The Biological Basis of Behavior

1. The Biological Basisof Behavior The Nervous System and Neural Transmission

2. Functions of the Nervous System (NS) 1. The NS governs voluntary behaviors (walking, talking) and thought processes. 2. The NS controls involuntary functions needed for survival (breathing, cardiac activity).

3. Branches of the Nervous System

4. CNS • The CNS is the body’s executive control center. • It consists of the brain and spinal cord.

5. Peripheral Nervous System • Anything not encased in bone • Two branches: somatic and autonomic NSs • Somatic NS controls voluntary actions • Autonomic NS governs organ and gland function

6. Symptoms of the Sympathetic NS: “Fight” or “Flight” response • HR increases • Breathing increases • Sweating increases • Pupils dilate • Dry mouth

7. Symptoms of the Parasympathetic NS • HR decreases • Breathing decreases • Sweating decreases • Pupils constrict • Saliva is normal

8. Neurons: What are they? • The cells of the NS. • We have over 100 billion of these!!!

9. Types of Neurons • Sensory neurons -receive information from environment. • Motor neurons – send signals to muscles and glands to ready organism for action. • Interneurons – receive & send information to other neurons.

10. Neuron Shapes

11. Parts of the Neuron cell • 1. Cell body – control center for cell; contains nucleus. • 2. Dendrites – “tree-like” branches that receive signals from other cells. • 3. Axon – long branching arm where impulses travel down cell.

12. Motor Neuron

13. Neural transmission • Communication “within” cells is “electrical.” • Communication “between” cells is “chemical.”

14. Resting neurons A neuron at rest is more negatively charged inside the cell than outside the cell. The difference in voltage between the inside and outside of the cell is called its resting potential.

15. Forces to keep a cell at rest • 1. Concentration gradient • 2. Electrical gradient • 3. Selective permeability • 4. Sodium-Potassium pump

17. Summary • 1. Na+, K+, & Cl- are unequally distributed across the cell. • 2. Na+ is driven to enter cell due to cell’s internal negative charge & heavy concentration outside cell. • 3. K+ is driven to leave cell due to heavy concentration inside the cell. • 4. Na+ kept out through resistance of membrane & pump. K+ kept in due to pump.

18. Action potentials The cell fires, or sends an impulse down its axon. Operates according to the “all-or-none” rule.

20. Summary: Action potentials • 1. Na+ ions rush into cell driving charge up from –70mV to +50 mV. • 2. K+ ions leave cell due to their heavy concentration inside the cell and the cell’s new + charge. Cl- ions enter cell drawn by cell’s + charge. • 3. Na+ influx ceases, while K+ exflux continues. Cell’s charge is now –72 mV (hyperpolarized).

21. Synaptic transmission • Neurons communicate with one another by releasing chemicals called neurotransmitters. • Neurotransmitters: dopamine, acetylcholine, serotonin, & norepineprhine

22. Otto Leowi’s work (1920)

23. Sequence of events in synaptic transmission • 1. Cell synthesizes neurotransmitters (NTs). • 2. NTs transported down axon to end buttons. • 3. NTs released from terminals. • 4. NTs attach to receptors of postsynaptic cell. • 5. NTs broken down and reabsorbed by presynaptic neuron.

25. Synaptic transmission • When cell’s fire, Ca++ channels open in the end terminal, release Ca++ ions. • Ca++ ions cause release of NTs at synaptic cleft. • This is why you should drink milk!!!!