Lecture 10 Flashcards
what do endocrine glands respond to?
-diverse stimuli
-stimuli regulating homeostasis, development, and behaviour
what commonly occurs within endocrine systems?
-feedback regulation
-coordination with the nervous system
what do hormones and signalling molecules bind to? what does this trigger?
-bind to target receptors on target cells
-triggers specific response pathways
where are an animals hormones secreted? where will they go?
-into the circulatory system (blood)
-can go to all parts of the body, but will only go to the target cell that has the hormone receptor
what type of signals are hormones?
-chemical signals
what will hormones communicate?
-regulatory messages within the body
what two systems coordinate communication throughout the body?
-endocrine system
-nervous system
what is the role of the endocrine system?
-to secrete hormones that coordinate slower but longer-acting responses
-present in everyone
what areas/systems does the endocrine system cover?
-reproduction
-development
-energy metabolism
-growth
-behaviour
what is the role of the nervous system?
-convey high-speed electrical signals along neurons through specific pathways
-unique to the individual
-signals regulate other cells (neurons, muscle cells, endocrine cells)
how do animals use chemical signals?
-to communicate in diverse ways
-endocrine signalling is one of several ways animals cells transmit information between cells
how are the ways signals are transmitted between animal cells classified?
-type of secreting cell
-route taken to reach its target cell
what are the 3 types of signalling?
-endocrine signalling
-paracrine signalling
-autocrine signalling
what is endocrine signalling? what does it maintain, mediate, and regulate?
-when hormones are secreted into extracellular fluids by endocrine cells
-get to their targets via the bloodstream
-maintains homeostasis, mediates stimuli response, and regulates growth + development
what is paracrine signalling?
-target cells are near the secreting cells
-different types of cells
-target cell is typically a muscle cell
what is autocrine signalling?
-when the target cell is also the secreting cell
-neuron is typically the cell involved
what are synapses?
-specialized junctions with the target cells
-neuron + target cell typically
what occurs in synaptic signalling? what is it typically involving?
-neurons will secrete neurotransmitters to diffuse a short distance and bind to the target cell receptors
-neuron directly to cell
-involving cognition, movement, memory, and sensation
what occurs in neuroendocrine signalling?
-specialized neurosecretory cells secrete neurohormones
-travel to target cells via the bloodstream
-‘neuron’ to bloodstream
what is an example of a common neurohormone?
-antidiuretic hormone
what are pheremones?
-chemicals released into the environment
-a way of animal species communication
what are the main functions of pheromones?
-marking trails leading to food
-defining territories
-warning of predators
-attracting potential mates
what are the 3 major classes of hormones in vertebrates?
-polypeptides (proteins + peptides)
-amines (derived from amino acids)
-steroid hormones
what is an important property for the function of the classes of hormones?
-their solubility properties
-water soluble vs lipid soluble
-correlates with the location of receptors (inside or on the surface of target cells)
what are lipid soluble hormones?
-steroid hormones
-pass easily through cell membranes
what are water soluble hormones?
-polypeptides + amines
-do not pass easily through cell membranes
what are local regulators?
-molecules that act over short distances
-reach target cells by diffusion
how are gases able to act as local signallers?
-small size + lack of charge allows them to diffuse freely
-cannot travel far b/c they are highly reactive
what is an example of gaseous local regulator?
-nitric oxide (NO)
-functions as a local regulator + neurotransmitter
-help with blood flow
what are the most familiar hormones?
-proteins encoded by genes
-insulin and growth factors
what are the key aspects of insulin?
-produced as long inactive cleaved prohormone polypeptide
-stored in beta cells
how is insulin secreted and what is it needed for?
-secreted via vesicular trafficking
-needed to reduce blood glucose levels
what do growth factors regulate?
-the cell cycle
what are amide hormones? what are examples?
-signalling factors produced from amino acids
-GABA (neuronal signalling factor) (made from glutamate)
-epinephrine (made from tyrosine)
-thyroxine (thyroid hormone) (made from tryptophan)
what is the pathway of a water soluble hormone?
-secreted by exocytosis
-travel freely in the bloodstream
-bind to cell-surface receptors
what is the pathway of a lipid soluble hormone?
-travel in the bloodstream bound to transport proteins
-diffuse through the cell membrane of target cells
-bind to receptors in the cytoplasm or nucleus
what is the pathway of the water soluble hormone epinephrine?
-released by the adrenal gland
-binds to membrane surface receptors on liver cells
-release of messenger molecules to activate enzymes is triggered
-one cell response is the activation of an enzyme to break down glycogen
-results in the release of glucose to the bloodstream
what happens when a hormone binds to its receptor?
-signal transduction pathway is initiated
-responses in the cytoskeleton, enzyme activation, or a gene expression change occurs as a result
what is the typical response for a lipid soluble hormone? what is its pathway?
-response is usually a change in gene expression
-binds to its cytosolic receptor
-hormone-receptor complex moves into the nucleus
-once in the nucleus the receptor part acts a transcription factor
-regulates the transcription of specific target genes
what causes the same hormone to have different effects on target cells?
-different receptors for the hormone
-different signal transduction pathways
what is an example of a hormone that demonstrates different effects?
-epinephrine
-increases blood flow to major skeletal muscles
-decreases blood flow to the digestive tract (part of sympathetic nervous system)
what does the thyroid hormone regulate in vertebrates? what is its role in frogs?
-regulates metabolism
-controls metamorphosis of the larva frog into the adult frog
what are endocrine glands?
-groups of endocrine cells
-ductless
-secrete hormones directly into the surrounding fluid
-ex: thyroid gland, parathyroid gland, testes, ovaries
what are exocrine glands?
-glands that have ducts to carry secreted substances onto body surfaces or into body cavities
-ex: salivary glands
what are hormones assembled into?
-regulatory pathways
what is an example of a simple hormone pathway?
-acidic stomach contents being released into the duodenum
-stimulates endocrine cells to secrete secretin
-causes target cells in the pancreas to raise the pH in the duodenum
what occurs in a simple neuroendocrine pathway?
-stimulus is received by a sensory neuron
-stimulates a neurosecretory cell to secrete a neurohormone
-neurohormone enters the bloodstream and travels to target cells
what is an example of a simple neuroendocrine pathway?
-suckling by an infant sends a stimulus that reaches the hypothalamus
-nerve impulses from the hypothalamus trigger the release of oxytocin from the posterior pituitary
-causes mammary glands to secrete more milk
-positive feedback system
what role do endocrine cells play in terms of integrating systems?
-they integrate function of the endocrine system with the function of the nervous system
what combination of hormones and their functions control the molting and development in insects?
-prothoracicotropic hormone (produced in the brain, stimulates release of ecdysteroid from prothoracic gland)
-juvenile hormone (retains larval characteristics)
-ecdysone (promotes moulting when juvenile hormone is present, promotes development of adult characteristics when juvenile hormone is absent)
what is the role of the hypothalamus?
-central role in integrating both the endocrine and nervous system
-receives info and initiates responses through endocrine signalling
what is attached to the hypothalamus?
-pituitary gland
-made up of the anterior and posterior pituitary portions
what is the role of the posterior pituitary?
-stores and secretes hormones made in the hypothalamus
-hypothalamic axons reach into the PPG will secrete neurohormones synthesized from the hypothalamus
what is the role of the anterior pituitary?
-makes and releases hormones under the regulation of the hypothalamus
what two hormones released from the posterior pituitary will act directly on non endocrine tissues?
-oxytocin (regulates milk secretion by mammary glands)
-antidiuretic hormone (ADH) (regulates physiology and behaviour)
how is hormone production controlled in the anterior pituitary?
-by the releasing + inhibiting hormones secreted from the hypothalamus
how do anterior pituitary hormones act?
-as tropic hormones
-regulate the function of other endocrine cells or glands
what anterior pituitary hormone has a role in milk production? how is it released
-prolactin
-prolactin-releaseing hormone from the hypothalamus stimulates the secretion of prolactin
what happens when thyroid hormone levels drop in the blood?
-hypothalamus secretes thyrotropin-releasing hormone
-anterior pituitary secretes thyroid stimulating hormone
-TSH stimulates the release of thyroid hormone by the thyroid gland
-negative feedback
what hormone regulates many functions in humans and other mammals?
-thyroid hormone
what is hypothyroidism?
-too little thyroid function
-lead to symptoms like weight gain, fatigue, cold intolerance
what is hyperthyroidism?
-excessive production of thyroid hormone
-lead to symptoms like high temperature, sweating, weight loss, irritability, high blood pressure
how does malnutrition affect thyroid function?
-deficiencies (ex: iodine deficiency) can create a result of hypothyroidism
-disrupts the negative feedback loop
what is growth hormone and what are its effects?
-hormone secreted by the anterior pituitary gland
-has tropic, nontropic, and diverse metabolic effects
-promotes growth directly
-stimulates growth factor production
what is caused by a lack of growth hormone? what about an excess?
-lack = dwarfism
-excess=gigantism
what ion concentration is critical in the circulatory system?
-calcium
what are the 2 hormones that will regulate the homeostasis of blood calcium?
-parathyroid hormone (released by parathyroid glands)
-calcitonin (released by thyroid gland)
how does parathyroid hormone regulate blood calcium?
-increases blood calcium levels
-releases calcium from bone and stimulates reabsorption of calcium in the kidneys
-indirectly stimulates kidney to activate vitamin D
how does vitamin D help to increase blood calcium?
-promotes intestinal uptake of calcium from food
how does calcitonin regulate blood calcium?
-decreases the level of blood calcium
-stimulates calcium deposition in bone and the secretion of calcium in the kidneys
what are the glands located within the adrenal glands?
-adrenal medulla (inner)
-adrenal cortex (outer)
what hormones are secreted by the adrenal medulla? why are they secreted?
-epinephrine (adrenaline)
-norepinephrine (noradrenaline)
-in response to involuntary stress-activated impulses from the nervous system (mediate fight or flight)
what class of compounds are the hormones epinephrine and norepinephrine apart of?
-catecholamines
what do epinephrine and norepinephrine do within the body?
-trigger the release of glucose and fatty acids into the blood
-increase oxygen delivery to body cells
-direct blood toward the heart, brain and skeletal system
-direct blood away from the skin, digestive system, and kidneys
what type of stress response is created by the adrenal medulla?
-short term
what type of stress response is created by the adrenal cortex?
-long term
what family of hormones is released by the adrenal cortex? how are they triggered?
-corticosteroids
-by a hormone cascade pathway via the hypothalamus and anterior pituitary
what 2 types of corticosteroids are produced by humans?
-glucocorticoids
-mineralocorticoids
what do glucocorticoids influence? what is an example?
-influence glucose metabolism and the immune system
-ex: cortisol
what do mineralocorticoids affect? what is an example?
-affect salt and water balance
-ex: aldosterone
what does the adrenal cortex produce in small amounts?
-steroid hormones that function as sex hormones
what organs/glands produce most of the sex hormones?
-gonads (testes + ovaries)
what are the 3 sex hormones found in both males and females?
-androgens
-estrogens
-progestins
-found in significantly different proportions for males and females
what do sex hormones affect?
-growth
-development (formation of reproductive structures)
-reproductive cycles
-sexual behaviour
which gland/organ primarily synthesizes androgens? what is an example of one?
-testes
-mainly testosterone
what are testosterones purposes?
-stimulate development and maintenance of the male reproductive system
-increase muscle + bone mass
what can testosterone be taken as a supplement for?
-muscle growth
what are estrogens purposes? what is the main kind?
-main kind = estradiol
-maintenance of the female reproductive system
-development of female secondary sex characteristics
what are progestins purposes? what is main kind?
-main kind = progesterone
-preparing + maintaining the uterus for embryo growth and development
what controls the synthesis of sex hormones?
-hormones of the anterior pituitary
what secretes melatonin? what controls the release of it?
-pineal gland, located in the brain
-light + dark cycles control the release and a group of neurons in the hypothalamus
what is the name of the group of neurons that control the release of melatonin?
-the suprachiasmatic nucleus (SCN)
what do the primary functions of melatonin relate to?
-biological rhythms associated with reproduction
-daily activity levels
