Chapter 45: Hormones and the Endocrine System Flashcards
Hormones
- Signaling molecules
- Communicate regulatory messages throughout the body (pass through the bloodstream)
Endocrine System
- 1 of 2 basic systems for communication and regulation (in the animal body)
- Chemical signaling = function
- Slow
Nervous System
- 1 of 2 basic systems for communication and regulation (in the animal body)
- Network of specialized cells that transmit signals along dedicated pathways (regulate endocrine cells, muscle cells, and neurons)
Local Regulators
- Molecules that act over a short distance
- Reach their target through diffusion
Paracrine
Target cells lie near the secreting cells
Autocrine
Secreting cells are the target cells
Prostaglandin
- Local regulator
- Mediates signaling
- Acts in reproductive organs and in the immune system
- Helps regulate aggregation of platelets
- A modified fatty acid
Neurotransmitters
- Diffuse at a very short distance
- Bind to receptors on target cells
Neurohormone
- Molecule that is secreted by a neuron
- Travels in body fluids
- Acts on specific target cells, changing their functioning
Pheromones
- Chemicals released externally into the environment
- Functions:
- defining territories
- warning of predators
- attracting potential mates
Nitric Oxide (NO)
- Functions as a neurotransmitter and local regulator
- Released when blood oxygen levels fall
- Activates enzyme to relax cells, increasing blood flow to tissues
Signal Transduction
- Series of changes in cellular proteins
- Changes the extracellular chemical signal to an intracellular response
Epinephrine
- Adrenaline
- Causes cAMP to be synthesized and activation can cause glycogen breakdown
- Glucose is released into the bloodstream to fuel the fight/flight response
- A catecholamine
- Secreted by the adrenal medulla
Endocrine Glands
- Ductless organs made up of endocrine cells
- Release hormones directly into surrounding fluid
Oxytocin
- Hormone released by posterior pituitary
- Signals milk production in mammary glands
- Stimulates contraction of smooth muscle cells in uterus
Negative Feedback
- Response reduces initial stimulus
- Helps restore to standing prior to stimulus
- Like an on/off switch
Positive Feedback
- Response causes reinforcement of stimuli
- Continued response
Hypothalamus
- Region of the brain
- Coordinates endocrine signaling in vertebrates
Pituitary Gland
- Located at the base of the hypothalamus
- Receives signals from that gland
- Master gland
Posterior Pituitary
- Extension of the actions of the hypothalamus
- Releases oxytocin and vasopressin (antidiuretic hormone)
Anterior Pituitary
Synthesizes and secretes hormones in response to hypothalamus ones
Antidiuretic Hormone (ADH)
- Functions in regulating the kidneys
- Also called vasopressin
- Secreted by the posterior pituitary
- Role in social behavior
Prolactin
- Hormone produced and secreted by the anterior pituitary
- Diversity of effects in different vertebrate species
- Stimulates growth and milk production by the mammary glands in mammals
Tropic Hormones/Tropins
Anterior pituitary hormones in a hormone cascade pathway
Thyroid Hormone
- Regulates bioenergetics
- Helps maintain blood pressure, heart rate, muscle tone, and digestive/reproductive functions
Growth Hormone (GH)
- Secreted by anterior pituitary
- Stimulation causes tropic/nontropic effects to cause growth
Parathyroid Glands
- 4 small endocrine glands
- Embedded in the surface of the thyroid
- Secretes parathyroid hormone
Parathyroid Hormone (PTH)
- Increases level of blood Ca2+
- Causes mineralized matrix of bones to break down
- Stimulates reabsorption of Ca2+ in renal tubules of kidneys
- Promotes production of Vitamin D (indirect effect on intestines)
Calcitonin
- Inhibits bone breakdown
- Enhances Ca2+ excretion by kidneys
- Secreted by the thyroid gland
Adrenal Glands
- Located near the top of the kidneys
- Made up of the adrenal cortex (outer) and adrenal medulla (central)
- Fused endocrine and neurocrine gland
Norepinephrine
- Noradrenaline
- A catecholamine
- Secreted by the adrenal medulla
- Chemically and functionally similar to epinephrine
- Acts as a hormone or neurotransmitter
- with epinephrine, responsible for the fight/flight response
Catecholamines
Amine hormones synthesized from the amino acid tyrosine
Glucocorticoids
- Have a primary effect on glucose metabolism
- Cause breakdown of skeletal muscle proteins (when reserves run out in the liver)
- Can have an anti-inflammatory effect
Mineralocorticoids
- Have an effect on mineral metabolism
- Specifically affect water and salt balance
Androgens
- Example: testosterone
- Responsible for the development of male secondary sex characteristics
- Primarily synthesized by the testes
Testosterone
- Steroid hormone
- Required for development of the male reproductive system, spermatogenesis, and male secondary sex characteristics
- Major androgen in mammals
Estrogens
- Example: estradiol
- Maintain female reproductive system
- Develop female secondary sex characteristics
Estradiol
- Steroid hormone
- Stimulates the development and maintenance of the female reproductive system and secondary sex characteristics
- Major estrogen in mammals
Progestins
- Example: progesterone
- Prepare and maintain tissues lining the uterus for the support and development of an embryo
Progesterone
- Steroid hormone
- Prepares the uterus for pregnancy
- Major progestin in mammals
Melatonin
-Modified amino acid
-Regulates light and seasonal related functions
-Functions in:
-skin pigmentation
-biological rhytyms associated with reproduction and daily
activity
-promoting sleep
Pineal Gland
- Small mass of tissue near the brain
- Produces melatonin
Melanocyte-Stimulating Hormone (MSH)
- Secreted by anterior pituitary
- In amphibians, fish, and reptiles: it regulates pigmentation
- In mammals: functions in hunger, metabolism, and skin pigmentation
