Chapter 48 ~ Nervous System

1. Chapter 48 ~ Nervous System

2. Neurons Glial cells Soma Axon Dendrite Synapse Neurotransmitters Action potential Motor neurons Interneurons Sensory neurons Myelin sheath Schwann cells Reflex arc The Nervous System http://outreach.mcb.harvard.edu/animations/synaptic.swf

3. Nervous systems • Effector cells~ muscle or gland cells • Nerves~ bundles of neurons wrapped in connective tissue • Central nervous system (CNS)~ brain and spinal cord • Peripheral nervous system (PNS)~ sensory and motor neurons

4. Structural Unit of Nervous System • Neuron~ structural and functional unit • Cell body~ nucelus and organelles • Dendrites~ impulses from tips to neuron • Axons~ impulses toward tips • Myelin sheath~ supporting, insulating layer • Schwann cells~PNS support cells • Synaptic terminals~ neurotransmitter releaser • Synapse~ neuron junction

8. Simple Nerve Circuit http://msjensen.cehd.umn.edu/1135/Links/Animations/Flash/0016-swf_reflex_arc.swf • Sensory neuron: convey information to spinal cord • Interneurons: information integration • Motor neurons: convey signals to effector cell (muscle or gland) • Reflex: simple response; sensory to motor neurons • Ganglion (ganglia): cluster of nerve cell bodies in the PNS • Supporting cells/glia: nonconductiong cell that provides support, insulation, and protection

10. Neural signaling http://bcs.whfreeman.com/thelifewire/content/chp44/4403s.swf http://outreach.mcb.harvard.edu/animations/actionpotential.swf • Membrane potential (voltage differences across the plasma membrane) • Intracellular/extracellular ionic concentration difference • K+ diffuses out (Na+ in); large anions cannot follow….selective permeability of the plasma membrane • Net negative charge of about -70mV

11. http://bcs.whfreeman.com/thelifewire/content/chp44/4402s.swf Neural signaling http://www.mind.ilstu.edu/curriculum/neurons_intro/flash_electrical.php?modGUI=232&compGUI=1827&itemGUI=3158 • Excitable cells~ cells that can change membrane potentials (neurons, muscle) • Resting potential~ the unexcited state of excitable cells • Gated ion channels (open/close response to stimuli): photoreceptors; vibrations in air (sound receptors); chemical (neurotransmitters) & voltage (membrane potential changes)

12. Neural signaling • Graded Potentials (depend on strength of stimulus): • 1- Hyperpolarization (outflow of K+); increase in electrical gradient; cell becomes more negative • 2- Depolarization (inflow of Na+); reduction in electrical gradient; cell becomes less negative

14. Neural signaling • Threshold potential: if stimulus reaches a certain voltage (-50 to -55 mV)…. • The action potential is triggered…. • Voltage-gated ion channels (Na+; K+) • 1-Resting state •both channels closed • 2-Threshold •a stimulus opens some Na+ channels • 3-Depolarization•action potential generated •Na+ channels open; cell becomes positive (K+ channels closed) • 4-Repolarization•Na+ channels close, K+ channels open; K+ leaves •cell becomes negative • 5-Undershoot•both gates close, but K+ channel is slow; resting state restored • Refractory period~ insensitive to depolarization due to closing of Na+ gates

15. Neural signaling • “Travel” of the action potential is self-propagating • Regeneration of “new” action potentials only after refractory period • Forward direction only • Action potential speed: • 1-Axon diameter (larger = faster; 100m/sec) • 2-Nodes of Ranvier (concentration of ion channels); saltatory conduction; 150m/sec

16. Synaptic communication • Presynaptic cell: transmitting cell • Postsynaptic cell: receiving cell • Synaptic cleft: separation gap • Synaptic vesicles: neurotransmitter releasers • Ca+ influx: caused by action potential; vesicles fuse with presynaptic membrane and release…. • Neurotransmitter

18. Signal transmission http://www.bayareapainmedical.com/neurtrns.html

19. Neurotransmitters http://www.blackwellpublishing.com/matthews/neurotrans.html • Acetylcholine (most common) •skeletal muscle • Biogenic amines(derived from amino acids) •norepinephrine •dopamine •serotonin • Amino acids • Neuropeptides(short chains of amino acids) •endorphin

20. Nervous System • Central Nervous System • Crainial Nerves • Spinal Nerves • Peripheral Nervous System • Sensory (afferent) Division • Sensing external environment • Sensing internal environment • Motor (Efferent) Division • Autonomic Nervous System • Sympathetic Nervous System • increase energy consumption • Parasympathetic Nervous System • conservation of energy • Somatic Nervous System • voluntary, conscious control, muscles

21. Vertebrate PNS

25. Meninges Cerebrospinal fluid Ventricles Brain Stem Medulla oblongata Pons midbrain Diencephalon Thalamus Hypothalamus Cerebellum The Brain

26. The Vertebrate Brain • Forebrain • •cerebrum~memory, learning, emotion • •cerebral cortex~sensory and motor nerve cell bodies • •corpus callosum~connects left (analytical) and right (creative) hemispheres • •thalamus (main input/output from cerebrum); hypothalamus (hormone production) • Midbrain • •inferior (auditory) and superior (visual) colliculi • Hindbrain •cerebellum~coordination of movement•medulla oblongata/ pons~autonomic, homeostatic functions

28. Pituitary Gland Corpus Callosum

29. Cerebral hemispheres Cerebral cortex—”gray matter” Convolutions Cerebral lobes Frontal lobe—conscious thought and muscle control. Parietal Lobes—receive information from skin receptors. Occipital Lobe—receives visual input. Temporal Lobe—has areas for hearing and smelling. Cerebrum