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) Sensory Receptors of Sense Organs (eyes, ears etc) Nerves connect nervous system with other systems

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

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

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

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)

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

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

The Autonomic Nervous System Splits Parasympathetic Nervous System Sympathetic Nervous System

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

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

Structure of a Neuron

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

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

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

The Synapse Area where a neuron communicates with another cell

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

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

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

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

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

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)

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