Nervous System Communication

1. Nervous System Communication

2. Kid ConcussionsIn The News

3. Neurons • Nerve cells • Parts of neurons • Cell body • Long extensions (fibers=dendrites or axons) • Message = nerve impulse

4. Animal Nervous Systems • Sponges – no nervous system • Other animals all have neurons in systems

5. Nerve Net • In all cnidarians • Interconnected nerve cells • No brain

6. Ringlike Nervous System • In echinoderms • Ring with 5 radiating nerves

7. Ladderlike Nervous System • In many Platyhelminthes • Some have distinct brain (ganglia)

8. Annelid Nervous System • Segmental ganglia • Ganglia = aggregations of nervous tissue • Ventral nerve cord & brain Arthropod Mollusks(depends level of activity) some have giant fibers

9. Vertebrate Nervous System • Central nervous system • Brain & spinal cord • Peripheral nervous system • Nerves to & from CNS

10. Nerve Cells(Neurons) • Cell body • Contains nucleus and organelles • Produces substances necessary for cell to live & function • Axon (conducts or passes on impulse) • Long cell extension • May have myelin covering • Dendrites (receive impulse) • Usually short cell extensions • No myelin covering • most neurons have multiple dendrites

11. Sensory Neurons • Receive information from sense organ receptors • Transmit to the central nervous system • Cell bodies of sensory neurons lie near the CNS

12. Motor Neurons • Transmit commands away from CNS to effector (muscle or gland) • Each neuron has one long axon • Cell bodies on most motor neurons lie in or near CNS

13. Interneurons • Located within brain & spinal cord • Integrate information • Axons may or may not be myelinated • usually axons are shorter than those in PNS

14. Neuroglia • Nerve support cells • Provide support, protection, & nutritional stability • Schwann cells (special neuroglial cells) • Found around axons • Produce myelin sheath • Oligodendrocytes – produce myelin sheath around some CNS axons

15. Myelin Sheath • Insulates axon • Nodes of Ranvier-allows impulse to move at a greater speed along axon • Uninsulated areas- no myelin sheath

16. Nerve Impulses • Electrical signals transmitted along membranes of nerves

17. Resting Potential • Neuron is electrically charged at rest • Outside is positively charged • Inside is negatively charged

18. Sodium-Potassium Pump • Proteins embedded within cell membrane • Moves sodium to the outside • Moves potassium to the inside • Maintains resting potential • Requires energy (ATP)

20. Action Potential • Nerve impulse is started by a stimulus • Stimuli cause movements of ions through membrane • Threshold potential • Sufficient stimulation to depolarize membrane • Action potential • Rapid reversal of membrane electric potential

22. Nerve Transmission • Action potential at one point depolarizes next area • Depolarization moves in self-propagating wave

23. Saltatory Conduction • Nerve impulse jumps & moves faster along myelinated axon

24. Synapse • Area where nerve communicates • Transfers message • Another neuron • An effector

25. Synaptic Cleft • Neurons do not touch other neurons or effector cells • Nerve impulse must cross gap (electrical signal is changed to a chemical signal)

26. Neurotransmitters • Organic molecules (> 60 different chemicals) • Transfer message across synaptic cleft • Attach to receptors on target cell

27. Neuromuscular Junctions • Synapse between neuron & skeletal muscle • Neurotransmitter is aceytylcholine

28. Neuron to Neuron Connections • Uses many different neurotransmitters (such as dopamine, norepinephrine, serotonin) • Some cause different effects • Excitatory synapse – continuation of impulse • Inhibitory synapse – reduce ability to depolarize

29. Integration of Nerve Impulses • Summed impulses determine if postsynaptic neuron will depolarize

30. Human Nervous System • Central nervous system • Brain • Spinal cord • Peripheral nervous system • Brings messages to & from CNS • Somatic nervous system – voluntary • Autonomic nervous system - involuntary

31. Central Nervous System • Integrates sensory & motor impulses

33. Spinal Cord • Connects peripheral nervous system with brain • Receives information via spinal nerves • Includes reflex arcs

34. CNS Protection - Meninges • Layers of membranes • Dura mater • Arachnoid • Pia mater

35. Peripheral Nervous System • Sensory & motor impulses • Cranial nerves communicate directly with brain, some are strictly sensory or motor, some are mixed.

36. Spinal Nerves • Sensory & motor nerve fibers • 31 pairs and all are mixed nerves • Travel directly to spinal cord • Nerves are bundled to form mixed nerves

37. Motor Neuron Systems • Somatic nervous system, part of PNS • Voluntary • Movements of skeletal muscles • requires a single motor neuron • Reflex = automatic response to nerve stimulation • Autonomic nervous system, part of PNS • Involuntary motor pathways • requires two motor neurons

38. Divisions of the Autonomic Nervous System • Parasympathetic • Acetylcholine is the neurotransmitter • Prevails during periods of inactivity • Housekeeping • Sympathetic • Norepinephrine is the neurotransmitter • “fight or flight” • Responds to stress • Prepares body for action • Parasympathetic & sympathetic together help to maintain homeostasis

40. Psychoactive Drugs • Affect action of neurotransmitters In specific parts of the brain • Some are abused

45. Drug Addiction • Chronic use (or abuse) of psychoactive drugs • Person becomes physically dependant • Drug use tends to increase due to drug tolerance

46. End Chapter 32