The Nervous System
Coordinates the activity of muscles, organs, senses, and actions
Made up of nervous tissue Has 3 main functions:
1. Receives sensory Input 2. Integration 3. Dictates motor output
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Divisions of the Nervous System
Central Nervous System (CNS) Brain and spinal cord Interprets incoming sensory signals Dictates motor responses
Peripheral Nervous System (PNS) Ganglia Nerves
Cranial nerves and spinal nerves Communication between regions of
body and CNS pg 16
Review of Nervous Cells
Neuron Cell body Dendrite Axon
Myelin Sheath
Neuroglia Interneuron
Reflex Arc Synapse
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Organization of a Nerve Endoneurium
Surrounds each axon (nerve fiber) Myelinated and Unmyelinated axons Motor and Sensory nerve fibers Loose CT
Perineurium Bundles axons into fascicles CT
Epineurium Bundles fascicles into a nerve Fibrous CT
CT layers contain blood vessels
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Types of Nerve Signals/Fibers
Sensory (afferent) Picked up by sensory receptors thru body Carried by nerve fibers of PNS into CNS
Motor (efferent) Carried away from the CNS by nerve fibers
into PNS Innervate muscles and glands Causes these organs to contract or secrete
Remember: SAME
Sensory and Motor Signals/Fibers Somatic sensory
Body senses touch, pressure, temperature, vibration of body, muscles
stretching, balance Visceral sensory
Organ senses Stretch, pain, temperature in organs (eg) nausea, hunger, cramps
Somatic motor Body movement Voluntary contraction of skeletal muscles
Visceral motor Organ movement Contraction of smooth muscle, glands = Autonomic Nervous System (involuntary)
CNSBrain
Spinal cord
PNSCranial nerves and spinal nerves
Sensory (afferent)division
Motor (efferent)division
Somatic sensory
General: Touch, pain, pressure, vibration
Special: hearing, equilibrium, vision, smell
Visceral sensory
General: Stretch, pain, temperature, nausea, hunger
Special: Taste
Somatic motor
General: Motor innervation of all skeletal muscles
Visceral motor
General: Motor innervation of smooth muscle, cardiac muscle, and glands; = ANS
Parasympathetic division
Sympathetic division
CNS – Spinal Cord
Runs through vertebral canal of the vertebral column Protected by bone, meninges, and cerebrospinal fluid Spinal cord made of a core of gray matter surrounded
by white matter 31 pairs of spinal nerves branch off spinal cord through
intervertebral foramen Functions in many ways:
Involved in sensory and motor innervation of body inferior to the head (through spinal nerves)
Provides a 2-way conduction pathway for signals between body and brain
Major center for reflexespg 63
Meninges of Spinal Cord
Membranes surrounding the spinal cord 3 Layers of connective tissue Functions
Protect spinal cord Contains cerebrospinal fluid Protect blood vessels serving spinal cord
Meninges of Spinal Cord
Dura mater (superficial) Spinal dural sheath Does not attach to bone
Epidural space Fat and veins Between dura mater and vertebra
Subdural space Between dura mater and arachnoid
pg 67
Meninges of Spinal Cord
Arachnoid mater (middle) Impermeable layer = barrier Raised off pia mater by rootlets
Subarachnoid space Between arachnoid and pia mater Contains CSF
Pia mater (deep) Highly vascular Adheres to brain/spinal cord tissue
pg 67
Regions of Spinal Cord
Cervical Thoracic Lumbar Sacral Coccygeal Cervical + Lumbar enlargements Cauda equina Conus medullaris Filum terminale
CT & pia mater Attaches to coccyx
pg 63pg 24
Gray Mater
Consists of neuron cell bodies, unmyelinated axons, dendrites, and neuroglia
Shaped like an “H” Gray commissure (crossbar) Central canal
Posterior horns Anterior horns
pg 63
Gray Mater
Posterior horns Consist of interneurons that transmit in from outside spinal cord
into it Dorsal root contain sensory fibers
Somatic Sensory (SS) Visceral Sensory (VS)
Dorsal root ganglia - swelling in dorsal root that these interneurons pass through
Anterior horns Cell bodies of motor neurons send info out of spinal cord to
muscles and glands Ventral Root contains Motor Fibers
Visceral Motor Somatic Motor pg 63
White Mater
Surrounds gray matter Composed of myelinated and unmyelinated axons Divided into white columns (funiculi)
Posterior funiculus Anterior funiculus Lateral funiculus
Allow for communication between Parts of the spinal cord Spinal cord and brain
pg 63
White Mater 3 types of nerve fibers:
Ascending Carry sensory info from sensory neurons of body to brain touch, pressure, pain, temperature
Descending Carry motor instructions from brain to spinal cord Contraction of muscles and secretion of glands control precise, skilled movement = writing, maintain
balance, create movement Commissural
Cross from one side of cord to the other
Spinal Nerves (31 Pairs)
Part of the PNS (Somatic) Lie in intervertebral foramina
Send lateral branches to body Named according to their point of issue from the vertebral column
8 pairs of cervical spinal nerves; C1-C8
12 pairs of thoracic spinal nerves; T1-T12
5 pairs of lumbar spinal nerves; L1-L5
5 pairs of sacral spinal nerves; S1-S5
1 pair of coccygeal spinal nerves; C01
pg 71-2
Spinal Nerves
Each spinal nerve connected to spinal cord via dorsal (sensory) and ventral (motor) root
Spinal nerves branch into dorsal ramus and ventral ramus Ventral ramus
Connects to rami communicans, which then lead to sympathetic chain ganglia
Supply anterior and lateral regions of the neck, trunk, and limbs
Dorsal ramus Supply the dorsum of the neck and
trunk (back) pg 81
The Big Picture
Just lateral to intervertebral foramen, each spinal nerve then splits in 2
Dorsal Rami Ventral Rami
Contain BOTH Sensory and Motor fibers!!
pg 68
CNSBrain
Spinal cord
PNSCranial nerves and spinal nerves
Sensory (afferent)division
Motor (efferent)division
Somatic sensory
General: Touch, pain, pressure, vibration
Special: hearing, equilibrium, vision, smell
Visceral sensory
General: Stretch, pain, temperature, nausea, hunger
Special: Taste
Somatic motor
General: Motor innervation of all skeletal muscles
Visceral motor
General: Motor innervation of smooth muscle, cardiac muscle, and glands; = ANS
Parasympathetic division
Sympathetic division
Autonomic Nervous System = Visceral Motor
Autonomic Nervous System
Visceral Motor Function Not easily controlled by will
Get nervous and sweat Innervate smooth muscle, cardiac muscle,
glands Regulate visceral function
Heart rate, blood pressure, digestion, urination Has 2 divisions:
Parasympathetic Sympathetic
Autonomic Nervous System
Parasympathetic “rest and digest” Enables body to
unwind and calm down Most active when body
at rest Routine maintenance
functions Craniosacral division
Fibers emerge from brain and sacral spinal cord
Sympathetic “fight or flight” Mobilizes the body
during extreme situations
Becomes active when extra metabolic effort needed
Thoracolumbar division
Fibers arise from thoracic and lumbar parts of spinal cord