Human Phys

Receptor or Second Messenger Problems Cause Abnormal Tissue Responsiveness

Down-regulation - Decreased number of receptors in response to abnormally high hormone levels - Target cell is attempting to diminish its responsiveness to the excess hormone - Hyperinsulinemia (Lead to Type 2 Diabetes)• Receptor and signal transduction abnormalities - Missing or nonfunctional receptors - Cells fail to respond or respond inappropriately to hormone signals

Peptide hormones• ______________ is a large, inactive precursor- ________________ is processed to smaller form but still inactive- Active hormone stored in vesicle; requires __________ to be released• Relatively short half-life: minutes (__________________ needed for long activity)• Cellular mechanism- Bind surface membrane receptors- Cell response through _______________________

Preprohormone; Prohormone; signal; continual secretion; signal transduction system

Diagnosis of Endocrine Pathologies Depend on the Complexity of the Reflex•

Primary pathology due to last endocrine gland in pathway• Secondary pathology due to pituitary gland• Tertiary pathology due to hypothalamus

7.9 anterior pituitary pathway

RH- releasing hormones IH- inhibiting hormones of the hypothalamus

Comparison of Peptide, Steroid, and Amino Acid-Derived Hormones

catecholamines are similar to peptide hormones, thyroid hormones are similar to steroid hormones.

A hormone is a __________• Hormones are secreted by ________________• Hormones are secreted into the _________• Pheromones are specialized ______________ (act on other individuals)• Growth factors act at ________ distance (autocrine or paracrine signls)• Hormones exert their effect at very ____ concentrations

chemical signal; a cell or group of cells; blood; ectohormones; short; low

figure 7.6 amine hormones

tyrosine is used to make hormones by modifying the side groups catecholamines and adding iodine to thyroid hormones

antagonistic control

uses different signals to send a parameter in opposite directions for example neurons that control heart rate

Neurohormones are secreted into the blood by neurons, give 3 examples.

(1) catecholamines made by modified neurons in the adrenal medulla (2) hypothalamic neurohormones secreted from the posterior pituitary (3) hypothalamic neurohormones that control hormone release from the anterior pituitary.

Thyroid-stimulating hormone (TSH)

- Also called thyrotropin- Controls hormone synthesis and secretion in the thyroid▪ Thyroid hormones (amines)

2 gonadotropins

- Follicle-stimulating hormone (FSH)- Leutinizing hormone (LH)- Controls hormones in the gonads (ovaries and testes) ▪ Sex hormones (steroids)

long loop negative feedback

- Peripheral endocrine gland produces hormone that suppresses secretion of anterior pituitary and hypothalamic trophic hormones - Most dominant feedback mechanism

Short-Loop Negative Feedback

- Pituitary hormone suppresses hypothalamic trophic hormone production - Secondary feedback mechanism

Simple Endocrine Reflex: Parathyroid Hormone

- low plasma calcium - parathyroid cell - parathyroid hormone - blood for transport - bone and kidney - increased bone absorption, increased kidney resorption of calcium, production of calcitriol leads to increased intestinal absorption of calcium - increased plasma calcium concentration

Organization of the Nervous System

1. action potential reaches presynaptic terminal 2. depolarization of presynaptic terminal opens ion channels letting Ca2+ 3. Ca2+ triggers release of neurotransmitter from vesicles 4. neurotransmitter binds to receptor sites on postsynaptic membrane 5. opening and closing of channels cause change in postsynaptic membrane potential 6. Action potential propagates through next cell 7. Neurotransmitter is inactivated or transported back into presynaptic terminal.

Adrenocorticotrophic hormone (ACTH)

Also called adrenocorticotropin- Controls hormone synthesis and secretion in the adrenal cortex▪ cortisol (steroid)

- Competitive inhibitors

Antagonism may result when two molecules compete for the same receptor

prolactin

Controls milk production (lactation) in the female breast- Has a hypothalamic release-inhibiting hormone (Dopamine)

Hypercortisolism

Cushing's syndrome

peptide hormone synthesis

DNA --> mRNA on ribosomes--> preprohormone made and directed to ER lumen by signal sequence of aas --> enzymes chop off signal sequence making inactive prohormone--> prohormone is moved into golgi complex--> secretory vesicles w/ enzymes & prohormone bud off golgi--> enzymes chop prohormone into active peptides/fragments --> exocytosis release hormones, they go to blood and reach target

AP is structurally? Epithelial origin, thus true endocrine gland Trophic hormones stimulate secretion of other hormones, list 6 AP makes ▪ Prolactin (PRL),▪ thyrotropin (TSH), ▪ adrenocorticotropin (ACTH), ▪ growth hormone (GH), ▪ follicle-stimulating hormone (FSH), ▪ and luteinizing hormone (LH)- AP is Regulated by hypothalamic hormones like: ▪ Somatostatin (SS) = growth hormone-inhibiting hormone

Epithelial origin, thus true endocrine gland ▪ Prolactin (PRL), ▪ thyrotropin (TSH), ▪ adrenocorticotropin (ACTH), ▪ growth hormone (GH), ▪ follicle-stimulating hormone (FSH), ▪ and luteinizing hormone (LH) Like Somatostatin (SS) = growth hormone-inhibiting hormone

growth hormone

Growth hormone (GH)- Also called somatotropin- Affects metabolism- Stimulates hormone production in the liver- Has a hypothalamic release-inhibiting hormone (Somatostatin, or GHIH)

name the hypothalamic hormones

IH- dopamine (PH), Somastatin (SS)/(GHIH) RH- thyrotropin-releasing hormone (TRH), corticotropin-releasing hormone (CRH), GHRH(dominant), gonadotropin-releasing hormone (GnRH)

what are the three parts of response loops and describe them?

Input: stimulus/sensor receptor w/ threshold/input signal or afferent pathway Integration: integrating center compares with setpoint(for endocrine pathways the sensor too) Output: Output Signal or Efferent pathway/ target or effector/ response

Ulta-short-loop negative feedback

Occurs in hypothalamus and pituitary - Autocrine or paracrine signals to regulate secretion

tonic control

Regulates physiological parameters in an up-down fashion. The signal is always present but changes in intensity.

Fast axonal transport - Moves organelles at rates of up to 400 mm/day - Anterograde transport: from cell body to axon terminal - Retrograde transport: from axon terminal to cell body

Slow axonal transport - Moves material by axoplasmic (cytoplasmic) flow at 0.2-2.5 mm/day.

multiple pathways for insulin secretion

Stimulation of pancreatic release of insulin: 1) High Blood Glucose levels 2) Stretch receptors of the GI --> Neural stimulation 3) GLP-1 released by GI chemoreceptors for glucose

Feedback loops in the hypothalamic pituitary pathway

The hormone, not the response, is the feedback signal

in a reflex pathway the output signal is replaced by what in endocrine and neuroendocrine reflexes? The endocrine cell is what part in simple endocrine reflexes?

a hormone or neurohormone it is the sensor

a permissive hormone does what? give an example

a permissive hormone allows another hormone to exert its full effect thyroid hormone allows reproductive hormones make normal development of reproductive systems

what is a receptor? what are sensory receptors classified into?

a receptor may mean a protein that binds to a ligand or a specialized cell or structure for transduction of stimuli into electrical signals. Sensory Receptors are classified as central or peripheral depending on if they are found inside/close to or outside the brain.

(A), (P), (S)

a- acid derived p- peptide s- steroid

to which of the 3 classes of hormones (peptide, amino-acid derived, and steroid) do thyroid (thyroxine and triiodothyronine) hormones belong? If a person's diet is low in iodine what would happen to thyroxine production?

amino-acid derived person would be unable to make thyroid hormones

peripheral receptors can be found...

away from brain, chemoreceptors (pH, gases, chemicals), osmoreceptor (osmolarity), thermoreceptor (temperature), baroreceptor (pressure), proprioceptor (body position), other (pain, vibration, touch)

Hormones act by

binding to receptors

negative feedback from exogenous hormone

both endogenous and exogenous cortisol would cause a negative feedback signal exogenous cortisol causes the glands to shut off and atrophy over time due to non use

steroid hormones are derived from made from what organs: synthesis and release: half life: bind: cellular mechanism:

cholesterol made in the adrenal cortex of adrenal glands/gonads made as needed long half life: 1-2 hours receptors inside cell stimulate genomic effects, receptors outside cell stimulate nongenomic responses

A Portal System Connects the Hypothalamus and Anterior Pituitary• Portal system is: ??? - Hypothalamic neurons produce trophic hormones - Released into 1st capillary bed in portal system to anterior pituitary - Anterior pituitary endocrine cells produce trophic hormones - Released into 2nd capillary bed in portal system to target tissues• Ensures that small amount of concentrated hormone is directed to its target

consists of two sets of capillaries connected in series by a vein, named Hypothalamic-hypophyseal (pituitary) portal system

Hyposecretion does?

diminishes or eliminates a hormones effect - Deficient hormone - Caused by decreased synthesis materials or atrophy - Absence of negative feedback leads to overproduction of trophic hormones

Hypersecretion does?

exaggerates a hormones effect - Excess hormone - Often caused by tumors or exogenous (physician administered) treatment - Negative feedback may lead to atrophy of gland

central receptors can be found...

eyes, ears, nose, tongue, chemoreceptors, osmoreceptors, thermoreceptors

simple reflexes are mediated the nervous system and the the endocrine system t/f

false they are regulating by either one not both However complex ones are mediated by both

Insulin is an example of a hormone with varied effects. - In muscle and adipose tissues, _________________________________________. - In the liver, it __________________________________. - In the brain and certain other tissues, _________________________________________________. Its action must be terminated/ start and stop.

insulin alters glucose transport proteins and enzymes for glucose metabolism modulates enzyme activity but has no direct effect on glucose transport proteins. glucose metabolism is totally independent of insulin.

complex nuero-endocrine reflex steps:

internal or external change-> receptor -> input signal: sensory neuron-> nervous system integrating center-> efferent neuron or neurohormone-> endocrine integrating center -> output signal #2 hormone -> target -> response

simple neural reflex steps:

internal/external change-> receptor-> input signal: sensory neuron-> nervous system integrating center-> efferent neuron-> target-> response

simple endocrine reflex steps:

internal/external change->endocrine system sensor-integrating center-> output signal: hormone-> target-> response

comparison of neural endocrine and neuroendocrine reflexes

know the picture

Half-Life indicates

length of activity. hormones in the bloodstream are broken down into inactive metabolites by enzymes mainly in the liver and kidneys

some hormones are derived from single amino acid like

melatonin from the pineal gland is from tryptophan catecholamines (single) and thyroid hormones (double) from tyrosine

in synergism the effect of interacting hormones is ________ than additive

more

neural vs endocrine pathways which one is more specific? what are their natures? speed? coding for stimulus intensity?

neural is more specific, faster, is electrical and chemical in nature and increases frequency for stimulus intensity endocrine is slower, less specific, only chemical in nature and increases hormone amount for stimulus intensity, also last longer neuroendocrine takes on both characteristics

The changes triggered by peptide hormones include

opening or closing membrane channels and modulating metabolic enzymes or transport proteins.

steps to identify an endocrine gland and the hormone they produce are:

remove the suspected gland: hormone deficiency replace the hormone: hormone replacement therapy create hormone excess: hormone excess

Hormones

responsible for long term/ongoing functions: metabolism, homeostasis, reproduction, growth, development Act in rates of enzymatic reactions, transport of ions or molecules across cell membranes, and gene expression and protein synthesis

The response of cells to peptide hormones is usually rapid because

second messenger systems modify existing proteins.

Liver

secretes Angiotensinogen (P), Insulin-like growth factors (P) targets adrenal cortex/ blood vessels/ other main effects: aldosterone secretion/ increases blood pressure/ growth

adrenal cortex

secretes aldosterone (S), Cortisol (S), Androgens (S) targets kidney/other main effects: Na+ and K+ homeostasis, stress response, sex drive in females

Testes (G)

secretes androgens, inhibin targets anterior pituitary/ other main effects: sperm production, secondary sex characteristics, inhibits FSH secretion

heart (C)

secretes atrial natriuretic peptide (P) targets kidneys main effects: increases Na+ excretion

adrenal medulla (N)

secretes epinephrine and norepinephrine (A) targets many tissues main effect: fight-or-flight response

kidney (C)

secretes erythropoietin (P), 1,25 Dihydroxy-vitamin D3 (calciferol) (S) targets bone marrow/intestine main effects: red blood cell production, increases calcium absorption.

placenta (C)

secretes estrogen (S), chorionic somatomammotropin (P), chorionic gonadotropin (P) targets: corpus lutem/other main effects: fetal/maternal development/metabolism/hormone secretion

ovaries (G)

secretes estrogen, progesterone (S), inhibin (P), relaxin (pregnancy) (P) targets hypothalamus/other main effects: egg production, secondary sex characteristics, inhibits FSH secretion, relaxes muscle

stomach and small intestine (C)

secretes gastrin, cholecystokinin, secretin, others (P) targets GI tract and pancreas main effects: assist digestion and absorption of nutrients

Pancreas (G)

secretes insulin, glucagon, somatostatin, pancreatic polypeptide (P) targets many tissues metabolism of glucose/nutrients

adipose tissue (C)

secretes leptin, adiponectin, resistin (P) targets hypothalamus/other main effects: food intake, metabolism, reproduction

pineal gland

secretes melatonin, targets brain/other, main effects: circadian rhythm, immune function, antioxidant

posterior pituitary gland (N)

secretes oxytocin (P), vasopressin (ADH) (P) targets breast/uterus/kidney main effects: milk ejection, labor/delivery, behavior, water reabsorption

parathyroid gland

secretes parathyroid hormone (P) targets bone/kidney main effects: regulates Ca+ and phosphate levels

thymus gland

secretes thymosin, thymopoietin (P) targets lymphocytes main effects: lymphocyte development

thyroid gland

secretes triiodothyronine and thyroxine(A), calcitonin (P) targets bone/other main effects: metabolism, growth, development, plasma Ca+ levels

hypothalamus

secretes trophic hormones (P, A) targets anterior pituitary main effects: phosphorylates proteins, alters channel opening

Skin (C)

secretes vitamin D3 (S) targets intermediate form of hormone main effects: precursor of 1,25-dihydroxycholecalciferol (vitamin D3)

types of neurons

sensory neurons, motor neurons, interneurons

figure 7.5A steroid hormones cholesterol

since steroids are lipophilic they aren't stored in the endocrine cell, thus made on demand.

FIgure 7.5B

so steroid hormones mainly act on intracellular receptors (mainly have genomic effects). Steroids are usually bound to plasma protein carriers, they need to pop off to go inside the cell to find receptors in cytoplasm or nucleus. they can also bind to membrane receptors w/ second messenger systems for rapid response

what are the reflex steps in order?

stimulus->sensor->input signal->integrating center->output signal->target->response---> feedback loop to stimulus

endocrinology

study of hormones

the pituitary gland anatomy

surrounded by sphenoid bone

Antagonistic hormones have______ the two types are?

they have opposing effects - Competitive inhibitors and Fuctional Antagonists

Functional antagonists

they have opposing physiological actions. ▪ For example, both glucagon and growth hormone raise the concentration of glucose in the blood, and both are antagonistic to insulin, which lowers the concentration of glucose in the blood. - Hormones with antagonistic actions do not necessarily compete for the same receptor.

long distance pathways maintain homeostasis t/f

true

When hypothalamus is stimulated, posterior pituitary secretes two neurohormones? PP is structurally: PP Stores hormones produced in?

vasopressin (antidiuretic hormone ADH), oxytocin neural tissue the hypothalamus