Basic neurophysiology Flashcards
Intracellular resting membrane potential
-70mV
Intracellular threshold potential
-55mV
Channels that open at the intracellular threshold potential of -55mV
Na+ channels
Result of the Na+ influx caused by Na+ channels opening
Reversal of the membrane potential to +40mV
Effect of the membrane potential reaching +40mV
Na+ channels close
Voltage gated K+ channels open
K+ ions move out of the axon
Cell membrane is repolarised
Term for a junction between two nerve cells
Synapse
Three types of synapses in the nervous system
Chemical synapse
Electrical synapse
Conjoint synapse
Features of a chemical synapse
Presynaptic neuron is stimulated and releases a chemical molecule
Molecule acts on the postsynaptic neuron to produce an effect, or to carry the impulse further along to a further neuron
Types of chemical synapse depending on their effect on the postsynaptic neuron
Excitatory
Inhibitory
Effect of excitatory chemical synapses on postsynaptic neurons
Depolarises
Effect of inhibitory chemical synapses on postsynaptic neurons
Hyperpolarises
Process where a postsynaptic depolarisation is not enough by itself to induce an action potential in the cell, but with further stimulation an action potential can be generated
Facilitation
Type of facilitation where input from several different presynaptic cells leads to an action potential
Spatial summation
Type of facilitation where recurrent stimulation from the same presynaptic neuron results in an action potential
Temporal summation
Features of an electrical synapse
Response is generated by electrical communication without the need for chemical molecules to be exchanged
Features of a conjoint synapse
Both electrical and chemical properties
Part of the body which acts as the satiety centre
Ventromedial hypothalamus
Part of the body which acts as the feeding centre
Lateral hypothalamus
Neurochemicals which cause increased appetite
Ghrelin
Neuropeptide Y
Neurochemicals which decrease appetite
Leptin
Cholecystokinin
Serotonin
Part of the body where ghrelin is synthesised
Gastric mucosa
Cells which synthesise ghrelin
Adipose cells
Part of the body where activity is increased by food and food cues
Nucleus accumbens
Type of activity produced in the nucleus accumbens by food and food cues
Dopaminergic activity
Part of the body which acts as the hypothermic centre
Preoptic anterior hypothalamus
Part of the body which acts as the hyperthermic centre
Posterior hypothalamus
Effects of stimulating the preoptic anterior hypothalamus
Sweating
Vasodilation
Hyothermia
Effects of stimulating the posterior hypothalamus
Shivers
Vasoconstriction
Hyperthermia
Part of the body where lesions can interrupt normal diurnal temperature variation
Median eminence (a midline swelling on the inferior surface of the hypothalamus)
Cause of malignant hyperthermia caused by drugs
Abnormal excitation-contraction in skeletal muscles
Part of the brain which is involved in pain perception
Thalamus
Types of fibres which carry pain sensation to the spinal cord
C fibres
A delta fibres
Difference in myelination between C fibres and A delta fibres
C fibres are unmyelinated
A delta fibres are myelinated
Difference in speed of transmission between C fibres and A delta fibres
A delta fibres send pain sensation quicker
Specialised receptors in the skin which are able to detect pain
Nociceptors
Pathway in the spinal cord which carries pain and temperature sensation
Lateral spinothalamic tract
Pathway in the spinal cord which carries crude touch and pressure sensation
Anterior spinothalamic tract
Blood vessel involved in a stroke causing thalamic pain syndrome
Thalamoperforating branches of the posterior cerebral artery
Features of thalamic pain syndrome
Contralateral loss of sensation
Contralateral burning and tingling with allodynia
Eponymous name for thalamic pain syndrome
Dejerine-Roussy syndrome
Parts of the brain involved in thirst perception
Subfornical organ (sits on the underside of the fornix near the foramina of Monro)
Vascular organ of lamina terminalis (sits near the subfornical organ and the median prominence)
Median preoptic nucleus of the hypothalamus
Neurotransmitter which propagates thirst signals
Angiotensin II
Location of baroreceptors which stimulates thirst when hypotension occurs
Aorta
Carotid
Organ which produces angiotensinogen
Liver
Enzyme which modifies angiotensinogen to angiotensin I
Renin
Organ which produces renin
Kidneys
Trigger for the kidneys to produce more renin
Decreased renal perfusion
Enzyme which modifies angiotensin I to angiotensin II
ACE
Organs which produce ACE
Lungs
Kidneys
Effects of angiotensin II
Propagates thirst signals
Increases sympathetic activity (to increase contractility of heart among other effects)
Increases tubular Na+ and Cl- reabsorption and K+ excretion in the kidneys to increase water retention
Increases aldosterone secretion in the adrenal gland (promotes Na+ and water retention)
Vasoconstricts to increase BP
Causes the pituitary to secrete ADH which leads to increased water reabsorption in the collecting duct
Two causes of increased thirst
Decreased circulating volume
Increased salt concentration of the interstitial fluid
Steps leading to increased thirst
Receptors in the subfornical organ and the organum vasculosum of lamina terminalis detect the concentration of blood plasma and the presence of angiotensin II
They activate the median preoptic nucleus
Water seeking and ingestion behaviour is initiated
Lesions seen in Kluver-Bucy syndrome
Bilateral lesions of the amygdala and hippocampus
Features of Kluver-Bucy syndrome
Docility and decreased aggression
Hypersexuality
Hyperphagia and hyperorality
Visual agnosia
Type of inheritance of Laurence-Moon-Biedl syndrome
Autosomal recessive
Features of Laurence-Moon-Biedl syndrome
Obesity Intellectual disability Polydactyly Diabetes insipidus Blindness due to retinitis pigmentosa Spastic paraplegia
Chromosome affected in Prader-Willi syndrome
15
Features of Prader-Willi syndrome
Obesity and hyperphagia Intellectual disability Hypotonia Short stature Diabetes mellitus
Usual trigger for Kleine-Levin syndrome
Viral infection
Feature of an episode of Kleine-Levin syndrome
Hypersomnia
Hyperphagia
Hypersexuality
Usual course of Kleine-Levin syndrome
Symptoms begin in adolescence
Repeated episodes each lasting weeks to months
Months of normal behaviour between episodes
Gradually increasing time between episodes and decrease in severity of episodes
Reduction or resolution in symptoms in 20s
Permeability of potassium ions across the cell membrane
Relatively permeable
Permeability of chloride ions across the cell membrane
Freely permeable
Permeability of sodium ions across the cell membrane
Relatively impermeable
Permeability of organic ions across the cell membrane
Relatively impermeable
Ion which causes presynaptic vesicles to release neurotransmitter into the synaptic cleft
Ca2+
Ion which sees an increased concentration in the axon terminal prior to depolarisation
K+
Ion which sees an increased concentration in the axon terminal prior to depolarisation
K+