Neurophysiology Flashcards
What is spatial summation?
When additional input from several other presynaptic cells through other synapses lead to an action potential.
What is temporal summation?
When recurrent stimulation by same synapse results in action potential.
What are the neurochemical mediators of increased appetite?
Ghrelin
Neuropeptide Y
What are the neurochemical mediators of satiety?
Leptin
Cholecystokinin
Serotonin
Which orexigenic substance is produced outside of the CNS?
Ghrelin
Where is Ghrelin produced?
Gastric mucosa
What happens to dopamine receptors in obesity?
D2 receptors are reduced in striatum.
What are the centres for temperature in the hypothalamus?
Preoptic anterior hypothalamus
Posterior hypothalamus
What is the hypothermic centre called?
Preoptic anterior hypothalamus
What is the hyperthermic centre called?
Posterior hypothalamus
What type of lesion reduces diurnal temperature variation?
Lesions in median eminence
Which subcortical centre plays a role in pain?
Thalamus
Which fibres carry pain sensation?
Unmyelinated C fibres
Sparsely myelinated A-delta fibres
What happens once pain sensation arrives at dorsal horn of spinal cord
Fast transmission via lateral spinothalamic route
Slow transmission via reticulothalamic tract
Purpose of transmission of pain along lateral spinothalamic tract?
Aids localization of pain
Purpose of slow transmission of pain sensation via reticulothalamic tract?
Aids subjective sensation
Which receptors modulate pain sensitivity?
Opioid receptors in dorsal horn + periaqueductal grey matter (brain stem)
Which fibres modulate pain perception?
Descending fibres from serotonergic raphe nuclei
How does thalamic pain syndrome occur?
Stroke involving thalamoperforating branches of posterior cerebral artery.
Which parts of the brain are involved in thirst
Subfornical organ
Organum vasculosum of the lamina terminalis
Hypothalamic paraventricular nucleus
Which neurotransmitter is used to propagate thirst signals?
Angiotensin II
How does hypotension stimulate thirst
Via baroreceptors on aorta and carotid
Organic/anatomical cause of SIADH?
Damage to paraventricular and supraoptic hypothalamic nuclei
Symptoms in Kluver-Bucy syndrome?
Decreased aggressive behaviour.
Prominent oral exploratory behaviour and hypersexuality.
Hypermetamorphosis (objects repeatedly examined as if novel)
What is the cause of Laurence-Moon-Biedl Syndrome?
Autosomal recessive with genetic locus at 11q13 in most cases
Symptoms in Laurence-Mood-Biedl Syndrome?
Obesity Hypogonadism Low IQ Retinitis pigmentosa Polydactyly Diabetes insipidus
When does neuronal migration take place?
First 6 months of gestation
What is heteropia?
Abnormalities in neuronal migration due to neurons failing to reach cortex and residing in ectopic positions.
When does myelination begin?
4th gestational month
When is myelination complete?
2 years postnatal
When does synaptogenesis occur rapidly?
From second trimester through to the first ten years of life.
When is the peak of synaptogenesis?
First 2 years postnatally.
What can we use to study neuronal numbers?
Density of D2 receptors
Rate of dopamine receptor loss in adults?
2.2% reduction per decade
Rate of D2 receptor loss in schizophrenia?
6% loss per decade
Where are neurohormones produced which regulate hormones from anterior lobe of the pituitary gland?
Parvocellular neurons of hypothalamus.
Where are the two hormones synthesized which are released from the posterior lobe of the pituitary gland?
Magnocellular cells of supraoptic nuclei
Paraventricular nuclei of hypothalamus
What increases GH release?
Exercise
Sleep
Stress
What facilitates release of prolactin?
Thyrotrophin releasing hormone
During which activities are prolactin released?
Pregnancy
Nursing
Sleep
Exercise
What does Vasopressin play a role in?
Attention
Memory
Learning
When is vasopressin release increased?
Pain
Stress
Exercise
What drugs increase vasopressin?
Morphine
Nicotine
Barbiturates
What drug decreases vasopressin release?
Alcohol
Which hormone inhibits growth hormone?
Somatostatin
What happens if exogenous administration of TRH is given to depressed patients?
Blunted response to TRH
What activates nerve growth factor genes in early development?
T3
What happens to the hypothalamic-pituitary-adrenal axis in chronic stress?
Feedback fails
Continuous excess of cortisol produced, leading to deleterious consequences to hippocampus where there are glucocorticoid receptors.
Decreased hippocampal neurogenesis with atrophy of hippocampal dendrites.
Disrupts long-term potentiation and impaired memory performance.
What compensations occur if hippocampal shrinkage occurs in chronic stress?
Compensatory increase in dendritic arborization of neurons in basolateral amygdala, contributing to memory bias towards negative events in chronic stress.
What physical conditions can lead to DST non-suppression?
Pregnancy
Severe weight loss
ETOH
Hepatic enzyme inducers
What drugs decrease melatonin synthesis?
Beta-antangonists such as propranolol
What regulates circadian rhythms?
Melatonin
What hormone is increased at the start of sleep?
Testosterone
What hormone is increased at slow wave sleep?
GH
SST
What hormone is reduced in REM sleep?
Melatonin
What hormone is increased in early morning sleep?
Prolactin
What type of dreams occur in REM sleep?
Illogical
Bizarre
What is normal REM latency in adults?
90 minutes
How much of adult sleep is N-REM?
75%
What is slow wave sleep?
Stages 3 and 4 of N-REM sleep.
What happens in Stage 1 NREM?
Low voltage theta activity, sharp V waves.
5% of sleep
What happens in Stage 2 NREM?
45% of sleep
Development of sleep spindles and K complexes
What happens in Stage 3 sleep?
12% of sleep
<50% delta waves
What happens in stage 4 NREM?
13% of sleep
>50% delta waves
Physiological functions at lowest
Features of NREM sleep
Increased parasympathetic activity - low HR and systolic BP, RR, cerebral blood flow.
Abolition of tendon reflexes.
Upward ocular deviation with few or no movements
Reduced recollection of dreams if awaken.
What does EEG show in REM sleep?
Low-voltage, mixed frequency (theta and slow alpha) activity similar to awake state.
Saw tooth waves.
What are sleep spindles?
Waves with upper alpha or lower beta frequency
Where are K complexes most prominent?
Bi-frontal regions
Where are K complexes mediated from?
Thalamocortical circuitry.
What happens to sleep in old age?
Absolute reduction in both slow-wave and REM sleep.
Increase in frequecy of awakenings after sleep onset
What synchronizes the suprachiasmatic nucleus?
Signals from retina
Reset each day by signals of light.
What can reset the SCN?
signals of light from retina
pineal melatonin secretion during darkness
What is the sleep switch nucleus?
Ventrolateral preoptic nucleus
What must be inhibited for people to wake up?
Ventrolateral preoptic nucleus
What causes inhibition of VLPO?
Negative feedback from monoaminergic system.
Switching to arousal is then stabilised by orexin/hypocretin neurons in hypothalamus.
Where are histaminergic neurotransmitters in ascending RAS?
Tuberomammillary nucleus
Function of cholinergic midbrain-pons nuclei
REM on neurons - activation brings on REM sleep.
Function of noradrenergic neurotransmitter in locus coeruleus?
REM off neurons - activation reduces REM sleep.
Function of dopaminergic neurotransmitters in periaquaductal gray matter?
D2 enhances REM sleep
Function of serotonergic neurotransmitter in raphe nuclei?
5HT2 stimulation maintains arousal
Affect of ETOH on sleep
Increases SWS (chronic use causes loss) Reduces initial REM but increases second half REM
Affect of ETOH withdrawal on sleep
Loss of SWS
Increased REM
Intense REM rebound
Affect of anxiety disorders on sleep
Increased stage 1 (light sleep)
Reduced REM
Normal REM latency
Reduced slow wave sleep
Affect of benzo on sleep
Decreased sleep latency Increased sleep time Reduced stage 1 sleep Increased stage 2 sleep Reduce REM and SWS Prevent transition from lighter stage 2 sleep into deep, restorative stage 3 and 4 sleep.
Affect of cannabis on sleep
Increased SWS
Suppress REM
Affect of depression on sleep
Loss of SWS slow wave sleep (first half)
Increased REM, leading on to early awakening
Reduced REM latency
Affect of lithium on sleep
Suppresses REM
Increases REM latency
Increases SWS
Affect of SSRIs on sleep
Alerting due to 5HT2 stimulation
May reduce REM latency
Affect of tricyclics on sleep
REM suppression - especially clomipramine
Increased SWS and stage 1 sleep
Where is beta waves seen?
Frontal, central position in normal waking EEG
Where is alpha wave seen?
Dominant brain wave frequency when eyes are closed and relaxing occipitoparietal predilection.
Which waves are dominant in EEG when asleep?
Theta
Which waves are dominant in newborns?
Delta
Theta
What is seen in EEG during absence seizure?
Regular 3 Hz complexes
What is seen in EEGs in Angelmans syndrome?
Noted by age of 2
Prolonged runs of high amplitude 2-3 Hz frontal activity with superimposed interictal epileptiform discharges.
EEG in CJD
Generalised periodic 1-2 Hz sharp waves in 90% of patients with sporadic CJD.
Not in variant form.
EEG in herpes simplex encephalitis
Episodic discharges recurring every 1-3 seconds with variable focal waves over Temporal areas
EEG in metabolic and endocrine disorders
Diffuse, generalised slowing.
Triphasic waves 1.5-3 per second high-voltage slow-waves (particularly in hepatic encephalopathy)
What is a hallmark of seizure on EEG?
Epileptiform discharges seen interictally
Effect of antipsychotics on EEG?
Slowing of beta activity
Increase in alpha, theta and delta
Effect of antidepressants on EEG?
Slowing of beta activity
Increase in alpha, theta and delta
Effect of lithium on EEG?
Slowing of alpha or paroxysmal activity
Effect of benzos on EEG?
Increased beta
Decreased alpha
What can EEG and MEG measure?
MEG: selectively measure activity in sulci
EEG: measure activity in both sulci and at top of cortical gyri
What is decreased P300 amplitude related to in MH
Biological trait marker in schizophrenia
