DRILL – Excretion Review. Label the nephron. Describe what happens in each part.

1. DRILL – Excretion Review. Label the nephron. Describe what happens in each part.

2. Ch 49 Nervous System

3. Why do animals need a nervous system? • What characteristics do animals need in a nervous system? • fast • accurate • reset quickly Remember…think aboutthe bunny… Poor bunny!

4. Ch 49 Nervous System • Structure of a Neuron

5. How do nerves send messages?

6. Nervous system cells • Neuron • a nerve cell signal direction dendrites • Structure fits function • many entry points for signal • one path out • transmits signal cellbody axon signal direction synaptic terminal myelin sheath dendrite  cell body  axon synapse

7. Fun facts about neurons • Most specialized cell in animals • Longest cell • blue whale neuron • 10-30 meters • giraffe axon • 5 meters • human neuron • 1-2 meters Nervous system allows for 1 millisecond response time

8. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + – – – – – – – – – – – – – – – – – – – – – – – – – – – – Cells have a resting membrane potential! • Membrane is polarized • More + ions outside relative to inside • Resting membrane potential is approx -70mV

9. + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – Na+ How does a nerve impulse travel? • Stimulus: nerve is stimulated EX by touch • reaches threshold potential • open Na+ channels and Na+ ions diffuse into cell • charges reverse at that point on neuron • positive inside; negative outside • cell becomes depolarized

10. Gate + + – + channel closed channel open + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – + + – – Na+ wave  How does a nerve impulse travel? • Wave: nerve impulse travels down neuron • change in charge opens next Na+ gate down the line • “voltage-gated” channels • Na+ ions continue to diffuse into cell • “wave” moves down neuron = action potential The restof thedominoes fall!

11. How does the nerve re-set itself? • Sodium-Potassium pump • active transport protein in membrane • requires ATP • 3 Na+ pumped out • 2 K+ pumped in • re-sets chargeacross membrane ATP That’s a lot of ATP ! Feed me somesugar quick!

12. Myelin sheath • Axon coated with Schwann cells • insulates axon • speeds signal • signal hops from node to node • saltatory conduction • 150 m/sec vs. 5 m/sec(330 mph vs. 11 mph)

13. What happens at the end of the axon? Synapse Impulse has to jump the synapse! • junction between neurons • has to jump quickly from one cell to next

14. Chemical synapse • Events at synapse • action potential • opens Ca++ channels • neurotransmitter vesicles fuse with membrane • release neurotransmitter to synapse • Neurotransmitter opens a “chemically gated” Na channel – starts Act Pot. • neurotransmitter degraded or reabsorbed axon terminal action potential synaptic vesicles synapse Ca++ neurotransmitteracetylcholine (ACh) receptor protein muscle cell (fiber)

15. Neurotransmitters • Acetylcholine • transmit signal to skeletal muscle • Epinephrine (adrenaline) & norepinephrine • fight-or-flight response • Dopamine • Serotonin • Adenosine

16. 49.4 Drugs and the Nervous System • Psychoactive drugs – affect Nerv Sys • Dependence – physical/emotional need • Addiction – no control over use • Withdrawal – physical response to absence • Tolerance – physical change such that more drug is req’d to get same effect.

18. Neurotransmitters • Weak point of nervous system • any substance that affects neurotransmitters or mimics them affects nerve function • gases: nitrous oxide, carbon monoxide • mood altering drugs: • stimulants • amphetamines, caffeine, nicotine • depressants • Barbiturates, alcohol • hallucinogenic drugs: LSD • SSRIs: Prozac, Zoloft, Paxil

19. Acetylcholinesterase • Enzyme which breaks downacetylcholine neurotransmitter • acetylcholinesterase inhibitors = neurotoxins • snake venom, sarin, insecticides neurotoxin in green active site in red snake toxin blockingacetylcholinesterase active site acetylcholinesterase

20. Questions to ponder… • Why are axons so long? • Why have synapses at all? • How do “mind altering drugs” work? • caffeine, alcohol, nicotine, marijuana… • Do plants have a nervous system? • Do they need one?

21. Ponder this…Any Questions??

22. 49.2 Structure of the Nervous System • Central Nervous System - Brain and Spine • Peripheral Nervous System - All other nerves and nerve endings

23. Brain Structure and Function

24. Brain regions

25. Peripheral System Divisions • Sensory – deals with all incoming info • Motor – muscle control • Two Motor Divisions • Somatic – skeletal muscle conscious and reflexes. • Autonomic – deals with smooth muscle *Sympathetic – fight or flight/stress * Parasympathetic – normal/non freak out

26. Spinal Reflex – EX Knee Jerk

27. HW Due Thurs 4/24 • Ch 49 GRQ;s • Test Chap 47&48. • (turn in any prior GRQ’s/SR’s EX. Ch47, Ch 48)

28. HW Due Mon 4/28 • Ch 49 SR 1 – Q 2-5,7 • Ch 49 SR 2 – Q1-5 • Ch 49 SR 4- Pick a psychoactive drug and google ”Mechanism of action” –find out how it affects the Nervous system. Cite Sources