Lecture 26- Hypothalamus + Pituitary gland Flashcards
What is endocrinology?
The study of hormones, their receptors and their intracellular signaling pathways
What are hormones?
Hormones are chemical messengers produced in one location and transported to a second location (target cells) where they exert their effects. Hormones often
reach their targets via the bloodstream.
Do concentrations of hormones need to be high in order to have an effect?
No, work at low concentrations
What are the principle functions of the endocrine system?
- Maintain homeostasis: a stable internal environment in the face of a changing external environment, example: dehydration
- Regulation of growth and development
- Control energy storage and use
- Mediate the body’s response to environmental cues
What are the four types of hormone communication in the body?
- Autocrine= Hormone produced by the very cell it acts on
- Paracrine= Hormone acts on a a different cell than to where it was produced but this cell is close by (localized)
- Endocrine= Hormone travels in blood stream to act on cell far away/ distant
- Neurocrine= Like endocrine but the cell that produces the initial hormone is a neuron
What are some chemical classifications of hormones?
Peptides – ca. ≤ 50 amino acids
Proteins – ca. ≥ 50 amino acids
Amines – derivatives of tyrosine (amino acid)
Steroids – synthesized from cholesterol
Prostaglandins – synthesized from arachidonic acid
What are the four potential outcomes for hormones that are secreted into the bloodstream?
- Excreted in urine + feces
- Inactivated by metabolism
- Goes directly to target cells which has specific receptor
- Activated by metabolism then goes on to complete 3 (in this case would have been released from the endocrine cell as a precursor)
What is synergy? What is the alternative?
- The sum is better than the parts. Hormones can have a greater effect when they are released in unison and can facilitate each other’s actions
- Additive effect: when both effects simply add, so get a line that is double that from the action of one. It’s not synergy though i.e. the action of one isn’t enhanced by the other as such
What are some endocrine glands that are often missed?
- Sweat glands
- Adipose tissue
What is the circadian rhythm? What controls it? What parts of brain are involved?
- Body clock
- Controls lots of physiological processes. Alertness, temperature etc.
- Clock resides in the superchiasmatic nucleus in the hypothalamus
- Zeitgeber= time keeper (external cues), adjusts the circadian rhythm to align with light as our natural body clock runs a bit longer than 24 hours
- Melatonin= produced in pineal gland (small gland at base of brain) is released as a Zeitgeber and provides feedback to the hypothalamus. Light inhibits melatonin production. Melatonin therefore high at night/ associated with sleep.
What processes is the pituitary gland response for?
-Water balance
-Metabolism
-Body growth
-Reproduction
=Milk secretion
What are the two ‘sections’ of the pituitary gland?
- Anterior
- Posterior (technically part of the brain)
How does the hypothalamus control release from the anterior pituitary?
- Cell bodies in hypothalamus, produce hormones (inhibiting and releasing hormones) that travel via the portal veins and effect glands in the anterior pituitary.
- More hormones produced at glands here and these travel into the blood stream to act on target organs
What is the medial eminence?
Makes sure brain is in contact with blood in both directions. Neurons connect into this blood stream.
Draw the axis on slide 15 showing hormone release from the hypothalamus, effect on the anterior pituitary and then impact of peripheral target tissues….
Answers are on slides
