w2 the autonomic nervous system

Question 1

What are afferent neurons?

Answer 1

Recieve incoming information from sensory receptors

Question 2

What are efferent neurons?

Answer 2

Transmit information to other neurons or effector organs/tissues

Question 3

What are synapses?

Answer 3

Specialised regions where information is passed between neurones on a cell to cell basis.
Allows neurons to be considered post or pre-synaptic.

Question 4

Explain the hierarchy of the nervous system

Answer 4

The first branch splits into the central (brain or spinal cord) or the peripheral nervous system.
The peripheral nervous system then splits into the somatic or the autonomic nervous system.
The autonomic then splits into the parasympathetic and the sympathetic division.

Question 5

What is the difference between the somatic and the autonomic nervous system?

Answer 5

The somatic -sensory and motor innervation of skeletal muscles, voluntary
Autonomic - sensory and motor innervation of smooth muscle, cardiac muscle and glands, involuntary.

Question 6

What makes up the peripheral nervous system?

Answer 6

31 pairs of spinal nerves:
8 cervical (note only 7 cervical vertebrae so stops
above c1)
12 thoracic
5 lumbar
5 sacral
1 coccygeal
12 pairs of cranial nerves.

Question 7

What is sensory innervation?

Answer 7

Detects heat, pressure, vibration, pain, location of limbs and chemical concentration.

Question 8

What is motor innveration?

Answer 8

Helps with movement and function.

Question 9

What is the somatic nervous system?

Answer 9

Innervates structures derived from somites including skeletal muscle and skin.
Can be sensory or motor.
Respond to external stimuli to cause voluntary movement.

Question 10

What is the autonomic nervous system?

Answer 10

Innervates viscera, glandular and smooth muscle.
Has visceral afferent and efferent fibres
Can be motor or sensory
Responds to information from internal stimuli to cause involuntary processes.

Question 11

What is the sympathetic nervous system?
What are some of its effects?

Answer 11

Branch of autonomic nervous system
Acts in time of stress in flight or fight response
Causes increased heart rate, increased blood pressure and increased blood flow to heart and muscles through vasodilation
Dilates pupils
Decreases blood flow to the extremities and GI tract through vasoconstriction.

Question 12

What is the parasympathetic nervous system?
What are some of its effects?

Answer 12

Branch of the autonomic nervous system.
Stimulates the rest and digest response.
Decreases the heart rate and force on contraction to decrease the blood pressure.
Increases blood flow to the extremities to the Gi tract and extremities
Decreasing blood flow to the heart and muscles
Constricts the pupils.

Question 13

What is meant by the parasympathetic or sympathetic tone?

Answer 13

Two systems normally act in homeostasis, tone refers to the activeness of one system over the other at any one time.

Question 14

What does topography mean in terms of anatomy?

Answer 14

The distribution of parts or features on the surface or within an organ or organism.

Question 15

Draw a diagram to show the basic structure of typical a spinal nerve.

Answer 15

Question 16

What are the similarities and differences between the dorsal and ventral roots?

Answer 16

Both connect from the vertebrae to the spinal nerve.
Dorsal root is posterior is solely sensory neurons and synapses with the grey matter in the dorsal horn.
Ventral Root is Anterior, is solely motor neurons and synapses with the grey matter in the ventral horn.

Question 17

Where does a synapse form?

Answer 17

Between the terminal buttons of one neuron and the dendrites of another.

Question 18

What are some features of the spinal nerve?

Answer 18

Contains all fibres travelling out of/into the ventral and dorsal root,
Also splits into the ventral and dorsal rami.

Question 19

What is the deal with the ventral and dorsal rami?

Answer 19

Ventral rami innervates anterior and lateral aspects of the body
Dorsal rami innervates the posterior aspects of the body.
All pass information with the spinal nerve.

Question 20

What is meant by a mixed nerve?
What are some examples of this?

Answer 20

Mixed carry both sensory and motor fibres
Dorsal ramus, ventral ramus and the spinal nerve.

Question 21

Describe the pathway of a somatic sensory nerve.

Answer 21

The afferent neurone runs from the receptor along the dorsal/ventral ramus into the spinal nerve.
Sensory innervation travels through the dorsal root to synapse in the dorsal horn.
The efferent neuron then runs from the ventral horn to the ventral root into the spinal nerve.
Then back along the dorsal or ventral ramus to synapse at the effector muscle providing motor innervation.

Question 22

Explain the structure of somatic nerves?
What neurotransmitters are produced?

Answer 22

Both afferent and efferent nerves produce acetylcholine
afferent - cell bodies lie in the dorsal root ganglion with axons extending in tow directions
efferent - cell bodies lie in the ventral horn of grey matter in the spinal cord, with axons extending only in one direction.

Question 23

Explain the origins of the autonomic nervous system from the spinal cord?

Answer 23

Sympathetic sandwhich
Sympathetic is described as thoracolumbar as arises from T1 to L2
Parasympathetic is described as craniosacral as arises from brainstem and spinal nerves S2-4.

Question 24

Describe the structure of motor pathways within the autonomic nervous system?

Answer 24

Motor pathway always consists of a pre and post synaptic/ ganglionic fibre
Synapses are always within ganglia.

Question 25

What is the structure of a sympathetic efferent neurone?

Answer 25

The pre-ganglionic efferent fibre orignates in the lateral horn,
Travels through ventral root, spinal nerve and associated ramus.
Travels through white or myelinated ramus communications to enter the sympathetic ganglion where synapse occurs.
Post synaptic ganglion leaves by grey/unmyelinated ramus communication.
Travels through ramus to find target.

Question 26

What is a lateral horn indicate?

Answer 26

Only found in thoracic and lumbar vertebrae as only for sympathetic innervation.

Question 27

What is the function of the sympathetic trunk?

Answer 27

Once some efferent sympathetic fibres have entered the sympathetic ganglion, they may travel up or down the sympathetic trunk to leave in the grey ramus communications from other sympathetic ganglion.

Question 28

What is the synaptic patterns of splanchnic nerves?

Answer 28

pass through the sympathetic trunk without synapsing within it.
They synapse in prevertebral ganglia instead. (anterior to vertebrae and aorta, often when aorta branches)
The post synaptic ganglion then follows the blood vessels to supply sympathetic (mostly) innervation to the target organ.

Question 29

What do splanchnic nerves target?

Answer 29

Organs

Question 30

Explain the journey of travel of the pulmonary plexus.

Answer 30

Orignate from T1-T4.
Synapse in the sympathetic trunk
Innervate the lungs.
Sympathetic

Question 31

Explain the journey of the cardiac plexus.

Answer 31

Arise from cervical ganglia and synapses in the sympathetic chain from T1-T4.
innverate the heart
Sympathetic

Question 32

What sympathetic fibres do not synapse in the sympathetic trunk?

Answer 32

Splanchnic nerves

Question 33

What neurotransmitters are released normally by sympathetic nerves?

Answer 33

In the sympathetic ganglion acetylcholine is released.
At target tissue noradrenaline is released.

Question 34

Describe the pathway of an efferent parasympathetic neuron.

Answer 34

Efferent neuron runs through the ventral horn of grey matter.
Along the ventral root into the spinal nerve then along the ventral or dorsal ramus.
Synapses in a ganglion before reaching a target organ.

Question 35

What is important to note about parasympathetic ganglion?

Answer 35

Located very close to the target organ so pre-ganglionic parasympathetic fibres travel the majority of the way until reaching the near-surface of the organ then synapsing to a post synaptic neuron.

Question 36

Why is the vagus nerve important?

Answer 36

Provides all parasympathetic innervation from the neck down to the midgut.
Arises from CN X.

Question 37

What neurotransmitter is released by parasympathetic fibres?

Answer 37

Acetylcholine
ALWAYS - in ganglion and at the target organ.

Question 38

What is pathway and role of a visceral afferent?

Answer 38

Transmitts sensations of visceral pain or fullness to CNS.
Follow the same path as somatic afferents.
Cell bodies lie in the dorsal Root Ganglia

Question 39

Compare the length of neurons within the parasympathetic and sympathetic neurons?

Answer 39

PS - long pre synaptic and short post synaptic
S - short pre synaptic and long post synaptic.