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 Cord (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 Cord 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 cord (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. The Synapse Area where a neuron communicates with another cell

17. 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

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

19. 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

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

21. Neuroglia Functions Lines central canal of spinal cord and ventricles of brain Repair damaged neural tissue Processes contact between other neuron cell bodies

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

23. White and Grey Matter White Matter – Regions of CNS with many myelinated nerves Grey Matter – Unmyelinated areas of CNS

24. Quick Quiz 1.Name the 2 major divisions of nervous system and give example of what they contain and their function 2.How many pairs of nerves do we have and describe 3.Describe 3 aspects of the neuron 4.What is a synapse? Why is it important? 5.What is neuroglia? Why is it important?