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What are the funtions of the nervous system?
- 1. enables the body to react to changes in its external and internal environments via collection of information and eliciting the appropriate response (homeostasis)
- 2.Transduce (convert) energy into signals usable by the central nervous system- perception
- 3.Transfer information rapidly over long distances- sensory and motor functions
- 4.Store ( and process) information- learning & memory
- 5. Release neurotransmitters (or signals) that act on the nervous system- emotions
General definition of the nervous system?
a network of specialized cells including neurons and neuroglia
Nerve cells that are structural and functional units of the nervous system; electrically excitable cells that transmit and process information; neurons are core components of the brain, spinal cord, and peripheral nerves
What are the components of a neuron?
- cell body
- axon terminal
What are dendrites?
cellualr extensions that recive impulses and conducts them to the neuron cell body (or soma)
whats another name for the neuron cell body?
Define cell body (soma).
central part of the neuron that consists of the nucleus of the cell; where protein synthesis occurs
nerve fiber responsible for carrying nerve impulses away from the cell body to another cell (neuron or end organ)
Define axon terminal.
contains synapses, or specialized structures where neurotransmitters are released to communicate with another cell
How are neurons classified ?
- 1. Sensory (Afferent)
- 2. Motor (Efferent)
Describe pseudounipolar (or unipolar) sensory neurons.
composed of one dendrite (peripgeral process), one axon (central process), and a cell body;
most sensory (or afferent) neurons are pesudounipolar neurons which mean they carry information (touch, pain, and temperature) to the central nervous system
What does "afferent" mean?
"To carry towards or bring to"
Describe multipolar motor neurons.
have multiple (two or more) dendrites and a single axon; most common type of neuron in the nervous system
-they carry information away from the CNS
What does "efferent" mean?
"to carry away or bring out"
What neurons control the skeletal nuscle and the autonomic nervous system?
multipolar motor neurons
Describe neuroglia (glial cells or glia).
cells that support, insulate, and nourish the neurons
- -5 times more abundant than neurons
- -non excitable cells that form a major component of nervous tissue
What are 5 times more abundant thatn neurons?
neuroglia (glial cells or glia)
What is an example of the functions of glial cells?
they minimize metabolic expensie while maintaing rapid nerve conduction, many neurons are insulated with sheaths of myelin or layers of lipid/protein substances around their axons
Myelin sheaths are formed by _____ including _____ and _____.
- 1. glial cells
- 2. oligodendrocytes
- 3.Schwann Cells
glial cells that produce myelin in CNS
Define Schwann cells.
glial cells that produce myelin in perioheral nervous system PNS
Describe CNS (Central Nervous System).
- -made of spinal cord and brain
- -integrates and coordinate incoming & outgoing neural signals
- -carry out higher mental functions (thinking and learning)
CNS imporant key words?
- -white mater
- -gray matter
collections of cell bodies in the central nervous system
- bunde of nerve fibers (axons) connecting nuecli
- (also called fiber bundles, columns,pathways)
Define white matter.
where axons form nundles within the CNS
Describe gray matter.
where cell bodies (nuclei) congregate together in the CNS
A cross section of the spinal cord reveals what?
-its in an H shape
Where do the cell bodies of the multipolar motor neurons reside within? And what do they do?
-they reside within the anterior gray horns of the spinal cord
- they convey motor (efferent) information to the body
What is the PNS composed of?
composed of nerves and ganglia
What do nerves consist of?
- 1. bundles of nerve fibers (axons) outside the central nervous system
- 2. the connective tissue (endoneurium, perinuerium, and epineurium) to bind the nerve fibers
- 3.the blood vessels ( vasa nervorum) that supply the nerves
Cranial nerves vs. spinal nerves are different by?
how they exit the bony encasement of CNS
how do cranial nerves exit the cranial cavity?
via openings (foramina) in cranium (skull)
Describe cranial nerves.
- -12 pairs of cranial nerves
- -identified by bame, Roman numeral, or both
- -all (but one) of the cranial nerves arise from brain (exception: accessory)
- -cranial nerves can be purely sensory, purely motor, or mixed
Describe spinal nerves.
- -identified by a latter (region) and a number (first cervical nerve=c1)
- -arise from the spinal cord
- -31 pairs= 8 cervical, 12 thoraic, 5 lumbar, 5 sacral, 1 coccygeal
How do spinal nerves exit the bony encasement of the CNS?
exit from the vertebral column (spine)
The density of nerve supplt varies CONSIDERABLY!! However, all body tissues are supplied with nerves of some kind!!
Motor (efferent nerves) innervate what?
multipolar neurons innervate muscle cells (which contact and shorten) or glands (which secrete)
What do sensory or afferent nerves do?
pseudounipolar neruons detect changes in the internal and external environment and infrom the CNS of the changes
-cell bodies of sensory nerusons are located in the spinal ganglia in spinal nerves or sensory ganglia of cranial nerves
NOTE: Nerves are NOT purely sensory or motor!!!
What are the 2 destinations of contained fibers?
- 1. Somatic (or parietal)
- 2. Visceral (or splanchnic)
Several different types of nerve fibers can be carried within one nerve, but then divide into different categories.
Name these categories.
- 1. somatic motor
- 2. visceral motor
- 3. general sensory
- 4. visceral sensory
Describe somatic motor.
- innervate skeletal muscle (voluntary)
- -one neuron from CNS to viscera
- -somatic= related to body wall
Describe visceral motor.
- innervate smooth (involutary) muscle, cardiac muscle, and glands
- -2 neurons (presynaptic and post synaptic) conduct impulses from the CNS to viscera
- -visceral motor neurons are the autonomic nervous system
- -visceral= related to the body organs
Describe general sensory.
transmit sensations ( fine touch, pain, temperature, proprioception, etc) from the body to the CNS
Describe visceral sensory.
transmit visceral sensations, both conscious (pain) and unsconscious (reflexive)
collection of nerve cell bodies outside the CNS (or within the PNS)
-classified as motor or sensory ganglia
Describe sensory ganglia.
a collection of cell bodies of sensory (afferent) neurons, which forms a visisble swelling in the course of a peripheral nerve
Name 2 of the sensory ganglia.
- 1. spinal ganglia=ganglia of the spinal cord
- 2. cranial nerve ganglia= ganglia associated with cranial nerves
Describe autonomic ganglia.
ganglia associated with motor (or efferent) nerves of the autonomic nervous system (ANS)
-the sympahteic division of the ANS includes ganglia of the sympathetic trunk and prevertbral ganglia
where do the prevertebral ganglia lie?
lie anterior to the vertebral column
what does the parasympathetic division of the ANS have which are located within or close to the organ innervated?
name the 2 functions of the nervous system.
-SNS Somatic Nervous System and ANS Autonomic Nervous System
Describe the SNS.
- voluntary nervous system
- -general sensory fibers carry pain from the skin and joints and somatic motor fibers supply skeletal muscle
-SNS is under your conscious control
Which nervous system is under your conscious control?
Describe the ANS.
- involuntary/viscera; nervous system
- -visceral motor that innervate smooth & cardiac muscle, glands, and the internal organs in the body cavities
-is purely motor or efferent system****
What does the vertebral column do?
serves to form axis of the body and provide a proctective bony covering of the spinal cord.
The back region contains many layers of muscles that can connect to?
upper limb or vertebral column
Whats another term for the vertebral column?
The vertebral column extends from the cranium to the ?
The vertebral column protects what?
the spinal cord and spinal nerves
Describe some of the things the vertebral columnn does.
- -supports the weight of the body superior to the pelvis
- -prvides a pivot for the head
- -provides rigid and felxible axis for body
- -has roles in posture and locomotion
- -formed by 5 reguons of vertebrae named by the corresponding body reguons where they are located: cervical, thoracic, lumbat, sacral, and coccygeal
how many vertrbrae total?
Out of the vertebrae name the parts and how many?
5 sacral segments (fused)
4 coccygeal semgents (fused)
What are the features of a typical vertebrae:
weight bearing portion of vertebra
What are the Feature of a typical vertebra:
consists of a pair of pedicles and a pair of laminae that surroind the vertrebral foramen where the spinal cord passes through
What are the features of a typical vertebrae:
one on posterior portion and site for muscle attachments
What are the features of a typical vertebra:
one on each side and sites for muscle attachments
What are the features of a typical vertebrae:
superior and inferior articular processes
have smooth facets where adjacent vertebrae form joints'
**between the vertebral notches of adjacent vertrbrae form INTERVERTEBRAL FORAMINA and this is where SPINAL NERVES emerge and divide into POSTERIOR and ANTERIOR rami
What are the 2 main types the muscles in the back are divided into?
extrinisic muscles and intrinisc muscles
Extrensic muscles have two general divisions. name them and describe them.
1. Superficial Shoulder Muscles= conect the back to the upper limbs
- 2. Accessory Respiratory Muscles= connect to ribs
- **Innervated by ventral primary rami of spinal nerves: (Except, the trapezius m. is innervated by Cranial Nerve XI).
Describe Intrinsic muscles.
also called "ture" or "deep" back muscles.
**attached on and primary movers of vertrbral column
Innervated by dorsal (posterior) primary rami of spinal nerves.
Name some examples of extrensic back muscles.
- -latissimus dorsi
- -levator scapulae
- -rhomboid major and rhomboid minor
What is the triangle of auscultation?
- bounded by lateral border of trapezius middle
- -superior border of latissimus dosi m and medial border of scapula
- -mo muscles overlie intercostal space 6 here****
- -good location for stethoscope placement for listening to lung sounds
Name and describe the parts of the trapezius.
- 1. ascending= depress scapula
- 2. middle- retract scapula
- 3. descending= elevate scapula
**innervation by accessory nerve
Describe the latissimus dorsi.
- -adducts and medially roates humerus
- -innervation by ventral ramus (thoracodorsal nerve)
Descirbe the levator scapulae.
- -elevates scapula
- -innervation by verntral ramus (dorsal scapular nerve)
Describe the rhomboid major & rhomboid minor
- -retract scapula
- -innervation by ventral ramus
What are the acessory respiratory muscles?
they connect to ribs and primarily propioceptive
- serratus posterior superior
- serratus posterios inferior
- **both innervated by th ventral ramus (intercostal nerve)
Where do intinisc back muscles attach?
the vertrbral column
What are some examples of intrinisic back muscles?
- -erector spinae muscles
What is the most superficial of intrinsic back muscles?
Describe the splenius.
- -thick muscles
- -looks like a bandage, lateral back of neck
- -splenion is latin for bandage
- -when both sides act together, they extend the head & neck
- -when one side acts a;pme,they laterally flex and rotate the head toward the side of the contracting muscle
- -innervated by ventral (dorsal) ramus
What are the 3 intermediate muscles of the erector spinae?
Describe the erector spinae generally.
- -chief extensor of vertebral column
- -innervation by dorsal (posterior) ramus
- -iliocostalis= lateral
- -spinalis= medial
What are the deeper back muscles called?
Where are they attached and innervated?
- -attach to transvere and spinous processes and located between adjacent vertebrae to stabilize vertebral column.
- -innervatd by the posterior rami
Whats the only muscle in the deeper back muscles we dissect?
-What are the deeper back muscles?
-Semispinalis, multifidus, rotatores
Describe the semispinalis.
- -located on about half the vertebral column deep to the splenius m
- -greater occipital nerve (cutaneous branch of dorsal ramus C2) penetrates this muscle to provide sensory innervation to the back of the head
smooth articular surface on vertrbrae.
anither name for "anterior"
Another name for "posterior"
first braches from the spinal nerves
rami** is the singular form
Vertebra is singular, so whats plural?
Vertebrae is plural
an opening or hole that structure transverse through
Name the 2 skeletons of the body.
- 1. axial skeleton
- 2. appendicular skeleton
How is the axial skeleton formed?
formed by articulated bones
Name the parts of the axial skeleton.
- -vertebral column
Name the parts of the appendicular skeleton.
What is another name for the vertebral column?
Describe the spine.
where does it extend?
- -extends from the skull to the tip of the coccyx
- -forms the main part of the axial skeleton
- -fucntions include: maintaing posture, support body weight and protection of spindal cord and spinal nerves
- -consists of 33 bones (vertebrae), intervertebral (IV) discs connected by joints and ligaments that form the "Axis" of the axial skeleton
What are the functions of the spine?
- -maintaing posture
- -support body wieght
- -protection of spinal cords and spinal nerves
Name the 5 regions of the vertebral column.
- 1. cervical
How many cervical vertebrae are there?
- 7 bones (C1-C7)
- -cervical vertebrae are small vertebral bodies and have a transverse foramen ( for vertebral artery)
- Atypical C1 (Atlas)
- -has no body or spinous process instead it has a posterior and anterior arch with tubercles and foramen for the dens
-Dens-projects uo through foramen for the dens (c1) allowing head to rotate
it is the VERTEBRAL PROMINENS, which is evident when the neck is flexed and you can see a palpable landmark
Describe the thoracic vertebrae.
- -12 bones (T1-T12)
- -slightly larger
- -heart shaped vertebral bodies than cervical region
- -facets for articulation with the ribs
- -long spinous process that overlaps the vertebra below for additional protection of the spinal cord
Describe the lumbar vertebrae.
- -5 bones
- -large, kidney shaped bodies
- -triangular vertebral canal
- -large and slender transverse processes
- -short & sturdy spinours processes
Describe the sacrum.
- -5 fused bones
- -provides strength & stability to pelvis
Describe the coccyx.
- -4 fused bones (sometimes less)
- -development of these vertebrae form a break line bone that articulates with the sacrum
- -provides for muscle attachment and support of certain structures
How many vertebrae are there total?
Curvatures of the Vertebral Column:
fetus= is "C" shaped or cuved due to the embryo folding, fetal position
adult= four cuvatures
What are the four curvutures of an adult for the vertebral column for?
- - maintain balance
- -. increase strength for weight bearing
- -without curvatures the body weight on vertebral column would be 10 times greater
For the adult curvurtures of the vertebral column was are the primary curvutures (2) and secondary curvutures (2)?
- -concave anteriorly
- -develop during fetal life & persist
- -thoracic & sacral curvutures
- -concave posteriorly
- -develop later in life
- -cervical= develop during infancy, attain head control in space, head erect
- -lumbar= develop during infancy, sitting, erect when standing & walking
Name 3 abnormal curvutes of the vertebral column.
- -exaggerated thoracic curvuture
- -called "humpback" or "hunchback"
- -result of erosion of the anterior part of one or more vertebra osteoporosis
- -exaggerated lumbar or cervical curvuture
- -called "hollowback" or "swayback"
- -caused by weakened trunk musculature
- -abnormal lateral curvature
- -called crooked or curved back
- -caused by asymmetrical weakness of the intrinisc back muscles, failute of vertebra to develop
What is the function of intervertrebral disks?
to resist displacement of vertebral bodies while allowing movement on one another and acts a as a shock absorber
Describe intervertebral disks.
- -connect articulating surface of adjacent body vertebrae
- -second component of vertebral column
- -designerd for weight bearing and strength
- -thickest in lumbar region > thoracic > cervical
What are the 2 components of IV disks?
- 1. anulus fibrosus
- 2. nucelus pulposus
Describe annulus fibrosus.
- -outer fibrous ring
- -consisting of concentric lamellae of fibrocartilage forming the outer region of the IV discs
- -insert into the epiphysal rims of the vertebral bodies
- -posterior portion is thin and predisposed to rupture of the ring
Describe nucleus pulposus.
- -inner portion
- -central core of the IV disk
- -composed of gelatinous matrix embedded in collagen
- -water content is 85%
- -water content decreases with age therefore you get shorter as you age
What are the 3 ligaments of the vertebral column?
- 1. anterior longitudinal ligament
- 2. posterior longitudinal ligament
- 3. ligamentum flavum
Describe the anterior longitudinal ligament.
- -covers the anterolateral aspects of the vertebral bodies & IV discs
- -limits extension
Describe the posterior longitudinal ligament.
- -limits flexion
- -naroower ligament that runs within the spinal canal along the posterior aspects of the vertebral bodies
Describe the ligamentum flavum.
- -joins together the lamina of adjacent vertebral arches
- -resist seperation of vertebral lamina
Describe the spinal cord.
- -part of the CNS
- -contuniatuon of the medulla oblongata of the brain
- -accessed via a laminectomy (cutting through the laminae of vertebral arch)
- -in adults extends to L1 or L2
Describe the conus medullaris.
- -tapering inferior end of spinal cord
- -cone ends at L2
- -thus, spinal cord occurpies superior 2/3 or vertebral canal
What are the 2 enlargements?
- 1. cervical enlargement
- 2.lumbosacral enlargement
Describe the cervical enlargement.
- -widening of the spinal cord from c4- t1
- -due to innervation of the upper limb via the brachial plexus
Describe the lumbosacral (lumbar) enlargement.
- -widening of the spinal cord from T11-L1
- -due to innervation of the lower limb via the lumbosacral plexus
Describe cauda equina.
- -called "horse's tail"
- -loose collection of spinal nerve arising from the lumbosacral enlargement and conus medullaris
- -entends from inferior end of spinal cord
Describe Filum terminale.
- -arises from tip of the conus medullaris and inserts in the coccyx bone
- -anchors the inferior end of the spinal cord and spinal meninges
- -contunuation of the pia mater
What are the 3 layers of the spinal meninges?
Pia, arachnoid, & Dura mater
What are the functipns of the spinal meninges:
- -protects the spinal cord
- -serve as supporting framework for vessels
- -encloses the subarachnoid space, where blood vessels and cerebrospinal fluid CSF reside
What are the layers of the spinal cord made of?
collagen and elastic fibers
Describe the dura mater.
- -outermost layer
- -known as the "tough mother"
- -ends at S2 level
- -forms a long dural sac
- -covers dorsal and ventral roots
Describe the arachnoid mater.
- -middle layer
- -thin delicate an avascular
- -spider web like
Describe the pia mater.
- -innermost later
- -delicate, highly vasuclar layer of connective tissue
- -directly adheres to spinal cord and brain
- -inferior to conus medullaris, the pia contunes as the filum terminale
What is the arachnoid trabeculae?
a network of CT connecting arachnoid to pia mater
The three layrs of spinal meninges create spaces. Name 3 of the spaces.
- -epidural space
- -subdural space
- -subarachnoid space
Describe the epidural space.
- -between the vertebral canal and dura mater
- -contains fat and loose connective tissue
- -internal vertebral venous plexuses are located
Describe the subdural space.
- -NOT A REAL SPACE
- -between the dura and subarachnoid mater
- -can become a REal spae, due to pathological conditions (ex: bleeding into this layer)
Describe the subarachnoid space.
- -between the arachnoid and pia mater
- -contains CSF (cerebrospinal fluid)= clear colorless fluid which bathes the brain tissue to help protect it
- -contains blood vessels
Specializations of the spinal meninges:
describe the Spinal Dural Sac.
- -formed by the dura
- -long tubular shealth within the vertebral canal
- -the spinal cord is suspended in the dural sac
- -superiorly adheres to foramen magnum of cranium
- -inferiorly anchored by filum terminale of coccyx
What is the spinal cord in the dural sac suspended by?
How many saw like tooth like extensions are there of the pia mater?
What does cistern do in lumbar cistern?
dilations in the subarachnoid space
The lumbar cistern extens infereriorly how?
from L2 (where the spinal cord ends) to S2 (dural sac ends)
How is the lumbar cistern named?
according to location
What is so special about the lumbar cistern?
it is a great place to sample CSF or administer drugs
The lumbar cistern communicates with?
the brain CSF
What are spinal artieries?
three artieries can supply only the superior part of the spinal cord, so additional artieries are needed and are branches of the vertebral a.
Describe the anterior spinal artery 1.
1- artery located in the midline that supplies the anterior of the spinal cord
Describe the posterior spinal artery.
2 laterally placed arteries which supply the posteror of the spinal cord
What is the segmental medullary arteries?
derived from spinal branches of nearby arteries and supply additional regions of the spinal cord
What are the radicular arteries?
-most of these arteries do not supply the spinal cord, some do supply superficial (peripheral) parts of spinal cord, mostly supply roots of spinal nerves
Anterior radicular artery follows?
follow the anterior roots of the spinal nerves
Posterior radicular artery?
follow the posterior roots of the spinal nerves