Learning Diary, Week 5

This week’s reading was about the chemical control of the brain and behavior, and in this blog I will summarize my takeaways from the text. Three interconnected systems were detailed: the secretory hypothalamus, autonomic nervous system (ANS), and diffuse modulatory systems.

Transmitters in this chapter are synonymous with their corresponding system. the sympathetic nervous system is noradrenergic, and is involved with the “4 F’s” (“fright, flight, fight, and sex,” as it said in the textbook – it took me a moment to process why it listed only 3 f’s). Raphe, (from the Greek “ridge”) are 9 nuclei on either side of the midline of the brain stem which are seratonergic, and are involved in regulating consciousness levels. Dopaminergic diffuse modulatory systems exist in the substantia nigra, which is important for voluntary motor control.

To condense these transmitter links further:

Sympathetic nervous system 🔗 noradrenergic
Raphe 🔗 serotonin
Substantia nigra 🔗 dopamine

Each of these systems are important for regulating brain homeostasis, which is like the internal and biological cybernetic system that keeps everything functioning smoothly. For instance, the hypothalamus maintains temperature & blood composition while the ANS takes care of blood pressure, and raphe nuclei regulate sleep/wake cycles and mood.

Here are the key terms from the chapter with short definitions:

The Secretory Hypothalamus
homeostasis – Internal environment maintenance
periventricular zone 1 of the 3 funtional hypothalamus zones. Receives inputs from other 2.
magnocellular neurosecretory cell – The largest of the hypothalamus neurosecratory cells. Axons extend from pituitary stock to posterior lobe. Release neurohormones into bloodstream.
neurohormone – peptides released into blood by neurons include oxytocin (so called “love hormone”) & vasopressin
antidiuretic hormone (ADH) – also called vasopressin, ADH regulates blood volume and salt concentration.
parvocellular neurosecretory cell – hypothalamic neurons that communicate via the bloodstream and secrete hypophysiotropic hormone.
hypothalamo-pituitary portal circulation – a series of small veins that connect hypothalamus and pituitary gland, where neurohormones are spread.
adrenal cortex – located just above the kidneys, this area contains the adrenal medulla, which is involved in the production of coritsol.
cortisol – a steroid that is released to mobilize systems in a stress response.

The Autonomic Nervous System
sympathetic division –
a series of ganglia on the side of the vertibral column, involved with noradrenaline.
parasympathetic division –
involved with maintaining long term processes like digestion
autonomic ganglia – peripheral ganglia of the ANS
postganglionic neuron – soma lies in the ANS, axons terminiate in organs/tissues.
preganglionic neuron – soma lies in CNS, axons terminate peripherally to synapse with postganglionic neurons
sympathetic chain – series of ganglia next to the spinal column
enteric division – a unique neural system or “little brain” of the ANS located inside various organs.

The Diffuse Modulatory Systems of the Brain
diffuse modulatory system –
axons projecting in multiple directions, thought to regulate mood and arousal.
locus coeruleus – from the latin for “blue spot,”  its diffuse axon projections can make more than 250,000 synapses
raphe nuclei – ridges on either side of brain stem involved with serotonin.
basal forebrain complex – part of a diffuse modulatory cholinergic system, medial and ventral to the basal ganglia.

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