Spinal cord tracts Flashcards
How is the nervous system organised?
Into the Central and Peripheral nervous system
What are afferent somatic (sensory) nerves
nerves that come from the skin/ retina
What are afferent visceral (sensory) nerves?
nerves that come from thoracic/ abdominal areas
What are efferent somatic (motor) nerves?
Nerves that go towards skeletal muscle
What are efferent visceral (motor nerves)?
Nerves that go towards cardiac muscle
What is a reflex?
an inherent, subconscious, relatively consistent response to a particular stimulus
What are exteroreceptors?
Receptors that receive input from outside the body, e.g olfactory, smell and sight
What are interoreceptors?
Receptors that receive input from inside of the body/ internal environment
What are proprioreceptors?
Receptors used in spatial orientation/ mechanical so limbs etc.
What are the main functions of the motor system?
to maintain posture, gait and provide a stable platform for movement
Where are UMN found?
they are completely contained within the central nervous system and usually located in the brain stem or the forebrain
What is the function of UMN?
modify and regulate the activity of LMN
Where are LMN found?
their cell body is in the CNS and their axons project into the PNS via cranial or spinal nerves
What is an ascending pathway?
They carry information from the receptors to the brain
What is a descending pathway?
Carries information from the brain to effectors via the spinal cord
What are tracts and where are they found?
Tracts are a bunch of functionally related axons found in the CNS (white matter)
What is the first order neuron?
spinal ganglion
What is the second order neuron?
In the spinal cord
What is the third order neuron?
thalamus
What is the somatosensory cortex?
Area where pain is localised
What is the Spinocervicothalamic tract?
Concerned with the transmission of superficial pain and tactile sensations considered primary conscious pathway in carnivores
What are the four extrapyramidal spinal pathways?
Rubrospinal, Vestibulospinal, Reticulospinal, and Tectospinal
Which pathways control involuntary movement and adjustment of posture?
Vestibulospinal, Reticulospinal and Tectospinal
Which spinal pathway controls voluntary movements?
Rubrospinal pathway
Explain the patellar reflex
Tapping the patellar tendon activates the receptors in the quadriceps muscle, this then sends an impulse through the afferent sensory nerve to the spinal cord
Efferent motor nerve (femoral nerve) then extends/contracts the quadricep muscle whilst simultaneously inhibiting the hamstring from flexing
Where does the motor component of the femoral nerve arise from?
L4-L6
What nerve does the withdrawal reflex primarily test for?
Tests primarily for the sciatic nerve and the spinal cord
What are the two pathways motor systems are functionally grouped into?
Ventromedial motor system and the Dorsolateral motor system
What is the ventromedial motor system?
axial and proximal limb muscles, especially extensors
What type of reflex is the patellar reflex?
It is a type of myotatic reflex
Describe the spinothalamic tract
1) Receives pain stimulation from nociceptors
2) Pain stimulation travels to the first order neuron in the dorsal horn
3) neuron decussates to the other side to reach the second order neuron which then ascends along the tract
4) Third order neurons in the thalamus receive the stimulation and carry the impulse to the somatesthetic area of the cerebral cortex
What are the two types of spinothalamic tract?
tract that goes to the lateral thalamus (neurons that decussate) = intensity of the pain
tract that goes to the medial thalamus (neurons that do not decussate) = emotional aspects of pain
In what area of the dorsal horn are most of the projection neurons concentrated (for the spinothalamic tract)
Marginal nucleus and nucleus proprius
What is the difference between spinothalamic and spinocervicothalamic?
Spinocervicothalamic is mostly concerned with carnivores
And has a 4th order neuron
Describe the spinocervicothalamic pathway
1) Pain sensation from nociceptors along 1st order neuron
2) reaches the second order neuron on the marginal nucleus/ nucleus proprius which then ascends ipsilaterally
3) Terminates with the 3rd order neurons on the lateral cervical nucleus which then decussate to terminate on the 4th order neurons at the contralateral thalamus
4) these axons then project to the cerebral cortex
In what segment is the lateral cervical nucleus found?
C1, C2
What 4 pathways are knowns as extrapyramidal and why?
Rubrospinal, Reticulospinal, Tectospinal and vestibular spinal
because they pass outside of the ventral pyramids in the medulla
