quiz 1 Flashcards
5 mechanisms of intercellular activity
direct communication, paracrine communication, autocrine communication, endocrine communication, synaptic communication
direct communication
through gap junctions
chemical signals are from ions, small solutes, lipid soluble materials
limited to adjacent cells of the same type that are interconnected by connections
paracrine communication
through extracellular fluid
chemical signals from paracrine (one cell to another cell)
limited to the local area and target cells must have appropriate receptors
autocrine communication
through extracellular fluid
chemical signals from autocrines released to itself
limited to the cell that secretes the chemical signals
endocrine communication
through the blood stream
can arise from tissues and travel far
synaptic communication
across synapses
chemical signals from neurotransmitters
limited to very specific areas
similarities between nervous system and endocrine system
- rely on release of chemicals that bind to specific receptors on target cells
- share many chemical messengers; NE and E are hormones when realeased into bloodstream but actually are neurotransmitters when released across sysnapses
- regulated by negative feedback controls
- share common goal: to preserve homeostasis by coordinating and regulating actives of cells, tissues, organs, systems
hormones, paracrine, and autocrines can be divided into 3 groups based on their chemical structure. what are 3 groups
hormones: chemical mean of messaging inside bodies of all multicellular organisms
paracrine: hormones that communicate between closely related neighboring cells
autocrines: action of hormones on themselves
1) amino acid derivatives
2) peptide hormones
3) lipid derivatives
amino acid derivatives
- thyroid hormones produced by thyroid gland
- catecholamines which are compounds of epinephrine, norepinephrine, and dopamine
- trytophan derivatives, melatonin (secreted by pineal gland)
peptide hormones
- includes most hormones of the body
- hormones secreted by hypothalamus, thymus, digestive tract, pancreas, pituitary glands
- glycoproteins (polypeptides that have carbohydrate side chains) TSH LH FSH
- synthesizes as inactive hormones (pro hormones) that are then activated before or after release
lipid derivatives
-eicosanoids (carbon ring with fatty acids side chains)
they are important pacacrine factors that coordinate cellular activities in extracellular fluids (blood clotting)
examples
lukotrienes: secondary roles as hormones
prostglandins: involved in primarily coordinating local cellular activities
-steorid hormones : cholesterol base released by: -reproductive organs (androgens, estrogen, progesterone) -adrenal cortex (corticosteroids) -kidneys (calcitrol)
what happens if a target cell doesnt have the appropriate hormone receptor
the circulating hormone has no effect
hormone receptors are located where
on plasma membrane (extracellular factors) or within target cells (intracellular factors)
receptor in plasma membrane
- receptors for catecholamines (E, NE, dopamine) peptide hormones, and most eicosonoids
- these are water soluble hormones that cannot cross plasma membrane
- hormone acts as first messenger relaying message to second messenger
- second messenger then affects enzyme activity to exert the hormones effects on the cell and change cellular metabolic reactions
important second messengers
cyclic AMP (cAMP) derivative of ATP calcium ions (Ca2+)
receptor in cytoplasm or nucleus (steroids)
- steroid hormones diffuse across the lipid part of the plasma membrane and bind to intracellular receptors in cytoplasm or nucleus
- steprids affect DNA transcription rate and protein synthesis
- steroids change synthesis of enzyme and structural proteins affecting cells metabolic activity
receptor in cytoplasm or nucleus (thyroid hormones)
- thyroid hormones are primarily transported across plasma membrane by carrier mediated processes
- bind to receptors on mitochondria affecting energy production
- bind to receptors in nucleus, affecting cells metabolic activity
hypothalamus control
- contains both brain centers and endocrine tissues
- provides the highest level of control by integrating nervous and endocrine systems through 3 mechanisms
what are 3 mechanisms of hypothalamus control
1) has neurons that secrete two hormones released from posterior pituitary
- ADH and OXT
2) secretes regulatory hormones that control anterior pituitary gland endocrine cells
- transported to pituitary through hypopheaseal portal system
- has releasing hormones (stimulate hormone realize at anterior lobe of pituitary)
- has inhibiting hormones (prevent hormone release at anterior pituitary)
3) contains autonomic (sympathetic) neurons that stimulate release of hormones from adrenal medulla
another name for anterior lobe of pituitary
adenohypophysis
another name for posterior love of pituitary
neurohypophysis
how many hormones from anterior and posterior pitutitary
anterior pituitary
- 7 peptide hormones that are called tropic hormones because they turn on other endocrine glands
posterior pituitary
-2 peptide hormones
all 9 bind to membrane receptors and use cAMP as 2nd messenger
thyroid stimulating hormone (TSH)
anterior pituitary
target: thyroid gland
- triggers release of thyroid hormones
- released in response to thyrotropin releasing hormone (TRH) from hypothalalmus
- TSH and TRH decreases release when thyroid hormone levels rise (negative feedback loop)
adrenocorticotropic hormone (ACTH)
anterior pituitary
target: adrenal gland
- stimulates release of steroid hormones from adrenal cortex ( specifically those that affect glucose metabolism
- released in response to corticotropin releasing hormone (CRH) from hypothalamus
gonadtropins 2 types
- regulate gonadal (testes and ovaries) activites
- released in response to gonadatropin releasing hormone (GnRH) from hypothalamus
- FSH and LH
Follicle stimulating hormone (FSH)
anterior pituitary
- females: promotes ovarian follicle development and (in cohort with LH) stimulates secretion of estrogen
males: promotes maturation of sperm - inhibited by inhibin (peptide released by gonads)
Luteinizing hormone (LH)
anterior pituitary
- females: induces ovulation and promotes secretion of estrogens and progesterone which prepares body for pregnancy
- males: stimulates production of sex hormones (androgens), primarily testosterone
Growth hormone (GH)
anterior pituitary
target: musclloskeltal system
- stimulates cell growth and reproduction by stimulating rate of protein synthesis
- released in response to growth hormone releasing hormone (GH_RH) and growth hormone inhibiting hormone (GH_IH)
prolactin (PRL)
anterior pituitary
target: mammary glands
- works with other hormones to stimulate mammary gland development and milk production
- released in response to several prolactin releasing hormones (PRH) and inhibited by prolactin inhibiting hormone (PIH)
melanocyte stimulating hormone (MSH)
anterior pituitary
target: skin
- from pars intermedia of anterior lobe of pituitary
- stimulates melanocytes of the skin to increase meaning production
- in adults, none are produced
oxytocin (OXT)
posterior parathyroid
target: uterus
- increased release in response to childbirth, nursing, sexual arousal, sensory input (both neural and endocrine mechanisms
- stimultes contraction of smooth muscle walls of uterus and mammary gland myoepitheila cells releasing milk
what controls secretion rate
negative feedback mechanisms control the secretion rate of the hypothalamus and the pituitary gland
feedback loop of hypothalamus and pituitary gland
1) hypothalamus produces a release hormone
2) this triggers release of a hormone by the anterior lobe of the pituitary gland
3) the pituitary hormone stimulates release of a second hormone by the target organ
4) this second hormone surpasses secretion of both the hypothalamic releasing hormone and the pituitary hormone
example:
releasing hormone: TRH –> hormone 1 from pituitary: TSH –> endocrine target organ: thyroid gland –> hormone 2 from endocrine target hormone: Thyroid hormones
releasing hormone: CRH –> hormone 1 from pituitary: ACTH –> endocrine target organ: Adrenal Cortex –> hormone 2 from endocrine target organ: Glucocorticoids
thyroid gland
contains c (clear) cells that are in-between follicular cells which secrete calcitonin (aids in calcium regulation)
thyroid hormone production and storage steps
1) iodine ions from diet delivered to thyroid gland and taken up by follicular cells
2) enzymes activate iodine and attach to tyrosine portions of thyroglobin molecule
3) t4 and t3 are produced and stored in thyroglobin
4) follicle cells remove thyroglobin from follicle via endocytosis
5) enzymes brekead down thyroglobin releasing thyroid hormones into cytoplasm
6) T3 and T4 diffuse across basement membrane and enter bloodstream
7) 75% of thyroid hormones travel in blood attached to transport proteins (thyroid binding globulins)
- The thyroid gland releases triiodothyronine (T3) and thyroxine (T4). These hormones play an important role in regulation of your weight, energy levels, internal temperature, skin, hair, nail growth
effects of thyroid hormones on peripheral tissues
- increase rates of oxygen consumption and energy consumption
- increased heart rate and force of contraction; generally results in a rise of blood pressure
- increased sensitivity to sympathetic stimulation
- maintenacne of normal sensitivity of respiratory centers to changes in oxygen and carbon dioxide concentrations
- stimulation of red blood cell formation and thus enhanced oxygen delivery
- stimulation of activity in other endocrine tissues
- accelerated turnover of minerals in bone
what hormone is primary regulator of blood calico ion levels
parathyroid hormone, produced by parathyroid glands
parathyroid gland location and structure
- two pairs on posterior surface of thyroid glans
- have two cell populations
1) oxyphil cells (unknown function )
2) parathyroid (chief) cells - produce parathyroid hormone which increases calcium levels in extracellular fluid
- monitor calcium levels in blood like thyroid c cells
specific function of parathyroid hormone
-mobilizies calcium from bone by inhibiting osteoblasts (reduces deposition rate of bone) and increases osteoclasts by releasing growth factors
-enhances reabsorption of CA2+ by kidneys
-stimulates release of calcitrol by kidneys
calcitrol enhances 4th effects and increases ca2+ and PO3-4 aborsppton in intestine
function of calcium
muscle contraction, nerves, clotting