Exam 4 Part IV

Question 1

reticular formation

Answer 1

Much of what most of these brainstem pathways do is to provide background contraction of the trunk and neck musculature and the proximal portion of the limbs. The purpose of much of this is to support the body against gravity.

Question 2

The intrinsic activity of these brain stem areas including RF shows up in the

Answer 2

The intrinsic activity of these brain stem areas including RF shows up in the decerebrate animal (sectioned at midbrain), where activity causes rigidity, particularly of antigravity muscles, called an “extensor rigidity”.

Question 3

sensory cells in the maccula

Answer 3

The sensory cells are the hair cells which synapse with the vestibular nerve

Question 4

Each macula with its hair cells is covered with a

Answer 4

Each macula with its hair cells is covered with a thick gelatinous layer in which calcium carbonate crystals (called statoconia or otoliths) are imbedded

Question 5

Different hair cells are oriented in all different directions, so in different head positions, different hair cells are stimulated. This pattern of stimulation is what

Answer 5

Different hair cells are oriented in all different directions, so in different head positions, different hair cells are stimulated. This pattern of stimulation is what tells the nervous system the position of the head with respect to gravity.

Question 6

The vestibular, cerebellar & reticular motor systems reflexly excite the correct muscles to maintain .

Answer 6

The vestibular, cerebellar & reticular motor systems reflexly excite the correct muscles to maintain balance.

Question 7

So: the maculae function in both

Answer 7

So: the maculae function in both static equilibrium and linear acceleration to maintain body equilibrium.

Question 8

If the head suddenly rotates, the __(the viscous fluid) tends to remain stationary while the _canals turn

Answer 8

If the head suddenly rotates, the endolymph (the viscous fluid) tends to remain stationary while the semicircular canals turn

Question 9

sudden rotation of the head

Answer 9

This causes relative fluid flow in the canals in the direction opposite to the rotation of the head. This excites the hair cells. Then if the rotation continues, the hair cells cease firing,

Question 10

head suddenly stops rotating

Answer 10

the hair cells give a signal because the endolymph is still moving & the semicircular canals are not. They detect the beginning and end of head rotation, which says where the head will be.

Question 11

Loss of function of the semicircular canals causes

Answer 11

Loss of function of the semicircular canals causes a person to have poor equilibrium when performing fast and intricate body movements.

Question 12

Removal of certain [flocculonodular] lobes of the cerebellum prevents

Answer 12

Removal of certain [flocculonodular] lobes of the cerebellum prevents normal semicircular canal functioning

Question 13

Vestibular postural reflexes

Answer 13

Vestibular postural reflexes help maintain posture & equilibrium. If an animal suddenly falls forward, the paw comes out to catch the animal, extensor muscles tighten to prevent the head from hitting the ground.

Question 14

Each time the head is suddenly rotated,

Answer 14

Each time the head is suddenly rotated, signals from the semicircular canals cause the eyes to rotate in an opposite direction.

Question 15

Nystagmus:

Answer 15

Nystagmus: the jerky involuntary eye movement at the start & end of rotation is the naturally stimulated nystagmus that uses the vestibular system.

Question 16

when nystagmus has a direction, by convention the

Answer 16

when nystagmus has a direction, by convention the fast component is taken as the direction of nystagmus.

Question 17

types of nystagmus

Answer 17

rotatory
postrotatory
caloric
optokinetic
cerebellar

Question 18

rotatory nystagmus

Answer 18

Rotatory: fast in the direction of rotation, slow component is still looking at old visual field

Question 19

Postrotatory

Answer 19

Postrotatory – opposite to the direction of rotation

Question 20

caloric nystagmus

Answer 20

Caloric - cool or warm H2O in ear: COWS = Cool Opposite warm same.

Question 21

optokinetic nystagmus

Answer 21

Optokinetic – head is stationary, visual field is moving, slow component following visual field, fast – Opposite movement of visual field. Controlled by visual system.

Question 22

Physiologic nystagmus (microsaccades) –

Answer 22

Physiologic nystagmus (microsaccades) – no directionality, when a person fixates, eyes move back & forth (to keep the photoreceptors from adapting)

Question 23

• Cerebellar:

Answer 23

• Cerebellar: a person with cerebellar damage fixates to the side:

Question 24

Motion sickness can come from

Answer 24

Motion sickness can come from excessive vestibular stimulation, actual motion. Vertigo can come from vest. inflamm., dislodged otoliths etc., sensation of movement when stationary.

Question 25

Quinine (tonic)

Answer 25

Quinine (tonic) toxic to vest. syst. No gin and tonic for you! Particularly if you’re going to fly an airplane.

Question 26

The vestibular apparatus only detects

Answer 26

`The vestibular apparatus only detects movements of the head. For balance to be maintained, there must also be information about position of the head with respect to the body.

Question 27

bending the neck doesn’t mean the person is

Answer 27

bending the neck doesn’t mean the person is off balance. Bending the neck signals oppose the vestibular reflexes. The 2 sets of reflexes are both operating?, I don’t need to put out my paws to correct when I bend my head forward: the reflexes cancel

Question 28

Proprioceptors and exteroceptors (e.g., pressure on footpads) in

Answer 28

other parts of the body give information about whether weight is distributed equally.

Question 29

Visual information can be used about

Answer 29

Visual information can be used about whether a person is balanced or not. Even with complete destruction of the vestibular system a person can have almost normal equilibrium with the eyes open and if all motions are performed slowly. When performed rapidly or with eyes closed, equilibrium is lost.

Question 30

The basal nuclei =

Answer 30

The basal nuclei = caudate, putamen & globus pallidus.

Question 31

The caudate & putamen together are the .

Answer 31

neostriatum.

Question 32

One of the general effects of diffuse excitation of the basal nuclei is

Answer 32

decreased muscle tone throughout the body.

Question 33

With widespread destruction of the B.G.,

Answer 33

With widespread destruction of the B.G., rigidity results. In decerebrate rigidity (sectioning at the midbrain), the inhibitory effects of the B.G. are absent.

Question 34

So the B.G. have a generally inhibitory effect, but:

Answer 34

Stimulating certain specific areas can even elicit complex movements (which should not be too surprising for a motor control area).

Question 35

he neostriatum (caudate and putamen) helps control

Answer 35

he neostriatum (caudate and putamen) helps control gross intentional movement that we normally perform unconsciously, such as “limb fixation”, in conjunction with the motor cortex.

Question 36

Chorea

Answer 36

Chorea = dance. Random “flicking” motions, occurring one after another suddenly switching to another pattern of movement:

Question 37

Huntington’s chorea –

Answer 37

Huntington’s chorea – a genetic disorder that starts with flicking motions and becomes progressively more exaggerated in movements finally leading to a dementia. It is autosomal dominant (a child has 50% chance of getting it if one parent has the gene). The disease does not show up till the mid-thirties or so.

Question 38

In Huntington’s chorea, there is a loss of

Answer 38

In Huntington’s chorea, there is a loss of GABA in striatonigral neurons (associated with degeneration of the caudate and putamen). Also loss of ACh neurons.

Question 39

athetosis

Answer 39

athetosis – slow, writhing, wormlike movements which occur continuously. If so slow it is almost posture, called dystonia. Damage to globus pallidus &/or putamen, many diff. causes.

Question 40

Choreoathetosis:

Answer 40

Choreoathetosis: additional damage to neostriatum

Question 41

Ballism –

Answer 41

Ballism – succession of violent movements of large areas of the body. A leg or limb might jerk suddenly into full flexion or the whole body may twist.

Question 42

Parkinson’s

Answer 42

rigidity – mask-like expression, resistant to passive stretch:
tremor-at-rest (NOT cerebellar intention tremor)
iii.akinesia – inability to initiate movement. One patient threw paper

Question 43

substantia nigra treatments

Answer 43

L-DOPA (dopamine doesn’t cross the blood-brain barrier =BBB).
Normally the dopamine-containing cells inhibit ACh neurons, so anti-ACh can help.
Transplant DA-producing cells into brain: often overproduction\
Anti-oxidants to forestall damage: preventing excitotoxicity

Question 44

Parkinson’s patients given too much L-DOPA can develop

Answer 44

Parkinson’s patients given too much L-DOPA can develop Tourette’s-like symptoms. People given anti-psychotics blocking dopamine receptors can develop some Parkinson-like rigidity, among other things.

Question 45

lesion to the motor cortex caused by

Answer 45

Usually caused by stroke, either ruptured blood vessel or thrombosis

Question 46

Removal of a very small portion of the primary motor cortex –

Answer 46

Removal of a very small portion of the primary motor cortex – the area that contains the giant Betz pyramidal cells. In the monkey, loses voluntary control of discrete movements of the hands and fingers. Finger movements are gone.

Question 47

Lesions of the primary motor cortex alone yields

Answer 47

Lesions of the primary motor cortex alone yields hypotonia 1°motor cortex exerts a tonic stimulatory effect, so loss causes hypotonia

Question 48

Most lesions that occur involve both the motor cortex and the B.G. This results in

Answer 48

spasticity because of release from normal inhibitory influence of B.G. If the damage is to below the caudate decerebrate rigidity

Question 49

he Babinski sign:

Answer 49

In infants (whose cortices have not taken over yet or destruction of foot region of the area pyramidalis in 1° motor cortex or of the pyramidal tract.

Question 50

damage in Voluntary eye movement field

Answer 50

Voluntary eye movement field can’t voluntarily move eyes around.Instead – controlled by this area in the back – eye fixation area stare fixedly

Question 51

damage to head rotation area

Answer 51

Head rotation area – closely associated with eye movement field – can’t direct head toward different objects.

Question 52

damage to hand skills area

Answer 52

Hand skills area – hand movements become uncoordinated and non-purposeful = motor apraxia