Autonomic Nervous System Flashcards
What 4 things does the autonomic nervous system innervate?
Visceral structures
Glandular myoepithelium
Adipose tissue
Vasculature and cardiac tissue
What is the autonomic nervous system and what is its function?
It is an involuntary system that aims to preserve a constant internal environment (homeostasis)
What are the 2 subdivisions of the ANS?
- Parasympathetic (rest and digest)
- Sympathetic (fight or flight)
Where does the parasympathetic NS arise from?
Parasympathetic arises from brain and sacral spinal cord
Where does the sympathetic NS arise from?
Sympathetic arises from the thoraco-lumbar spinal cord.
What does it mean to have dual innervation?
Each organ receives innervation from both sympathetic and parasympathetic nerve axons.
What happens when there is sympathetic dominance?
- Increased heart rate
- Decreased digestion
- Pupils dilate
What happens when there is parasympathetic dominance?
- Decreased heart rate
- Increased digestion
- Pupils constrict
An autonomic pathway consists of a 2-neurone chain, where do these two neurones synapse?
In a ganglion
What is different about the post-ganglionic neurone?
It is normally unmyelinated.
What neurotransmitter is released with the sympathetic nervous system?
Norepinephrine
What neurotransmitter is released with the parasympathetic nervous system?
Acetylcholine
Are the pre- and post-ganglionic neurones of the autonomic NS afferent or efferent?
They are efferent neurones
What neurotransmitter do pre-ganglionic neurones always release?
Pre-ganglionic neurones release ACh
What are the advantages and disadvantages of using two different neurones in the autonomic system?
- Moving neurones into the PNS helps to save space in the CNS
- It can take longer for information to reach the brain (not too much of a concern as visceral organs have a very limited range of possible actions)
What type of ganglia do you find coming out on either side of the spinal cord?
Paravertebral ganglia
Which parts of the brain control the sympathetic and parasympathetic nervous systems?
- Rostral hypothalamus influences the parasympathetic system
- Caudal hypothalamus influences the sympathetic system
What are the 5 different components to a reflex arc in the autonomic nervous system?
- Sensory receptor
- Sensory neurone (afferent)
- Integrating centre
- Pre- and post-ganglionic motor neurones
- Visceral effectors
Where does the sympathetic nervous system originate and leave from?
- The lateral/ intermediate horn of the thoracolumbar spinal cord.
- It leaves via ventral roots around T1-L3/4
Why do SNS nerves have short preganglionic and long post-ganglionic axons?
- Because the pre- and post-ganglionic nerves synapse in ganglia alongside the vertebral column.
- Can also synapse in dorsal thoracic and abdominal cavities.
What is the function of rami communications?
To carry sympathetic axons between the spinal nerve and sympathetic trunk.
What do white rami communicates do?
They carry pre-synaptic (myelinated) sympathetic neurones to ganglia
What do grey rami communicates do?
They carry post-synpatic (unmyelinated) sympathetic neurones back to the spinal nerve to the target.
For all regions of the body, what is the initial pathway for sympathetic pre-ganglionic axons?
Ventral root -> spinal nerve -> White rami communicans -> Sympathetic trunk
What is the pathway for sympathetic neurones for innervation to the body wall and limbs?
Sympathetic trunk -> Grey rami communicans -> Spinal nerve
What is the sympathetic pathway to the head?
Sympathetic trunk -> Ansa subclavia -> Cervical sympathetic trunk
Where does the sympathetic trunk lead into to innovate the abdomen and pelvis?
The major, minor and lumbar splanchic nerves.
What is the cervicothoracic formed from?
Fusion of the cervical and thoracic ganglia.
What does the ansa subclavia connect?
Connects the cervicothoracic ganglion to the middle cervical ganglion and the cervical sympathetic trunk
Where do splanchic nerves synapse in the abdomen?
- Coaeliac region
- Cranial mesenteric ganglion
- Caudal mesenteric ganglion
Where does the parasympathetic NS originate from?
From the brainstem and sacral segments of the spinal cord.
Why do parasympathetic nerves have long pre-synaptic and short post-synaptic neurones?
The parasympathetic nerves synapse in ganglia located close to or within the target organ.
What neurotransmitter is released from pre-synaptic parasympathetic neurones?
ACh
Where does the vagus nerve start/ stop?
Starts in the brainstem and reaches as far as the colon.
Where would you find rich vagal innervation?
In the heart and lungs
Where does the vagus nerve split into its dorsal and ventral branches?
Caudal to the root of the lung
Where do the dorsal and ventral branches pass through?
Left and right dorsal and ventral branches each fuse and pass through the diaphragm at the oesophageal hiatus.
How do the pelvic viscera receive its nerve supply?
Via the pelvic nerve
What is the vagosympathetic trunk?
This is where the vagus nerve and the cranial sympathetic trunk run together
What surrounds the vagosympathetic trunk?
A carotid sheath
