Autonomic Nervous System Flashcards
What is the autonomic nervous system is involved with the involuntary control of?
Regulation of the functioning of internal organs
Maintenance of the internal environment
What does the autonomic nervous system directly innervate?
Cardiac muscle
Glands
Smooth muscle
What can the autonomic nervous system be divided into?
Sympathetic, parasympathetic and enteric nervous system
How do the sympathetic and parasympathetic nervous system vary in their interaction with metabolic resources?
Sympathetic maximises use of metabolic resources
Parasympathetic conserves metabolic resources
How do axons of the ANS reach effector organs, what kind of pathway is this called, and what organ is the only exception to this?
Via pre/postganglionic axons with a ganglion in the centre
Disynaptic pathway
Only exception is supply to the adrenal medulla
What is the myelin content of preganglionic and postganglionic?
Preganglionic = Myelinated
Postganglionic = Unmyelinated
What neurotransmitter do ganglion cells use, and what receptors do they bind to on postganglionic axons?
ACh
Bind to ionotropic nicotinic receptors
What neurotransmitter do postganglionic sympathetic axons use, what type of receptors do the bind to on effector organs, and what is the only exception?
Noradrenaline
Bind to metabotropic adrenergic receptors
Only exception is sweat glands, which use ACh
What are the different types of adrenergic receptors and where are they found?
alpha-1 (smooth muscle of blood vessels)
Beta-1 (heart)
Beta-2 (bronchial smooth muscle)
What neurotransmitter do postganglionic parasympathetic axons use, what type of receptors do the bind to on effector organs?
ACh
Bind to muscarinic metabotropic receptors
What is the sympathetic trunk
Interconnected paravertebral ganglia that extends from the cervical region down to the sacral region
Through what do preganglionic fibres enter the sympathetic trunk, and at what levels can this occur?
White rami communicans
T1-L2
Through what do postganglionic fibres exit the sympathetic trunk
Gray rami communicans
When preganglionic fibres enter the sympathetic trunk one of two things can happen, what are they?
1) Can synapse in the ganglion
2) Can pass through the ganglion and and into splanchnic nerves, where they can then synapse onto prevertebral ganglia
Are there more pre or postganglionic fibres, to what ratio is this, and what is the purpose of this?
More postganglionic fibres (1:10 ratio)
Allows for mass responses
How do postganglionic fibres from the prevertebral ganglia supply viscera?
They form a plexus around the visceral organ
What are the three ganglia in the cervical sympathetic trunk?
Superior, middle and inferior
What causes Horner’s syndrome, and what does it affect?
Disruption of sympathetic supply to the head between preganglionic fibres and the hypothalamus (e.g. due to a lesion)
Affects eyelids, pupils and skin of the face
What are the different thoracic splanchnic nerves that go to the prevertebral ganglia, and what do they innervate?
Greater, Lesser and Least splanchnic nerves
Innervate the abdomen
What are the preganglionic fibres of the parasympathetic NS within and what do they supply?
Brainstem (supply head, heart, lungs and abdomen)
Grey matter spinal cord that form S2-S4 spinal nerves (pelvic organs)
What type of nerves does the brainstem use in the parasympathetic nervous system?
Cranial nerves
What type of nerves does the spinal cord use in the parasympathetic NS?
Pelvic splanchnic nerves
What cranial nerves are involved in the parasympathetic NS, and what are their cranial nerve nuclei called?
Occulomotor nerve = Westphal-Edinger nucleus
Facial nerve = Superior salivatory nucleus
Glossopharyngeal nerve = Inferior salivatory nerve
Vagus nerve = Nucleus ambiguous
What do sacral parasympathetic fibres from the spinal cord form?
Sacral plexus
What are the functions of the sacral plexus?
Contraction of bladder wall and inhibition of sphincter
Inhibition of rectal sphincter
Vasodilation of erectile tissue
What are the 2 plexi of the enteric NS, where are they located and what is their function?
Auerbach’s plexus which regulates muscle contraction and is found in between the muscle layers
Meissner’s plexus regulates glandular secretions and is found on the inside wall
