Nervous System

Functions Communication Communication Integration Integration Control Control Responds Responds External environment External environment Internal Internal

Divisions of the Nervous System 2 main 2 main Central and peripheral Central and peripheral

CNS 2 organs 2 organs Brain Brain Spinal cord Spinal cord

PNS All other nerves All other nerves 12 pairs of cranial nerves: branch 12 pairs of cranial nerves: branch 31 pairs of spinal nerves: branch 31 pairs of spinal nerves: branch

PNS Divisions 2 major division 2 major division Somatic…voluntary movement; have control…writing Somatic…voluntary movement; have control…writing Autonomic division; involuntary..no purposeful control Autonomic division; involuntary..no purposeful control

Autonomic N.S. 2 division 2 division Sympathetic division…fibers speed up processes “Saber tooth tiger” Sympathetic division…fibers speed up processes “Saber tooth tiger” Inc: hr, breathing, bld supply to muscles….digesting slows down Inc: hr, breathing, bld supply to muscles….digesting slows down Parasympathetic: fibers slow down processes Parasympathetic: fibers slow down processes “Resting And Digesting” “Resting And Digesting” Decrease functions….hrt rate slower, slower rsp. Inc absorption of nutrients Decrease functions….hrt rate slower, slower rsp. Inc absorption of nutrients

Microscopic View Cells of Ns Cells of Ns 2 Types 2 Types Neuron (3) Neuron (3) Glia (3) Glia (3)

3 types Classified according to function Classified according to function Sensory: conduct impulses to spinal cord and brain (external and internal environment) Sensory: conduct impulses to spinal cord and brain (external and internal environment) Ex: external:temp, pain Ex: external:temp, pain internal: listening, absorption of nutrients, heart beat, breathing internal: listening, absorption of nutrients, heart beat, breathing

Types of neuron cont. Motor neurons: conduct impulses away from brain and spinal cord to muscles and glands Motor neurons: conduct impulses away from brain and spinal cord to muscles and glands Interneurons: conduct impulses from sensory to motor Interneurons: conduct impulses from sensory to motor

Neurons Basic nerve cell of ns Basic nerve cell of ns 3 main parts 3 main parts Dendrites, cell body, axon Dendrites, cell body, axon 3 types: 3 types: Sensory, motor, interneurons Sensory, motor, interneurons

Neuron Parts Dendrites: pick up stimulus and carry to cell body Dendrites: pick up stimulus and carry to cell body Cell body; (contains nucleus) modifies info from dendrites Cell body; (contains nucleus) modifies info from dendrites Axon: carries impulse away to next neuron Axon: carries impulse away to next neuron Covered in the PNS are covered myelin: white fatty substance that speeds up nerve impulse transmission Covered in the PNS are covered myelin: white fatty substance that speeds up nerve impulse transmission Schwann cells make up myelin Schwann cells make up myelin

Myelin Formed by schwan cells Formed by schwan cells Form long rings Form long rings Grooves between each ring Grooves between each ring Called: nodes of Ranvier Called: nodes of Ranvier Nerve impulses jump over these nodes ; which speed it up Nerve impulses jump over these nodes ; which speed it up

Axon End: branches: terminal branches End: branches: terminal branches End of branches, tiny nodes called synaptic knobs End of branches, tiny nodes called synaptic knobs Synaptic knobs release chemicals: neurotransmitters (allows an impulse to cross the synapse) Synaptic knobs release chemicals: neurotransmitters (allows an impulse to cross the synapse)

Glia 3 types; astrocytes, microglia, ogliodendrocytes 3 types; astrocytes, microglia, ogliodendrocytes Astrocytes star shaped and attach blood vessels to neurons Astrocytes star shaped and attach blood vessels to neurons Form: BBB blood brain barrier (protective) Form: BBB blood brain barrier (protective) Microglia: digest pathogens Microglia: digest pathogens O: help form myelin O: help form myelin

Nerve Coverings Made of fibrous connective tissue Made of fibrous connective tissue 3 coverings 3 coverings Endoneurium: surrounds individual fibers Endoneurium: surrounds individual fibers Perineurium: surrounds a group (facisle) Perineurium: surrounds a group (facisle) Epineurium: surrounds entire nerve Epineurium: surrounds entire nerve

Worksheet Questions Explain the parts a reflex arc Explain the parts a reflex arc two-neuron arc and three neuron arc two-neuron arc and three neuron arc Give 2 examples Give 2 examples What is a sensory receptor and effector, how does it pertain to a reflex arc? What is a sensory receptor and effector, how does it pertain to a reflex arc? How does a reflex occur? How does a reflex occur? What is a ganglion? What is a ganglion?

Reflexes Protection Protection Quick response with afterthought Quick response with afterthought Examples: knee-jerk, touch hot, feel pain (withdrawal) Examples: knee-jerk, touch hot, feel pain (withdrawal) Response sent from spinal cord, message then sent to brain Response sent from spinal cord, message then sent to brain

Reflex arcs 2 types: 2 types: Simplest: two neuron arcs(sensory and motor neurons) Simplest: two neuron arcs(sensory and motor neurons) Second type: sensory, interneurons, and motor neurons Second type: sensory, interneurons, and motor neurons Both pathways synapse within the spinal cord Both pathways synapse within the spinal cord