Organisation Of The Nervous System 3 Flashcards
What is a spinal reflex?
It is a rapid, automatic nerve response triggered by specific stimuli. It is controlled by spinal cord alone, not the brain
The spinal cord is about
18 inches (45cm) long and 1/2 inch (14mm) wide
The spinal cord ends between
Vertebrae L1 and L2, the cord itself is not as long as the vertebral column
The bilateral symmetry of the spinal cord:
Grooves divide the spina cord into left and right
One of the grooves that divide the spinal cord is the posterior median sulcus which is
On the posterior side
The other groove that divides the spinal cord is the anterior median fissure which
Is a deeper groove on anterior side
Enlargements of the spinal cord are caused by
Amount of grey matter in segment and involvement with sensory and motor nerves of limbs
There are two types of enlargements of the spinal cord
Cervical enlargement and lumbar enlargement
The cervical enlargement supplies
Nerves to the shoulder and upper limbs
The lumbar enlargement provides
Innervation to structures of the pelvis and lower limbs
The distal end of the spinal cord is composed of
Conus medullaris
Filum terminale
Cauda equina
The conus medullaris is a
Thin, conical spinal cord below lumbar enlargement
The filum terminale is a
Thin thread of fibrous tissue at end of conus medullaris
The filum terminale attaches to
Coccygeal ligament
The cauda equina is
Nerve roots extending below conus medullaris
The spinal cord segments are based on
Vertebrae where spinal nerves originate
The positions of the spinal segment and vertebrae change
With age
Cervical nerves named for
Inferior vertebra
All other nerves named for
Superior vertebra
The roots of the spinal cord are
Two branches of spinal nerves
The two roots are the
Ventral root and the dorsal root
The ventral root
Contains axons of motor neurons
The dorsal root
Contains axons of sensory information
The dorsal root ganglia contains
Cell bodies of sensory neurons
The spinal nerve is
Distal to each dorsal root ganglion, the sensory and motor roots are bound together into a single spinal nerve
Mixed nerves carry both
Afferent (sensory) and efferent (motor) fibres
The spinal meninges are
Specialised membranes isolate spinal cord from surroundings
The functions of the spinal meninges include:
Protecting spinal cord against bumps and shocks to the skin of the back
Carrying blood supply
Continuous with cranial meninges, which surround the brain
Meningitis is a
Viral or bacterial infection of meninges
The three meningeal layers are the
Dura mater
Arachnoid mater
Pia mater
The dura mater is the
Outer layer of spinal cord
The arachnoid mater is the
Middle meningeal layer
The pia mater is the
Inner meningeal layer
The dura mater is
Tough and fibrous
The dura mater is the layer that forms the
Outermost covering of the spinal cord
This dura mater layer contains
Dense collagen fibres that are oriented along the longitudinal axis of the cord
The arachnoid mater is
The middle meningeal layer
The inner surface of the dura mater and the outer surface of the arachnoid mater are covered by
Simple squamous epithelia
The arachnoid mater includes this
Epithelium called the arachnoid membrane
The pia mater is the
Innermost meningeal layer
The pia mater is a mesh
Of collagen and elastic fibres
The pia mater is bound
To underlying neural tissue
The interlayer spaces of the arachnoid mater are the
Subdural space and the subarachnoid space
The sundial space is between
The arachnoid mater and dura mater
The subarachnoid space is between
The arachnoid mater and the pia mater
The subarachnoid space contains
Collagen/elastic fiber network (arachnoid tribeculae)
The subarachnoid space is filled
With cerebrospinal fluid (CSF)
The cerebrospinal fluid acts as a
Shock absorber and carries dissolved gases, nutrients and wastes
The White mater of the spinal cord is
Superficial and contains myelinated and Unmyelinated axons
The gray mater surrounds the
Central canal of spinal cord
The gray mater of the spinal cord contains
Neuron cell bodies, neuroglia, Unmyelinated axons
The gray matter has
Projections (gray horns)
There are three types of gray horns
Posterior gray horns
Anterior gray horns
Lateral gray horns
The posterior gray horns contain
Somatic and visceral sensory nuclei
The anterior gray horns contain
Somatic motor nuclei
The lateral gray horns are in
Thoracic and lumbar segments; contain visceral motor nuclei
Gray commissures are
Axons that cross from one side of cord to the other before reaching gray mater
The cell bodies of neurons form
Functional groups called nuclei of which there are two kinds
The two types of nuclei are
Sensory nuclei and motor nuclei
The sensory nuclei are
Dorsal (posterior) and connect to peripheral receptors
The motor nuclei are
Ventral (anterior) and connect to peripheral effectors
Sensory and motor nucleus located within gray mater determines
Which body part it controls
On each side of the spinal cord, in medial and lateral sequence, are somatic motor nuclei that control
- Muscles that position the pectoral girdle
- Muscles that move the arm
- Muscles that move the forearm and hand
- Muscles that move the hand and fingers
Because the spinal cord is so highly organised,
We can predict which muscles will be affected by damage to a specific area of gray mater
The White mater on each side of the spinal cord can be divided into
Three regions called columns
The three columns are the
Posterior white columns
Anterior white columns
Lateral white columns
Posterior white columns lie between
Posterior gray horns and posterior median sulcus
Anterior white columns lie between
Anterior gray horns and anterior median fissure
The anterior white commissure is area where
Axons cross from one side of spinal cord to the other
Lateral white columns located on
Each side of spinal cord between anterior and posterior columns
Each column contains tracts (fasciculi) whose
Axons share functional and structural characteristics
A tract, or fasciculus is a
Bundle of axons in the CNS that is somewhat uniform with respect to diameter, myelination, and conduction speed
All axons within a tract
Relay the same type of information (sensory or motor) in the same direction
Ascending tracts
Carry information to brain
Descending tracts
Carry motor commands to spinal cord
Spinal cord summary
Spinal cord has a narrow central canal Is surrounded by gray mater Containing sensory and motor nuclei: Sensory nuclei are dorsal Motor nuclei are ventral
Gray mater is covered by
A thick layer of White mater
White mater consists of
Ascending and descending axons
Is organised in columns
Contains axon bundles with specific functions
Spinal cord is so highly organised it is possible
To predict results of injuries to specific areas
Damage to the ventral root of a spinal nerve, which is composed of both visceral and somatic motor fibres,
Would interfere with motor function
A spinal reflex is a
Rapid, automatic response triggers by specific stimuli. Spinal reflexes are controlled in the spinal cord
The CNS is made up of brain and spinal cord while
Cranial nerves and spinal nerves constitute the PNS
Sensory nuclei recieve and relay sensory information from peripheral receptors whilst
Motor nuclei issue motor commands to peripheral effectors
A disease that damages myelin sheaths would affect the columns in the White matter of the spinal cord
Because the columns are composed of bundles of myelinated axons