Week 3 CNS regulation of the Autonomic Nervous System

Question 1

What is the primary function of the hypothalamus?

Answer 1

• Particularly the PVN (paraventricular nucleus) is the master controller of homeostasis
• receives input about temp, pressure, electrolytes, fluid, weight
• sends
  1. neural and hormonal signals to pituitary gland-modulate endocrine function
  2. neural signals to ANS to coordinate parasymp and symp nervous system

Question 2

Describe the connections between the hypothalamus and ANS that allows it to control autonomic responses.

Answer 2

Efferent connections reciprocal to afferent ones
Hypothalamus to Brain Stem
1. medial forebrain bundle (MFB): in dorsolateral tegmentum
2. dorsal longitudinal fasciculus (DLF)
3. mamillotegmental tract (MTegT)
Hypothalamus to spinal cord-ill defined
4. hypothalamo-spinal tract: in lateral part of medulla and ends on lateral horn of symp/pre neurons

Question 3

Describe the sympathetic medullary regulating center and how it controls cardiovascular function.

Answer 3

NTS=nucleus tractus solitarius

1. Neurons in NTS in medulla assess bp changes from baroreceptors fibers (via CN IX and X) and top down input from hypothalamus
   - Increased input (high bp)–>inhibit activity in RVLM and decrease sympathetic tone to heart
   - decreased input (low bp)–>reduce inhibition at RVLM and increase sympathetic tone

Question 4

What are the medullary regulating centers for regulation of CV function?

Answer 4

1. NTS=nucleus tractus solitarius
2. DMV=dorsal motor nucleus of vagus
3. NA=nucleus ambiguus (IX, X)

Question 5

Describe the parasympathetic medullary regulating center and how it controls cardiovascular function.

Answer 5

1. NTS projects to DMN and NA of CN X to modulate parasympathetic innervation to heart
   - increased input (high bp)–>increase parasympathetic tone and decrease hr
   - decreased input (low bp)–>decrease parasympathetic tone

Question 6

What lesions can cause Horner’s syndrome? (interruption of sympathetics)

Answer 6

1. peripheral lesions
   - unilateral lesion to superior cervical ganglion
   - preganglionic cell bodies in T1-T4
   - postganglionic cell bodies in superior cervical ganglion -unilateral
2. Central lesions
   - medulla (lateral medullary syndrome)- unilateral Horner’s due to vascular lesion of PICA
   - Cervical spinal cord injury (bilateral Horners)

Question 7

What results from isolated unilateral parasympathetic lesions of the CN IX ?

Answer 7

little effect because of bilateral distribution from nerve to target
-also uncommon

Question 8

What are the effects of lesions affecting the oculomotor nerve CNIII parasympathetics? (e.g. uncal herniation)

Answer 8

-mydriasis: dilated pupils
-loss of light reflex
-loss of accommodation
Lesion of somatomotor part of CNIII also causes
-“big” ptosis-loss of innervation to levator palpebrae superioris

Question 9

What symptoms result from parasympathetic pathology from central lesion in pons or tumor at internal acoustic meatus affecting CN VII?

Answer 9

• dry eye/loss of tears

- dry mouth

Question 10

What symptoms result from somatomotor pathology from central lesion in pons or tumor at internal acoustic meatus affecting CN VII?

Answer 10

• facial paralysis on one side of lower face, drooping corner of mouth
• frontalis and obicularis oculi remain intact due to bilateral innervation by UMNs