✅Organisation Of The Nervous System 3 Flashcards
What is a spinal reflex?
A rapid, automatic nerve response triggered by specific stimuli
What is a spinal reflex controlled by?
Spinal cord alone, not brain
Is a spinal Reflex caused by the brain?
No
What is an example of a spinal reflex?
a reflex controlled in the spinal cord makes you drop a frying pan you didn’t realize was sizzling hot. Before the information reaches your brain and you become aware of the pain, you’ve already released the pan.
How long is the spinal cord?
18 inches
How wide in the spinal cord?
1/2 inch
Where does the spinal cord end?
Between vertebrae L1 and L2
What is the cord itself not as long as?
The vertebral column
What divides the spinal cored into left and right?
Grooves
Where is posterior median sulcus?
On posterior side
What is the anterior median fissure?
Deeper groove on anterior side
What are enlargements of the spinal cored caused by?
Amount of grey matter in segment
Involvement with sensory and motor nerves of limbs
What does cervical enlargement do?
It supplies nerves to the shoulder and upper limbs
What does lumbar enlargement do?
Provides innervation to structures of the pelvis and lower limbs
What are the three key areas of gross anatomy of the distal end of the spinal cord?
Conus medullaris
Filum terminale
Cauda equina
What is the conus medullaris?
Thin, conical spinal cord below lumbar enlargement
What is the filum terminale?
Thin thread of fibrous tissue at end of conus medullaris
What does the filum terminale attach to?
Coccygeal ligament
What is cauda equina?
Nerve roots extending below conus medullaris
How many spinal cord segments are there?
31
What changes with age?
The positions of spinal segment and vertebrae
What are cervical nerves named for?
Inferior vertebra
What are all other nerves named for?
Superior vertebra
What are the two branches of spinal nerves?
Ventral root
Dorsal root
What does the ventral root contain?
Axons of sensory neurons
What does the dorsal root contain?
Axons of sensory neurons
What does the dorsal root ganglia contain?
Cell bodies of sensory neurons
Describe the spinal nerve
Distal to each dorsal root ganglion, the sensory and motor roots are bound together into a single spinal nerve
What do mixed nerves do?
Carry booth afferent (sensory) and efferent (motor) fibres
What do specialised membranes isolate?
Spinal cord from surroundings
What are 3 functions of the spinal meninges?
Protecting spinal cord agains bumps and shocks to the skin of the back
Carrying blood supply
Continuous with cranial meninges, which surround the brain
What is meningitis
Viral or bacterial infection of meninges
What are the three meninges layers?
Dura mater
Arachnoid mater
Pia mater
What is the dura mater?
Outer layer of spinal cord
What is arachnoid mater?
Middle meningeal layer
What is pia mater?
Inner meningeal layer
What is the texture of the dura mater?
It is tough and fibrous
What does the dura mater layer form?
The outermost covering of the spinal cord
What does the dura mater contain?
Dense collagen fibres that are oriented along the longitudinal axis of the cord
Further describe the arachnoid mater
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.
What is the texture of the pia mater?
A mesh of collagen and elastic fibres
What is the pia mater bound to?
Underlying neural tissue
Where is the subdural space in the arachnoid mater?
Between arachnoid mater and pia mater
Where is the subarachnoid space in the arachnoid mater?
Between arachnoid mater and pia mater
What does the subarachnoid space contain?
Collagen/ elastin fiber network ( arachnoid trabeculae)
What is the subarachnoid space filled with?
Cerebrospinal fluid (CSF)
What doesCSF act as?
A shock absorber
What does CSF carry?
Dissolved gases, nutrients, and wastes
Is white matter superficial?
Yes
What does white matter contain?
Myelinated and unmyelinated axons
What does grey matter surround?
The central canal of spinal cord
What does gray matter contain?
Neuron cell bodies, neuroglia, unmyelinated axons
What are gray horns?
Gray matter projections
What are the three gray horns
Posterior
Anterior
Lateral
What do posterior gray horns contain?
Somatic and visceral sensory nuclei
What do anterior gray horns contain?
Somatic motor nuclei
What are lateral gray horns in?
Thoracic and lumbar segments; contain visceral motor nuclei
What are commissures?
Axons that cross from one side of cord to the other before reaching gray matter
What do the cell bodies of neurons form?
Functional groups called nuclei
Describe sensory nuclei?
Dorsal (posterior)
Connect to peripheral receptors
Describe motor nuclei
Ventral (anterior)
Connect to peripheral effectors
What do Sensory or motor nucleus location within the gray matter determine?
What body part it controls
On each side of the spinal cord, in medial to 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, and
- muscles that move the hand and fingers.
What can we predict because the spinal cord is sop highly organised?
which muscles will be affected by damage to a specific area of gray matter.
The white matter on each side of the spinal cord can be divided into three regions
called columns, what are they?
Posterior
Anterior
White
Where do posterior white columns lie?
Between posterior gray horns and posterior median sulcus
Where do anterior white columns lie?
Between anterior grey horns and anterior median fissure
What is anterior white commissure?
Area where axons cross from one side of spinal cord to the other
Where are lateral white columns located?
On each side of spinal cord between anterior and posterior columns
What does each column contain?
Tracts (fasciculi) whose axons share functional and structural characteristics
What is a tract? (Fasciculus)
a bundle of axons in the CNS that is somewhat uniform with respect to diameter, myelination, and conduction speed.
What do all axons within a tract do?
relay the same type of information (sensory or motor) in the same direction.
What do ascending tracts carry?
Information to brain
What do descending tracts carry?
Motor commands to spinal cord
What is the central canal surrounded by?
Gray matter
What does the central canal contain?
Senroray nuclei (dorsal) Motor nuclei (ventral)
What is grey matter covered by?
A thick layer of white matter
What does white matter consist of?
Ascending and descending axons
How is white matter organised?
Columns
Summary: What does white matter contain?
Axon bundles with specific functions
Name the components of the central nervous system and of the peripheral nervous system.
The central nervous system is made up of the brain and spinal cord, while cranial nerves and spinal nerves constitute the peripheral nervous system.
Define spinal reflex
A spinal reflex is a rapid, automatic response triggered by specific stimuli. Spinal reflexes are controlled in the spinal cord
Identify the three spinal meninges.
The three spinal meninges are the dura mater, arachnoid mater, and pia mater.
Damage to which root of a spinal nerve would interfere with motor function?
Damage to the ventral root of a spinal nerve, which is composed of both visceral and somatic motor fibres, would interfere with motor function.
Differentiate between sensory nuclei and motor nuclei.
Sensory nuclei receive and relay sensory information from peripheral receptors. Motor nuclei issue motor commands to peripheral effectors.
A disease that damages myelin sheaths would affect which portion of the spinal cord?
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.
