Vestibular system, proprioception, somatosensation, cranial nerves Flashcards
(72 cards)
What is proprioception
Proprioception is the awareness of where you are (limbs, body) in relation to other things – other parts of the body, the environment
This may be when parts of the body are static or it may be when they are moving (specifically named kinaesthesia)
How does proprioception wokr
Uses receptors embedded in skeletal muscle, tendons, joint capsules and ligaments to transfer information on muscle length, tension and the amount of joint flexion, along with the rate of change via dorsal root ganglia near spinal cord or trigeminal ganglion in the head to the CNS (spinal cord and brain) to be processed
Activates reflexes to maintain muscle tone
Coordinates posture
Produces effective movement
What is ataxia
If proprioception is disrupted movements become uncoordinated
Is proprioception conscious or unconscious
Much proprioception is unconscious, but some is conscious – we are aware of position and movement of limbs without looking at them
What is the vestibular system (special proprioception)
Primary (but not the only) component of the nervous system responsible for maintaining equilibrium and balance
Maintains stable eye and body position in response to changes in head position
How does vestivular system work
Does this by sensing head motion and regulating lower motor neurons innervating the body and extraocular eye muscles
What does dysfunction of the vestibular system lead to
Dysfunction of the vestibular system results in a multitude of clinical signs demonstrating its widespread integration in normal neurological function
Where is the peripheral vestibular system
The peripheral vestibular system is the inner ear where five structures sitting within the membranous labyrinth (which itself lies within the bony labyrinth) help to coordinate balance based on position:
Describe the two main structures apart of vestibular system
three semicircular canals (each of which contains a semicircular duct) – angular acceleration (head rotations – side to side, up and down, shoulder to shoulder)
two otoliths - saccule and utricle – linear acceleration (forward and back, up and down) - both of these are within the vestibule
How many semicircular canals
3
How many otoliths
2- saccule and utricle
What do semicircular canals measure
angular acceleration (head rotations – side to side, up and down, shoulder to shoulder)
What do otoliths measure
linear acceleration (forward and back, up and down) - both of these are within the vestibule
Two receptor types in vestibular system and what are they on
Crista ampullaris – receptor on semicircular ducts
Macula – receptor on utricle and saccule
How do the receptors dictate the movement direction
Each of these receptors contains hair-like structures (kinocilia and stereocilia) the direction of which dictates the direction of movement the receptor is responsible for detecting
What is endolymph
The vestibular organ is filled with fluid called endolymph and the movement of this endolymph against the cilia is how the receptors detect movement
What cranial nerve do the receptors send information to the brain via
The receptors (cristae ampullaris on semicircular ducts and maculae on saccule and utricle) send this information to the brain via the vestibular part of the 8th Cranial Nerve (vestibulocochlear)
Where do most nerve terminate (vestibular cranial nerves)
Most nerves terminate in the medulla and pons, some go directly to the cerebellum
What two main reflexes does the brain use to maintain balance
Information from the inner ear receptors is interpreted in the brain alongside information from eyes, joints and muscles and maintains balance via two key reflexes – vestibulo-ocular reflex and vestibulo-spinal reflex
What controls the flexor and extensor muscles
Control of flexor and extensor muscles is through the vestibulospinal tract
Are other systems important for equilibrium and balance
The vestibular system is not the only system that plays such a role
Proprioceptive and visual information also important for maintaining equilibrium
Proprioceptors in muscles and joints signal position and movement of body parts
Vision also signals position of the head and body relative to the environment
Symptoms of vestibular disease
Symptoms include falling, head tilt, nystagmus (flickering of the eyeball from side-to-side or up and down), unsteadiness (the patient may drift to one side as they move around) and/or circling
Patients may also feel nauseous or vomit
What can also be affected depending on cause of vestibular disease
Depending on the cause of the vestibular disease, hearing or facial muscles may also be affected, or if the problem is central there may be something which is also affecting other parts of the brain causing seizures, weakness, loss of vision, or difficulty eating and drinking
In dogs what often happens with vestibular disease
In dogs it is often idiopathic, and may occur spontaneously with no identifiable cause. Looks dramatic (and is distressing for the owner and patient) but may resolve quickly, sometimes completely, sometimes with residual head tilt to which the animal can adapt. Nursing care in the first few days is important to support the animal as this condition is distressing and uncomfortable. Antisickness medication may be useful (as used for motion sickness) and prevention of falls, as well as assistance with toileting, eating and drinking are essential.
