70 mv A- K+ Cl- Inside of Cell Potassium (K+) can pass through to equalize its concentration Sodium and Chlorine cannot pass through Result - inside is negative relative to outside The Cell Membrane is Semi-Permeable

22. Action potential

23. Neural Communication • Synapse [SIN-aps] • junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron • tiny gap at this junction is called the synaptic gap or cleft • Neurotransmitters • chemical messengers that traverse the synaptic gaps between neurons • when released by the sending neuron, neuro-transmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse

24. 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

25. Dopamine Pathways Neural Communication Serotonin Pathways

26. Excitatory and Inhibitory Messagesof neurotransmitters • Excitatory message— increases the likelihood that the postsynaptic neuron will activate • Inhibitory message— decreases the likelihood that the postsynaptic neuron will activate.

27. Neurons and Synapses Types of Neurons Sensory Motor Interneurons

28. Sensory Neurons • INPUT Fromsensory organs to the brain and spinal cord Brain Drawing shows a somatic neuron Also called AFFERENT NEURONS Sensory Neuron Spinal Cord

29. Brain Sensory Neuron Spinal Cord Motor Neuron Motor Neurons • OUTPUTFrom the brain and spinal cord, to the muscles and glands Also called EFFERENT NEURONS

30. Brain Sensory Neuron Spinal Cord Motor Neuron Interneurons • Interneuronscarry information between other neurons only found in the brain and spinal cord

31. Nervous system Peripheral Central (brain and spinal cord) Autonomic (controls self-regulated action of internal organs and glands) Skeletal (controls voluntary movements of skeletal muscles) Sympathetic (arousing) Parasympathetic (calming) The Nervous System