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AHS2 > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the medial descending tracts?

A

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

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2
Q

Which two medial descending tracts control axial and proximal musculature?

A
  • Vestibulospinal tract

- Reticulospinal tract

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3
Q

What else do the medial descending tracts control?

A
  • posture

- locomotion and reflexes

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4
Q

How far does the tectospinal tract project?

A

-cervical level of the spinal cord.

projects from midbrain

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5
Q

What does the tectospinal tract control?

A

reflex head orientation in response to visual or auditory stimuli

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6
Q

What are the lateral descending tracts?

A

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

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7
Q

What do the lateral D tracts control?

A
  • spinal circuits of distal musculature

- goal-directed movements

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8
Q

What is the major lateral descending tract in most mammals?

A

-Rubrospinal

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9
Q

Where does the rubrospinal tract come from?

A

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

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10
Q

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

A

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

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11
Q

What indicates a disorder of the lower reflex arc?

A

weakness of absence of the stretch reflex

lower motor-neurone dysfunction

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12
Q

What can disorders of the central descending control lead to?

A

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

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13
Q

What can happen with forebrain damage?

A

spasticity

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14
Q

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

A

decerebrate rigidity

Hyperactivity in the limb extensors

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15
Q

What happens when there are lesions at the spinal level?

A

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

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16
Q

Which reflex opposes changes in muscle length?

A

-the stretch relfelx

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17
Q

How can the body adapt to increase postural stability?

A

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

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18
Q

What does locomotion in terrestrial animals need to be?

A
  • a rhythmic pattern of swing phase and stance phases which align with flexor and extensor phases of muscle groups respectively.
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19
Q

What is a central pattern generator?

A

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

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20
Q

What is switched off during swing phase?

A

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

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21
Q

What is the mesencephalic locomotor region?

A

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

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22
Q

How does the visual guidance of locomotion work?

A
  • feedforward control

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

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23
Q

What happens during feedforward of locomotion?

A

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

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24
Q

What would happen if the motor cortex is damaged?

A

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

25
Q

Cortical motor areas

A
  • supplementary motor area
  • primary motor cortex
  • premotor cortex
26
Q

where does the primary motor cortex receive sensory inputs?

A
  • primary somatosensory cortex

- posterior parietal association cortex

27
Q

What stimulates the premotor cortex and the supplementary motor area?

A
  • more complex movements around joints

- coordinated movements of multiple parts of the body

28
Q

What does the primary motor cortex do?

A
  • execution of movements

- control of force and direction, not position of limbs

29
Q

What does damage of the primary motor cortex lead to?

A

weakness and reluctance to move affected limbs - paresis

30
Q

What does the lateral premotor cortex do?

A

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

31
Q

What does damage to the lateral premotor cortex do?

A

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

32
Q

What does the supplementary motor area do?

A

planning of movement- self willed via basal ganglia loop

learned sequence of movements

33
Q

Damage of supplementary motor area?

A

leads to deficits in coordinating voluntary movements between limbs

34
Q

Where would you find the basal ganglia?

A

-in the telencephalon

35
Q

Where do basal ganglion get their input?

A

from cortex

36
Q

Where does output from basal ganglia go?

A

to cortex via thalamus

37
Q

What are the basal ganglia involved with?

A
  • initiation of self-willed movements
  • disinhibit thalamocortical circuits: desired and internally motivated movements are initiated
  • suppressing undesirable movements
38
Q

What is the overall role of the basal ganglia?

A

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

39
Q

What are the 4 main circuits for motor action?

A
  • 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
40
Q

What does the vestibulo-ocular reflex do?

A

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

41
Q

What do climbing fibres convey?

A

-error signals

42
Q

What does the climbing fibres input do?

A

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

43
Q

What does a change in purkinje cell output do?

A

Recalibrates the VOR

44
Q

What is a symptom of disorders with the VOR system?

A

nystagmus

45
Q

What is nystagmus?

A

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

46
Q

What does the vestibulocerebellum regulate?

A

balance and eye movements via its output to the vestibular nuclei

47
Q

What does damage to the vestibulocerebellum lead to?

A
  • inaccurate stabilisation of gaze during head movements
  • nystagmus
  • balance problems with wide stance and unsteady gait
48
Q

What is cerebellar hypoplasia?

A

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

49
Q

What are the inputs and outputs of the vestibulocerebellum?

A

inputs: vestibular system, vestibular nuclei
outputs: vestibular nuclei

50
Q

What are the inputs and outputs of the Spinocerebellum?

A

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

51
Q

What does the spinocerebellum do?

A
  • calibrates the accuracy of ongoing movements via the lateral descending tracts
  • regulates ongoing movement ipsilaterally, including saccadic eye movements
52
Q

What happens when there is damage to the spinocerebellum?

A

cerebellar ataxia

53
Q

Where is the spinocerebellum found?

A

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

54
Q

What are the inputs and outputs of the cerebrocerebellum?

A

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

55
Q

What is the function of the cerebrocerebellum?

A

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

56
Q

What happens when there is damage to the cerebrocerebellum?

A
  • disruption in timing of movements

- disruption of learning new motor skills and adaptation of current ones

57
Q

What stimuli does the hypothalamus integrate?

A

internal and external info about the environment

  • blood-borne stimuli
  • neural inputs from the brainstem
  • neural inputs from the forebrain
58
Q

What type of responses does the hypothalamus produce?

A

coordinated internal and external responses

  • autonomic
  • endocrine
  • behavioural

AHS2 (5 decks)

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