Understanding the Nervous System: Functions and Divisions

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