Neurology Flashcards
What are the two major types of synapse
Chemial: Main type with a neurotransmitter action
Electrical: direct connection between neurons via gap junctions, allows bi-directional flow
Which ion is responsible for mediation neurotransmitter release from vesicles at the synaptic cleft
Calcium
What are the two main categories of neurotransmitter
Small-molecule transmitters - Fast acting
class 1 (ACh), 2 (Amines - e.g. NE), 3 (Amino acids e.g. GABA), 4 - Nitric oxide
Neuropeptides - slow acting
What are the two types of postsynaptic potential
- Exictatiory postsynaptic potential (EPSP) - increases membrane permeability to Na+ and likelihood for AP
- Inhibitory postsynaptic potential (IPSP) - increased permeability to CL- in or K+ out - hyperpolarisation and reduced likelihood AP
What are the two types of signal summation
Spatial Summation: Addition of potentials from multiple synapses activated simultaneously across the neuron
Temporal Summation: Addition of potentials from repeated activation of the same synapse within a short time period
Describe the main anatomical features of the sympathetic nervous system
- spinal cord segments T1-L2,
- pass into sympathetic chain then to organs
- Preganglionic fibres can synapse in the sympathetic chain ganglia, peripheral vertebral ganglia or transmit up/down to other ganglia in SC
- Some preganglionic neurons pass straight to adrenal medulla
Describe the main anatomical features of the parasympathetic nervous system
- Leave CNS via CN 3,7,9,10
- Sacral spinal nerves S1-4
- Preganglionic fibres typically extend to the target organ
- Postganglionic fibres are short
Cholinergic fibres are present in which autonomic neurons, and secrete which substance
- All preganglionic neurons (sympathetic and parasympathetic)
- Almost all parasympathetic postganglionic neurons
- Some sympathetic postganglionic neurons (sweat glands, some blood vessels)
- Acetylcholine
Adrenergic fibres are present in which autonomic neurons, and secrete which substance
- Most sympathetic postganglionic neurons
- Norepinephrine
How is acetylcholine synthesised
- In terminal nerve endings
- Acetyl-CoA + choline –> choline acetyl transferase –> Acetylcholine
- Stored in vesicles ready for release
After acetylcholine has been secreted what happens to it
- split into acetate ion and choline
- by acetylcholinesterase
- choline transported back into nerve endings
How is norepinephrine synthesised
- In the axoplasm and completes in secretory vesicles
- Tyrosine –> Hydroxylation –> Dopa
- Dopa –> decarbylation –> Dopamine
- Dopamine transported to vesicles –> hydroxylation –> Norepinephrine
After norepinephrine has been secreted what happens to it
- 50-80% taken back up into nerve endings
- Some diffuses into blood
- Some destroyed by enzymens (monoamine oxidase)
Which receptors are cholinergic and list some of their features
Muscarinic receptors:
* Use G-proteins
* on effector cells stimulated by postganglionic cholinergic neurons
Nicotinic receptors:
* Use ligand-gated ion channels
* in autonomic ganglia at synapses between pre- and postganglionic neurons
* Also at many non-autonomic nerve endings e.g. skeletal muscle
Which receptors are adrenergic and list some of their features
Alpha receptors (α1, α2):
- G proteins
- vasoconstriction, iris dilation, intestinal relaxation, bladder sphincter contraction
Beta receptors (β1, β2, β3): G proteins - generally cause:
- (β1) - cardio acceleration, increased myocardial strength, lipolysis
- (β2) - Vasodilation, intestinal relaxation, bronchodilation, glycogenolysis, bladder wall relaxation
- (β3) - thermogenesis
- Norepinephrine excites mainly alpha receptors
- Epinephrine excites both alpha and beta equally
Give an examples of sympathomimetic drug
Norepinephrine, epinephrine, phenylephrine (α), isoproterenol (β), albuterol (β2)
Give an example of an alpha blocker
- General - phenoxybenzamine and phentolamine
- Selective alpha1 adrenergic blockers include prazosin and terazosin
- Selective alpha2 receptors yohimbine
Give and examples of beta blockers
- Both beta1 and beta2 receptors - propranolol
- Beta1 receptors are atenolol
Give and exampel of a parasympathomimetic drug
Pilocarpine
Give an example of a drug which has parasympathetic potentiation effect
Anticholinesterases: Neostigmine, pyridostigmine
What is the blood brain barrier and blood CSF barrier permeable/impermeable to
- highly permeable to water, O2, CO2, and lipid-soluble substance
- slightly permeable to electrolytes (Na, Cl, K)
- Almost impermeable to proteins and large non-lipid-soluble molecules
What are the main areas of the cerebrum
- Olfactory bulb (sensory)
- Frontal lobe (motor/sensory)
- Parietal lobe (motor/sensory)
- Temporal lobe (motor/sensory)
- Occipital lobe (sensory)
What are the main areas for neurolocalisation?
Forebrain - Cerebrum and thalamic area
Cerebellum
Brainstem (medulla, pons, midbrain)
Spinal cord
○ C1-C5 spinal cord segments
○ C6-T2
○ T3-L3
○ L4-S3
Peripheral nerves
Lumbosacral and brachial plexus
Describe the localisation and features of a decerebrate rigidity
- Lesion in brainstem
- Comatose, opisthotonus, extension and increased tone in all limbs
- Poor prognosis
