Physiology

Question 1

What are the medial descending tracts?

Answer 1

motor tracts that convey influences from UMN to spinal motor control circuits
on the medial aspect of the brain stem etc

Question 2

Which two medial descending tracts control axial and proximal musculature?

Answer 2

• Vestibulospinal tract

- Reticulospinal tract

Question 3

What else do the medial descending tracts control?

Answer 3

• posture

- locomotion and reflexes

Question 4

How far does the tectospinal tract project?

Answer 4

-cervical level of the spinal cord.

projects from midbrain

Question 5

What does the tectospinal tract control?

Answer 5

reflex head orientation in response to visual or auditory stimuli

Question 6

What are the lateral descending tracts?

Answer 6

motor tracts that convey influences from UMN to spinal motor control circuits
on the lateral aspect of the brain stem

Question 7

What do the lateral D tracts control?

Answer 7

• spinal circuits of distal musculature

- goal-directed movements

Question 8

What is the major lateral descending tract in most mammals?

Answer 8

-Rubrospinal

Question 9

Where does the rubrospinal tract come from?

Answer 9

red nucleus in midbrain and input from lateral cerebellum and motor cortex

Question 10

What is the major lateral descending tract in apes and carnivores?

Answer 10

lateral corticospinal tract from the large cortical neurones
it’s a pyramidal tract
axons from cortical pyramidal cells.

Question 11

What indicates a disorder of the lower reflex arc?

Answer 11

weakness of absence of the stretch reflex

lower motor-neurone dysfunction

Question 12

What can disorders of the central descending control lead to?

Answer 12

hyperactive or hypoactive stretch reflexes and abnormal muscle tone
upper motor neurone dysfunction

Question 13

What can happen with forebrain damage?

Answer 13

spasticity

Question 14

What happens when there’s damage at the midbrain level?

Answer 14

decerebrate rigidity

Hyperactivity in the limb extensors

Question 15

What happens when there are lesions at the spinal level?

Answer 15

spinal shock- all reflexes below the point of the lesion are suppressed

Question 16

Which reflex opposes changes in muscle length?

Answer 16

-the stretch relfelx

Question 17

How can the body adapt to increase postural stability?

Answer 17

-reflexes need to be calibrated continuously to ensure they are effective.
role of the cerebellum

Question 18

What does locomotion in terrestrial animals need to be?

Answer 18

• a rhythmic pattern of swing phase and stance phases which align with flexor and extensor phases of muscle groups respectively.

Question 19

What is a central pattern generator?

Answer 19

found in the spinal cord
generate rhythmic patterns of extensor and flexor neural activity
input from the reticulospinal tract
flip flop arrangment based on mutual inhibition

Question 20

What is switched off during swing phase?

Answer 20

the flexor activity inhibits extensor activity during swing phase via an inhibitory interneurone

Question 21

What is the mesencephalic locomotor region?

Answer 21

drives locomotion in the midbrain
projection: through the medial reticular formation and reticulospinal tract
increased stimulation means increased speed of locomotion
as speed increases= gait change

Question 22

How does the visual guidance of locomotion work?

Answer 22

• feedforward control

- adjustments of step cycle by descending projections from the motor cortex. with increased firing of pyramidal neurones

Question 23

What happens during feedforward of locomotion?

Answer 23

from the visual cortex and allows the locomotion system to predict upcoming obstacles and variations in terrain.

Question 24

What would happen if the motor cortex is damaged?

Answer 24

able to walk on smooth surfaces but not skilled in walking which involves a high degree of visuomotor coordination.

Question 25

Cortical motor areas

Answer 25

- supplementary motor area - primary motor cortex - premotor cortex

Question 26

where does the primary motor cortex receive sensory inputs?

Answer 26

- primary somatosensory cortex | - posterior parietal association cortex

Question 27

What stimulates the premotor cortex and the supplementary motor area?

Answer 27

- more complex movements around joints | - coordinated movements of multiple parts of the body

Question 28

What does the primary motor cortex do?

Answer 28

- execution of movements | - control of force and direction, not position of limbs

Question 29

What does damage of the primary motor cortex lead to?

Answer 29

weakness and reluctance to move affected limbs - paresis

Question 30

What does the lateral premotor cortex do?

Answer 30

-planning of movements in response to external cues via the cerebellar loop

Question 31

What does damage to the lateral premotor cortex do?

Answer 31

deficits ion complex movements, including difficulty associating a sensory stimulus with a motor response

Question 32

What does the supplementary motor area do?

Answer 32

planning of movement- self willed via basal ganglia loop | learned sequence of movements

Question 33

Damage of supplementary motor area?

Answer 33

leads to deficits in coordinating voluntary movements between limbs

Question 34

Where would you find the basal ganglia?

Answer 34

-in the telencephalon

Question 35

Where do basal ganglion get their input?

Answer 35

from cortex

Question 36

Where does output from basal ganglia go?

Answer 36

to cortex via thalamus

Question 37

What are the basal ganglia involved with?

Answer 37

- initiation of self-willed movements - disinhibit thalamocortical circuits: desired and internally motivated movements are initiated - suppressing undesirable movements

Question 38

What is the overall role of the basal ganglia?

Answer 38

select appropriate courses of action based on current context and past experience

Question 39

What are the 4 main circuits for motor action?

Answer 39

- skeletomotor circuit to/from motor cortical areas - oculomotor circuit to/from frontal cortex ad supplementary eye fields - prefrontal circuit to/from lateral prefrontal and lateral orbitofrontal cortices - limbic circuit to/from cingulate and medial orbitofrontal cortices

Question 40

What does the vestibulo-ocular reflex do?

Answer 40

stabilises retinal image when the head moves otherwise the image would blur

Question 41

What do climbing fibres convey?

Answer 41

-error signals

Question 42

What does the climbing fibres input do?

Answer 42

strongly depolarises Purkinje cells leading to the plasticity of parallel fibres synapsing

Question 43

What does a change in purkinje cell output do?

Answer 43

Recalibrates the VOR

Question 44

What is a symptom of disorders with the VOR system?

Answer 44

nystagmus

Question 45

What is nystagmus?

Answer 45

Nystagmus is an involuntary rhythmic side-to-side, up and down or circular motion of the eyes that occurs with a variety of conditions. jerky movements of the eyes

Question 46

What does the vestibulocerebellum regulate?

Answer 46

balance and eye movements via its output to the vestibular nuclei

Question 47

What does damage to the vestibulocerebellum lead to?

Answer 47

- inaccurate stabilisation of gaze during head movements - nystagmus - balance problems with wide stance and unsteady gait

Question 48

What is cerebellar hypoplasia?

Answer 48

congenital condition when the cerebellum fails to develop properly compensation for it's postural deficits can develop over time

Question 49

What are the inputs and outputs of the vestibulocerebellum?

Answer 49

inputs: vestibular system, vestibular nuclei outputs: vestibular nuclei

Question 50

What are the inputs and outputs of the Spinocerebellum?

Answer 50

inputs: spinal cord, visual system, auditory system, vestibular system outputs: reticular formation, vestibular nuclei, oculomotor nuclei, primary motor cortex, red nucleus

Question 51

What does the spinocerebellum do?

Answer 51

- calibrates the accuracy of ongoing movements via the lateral descending tracts - regulates ongoing movement ipsilaterally, including saccadic eye movements

Question 52

What happens when there is damage to the spinocerebellum?

Answer 52

cerebellar ataxia

Question 53

Where is the spinocerebellum found?

Answer 53

In the vermis and the intermediate hemispheres (the paravermis) either side of the vermis

Question 54

What are the inputs and outputs of the cerebrocerebellum?

Answer 54

Inputs: parietal cortex, frontal cortex, motor cortical areas outputs: primary motor cortex, lateral premotor area

Question 55

What is the function of the cerebrocerebellum?

Answer 55

involved in planning of movements and refinement of the motor model in response to parametric feedback mental rehearsal of actions, motor learning

Question 56

What happens when there is damage to the cerebrocerebellum?

Answer 56

- disruption in timing of movements | - disruption of learning new motor skills and adaptation of current ones

Question 57

What stimuli does the hypothalamus integrate?

Answer 57

internal and external info about the environment - blood-borne stimuli - neural inputs from the brainstem - neural inputs from the forebrain

Question 58

What type of responses does the hypothalamus produce?

Answer 58

coordinated internal and external responses - autonomic - endocrine - behavioural