Spinal Cord
Peripheral Nervous System (PNS) - Spinal Nerves
+ 8 Pairs of Cervical Nerves + 12 Pairs Thoracic Nerves + 5 Pairs Lumbar Nerves + 5 Pairs Sacral Nerves + 1 Pair Coccygeal Nerves
Conus Medullaris, Cauda Equina and Film Terminale from Superior to Inferior
+ Conus Medullaris (Superior) + Cauda Equina (Middle) + Filum Terminale (Inferior)
Lumbar Cord Lesion
+ Cranial Nerves and Motor System: Flaccid Paralysis of Lower Extremities + Reflexes: Hypo- Reflexia, of Lower Extremities + Sensation: Loss Of Sensation Below The Level Of The Lesion
Lower Cervical Cord Lesion
+ Cranial Nerves and Motor System: Flaccid Paralysis of Upper Limbs and Spastic Paralysis of Lower Limbs + Reflexes: Hyporeflexia of Upper Limbs and Hyperreflexia of Lower Limbs + Sensation: Loss Of Sensation Below The Level Of The Lesion
Thoracic Cord Lesion
+ Cranial Nerves and Motor System: Spastic Paraplegia + Reflexes: Hyper- Reflexia, Below Level Of The Lesion + Sensation: Loss Of Sensation Below The Level Of The Lesion
Upper Cervical Cord Lesion
+ Cranial Nerves and Motor System: Spastic Quadriplegia + Reflexes: Hyperreflexia + Sensation: Loss of Sensation below the Level of the Lesion
Nerves Strictly Responsible for Mixed Signal Transmission in the Spine?
+ Dorsal Primary Ramus + Ventral Primary Ramus + Spinal Nerve
Nerves Strictly Responsible for Sensory Input Into the Spine?
+ Dorsal Root + Dorsal Root Ganglion
Spinal Cord Meninges
+ Epidural (Fat) + Dura Mater + Subdural Space + Arachnoid Space + Subarachnoid Space + Pia Mater
Spinal Cord
+ Lies on the Vertebral Column + Extends from the Foramen Magnum to L1/L2
What are the 4 Extrapyramidal (Descending Motor) Tracts?
+ Reticulospinal Tracts + Rubrospinal Tracts + Tectospinal Tracts + Vestibulospinal Tracts
Somatosensory Cortex (Parietal Lobe) (Post Central Gyrus)
A brain area at the front of the parietal lobes that registers and processes body sensations + Located in the parietal lobe of the human cortex and is the primary somatosensory region of the human brain. This is the point-for-point correspondence of an area of the body to a specific point on the central nervous system. Typically, the area of the body corresponds to a point on the primary somatosensory cortex (postcentral gyrus). This cortex is typically represented as a sensory homunculus which orients the specific body parts and their respective locations upon the homunculus. Areas such as the appendages, digits, and face can draw their sensory locations upon the somatosensory cortex. Areas that are finely controlled, such as the digits, have larger portions of the somatosensory cortex, whereas areas that are coarsely controlled, such as the trunk, have smaller portions. Areas such as the viscera do not have sensory locations on the postcentral gyrus.
Fasciculus Gracilis
A division of the Dorsal Columns System specifically dealing with the LOWER EXTREMITY + Lower 1/2 of the Body
Fasciculus Cuneatus
A division of the Dorsal Columns System specifically dealing with the UPPER EXTREMITY + Upper 1/2 of the Body
Foramen Magnum
A large opening at the base of the skull through which the brain connects to the spinal cord.
Inferior Cerebellar Peduncle (ICP)
A major (white matter) neural tract in the cerebellum and is involved in coordination of movement and proprioception; therefore, ICP injury can be accompanied by poor coordination of movement, including ataxia
Homunculus
A maplike representation of regions of the body in the brain
Neuron
A nerve cell; the basic building block of the nervous system
Gracile Tubercle
A nucleus that relays sensory information from the lower body
Cuneate Tubercle
A nucleus that relays sensory information from the upper body
Subarachnoid Space
A space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid
Posterior (Dorsal) Horn
Posterior projections of the gray matter. Consists entirely of inter-neurons receiving somatic and visceral input from Sensory Neurons + Receive sensory information that enters the spinal cord via the dorsal roots of the spinal nerves
Receives Information from the Labyrinth System & Cerebellum & Activates Extensor Motor Neurons concerned with Maintenance of Anti-Gravity Posture
Vestibulospinal Tract
The Shoulder is innervated by what nerve?
C5
What is the Total Number of Spinal Nerves?
31 Pairs
There are ______ pairs of spinal nerves, but only ______vertebral levels?
31;30
Neuroepithelial Cells divide and differentiate into what 3 Layers?
1. Neuroepithelial Layer 2. Mantle Layer 3. Marginal Layer
How long is the Spinal Cord in Adults?
18 inches
Neuroepithelium
A type of epithelium that is specialized to perform a particular sensory function; these provide the senses + During embryonic development, neuroepithelial cells function as neural stem cells: they renew themselves while undergoing interkinetic nuclear movements along the apico-basal axis during the cell cycle, and they produce postmitotic cells that function as newborn neurons.
C2-C7 Nerves exit ______________ the vertebra with the same number
Above
Sensory Neurons are
Afferent neurons of the PNS
Neural Tube
An embryonic structure with subdivisions that correspond to the future forebrain, midbrain, and hindbrain + Day 24
Spinal Cord Gray Matter
An essential type of tissue that plays a significant role in mental functions, memory, emotions and movement. It comprises 40% of our Brain and Spinal Cord and consists of neuronal cell bodies and their dendrites. The dendrites are short protrusions (like little fingers) that communicate with neurons close by in order to transmit signals, both Motor and Sensory. Gray Matter is comprised of 4 Key Components: + Posterior/Dorsal Horn (Sensory) + Anterior/Ventral Horn (Motor) + Later Horn (Autonomic) + Central Gray Commissure
What are the 2 Corticospinal Tracts?
Anterior Corticospinal Tract and Lateral Corticospinal Tract
Anterior (Ventral) Horn
Anterior projections of the gray matter that contain the cell bodies of somatic Motor Neurons and some interneurons + Contains the cell bodies of motor neurons that send axons via the ventral roots of the spinal nerves to terminate on striated muscles
Dermatomes
Area of skin innervated by cutaneous branches of single spinal nerve + Distribution of sensory innervation to the skin that is segmental
Anterior Spinothalamic Tract
Ascending tract (sensory pathways) that conveys Crude Touch
Lateral Spinothalamic Tract
Ascending tract (sensory pathways) that conveys sensations of Pain and Temperature
Dorsal Root Ganglion (DRG)
Associated with the dorsal horns; cell bodies of sensory neurons are located here; spawns from the Dorsal Root
Lumbar Puncture in Adults
At the L3-L4 Interval
Lumbar Puncture in Children
At the L4-L5 Interval
C1 Nerves Exit above _______________
Atlas (C1)
Spinal Nerve Development
Axons from both the dorsal and ventral roots merge together into a single spinal nerve + Neural Crest + Association Plate (Alar Plate) + Motor Plate (Basal Plate)
Marginal Layer of Neural Tube
Becomes nerve fibers via white matter of CNS
C8 Nerves exit ______________ vertebra C7 and subsequent spinal nerves exit ___________ the vertebra of the same number.
Below
Upper Motor Neurons (UMN) are in the......
Brain and Spinal Cord
Ventral Primary Ramus
Branch of a spinal nerve that innervates the skeletal, muscular, and cutaneous areas of the limbs and/or of the anterior and lateral trunk. + MIXED SIGNAL TRANSMISSION (Sensory and Motor)
The Hand is innervated by what 3 nerves?
C6, C7 and C8
Lumbar Puncture (LP) ("Spinal Tap")
CSF is withdrawn from between two lumbar vertebrae for analysis via Subarachnoid Space
Descending Tracts
Carry motor information down the spinal cord
Ascending Tracts
Carry sensory information up the spinal cord to the brain
Spinothalamic Tracts (Summary)
Charged with Crude Touch & Pressure and Pain & Temperature (From the Body). These Neuronal Tracts cross over the Cord at the level of the 1st Synapse. + 1st Order Neuron: Dorsal Root Ganglion (Inferior/Bottom) *Cross OVER Point + 2nd Order Neuron: Dorsal Horn + 3rd Order Neuron: Thalamus (Superior/Top)
Dorsal Column Tracts (Summary)
Charged with transmitting position, vibration, and touch information (From the body). These Neuronal Tracts cross over the cord at the Medulla Oblongata. + 1st Order Neuron: Dorsal Root Ganglion + 2nd Order Neuron: Medulla (Nucleus Cuneatus or Nucleus Gracilis) *Cross OVER Point + 3rd Order Neuron: VPL (Ventral Posterolateral) Nucleus of The Thalamus
Dorsal Spinocerebellar Tract
Communicates sensation of temperature, proprioception, and touch from lower body and legs, to ipsilateral cerebellum
Spinal Cord White Matter (General)
Composed of bundles of axons. These axons are coated with myelin, a mixture of proteins and lipids, that helps conduct nerve signals and protect the axons. White matter conducts, processes, and send nerve signals up and down the spinal cord via Ascending Tracts (Sensory) and Descending Tracts (Motor).
What is Visible on the Posterior (Dorsal) Medulla?
Comprised of the Inferior Cerebellar Peduncle, Floor of the 4th Ventricle, Cuneate Tubercle and the Gracile Tubercle
Vestibulospinal Tract
Comprised of two subtract systems - Medial and Lateral Vestibulospinal Tract - that are responsible for increasing antigravity muscle tone in response to the head being tilted to one side. Antigravity muscles are extensor muscles in the limbs
Dorsal Column System
Consists of LARGE DIAMETER FIBERS that transmit sensory information with GREAT SPEED and PRECISE LOCALIZATION. Has Two Tracts: + Fasciculus Gracilis (Lower 1/2 of the Body) + Fasciculus Cuneatus (Upper 1/2 of the Body)
Spinocerebellar Tracts
Consists of sensory fibers that transmit unconscious proprioceptive information to the cerebellum: also transmit some information on pain, crude touch and pressure + Dorsal Spinocerebellar Tract + Anterior Spinocerebellar Tract
Anterior Root Fibers of the Spinal Cord (Gray Matter)
Contain axons of motor neurons, which conduct nerve impulses from the CNS to effectors (muscles and glands) + MOTOR OUT
Mantle Layer of Neural Tube
Contains cell bodies that will become Gray matter
Posterior Root Fibers of the Spinal Cord (Gray Matter)
Contains the cell bodies of sensory neurons carrying signals to the spinal cord + SENSORY IN
Rubrospinal Tract
Control of muscle tone in flexor muscle groups (it is particularly important in the term newborn because of the flexor tone in the limbs) + It has an important role in the modulation of motor tone, causing flexors to contract and extensors to relax and vice versa. This function is associated with the rubrospinal tract because the red nucleus receives input fibers from reticular formation (the archaic core of those pathways connecting the spinal cord and the brain)
Spinocerebellar Tracts (Summary)
Convey information about muscle and tendon stretch to the cerebellum + 1st Order Neuron: Dorsal Root Ganglion + 2nd Order Neuron: Dorsal Horn
Modalities of Spinothalamic Tract
Crude Touch & Pressure, Pain & Temperature (From the Body)
Cauda Equina (Horse Tail) (Spinal Cord)
Nerves hanging down from the Conus Medullaris (Peripheral Nervous System)
Neuroepithelium Layer is in charge of?
Dividing Cells
Lateral Corticospinal Tract
Division of the Corticospinal Pathway that travels through Upper Motor Neurons in the Primary Somatomotor Cortex and controls Appendicular musculature + Fibers cross over to the opposite side of The CNS in the Pyramids of the Medulla + 80% of Corticospinal Fibers
Anterior Corticospinal Tract
Division of the Corticospinal Pathway that travels through the Lower Motor Neuron in the Ventral (Anterior) Horn of the Spinal Cord and controls Axial musculature. + Cross over occurs in the Spinal Cord at the Level of Synapse where Fibers pass through the Medullary Pyramids without Crossing Over + Has charged control of 20% of Corticospinal Fibers
Upper Motor Neuron Syndrome
Due to Brain Damage Between the Brain and Spinal Cord, however, Reflexes are intact (e.g., Stroke) + Weakness or Paralysis of specific movements (Extension of arms and flexion or legs) + NO Wasting of Muscles + Spasticity (Hypertonia) + Hyperreflexia (of Deep Tendon Reflexes)
Lower Motor Neuron Syndrome
Due to Brain Damage Between the Muscle and Spinal Cord, rendering Reflexes Absent (e.g., Poliomyelitis) + Weakness (Paresis) or Paralysis (Plegia) of individual muscles + Hypotonia and Wasting of Muscles + Hyporeflexia or Areflexia ( of Deep Tendon Reflexes
Motor Neurons are
Efferent Neurons of the PNS
Hyperreflexia
Exaggerated reflex response
Denticulate Ligament
Extensions of pia mater and holds spinal cord in place
Descending Motor Tracts are...?
Extrapyramidal Tracts
Filum Terminale
Fibrous extension of the pia mater; anchors the spinal cord to the coccyx
Modalities of the Corticospinal Tracts
Fine, Precise Motor Movement
Neural Plate
Flat group of cells present in prenatal development that becomes the brain and spinal cord + Day 18
Flaccid equals
Floppy
Functions and Pathway of Spinal Cord White Matter within Ascending Sensory Tracts
Function: Fine Touch, Pressure and Conscious Proprioception Pathway: Medulla Oblongata --> Thalamus --> S.S. Cortex + These are ASCENDING Sensory Tracts
Central Gray Commissure
Gray matter that connects the lateral areas of gray matter on either side of the spinal cord
Neural Groove
Groove resulting from further growth and thickening of the neural plate. + Day 20
Differential Growth of the Spinal Cord
Growth of spinal cord is at different rate than growth of vertebral column; generally cord becomes more superior; nerve fibers become longer + The caudal end of the adult spinal cord is situated at the level of the first or second lumbar vertebra. This is because, following the third month of fetal development, the vertebral column grows faster than the spinal cord. The lumbosacral nerve roots elongate and extend past the caudal end of the spinal cord to form what is known as the cauda equina. The caudal end of the spinal cord tapers off into the cone-shaped conus medullaris, which continues distally as the filum terminale. The filum terminale is a caudal prolongation of the spinal pia materthat courses along with the cauda equina to terminate on the dorsal surface of the coccyx. + At 8 Weeks: Ratio of Spinal Cord to Vertebral Column (1:1) + At 24 Weeks: Ratio of Spinal Cord to V. Column (1:2 or 1/2) + Newborn: Ratio of Spinal Cord to V. Column (1:3 or 1/3) + Adult: Ratio of Spinal Cord to V. Column (1:4 or 1/4)
Hypertonia (Spastic Paralysis)
Increased muscle activity causing fixed positions or increased tone of the involved extremities.
Changes in the cross-sectional shape of the spinal cord are mainly due to ____________________________ in the gray matter of the cervical and lumbar regions. These neurons are needed to innervate the upper and lower limbs.
Increased numbers of motor neurons
Conus Medullaris
Inferior (tip) end of spinal cord that usually rests somewhere along the Upper Lumbar of the Vertebral Canal (L1-L2)
The Foot is innervated by what 3 nerves?
L4, L5 and S1
Hypotonia (Flaccidity)
Loose, flexible; weak muscle tone that produces a floppy muscle effect to Active Range of Motion + Decreased Muscle Tone
Gray Matter develops from what Layer of Neurons?
Mantle Layer
White Matter develops from what Layer of Neurons?
Marginal Layer
What is the Most Common Form of Spina Bifida?
Meningomyelocele Spina Bifida Cystica
Spinal Nerve (CN XI)
Mixed nerves sending motor, sensory, and autonomic signals between the CNS and the body and they belong to the peripheral nervous system (PNS). Spinal nerves are essential for the control of body parts by the higher centres of the nervous system. + MIXED SIGNAL TRANSMISSION (Sensory and Motor)
Spina Bifida (Meningomyelocele)
Neural tissue with the meninges protrudes outside the body. This result in abnormal growth of the spinal cord and some degree of lower extremity dysfunction, often bowel and bladder control is impaired.
What gives rise to ALL Spinal Cord Neurons?
Neuroepithelium
Marginal Layer is in charge of?
Neuronal Processes
Mantle Layer is in charge of?
Neuronal and Glial Cell bodies
Corticobulbar Tract
Originating the the Precentral Gyrus of the Cerebral Cortex and is composed of the upper motor neurons of the cranial nerves. This tract is in charge of the face, tongue, jaw, head and neck which terminates on motor neurons within brainstem motor nuclei. Contrast this to the corticospinal tract were the cerebral cortexconnects to spinal motor neurons, and controls movement of the torso, upper and lower limbs. The Cranial Nerves under its helm is: + CN V (Trigeminal): muscles for mastication + CN VII (Facial): muscles of the face + CN XI (Spinal Accessory): sternocleidomastoid and trapezius + CN XII (Hypoglossal): muscles of the tongue
Pyramids of the Anterior (Ventral) Medulla
Paired white matter structures of the brainstem's medulla oblongata that contain motor fibers of the corticospinal and corticobulbartracts - known together as the pyramidal tracts. The lower limit of the pyramids is marked when the fibers cross (decussate)
Plegia
Paralysis
Basal Plate
Part of the neural tube that differentiates into Motor neurons
Alar Plate
Part of the neural tube that differentiates into Sensory neurons
Epidural
Pertaining to the layer upon (above) the dura mater
Example of Lower Motor Neuron (Syndrome) Lesion
Poliomyelitis
Tectospinal Tract
Receives information from the retina and cortical visual association areas. In response to visual stimuli, the tectospinal tract mediates reflex movements .It is able to orientate the head/trunk towards auditory stimulus (inferior colliculus) or visual stimuli (superior colliculus).
Hyporeflexia (Areflexia)
Reduced/absent reflexes
Floor of the 4th Ventricle
Referred to as the Rhomboid Fossa because of its shape. It is divisible into a right and left half by the posterior median sulcus, and into a superior and inferior triangle by the striae medullares. The upper triangular part is formed by the posterior surface of the pons.
Epidural Anesthesia
Regional anesthesia produced by injecting medication into the epidural space of the lumbar or sacral region of the spine
Pyramidal System (Corticospinal Tract System)
Responsible for voluntary, Fine, precise and Skilled, movements made by the body and includes all fibers originating in the Precentral Gyrus and projecting onto subcortical structures + When a voluntary movement is made, the signal is passed along from neuron to neuron along the pyramidal tract until it reaches the desired nerves. This transmission takes place in a fraction of a second, allowing people to respond in a way that may feel instantaneous. The level of control available through the pyramidal tract is extremely precise and highly detailed, allowing people to do everything from controlling the movement of the hands during brain surgery to running a marathon. Functionally, the Pyramidal tracts can be subdivided into two domains: 1. Corticospinal tracts - supplies the musculature of the body. 2. Corticobulbar tracts - supplies the musculature of the head and neck.
Reticulospinal Tract
Responsible primarily for locomotion (balance) and postural control through two subtracts: Medial Reticulospinal Tract (Pontine) and Lateral Reticulospinal tracts (Medullary) that both share interneurons with corticospinal tract on proximal limb and axial muscle motor neurons + Essential for maintaining the posture of the body. + Autonomically Controls: Heart Rate, Circulation, Breathing and Respiratory Rate
Receives Information from the Hypothalamus and Activates Motor Neurons Concerned with Reflex Activity, Muscle Tone, Breathing and Circulatory System
Reticulospinal Tract
Receives Information from the Cortex & Cerebellum & Activates Motor Neurons of Flexor Muscles
Rubrospinal Tract
The "Saddle Area" of the Spine, also known as the Caudal End or Perineum is innervated by what 3 Nerves?
S3, S4 and S5
Spinothalamic System
SMALL DIAMETER FIBERS that transmit sensory information at a SLOW SPEED and WITHOUT PRECISE LOCALIZATION Has Two Tracts: + Lateral Spinothalamic Tract (Pain & Temperature) + Anterior Spinothalamic Tract (Crude Touch)
Spastic equals
Scrunchy
General Sensory Pathways Terminate in the ______________________________________________.
Somatosensory Cortex
Subdural Space
Space between dura mater and arachnoid mater (potential space)
Lower Motor Neurons (LMN) are in the.....
Spinal Cord and Nerves
Example of Upper Motor Neuron (Syndrome) Lesion
Stroke
Function of Spinal Cord White Matter in Descending Motor Tracts (Extrapyramidal)
Subconscious Movements and Posture
Spinal Cord White Matter within Descending Motor Tracts (Extrapyramidal) is charged with what function?
Subconscious Movements and Posture
Dorsal Primary Ramus
Supplies deep back muscles and the skin on the dorsal surface of the trunk + MIXED SIGNAL TRANSMISSION (Sensory and Motor)
The Umbilicus is innervated by what nerve?
T10
The Nipple is innervated by what nerve?
T4
Receives Information from the Visual System and Activates Motor Neurons Reflex Response to Visual Stimuli
Tectospinal Tract
L1-L2
The Terminal End of the Spinal
Ventral Root
The basal branch of each spinal nerve; carries motor neurons + MOTOR NEURONS
Pia Mater
The delicate innermost membrane enveloping the brain and spinal cord.
Dura Mater
The thick, outermost layer of the meninges surrounds and protecting the brain and spinal cord
Lateral Horn
The lateral horn is a lateral projection of the gray matter and is only present in the thoracic region of the spinal cord. The lateral horn consists of neuron cell bodies of the Autonomic Nervous System (ANS). + Contain preganglionic visceral motor neurons that project to the sympathetic ganglia
Dorsal Root
The sensory branch of each spinal nerve (afferent); origination point.
Descending Pathways
The systems of neurons that bring motor information from the brain down to the appropriate spinal level. Signals travel along two neurons. + Pyramidal System (Corticospinal Tracts via Anterior & Lateral) + Reticulospinal Tracts + Rubrospinal + Tectospinal + Vestibulospinal
Ventral Spinocerebellar Tract
Transmits pain sense and proprioception from legs and lower trunk to the ipsilateral cerebellum
The Face is innervated by the ______________________
Trigeminal Nerve (CN V) that has 3 Divisions + Ophthalmic (V1) + Maxillary (V2) + Mandibular (V3)
Nerve that is Strictly Responsible for Motor Input Into the Spine?
Ventral Root
Paresis
Weakness (i.e., Partial Impairment)
Arachnoid Mater
Weblike middle layer of the three meninges