2. The Human Nervous System 35-1 Name the three parts of a neuron. Describe the way in which a nerve impulse occurs.

4. Can you label a neuron? Cell body Nucleus Dendrites Axon Node of Ranvier Nucleus - Schwann cell Schwann cell Myelin sheath Synaptic knob Terminal Branches

5. A faster impulse – the action potential jumps from gap to gap. Myelin Sheath

6. Nerve Impulse First a cell sets up the resting potential negative inside and positive outside ATP used to drive sodium/potassium pump Potassium can move freely Sodium must be pumped Potassium diffuses back out.

8. Three types of Nerve Cells Sensory Neurons Inter Neurons Motor Neurons

11. In a synapse vesicles release neurotransmitters which cause the next neuron to fire.

13. The Impulse An Action potential stimulates the membrane. Permeability to Na+ suddenly increases as sodium gates open Na+ rushes in and the polarity reverses Impulse flows in one direction due to refractory period. Called all-or-none response.

14. The Nerve System

15. N E R V E S

16. Fun Facts ! Average number of neurons in the human brain= 100 billion Average number of neurons in an octopus brain= 300 billion Rate of neuron growth during development of a fetus (in the womb)= 250,000 neurons/minute Diameter of a neuron= 4 to 100 microns Longest axon of a neuron= around 15 feet (Giraffe primary afferent axon from toe to neck) Velocity of a signal transmitted through a neuron= 1.2 to 250 miles/hour (remember that these are averages because there is lots of variability in the nervous system!!) Guess what? There are more nerve cells in the human brain than there are stars in the Milky Way.

17. Fun Facts ! (continued) What if we lined up all the neurons in our body? How long would that line stretch? Well, let's think about this... Let's assume that one neuron is about 10 microns long. Remember, this is just an example, because neurons come in all different sizes. So, if we line up 100 billion neurons which are 10 microns long... 100,000,000,000 neurons x 10 microns= 1000 km or about 600 miles! This may help with the math: 1000 microns= 1milimeter (mm) 10 mm= 1centimeter (cm) 100 cm= 1 meter (m) 1000 m= 1 kilometer (km)

18. Art and text and presentation made by: Valerie Shiba and Jennifer Li Hiya Mr. Nelson =P

19. Xerox 35-1 1 e 2 i 3 d 4 n 5 g 6 l 7 j 8 a 9 j 10 m 11 b 12 a 13 h 14 k,b 15 c 16 k 17 m 18 f 19 l

20. Xerox 35-1 (Cont.) 20 dendrite 21 b 22 c 23 d 24 sensory 25 negative 26 toward 27 node 28 neurotransmitter 29 travel to the next neuron 30 the impulse would not work 31 increase the speed of the neuron

22. Credits Initial art, text and presentation made by Valerie Shiba and Jennifer LiInitial art, text and presentation made by Valerie Shiba and Jennifer Li