autonomic nervous System Flashcards
What are the two distinct divisions of the peripheral nervous system:
- autonomic nervous system
- somatic nervous system
what does the “efferent” part of a nervous system mean?
- from spinal cord/ NS centre to tissue
what is the ventral horn of the spinal cord?
- a specific region in the spinal cord
- contains cell bodies of motor neurons
what is the primary function of the autonomic nervous system?
homeostasis
* maintaining dynamic balance of physiological conditions within the body
what are the two types of ANS
- parasympathetic nervous system (PNS) - rest & digest
- sympathetic nervous system (SNS) - fight or flight
where are sympathetic pre-ganglionic neurons located on the spinal cord? (2)
- thoracic and lumbar spinal
where are the parasympathetic pre-ganglionic neurons located on the spinal cord (2)
- brain stem (c-region)
- sacral spinal cord
upon activation of the adrenal medulla by the SNS, what does it do?
release of catecholamines:
* epinephrine & norepinephrine
when is the adrenal medulla typically stimulate by the SNS?
- in response to very strong stress
how long does it take to clear catecholamines from the blood after stimulation of adrenal medullae?
- 3-4 minutes
what are catecholamines?
- a class of neurotransmitters that play crucial roles in the nervous system and the body’s stress response
3 main catecholamines
- dopamine
- norepinephrine
- epinephrine
pathway of sympathetic neuron flow: (4)
- pre-ganglionic neurons
- para-vertebral ganglia
- pre-vertebral ganglia - only some pathways
- post ganglionic neurons
post-ganglionic neuron features:
- unmyelinated
- exits para-vertebral ganglia via gray communicating rami
afferent vs efferent neurons:
afferent - sensory neurons
efferent - motor neurons
afferent neuron root in SNS: (3)
- paravertebral ganglia
- white rami
- dorsal root
what is the most robust nerve of the CNS, and what number nerve is it
- the Vagus nerve - 10th cranial nerve
why does the Vagus nerve need to be so robust?
- it innervates heart, and abdomen organs
the three components of the brain stem:
- medulla
- pons
- mid-brain
when would one cranial nerve have more than one cranial ganglia?
- when it is innervating different things
- e.g., nasal glands & salivary glands have different ganglia from C6
what modulates the ANS?
the hypothalamus
how is the enteric nervous system related to the ANS?
- it is autonomous - not dependant on control from central or peripheral nervous system
where is the enteric nervous system found?
- in the gastrointestinal tract
what stimulates the enteric nervous system?
- the PNS - increases motility and secretion
what type of receptors are nicotinic acetylcholine receptors, and muscarinic acetylcholine receptors?
nicotinic acetylcholine receptors - ionotropic receptors
muscarinic acetylcholine receptors -** m**etabotropic receptors
what are G-protein coupled receptors? (2)
- cell-surface receptors
- transmit signals from extracellular environment to intracellular environment
what is the substance that can only activate muscarinic acetylcholine receptors?
muscarine
what is the substance that can only activate nicotinic acetylcholine receptors?
nicotine
what substance activates both mAChRs and nAChRs?
acetylcholine
upon long abuse of nicotine, what system of the ANS is primarily effected, and how (2)?
SNS
* causes arrhythmia
* cause hypertension
what is the use of acetylcholine esterase inhibitors?
- medicines
- chemical weapons
what is the principle subunit that forms the ion channel of AChRs?
alpha subunits
how to record individual molecules current capacity? (2)
- using path clamp electrophysiology technique
- applying acetylcholine to polarise or hyperpolarise it
what is Curare? (4)
- a plant derived compound
- acts as a neurotoxin
- as a competitive antagonist at nAChRs
- blocks nAChRs on skeletal muscle
how does Curare kill animals? (4)
- acts on both ANS and SNS
- blocks somatic synapses in skeletal muscle
- diaphragm cannot contract
- respiration cannot occur
what are the receptors of the SNS?
adrenergic receptors
what are the receptors of the PNS?
muscarinic receptors
how are different sympathetic responses carried out?
- via different types of adrenergic receptors
what are vasomotor tone effects?
- effects of blood perfusion to skeletal muscle and visceral organs
what are chronotropic and inotropic effects
chronotropic - changes of HR
inotropic - how strong the heart contracts
what are the main 4 effects of the ANs on the CVS?
- heart rate
- heart contraction force
- constriction/dilation of blood vessels
- contraction/relaxation of smooth muscle in organs and glandular secretion
what are the main nerves involvedin the PNS control of the CVS, and where they originate from:
- Vagus nerve - 10th cranial nerve
- Glossopharyngal nerve - 9th cranial nerve
what send the afferent signals to the PNS in regulation of the heart
baroreceptors
what are the preganglionic nerves involved in parasympathetic regulation of the heart? (2)
- Dorso motor nucleus (vagus nerve)
- Nucleus ambiguous (glossopharyngeal nerve)
how the SNS effects systole and diastole during exercise:
- reduces systole duration
- increases diastole duration
what occurs in absence of the Vagal tone?
- high resting heart rate
what does frequent aerobic exercise do to the vagal tone?
- enhances the vagal tone, increasing parasympathetic system so HR lowers
how can the vagal tone be impaired? (4)
- aging
- altitude
- deconditioning
- bed rest (inactivity)
when you have not ran for a while, why may you feel a sense of ‘uneasiness’ during the first 2 minutes?
- body is un-adapted to the changes so parasympathetic system is trying to dampen the cardiac and pulmonary output
what does sympatholytic mean?
- something that decreases the sympathetic tone during rest
what is the initial consequence of spinal cord injury?
- spinal cord shock
what occurs in SCI after spinal cord shock?
- neurogenic shock
what condition can downregulation of the SNS in SCI lead to?
- autonomic dysreflexia
what is autonomic dysreflexia?
- a life-threatening emergency that can occur in individuals with spinal cord injuries at or above the level of T6
what is autonomic dysreflexia characterised by? (5)
- increased BP
- bradycardia
- sweating above level of injury
- nasal congestion
- headaches
how is autonomic dysreflexia caused? (3)
- painful stimuli,
- that is not percieved consciously by the patient
- that results in an increase in BP
how does the SCI effect thermoregulation? (2)
- lower temperature of body below level inury
- due to no SNS innervation of legs which normally constricts blood vessels and restricts head loss
what section of the PNS regulates bladder contractility:
- S2-4
what section of the SNS regulated the internal urethral sphrincter?
T11-L2
what is complex regional pain syndrome (CRPS)
- neuropathic pain and hyperalgesia
- which is provoked by mild, non-painful stimuli
