Intro to Endocrine Flashcards
Define Hormone
Ductless glands
Chemical signals secreted into the blood stream that act on tissues
Regulatory subtance produced that will elicit a response on a target cell (that has a specific receptor for that substance)
- 3 major classes
- Steroids
- Proteins/Peptides
- Amino Acid Analogues & Derivatives
Define Endocrine
- Endocrine = hormone
- Refers to ductless glands
- Chemical signals secreted into the bloodstream–> these act on tissues
Define Paracrine
- Hormone acts locally and diffuses in target cells in the neighborhood
- Elicits a response by binding to a receptor
- Exerts an effect on the cell next to it
Define Autocrine
- Hormone acts on the same cell that produced it
- Self secretion & self-response
Functions of the Endocrine System
- Maintian homeostasis (regulates bioenvironment)
- Growth and development of many tissues
- Bones & muscles
- Control reproduction
- Fertility
- Fetal growth and development
- nourishment of the newborn
How do endocrine organs work?
- Secrete hormones directly into the blood from the glandar cells
- Bind to receptors on target organ
- Elicit a response
3 types of arrangements:
- Discrete glands
- sole function is endocrine activity
- Endocrine components of other organs–> (ex. pancreas, ovary, testes)
- Ovary- cells to make eggs and cells to produce hormones
- Scattered cells throughout other organs (C cells in the thyroid)
Chemical Communication between cells in the Endocrine System
- Endocrine:
- Hormone secreted into the blood, binds to distant target cells via a receptor
- Secreted from a cell & travels a distance
- Hormone secreted into the blood, binds to distant target cells via a receptor
- Paracrine:
- Hormone acts locally and diffuses in target cells in the neighborhood
- ellicts a response by binding to a receptor (exerts an effect on the cell next to it)
- Hormone acts locally and diffuses in target cells in the neighborhood
- Autocrine:
- Hormone acts on the same cell that produced it
- self secretion & self-response
- Hormone acts on the same cell that produced it
Major Classes of Hormones:
Steroid #1
- Originate from a cholesterol precursor
- Changed into different hormones via enzymes
- Organs that secrete steroids:
- ovaries, testis, adrenal cortex
- Specific hormones:
- Mineralcorticoids, glucocorticoids, and testosterone, estradiol
Major Classes of Hormones:
#2 Protein/Peptide Hormones
- Name indicates the chemical structure
- Made up of amino acids
- Can have slight changes in the amino acid sequence = very different hormones
- Organs:
- Anterior pituitary
- Thyroid
- Parathyroid
- Pancreas
- Specific hormones: insulin, prolactin, antidiruetic hormone, oxytocin
Major Classes of Hormones:
#3 Amino Acid Analogs & Derivatives
- Named based on structure
- Organs:
- Thyroid gland
- Adrenal medulla
- Specific Hormones:
- Thyroxine
- Norepinephrine
- Epinephrine
- Most are derivatives of tyrosine
Hormone Receptors:
Synthesized hormone released from endocrine cell that makes it
No receptor for hormone = hormone will pass without binding to target tissue
If target cell has a receptor for that hormone, then it will bind to a receptor on the target cell and elicit a response.
Mechanisms of Hormone Action
Protein Hormones:
- Can’t just diffuse through lipid bilayer
- Need to bind a receptor
- 2nd messenger cascade
- Altered cell function & multiple biological effects
Steroid Hormones:
- Derivatives of cholesterol
- Can diffuse through the membrane b/c fat
- Bind to steroid receptors inside the cell
- Complex of hormone and receptor will bind to DNA in the cell
- Will elicit new protein production and biological effects
Control Mechanisms:
- External stimuli
- Will signal the endocrine action in the body so that organs will secrete certain hormones
- Fright, cold, light
- Internal stimuli
- Blood sugar levels, hormonal signals from another gland
- Feedback loops
- Positive vs. negative
- Long feedback loops (long distance to travel in the body)
- Short feedback loop (close proximity)
- Negative (turn on/turn off endocrine system)- ex. like a thermostat
- If levels are too high–> can negatively feedback to upstream organs to shut it off
- If levels are too low –> no negative feedback, will turn on system to produce more
Endocrine System Comparison
(Tissues, Hormones and their involvement)
Describe the main endocrine functions of the hypothalamus
Posterior Pituitary Hypothalamus Function:
- Synthesis of hormones released from posterior pituitary
- Oxytocin
- ADH (Vasopressin)
Communication with Posterior Pituitary =
Hypothalamic-Hypophyseal Nerve Tract
Anterior Pituitary Hypothalamus Function:
- Synthesis of regulating hormones that act on the anterior pituitary gland
- Release of regulating hormones that act on the anterior pituitary gland
- Releasing hormones (stimulating)
- Inhibiting hormones
- Done via feedback loops
- Ex. T4 thyroid hormone
Hypophyseal Portal System
Name the hypothalamic releasing and inhibiting hormones and briefly describe them
Hypothalamic Releasing Hormones:
- Corticotropin releasing hormone (CRH)
- Acts on the adrenal cortex
- Cortisol production
- Gonadotropin releasing hormone (GnRH)
- Endocrine cells of the gonads
- Androgen production
- Estrogen production
- Progesterone production
- Growth hormone releasing hormone (GHRH)
- Acts on GH
- Liver
- Somatomedins
- Nonendocrine targets = many tissues
- Growth hormone inhibiting hormone (GHIH)
- Acts on GH
- Liver
- Somatomedins
- Nonendocrine targets = many tissues
- Thyrotropin releasing hormone (TRH)
- Acts on TSH
- Thyroid gland stimulating
- Production of thyroid hormones
- Many tissues
- Prolactin releasing hormone (PRH)
- Prolacting hormone
- Mammary Gland (nonendocrine target)
- Dopamine or pro-lactin inhibiting hormone (PIH)
- Only non-peptide hormone
- Major inhibitor of prolactin
Name the primary hormones secreted from the posterior pitutary and describe their functions.
Describe the diseases/conditions that occur with insufficient or excess posterior pitutary hormones.
All (except 1) of the releasing/inhibiting hormones are associated to the hypothalamus.
Hypothalamus & Pituitary Gland
(interaction between these two is an interplay between the nervous system and the endocrine system)
- Base of brain (diencephalon)
- Lies below the 3rd ventricle at the base of the brain
- important regulator of endocrine action
Pituitary Gland (hypophysis)
- Endocrine gland connected to hypothalamus by infundibulum (stalk containing nerves and small blood vessels)
- Neurons that synthesize posterior pituitary hormones are made in the hypothalamus
- Require release signal
- Oxcytocin and Antidiruetic hormone (ADH)
Where are the neurons located that synthesize the hormones released from the posterior pituitary ?
Neurons that synthesize posterior pituitary hormones are made in the hypothalamus
Interaction between hypothalamus and anterior pituitary
Hypothalamus
- produces releasing hormones
- secreted in capillary beds from hypothalamus
- travel to anterior pituitary and bind to receptors there
- Stimulate anterior pituitary hormones (all protein hormones)
Relationship of the Hypothalamus and Anterior Pituitary
Form a complex unit–> transcends the boundary between neuro and endocrinology
Neuroendocrine system connected to endocrine system via portal circulation
- Requires releasing or inhibiting hormones
- made in the hypothalamus
- Secreted into the capillaries
- travel to the anterior pituitary to elicit a response
Endocrine roles of the Hypothalamus:
Specific endocrine functions:
-
Synthesis and release of regulating hormones that act on the anterior pituitary
- Releasing hormones
- inhibiting hormones
-
Synthesis of hormones released from the posterior pituitary
- Oxytocin
- Antidiuretic hormone (ADH) or Vasopressin (older name)
- Communicates with pituitary gland
- Hypothalamic-hypophyseal nerve tract (nerves that go from hypothalamus to posterior pituitary)
- Hypophyseal portal system (capillaries that communicate with anterior pituitary)
