The Autonomic Nervous System Flashcards
What is the majour function of autonomic sensory receptors?
Detecting the internal environmental conditions in the body
What is the function of chemoreceptors?
assessing blood (CO2), blood pH & blood glucose
What is the function of mechanoreceptors?
detecting the degree of stretch in the walls of BV’s and organs
what is the function of nociceptors?
detecting visceral pain
Where are the motor effectors in the ANS found? (3)
- Smooth muscle
- Cardiac muscle
- Glands
Can tissue function continue if there is nerve damage to an ANS-controlled tissue?
yes.
The beart beats on its own even if nerves to it are severed or damaged.
Some glands secrete even without ANS control
Describe an ANS motor unit
2 - neuron chain
- preganglic neuron
- postganglionic neuron
Describe the functions of the preganglionic & postganglionic neurons
Impluses leave the CNS via a prehanglionic neuron, which then synapses with the postganglionic neuron which then synapses with the effector
Where are the cell bodies of postganglionic neurons found?
Outside the CNS
What is another name for cell-bodies of postganglionic neurons?
autpnomic ganglia or motor ganglia
Describe the preganglionic neuron
extends from the CNS to the autonimic ganglion.
thin & lightly myelinated
CCell body is in the CNS
Describe the axon of the prehanglionic neuron
it forms part of the spinal or cranial nerve as it lewaves the CNS
what is the neurotransmitter thats preganglionic neurons produce?
acetylcholine (Ach)
Describe the postganglionic neuron
Extends from the preganglionic neuron to the effector.
Thinner & unmyelinated.
Entirely outside the CNS
What are the 2 branches of the ANS and motor division?
- Sympathetic (thoracolumbar)
2. parasympathetic (craniosacral)
What is the majour function of the sympathetic NS?
Emergency response
When there is a real or percieved threat on homeostasis
What is the fight or flight response?
when the body is under stress it either fights or flees from this stress.
Occus because of the sympathetic NS
What are the sympathetic responses?
Higher/increased: heart rate, BP, blood sugar, BPM, sweat
Dialated pupils & bronchi
Constriction of BV’s
Slowed digestion & urine production
Stimulation of adrenal gland (release of epinephren)
Where are the preganglionic neaurons foudn in the sympathetic NS?
The dendrites & ceoll bodies are found within the lateral grey horns in the thoracis & lumbar segments of the spinaal cord
How many postganglionic neurons does one preganglionic neuron synapse to?
multiple
What does cholinergic mean?
the type of neurons found in the sympathetic NS because acetylcholine is used.
Where is the sympathetic chain ganglia found?
extend from the C2 to the coccyx
Are presympathetic neurons long or short?
short
Are the preganglionic neurons myelinated?
yes
Are the postganglion neurons myelinated?
no
Where are the cell bodies & dendrites of postganglionic neurons found?
in the sympathetic chain ganglia
Where are the axons of the postganglionic neurons foud?
Very long.
Extend from the sympathetic chain ganglia to the effector cells
What are the 3 ways in which preganglionic & postganglionic neurons synapse?
- Preganglionic axon with poostganglionic neuron at the first gonglion entered
- Preganflionic axon may go up or down the chain of sympathetic chain ganglia to arrive at ganglia above/below its original exit point from the cord & synapse with postganglionic neurons at the new location
- The preganglionic neuron will continue & synapse at a secondary ganglia with multiple post-ganglionic neurons (this makes it wide spread & invlove many organs.
What are the types of postganglionic neurons?
- Adrenergic
2. Cholinergic
What is the most common type of postganglionic neuron?
Adrenergic
What do adrenergic neurons release?
norepinephrine (Nepi)
How is the adrenal gland stimulated?
When there is prolonged sympathetic activity
What does the adrenal gland produce?
norepinephrine & epinephrine
What are the types of adrenergic receptors? (2)
- Alpha
2. Beta
What are alpha receptors stimulated by?
Norepinephrine (Nepi)
What are the 2 subtypes of alpha receptors?
- ⌥1
2. ⌥2
What are the subtypes based upon?
their precise response to NT (nervous tissue) and various drugs that can inhibit or activate them.
What does ⌥1 receptors produce?
The stimulation/excitation of the effector
Where are ⌥1 receptors found?
on the plasma membranes of smooth muscle cells in the BV walls
What do ⌥1 receptors cause?
constriction of smooth muscle & constriction of blood vessels
what is the function of ⌥2 receptors?
they bind with Nepi/epi & cause the inhibition of the effector
What are BETA receptors stimulated by?
epi/nepi
What are the subtypes of BETA receptors? (3)
- ⌥1
- ⌥2
- ⌥3
What is the ultimate influence of epi/nepi?
depends on which receptors are present on the effectors cells
Describe ⌥2 BETA receptors
INHIBITED by epi, nepi
Found in plasma membranes in smooth muscle cells & in BV walls.
Therefore epi/nepi causes these cells to relax
Describe ⌥1 BETA receptors
STIMULATED by epi/nepi
Found in cardiac muscle cells
When epi binds to these receptors the cardiac muscle is stiumlated/excited producing an increased heart rate.
What is the function of drugs called “beta-blockers”
They block the beta receptors
Therefore lower HR & BP
What is the parasympathetic NS also known as?
“rest & repair” or “rest & digest”
What are some parasympathetic responses?
lower HE & BP Increased digestion & urine production/elimination Dialation of cornary BV's Constriction of pupils & bronchioles Increased secretion of tears & saliva
Where are preganglionic neurons found in the parasympathetic NS?
the dendrites & cell bodies are found in brain stem nuclei & in the lateral grey horns of the 2nd - 4th sacral segments of the spinal cord
“craniosacral division”
Where do the preganglionic & postganglionic neurons synapse in the parasympathetic NS?
At the terminal ganglia
Close to effectors far from CNS
Describe preganglionic neurons in the parasympathetic division
Long axons
Synapse to a single postganglionic neuron = single effector
Therefore localized
Describe the postganglionic neurons in the parasympathetic NS
Tend to be short
Cell bodies & dendrites are found in the ganglia/terminal ganglia which are embedded effector
What is the ONLY neurotransmitter used in the parasympathetic NS?
Acetylcholine (Ach)
What are the types of cholinergic receptors?
- Nicotine
2. Muscarine
What is the function of cholinergic neurons?
release Ach at their synapse with sweat glands
Therfore it stimulates the production & secretion of sweat glands
where are cholinergic receptors found?
In plasma membranes of cells making up the sweat glands
Where are nicotine receptors foud?
on the postganglionic neurons is both the sympathetic & parasympathetic nervous systems
ALSO found in the skeletal muscle cells at the neuromuscular junctions
What effect doers Ach have on nicotinic and muscarine receptors?
nicotine –> stimulte/excite the cell containing the receptors
Muscarinic –> stimulation/excitement or INHIBITION
How can the action of the neurotransmitter be determined?
- Reuptake of the neurotransmitter
2. Enzyme breakdown
How can enzymes be broken down?
ACETYLCHOLINE (Ach) –> ACETYLCHOLINESTERASE
NEPI –> Catechol - 0 - methyltranferase (COMT) or (MAO)
What is the function of the hypothalamus with the ANS?
Somatic senses, visceral autonomic sensary imput plus smell/taste
What is the function of the limbic system?
Sends emotional imput to the hypothalamus
Where does the hypothalamus send motor signals?
1> autonomic control centers in the brainstem (cardiac & respitory control centers)
2. Spinal cord (defication turination reflex centers)
Describe what parts of the hypothalamus parts of the hypothalamus control the sympathetic & parasympathetic divisions?
Sympathetic = posterior & lateral parasympathetic = Anterior & medial
