the peripheral nervous system. peripheral nervous system 31 pairs of spinal nerves 12 pairs of...
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The Peripheral Nervous The Peripheral Nervous System System
Peripheral Nervous SystemPeripheral Nervous System
31 pairs of spinal 31 pairs of spinal nerves nerves
12 pairs of cranial 12 pairs of cranial nervesnerves
All of the smaller All of the smaller nerves that branch nerves that branch from larger nervesfrom larger nerves
Afferent and Efferent PathwaysAfferent and Efferent Pathways
Afferent Pathways
Efferent Pathways
Spinal NervesSpinal Nerves
31 Pairs31 Pairs
Numbered according to the level of the vertebral Numbered according to the level of the vertebral column at which they emerge from the spinal column at which they emerge from the spinal cavity cavity
Lumbar, Sacral, and Coccygeal nerves descend Lumbar, Sacral, and Coccygeal nerves descend from their point of origin at the lower end of the from their point of origin at the lower end of the spinal cordspinal cord
Lower end of the cord is called the Lower end of the cord is called the cauda cauda equina, equina, which means “horses tail” in Latinwhich means “horses tail” in Latin
Structure of Spinal NervesStructure of Spinal Nerves
Mixed Nerves (contain Mixed Nerves (contain motor and sensory fibers)motor and sensory fibers)
Attach by means of two Attach by means of two short rootsshort roots
Dorsal rootDorsal root Has ganglion (cell bodies)Has ganglion (cell bodies) Carries sensory neruons Carries sensory neruons
Ventral rootVentral root Carries motor neuronsCarries motor neurons
Dorsal and Ventral RamiDorsal and Ventral Rami
Soon after each spinal nerve emerges from the Soon after each spinal nerve emerges from the spinal cavity, it forms several large branches, spinal cavity, it forms several large branches, each of which is called a ramus. each of which is called a ramus.
Dorsal Ramus Dorsal Ramus Supplies somatic motor and sensory fibers to serveral Supplies somatic motor and sensory fibers to serveral
smaller nervessmaller nerves
Ventral Ramus Ventral Ramus More complexMore complex
Rami of Spinal NervesRami of Spinal Nerves
Nerve PlexusesNerve Plexuses
Ventral rami of most spinal nerves Ventral rami of most spinal nerves subdivide to form complex networks called subdivide to form complex networks called plexuses.plexuses. Cervical plexus Cervical plexus Brachial plexus Brachial plexus Lumbar plexus Lumbar plexus Sacral plexusSacral plexus
Damage to one Damage to one spinal nerve does spinal nerve does not mean complete not mean complete loss of function in loss of function in any one region. any one region.
Dermatomes and Myotomes Dermatomes and Myotomes
Each skin surface Each skin surface area supplied by area supplied by sensory fibers of a sensory fibers of a given spinal nerve is given spinal nerve is called a dermatome.called a dermatome.
A myotome is skeletal A myotome is skeletal muscle or group of muscle or group of muscles that receives muscles that receives motor axons from a motor axons from a given spinal nerve.given spinal nerve.
Dermatome Distribution of Spinal Dermatome Distribution of Spinal NervesNerves
Myotomes and Body MovementMyotomes and Body Movement
Cranial Nerves Cranial Nerves 12 pairs 12 pairs
Connect to the undersurface of the brain Connect to the undersurface of the brain
Pass through small foramina (holes) in the cranial cavity Pass through small foramina (holes) in the cranial cavity and skulland skull
Identified by names and numbers Identified by names and numbers
3 Types3 Types Mixed Mixed Sensory Sensory Motor Motor
Divisions of the Divisions of the Peripheral Nervous Peripheral Nervous
System System
Somatic Motor Nervous System Somatic Motor Nervous System
All the voluntary motor pathways outside All the voluntary motor pathways outside the CNS (pathways to skeletal muscles)the CNS (pathways to skeletal muscles)
Single motor neuron whose axon stretches Single motor neuron whose axon stretches from the cell body in the CNS all the way from the cell body in the CNS all the way to the effectorto the effector
Stimulates effectors by means of the Stimulates effectors by means of the neurotransmitter acetylcholineneurotransmitter acetylcholine
Somatic Reflexes Somatic Reflexes
The action that results from a nerve impulse passing The action that results from a nerve impulse passing over a reflex arc is called a reflex.over a reflex arc is called a reflex.
Predictable response to a stimulus Predictable response to a stimulus
May or may not be consciousMay or may not be conscious
Somatic reflexes are contraction of skeletal muscleSomatic reflexes are contraction of skeletal muscle
Autonomic reflexes consist of contractions of smooth or Autonomic reflexes consist of contractions of smooth or cardiac muscle, or secretion by glandscardiac muscle, or secretion by glands
Used in the diagnosis of diseaseUsed in the diagnosis of disease
Knee Jerk ReflexKnee Jerk Reflex
Autonomic Nervous SystemAutonomic Nervous System
Regulates involuntary effectorsRegulates involuntary effectors
Major function of the ANS is to regulate Major function of the ANS is to regulate heartbeat, smooth muscle contraction, and heartbeat, smooth muscle contraction, and glandular secretion in ways to maintain glandular secretion in ways to maintain homeostasis. homeostasis.
Sympathetic and Parasympathetic Sympathetic and Parasympathetic DivisionsDivisions
Sympathetic and Parasympathetic have Sympathetic and Parasympathetic have separate pathwaysseparate pathways
Effectors may have dual innervation, that Effectors may have dual innervation, that is they have input from both types of is they have input from both types of pathwayspathways
Parasympathetic – “rest-and-repair”Parasympathetic – “rest-and-repair”Sympathetic – “fight-or-flight”Sympathetic – “fight-or-flight”
Autonomic Conduction PathsAutonomic Conduction Paths