1. 1 The Nervous System: Introduction Transmission of signals for communication and for coordination of body systems

2. 2 Nervous System Functions  The nervous system has three overlapping functions Gathering of sensory input Integration or interpretation of sensory input Causation of a response or motor output Sensory input

3. 3 Introduction  Sensory input The nervous system has millions of sensory receptors to monitor both internal and external change  Integration It processes and interprets the sensory input and makes decisions about what should be done at each moment  Motor output Causes a response by activating effector organs (muscles and glands)

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5. 5 Nervous System  Two types of cells in nervous system: Neurons – motor, sensory, association Neuroglia – 6 types  CNS (Central Nervous System): Brain – cerebrum, diencephalon, brain stem, cerebellum Spinal Cord – horns, columns; ascending and descending tracts  PNS (Peripheral Nervous System): Cranial nerves – 12 pairs Spinal nerves – 31 pairs

6. 6 Neurons  Functional unit of nervous system  Have capacity to produce action potentials electrical excitability/electrical impulses

7. 7 Neuron: Parts and Functions of Ranvier

8. 8 Classification of Neurons  Neurons can be classified functionally or structurally Functional classification is usually used to describe how the neurons work within us – see Table 8-1, p156 Structural classification is based on the number of processes that extend from the cell body.

9. 9 1. 3. 2.

10. 10 Structural Classification of Neurons  Based on number of processes found on cell body multipolar = several dendrites & one axon  most common cell type bipolar neurons = one main dendrite & one axon  found in retina, inner ear & olfactory unipolar neurons = one process only(develops from a bipolar)  are always sensory neurons

11. 11 Blood-Brain Barrier  The blood-brain barrier is selective and incomplete, not an absolute barrier  Nutrients, such as glucose, essential amino acids, and some electrolytes, move passively by facilitated diffusion through the endothelial cell membranes  Bloodborne metabolic wastes, such as urea and creatinine as well as proteins, certain toxins, and most drugs, are prevented from entering brain tissue

12. 12 The Nervous System: Nerve Impulses Action potentials = AP Neuronal electrical activity

13. 13 Electrical Activity of Axons  Functional characteristics of neurons: Excitability/irritability:  Ability to respond to stimuli by producing electrical impulses. Conductivity:  Ability to transmit electrical impulses

14. 14 Ion Channels 2 Proteins within the membrane can open and close, thus allowing ions to travel in or out. 2 K+ channels allow outward flow 2 Na+, inward

15. 15 The Nervous System: The Synapse Neurotransmitters TRANSMISSION across a Synapse

16. 16 Transmission of Nerve Impulses Between Neurons Synapse: junction between neurons, muscles, glands Signal is carried by neurotransmittors that diffuse across the synaptic cleft.

17. 17 Fig. 12.14

18. 18 Transmission of Nerve Impulses Between Neurons Neurotransmitters can be: Stimulatory: initiates action potential eg. Acetylcholine Inhibitory: prevents action potential eg. GABA, Dopamine

19. 19 Neurotransmitters by function  Excitatory – generally cause increase excitability (depolarization) ACH = Acetylcholine NE = Norepinephrine EPI = Epinephrine DA = Dopamine  Inhibitory – generally cause decrease excitability (hyperpolarization) GABA = Gamma-aminobutyric acid 5-HT = Serotonin Endorphins, enkephalins, dynorphins

20. 20 Nervous System and Aging:  Page 178

21. 21 Clinical Terms:  Neurology  Rabies  Guillain-Barre