PNS Flashcards
Peripheral nerves contain fibres that are axons of what neurones?
Afferent (sensory)
Efferent (motor)
Or both
What types of neurones do all spinal nerves contain?
Both efferent and afferent
What types of neurones do some cranial nerves contain and example for each?
Some cranial nerves contain only afferent fibres (optic nerve) or only have efferent fibres (hypoglossal nerve)
Afferent neurones
They convey info from ……. At their ……. To the……
Sensory receptors
Peripheral ending
CNS
Afferent neurones
Where do the longest part of their axon lie?
Outside the CNS and is part of the PNS
What are afferent neurones also referred to as and why?
First order neurones
They are the first cells entering the CNS
What do efferent neurones do?
They carry signals out from the CNS to muscles, glands and other tissues
What are efferent neurones subdivided into?
Somatic NS (voluntary) Autonomic NS (involuntary)
Somatic NS What does it innervate? How many axons/nurones does it have? Where do they go from & to? Neurotransmitters?
Innervates skeletal muscle
Single myelinated neurone/axon from CNS directly to skeletal muscle, without synapse
Only neurotransmitter-acetyl choline
Only excitatory
Autonomic NS What does it innervate? How many neurones involved? Where do they go from and to? Which neurotransmitters used? How do they function?
Innervate smooth & cardiac muscle, glands & neurones in the GI tract (enteric NS) & other tissues
2 neurone chain, connected by synapse
First neurone = cell body in CNS, pre ganglionic fibre, synapse outside CNS (autonomic ganglion), post ganglionic fibre, muscle/gland
Pre=always Ach
Post=Ach (excitatory) or NAd (inhibitory)
Function without conscious awareness (involuntary)
What can the autonomic NS be divided into?
Sympathetic and parasympathetic
Where does the sympathetic NS leave the CNS?
From the thoracic & lumbar regions (T1 - L2) of spinal cord
Where do most ganglia Iie in the sympathetic NS?
Most of the ganglia lie cloe to the spinal cord and form 2 chains of ganglia, one on each side of the cord, known as sympathetic trunks
Sympathetic
Are the preganglionic and postglionic axons short or long?
Pre = short Post = long
Sympathetic
Where do the preganglionic axons synapse?
At lateral horn T1 - L2
Sympathetic
What neurotransmitters and receprors are found at the pre and post ganglionic synapses?
Ach to nicotinergic
NAd to adrenergic
What does the efferent sympathetic NS supply?
Visceral organs and structures of superficial body regions
Does the sympathetic or parasympathetic division contain more ganglia?
Sympathetic contains more than parasympathetic
Sympathetic
The effects are ….. by the …….
Amplified
Adrenal glands
How do the adrenal glands amplify the effects of the sympathetic chain? What does this cause?
Release adrenaline directly into the blood
High blood pressure and Heart rate
What does the sympathetic NS cause to the body?
Increases heart rate Increases contractility Vasoconstriction Bronchodilation Reduces gastric motility Sphincter contraction Decreased gastric secretions Male ejaculation
Where does the parasympathetic axons leave the CNS?
From the brainstem and sacral portion of spinal cord
Where does cranial outflow come from?
Comes from brain
Which cranial nerves are parasympathetic?
What do the parasympathetic fibres do in these cranial nerves?
10, 9, 7, 3
CN3-occulomotor, pupil constriction
CN7-facial, to salivary glands
CN9- glossopharyngeal, for swallowing reflex
CN10-vagus, thorax and abdomen, (increased GI motility, decreased HR, vasodilation)
Where do cranial nerve cell bodies lie?
Cranial nerve nuclei in the brainstem
The parasympathetic fibres of the cranial nerves innervate organs of the …..
Head, neck, thorax and abdomen
What does the sacral outflow supply?
Supplies remaining abdominal and pelvic organs
Parasympathetic
Where do the ganglia lie relative to the organs that the post ganglionic neurones innervate?
Within/very close
Parasympathetic
Are the preganglionic and postglionic axons short or long?
Pre = long Post = short
Parasympathetic
What neurotransmitters and receprors are found at the pre and post ganglionic synapses?
Pre = Ach to nicotinergic Post = Ach to muscarinic
What does the parasympathetic NS cause to the body?
Decrease heart rate Decrease contractility Vasodilation Bronchoconstriction Increase gastric motility Sphincter relaxation Increased gastric secretions Male erection
What is the enteric NS?
Does it need to autonomic NS or can it operate independently?
NS of the GI tract
Can operate independently of the autonomic NS
