Physiology Flashcards
Corpuscle Somatosensory Stimuli
Meissner - light flutter Merkel Disk - pressure Pacinian - vibration Ruffini - skin stretch Free nerve ending - pain, itch and tickle, temp (PITT)
Nocicepter Fibre Types
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.
Stretch reflex synapse number
Reciprocal is polysynaptic but excitatory one is monosynaptic
Sensory fibres dynamic static
1a dynamic and static
2 static
Cerebral Blood Vessel Innervation
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).
Autoregulation Failure
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.
Blood-brain vs Blood-CSF Barriers
Tight junctions are in:
Blood-brain: endothelial cells
Blood-CSF: choroidal cells
Pressure required for CSF movement into blood
CSF moves into venous blood when CSF pressure is 1.5 mmHg or more higher than venous blood pressure
What tract inhibits anti-gravity muscles?
Rubrospinal tract
Tonic neck reflexes
- 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
Kinocilium orientation in otolith organs
Saccule - away from striola
Utricle - towards striola
(Mirror image on either side of striola, otolithic membranes change orientation in relation to head)
Structures in the brain regulating thirst
Hypothalamus (PVN, LN, SON)
Organum Vasculosum Laminae Terminalis (OVLT)
Subfornical Organ (SFO)
Burst vs Single-spike APs
When TRN neurons are depolarised, their firing pattern converts from burst mode (sleeping activity) to single-spike mode
(waking activity).
Childhood absence seizures (petit mal)
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
Frontoparietal areas activated for external and internal stimuli
External: lateral
Internal: medial
When one is active the other is suppressed
Flip-flop model
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.
Which part of the hypothalamus usually controls autonomic function and what are the six major functions of the hypothalamus?
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.
Which triptan causes flushing?
Zolmitriptan (given orally too)
Main NT in AAC
Dopamine
Visual and auditory streams
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
Apperceptive and associative agnosia locations
Temporal lobe (associative rostral to apperceptive)
Cerebellar feedforward model
Internal forward model
Predictive and dependent on context and past experience
Cerebellar circuit golgi and lugaro
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
Connection between red nucleus and olivary nucelus
Remember it
Motor homunculus specific region patterns
Distal outwards proximal inwards
Neurons for same direction movement usually dispersed (adjacent usually for different directions)
Physiology neuron activity arterial dilation
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)
Compensation to ischaemia
Increase BV then OEF then reduce CMR
