IB 202 e4 chemical signals in animals

Hormones

-produced by endocrine glands

-released into bloodstream and act on target cells

Endocrine System

-hormones are chemical messengers in endocrine system that target cells through the bloodstream

Nervous System

-electrical impulses act as messengers in the nervous system

What Structures make up the endocrine system?

-incredible diversity in endocrine clans in human endocrine system

Exocrine glands

-deliver secretions through ducts into a space other than the circulatory system

Negative Feedback System in Hormones

-glucocorticoids perform their functions through the body and negatively affect release of further secretions

What is the negative feedback system important for hormones?

-to maintain homeostasis

Positive Feedback in Hormones

-results in more hormone being released and a greater response

What systems can follow both positive and negative feedback loops?

The hormones in the menstrual cycle

Hormones in the menstrual cycle w/ positive and negative feedback.

-negative feedback: estrogen and progesterone to the hypothalamus and pituitary gland

-positive feedback: estrogen to the hypothalamus and pituitary gland in days 12-14 to raise estrogen in ovaries and lead to ovulation

What are the 3 main chemical classes of hormones?

1) peptides/polypeptides

2) amino acid derivatives

3) steroids

What are the receptors for the 3 main chemical classes of hormone?

1) For peptides and polypeptides, receptors are not lipid soluble and bind to receptors on the surface of the target cell.

2) For receptors of amino acid derivatives, they are not lipid soluble and bind to receptors on surface of target cell.

3) For steroids, receptors are lipid soluble and bind to receptors inside the target cell.

Steroid Hormones Crossing Membranes

-steroids and thyroid hormones cross membrane easily and bind to receptors inside the cell

What are the steroid hormones?

-estrogens (female steroids), androgens (male sex steroids), progesterone, glucocorticoids (cortisol)

-derived from cholesterol

Poplypeptide Hormones Crossing Membranes

-lipid insoluble hormones so they don’t directly affect target cell bc they can’t enter cell and act directly on DNA

-binding of hormones to cell surface hormones to cell surface activate signaling pathway that triggers intracellular activity

What are some examples of polypeptide hormones?

ADH, EPO, FSH, GH, oxytocin, PRL

Amino Acid Derivative Hormones Crossing Membranes

-bind to receptors on plasma membrane and don’t interact w DNA

Thyroid Hormones as Amino Acid Derivative Hormones

Thyroid hormones triiodothyronine and thyroxine derived from amino acid tyrosine but are lipid soluble

Hypothalamic Pituitary Axis

-HPA axis forms posterior pituitary and anterior pituitary influenced by different populations of neurons in the hypothalamus (neurosecretory cells)

Neurosecretory Cells

-hypothalamic neurons that synthesize and release hormones

Posterior Pituitary

-stores hormones produced by hypothalamus and is an extension of the hypothalamus

-extension of hypothalamus

Neurosecretory cells in the Posterior Pituitary

-project from hypothalamus and produce ADH and oxytocin hormones, release into bloodstream

-ADH reabsorbs water by kidneys

-Oxytocin induces labor and releases milk in women

Anterior Pituitary

-produces hormones and controlled by hormones of the hypothalamus

Anterior Pituitary and Hypothalamus

-connected indirectly by tiny blood vessels carrying hormones to anterior pituitary

-anterior pituitary secrets hormones in response that enter bloodstream and act on target tissues/glands

T3 and T4 Thyroid Hormones

-hypothalamus-pituitary-thyroid

-amino acid derivative

-can cross the plasma membrane

-interacts with DNA to alter gene expression-regulates weight, energy levels, internal temp, and metabolism

Thyroid Hormones and Intranuclear Receptor

-binds to receptor and increases metabolic rat which increases oxygen and energy consumption

Growth Hormone

-synthesized in anterior pituitary

-polypeptide hormone

-fuels childhood growth and maintains tissues and organs through life, in later ages starts to reduce amount of growth hormone produces

Estrogen

-synthesized in ovaries

-anterior pituitary

-required for further development of female reproductive tract, menstrual cycle, and secondary sex characteristics

Testosterone

-anterior pituitary

-synthesized in testes

-regulates sex differentiation, male sex characteristics, spermatogenesis, and fertility

-development of reproductive tract and masculinization of brain and genitalia

Epinephrine (adrenaline)

-synthesized by adrenal gland

-amino acid derivative

-neurotransmitter and hormone

Epinephrine and Fight Or Flight

-fight or flight response triggered by sympathetic system when it stimulates adrenal gland to release epinephrine

Other Short Term Responses to Stress by Epinephrine

-increases free fatty acids and glucose, pulse rate, blood pressure, and O2 consumption

-directs blood away from skin and digestive system to heart, brain, and muscle

Cortisol: Long term Response to Stress, Classify

-synthesized by adrenal glands

-steroid hormone

-cortisol released into bloodstream

Primary Roles of Hormones

-ensures continued availability of glucose to use by brain during long-term stress

-synthesis of liver enzymes that make glucose

-adipose tissue and resting muscle resistant to insulin

Effects of Long Term Cortisol Release

-muscle weakness, suppressed immune system response, reduced fitness

Blood Glucose Homeostasis, feedback and hormones

-insulin and glucagon are polypeptide hormones secreted by the pancreas

-blood glucose maintained by negative feedback

Blood Glucose levels and effects

if blood glucose too high: pancreas secretes insulin which stimulates glucose to glycogen and causes blood glucose to drop

If blood glucose too low: pancreas secretes glucagon which causes liver to convert glycogen to glucose then release it to bloodstream

Insulin and glucagon

-insulin by B cells

-glucagon by A cells

-endocrine pancreas role in endocrine system

-exocrine pancreas role in digestion

ADH- Antidiuretic Hormone

-polypeptide hormone synthesized by hypothalamus, secreted by posterior pituitary

-dehydration releases ADH

ADH hormone role with water

-ADH increases permeability of kidney’s collecting duct to water and water reabsorbed from urine

Aldosterone

-synthesized by adrenal glands

-steroid hormone

Aldosterone and Electrolyte balance

-released when sodium concentrations in body fluids are low

-increased reabsorption of Na+ in distal tubules of kidney

Erythropoietin (EPO) hormone

-synthesized in kidneys

-polypeptide hormones

-EPO is crucial to maintain homeostasis system for blood O2 levels

Blood O2 levels and EPO

-when blood O2 falls, kidneys and tissues release EPO

• stimulates RBCs, more RBC= more oxygen-carrying capacity of blood

Acromegaly

-excess growth of certain parts of human body

-enlargement of hands, feet, forehead, jaw, and nose

-caused by pituitary gland producing excess growth hormone- benign tumor, pituitary adenoma

What part of the pituitary is affected by the adenoma?

the anterior pituitary

Intrauterine Position Phenomenon

-when females and males share combs, sex hormones from fetus affects the other

-when cow gives birth to male-female twins, female usually sterile

-female offspring in rodents: still reproduce but can be more aggressive

-testes of male fetuses begin producing testosterone early in development, at this stage ovaries have not produced much