Physiology Exam 3 Study Guide (DRAFT)

What amino acids are amine hormones derived from?

• tyrosine and tryptophan

Examples of Amine Hormones

• epinephrine (adrenaline)

• norepinephrine (noradrenaline)

• melatonin

• T3

• T4

Peptide Hormones

• chains of amino acids

• shorter chains than protein hormones

Examples of Peptide Hormones

• insulin

• glucagon

• oxytocin

• growth hormone

• FSH

Glycoproteins

• long polypeptide chains bound to carbohydrate molecules

Examples of Glycoproteins

• FSH

• luteinizing hormone

Steroid Hormones

• lipid-based molecules derived from cholesterol

Examples of Steroid Hormones

• testosterone

• estradiol

• progesterone

• cortisol

• aldosterone

Hormone Receptors

• specific protein molecules located either on the cell surface (for water-soluble hormones) or inside the cell (for lipid-soluble hormones)

• bind to hormones with high affinity and trigger specific cellular responses

Hormone Half-Life

• the time it takes for half of the hormone in the bloodstream to be degraded or eliminated

• the half-life of hormones circulating in the blood ranges from hours to days

• most hormones are removed from the blood by the liver and converted to less active products

Hormone Concentration and Effects

• tissues typically respond to hormones only when their concentrations are within a certain physiological range

• pharmacological concentrations can lead to different effects

  • high concentrations may result in binding to receptors of related hormones

  • can result in widespread side effects

Water-Soluble Hormone Action

• water-soluble hormones bind to cell surface receptors, triggering intracellular signaling cascades involving second messengers

Water-soluble hormone examples

• peptides

• proteins

• glycoproteins

• catecholamines

Second Messengers

• cAMP, IP3, DAG,Ca2+

Lipid-Soluble Hormone Action

• lipid-soluble hormones diffuse across the plasma membrane

• bind to intracellular receptors

• directly influence gene expression

Examples of lipid-soluble hormones

• steroids

• thyroid hormones

Second Messenger Systems

• intracellular signaling molecules that amplify the hormone signal

• key examples include:

  • cAMP, IP3, DAG, Ca2+

Nuclear Hormone Receptors

• intracellular receptors that bind to lipid-soluble hormones and regulate gene transcription

• have ligand-binding and DNA-binding domains

Genomic vs. Nongenomic Actions of Steroid Hormones

• genomic actions involve changes in gene expression

• nongenomic actions involve rapid, non-transcriptional effects

Hormone Interactions: Synergistic Effects

• occur when two or more hormones work together to produce a particular effect

• additive: combined effect is greater than the sum of individual effect

  • norepinephrine and epinephrine affect the heart in the same way

• complementary: each hormone contributes a different piece of an overall outcome

  • producing milk requires estrogen, cortisol, prolactin, oxytocin

Hormone Interactions: Permissive

• one hormone is required for another to exert its full effect

  • occur when one hormone makes the target cell more responsive to a second hormone

  • exposure to estradiol makes the uterus more responsive to progesterone

  • increased secretion of PTH makes the intestines more responsive in D3 in calcium absorption

Hormone Interactions: Antagonistic

• hormone have opposing effects

• insulin and glucagon both affect adipose tissue

Hypothalamus

• a region of the brain that produces releasing and inhibiting hormones that regulate the anterior pituitary

Anterior Pituitary

• glandular epithelium (from embryonic mouth)

  • pars distalis and pars tuberalis

• produces and secretes several hormones

  • GH

  • TSH

  • ACTH

  • FSH

  • LH

  • PRL

  • POMC

Posterior Pituitary

• stores and releases oxytocin and ADH

• nervous tissue

• pars nervosa

Where are oxytocin and ADH produced?

hypothalamus

The release of oxytocin and ADH is regulated by what?

regulated by neuroendocrine reflexes

Thyroid Gland

• produces thyroid hormones (T3 and T4)

  • regulate metabolism

• produces calcitonin

  • regulates blood calcium levels

Iodine

• essential for thyroid hormone synthesis

Iodine Deficiency

• can lead to hypothyroidism and goiter

Parathyroid Glands

• produce parathyroid hormones (PTH)

  • regulates blood calcium levels

What does PTH act on?

• acts on bones, kidneys, and intestines to increase blood calcium levels

Adrenal Cortex Produces…

• produces steroid hormones

  • mineralocorticoids

  • glucocorticoids

  • androgens

Adrenal Medulla produces

• catecholamines

  • epinephrine

  • norepinephrine

The adrenal glands play a crucial role in…

• stress response, electrolyte balance, and metabolism

Pancreas

• contains islets of langerhans

  • produce insulin

  • produce glucagon

Insulin

• lowers blood glucose

Glucagon

• raises blood glucose

Insulin and Glucagon

• work antagonistically to maintain glucose homeostasis

• dysregulation of these hormones can lead to diabetes

Pineal Gland

• produces melatonin, which regulates circadian rhythms and sleep-wake cycles

What is melatonin production influenced by?

• influenced by light-dark cycles

Gonads

• produce sex hormones

  • testosterone, estradiol, progesterone

• produce gametes

  • sperm and eggs

Gonadal hormone production is regulated by what?

• gonadotropins from anterior pituitary

  • FSH and LH

Negative Feedback

• a regulatory mechanism where the final product of a hormonal pathway inhibits the secretion of hormones earlier in the pathway

Negative feedback looks maintain…

• maintain hormone levels within a narrow physiological range

• ex:

  • regulation of cortisol

  • thyroid hormones

  • sex hormones

Positive Feedback

• a regulatory mechanism where the final product of a hormonal pathway stimulates the secretion of hormones earlier in the pathway

What do positive feedback loops do?

• amplify a response

• ex: release of oxytocin during childbirth

Hypothalamic-Pituitary-Target Organ Axes

• functional units involving the hypothalamus, anterior pituitary, and a target endocrine gland

• ex:

  • hypothalamic-pituitary-adrenal (HPA) axis

  • hypothalamic-pituitary-gonadal (HPG) axis

What are hypothalamic-pituitary-target organ axis regulated by?

• complex interactions between releasing and inhibiting hormones, feedback mechanisms, and neural inputs

Hypothyroidism

• a condition characterized by low thyroid hormone levels

• symptoms:

  • weight gain

  • fatigue

  • cold intolerance

  • constipation

What causes hypothyroidism?

• iodine deficiency

• autoimmune diseases (hashimoto’s thyroiditis)

• pituitary dysfunction

Hyperthyroidism

• a condition characterized by high thyroid hormone levels

• symptoms:

  • weight loss

  • nervousness

  • heat intolerance

  • palpitations

Causes of Hyperthyroidism

• Grave’s disease (Autoimmune)

• thyroid nodules

• excessive iodine intake

Diabetes Mellitus

• metabolic disorder characterized by hyperglycemia

Type 1 Diabetes

• caused by autoimmune destruction of pancreatic beta cells

Type 2 Diabetes

• caused by insulin resistance

Diabetes Complications

• neuropathy

• retinopathy

• nephropathy

• cardiovascular diseases

Cushing’s Syndrome

• condition caused by excessive cortisol production

• symptoms

  • weight gain

  • moon face

  • buffalo hump

  • muscle weakness

Causes of Cushing’s Syndrome

• adrenal tumors

• pituitary tumors

• prolonged use of glucocorticoid medications

Addison’s Disease

• condition caused by adrenal insufficiency (low cortisol and aldosterone production)

• symptoms

  • fatigue

  • weight loss

  • low blood pressure

  • hyperpigmentation

Causes of Addison’s Disease

• autoimmune diseases

• adrenal gland destruction

Amine hormones are derived from…

• tyrosine or tryptophan

Peptide and protein hormones are…

• chains of amino acids

• peptides are shorter

Glycoprotein hormones have…

carbohydrate components

Steroid hormones are…

• lipid-derived from cholesterol

• lipophilic

T/F: Hormones bind to specific receptors with low affinity

• False

• hormones will bind to specific receptors with high affinity

Water-soluble hormones bind to ___ and trigger ___

• bind to cell surface receptors

• trigger second messenger systems

Lipid-soluble hormones diffuse…

• into cells and bing to intracellular receptors

• affect gene expression

Second Messenger Systems….

• amplify hormone signals

• cAMP, IP3, DAG, Ca2+

Nuclear hormone receptors are…

• transcription factors

Hormones can act…

• synergystically

• permissively

• antagonistically

Negative feedback maintains…

• hormone homeostasis

The hypothalamus regulates…

• the anterior pituitary

The anterior pituitary…

• produces and secretes many hormones

The posterior pituitary….

• stores and releases oxytocin and ADH

Thyroid hormones regulate ____, with calcitonin regulating ___

• metabolism

• calcium

Parathyroid hormone (PTH) increases…

• blood calcium

Adrenal cortex produces…

• corticosteroids

Adrenal Medulla produces…

• catecholamines

Insulin ____ blood glucose, glucagon ____ blood glucose

• insulin lowers blood glucose

• glucagon raises blood glucose

Melatonin regulates…

circadian rhythms

Gonads produce…

sex hormones and gametes

Hypothyroidism is characterized by…

low thyroid hormone levels

Hyperthyroidism is characterized by…

high thyroid hormone levels

DIabetes mellitus involves…

hyperglycemia

Cushing’s Syndrome results from…

excessive cortisol

Addison’s disease is caused by…

adrenal insufficiency

Synthesis of amine hormones

• involves specific enzyme modifications of the precursor amino acids

Prohormones

• larger, inactive precursor forms of many peptide and protein hormones

• require post-translational modification to become active

Carbohydrate Moieties and Glycoprotein Hormones

• carbohydrate moieties play a role in binding and hormone stability

Steroid Hormone Synthesis

• involves a series of enzymatic reactions in the mitochondria and endoplasmic reticulum

• leads to production of various steroid hormones with distinct functions

What is the rate-limiting step of steroid hormone synthesis?

• often the conversion of cholesterol to pregnenolone

Hormone receptor subtypes

• lead to diverse effects depending on the receptor isoform expressed in a given cell

• receptor density can also be up-regulated or down-regulated

Influences on Hormone half-life

• influenced by:

  • hormone metabolism in the liver and kidneys

  • binding to carrier proteins

  • receptor interactions

High hormone concentrations can lead to…

• receptor saturation, desensitization, binding to receptors for related hormones

  • causes unintended side effects

Different second messenger systems lead to…

• diverse cellular responses

  • specific signaling pathway activated depends on the hormone and receptor subtype

Hormone-receptor complex acts as…

• acts as a transcription factor

  • bind hormone response elements (HREs) on DNA

  • regulate transcription of target genes

    • this leads to changes in protein synthesis (often enzymes) and long-lasting effects

    • alter cell metabolism

Second Messenger Systems involve…

• G-proteins

• protein kinases

• other enzymes that regulate various cellular processes

• dysregulation of these pathways can lead to disease

Nuclear receptor families

• steroid receptor family

• thyroid receptor family

• many uncharacterized “orphan” receptors

• coactivators and corepressors modulate receptor activity

Net Hormone Effects

• net effect of multiple hormones on a target cell depends on the relative concentrations of each hormone and the interactions between their signaling pathways