KNES 365 - Midterm II Review (Part II)

What is the vestibulo-ocular reflex?

reflex that stabilizes the eyes in space when the head is moved around — head rotates + then the eyes counter-rotate to stay fixed in position

The hair cells within the ampullae on either side of the head have ____________ preferred directions of head rotation. Head rotation to the left ____________ firing rates in left ampulla afferents and _____________ firing rates in right ampulla afferents.

opposite, increase, decrease

If the head is turned to the left, the eye muscles that pull the eye to the right must be ___________ and their antagonists ____________. Which muscles would these be?

contracted, relaxed

right lateral rectus (contracted)

right medial rectus (relaxed)

left lateral rectus (relaxed)

left medial rectus (contracted)

What is the vestibulo-collic reflex (VCR)?

reflex that stabilizes the head in space when moving around — head is tilted, neck counter-rotates to keep head fixed in position

Tilting the head to the left ____________ the firing rate in the medial portion of the left utricle and ____________ the firing rate in the medial portion of the right utricle. This leads to increasing muscle contraction of lateral flexor motor neurons on the ________ side of the head that will bring the head vertical.

increases, decreases, right

In the vestibulo-spinal pathway, efferent neurons from the medial vestibular nucleus (MVN) project down the ventral-medial portion of the brainstem + into the cervical spinal cord to control _____________ bi-laterally (the VCR).

Efferent neurons from the lateral vestibular nucleus (LVN) project down the lateral vestibular tract to ventral horns in the thoracic, lumbar and sacral spinal segments to activate axial/proximal muscles controlling ______________.

neck muscles

posture + balance

Vestibular reflexes that control posture + balance are called _______________.

vestibular spinal reflexes (VSR)

The _____________ receives input from the vestibular nucleus + also projects back to the vestibular nucleus to influence the vestibular spinal pathways.

cerebellum

The cerebellum is involved in adaptively fine-tuning the _____/_____/_____ based on changes in sensory function (clinically or experimentally)

VOR, VCR, VSR

Which brain structure is involved in determining vestibular signals generated from self-motion vs. external forces (e.g. car)

cerebellum

Instead of a single “primary vestibular cortex” as the somatosensory, visual, and auditory cortical pathways, there is a distributed set of cortical areas in the ____________ lobe, where neurons are modulated by vestibular inputs.

parietal

The __________________ contains neurons that integrate vestibular, visual optic flow and somatosensory information.

parietoinsular vestibular cortex (PIVC)

What is the vestibular head impulse test? What occurs normally? What is an indication of an abnormality?

way to test vestibular function through fast rotation of the head

nystagmus refers to the eye movements that occur under continuous vestibular stimulation

• there is a SLOW phase in the direction counter to head rotation (the VOR) then when the eye reaches the end of its range of motion, it flicks back quickly (FAST phase)

catch-up (corrective) saccades to the left when the head is rotated to the right = right side VOR abnormality

What is caloric vestibular testing?

method to test the vestibular system by using water of different temperatures and irrigating it into each ear, the temperature difference causes nystagmus of the eyes (rapid side-to-side eye movements)

What is rotational/translational vestibular testing?

a common method of testing vestibular function by testing perceptual sensitivity to robotic motion devices

What is electric vestibular stimulation?

test that delivers electrical current behind the ears; causes a physical perturbation to balance control through the vestibular spinal reflex (VSR) pathway

What is the center of gravity?

the average position of an object’s mass, which gets pulled on by gravity

What is the base of support?

the area bounded by the points of contact between the feet and the ground

Gravity applies _______________ to the joints which need to be counteracted to remain upright.

“toppling” torques

Controlling standing balance involves keeping the center of gravity ____________ the base of support.

within

What is ground reaction force?

the force of the floor pressing back against the foot, cane, etc.

What is the center of pressure?

represents the summed (total) ground reaction force (calculated from the ground reaction forces)

example: orthotic machine thing at the pharmacy that measures the pressure points of your feet (foot mapping)

What is the Romberg test?

test that challenges balance and is used to measure postural stability in the clinic — people tend to adopt a particular control strategy that involves making postural adjustments at one or multiple joints (hip-only, ankle-only, combined hip-ankle strategy)

In order to control standing balance, the _____________ continuously makes small postural adjustments,

motor system

When standing still, we are constantly swaying (small, slow movements) in the ____________ and ____________ planes.

anterolateral, mediolateral

The pressure we apply under the feet (CoP) is said to “herd” or “corral” the more slow movement of the body’s CoG. What does this mean?

your body is constantly adjusting its center of pressure to keep your center of gravity within your base of support

________________ is a simplified model that captures the major aspects of standing balance (body segments moving to keep the center of gravity within the base of support)

Inverted pendulum

Sensory organization tests use ____________________ to manipulate or disrupt sensory feedback for postural control. What does this term mean?

sway referencing, means that the machine is moving along with your postural sway

What is the gait cycle?

the rhythmic pattern of movements made when walking/running and consists of two main phases, stance + swing (heel strike to heel strike of same foot = 1 cycle)

What is bi-pedal walking?

mode of locomotion in which the legs move in antiphase — one foot or the other is in contact with the ground at all times, and both feet are in contact with the ground briefly (double support)

What is bi-pedal running?

mode of locomotion in which both legs move in anti-phase — both feet are never on the ground at the same time, and there are periods where neither foot is on the ground at the same time (flight periods)

________________ varies periodically across the gait cycle and drives gat kinematics.

Muscle activity (EMG)

EMG is ____________ and _____________ in running than in walking because ____________ motor units are involved.

greater, earlier, larger

What are CPG’s (central pattern generators)?

spinal circuits controlling the rhythmic movement of the legs during locomotion

The ________________ and ________________ relay tonic excitatory inputs that activate spinal locomotor systems (CPG’s).

mesencephalic locomotor region (MLR), medial reticular formation (MRF)

When you stimulate the MLR, spinal locomotor circuits (CPGs) are activated. Higher intensities of stimulation lead to _____________ locomotion.

faster

When walking, ___________ vision is what detects an obstacle in front of you. This is because _____________ vision is sensitive to ______________ (______________).

peripheral, peripheral, visual motion, optic flow

In treadmill walking experiments, foot placement variability ____________ without vision.

increases