1. I. Overview of Nervous System NERVOUS SYSTEM Central Nervous System (CNS) Peripheral Nervous System (PNS) Somatic Nervous System Autonomic Nervous System (ANS) SYMPHATHETIC NERVOUS SYSTEM PARASYMPHATHETIC NERVOUS SYSTEM

2. CNS- brain and spinal cord PNS- cranial nerves and spinal nerves SNS- Controls skeletal/voluntary muscles and transmits sensory information to the CNS ANS- Controls automatic/involuntary body functions Sympathetic Division - Arouses body to expend energy – Fight or flight Parasympathetic Division- Peacekeeping or housekeeping system. Calms body to conserve and maintain energy.

3. II. General functions A. Sensory, integration, and motor – needed to maintain homeostasis. Ex. Seeing a red light - sensory Red = Stop – integration Foot pressing brake - motor 1. Sensory – using sensory receptors to monitor changes inside and outside your body. 2. Integration – processes and interprets sensory and how to proceed/decide what to do. 3. Motor – effects a response by activating muscles or glands – called effectors.

4. III. Nervous Tissue A. Histology –Neurons – nerve cell component – conducts impulses; neuron = one, nerve = a bundle. –Neuroglia or glia, – Latin for “nerve glue” – supportive cells – do not conduct impulses used for vascular support.

6. B. Structure of neurons,– 3 basic parts –Cell body or soma – contains structures like a common cell – cytoplasm, mitochondria, lysosomes, Golgi bodies, microtubules (structural support), Nissl bodies (ER), large nucleus that includes a nucleolus. –Dendrites – Latin for “tree” – look like branch structures. Highly branched structures that provide receptive surfaces for communication (basically they receive impulses and conduct impulses to the soma).

7. - Axon – long, slender, cylinder shaped process that has a smooth surface. It carries impulses away from the soma to other structures (axons or dendrites). Axon has several different structures. –Axon collateral – a branching axon. –Axon terminals or telodendria – fine extensions at the end of the axon. (book uses terminal branches- we are using telodendria or axon terminals) –Synaptic knob or synaptic bulb – swollen end of an axon. (book uses axon terminals (secretory region- don’t use this)

8. Myelin sheath – insulating, lipid material wrapped around an axon. It helps to speed up reactions. Myelinated tissues are called white matter and unmyelinated tissue is called gray material. Nodes of Ranvier – the spaces between myelin sheaths.

9. C.Neuroglia or glia – specialized cells Oligodendrocytes – in central nervous system – forms myelin sheaths in central nervous system. Schwann cells – peripheral nervous system – forms myelin sheaths in the peripheral nervous system Astrocytes – looks like star shaped structures – forms blood brain barrier and provides active transport of blood used for nourishment.

10. Microglia- phagocytic cells used for defense in the Central Nervous System Ependymal cells -lines fluid-filled cavities in the brain and spinal cord. It has cilia to keep fluid circulating within the cavities

11. IV. Classifications of neurons A. Structural divisions –Multipolar – most common type, they have cell body with many nerve fibers/dendrites, and one axon. –Bipolar – has cell body with one dendrite and one axon. Are found in sensory tracts, retina, inner ear, olfactory cells (smell). – Unipolar- has a cell body, one axon extension branching into two axon type structures, central process and a peripheral process, one acts as the axon and one as the dendrite

12. B.Functional divisions/classifications, Sensory neurons/afferent neurons – carry conducting impulses from receptor to the brain and spinal cord/central nervous system. Interneurons/association neurons – transports impulses between neurons with brain and spinal cord/central nervous system. Motor neurons/efferent neurons – conducts impulses from brain and spinal cord/central nervous system to effectors (muscles or glands).

13. V. Neurophysiology Overview- A. Neurophysiology – the functions of neurons – Nerve Impulses 1. Neurons are highly irritable (they respond to stimuli). 2. When a neuron is adequately stimulated, an electrical impulse can be generated. 3. Impulse is generated along the axon and the plasma membrane (neurilemma).

14. 4.Ion differences allow the cell membrane to be more permeable using a sodium/potassium pump where two K+ are pumped in and three Na+ are ejected from the cell. (solute pump- active transport) 5. Membrane potential – the difference in electrical charge between inside and outside of the plasma membrane due to the various concentrations of ions that normally exist in the ECF and ICF.

15. Measuring Membrane Potential Figure 11.7

16. B. Role of Ion Channels 1. Types of plasma membrane ion channels: –Passive or leakage channels – always open –Chemically gated channels – open with binding of a specific neurotransmitter –Voltage-gated channels – open and close in response to membrane potential –Mechanically gated channels – open and close in response to physical changes of receptors

17. Operation of a Gated Channel Figure 11.6a

18. Operation of a Voltage-Gated Channel

20. VI. Conduction of Nerve Impulses A. Resting Membrane Potential (RMP) – when a neuron is not conducting electrical signals, it is said to be “resting”. At rest, a neuron’s resting membrane potential is typically maintained at about -70 mV. This is due to differences in the ions inside and outside of the cell

21. Resting Membrane Potential Figure 11.8

22. B. Changes in Membrane Potential 1. Changes are caused by three events –Depolarization – the inside of the membrane becomes less negative as Na+ rushes into the cell –Repolarization – the membrane returns to its resting membrane potential, Na+ gates close, K+ gates open –Hyperpolarization – the inside of the membrane becomes more negative than the resting potential due to too much K+ leaving the cell These 3 events generate an Action Potential (AP)- principle method neurons use to send signals over long distances (nerve impulse)

23. Changes in Membrane Potential Figure 11.9

24. C. Action Potentials (APs) A brief reversal of membrane potential Action potentials are only generated by muscle cells and neurons They do not decrease in strength over distance They are the principal means of neural communication This is an electrical fluctuation that travels along the surface of a neuron’s plasma membrane. Action potential is typically maintained at +30mV.

25. Propagation of an Action Potential (Time = 2ms) Figure 11.13b

26. Phases of the Action Potential 1 – resting state 2 – depolarization phase 3 – repolarization phase 4 – hyperpolarization Figure 11.12

27. Action Potential Graph a. Resting membrane potential – -70 mV due to ion differences. b. Depolarization – moves up to zero and higher to +35 mV. Also called AP c.Repolarization – going back to resting membrane potential. Na+ gates close and K+ gates open.K+ rush out of the cell. High K+ outside of the cell and high Na+ inside the cell. d. Hyperpolarization – causes change away from 0 mV. More K+ moved out than was necessary. Neuron cannot be stimulated due to too much K+ in the cell. e. Refractory period – a brief period during which a local area of an axon’s membrane resists stimulation – no stimulus can occur. Na+ /K+ pump moves Na+ out of the cell and K+ into the cell. Reestablishes or balances out the original distribution of ions.

28. VII. Difference in Conduction A. Unmyelinated fibers – impulse or action potential are produced along the length of the axon – the impulse travels slower. B. Myelinated fibers – impulses or action potentials are generated at the nodes of Ranvier called saltatory conduction – impulses travel faster. 1. Saltatory conduction –process in which a nerve impulse travels along a myelinated fiber by jumping or leaping from one node of Ranvier to the next.

29. Saltatory Conduction Figure 11.16

30. VIII. Synaptic Transmission A. Synapse – the location or place where signals are transmitted from neuron to neuron. 1. There are two types: –Electrical synapse – occurs where two cells are joined end to end by gap junctions (found in cardiac muscle and some smooth muscles…are part of the cardiac conduction system). Are important in the CNS in arousal from sleep, mental attention, emotions and memory, ion and water homeostasis – Chemical synapse – chemical transmitter also called a neurotransmitter. Used to send a signal from the pre-synaptic cell to the post-synaptic cell.

31. Synapses Figure 11.17

32. Synaptic vesicles containing neurotransmitter molecules Axon of presynaptic neuron Synaptic cleft Ion channel (closed) Ion channel (open) Axon terminal of presynaptic neuron Postsynaptic membrane Mitochondrion Ion channel closed Ion channel open Neurotransmitter Receptor Postsynaptic membrane Degraded neurotransmitter Na + Ca 2+ 1 2 3 4 5 Action potential Figure 11.18 Synaptic Cleft

33. Structures to Know-synapse A.Pre-synaptic membrane – the semi-permeable membrane of the synaptic bulb. B.Synaptic knob – end of an axon. C.Synaptic vesicles – in the synaptic knob, houses neurotransmitters. D.Neurotransmitters – located inside the synaptic vesicles. E.Synaptic cleft – space between pre-synaptic membrane and post-synaptic membrane. F.Post-synaptic membrane – the semi-permeable membrane of the receptor site. G. Ion channels (protein receptors) – located on the post- synaptic membrane, where neurotransmitter binds

34. What Happens in Synaptic transmission? 1.Impulse reaches synaptic bulb 2.Presynaptic membrane depolarizes 3.Ca+ 2 channels/gates open 4.Ca+ 2 enters synaptic bulb 5.Vesicles migrate to presynaptic membrane 6.Vesicle fuse with membrane 7.Neurotransmitter release into cleft by exocytosis 8.Neurotransmitters binds to receptor on post synaptic membrane 9.Postsynaptic neuron depolarizes 10.Passes impulse to next postsynaptic membrane

35. IX. Neurotransmitters A.Neurotransmitters- chemical messengers used in neuron impulse transmission. 1. stored in synaptic vesicles in synaptic bulb. 2. 50 different neurotransmitters have been identified 3. classified as either inhibitory or excitatory based on function 4. classified as Acetylcholine (ACh), amines, amino acids, peptides, purines, dissolved gases 5. common examples- Acetylcholine (ACh), epinephrine, norepinephrine, dopamine, serotonin, endorphins