intro to the autonomic nervous system

Question 1

Name the two nerve roots that exit the spinal cord and describe their functions.

Answer 1

1. Anterior (ventral) nerve root:
   - carries motor signals from the CNS out to the peripheral muscles.
   - exits from the front side of the spinal cord so it can access the whole body much faster.
2. Posterior(dorsal) nerve root:
   - carries sensory signals from the periphery back into the CNS for interpretation.

Question 2

The dorsal and ventral nerve roots join together soon after exiting the spinal cord. What do they form?

Answer 2

They form the spinal nerves.

As such, each of the spinal nerves is mixed, containing sensory and motor neurons.

Question 3

How many spinal nerves are there?

Answer 3

31, consisting of:

8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.

Question 4

What is the swelling in the dorsal nerve root called?

Answer 4

This is the dorsal root ganglion.

It is a collection of sensory cell bodies.

Question 5

After the spinal nerves have left the spinal cord, they split for a second time. What do they form?

Answer 5

The spinal nerves split into:

1. Dorsal (posterior) rami and a
2. Ventral (anterior) rami

Question 6

What is the function of the dorsal (posterior) rami?

Answer 6

The dorsal (posterior) rami provide sensory and motor innervation to the muscles of the back at that level.

Question 7

What is the function of the ventral (anterior) rami?

Answer 7

The ventral (anterior) rami provide sensory and motor innervation to most of the body, and all the organs on the front side.

Question 8

How are ventral (anterior) rami organised?

Answer 8

They are organised into plexuses which means braids.

Question 9

What is the main nerve of the cervical plexus?

Answer 9

The phrenic nerve- the right and left phrenic nerves innervate the diaphragm.

Question 10

What is the major nerves of the brachial plexus?

Answer 10

The axillary, musculocutaneous, median, ulnar and radial nerves.

Question 11

What is the major nerve of the lumbar plexus?

Answer 11

The major nerve is the femoral nerve, which runs on the side of the femoral artery under the inguinal ligament.

Question 12

what is the major nerve of the sacral plexus?

Answer 12

The sciatic nerve. It is the largest nerve in the whole body, and runs down the back of the legs.

Question 13

What is a dermatome?

Answer 13

A dermatome refers to a region of skin innervated by the sensory fibres from a designated spinal nerve.

Question 14

What is a myotome?

Answer 14

A myotome refers to a group of muscles innvervated by the motor fibres from a designated spinal nerve.

Question 15

What two systems can the peripheral nervous system be divided into?

Answer 15

The peripheral nervous system can be split into the:

1. Afferent system (nerves going to the CNS)
2. Efferent system (nerves coming from the CNS)

Question 16

The efferent division of the peripheral nervous system refers to the nerves coming from the CNS to the periphery. What two systems can the efferent division be divided into?

Answer 16

the efferent division can be split into:

1. Somatic nervous system (nerves carrying motor instructions to voluntary muscle in the periphery)
2. Autonomic nervous system (nerves carrying the instructions and signals for all the involuntary processes in the body).

Question 17

The autonomic nervous system regulates all the involuntary processes of the visceral organs and smooth muscle. This system can be split into two smaller divisions, which are?

Answer 17

The autonomic nervous system:

1. The parasympathetic nervous system (rest and digest)
2. Sympathetic nervous system (fight and flight)

Question 18

What is the structure of the neurons of the parasympathetic and sympathetic nervous systems?

Answer 18

There is a preganglionic neuron, and a postganglionic neuron.

Question 19

Describe the length of the sympathetic nervous system’s pre and postganglionic nerves

Answer 19

the sympathetic neurons have short preganglionic and long postganglionic neurons. (coming from the sympathetic chain ganglion)

Question 20

Describe the length of the parasympathetic nervous system’s pre and postganglionic nerves.

Answer 20

The parasympathetic neurons have a long preganglionic neuron and a short postganglionic neuron (coming from the vagus nerve).

Question 21

What is the neurotransmitter released from the preganglionic neurons of both the parasympathetic and sympathetic nervous systems?

Answer 21

Acetylcholine.

Question 22

What is the neurotransmitter released from the postganglionic neurons of the parasympathetic and sympathetic nervous systems?

Answer 22

parasympathetic NS- still acetylcholine

sympathetic NS- noradrenaline/adrenaline

Question 23

Name the two types of adrenergic receptors and the describe their structure.

Answer 23

There are the alpha and beta adrenergic receptors.

These receptors are g-protein coupled receptors that send the message via the second messenger cascade.

Question 24

Name and describe the role of the alpha adrenergic receptors?

Answer 24

Alpha-1 receptors: excitatory of smooth muscle, causes brochoconstriction and vasoconstriction.
Alpha-2 receptors: they switch off sympathetic stimulation to the A1’s from NA/A when the constriction is too much (negative feedback).

Question 25

Name and describe the role of the beta adrenergic receptors?

Answer 25

Beta-1 receptors: excitatory of cardiac muscle, increases cardiac output.
Beta-2 receptors: inhibitory of smooth muscle, causes bronchodilation and vasodilation.
Beta-3 receptors: lipolysis of adipose cells

Question 26

What does the drug Prazosin do with regard to adrenergic receptors?

Answer 26

Prazosin is an alpha-1 antagonist drug.

It is used as an antihypertensive drug because it stops vasoconstriction and decreases TPR.

Question 27

What does the drug Atenolol do with regard to adrenergic receptors?

Answer 27

Atenolol is a beta-1 receptor antagonist drug, it is used as an antihypertensive drug because it decreases cardiac output.

Question 28

what does the drug Salbutamol do with regard to adrenergic receptors?

Answer 28

Salbutamol is a beta-2 receptor agonist. It activates b2 receptors to induce bronchodilation, and thus it is used to treat asthma and COPD.

Question 29

Name and describe the two kinds of cholinergic receptors?

Answer 29

Nicotinic receptors- they are found at neuromuscular junuctions and synapses of both parasympathetic and sympathetic NS and facilitate voluntary movement. They are ion channels that allow Na+ influx for AP propagation.

Muscarinic receptors-they are found in the parasympathetic NS only and are g-protein receptors.

Question 30

Name and describe the function of the three different types of muscarinic receptors?

Answer 30

M1- neural and excitatory, found in the CNS and promotes neuronal firing.
M2- inhibitory, found on cardiac tissue, decreases cardiac output.
M3-glandular tissue and smooth muscle, excitatory. Promotes salivation, lacrimation and sweating.

Question 31

What do the drugs Ipratropium and tiotropium do with regard to muscarinic receptors?

Answer 31

Ipratropium and tiotropium are both muscarinic receptor blockers (with a complex mechanism) that increase bronchodilation.