Control Systems (PB Lecture 17 – Spring 2008 Althoff Ch. 34)

1. Control Systems (PB Lecture 17 – Spring 2008 Althoff Ch. 34) •Nervous system

2. Systems of Control:ENDOCRINE & NERVOUS • BOTH “SYNTHESIZE” MESSENGER CHEMICALS THAT ARE RELEASED INTO EXTRACELLULAR SPACES HormonesNerve cells Distance to impact Approach Target Duration of impact

3. Functions • Messenger (receive stimuli) • Communicator (process stimuli) • The critical “network” for maintaining homeostasis…for advanced animals, this means they are “wired” for quick response

4. Nervous System: CNS = _____________________ (central nervous system) vs. PNS = all nerves & ganglia ________ the CNS (peripheral nervous system)

5. ______ ______

6. Brain & spinal cord __________ sensory input, __________ response Nerves: carries sensory info to CNS and motor commands from CNS ______ to muscles & glands CNS PNS

7. Nerves Bundles of nerve fibers outside the CNS, most notably the axon and dendrite(s) portion of neurons.

8. Cell Types • ___________--conducts nerve impulses • ___________--supports and services neurons. Supplies nutrients, provides protection, and gets rid of waste

9. Neuron Structure • CELL BODY • DENDRITE • AXON • AXON ENDINGS (= axon terminals) • MYELIN

12. Neuron Structure • CELL BODY --nucleus & most organelles • DENDRITE--receive incoming information (i.e., stimulus) • AXON--carry information away from cell body • AXON ENDING --makes contact with other neurons, muscles, glands • MYELIN--covering on some neurons

13. 3 Types of Neurons • __________ NEURON • __________ NEURON • _________________ (association neurons) • Not all neurons look alike • Not all neurons carry the same • type of information

14. Types of Neurons…con’t • Consider types relative to CNS • Collectively, they are the electronic communications network of the body…. …know these types as well as their relationship to one another!

15. SENSORY NEURON • Carry ________ info from periphery to CNS (i.e., PNS  CNS) • Both dendrite and axon are myelinated • ____________ is in the PNS • Examples: pain, pressure, touch, hot, cold, light, sound, blood pressure, blood CO2, bladder stretch, etc.

16. MOTOR NEURON • Carry ___________________ from CNS to muscles or glands (i.e., CNS  PNS) • Skeletal muscles - causes contraction Smooth muscles - “ “ Adrenal gland - secrete hormone • Cell body is in the CNS, therefore, axon is usually ______

17. INTERNEURONS (association neurons) • Found _____ inside the CNS • Connects ___________ (sensory to motor and vise versa) • Typically short dendrites and either long or short axons

18. Hand moves PNS CNS PNS

19. Nerve Impulse A small ___________________ that occurs across the plasma membrane of neurons and then conducted along the axon/dendrite of the neuron

20. RESTING POTENTIAL NEURON AT REST

21. RESTING POTENTIAL OUTSIDE +40mV -65mV INSIDE _________________ ____________________ NEURON AT REST

22. RESTING to__________________ Na+ in K+ out During ACTION POTENTIAL, _____ channels open first, Na+ rushes in resulting in depolarization…then _____ channels open, K+ rushes out.

23. Summary RESTING POTENTAIL • Maintained at about -65mV by sodium-potassium pump (i.e., Na-K pump) • _____ always diffusing back and forth because of ___________________ • Na+ higher outside an axon, K + higher inside the axon resulting in the axon having a negative charge

24. ACTION POTENTIAL • A rapid change in polarity across the plasma membrane as the nerve impulse occurs • It is an “____________” phenomenon • If it causes depolarization to a certain level, it is called a ____________ and an “action potential” occurs

25. ACTION POTENTIAL…con’t • Strength of an action potential does ____ change… • …but an intense stimulus can cause the axon to fire at a ______________ • Requires two types of GATED CHANNELS: one for ____ and one for _____. The Na+ channel opens first

26. ACTION POTENTIAL…con’t • During this process, Na+ moves to the inside of the axon during the depolarization phase (-65mV  +40mV) • K + moves to the outside of the axon during the repolarization phase. (+40mV  -65mV) • Review Fig. 34.5, pages 651 in Johnson and Losos

28. Propagation of an Action Potential • As action potential travels down the axon, each successive portion of the axon undergoes depolarization, followed by repolarization • Like a _________________ • As the action potential moves on, previous portion goes through refractory period--Na+ channels are shut, then K + channels are shut

29. Propagation of an Action Potential…con’t • With refractory period (i.e., Na+ gate closed), the action potential _________________ ______________….just forwards • At “nodes”, the action potentials jump from node-to-node. At nodes, voltage-sensitive Na+ channel gates are numerous. Speeds of _____ meters/second (_____ miles/hour) have been recorded along a motor neuron

30. Synapse Structure & Function • Where “signal” is transmitted from ____ _____________________ • Axon bulb  synaptic cleft  postsynaptic neuron • ___________________--molecules that transmit the signal across the synaptic cleft

31. Synapse (synaptic cleft) Presynaptic neuron Postsynaptic neuron

32. Put graphic from text here

33. Neurotransmitters • ____+ known substances or suspected to be neurotransmitters • Acetylcholine (ACh) and Norephinephrine (NE) best known • Acetylcholinestrease (AChE) is an enzyme that breaks down ACh

34. Neurotransmitters • Others include: dopamine serotonin opioids (endorphin) • Many drugs either _________________ ________________________________

35. Integration • Neurons handle “excitatory” and “inhibitory” signals • Each neuron sums up the two signal types in a process known as INTERGRATION • Result: neuron either “fire” signal down axon…or not “fire signal