The Autonomic Nervous System Flashcards
What does the autonomic nervous system control?
Involuntary movements
How may the autonomic nervous system be divided?
The sympathetic and parasympathetic nervous system
Which regions of the spinal column are associated with the sympathetic nervous system?
The thoracic and lumbar regions
Which branch of the autonomic nervous system is the vagus nerve generally associated with? Which organs does this influence?
The vagus nerve is generally associated with the parasympathetic branch of the autonomic nervous system - it deals with parasympathetic control of the heart, lungs, and digestive tract
From which specific part of the spinal cord does the vagus nerve stem?
The 10th cranial nerve
What specific region of the spinal cord is associated with the parasympathetic nervous system?
The medullary portion
How do the pre-ganglionic and post-ganglionic structures differ in the sympathetic and parasympathetic branches of the autonomic nervous system?
In the parasympathetic branch the pre-ganglionic nerve is fairly long and stems deep into the peripheral nervous system, while its post-ganglionic nerve is far shorter - conversely, in the sympathetic branch the pre-ganglionic nerve is short and stems only slightly into the peripheral nervous system, while its post-ganglionic nerve stems the majority of the peripheral nervous system
Where specifically are the ganglia of sympathetic and parasympathetic nerves located?
Parasympathetic ganglia are located in innervated tissues, while sympathetic ganglia are located in the paravertebral chain close to the spinal chord
Describe the myelination of pre- and post-ganglionic nerves in sympathetic and parasympathetic systems.
Both sympathetic and parasympathetic pre-ganglionic nerves are myelinated, while both sympathies and parasympathetic post-ganglionic nerves are unmyelinated
What neurotransmitter do pre-ganglionic nerves use? Is this the same in sympathetic and parasympathetic nerves?
Acetylcholine is the neurotransmitter used in pre-ganglionic nerves of both sympathetic and parasympathetic nervous systems
What receptors are situated on the post-ganglionic nerves?
Nicotinic acetylcholine receptors
What type of receptor are nicotinic acetylcholine receptors?
Ligand-gated ion channels
What type of receptor are adreno-receptors and muscarininc acetylcholine receptors?
They are all G protein-coupled receptors
What neurotransmitter do post-ganglionic nerves of parasympathetic and sympathetic nerve branches release?
Post-ganglionic nerves release acetylcholine in the parasympathetic branch, while they release noradrenaline in the sympathetic branch
What receptors are found on target tissues of sympathetic and parasympathetic nerves?
Muscarininc acetylcholine receptors are found on target tissues of parasympathetic nerves (as their post-ganglionic nerves are cholinergic) and adrenoreceptors are found on target tissues of sympathetic nerves (as their post-ganglionic nerves are noradrenergic)
How does a ligand activate a G protein-coupled receptor?
It binds and causes an allosteric change, causing the G protein to release GDP and bind GTP, activating it
In which cases do sympathetic nerve fibres release acetylcholine onto their target tissue as opposed to noradrenalin?
Those innervation sweat glands and hair follicles
Where in the body do chromaffin cells reside?
In the adrenal medulla
What branch of the nervous system controls voluntary movement (opposite to the autonomic nervous system)?
The somatic nervous system
How does the sympathetic nervous system act differently at the adrenal medulla?
The post-ganglionic fibres differentiate of form chromaffin cells - instead of secreting neurotransmitter onto a target tissue, they secrete adrenalin into the bloodstream to act on a wide variety of target organs
Does the somatic branch of the nervous us have pre- and post-ganglionic nerve fibres?
No
In the somatic nervous system, list the neurotransmitter used, the type of receptor it acts on, and on which tissue these receptors are located.
In the somatic nervous system acetylcholine is used, which binds nicotinic acetylcholine receptors on the surface of skeletal muscle
Which muscarininc receptor is located at the heart? Which muscarininc receptor is located at the lungs?
M2 muscarininc acetylcholine receptors are located at the heart, while M3 muscarininc acetlycholine receptors are located at the lungs
Which gas is involved with penile erection?
Nitric oxide
What is the collective term used to describe disorders of the autonomic nervous system?
Dysautonomia
Which G protein-coupled receptors are associated with noradrenergic release at the heart and the lungs?
B1 adrenoreceptors at the heart and B2 adrenoreceptors at the lungs
What body specifically monitors the components of blood? How is this relayed to the CNS?
The carotid body can monitor the blood for O2, CO2, and pH, which it relays information on back to the CNS via the glossopharyngeal nerve
Where is all sensory information eventually localised?
The nucleus tractus solitarius
Which area can detect toxins and relays this information back to the nucleus tractus solitarius to induce chemically-induced vomiting?
The area postrema
State 4 distinct part of neurotransmission that are targeted by drugs.
- degradation of neurotransmitter
- interaction with the post-synaptic receptor
- re-uptake of neurotransmitter
- inactivation of the neurotransmitter
What equation describes acetylcholine synthesis?
Acetyl CoA + choline —> acetylcholine + CoA
What enzyme is involved in acetylcholine synthesis? What enzyme is involved in its degradation?
Choline acetyltransferase is involved in acetylcholine synthesis - acetylcholinesterase is involved in its degradation
What products are produced from the breakdown of acetylcholine?
Acetate & choline
Give an example of an acetylcholinesterase.
Neostigmine
How many different types of muscarininc acetylcholine receptors are there?
5
Why do some drug interventions act differently at autonomic nervous system ganglia and at skeletal muscle neuromuscular junctions?
The nicotinic acetylcholine receptors at the 2 different regions differ in structure
What can be used to enhance the action of endogenous acetylcholine? List 2 examples.
Acetylcholinesterase inhibitors, such as pyridostigmine & donepezil
What is a consequence of the relative lack of specificity of drugs affecting the muscarininc cholinergic system?
Various side effects
What are some of the pathological effects indicative of a massive parasympathetic discharge. What mnemonic does this spell?
- Secretion - increased salivary gland secretion
- Lacrimation - stimulation of the lacrimal glands
- Urination - relaxation of the urethral interior sphincter muscle
- Defecation
- Gasrtointestinal - smooth muscle tone changes leading to problems
- Emesis - vomiting
How do nerve gases (eg sarin) and some insecticides (e.g. parathion) lead to the ‘SLUDGE’ symptoms?
The covalently modify acetylcholinesterases to prevent their activity, greatly increasing levels of acetylcholine
What is the pathology behind the ‘SLUDGE’ symptoms? What specific drugs may be used to treat these symptoms?
Chronic stimulation of muscarininc acetylcholine receptors may lead to the ‘SLUDGE’ symptoms - they may be treated by atropine & pralidoxime
describe the synthesis of adrenaline from tyrosine, stating all enzymes and intermediates.
Tyrosine -> tyrosine hydroxylase -> DOPA -> DOPA decarboxylase -> dopamine -> dopamine B-hydroxylase -> noradrenaline -> phenylethanolamine N-methyltransferase - > adrenaline
Where in the body is noradrenaline converted into adrenaline? What enzyme facilitates this conversion?
In the adrenal medulla, by phenylethanolamine N-methyltransferase
What receptors does noradrenaline interact with?
Adrenoreceptors
How is adrenergic transmission terminated?
It is terminated via reupatake into the pre-synaptic vehicle via a Na-dependent, high affinity transporter - a lower affinity mechanism also exists for any that are missed
List 2 enzymes involved in the metabolism of noradrenaline that can be targeted by drug therapy.
Monoamine oxidase
Catechol-O-methyl transferase
What type of molecules are used to combat asthma?
B2-adrenoreceptor-selective agonists are used in asthma to oppose bronchoconstriction (e.g. salbutamol)
What molecules are used to treat cardiovascular disorders such as hypertension?
A1-adrenoreceptor-selective antagonists (e.g. doxasosin)and B1-adrenoreceptor-selective antagonists (e.g. atenolol)
Describe the pathology of asthma.
Asthma is a chronic condition that stems from airway hyper-responsiveness to allergens such as cigarette smoke and pollen - these trigger eosinophils to release cytokines and other mediators which cause inflammation of the conducting part of the airway (bronchi and bronchioles) - there is also increased mucus secretion, making it harder to breath -
What adrenoreceptors are found in the conducting portion of the airways?
Beta-2 adrenoreceptors
What is the consequence of stimulating adrenoreceptors in the airways?
Stimulation of B2 adrenoreceptors in the airways by adrenaline/noradrenaline will lead to a Gs G protein activating adenyl cyclase, cAMP, and finally protein kinase A - this will act overall to cause smooth muscle in the airways to relax (bronchodilation)
What are the 2 main categories used to treat asthma? Give 2 examples of each.
- relievers, such as beta agonists and antocholinergics
- preventers, such as glucocorticosteroids and leukotrine receptor antagonists
Put simply, how to preventers aim to prevent asthma?
They are anti-inflammatory drugs
Describe when short-acting and long-acting bronchodilators would be used in asthma.
- short-acting bronchodilators are used immediately in an asthma attack in order to open the airways of an individual
- long-acting bronchodilators are often used at night, to give a steady and consistent peak flow during the night and the following morning
What is hypertension?
Abnormally high blood pressure
Describe in detail the physiological reflexes involved in controlling normal blood pressure.
Renin is produced by the kidneys in response to a decrease in blood pressure - this cleaves angiotensin produced by the liver to angiotensin 1, which is cleaved by ACE to form angiotensin 2 - this acts on the adrenal glands and blood vessels, stimulating vasoconstriction (in order to increase blood pressure)
What is normal blood pressure? What is the clinical criteria for diagnosis of hypertension?
Normal blood pressure is 120/80mmHg - the clinical criteria for hypertension is 140/90mmHg
Suggest 4 drug types that may be used to reduce hypertension, stating how they act.
- ACE inhibitors - inhibit ACE, meaning no angiotensin 2 is formed, and the cascade leading to vasoconstriction is blocked
- diuretics - increase Na+ and water loss, decreasing water volume in the blood and hence decreasing blood pressure
- Ca2+ channel blockers - prevent Ca2+ entry into cells, preventing contraction of skeletal and smooth muscle, and slowing the contraction of the heart
- beta-2 adrenoreceptor antagonist - slows heart rate
What are the major population of adrenoreceptors that mediate vasoconstriction of the vasculature?
Alpha-1 adrenoreceptors
State 3 ways in which beta-2 antagonists exert their anti-hypertensive action.
- reduced ionotropy (force of contraction of muscle)
- reduced chronotropy (reduced heartbeat)
- reduced renin release from the kidneys (preventing the cascade leading to vasoconstriction)
Why should consideration be given to the potential side effects when administering a drug?
Side effects are not normally well-received, and lead to poor compliance
What is thyrotoxicosis?
Thyrotoxicosis relates to an overactive thyroid
What class of drug are normally given to an individual who presents with thyrotoxicosis? Why?
Usually non-selective beta-adrenoreceptor antagonists are used - these can be administered intravenously in patients presenting acutely with thyrotoxicosis crisis
Describe the main steps when circulating adrenaline binds it’s appropriate receptors on cardia tissue.
- adrenaline binds beta-1 adrenoreceptors at the heart
- this stimulates a Gs protein to adopt GTP, which gives it the energy to activate adenyl cyclase
- adenyl cyclase converts ATP to cAMP, which binds and activates protein kinase A
- protein kinase opens T-type Ca2+ channels, releases stored Ca2+ from the sarcoplasmic reticulum, and phosphorylates myosin heads to increase their activity
- overall, this all leads to an increased heartbeat
