ANS, Hypothalamus, & Limbic System

Question 1

Function of the ANS

Answer 1

Maintains homeostasis - maintenance of an optimal internal environment by regulating activity of internal organs and vasculature

Influenced by Hypothalamus

Question 2

Receptors of the ANS (4)

Answer 2

1. Mechanoreceptors - pressure & stretch
2. Chemoreceptors - chemical changes in blood
   - impt in hypothalamus
3. Nociceptors - stretch & ischemia (viscera & walls of arteries)
4. Thermoreceptors - temp change of circulating blood
   - hypothalamus

Question 3

Afferent vs. Efferent Pathways of the ANS

Answer 3

Afferent - info from visceral receptors to the CNS
–> via dorsal roots in SC OR CN VII, IX and X (taste) and IX/X (info from viscera)

Efferent - info from CNS to the viscera or periphery
–> Sympathetic or Parasympathetic

Question 4

Sympathetic Nervous System

• function
• cell bodies

Answer 4

“fight or flight”

Function: maintain optimal blood supply (main), body temp & metabolic rate, regulate activity of viscera

**preganglionic cell bodies are located in the lateral horn of T1-L2

Question 5

Parasympathetic Nervous System

• function
• cell bodies

Answer 5

“rest & digest”

Function: energy conservation & storage (dec cardiac activity, facilitates digestion and regulates activity of viscera)

**preganglionic cell bodies are located in either brainstem or sacral spinal cord (S2-S4)

CN Nuclei in BS involved w/ PNS:

• CN III: pupillary reflex, ciliary muscles
• CN VII: lacrimal & salivary gland
• CN X - all viscera besides colon, bladder and external genetalia

Question 6

PNS Output Pathway

Answer 6

Hypothalamus –> CN nuclei –> organ/gland (via CN)

Question 7

SNS Output Pathway

Answer 7

Hypothalamus –> lateral horn of T1-S2 –> SNS preganglionic neuron –> paravertebral ganglia –> SNS postganglionic neuron –> organ/gland/vessel

Question 8

Central Regulation of the ANS - pathway

Answer 8

1. info enters BS and converges on solitary nucleus
2. info from solitary nucleus is relayed to viscera control areas in pons/medulla
3. relayed to modulatory areas of hypothalamus, thalamus & limbic system

Question 9

Central Regulation of the ANS

• medulla
• pons
• hypothalamus, thalamus & limbic system

Answer 9

• Medulla: regulates HR, respiration, vasoconstriction/dilation - via ANS efferent neurons & vagus nerve
• Pons: regulates respiration
• Hypothalamus: MASTER controller of ANS
• -> only direct connection to hypothalamus is the olfactory system

Thalamus projects info to limbic system IF emotions are involved

Question 10

Olfactory Pathway

Answer 10

nasal receptor –> olfactory bulb (via olfactory nerve) –> hypothalamus (via olfactory tract) –> medulla and pons to regulate ANS (OUTPUT)

Hypothalamus –> limbic system IF emotion is involved

Question 11

Peripheral Nerve Injury in the ANS

Answer 11

loss of vascular control, temp regulation and sweating

may lead to trophic changes in the skin

Question 12

Spinal region injury of the ANS

• S2-S4
• above sacral cord
• above T6

Answer 12

disrupts ascending and descending pathways of the ANS at the level of the lesion

S2-S4 = flaccid bladder
Above sacral cord = hypertonic/hyperreflexive bladder (b/c controlled by the S2-S4 sacral plexuses)

lesion above T6 prevents SC from receiving signals from brain to inhibit SNS so can cause autonomic dysreflexia