Physiology

Question 1

Corpuscle Somatosensory Stimuli

Answer 1

Meissner - light flutter
Merkel Disk - pressure
Pacinian - vibration
Ruffini - skin stretch
Free nerve ending - pain, itch and tickle, temp (PITT)

Question 2

Nocicepter Fibre Types

Answer 2

Thermal nociceptors – peripheral endings of small diameter thinly myelinated axons

Mechanical nociceptors - thinly myelinated axons

Polymodal nociceptors – at ends of small diameter, unmyelinated C axons

Signals of touch and proprioception reach the SC and brain centres sooner than noxious or thermal signals.

Question 3

Stretch reflex synapse number

Answer 3

Reciprocal is polysynaptic but excitatory one is monosynaptic

Question 4

Sensory fibres dynamic static

Answer 4

1a dynamic and static

2 static

Question 5

Cerebral Blood Vessel Innervation

Answer 5

The pial arteries receive extrinsic innervation from the Peripheral Nervous System. Nerves originate in the superior cervical (SCG), sphenopalatine (SPG), or otic (OG) or trigeminal (TG) ganglion. Contrary to that, arteries within the brain parenchyma, or the microcirculation, receive intrinsic inniveration; these nerves originate in the central nervous system. Cortical microvessels receive norepinephrine (NA), serotonin (5-HT), acetylcholine (ACh), or GABAergic afferents from subcortical neurons from the locus coeruleus, raphe nucleus, basal forebrain, or local cortical interneurons respectively (also thalamus and glu).

Question 6

Autoregulation Failure

Answer 6

Autoregulation fails in traumatic brain injury, in stroke (mainly in the penumbra and in the tissue affected by stroke, around space occupying lesions; in that case CBF begins to change linearly with MAP.

Question 7

Blood-brain vs Blood-CSF Barriers

Answer 7

Tight junctions are in:
Blood-brain: endothelial cells
Blood-CSF: choroidal cells

Question 8

Pressure required for CSF movement into blood

Answer 8

CSF moves into venous blood when CSF pressure is 1.5 mmHg or more higher than venous blood pressure

Question 9

What tract inhibits anti-gravity muscles?

Answer 9

Rubrospinal tract

Question 10

Tonic neck reflexes

Answer 10

• Flex neck - forelimbs flex and hind limbs extend
• Extend neck - forelimbs extends and hind limbs flex
• Turn neck - limbs on same side extend and contralaterally flex

Question 11

Kinocilium orientation in otolith organs

Answer 11

Saccule - away from striola
Utricle - towards striola
(Mirror image on either side of striola, otolithic membranes change orientation in relation to head)

Question 12

Structures in the brain regulating thirst

Answer 12

Hypothalamus (PVN, LN, SON)
Organum Vasculosum Laminae Terminalis (OVLT)
Subfornical Organ (SFO)

Question 13

Burst vs Single-spike APs

Answer 13

When TRN neurons are depolarised, their firing pattern converts from burst mode (sleeping activity) to single-spike mode
(waking activity).

Question 14

Childhood absence seizures (petit mal)

Answer 14

Begin abruptly, usually last less than 10 seconds
Staring and sudden cessation of all motor activity, loss of awareness but not loss of posture
EEG: 3 Hz spike-and-wave pattern in all cerebral areas simultaneously
No postictal symptoms
No aura before seizure
Preceded and followed by normal background activity

Question 15

Frontoparietal areas activated for external and internal stimuli

Answer 15

External: lateral
Internal: medial
When one is active the other is suppressed

Question 16

Flip-flop model

Answer 16

Sleep-promoting cell groups are themselves inhibited by the arousal system. The direct mutual inhibition between VLPO and monoaminergic cell groups (e.g. LC, TMN, and Raphe) forms a classic flip-flop switch, which produces sharp transitions in state.

Question 17

Which part of the hypothalamus usually controls autonomic function and what are the six major functions of the hypothalamus?

Answer 17

Posterior hypothalamus

Functions of the hypothalamus:
1. Blood pressure & electrolyte composition: Regulation of thirst, salt appetite,
drinking behavior, autonomic vasomotor control
2. Energy metabolism: Regulation of hunger and feeding behavior, control of digestion, Release of hormones (glucocorticoids, GH, and TSH).
3. Reproductive behaviors: Modulation of the reproductive organs and endocrine regulation of the gonads
4. Body temperature: Control of autonomic body heat conservation/loss mechanisms
5. Defensive behavior: Regulation of the stress response to threats in the environment
6. Sleep-wake cycle: Regulation of the sleep-wake cycle and levels of arousal when awake.

Question 18

Which triptan causes flushing?

Answer 18

Zolmitriptan (given orally too)

Question 19

Main NT in AAC

Answer 19

Dopamine

Question 20

Visual and auditory streams

Answer 20

Visual - 
dorsal stream (to parietal AC): position, motion, speed
Dorsodorsal in SPL for control of movements and ventrodorsal for visuomotor transformations

ventral stream (to temporal AC) : color, shape, texture

Auditory -
Dorsal pathways: motor and spatial functions

Ventral pathways: recognition functions

Question 21

Apperceptive and associative agnosia locations

Answer 21

Temporal lobe (associative rostral to apperceptive)

Question 22

Cerebellar feedforward model

Answer 22

Internal forward model

Predictive and dependent on context and past experience

Question 23

Cerebellar circuit golgi and lugaro

Answer 23

GCs activate golgi through basal and apical dendrites
Lugaro cells are inhibitory interneurons relaying on golgi
Golgi cells interact with each other through gap junctions

Question 24

Connection between red nucleus and olivary nucelus

Answer 24

Remember it

Question 25

Motor homunculus specific region patterns

Answer 25

Distal outwards proximal inwards

Neurons for same direction movement usually dispersed (adjacent usually for different directions)

Question 26

Physiology neuron activity arterial dilation

Answer 26

Direct - ?
Pyramidal - PGE2
Interneuron - NO and GABA
All neurons via NMDA
Astrocyte (indirect and slow and prolonged, can be activated by others via glutamate) - Gives AA to give EET and PG (dilation) and 20-HETE (constriction), also k+ for dilation
Astrocyte via mGluR1 (but both nmda and mGluR1 increase iCa2+)
Similar letters (way to memorise)

Question 27

Compensation to ischaemia

Answer 27

Increase BV then OEF then reduce CMR