Basic neurophysiology Flashcards by Bethan Williams

Intracellular resting membrane potential

-70mV

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Intracellular threshold potential

-55mV

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Channels that open at the intracellular threshold potential of -55mV

Na+ channels

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Result of the Na+ influx caused by Na+ channels opening

Reversal of the membrane potential to +40mV

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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

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Term for a junction between two nerve cells

Synapse

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Three types of synapses in the nervous system

Chemical synapse
Electrical synapse
Conjoint synapse

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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

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Types of chemical synapse depending on their effect on the postsynaptic neuron

Excitatory

Inhibitory

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Effect of excitatory chemical synapses on postsynaptic neurons

Depolarises

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Effect of inhibitory chemical synapses on postsynaptic neurons

Hyperpolarises

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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

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Type of facilitation where input from several different presynaptic cells leads to an action potential

Spatial summation

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Type of facilitation where recurrent stimulation from the same presynaptic neuron results in an action potential

Temporal summation

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Features of an electrical synapse

Response is generated by electrical communication without the need for chemical molecules to be exchanged

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Features of a conjoint synapse

Both electrical and chemical properties

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Part of the body which acts as the satiety centre

Ventromedial hypothalamus

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Part of the body which acts as the feeding centre

Lateral hypothalamus

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Neurochemicals which cause increased appetite

Ghrelin

Neuropeptide Y

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Neurochemicals which decrease appetite

Leptin
Cholecystokinin
Serotonin

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Part of the body where ghrelin is synthesised

Gastric mucosa

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Cells which synthesise ghrelin

Adipose cells

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Part of the body where activity is increased by food and food cues

Nucleus accumbens

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Type of activity produced in the nucleus accumbens by food and food cues

Dopaminergic activity

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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

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+