Autonomic Nervous System

Question 1

What 4 things does the autonomic nervous system innervate?

Answer 1

Visceral structures
Glandular myoepithelium
Adipose tissue
Vasculature and cardiac tissue

Question 2

What is the autonomic nervous system and what is its function?

Answer 2

It is an involuntary system that aims to preserve a constant internal environment (homeostasis)

Question 3

What are the 2 subdivisions of the ANS?

Answer 3

• Parasympathetic (rest and digest)
• Sympathetic (fight or flight)

Question 4

Where does the parasympathetic NS arise from?

Answer 4

Parasympathetic arises from brain and sacral spinal cord

Question 5

Where does the sympathetic NS arise from?

Answer 5

Sympathetic arises from the thoraco-lumbar spinal cord.

Question 6

What does it mean to have dual innervation?

Answer 6

Each organ receives innervation from both sympathetic and parasympathetic nerve axons.

Question 7

What happens when there is sympathetic dominance?

Answer 7

• Increased heart rate
• Decreased digestion
• Pupils dilate

Question 8

What happens when there is parasympathetic dominance?

Answer 8

• Decreased heart rate
• Increased digestion
• Pupils constrict

Question 9

An autonomic pathway consists of a 2-neurone chain, where do these two neurones synapse?

Answer 9

In a ganglion

Question 10

What is different about the post-ganglionic neurone?

Answer 10

It is normally unmyelinated.

Question 11

What neurotransmitter is released with the sympathetic nervous system?

Answer 11

Norepinephrine

Question 12

What neurotransmitter is released with the parasympathetic nervous system?

Answer 12

Acetylcholine

Question 13

Are the pre- and post-ganglionic neurones of the autonomic NS afferent or efferent?

Answer 13

They are efferent neurones

Question 14

What neurotransmitter do pre-ganglionic neurones always release?

Answer 14

Pre-ganglionic neurones release ACh

Question 15

What are the advantages and disadvantages of using two different neurones in the autonomic system?

Answer 15

• 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)

Question 16

What type of ganglia do you find coming out on either side of the spinal cord?

Answer 16

Paravertebral ganglia

Question 17

Which parts of the brain control the sympathetic and parasympathetic nervous systems?

Answer 17

• Rostral hypothalamus influences the parasympathetic system
• Caudal hypothalamus influences the sympathetic system

Question 18

What are the 5 different components to a reflex arc in the autonomic nervous system?

Answer 18

• Sensory receptor
• Sensory neurone (afferent)
• Integrating centre
• Pre- and post-ganglionic motor neurones
• Visceral effectors

Question 19

Where does the sympathetic nervous system originate and leave from?

Answer 19

• The lateral/ intermediate horn of the thoracolumbar spinal cord.
• It leaves via ventral roots around T1-L3/4

Question 20

Why do SNS nerves have short preganglionic and long post-ganglionic axons?

Answer 20

• Because the pre- and post-ganglionic nerves synapse in ganglia alongside the vertebral column.
• Can also synapse in dorsal thoracic and abdominal cavities.

Question 21

What is the function of rami communications?

Answer 21

To carry sympathetic axons between the spinal nerve and sympathetic trunk.

Question 22

What do white rami communicates do?

Answer 22

They carry pre-synaptic (myelinated) sympathetic neurones to ganglia

Question 23

What do grey rami communicates do?

Answer 23

They carry post-synpatic (unmyelinated) sympathetic neurones back to the spinal nerve to the target.

Question 24

For all regions of the body, what is the initial pathway for sympathetic pre-ganglionic axons?

Answer 24

Ventral root -> spinal nerve -> White rami communicans -> Sympathetic trunk

Question 25

What is the pathway for sympathetic neurones for innervation to the body wall and limbs?

Answer 25

Sympathetic trunk -> Grey rami communicans -> Spinal nerve

Question 26

What is the sympathetic pathway to the head?

Answer 26

Sympathetic trunk -> Ansa subclavia -> Cervical sympathetic trunk

Question 27

Where does the sympathetic trunk lead into to innovate the abdomen and pelvis?

Answer 27

The major, minor and lumbar splanchic nerves.

Question 28

What is the cervicothoracic formed from?

Answer 28

Fusion of the cervical and thoracic ganglia.

Question 29

What does the ansa subclavia connect?

Answer 29

Connects the cervicothoracic ganglion to the middle cervical ganglion and the cervical sympathetic trunk

Question 30

Where do splanchic nerves synapse in the abdomen?

Answer 30

- Coaeliac region - Cranial mesenteric ganglion - Caudal mesenteric ganglion

Question 31

Where does the parasympathetic NS originate from?

Answer 31

From the brainstem and sacral segments of the spinal cord.

Question 32

Why do parasympathetic nerves have long pre-synaptic and short post-synaptic neurones?

Answer 32

The parasympathetic nerves synapse in ganglia located close to or within the target organ.

Question 33

What neurotransmitter is released from pre-synaptic parasympathetic neurones?

Answer 33

ACh

Question 34

Where does the vagus nerve start/ stop?

Answer 34

Starts in the brainstem and reaches as far as the colon.

Question 35

Where would you find rich vagal innervation?

Answer 35

In the heart and lungs

Question 36

Where does the vagus nerve split into its dorsal and ventral branches?

Answer 36

Caudal to the root of the lung

Question 37

Where do the dorsal and ventral branches pass through?

Answer 37

Left and right dorsal and ventral branches each fuse and pass through the diaphragm at the oesophageal hiatus.

Question 38

How do the pelvic viscera receive its nerve supply?

Answer 38

Via the pelvic nerve

Question 39

What is the vagosympathetic trunk?

Answer 39

This is where the vagus nerve and the cranial sympathetic trunk run together

Question 40

What surrounds the vagosympathetic trunk?

Answer 40

A carotid sheath