PROPRIOCEPTION AND SPINAL ORGANISATION Flashcards
What is proprioception
Perception or awareness of the position and movement of the body
What are the general principles of spinal organisation
- similar fibres (axons) are arranged in tracts
- specific tracts for specific functions
- afferent and efferent regions
- somatotropic organisation
- fibres run in white matter
- poly-synaptic
- decussation
- sensible nomenclature
What does the dorsal funiculus contain
Afferent neurons
What does the lateral funiculus contain
50/50 split between afferent and efferent neurons
What does the ventral funiculus contain
Efferent neurons
What are the general principles of spinal organisation
- Similar fibres (axons) arranged in tracts
- Afferent and efferent regions
- Somatotopic organisation
- Fibres run in white matter
- Poly-synaptic
- Decussation
- Sensible nomenclature
What are the different types of poly-synaptic neurons
- pyramidal
- extrapyramidal
- afferent pathways
What is a pyramidal neuron
1 synapse between brain and muscle (at spinal root)
Mostly limited to forelimbs and responsible for fine motor control
-fast but resource rich
What is an extrapyramidal neuron
- multiple synapseswhich is why it is sower than pyramidal
- responsible for locomotion and posture
- in general projects more to the gamma motor neurone than the alpha
- slow but efficient
What is decussation
When nervous tracts switch sides (e.g. left side of brain controls the right side of the body)
What nerves are exception to the decussation rule
-spinocerebellar
Describe the spinothalamic tract
Has bilateral projections in domestic speecies
What is the species variation in the pyramidal pathway
Increasing the number of functional digits a species has, increased how far the pyramidal pathway goes
E.g. sheep doesn’t project beyond C4 segment
E.g horse stops sat C1- as doesn’t do fine digital movement as only has 1 digit
What are the receptors for propriception
- Muscle spindles
- Golgi tendon organs
- Joint capsule
- Ligaments
- SKIN
What are reflex arcs
- The simple organisation within the nervous system
- Doesn’t require the brain
- Are either monosynaptic or polysynaptic
What fibres are involved in the muscle spindle
- 1a originate from annulospiral endings (wrap around)
- 2 fibres originate from the flower spray nerve endings
Describe 1a fibres
- biggest sensory fibre therefore fastest impulse
- tend to form a monosynaptic connection with alpha motor neurons
- produce impulses proportional to the rate of change of length of the intramural muscle fibres (faster the stretch the faster the response)-produce dynamic information
Describe 2 fibres
- slow
- tend to form polysynaptic responses
- produce impulses proportional to the tension within the intramural muscle fibres responding to change in length
- produce static information
- allow or fine control of intramural muscle fibre length and tension thereby allowing the maintenance of posture
Describe Schaffer’s Sherrington syndrome
- dogs have paralysis in their pelvis and hindlimbs and the forelimbs are rigid and extended
- This is due to an interruption of an ascending spinal cord tract from the lumbar intumescences to the cervical intumescences which inhibits extensors of the forelimbs
Describe golgi tendon organs
- strain gauge
- can produce reverse myotonic reflex
e. g. overload of tension results in release (relaxation) of muscle (to prevent damage) - better placed to respond to tension
What does upper motor neuron damage cause
- spastic paralysis- still has tone
- hyper/normoreflexia - reflex arc still intact so can still perform reflexes
- slow muscle wastage
Describe lower motor neuron damage
- flaccid paralysis
- hypo/areflexia - no reflexes
- rapid muscle wastage
List thoracic outflow of nerves from cranial to caudal
Suprascapular Subscapular Musculocutaneous Axillary Radial Median Ulnar
List pelvic outflow of nerves from cranial to caudal
Femoral Obturator Cranial gluteal Caudal gluteal Sciatic- tibial and Fibular Pudendal
