autonomic nervous system (para, sympa, enteric) Flashcards
(29 cards)
What is the autonomic system?
Things which happen automatically whether you think about them or not.
What 3 systems is the autonomic system split into?
Parasympathetic
sympathetic
enteric
Parasympathetic and sympathetic are both outputs from where?
CNS with largely complementary effects on organs of the body.
Where is the enteric system mainly based and why is that key?
Gut, and able to function fairly independently to regulate GI activity.
What are voluntary (somatic) activities?
→ movement of skeletal muscles (e.g. limb movement),
→ sensory inputs (touch, temperature, pain)
What are automatic (autonomic) activities?
- regulation of activity of smooth muscles in blood vessels and viscera
- activity of many glands e.g. sweat or salivary
- regulation of heartbeat
- regulation of activity of the digestive tract
- inputs = feedback (e.g blood pressure) and some pain
What is the general organization of the autonomic nervous system?
- neuronal fibres leaving the CNS make a synapse in the small bundles of nerve cells (autonomic ganglia)
- postsynaptic/postganglionic neurons send fibres to target tissues
https://www.notion.so/autonomic-nervous-system-para-sympa-enteric-17d00bb3982d8047aafcd27a93acf567?pvs=4#17d00bb3982d800fa07fc65e3056cdff
What are the main types of transmitters?
Acetylcholine
Norepinephrine
Epinephrine
What are the similarities between sympathetic and parasympathetic systems?
Both receive ACh inputs from the CNS
Both have synapse in a ganglia (adrenal medulla is a slight exception) and then transmit to target tissue.
How are autonomic synapses different from voluntary synapses?
Autonomic synapses are less direct than voluntary synapses, and neurotransmitters have more diffuse impacts.
i.e. they regulate the overall ‘tone’ of the system, but don’t target specific muscle fibres
What is the ‘post ganglionic’ adrenal medulla an extreme example of?
Where secretion of adrenaline (epinephrine) into the bloodstream impacts tissues throughout the body.
Where are the ganglia in the parasympathetic system?
Very close to organs.
What transmitter remains in the post ganglionic neuron of the parasympathetic system?
ACh.
Where are the ganglia in the sympathetic system?
Ganglia (adrenal medulla slight exception): all along spinal cord.
Does the neurotransmitter change in the sympathetic system?
Neurotransmitter typically switches to NA but not always.
What is the autonomic efferent pathway?
Transmission of signals from the central nervous system (CNS) to target effectors.
- Where does the autonomic efferent pathway originate?
Origin in the spinal cord, where a central neuron (located in the CNS) generates a signal.
- Where does the signal travel after originating in the spinal cord?
Along a myelinated autonomic presynaptic axon to a ganglionic neuron in the autonomic ganglion.
The myelination enhances the speed of signal transmission.
- Where does the presynaptic neuron form a synapse?
With the ganglionic neuron within the autonomic ganglion.
- How is the signal carried away from the ganglion?
By the unmyelinated autonomic postsynaptic axon.
The lack of myelin means the signal transmission is slower than in the presynaptic axon.
- What does the postganglionic axon form instead of terminating at a single synapse?
Structures called varicosities, which release neurotransmitters over a wider area, allowing for diffuse signaling to the target tissue.
Where do neurotransmitters released at the varicosities bind?
On the target effector (e.g., smooth muscle cells).
This activates the effector to carry out its specific function, such as contracting the smooth muscle.
How do we know if your autonomic nervous system is working?
With no autonomic system, heart rate would be around 100+: for it to be under 100 bpm, set by parasympathetic tone.
How does standing trigger inputs to the spinal cord?
Blood flow will need to be changed to counter gravity pulling more to the feet, triggering the sympathetic nervous system to constrict muscles (mainly in the legs).
