Structure of Autonomic NS

Question 1

Explain actions controlled by the autonomic NS

Answer 1

• Involuntary actions

- Heart function, eye motions (ability to focus- accommodation and pupil dilation), saliva secretion

Question 2

Explain different branches of peripheral NS

Answer 2

• Somatic (controls voluntary skeletal muscle)
• Autonomic NS (smooth and cardiac muscle, some glands)
• Further divided into sympathic (gight or flight) and parasympathetic (rest and digest- also growth and maintenance)

Question 3

Explain actions of fight or flight response-

Answer 3

• Activating escape type processes and shutdown of non-essential systems
• Positive inotropy (more force) and +ve chronotropy (faster) heart beat
• Vasoconstriction in gut
• Vasodilation in skeletal muscle
• Greater sensory awareness e.g. eyes- focus and dilation
• Sweat secretion to cool down from large amounts of heat due to skeletal muscle contraction

Question 4

In a simple reflex (somatic NS) what neurons are involved- how does this differ in the automimic NS?

Answer 4

Receptor–> sensory neuron to spinal chord–> synapses with motor neuron –> effector muscle
(monosynaptic)
aka afferent to efferent nerve

In somatic single alpha spinal motorneurone
In autonomic- preganglionic neuron with cell body in CNS and post synaptic neuron with cell body in ganglion outside CNS

Question 5

Explain length of pre and post ganglionic neurons in autonomic NS

Answer 5

Sympathetic- short preganglionic neuron (due to ganglion in near para/prevertebral column) , long post ganglionic neuron
Parasympathetic- short pre-ganglionic neuron, short post ganglionic

Question 6

Explain divisions in the sympathetic NS

Answer 6

• Preganglionic fibres emerging from T1-L2 of spinal chord
• Paravertebral column (T1-L2) innervated by preganglionic fibres
• Prevertebral column- north of first thoracic vertebrae (above T1) - innervated by preganglionic fibres coming from T1-L2 of spinal chord
• Prevertebral ganglion (where pre and post ganglionic fibres synapse in prevertebral region) include superior mesenteric ganglion (end small intestine beginning large intestine), superior cervical ganglion (head and neck), celiac ganglion (stomach, liver, kidney, gall bladder, spleen, small intestine and ascending and transverse colon)

Question 7

Explain what the paravertebral chain is

Answer 7

• Part of autonomic sympathetic nervous system
• Coming out of the spinal chord at each spinal segment is the preganglion fibres
• At the paravertebral chain they innervate with post ganglionic fibres
• Interconnecting fibres links ganglion from each spinal level together

Question 8

Explain how structure of somatic and sympathetic nervous system differs

Answer 8

Somatic NS- cell bodies of preganglionic fibres located in dorsal root ganglion, synapse with efferent nerves in spinal column and via motor fibre innervate target organ
- Sympathetic- Afferent nerve enters through dorsal root- In the intermediate leteral column cell bodies of pregang