Maintaining balance and posture Flashcards by Ryley Cornfield

Posture =

Relative position of various parts of the body with respect to one another

How well did you know this?

Not at all

Perfectly

2 types of postural equilibrium =

Static

Dynamic

How well did you know this?

Not at all

Perfectly

Postural system afferents come from:

Somatosensory receptors on skin
Proprioceptions on muscles and joints
Visual system
Vestibular system

How well did you know this?

Not at all

Perfectly

Where do the efferents for the postural system converge?

Brain stem

How well did you know this?

Not at all

Perfectly

2 dorsolateral pathways:

Corticospinal

Rubrospinal

How well did you know this?

Not at all

Perfectly

4 ventromedial pathways:

Tectospinal
Vestibulospinal (lateral and medial)
Pontine reticulospinal
Medullary reticulospinal

How well did you know this?

Not at all

Perfectly

Another name for pontine and medullary reticulospinal tracts

medial and lateral reticulospinal tracts

How well did you know this?

Not at all

Perfectly

Which ventromedial tract decussates?

Tectospinal

How well did you know this?

Not at all

Perfectly

Brainstem areas which go to the ventral horn of spinal cord to coordinate postural responses:

Vesticular nuclei (medulla)
Superior colliculus (midbrain)
Pontine and medullary reticular formation

How well did you know this?

Not at all

Perfectly

Superior colliculus is located in the

Midbrain

How well did you know this?

Not at all

Perfectly

Vestibular nuceli is located in the

Medulla

How well did you know this?

Not at all

Perfectly

What does the medial vestibulospinal and tectospinal tract have in common?

Act on head and neck muscles

How well did you know this?

Not at all

Perfectly

2 pathways of vestibulospinal tract and their broad functions

Lateral - axial extensor muscles

Medial - head and neck extensors

How well did you know this?

Not at all

Perfectly

Extensor muscles also known as

Antigravity muscles

How well did you know this?

Not at all

Perfectly

What type of postural reflex is the vestibulospinal tract most involved in

Compensatory

How well did you know this?

Not at all

Perfectly

Input to tectospinal tract from:

Optic nerves
Retina
Auditory

How well did you know this?

Not at all

Perfectly

Where does the tectospinal tract decussate?

Midbrain - very early

How well did you know this?

Not at all

Perfectly

Function of tectospinal tract:

Movements of head in relation to visual stimuli

How well did you know this?

Not at all

Perfectly

Function of pontine reticulospinal tract:

Enhances antigravity reflex. Extensors of lower limbs. Increases tone.

How well did you know this?

Not at all

Perfectly

Function of medullary reticulospinal tract:

Liberates antigravity muscles (flexors). Reduces muscle tone)

How well did you know this?

Not at all

Perfectly

Transection studies allow us to

Remove components of brain (e.g. cerebrum) to study function of one part (e.g. brainstem)

How well did you know this?

Not at all

Perfectly

If you transected the cerebrum away from the brainstem what would happen and why?

Decerebrate posturing/decerebrate rigidity: massive increase in tone of extensors as there is no tonic inhibition of the efferents from the cerebrum and cerebellum

How well did you know this?

Not at all

Perfectly

Cause of decerebrate posturing:

Brainstem damage

How well did you know this?

Not at all

Perfectly

Cause of decorticate posturing:

Cerebral damage

How well did you know this?

Not at all

Perfectly

Which type of posturing is more 'severe'

Decerebrate

Function of vestibular system:

- Sense of balance and motion detection | - Info about head orientation, movements in 3D space

2 otolith organs:

urticle | saccule

Urticle and saccule detect what using what

Linear movement using macule

Urticle detects =

Horizontal acceleration

Saccule detects =

Verticle acceleration

Structures in the vestibular system:

- Otolith organs - Semicircular canals - Ampulla

Semicircular canals detect

Head roation, angular acceleration

What does both the macule and ampulla contain?

Hair cells

Describe the structure of the macule in otolith organs:

Hair cells connected to sensory nerve fibers Gelatinous cap over the top Otoliths covering cap which move

Otoliths are

Calcium carbonate crystals

Depolarisation of hair cells occurs when

Stereocillia move toward kinocillum

Hyperpolarisation of hair cells occurs when:

Stereocilla move away from kinocillum

3 semicircular canals:

- Anterior - Posterior - Lateral/horizontal

Semiciruclar canals are filled with

Endolymph

Main sensory structure of semicircular canals =

Ampulla

What is found in the ampulla of semicircular canals:

Hair cells | Cupula

Where do sensory nerve fibers of CN VIII project to:

- cerebellum - down through spinal cord to limbs, neck - extraocular muscles

Function of vestibulo-ocular reflex:

Compensatory mechanism of eyes, eyes move in opposite direction to head rotation (to maintain a steady image on back of retina)

What would happen in head turns left (VOR reflex)

- Endolymph of left horizontal canal moves right and is excited (left is inhibited). - Signal to vestibular nuclei which synapses with abducens (opposite side) and oculor motor (same side) - Right abducens flexes right lateral rectus - Left oculormotor flexes left medial rectus - Eye moves right

Name of test for VOR in unconscious patient:

Caloric testing

Calortic testing can be done with:

Cold water | Hot water

Brainstem in tact with caloric testing:

eyes move away (cold) | towards (hot) - in fast nystagmus

Nystagumus =

Involuntary movement of eye

2 phases of physiologic nystagumus:

Slow - slow movement to opposite | Fast - quick movement to same

If in caloric testing only one eye moved what might this suggest.

Bilateral MLF lesion (medial longitudinal fasiculus) lesion

Low brainstem lesion caloric testing:

No movement

What can be used to test the vestibular system

Posture platform studies

What do you do to patient to test vestibular balance system

Blindfold

Reticular formation is important in which kind of postural control:

Anticipatory

Name 3 disorders of the vestibular system:

Menieres syndrome BPPV - benign paroxysmal postural vertigo MAV - migraine associated vertigo

Cause of menieres syndrome =

Excess endolymph - distended ducts - damage to membranes

Symptoms of menieres syndrome =

Tinnitus Sensorineural hearing loss Vertigo

Treatment of menieres syndrome -

Symptomatic. Prochlorperazine - nausea and vomiting Antihistamines - nausea, vomiting, vertigo Treat hearing

Prochlorperazine moa

Dopamine antagonist (anti-psychotic)

Symptoms of BPPV

Suddenly feeling dizzy on moving head or rolling in bed, nausea, vomiting

Cause of BPPV

CaCO3 crystals from otolith organs dislodge and disrupt flow of endolymph in semicircular canals

Which semicircular canal is involved when turning head left to right

Horizontal