- Hormones
2017-09-29 14:26:28
Today's Topics
Hormones
- Chemicals secreted into blood
- Act on specific target tissues via receptors
- Produce specific effects
Examples of substances that are both hormones and NTs
- Melatonin
- Epinephrine/adrenaline
- Oxytocin
- Vasopressin
Behaviors under hormonal influence
Behaviors under hormonal influence
- Ingestive (eating/ drinking)
- Fluid levels
- Na, K, Ca levels
- Digestion
- Blood glucose levels
Behaviors under hormonal influence
Behaviors under hormonal influence
- Reproduction
- Sexual Maturation
- Mating
- Birth
- Care giving
Behaviors under hormonal influence
Behaviors under hormonal influence
- Responses to threat/ challenge
- Metabolism
- Heart rate, blood pressure
- Digestion
- Arousal
What do these behaviors have in common?
- Biological imperatives
- Proscribed in space and time
- Foraging/hunting
- Find targets distributed in space, evaluate, act upon
- Often involve others
Principles of hormonal action
- Gradual action
- Change intensity or probability of behavior
- Behavior influences/influenced by hormones
- +/- Feedback
- Multiple effects on different tissues
Principles of hormonal action
- Produced in small amounts; released in bursts
- Levels vary daily, seasonally
- or are triggered by specific external/internal events
- Effect cellular metabolism
- Influence only cells with receptors
Differences between neural and hormonal communication
- Point to point vs.“broadcast”
- Wider broadcast than neuromodulators
- Fast vs. slow-acting
- Short-acting vs. long-acting
- Digital (yes-no) vs. analog (graded)
- Voluntary control vs. involuntary
Similarities between neural and hormonal communication
- Chemical messengers stored for later release
- Release follows stimulation
- Action depends on specific receptors
- 2nd messenger systems common
Where are hormones released
Where are hormones released?
- CNS
- Hypothalamus
- Pituitary
- Anterior
- Posterior
- Pineal gland
Where are hormones released
Where are hormones released?
- Rest of body
- Thyroid
- Adrenal (ad=adjacent, renal=kidney) gland
- Adrenal cortex
- Adrenal medulla
- Gonads (testes/ovaries)
Two release systems
- Direct
- Indirect
Direct hormone release into bloodstream
- Hypothalamus (paraventricular, supraoptic nucleus) to
- Posterior pituitary
- Oxytocin
- Arginine Vasopressin (AVP, vasopressin)
Direct release
Indirect release
- Hypothalamus -> releasing hormones
- Anterior pituitary -> tropic hormones
- End organs
Indirect release
Case studies
Case 1: Responses to threat or challenge
- Neural response
- Sympathetic Adrenal Medulla (SAM) response
- Sympathetic NS activation of adrenal medulla, other organs
- Releases NE and Epi
Case 1: Responses to threat or challenge
- Endocrine response
- Hypothalamic Pituitary Adrenal (HPA) axis
- Adrenal hormones released
- Hypothalamus
- Corticotropin Releasing Hormone (CRH)
- Anterior pituitary
- Adrenocorticotropic hormone (ACTH)
Case 1: Responses to threat or challenge
- Adrenal cortex
- Glucocorticoids (e.g., cortisol)
- Mineralocorticoids (e.g. aldosterone)
Adrenal hormones
- Steroids
- Derived from cholesterol
- Cortisol
- increases blood glucose, anti-inflammatory
- negative consequences of prolonged exposure
- Aldosterone
- Regulates Na (and water) retention in kidneys
Case 2: Reproductive behavior – the milk letdown reflex
- Supraoptic & Paraventricular nucleus (PVN) of hypothalamus releases oxytocin
- Into bloodstream via posterior pituitary (endocrine)
- Onto neurons in nucleus accumbens (neurocrine), amygdala, brainstem
Milk letdown reflex
Oxytocin's role
- Sexual arousal
- Released in bursts during orgasm
- Stimulates uterine, vaginal contraction
- Links to social interaction, bonding (Weisman and Feldman 2013)
- Alters face processing in autism (Domes et al. 2013)
- May inhibit fear/anxiety-related behaviors by gating amygdala (Viviani et al. 2011)
Oxytocin
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Melatonin
- Diurnal rhythm
- Night time peak, early morning low
- Secretion suppressed by "blue" light (< 460-480 nm)
- Rhythm irregular until ~3 mos post-natal (Ardura et al. 2003)
- Peak weakens, broadens with age
Melatonin circuitry
- Suprachiasmatic nucleus of the hypothalamus
- Paraventricular nucleus of the hypothalamus
- Spinal cord
- Superior cervical ganglion
- Pineal gland
How to think about neurochemical influences
- Measure hormones in blood, saliva; can't effectively measure NTs
- Multivariate, nonlinear, mutually interacting
- Varied time scales
- Phasic (e.g., cortisol in response to challenge)
- Periodic (e.g., melatonin; diurnal cortisol)
How to think about neurochemical influences
- Peripheral effects + neural feedback
- State variables and behavior
- Are your participants sleepy, hungry, horny, distressed…
- Endogenous & exogenous influences
Next time…
- How the human brain got this way…
References
Ardura, Julio, Regina Gutierrez, Jesus Andres, and Teresa Agapito. 2003. “Emergence and Evolution of the Circadian Rhythm of Melatonin in Children.” Horm. Res. 59 (2): 66–72. doi:68571.
Domes, Gregor, Markus Heinrichs, Ekkehardt Kumbier, Annette Grossmann, Karlheinz Hauenstein, and Sabine C. Herpertz. 2013. “Effects of Intranasal Oxytocin on the Neural Basis of Face Processing in Autism Spectrum Disorder.” Biological Psychiatry 74 (3): 164–71. doi:http://dx.doi.org/10.1016/j.biopsych.2013.02.007.
Ulrich-Lai, Yvonne M., and James P. Herman. 2009. “Neural Regulation of Endocrine and Autonomic Stress Responses.” Nature Reviews Neuroscience 10 (6): 397–409. doi:10.1038/nrn2647.
Viviani, Daniele, Alexandre Charlet, Erwin van den Burg, Camille Robinet, Nicolas Hurni, Marios Abatis, Fulvio Magara, and Ron Stoop. 2011. “Oxytocin Selectively Gates Fear Responses Through Distinct Outputs from the Central Amygdala.” Science 333 (6038). American Association for the Advancement of Science: 104–7. doi:10.1126/science.1201043.
Weisman, Omri, and Ruth Feldman. 2013. “Oxytocin Effects on the Human Brain: Findings, Questions, and Future Directions.” Biological Psychiatry 74 (3): 158–59. doi:http://dx.doi.org/10.1016/j.biopsych.2013.05.026.