Lecture 2: Spinal cord Flashcards
What is the purpose of the spinal cord
Send motor information from the CNS (brain) to the PNS (skin) and sensory information from the PNS to the CNS
How the 31 nerves in the spinal cord divided up top to bottom
8 pairs of cervical nerves, 12 pairs thoracic nerves matching the ribs, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerves.
What are the two enlargements on the spinal cord and why
Cervical enlargement- where all the sensory/ motor info for arms and hands are
Lumbar enlargement- where all the sensory/motor info for legs is.
Enlargement because they need more SA for more neurons
What is the cauda equina
The horses tail, roots of the lumbar, sarcral and coccygeal nerves that spread out laterally
What is the conus medullaris
Cone shaped end of the spinal cord
What are dermatones
They are segments of the body that provides sensory input to the CNS through one pair of spinal nerves. As these areas are mapped, and although there can be some overlap between areas, they can be used to determine if there is damage to specific parts of the spinal cord
What is the organisation of white matter and grey matter in the spinal cord and the orientation regarding anterior and posterior
White matter on the outside and grey matter butterfly in the middle The small wings of the butterfly are closest to the posterior
How is the white matter of the spinal cord organised
Into three white columns sectioned off by the butterfly: anterior, posterior and lateral. These contain distinct bundles of axons going to the same destination carrying the same information= tracts.
How is the grey matter of the spinal cord organised and what does each section contain
The tips of the butterfly are called ‘horns’. The posterior horns (small wing tips) contain the axons of incoming sensory neurons and interneurons. The anterior horns (bigger wing tips) contain somatic motor nuclei that give nerve impulses for skeletal muscle. The lateral horns- in the middle of the edge of the butterfly have autonomic motor neurons for cardiac, smooth and glands.
What are ‘nuclei’ in grey matter and the two types
clusters of neuronal cell bodies that form functional groups. Sensory nuclei receive input from sensory neurons and motor nuclei provide output to effector tissues via motor neurons.
Where do the cell bodies of incoming sensory neurons located in
the posterior (dorsal) root ganglion of the spinal nerve
Where does sensory information sent to the CNS (general afferent pathway) first enter at what root
Nerve impulses from the sensory receptor go along the axon which enters the spinal cord at the posterior (dorsal) root. The cell bodies are in the dorsal root ganglia. They can then go 3 possible pathways
What are the 3 possible pathways for sensory information to go from once it enters the spinal cord
- Axons can extend into the white matter of the spinal cord and ascend into the brain as part of the sensory tract.
- Axons of neurons may enter the posterior grey horn and synapse with interneurons whose axons extend into the white matter of the spinal cord.
- Axons of neurons may enter the posterior grey horn and synapse with interneurons that in turn synapse with somatic motor neurons involved in spinal reflex pathways
What is the difference between the first order neurons that carry touch/pressure and pain/temperature sensation
Pain and temperature is carried by unmyelinated neurons with free nerve endings.
Touch and pressure are carried by myelinated pseudounipolar neurons with encapsulated nerve endings
The capsule of the nerve ending determines what type of information a nerve will respond to. What are the names of the different capsules for touch and pressure
touch: Meisners corpuscles, Pressure is pacinian corpuscle.
Define sensation vs perception
The conscious or subconscious awareness of changes in the external or internal environments. Perception of sensation only happens when impulses reach the cerebral cortex.
Each neuron only transmits information about one sensory modality. What is a sensory modality
A unique type of sensation- one type of sensory information.
What are the four kind steps that lead to sensation being felt
- Stimulation of the sensory receptor
- Energy of Stimulus converted to graded potential (transduction)
- Generation of nerve impulse that go to CNS
- Integration of sensory input in the cerebral cortex which leads to perception.
What are three main layers of the protective structures for the spinal cord and brain (CNS)
- The outer skull/ vetebral column made of bone
- The three connective tissue layers of the meninges
- The cerebrospinal fluid/ fat and connective tissue in the space between two of the meningeal membranes
What is the order of the 3 spinal meningeal membranes from outside to inside
Dura mater, Arachnoid mater and Pia mater.
Describe the dura mater. What is it continuous with
Thick strong layer of dense irregular connective tissue. It forms a sac form the foramen magnum in brain to sacral vertebra 2. It is continuous with the meningeal dura mater of the brain and epineurium
What is the epineurium
the outer covering of spinal and cranial nerves
Describe the Arachnoid mater. What is it continuous with
Middle layer. It is a thin avascular covering made of cells and loosely arranged collagen and elastin fibres. Through the foramen magnum It is continous with the arachnoid mater of the brain
Where is the subdural space and what does it contain
Between the dura mater and arachnoid mater and it contains interstitial fluid
Describe the Pia mater. What other structures are at this layer
Thin transparent connective tissue layer that sticks to the surface of the spinal cord and brain. It is thin squamous cuboidal cells with collagen and elastic fibres interlacing.
At this layer there are blood vessels for the spinal cord and denticulate ligaments.
What is the subarachnoid space and what does it contain
Between arachnoid and pia mater space containing shock absorbing cerebrospinal fluid.
What are denticulate ligaments
triangular Thickenings of pia mater that stick outwards and fuse with the arachnoid mater + inner surface of dura mater between the nerve roots entering the spinal cords at both sides
What is in the epidural space and where is it
Space between the dura mater and wall of the vertebral canal. It contains fat and connective tissue.
