1. Introduction to Vertebrate Nervous Systems
Chapter 48

2. Functions of NS Receiving information from environment
Integrating information received from environment
Motor output in response

3. Neuron Structure

4. Neurons have different shapes for different jobs

5. Vertebrate NS Structure
Central Nervous System: brain and spinal cord
Peripheral Nervous System: peripheral nerves

6. Nervous Conduction
All cells have a voltage potential across their membranes
Changes in this potential give rise to nervous signaling

7. Resting Potential Inside the neuron is more negative than the outside
Ion channels allow only some ions to cross the membrane

8. Action Potential
1. At rest, there is more K+ inside and more Na+ outside. Both ions’ channels are closed. Membrane potential: -70mV
2. A stimulus causes the threshold potential to be reached, so sodium channels open and sodium ions flow in and cause more Na+ channels to open. MP: -50mV

9. Action Potential
3. During depolarization, the Na+ channels are open, but the K+ channels are closed. Cell interior becomes more positive due to Na+ ion influx. MP: +35mV
4. During repolarization, Na+ channels close and K+ channels open, causing K+ to exit. The inside of the cell is more negative than the outside. MP: <+35mV

10. Depolarization and Repolarization: what it looks like

11. Action Potential
5. As the membrane potential heads back toward resting, the K+ channels have not had a chance to close. The membrane is hyperpolarized and membrane potential dips slightly below -70mV: undershoot
6. Eventually, ion concentrations return to normal and resting potential is restored. MP: -70mV

13. Membrane Potential

14. Principles of Neural Firing
When a nerve fires, it does not fire “halfway” when stimulated
It will fire completely once a stimulus is received and threshold potential is reached: “all or nothing” principle
No threshold, no action potential

15. Saltatory Conduction
Axons are myelinated--increases nervous signal conduction speed by making signal jump between Schwann cells.

16. Chemical Communication
Occurs at synapses: gaps between neurons
Uses neurotransmitters: substances released from vesicles when action potential reaches end of pre-synaptic axon

17. Synaptic transmission
1. An AP depolarizes the synaptic terminal membrane and Ca+2 ions rush in.
2. Synaptic vesicles with neurotransmitter fuse with presynaptic membrane.
3. Vesicles fuse with membrane, releasing neurotransmitter into cleft.

18. Synaptic transmission
4. Neurotransmitter binds to receptors on post-synaptic membrane, which gets depolarized.
5. Neurotransmitter is degraded by enzymes or taken up by another neuron. This prevents the synaptic response from persisting.

19. Synaptic transmission

20. Divisions of the NS Somatic NS Autonomic NS
Controls the voluntary actions an organism does
Example: voluntary muscle movements
Autonomic NS
Controls involuntary actions in an organism
Example: control of heartbeat, breathing, GI tract

21. Divisions of the autonomic NS
Sympathetic NS
Activation is correlated to arousal and energy generation
Examples: heart beat increases, liver converts glycogen glucose
Parasympathetic NS
Activation is correlated to calming actions
Opposite actions of SNS

23. Brain structures Cerebrum: conscious thought
Cerebellum: motor coordination
Medulla oblongata: involuntary functions
Meninges: tough protective membranes

24. Brain structures Corpus callosum: connects left and right hemispheres
Thalamus: relay center for messages
Hypothalamus: controls 4F’s: feeding, fleeing, fighting, flirting

25. Regions of the Brain
Frontal Lobe: personality, control of voluntary muscle movements, thoughts words

26. Regions of the Brain
Parietal Lobe: interpretation of textures, understanding symbols, verbal articulation of thoughts words

27. Regions of the Brain
Occiptal Lobe: organizes sight, conscious seeing

28. Regions of the Brain
Temporal Lobe: speech, olfaction, interpretation of auditory sensations, emotional behavior