Spinal tracts Flashcards
What is the purpose of different segments in the spinal cord?
They have different workloads.
What is the reason for cervical and lumbar enlargement in the spinal cord?
They have extra inputs and outputs and required to manage sensory and motor.
What protection does the spinal cord have?
Meninges.
What is the purpose of thin connective tissue in the spinal cord?
Anchors the spinal cord to the area of the coccyx.
What is the general overview of the CNS?
Ascending sensory pathways into the brain, descending motor pathways to the body (away from the brain).
What are sensory pathways?
Carry info from sensory receptors to the brain.
Which info reaches the cerebral cortex?
The conscious.
Which info doesnt reach cerebral cortex?
The unconscious (eg moving leg)- carry to the cerebellum.
What are the unencapsulated nerve endings?
Free nerve endings, tactile discs, hair receptors.
What are free nerve endings?
Pain, heat and cold. Found in epithelia and connective tissues.
What are tactile discs?
Light, touch, texture, edges and shapes. Found in stratum basale.
What are hair receptors?
Movement of hairs, found around the hair follicle.
What are the encapsulated nerve endings?
Tactile corpuscles, Krause end bulbs, lamellated corpuscles, Ruffini corpuscles, muscle spindles, Golgi tendon organs.
What are tactile corpuscles?
Light, touch and texture. In palms, eyelids, nipples, genitals.
What are Krause end bulbs?
Similar to tactile corpuscles, in mucous membranes.
What are lamellated corpuscles?
Deep pressure, stretch, tickle, vibration. Found in joint capsules, breasts, genitals.
What are Ruffini corpuscles?
Heavy touch, pressure, stretching of skin, joint movements. In dermis and joint capsules.
What are muscle spindles?
Muscle stretch. Found in skeletal muscles near tendon.
What are Golgi tendon organs?
Tension on tendons and found in tendons.
Which sensory receptors help understand the position of movement of muscles and joints?
Ruffini corpuscles, muscle spindles and Golgi tendon organs.
What is the meaning of decussation?
Crossing of nerve fibres (cross the midline of the body).
What is the process of the generic sensory pathway?
-The 1st order neuron (sensory cell body in the dorsal route ganglion) -2nd order neuron (cell body in the dorsal grey matter).
-3rd order neuron (cell body in the thalamus)- decussates and is like a distribution centre- the sensory info is sent here and directed where to go).
How do these pathways travel?
Through action potentials (APs).
Where is the 1st order neuron in the spinothalemic pathway?
Cell body in the dorsal route ganglia.
Where is the 2nd order neuron in the spinothalemic pathway?
Cell body in dorsal horn.
Where is the 3rd order neuron in the spinothalemic pathway?
Cell body in thalamus.
Where does it decussate in the spinothalemic pathway?
After the 2nd order neuron, carried to the contralateral sensory synapse.
Is the spinothalemic pathway direct or indirect?
Direct.
Where are the synapses for the indirect pathway of spinothalemic?
-reticular formation
-hypothalamus
-limbic system (emotional)
What happens if there is spinothalemic damage?
The pathways are crossing the midline of the spinal cord- therefore, damage to the left hand side means you would feel pain in the contralateral side (right).
What senses would you lose with damage to spinothalemic?
Touch, pain, warmth/ cold
Where is the dorsal column pathway?
Posteriorly along the spinal cord. Two columns each for upper and lower and both travel through the ipsilateral side.
Where is the 1st order neuron in the dorsal column pathway?
Cell body in dorsal route ganglia.
Where is the 2nd order neuron in the dorsal column pathway?
In the medulla.
Where is the 3rd order neuron in the dorsal column pathway?
In the thalamus- projects info into the sensory cortex.
Where does decussation occur in the dorsal column pathway?
In the brainstem (2nd order and decussation are in different places).
What happens with dorsal column pathway damage?
Loss of touch, proprioception and vibration and would be felt on the ipsilateral side.
What is the Romberg’s test?
This is where you stand still and close your eyes. If you wobble or fall over, you have a proprioceptic deficit (dorsal column damage).
What is the spinocerebellar pathway?
This is connectivity between the spine and cerebellum.
How many neurons are in the spinocerebellar pathway?
Only two.
Which side do the neurons travel in the spinocerebellar pathway?
All up the ipsilateral side. Delivers proprioceptive info to the cerebellum.
Are we consciously aware of the spinocerebellar pathway?
No, and therefore, it doesnt reach the somatosensory cortex.
What happens if there is damage to the spinocerebellar pathway?
Clumsy movements, incoordination of limbs.
What direction do motor pathways travel?
Top to bottom (brain to muscles).
Where is the UMN located in pyramidal?
In the brain.
Where is the LMN located in pyramidal?
In ventral grey matter.
What route do motor pathways travel in?
Through the ventral route.
What are the 2 types of motor pathway?
-Pyramidal (direct)- directly through the brain stem into the spinal cord. —-Extrapyramidal (indirect)- no well defined direct connection from motor cortex to LMNs.
Are pyramidal pathways conscious or subconscious?
Conscious.
Are extra pyramidal conscious or subconscious?
Mostly subconscious.
Where is the LMN in the corticospinal pathway?
Spinal cord. Goes to the ventral spinal roots to control limbs.
Where is the LMN in the corticobulbar pathway?
Brian stem. Goes to the cranial nerves that control the face.
It is diverted to control the face, the rest of the fibres carry on down.
What percentage of fibres decussate after the pyramids?
90% (control the limbs).
What percentage of fibres decussate at segmental level?
10% (control the torso, back etc).
What is the purpose of extra-pyramidal pathways?
These are unconscious and adjust the tone of muscles etc (balance eg).
What is the rubrospinal tract?
Rubio means red as cell body is in the ‘red nucleus’ (part of midbrain that has lots of Hb in).
Mainly for fine motor coordination in upper limb.
Where does decussation occur in the rubrospinal tract?
After the UMN.
Where do most fibres exit in the rubrospinal tract?
In the cervical spine, therefore, mainly in the upper limb for adjusting motor control.
What is the tectospinal tract?
This is for controlling the neck muscles (head- eye coordination and visual and auditory feedback).
Where is the UMN in the tectospinal tract?
In the midbrain projecting down.
Where does decussation occur in the tectospinal tract?
In the midbrain.
What is the vestibulospinal tract?
This is for balance and receives sensory info about balance from the inner ear.
Ipsilateral projection down to the lumbar spine.
Where is the UMN in the vestibulospinal tract?
In the pons.
What is the reticulospinal tract?
This is for motor functions, autonomic functions (resp function) and pain modulation (suppression of spinal reflexes).
