Overview of the Nervous System and Spinal Nerves Flashcards Preview

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Flashcards in Overview of the Nervous System and Spinal Nerves Deck (94):
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Comprised of the neuronal cell bodies, nerve fibers, and connective tissues of the brain and spinal cord

Central nervous system (CNS)

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Initiates, regulates, and coordinates body functions

CNS

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The CNS communicates with other functional components of the body via the

Peripheral nervous system (PNS)

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Collections of neuronal cell bodies within the CNS are called

Nuclei

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The nerve fibers of the CNS are commonly arranged into discreet bundles called

Tracts

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Comprised of the neuronal cell bodies, nerve fibers and connective tissues that lie outside the CNS

-conveys information between CNS and peripheral structures

Peripheral Nervous System (PNS)

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Collections of neuronal cell bodies outside of the CNS are referred to as

Ganglia

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Comprised of peripheral nervous tissue responsible for
carrying signals to and from skeletal muscles, tendons,
joints and skin

Somatic Nervous System

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Conveys sensations of pain, temperature, tough, and proprioception from the periphery to the CNS

Somatic PNS

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The cell bodies of lower somatic motor neurons are located in the

Ventral horn of spinal cord

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The cell bodies of somatic sensory neurons are located in

Dorsal root (spinal) and cranial nerve ganglia

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The internal organs in the main cavities of the body, especially those in the abdomen, e.g., the intestines.

Viscera

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Comprised of peripheral nervous tissue responsible for
carrying signals to and from the viscera.

-conveys visceral sensations such as distension

Autonomic PNS

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The Autonomic PNS is comprised of

1.) Sympathetic nervous system
2.) Parasympathetic nervous system

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Elicits the so-called "fight or flight" response, which includes pupilary dilation, increased heart rate, blood pressure, and sweating

Sympathetic nervous system

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Controls digestive functions, slows the heart rate, and constricts the pupils

Parasympathetic nervous system

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Both utilize two motor neurons in the peripheral path to innervate smooth and cardiac muscle

Sympathetic and parasympathetic nervous systems

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The anatomic unit of the nervous system

-consists of a cell body, dendrite(s), and an axon

Neuron

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Microscopically, neurons can be classified as being

-based on the number of processes associated with their cell body

Multipolar, bipolar, or unipolar

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Functionally, neurons are classified as being either

Motor (efferent) or Sensory (afferent)

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These neurons are multipolar and carry information away from the CNS

-cell bodies are located in the nuclei, within the ventral horn of spinal cord

Motor (efferent) neurons

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These neurons are unipolar and carry information towars the CNS

-cell bodies are clustered in ganglia located outside CNS

Sensory (afferent) Neurons

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Ganglia associated with spinal nerves are called

Dorsal root ganglia (spinal ganglia)

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Lies within the vertebral canal extending from the foramen magnum to the level of the intervertebral disc between L1/L2 vertebra

Spinal Cord

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Surrounded by three meningeal layers: dura mater (outermost), arachnoid mater (intermediate), and pia mater (innermost) and bathed in cerebrospinal fluid (CSF) that fills the subarachnoid space

Spinal cord

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The spinal cord consists of

White and grey matter

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Bundles of myelinated axons arranged in discreet fiber tracts

White matter

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Arranged into three major horns: ventral (motor), dorsal (sensory), and lateral (autonomic motor)

Grey matter

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Attach to the spinal cord via ventral (motor) and dorsal
(sensory) roots and functionally divide it into 31 spinal cord segments

Spinal nerves (31 pairs)

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There are 31 pairs of spinal nerves, which comprises

8 Cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

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Spinal nerves exit the vertebral canal through intervertebral foramen. Where do the following exit?

1.) Spinal nerves C1-C7
2.) Spinal nerve C8
3.) Thoracic, lumbar, and sacral nerves

1.) Above the vertebrate (I.e. C3 exits above C3 between C2 andC3)
2.) Below C7
3.) Below their corresponding vertebra

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Spinal nerves exit the vertebral canal through

Intervertebral foramen

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Each spinal nerve is attached to the spinal cord via a

1.) Ventral (motor) root
and a
2.) Dorsal (sensory) root

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The ventral root carries only motor nerve fibers and the dorsal root carries only sensory nerve fibers. these roots merge to form the

Mixed (motor and sensory) spinal nerve

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The spinal nerve divides into two, forming a

-also mixed nerves

Ventral ramus and dorsal ramus

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What three things do dorsal rami innervate?

1.) Skin of back
2.) True back muscles
3.) Zygapophyseal joints

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Innervate the remainder of the skin and skeletal muscles of the neck, trunk, and limbs

Ventral rami

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The skin of the neck, body wall and limbs is divided up
into segments or slices called

Dermatomes (skin slice)

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Each dermatome is innervated by the

Dorsal or ventral rami of spinal nerves

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Dermatome segments overlap eachother such that innervation of the ventral T10 dermatomal segment is supplied in part by

T9 and T11 ventral rami

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Thus, complete anesthesia of the T10 dermatomal segment would require knocking out the

T9,T10, and T11 ventral rami

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The portion of the PNS responsible for monitoring and regulating visceral functions

Autonomic Nervous System

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Primarily responsible for motor innervation of smooth muscle lining blood vessels, cardiac muscle and sweat glands and sensory innervation of viscera

Sympathetic ANS

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Primarily responsible for motor innervation of smooth muscle lining digestive tract, cardiac muscle and salivary glands and sensory innervation of viscera

Parasympathetic ANS

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Distributed with spinal nerves and blood vessels

Sympathetic nerve fibers

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Distributed with cranial nerves and pelvic autonomic nerves

Parasympathetic nerve fibers

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Both multipolar neurons, which carry signals away from the CNS

Somatic and visceral motor neurons

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Innervates skeletal muscle and takes a 1 motor neuron pathway from CNS

Somatic motor

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Innervate smooth muscle, modify cardiac muscle and glands, and takes a 2 motor neuron pathway from CNS

Visceral motor

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A single neuron pathway from CNS to skeletal muscle. Cell bodies are multipolar and located in the ventral (motor) horn of the spinal cord

Somatic Motor (efferent)

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For visceral motors, cell bodies of the first motor neuron (preganglionic) are located in the

CNS

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For visceral motors, cell bodies of the second motor neuron (post ganglionic) are located in the

Ganglia in PNS

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Preganglionic neurons innervate ONLY

Post ganglionic neurons (directly innervates visceral structures)

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Sympathetic and parasympathetic motor innervation of smooth muscle, cardiac muscle and glands both
require a two neuron pathway with the first neuron located in the CNS and the second neuron in the

PNS

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Where are the preganglionic bodies of sympathetic motors located?

-referred to as thoracolumbar outflow

Lateral horn of T1-L2

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Where are the postganglionic cell bodies of sympathetic motors located?

Paravertebral and prevertebral ganglia

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Where are the preganglionic bodies of parasympathetic motors located?

-craniosacral outflow

Brainstem nuclei and lateral horn of spinal cord segments S2-S4

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Where are the postganglionic cell bodies of parasympathetic motors located?

4 discrete ganglia of the head and enteric ganglia of the gut

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Which has a more limited distribution, the parasympathetic or sympathetic system?

Parasympathetic

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Does not innervate smooth muscle or glands associated with somatic structures and is therefore not distributed to the trunk or limbs

Parasympathetic system

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Distributed throughout the entire body

Sympathetic neurons

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Before being distributed, all preganglionic sympathetic fibers enter paravertebral ganglia from T1-L2 via

White rami communicans

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The location of sympathetic preganglionic cell bodies found only from T1-L2 spinal cord segments

Lateral horn

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Carries preganglionic sympathetic motor axons to spinal nerve

-also carries somatic motor axons

Ventral root

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All carry somatic motor axons, somatic sensory fibers, and postganglionic sympathetic axons

Spinal nerves

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Carry all of those fibers plus visceral sensory and
preganglionic sympathetic axons

Spinal nerves from T1-L2

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Carries pre- and postganglionic sympathetic axons

-Carries somatic motor and sensory fibers and visceral sensory fibers

Ventral Ramus

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Connects ventral rami of spinal nerves T1-L2 with paravertebral ganglia, and carries preganglionic sympathetic axons

White ramus communicans

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Connects ventral rami of all spinal nerves with paravertebral ganglia, and carries postganglionic sympathetic axons that are distributed to somatic structures

Gray Ramus Communicans

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Sympathetic chain of ganglia located alongside the vertebral column

-contain postganglionic cell bodies

Paravertebral ganglia

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Connects paravertebral and prevertebral ganglia and carries preganglionic sympathetic axons

-also carries visceral sensory fibers

Splanchnic Nerve

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Contain postganglionic cell bodies whose axons are distributed to abdominopelvic viscera

Prevertebral ganglia

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Spinal nerves T1-L2 provide innervation primarily to the

Trunk

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The blood vessels and sweat glands associated with the trunk are innervated by

-travel in the rami of T1-L2 spinal nerves

Postganglionic sympathetic nerve fibers

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Provide innervation to the upper limb

Spinal nerves C5-T1

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Provide innervation to the lower limb

L2-S4

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The blood vessels and sweat glands associated with the limbs are innervated by postganglionic sympathetic nerve fibers that travel in the

Rami of the spinal nerves

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The upper and lower limb spinal nerves (besides T1 and L2) do not have

Preganglionic cell bodies or white rami communicates

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The lack of white rami communicates means that there is no direct entry to the

Paravertebral ganglia

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Neurons that convey somatic sensations are anatomically identical to those neurons that convey visceral sensations. Both are unipolar neurons with cell bodies located in a

Ganglion

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Innervates skin, muscle, and joints and conveys pain, temperature, touch, and proprioception

Somatic sensory neurons

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What is the location of the cell bodies of somatic sensory neurons?

Dorsal root ganglia from C2-Co

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The somatic sensory neurons take the same pathway as the motor pathway up to the spinal nerve. Then it follows the

Dorsal root to the dorsal horn

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Innervates viscera, glands, and blood vessels and conveys distension, nausea, and hunger

Visceral sensory neurons

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What is the location of the cell bodies of visceral sensory neurons

Dorsal root ganglia from T1-L2

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Visceral sensory neurons follow the same pathway as the motor pathway up till the spinal nerve. Then they follow the dorsal root to the

Dorsal horn

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How many neurons do the following require?
1.) Somatic and visceral motor pathway
2.) Somatic and visceral sensory pathway

1.) 2
2.) 1

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Somatic sensory and visceral sensory are both part of the

Autonomic Sensory (afferent) innervation

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Convey some pain, but are mostly involved with visceral reflexes such as monitoring blood pressure

Parasympathetic afferent fibers

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Travel in cranial nerves and pelvic splanchnic nerves along with visceral efferent fibers

Parasympathetic afferent fibers

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Parasympathetic afferent cell bodies are located in the cranial nerve sensory ganglia and dorsal root ganglia of spinal nerves

S2-S4

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Go from a stimulus back to the spinal cord

Afferent Nerve

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Go from the spinal cord to a body part

Efferent Nerve

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Occurs because visceral afferent fibers synapse on the same neurons in the dorsal horn of spinal cord segments T1-L2 as the somatic afferent fibers

Referred pain

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