Lecture 8 regulatory mechanisms part 1

Lecture 8. Regulatory Mechanisms

I. Intercellular Communication and the Endocrine System

II. Nervous Coordination

• Endocrine signaling: secreted molecules diffuse into the bloodstream and trigger responses in target cells anywhere in the body

Intercellular Communication

Intercellular Communication

• Paracrine signaling: secreted molecules diffuse locally and trigger a response in neighboring cells

Intercellular Communication

• Autocrine signaling: secreted molecules diffuse locally and trigger a response in the cells that secrete them

• Synaptic signaling: neurotransmitters diffuse across synapses and trigger responses in cells of target tissues

Intercellular Communication

Intercellular Communication

• Neuroendocrine signaling: neurohormones diffuse into the bloodstream and trigger responses anywhere in the body

• Growth factors: proteins and polypeptides that stimulate cell proliferation

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Signaling Molecules: Local Regulators

• Cytokines: play a role in immune responses

• Nitric oxide (NO)– acts as a neurotransmitter when secreted by

neurons– kills bacteria and cancer cells when secreted by

WBCs– dilates the walls of blood vessels when secreted by

endothelial cells

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Signaling Molecules: Local Regulators

• Prostaglandins (PGs)– modified fatty acids– when secreted by the placenta stimulate uterine

contractions during childbirth– promote fever and inflammation and intensify the

sensation of pain

Signaling Molecules: Local Regulators

– secreted by neurons at many synapses– diffuse a very short distance– bind receptors on target cells

Signaling Molecules: Neurotransmitters

– secreted by neurosecretory cells– diffuse from nerve cell endings into the

bloodstream– ADH (vasopressin)

Signaling Molecules: Neurohormones

– released into the external environment– to mark trails leading to food– for defining territories– warning of predators– attracting potential mates

Signaling Molecules: Pheromones

– chemicals that transfer information and instructions between cells in animals and plants

– body’s chemical messengers– regulate growth and development– control the function of various tissues– support reproductive functions– regulate metabolism

Signaling Molecules: Hormones

Hypothalamus • integrates endocrine and nervous function

• hormones produced by neurosecretory cells of the hypothalamus:

• Releasing hormones stimulate the anterior pituitary (adenohypophysis) to secrete hormones• Inhibiting hormones prevent the anterior

pituitary from secreting hormones

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Posterior Pituitary Gland

Anterior Pituitary Gland

regulate other endocrine glands

Pituitary Gigantism•A syndrome that results when GH is secreted in excess even before puberty

Acromegaly•A syndrome that results when the pituitary gland produces excess growth hormone (GH) after epiphyseal plate closure at puberty•Affects the face and extremities

Hypopituitary dwarfism•Decreased bodily growth due to hormonal problems. The end result is a proportionate little person, because the height and growth of all other structures of the individual are decreased

Simple Goiter•Enlargement of the thyroid gland caused by the deficiency of iodine in the diet•Iodine is a major component of thyroid hormones•Thyrotropic hormone (TSH) from anterior pituitary regulates synthesis and secretion of thyroid hormones•During iodine deficiency, TSH overstiumulates the thyroid gland to extract iodine from the blood, causing the gland to enlarge

Cretinism•Caused by a malfunction of the thyroid gland at an early age.•Mentally retarded dwarf•Severe stunted physical and mental growth due to untreated congenital deficiency of thyroid hormone (congenital hypothyroidism) due to maternal nutritional iodine deficiency

Cushing Syndrome•Caused by high levels of cortisol in the blood•Symptoms include rapid weight gain, particularly of the trunk and face while sparing the limbs, growth of fat pads along the collar bone and on the back of the neck (buffalo hump), and a round face (moon face)

Melatonin Production•“Hormone of darkness” – production by pineal gland is inhibited by light and promoted by darkness•Blue light (460 – 480 nnm) particularly inhibits melatonin•melatonin signal forms part of the system that regulates the sleep-wake cycle by chemically causing drowsiness and lowering the body temperature

Melatonin Production

• A lack of PTH causes hypoparathyoidism, a tetany– calcium levels in the blood drop– convulsive contractions of the skeletal

muscles

• The pancreas has both endocrine and exocrine functions– Exocrine function: secretion of bicarbonate ions and

digestive enzymes– Endocrine function: insulin and glucagon secreted by

islets of Langerhans

• Hypoinsulinism: diabetes mellitus– hereditary factors and obesity play a role

in its development– high blood sugar levels – sugar excreted

in the urine– symptoms: excessive urination and

excessive thirst– if severe: fat substitutes for glucose as

major fuel source production of acidic metabolites life threatening lowering of blood pH

• Type I diabetes mellitus (insulin-dependent diabetes)– autoimmune disorder– usually appears in childhood– treatment: insulin injections

• Type II diabetes mellitus (non-insulin-dependent diabetes)–usually due to target cells having a decreased

responsiveness to insulin–usually occurs after age 40 – risk increases

with age–accounts for over 90% of diabetes cases–can lead to renal failure, erectile dysfunction,

blindness, slow healing wounds (including surgical incisions), and arterial disease–Treated with lifestyle modification and taking

in biguanide metformin

• Epinephrine (adrenaline) and norepinephrine (noradrenaline).

• catecholamines• secretion regulated by the nervous system in

response to stress• raises blood glucose level and blood fatty acid level• increase metabolic activities

– increases heart rate and stroke volume and dilates bronchioles

• shunts blood away from skin, digestive organs, and kidneys, and increases blood flow to heart, brain, and skeletal muscle

– Adrenal cortex reacts to stress• secretion of corticosteroids is regulated by the

nervous system in response to stress

• Glucocorticoids– raises blood glucose level– secretion regulated by ACTH (negative feedback)– abnormally high doses are administered as medication

to suppress the inflammation response

• Mineralocorticoids (example: aldosterone, which affects salt and water balance).– promotes reabsorption of Na+ and excretion of K+ in

kidneys– secretion regulated by K+ in blood

– A third group of corticosteriods are sex hormones• androgens secreted by the adrenal cortex

may account for the female sex drive• the adrenal cortex also secretes small

amounts of estrogens and progesterone

• Testes– Androgens (e.g., testosterone)• supports sperm formation• promote development and maintenance of

male sex characteristics• secretion regulated by FSH and LH

• Ovaries– Estrogens (e.g., estradiol)• stimulate uterine lining growth• promote development and maintenance of

female sex characteristics• secretion regulated by FSH and LH

– Progestins (e.g., progesterone) • promotes uterine lining growth• secretion regulated by FSH and LH

Endocrine Regulation in Insects