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The Nervous System

The Nervous System. Functions of the Nervous System. 1. Monitors internal and external environment 2. Take in and analyzes information 3. Coordinates voluntary and involuntary responses. Organs of the Nervous System. Brain and Spinal Chord (CNS)

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The Nervous System

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  1. The Nervous System

  2. Functions of the Nervous System • 1. Monitors internal and external environment • 2. Take in and analyzes information • 3. Coordinates voluntary and involuntary responses.

  3. Organs of the Nervous System • Brain and Spinal Chord (CNS) • Sensory Receptors of Sense Organs (eyes, ears etc) • Nerves connect nervous system with other systems

  4. Divisions of the Nervous System • 1. Central Nervous System • Spinal Chord and Brain • Processing coordination of stimulus and response 2. Peripheral Nervous System - All neural tissue outside the CNS - Delivers sensory information to the CNS and carries motor commands to the effectors

  5. Functions of the CNS • Are to process and coordinate: • - sensory data: • From inside and outside the body • Movement: • Control activities of peripheral organs (e.g. skeletal muscles) • Higher functions of the brain • Intelligence, memory, learning, emotion

  6. Functions of the PNS • 1. Deliver sensory information to the CNS • 2. Carry commands to peripheral tissues and systems

  7. Nerves • Also called peripheral nerves: • Bundles of axon with connective tissues and blood vessels • Carry sensory information and motor commands in PNS: • Cranial nerves: connects to brain (12 pairs) • Spinal nerves: attach to spinal chord (31 pairs)

  8. Divisions of the PNS • Afferent Division: • Carries information from PNS to CNS • Efferent Division: • Carries motor commands from CNS to PNS • Has somatic and autonomic components

  9. The Efferent Division of the PNS • Somatic Nervous System (SNS) • Controls skeletal muscle contraction • Voluntary muscle contractions • Reflexes • Autonomic Nervous System (ANS) • Controls subconscious actions • Contraction of smooth and cardiac muscle • Glandular secretions

  10. The Autonomic Nervous System Splits • Parasympathetic Nervous System • Sympathetic Nervous System

  11. Neural Tissue • Contains 2 kinds of cells • Neurons • Cells that send and receive signals • Neuroglia • Cells that support and protect nerves

  12. Neurons • The basic functional units of the nervous system • Parts of a neuron • Cell body (Soma) • Short, branched dendrites • Long, single axon

  13. Structure of a Neuron

  14. Dendrites • Highly branched • Dendritic spines: • Receive information from other neurons • 80-90% of neuron surface area

  15. The Axon • Long • Carries electrical signal (action potential) to target • Axon structure is critical to function

  16. Nodes and Internodes • Internodes • Myelinated segments of axon • Nodes • Also called nodes of Ranvier • Gaps between internodes • Where axons may branch

  17. The Synapse • Area where a neuron communicates with another cell

  18. Synapse • Areas where a neuron communicates with another cell • Presynaptic Cell • Neuron that sends message • Postsynaptic Cell • Cell that receives message • Synaptic Cleft • Gap that separates the presynaptic membrane and the postsynaptic membrane

  19. The Synaptic Knob • Is expanded area of axon • Contains synaptic vesicles of neurotransmitters • Chemical messengers • Released at presynaptic membrane • Affect receptors of postsynaptic membrane

  20. Functional Classifications of Neurons • Sensory Neurons • Deliver information to CNS • Motor Neurons • Stimulate or inhibit peripheral tissues • Interneurons • Located between sensory and motor neurons • Analyze inputs, coordinates outputs

  21. Neuroglia • Half the volume of the nervous system • Many types of neuroglia in the CNS and PNS

  22. Neuroglia Functions • Line of central canal of spinal chord and ventricles of brain • Repair damaged neural tissue • Processes contact between other neuron cell bodies

  23. Neuorglia • Wrap around axons to form myelin sheaths (Schwann Cells) • Increases speed of action potentials • Myelin insulates myelinated axons • Makes nerves appear white (white matter)

  24. White and Grey Matter • White Matter • Regions of CNS with many myelinated nerves • Grey Matter • Unmyelinated areas of CNS

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