functional neuroanatomy of the peripheral nervous system Flashcards
what are the three major divisions of the nervous system?
-the Somatic NS
-the Autonomic NS
-the Enteric NS
what two classes of neurons does the somatic NS consist of?
-sensory neurons
-motor neurons
what do sensory neurons do?
-monitor the external environment and send signals to the CNS arising from a range of sensory receptors
state the different sensory receptors…
-mechanoreceptors-touch
-thermoreceptors-temp
-nocireceptors-pain
-proprioceptors-proprioception
what do sensory neurons use as neurotransmitters?
-glutamate
where do sensory neurons help to process info?
-spinal cord
-medulla
-thalamus
-somatosensory cortex
-this allows for the conscious perception of this info
where are motor neurons located?
within the spinal cord
what do motor neurons do?
-send signals to the skeletal muscles
-regulate voluntary motor control
-utilise Act as the neurotransmitter
-activate nicotinic cholinergic receptors located on muscle cells and this results in rapid muscle contraction
what is the differences between the ANS and the SNS?
-the involvement of conscious control
-in the SNS feedback via tactical, thermal,pain and proprioreceptive (position) sensations are consciously perceived and skeletal muscles is the main tool used to provide reflexive and voluntary movements
-the ANS usually operates without conscious control,although centres in the hypothalamus and brainstem provide regulation for ANS reflexes
what are interoceptors and where are they located?
-interoceptors are sensory receptors that monitor conditions in the internal environment and they are located in the blood vessels, visceral organs,muscles and nervous system
give examples of interoceptors…
-chemoreceptors that monitor blood CO2 levels
-mechanoreceptors that detect the degree of stretch in the walls of organs or blood vessels
what does the ANS do?
monitors the internal environment
how does the ANS carry out its function?
-there is sensory input-by autonomic sensory neurons associated with interoceptors in blood vessels, visceral organs, muscles
-there is motor output to cardiac and smooth muscles and glands, the response is involuntary and either increases (excites) or decreases (inhibits) activity
-it uses two motor neurons in series which release ACh or NE (norepinephrine0
describe the anatomy of the autonomic motor pathways…
-there is the preganglionic neuron (myelinated)-this is a cell body in the brain or spinal cord
-there is the postganglionic neuron (unmyelinated) which is a cell body in the autonomic ganglion
what is the ganglion?
a collection of neuronal cell bodies in the PNS
describe the ANS connections…
-Neurons in the CNS send their axons to synapse onto (these axons are called preganglionic fibres)
-Group of neurons are located outside the CNS (called ganglia)
-Neurons in these ganglia send their axons to release their neurotransmitters on target organs(these axons are called post-ganglionic fibres)
-Target organs express receptors for the neurotransmitters (NA & Ach) which are released from post-ganglionic fibres
-Released neurotransmitters bind to receptors on target organs and this results in the effect on that organ e.g an increase in hear rate,increased glandular secretion etc
what are the two divisions of the ANS?
-sympathetic division (SNS)
-parasympathetic division (PNS)
what does the sympathetic division cause?
-generally causes excitation
-flight or fight response
-increases heart rate and blood pressure
-pupil dilation
-release of glucose from the liver
what does the parasympathetic division cause?
-generally causes inhibition
-rest and digest
-conserves energy and replenishes nutrient stores
what do postganglionic neurotransmitters do?
-in the parasympathetic system they release Ach and there is a local effect
-in the sympathetic system they release Noradrenaline and there is a far reaching effect
define parasympathomimetic
mimimicing on promoting muscarinic actions of Ach or inhibiting actions of NA
define parasympathomimetic
mimicking or promoting NA actions or inhibiting muscarinic actions of Ach
describe nicotinic receptors…
-they are pentameric (have 5 protein subunits)
-they are inotropic
-they have ligand-gated ion channels
-2 molecules of Ach are needed to activate receptors
what are three main classes of nicotinic receptors?
-muscle type
-ganglion type
-CNS type
what is the location of each class of nicotinic receptors?
muscle type-neuromuscular junction
ganglion type-autonomic ganglia
CNS-brain
what is the membrane response for each class of nicotinic receptors?
-all excitatory membrane responses
what are the agonists for the muscle type of nicotinic receptor?
-Ach
-Carbachol
-succinylcholine
what are the agonists for the ganglion type of nicotinic receptors?
-Ach
-Carbachol
-Nicotine
what are the agonists for the CNS type of nicotinic receptor?
-Ach
-nicotine
what are the antagonists for the muscle type of nicotinic receptor?
-tubocurarine
-a-bungarotoxin
-pancuronium
what are the antagonists for the ganglion type of nicotinic receptor?
-hexamethonium
-trimetaphan
what are the antagonists for the CNS type of nicotinic receptors
a-bungarotoxin
