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Chapter 45. Chemical Signals in Animals. Overview: The Body’s Long-Distance Regulators. Hormones- chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body

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chapter 45

Chapter 45

Chemical Signals in Animals

overview the body s long distance regulators
Overview: The Body’s Long-Distance Regulators
  • Hormones- chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
  • Endocrine system- secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior
  • Nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells
types of secreted signaling molecules
Types of Secreted Signaling Molecules
  • Secreted chemical signals include
    • Hormones
    • Local regulators
    • Neurotransmitters
    • Neurohormones
    • Pheromones
types of secreted signaling molecules1
Types of Secreted Signaling Molecules
  • Hormones- secreted into extracellular fluids and travel via the bloodstream
  • Mediate responses to environmental stimuli and regulate growth, development, and reproduction
  • Local Regulators- chemical signals that travel over short distances by diffusion
  • Help regulate blood pressure, nervous system function, and reproduction
types of secreted signaling molecules2
Types of Secreted Signaling Molecules
  • Neurotransmitters- diffuse short distances between nerve synapses
  • Play a role in sensation, memory, cognition, and movement
  • Neurohormones- originate from neurons in the brain and diffuse through the bloodstream
  • Pheromones- chemical signals that are used to communicate with other individuals
  • Mark trails to food sources, warn of predators, and attract potential mates
three major classes of molecules function as hormones in vertebrates
Three major classes of molecules function as hormones in vertebrates:
    • Polypeptides (proteins and peptides)
    • Amines derived from amino acids
    • Steroid hormones
  • Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not
slide7

Water-soluble

Lipid-soluble

0.8 nm

Polypeptide:

Insulin

Steroid:

Cortisol

Amine:

Epinephrine

Amine:

Thyroxine

pathway for water soluble hormones
Pathway for Water-Soluble Hormones
  • Binding of a hormone to its receptor initiates a signal transduction pathway leading to
  • 1) responses in the cytoplasm
  • 2) enzyme activation
  • 3) or a change in gene expression

Animation: Water-Soluble Hormone

slide9

Epinephrine

Adenylyl

cyclase

G protein

GTP

G protein-coupled

receptor

ATP

Epinephrine- result in the release of glucose into the bloodstream

Second

messenger

cAMP

Protein

kinase A

Inhibition of

glycogen synthesis

Promotion of

glycogen breakdown

pathway for lipid soluble hormones
Pathway for Lipid-Soluble Hormones
  • The response to a lipid-soluble hormone is usually a change in gene expression

Animation: Lipid-Soluble Hormone

slide11

Hormone

(estradiol)

Estradiol

(estrogen)

receptor

Plasma

membrane

Hormone-receptor

complex

DNA

Vitellogenin

mRNA

for vitellogenin

multiple effects of hormones
Multiple Effects of Hormones
  • The same hormone may have different effects on target cells
slide13

Same receptors but different

intracellular proteins (not shown)

Different receptors

Epinephrine

Epinephrine

Epinephrine

Epinephrine

 receptor

 receptor

 receptor

 receptor

Glycogen

deposits

Vessel

dilates.

Vessel

constricts.

Glycogen

breaks down

and glucose

is released.

(a) Liver cell

(c) Intestinal blood

vessel

(b) Skeletal muscle

blood vessel

slide14

Major endocrine glands:

Hypothalamus

Pineal gland

Pituitary gland

Organs containing

endocrine cells:

Thyroid gland

Thymus

Parathyroid glands

Heart

Liver

Adrenal

glands

Stomach

Pancreas

Kidney

Testes

Small

intestine

Kidney

Ovaries

slide20

Pathway

Example

Stimulus

Low pH in

duodenum

S cells of duodenum

secrete secretin ( )

Endocrine

cell

Negative feedback

Blood

vessel

Target

cells

Pancreas

Bicarbonate release

Response

insulin and glucagon control of blood glucose
Insulin and Glucagon: Control of Blood Glucose
  • Pancreas- has endocrine cells called islets of Langerhans
    • alpha cells produce glucagon and beta cells produce insulin
  • Insulin reduces blood glucose levels by
    • Promoting the cellular uptake of glucose
    • Slowing glycogen breakdown in the liver
    • Promoting fat storage
  • Glucagon increases blood glucose levels by
    • Stimulating conversion of glycogen to glucose in the liver
    • Stimulating breakdown of fat and protein into glucose
slide22

Insulin

Beta cells of

pancreas

release insulin

into the blood.

STIMULUS:

Blood glucose level

rises.

Homeostasis:

Blood glucose level

(about 90 mg/100 mL)

slide23

Body cells

take up more

glucose.

Insulin

Beta cells of

pancreas

release insulin

into the blood.

Liver takes

up glucose

and stores it

as glycogen.

STIMULUS:

Blood glucose level

rises.

Blood glucose

level declines.

Homeostasis:

Blood glucose level

(about 90 mg/100 mL)

slide24

Homeostasis:

Blood glucose level

(about 90 mg/100 mL)

STIMULUS:

Blood glucose level

falls.

Alpha cells of pancreas

release glucagon.

Glucagon

slide25

Homeostasis:

Blood glucose level

(about 90 mg/100 mL)

STIMULUS:

Blood glucose level

falls.

Blood glucose

level rises.

Alpha cells of pancreas

release glucagon.

Liver breaks

down glycogen

and releases

glucose.

Glucagon

slide26

Body cells

take up more

glucose.

Insulin

Beta cells of

pancreas

release insulin

into the blood.

Liver takes

up glucose

and stores it

as glycogen.

STIMULUS:

Blood glucose level

rises.

Blood glucose

level declines.

Homeostasis:

Blood glucose level

(about 90 mg/100 mL)

STIMULUS:

Blood glucose level

falls.

Blood glucose

level rises.

Alpha cells of pancreas

release glucagon.

Liverbreaks

downglycogen

andreleases

glucose.

Glucagon

diabetes mellitus
Diabetes Mellitus
  • Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells
  • Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors
coordination of endocrine and nervous systems in vertebrates
Coordination of Endocrine and Nervous Systems in Vertebrates
  • Hypothalamus- receives information from the nervous system and initiates responses through the endocrine system
  • Pituitary gland- attached to the hypothalamus
slide29

Cerebrum

Thalamus

Pineal

gland

Hypothalamus

Cerebellum

Pituitary

gland

Spinal cord

Hypothalamus

Posterior

pituitary

Anterior

pituitary

posterior pituitary hormones
Posterior Pituitary Hormones

Posterior pituitary- stores and secretes hormones made in the hypothalamus

  • Oxytocininduces uterine contractions and the release of milk (pos. feedback)
  • Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys
slide31

Hypothalamus

Neurosecretorycells of thehypothalamus

Axon

Posterior

pituitary

Anterior

pituitary

HORMONE

Oxytocin

ADH

TARGET

Kidney tubules

Mammary glands,uterine muscles

slide32

Pathway

Example

Stimulus

Suckling

+

Sensoryneuron

Hypothalamus/posterior pituitary

Neurosecretorycell

Posterior pituitarysecretes oxytocin ( )

Positive feedback

Bloodvessel

Smooth muscle inbreasts

Targetcells

Response

Milk release

anterior pituitary hormones
Anterior Pituitary Hormones

Anterior pituitary makes and releases hormones under regulation of the hypothalamus.

  • For example, the production of thyrotropin releasing hormone (TRH) in the hypothalamus stimulates secretion of the thyroid stimulating hormone (TSH) from the anterior pituitary
slide34

Tropic effects only:FSHLHTSHACTH

Neurosecretory cellsof the hypothalamus

Nontropic effects only:ProlactinMSH

Nontropic and tropic effects:GH

Hypothalamicreleasing andinhibitinghormones

Portal vessels

Endocrine cells ofthe anterior pituitary

Posterior pituitary

Pituitary hormones

HORMONE

FSH and LH

TSH

ACTH

Prolactin

MSH

GH

TARGET

Testes orovaries

Thyroid

Adrenalcortex

Mammaryglands

Melanocytes

Liver, bones,other tissues

hormone cascade pathways

Example

Pathway

Hormone Cascade Pathways

Cold

Stimulus

Sensoryneuron

Hypothalamus secretesthyrotropin-releasinghormone (TRH )

Neurosecretorycell

Bloodvessel

slide36

Example

Pathway

Stimulus

Cold

+

Sensoryneuron

Hypothalamus secretesthyrotropin-releasinghormone (TRH )

Neurosecretorycell

Bloodvessel

Anterior pituitary secretes

thyroid-stimulating

hormone (TSH

or thyrotropin )

slide37

Pathway

Example

Stimulus

Cold

Sensoryneuron

Hypothalamus secretesthyrotropin-releasinghormone (TRH )

Neurosecretorycell

Bloodvessel

Anterior pituitary secretes thyroid-stimulatinghormone (TSHor thyrotropin )

Negative feedback

Thyroid gland secretes thyroid hormone (T3 and T4 )

Targetcells

Body tissues

Increased cellularmetabolism

Response

tropic hormones
Tropic Hormones
  • Tropic hormones regulate the function of endocrine cells or glands
    • Thyroid-stimulating hormone (TSH)
    • Follicle-stimulating hormone (FSH)
    • Luteinizing hormone (LH)
    • Adrenocorticotropic hormone (ACTH)
nontropic hormones
Nontropic Hormones
  • Nontropic hormones target nonendocrine tissues
    • Prolactin(PRL)- stimulates lactation in mammals
    • Melanocyte-stimulating hormone (MSH)- skin pigmentation and fat metabolism
growth hormone
Growth Hormone
  • Growth Hormone- secreted by the anterior pituitary gland, has tropic and nontropic actions
  • An excess of GH can cause gigantism, while a lack of GH can cause dwarfism
thyroid hormone control of metabolism and development
Thyroid Hormone: Control of Metabolism and Development
  • Stimulate metabolism and influence development and maturation
  • Hyperthyroidism- high body temp., weight loss, irritability, and high blood pressure
    • Graves’ disease is a form of hyperthyroidism in humans
  • Hypothyroidism- weight gain, lethargy, and intolerance to cold
  • Proper thyroid function requires dietary iodine for hormone production
parathyroid hormone and vitamin d control of blood calcium
Parathyroid Hormone and Vitamin D: Control of Blood Calcium
  • Parathyroid hormone (PTH) increases the level of blood Ca2+
    • It releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys
    • Stimulates kidneys to activate vitamin D-promotes uptake of Ca2+ from food
  • Calcitonin decreases the level of blood Ca2+
    • It stimulates Ca2+ deposition in bones and secretion by kidneys
slide43

PTH

Parathyroid gland(behind thyroid)

STIMULUS:

Falling bloodCa2+ level

Homeostasis:

Blood Ca2+ level(about 10 mg/100 mL)

slide44

Activevitamin D

Stimulates Ca2+uptake in kidneys

Increases Ca2+ uptake in intestines

PTH

Parathyroid gland(behind thyroid)

Stimulates Ca2+ release from bones

STIMULUS:

Falling bloodCa2+ level

Blood Ca2+level rises.

Homeostasis:

Blood Ca2+ level(about 10 mg/100 mL)

adrenal hormones response to stress
Adrenal Hormones: Response to Stress
  • Adrenal Medulla- Catecholamines
  • Secretes epinephrine (adrenaline) and norepinephrine(noradrenaline)
  • They mediate various fight-or-flight responses
    • Trigger the release of glucose and fatty acids into the blood
    • Increase oxygen delivery to body cells
    • Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive system, and kidneys
adrenal hormones response to stress1
Adrenal Hormones: Response to Stress
  • Adrenal Cortex- Steroid Hormones
  • Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system
  • Mineralocorticoids, such as aldosterone, affect salt and water balance
slide47

Fig. 45-21a

Stress

Nervesignals

Hypothalamus

Spinal cord

Releasinghormone

Nervecell

Anterior pituitary

Blood vessel

ACTH

Adrenal medulla

Adrenal cortex

Adrenalgland

Kidney

gonadal sex hormones testes and ovaries
Gonadal Sex Hormones (testes and ovaries)
  • All three sex hormones are found in both males and females, but in different amounts
  • Testes- synthesize androgens(ex: testosterone)- male reproductive system
    • Testosterone causes an increase in muscle and bone mass
  • Estrogens (ex: estradiol)- female reproductive system and secondary sex characteristics
  • Progestins (ex: progesterone)- preparing and maintaining the uterus
melatonin and biorhythms
Melatonin and Biorhythms
  • Pineal gland- located in the brain, secretes melatonin, controlled by light/dark cycles
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