Two systems coordinate communication throughout the body: the endocrine system and the nervous syste...
This presentation is the property of its rightful owner.
Sponsored Links
1 / 88

Signals can be of many kinds light, sound, smell, touch etc. many of which are due to chemicals. PowerPoint PPT Presentation


  • 29 Views
  • Uploaded on
  • Presentation posted in: General

Two systems coordinate communication throughout the body: the endocrine system and the nervous system The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior

Download Presentation

Signals can be of many kinds light, sound, smell, touch etc. many of which are due to chemicals.

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

  • Two systems coordinate communication throughout the body: the endocrine system and the nervous system

  • The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior

  • The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

  • In multicellular animals, nerve impulses provide electric signals; hormones provide chemical signals.

  • Hormones are secreted by cells, diffuse into the extracellular fluid, and often are distributed by the circulatory system. Hormones reach all parts of the body, but only target cells are equipped to respond

  • Hormones work much more slowly than nerve impulse transmission and are not useful for controlling rapid actions.

  • Hormones coordinate longer-term developmental processes such as reproductive cycles.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Concept 45.1: Hormones and other signaling molecules bind to target receptors, triggering specific response pathways

Signals can be of many kinds light, sound, smell, touch etc. many of which are due to chemicals.

Chemical signals bind to receptor proteins on target cells

Only target cells with the appropriate receptor respond to the signal


Types of secreted signaling molecules

Types of Secreted Signaling Molecules

Secreted chemical signals include

Hormones

Local regulators

Neurotransmitters

Neurohormones

Pheromones


Local regulators

Local Regulators

Local regulators are chemical signals that travel over short distances by diffusion

Local regulators help regulate blood pressure, nervous system function, and reproduction

Local regulators are divided into two types

Paracrine signals act on cells near the secreting cell

Autocrine signals act on the secreting cell itself


Signaling by local regulators

Signaling by Local Regulators

In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells

Types of local regulators:

Cytokines and growth factors

Nitric oxide (NO)

Prostaglandins


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Long distance signaling involves the chemical being taken by circulation to the target tissues. Usually hormones are released from a special cell or organ called an endocrine cell/organ, travel through the bloodstream, and interact with the receptor or a target cell to cause a physiological response.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-2

Blood

vessel

Response

(a) Endocrine signaling

Response

(b) Paracrine signaling

Response

(c) Autocrine signaling

Synapse

Neuron

Response

(d) Synaptic signaling

Neurosecretory

cell

Blood

vessel

Response

(e) Neuroendocrine signaling


Chemical classes of hormones

Chemical Classes of Hormones

Three major classes of molecules function as hormones in vertebrates:

Polypeptides (proteins and peptides)

Amines derived from amino acids

Steroid hormones


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not

The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-3

Water-soluble

Lipid-soluble

0.8 nm

Polypeptide:

Insulin

Steroid:

Cortisol

Amine:

Epinephrine

Amine:

Thyroxine


Cellular response pathways

Cellular Response Pathways

Water and lipid soluble hormones differ in their paths through a body

Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors

Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Signaling by any of these hormones involves three key events:

Reception

Signal transduction

Response


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-5-1

Fat-soluble

hormone

Water-

soluble

hormone

Transport

protein

Signal receptor

TARGET

CELL

Signal

receptor

NUCLEUS

(a)

(b)


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-5-2

Fat-soluble

hormone

Water-

soluble

hormone

Transport

protein

Signal receptor

TARGET

CELL

OR

Signal

receptor

Cytoplasmic

response

Gene

regulation

Cytoplasmic

response

Gene

regulation

NUCLEUS

(a)

(b)


Pathway for water soluble hormones

Pathway for Water-Soluble Hormones

Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm, enzyme activation, or a change in gene expression

Animation: Water-Soluble Hormone


Multiple effects of hormones

Multiple Effects of Hormones

The same hormone may have different effects on target cells that have

Different receptors for the hormone

Different signal transduction pathways

Different proteins for carrying out the response

A hormone can also have different effects in different species


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-8-1

Same receptors but different

intracellular proteins (not shown)

Epinephrine

Epinephrine

 receptor

 receptor

Glycogen

deposits

Vessel

dilates.

Glycogen

breaks down

and glucose

is released.

(a) Liver cell

(b) Skeletal muscle

blood vessel


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-8-2

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


Hormones

Hormones

Endocrine signals (hormones) are secreted into extracellular fluids and travel via the bloodstream

Endocrine glands are ductless and secrete hormones directly into surrounding fluid

Hormones mediate responses to environmental stimuli and regulate growth, development, and reproduction

Exocrine glands have ducts and secrete substances onto body surfaces or into body cavities (for example, tear ducts)


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-10

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


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Concept 45.2: Negative feedback and antagonistic hormone pairs are common features of the endocrine system

Hormones are assembled into regulatory pathways

  • A negative feedback loop inhibits a response by reducing the initial stimulus

  • Negative feedback regulates many hormonal pathways involved in homeostasis


Coordination of endocrine and nervous systems in invertebrates

Coordination of Endocrine and Nervous Systems in Invertebrates

In insects, molting and development are controlled by a combination of hormones:

A brain hormone stimulates release of ecdysone from the prothoracic glands

Juvenile hormone promotes retention of larval characteristics

Ecdysone promotes molting (in the presence of juvenile hormone) and development (in the absence of juvenile hormone) of adult characteristics


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-13-3

Brain

Neurosecretory cells

Corpus cardiacum

PTTH

Corpus allatum

Low

JH

Prothoracic

gland

Ecdysone

Juvenile

hormone

(JH)

EARLYLARVA

LATER

LARVA

PUPA

ADULT


Coordination of endocrine and nervous systems in vertebrates

Coordination of Endocrine and Nervous Systems in Vertebrates

The hypothalamus receives information from the nervous system and initiates responses through the endocrine system

Attached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary

The pituitary gland of mammals is a link between the nervous system and many endocrine glands and plays a crucial role in the endocrine system.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-14

Cerebrum

Thalamus

Pineal

gland

Hypothalamus

Cerebellum

Pituitary

gland

Spinal cord

Hypothalamus

Posterior

pituitary

Anterior

pituitary


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

The posterior pituitary stores and secretes hormones that are made in the hypothalamus:these hormones are called neuroendocrine hormones

The anterior pituitary makes and releases hormones under regulation of the hypothalamus


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-15

Hypothalamus

Neurosecretorycells of thehypothalamus

Axon

Posterior

pituitary

Anterior

pituitary

HORMONE

Oxytocin

ADH

TARGET

Kidney tubules

Mammary glands,uterine muscles


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

ADH

  • The function of antidiuretic hormone (ADH) is to increase water conservation by the kidney.

  • If there is a high level of ADH secretion, the kidneys resorb water.

  • If there is a low level of ADH secretion, the kidneys release water in dilute urine.

  • ADH release by the posterior pituitary increases if blood pressure falls or blood becomes too salty.

  • ADH causes peripheral blood vessel constriction to help elevate blood pressure and is also called vasopressin.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Oxytocin induces uterine contractions and the release of milk

Suckling sends a message to the hypothalamus via the nervous system to release oxytocin, which further stimulates the milk glands

This is an example of positive feedback, where the stimulus leads to an even greater response


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-17

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


Tropic hormones

Tropic Hormones

A tropic hormone regulates the function of endocrine cells or glands

The four strictly tropic hormones are

Thyroid-stimulating hormone (TSH)

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Adrenocorticotropic hormone (ACTH)


Nontropic hormones

Nontropic Hormones

Nontropic hormones target nonendocrine tissues

Nontropic hormones produced by the anterior pituitary are

Prolactin (PRL)

Melanocyte-stimulating hormone (MSH)

  • Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates

  • MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals


Growth hormone

Growth Hormone

Growth hormone (GH) is secreted by the anterior pituitary gland and has tropic and nontropic actions

It promotes growth directly and has diverse metabolic effects

It stimulates production of growth factors

An excess of GH can cause gigantism, while a lack of GH can cause dwarfism


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Figure 42.6 Effects of Excess Growth Hormone


Releasing and release inhibiting neurohormones of the hypothalumus

Releasing and Release inhibiting Neurohormones of the Hypothalumus


Anterior pituitary hormones

Anterior Pituitary Hormones

Hormone production in the anterior pituitary is controlled by releasing and inhibiting hormones from 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


Hormone cascade pathways

Hormone Cascade Pathways

A hormone can stimulate the release of a series of other hormones, the last of which activates a nonendocrine target cell; this is called a hormone cascade pathway

The release of thyroid hormone results from a hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland

Hormone cascade pathways are usually regulated by negative feedback


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-18-3

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


Thyroid hormone control of metabolism and development

Thyroid Hormone: Control of Metabolism and Development

The thyroid gland consists of two lobes on the ventral surface of the trachea

It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4)

Two forms of thyroxine, T3 and T4, are made from tyrosine. T3 (triiodothyronine) has three iodine atoms. T4 has four iodine atoms.

More T4 is produced in thyroid, but it can be converted to T3 by an enzyme in the blood. T3 is the more active form of the hormone.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

  • Thyroxine has many roles in regulating metabolism.

    • It stimulates the transcription of many genes in nearly all cells in the body. These include genes for enzymes of energy pathways, transport proteins, and structural proteins.

    • It elevates metabolic rates in most cells and tissues.

    • It promotes the use of carbohydrates over fats for fuel.

    • It promotes amino acid uptake and protein synthesis and so is critical for metabolism, growth and development. Insufficient thyroxine may result in cretinism.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Hyperthyroidism, excessive secretion of thyroid hormones, causes high body temperature, weight loss, irritability, and high blood pressure

Hypothyroidism, low secretion of thyroid hormones, causes weight gain, lethargy, and intolerance to cold


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

A goiter is an enlarged thyroid gland associated with either very low (hypothyroidism) or very high (hyperthyroidism) levels of thyroxine.

Hyperthyroid goiter results when the negative feedback mechanism fails even though blood levels of thyroxine are high.

A common cause is an autoimmune disease in which an antibody to the TSH receptor is produced. This antibody binds the TSH receptor, causing the thyroid cells to release excess thyroxine. (Graves’ disease)

The thyroid remains maximally active and grows larger, causing symptoms associated with high metabolic rates.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Hypothalamus

Anterior

pituitary

TSH

Thyroid

T3

T4

+


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

  • Hypothyroid goiter results when there is insufficient thyroxine to turn off TSH production.

  • The most common cause is a deficiency of dietary iodine.

  • With high TSH levels, the thyroid gland continues to produce nonfunctional thyroxine and becomes very large.

  • The body symptoms of this condition are low metabolism, cold intolerance, and physical and mental sluggishness.


Parathyroid hormone and vitamin d control of blood calcium

Parathyroid Hormone and Vitamin D: Control of Blood Calcium

  • Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals

    • Parathyroid hormone (PTH) is released by the parathyroid glands

    • Calcitonin is released by the thyroid gland


Vertebrate endocrine systems calcium regulation

Vertebrate Endocrine Systems- Calcium regulation

  • Calcium levels in the blood must be regulated within a narrow range. Small changes in blood calcium levels have serious effects.

  • Most calcium in the body is in the bones (99%). About 1% is in the cells, and only 0.1% is in the extracellular fluids.

  • Blood calcium levels are regulated by:

    • Deposition and absorption of bone

    • Excretion of calcium by the kidneys

    • Absorption of calcium from the digestive tract


Hormonal control of calcium homeostasis in mammals

Calcitonin

Thyroid gland

releases

calcitonin.

Reduces

Ca2+ uptake

in kidneys

Stimulates

Ca2+ deposition

in bones

Blood Ca2+

level declines

to set point

STIMULUS:

Rising blood

Ca2+ level

Homeostasis:

Blood Ca2+ level

(about 10 mg/100 mL)

STIMULUS:

Falling blood

Ca2+ level

Blood Ca2+

level rises

to set point

Stimulates

Ca2+ release

from bones

Parathyroid

gland

PTH

Increases

Ca2+ uptake

in intestines

Stimulates Ca2+

uptake in kidneys

Active

vitamin D

Hormonal control of calcium homeostasis in mammals


Vertebrate endocrine systems

Vertebrate Endocrine Systems

  • Calcitonin, released by the thyroid gland, acts to lower calcium levels in the blood.

  • Bone is constantly remodeled by absorption of old bone and production of new bone.

  • Osteoclasts break down bone and release calcium.

  • Osteoblasts use circulating calcium to build new bone.

  • Calcitonin decreases osteoclast activity and stimulates the osteoblasts to take up calcium for bone growth.


Vertebrate endocrine systems1

Vertebrate Endocrine Systems

  • Blood calcium decrease triggers release of parathyroid hormone (PTH), from the parathyroid glands which are embedded in the posterior surface of the thyroid gland.

  • This in turn causes the osteoclasts to dissolve bone and release calcium.

  • Parathyroid hormone also promotes calcium resorption by the kidney to prevent loss in the urine.

  • It also promotes vitamin D activation, which stimulates the gut to absorb calcium from food.

  • Parathyroid hormone and calcitonin act antagonistically to regulate blood calcium levels.


Vertebrate endocrine systems2

Vertebrate Endocrine Systems

  • In the kidneys, vitamin D acts with PTH to decrease calcium loss in urine.

  • In bone vitamin D acts like PTH to stimulate bone turnover and the liberation of calcium

  • The overall action of vitamin D is to raise blood calcium levels, which promotes bone deposition.

  • Vitamin D also acts in a negative feedback loop to inhibit transcription of the PTH gene in the parathyroid glands.


Vertebrate endocrine systems3

Vertebrate Endocrine Systems

  • Bone minerals have both calcium and phosphate.

  • When PTH stimulates the release of calcium from bone, phosphate is also released.

  • Normal levels of calcium and phosphate in the blood are close to the concentration that could cause them to precipitate as calcium phosphate salts.

  • Calcium phosphate salts are involved in the formation of kidney stones and hardening of artery walls.

  • PTH acts on the kidneys to increase the elimination of phosphate to reduce the possibility of calcium phosphate salt precipitation.


Vertebrate endocrine systems glucose regulation

Vertebrate Endocrine Systems –Glucose Regulation

  • Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis

  • Insulin is produced in the pancreas in cell clusters called islets of Langerhans.

  • Several cell types have been identified in the islets:

    • Beta (b) cells produce and secrete insulin.

    • Alpha (a) cells produce and secrete glucagon (antagonist of insulin).

    • Delta (d) cells produce somatostatin.

  • The remainder of the pancreas acts as an exocrine gland with digestive functions.


Vertebrate endocrine systems4

Vertebrate Endocrine Systems

  • After a meal, blood glucose levels rise and stimulate the b cells to release insulin.

  • Insulin stimulates cells to use glucose and to convert it to glycogen and fat.

  • When blood glucose levels fall, the pancreas stops releasing insulin, and cells switch to using glycogen and fat for energy.

  • If blood glucose falls too low, the a cells release glucagon which stimulates the liver to convert glycogen back to glucose.


Maintenance of glucose homeostasis

Body cells

take up more

glucose.

Insulin

Beta cells of

pancreas are stimulated

to release insulin

into the blood.

Liver takes

up glucose

and stores it

as glycogen.

STIMULUS:

Rising blood glucose

level (for instance, after

eating a carbohydrate-

rich meal)

Blood glucose level

declines to set point;

stimulus for insulin

release diminishes.

Homeostasis:

Blood glucose level

(about 90 mg/100 mL)

Blood glucose level

rises to set point;

stimulus for glucagon

release diminishes.

STIMULUS:

Dropping blood glucose

level (for instance, after

skipping a meal)

Alpha cells of pancreas

are stimulated to release

glucagon into the blood.

Liver breaks

down glycogen

and releases

glucose into

blood.

Glucagon

Maintenance of glucose homeostasis


Target tissues for insulin and glucagon

Target Tissues for Insulin and Glucagon

  • Insulin reduces blood glucose levels by

    • Promoting the cellular uptake of glucose

    • Slowing glycogen breakdown in the liver

    • Promoting fat storage


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

  • Glucagon increases blood glucose levels by

    • Stimulating conversion of glycogen to glucose in the liver

    • Stimulating breakdown of fat and protein into glucose


Vertebrate endocrine systems5

Vertebrate Endocrine Systems

  • Diabetes mellitus is a disease caused by a lack of the protein hormone insulin (Type I) or a lack of insulin receptors on target cells (Type II).

  • Insulin binds to receptors on the cell membrane and allows glucose uptake.

  • Without insulin or the receptors, glucose accumulates in the blood until it is lost in urine.


Vertebrate endocrine systems6

Vertebrate Endocrine Systems

  • High glucose levels in the blood cause water to move from the cells into the blood by osmosis.

  • The kidneys then increase urine output to get rid of the fluid excess.

  • Cells not taking up glucose use fat and protein for fuel, resulting in the body’s wasting away and tissue and organ damage.


Adrenal hormones response to stress

Adrenal Hormones: Response to Stress

  • The adrenal glands are adjacent to the kidneys

  • Each adrenal gland actually consists of two glands: the adrenal medulla (inner portion) and adrenal cortex (outer portion)

  • The medulla produces epinephrine and norepinephrine.

  • The medulla develops from the nervous system and remains under its control.

  • The cortex is under hormonal control, mainly by adrenocorticotropin (ACTH) from the anterior pituitary.


Catecholamines from the adrenal medulla

Catecholamines from the Adrenal Medulla

  • The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)

  • These hormones are members of a class of compounds called catecholamines

  • They are secreted in response to stress-activated impulses from the nervous system

  • They mediate various fight-or-flight responses


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

  • Epinephrine and norepinephrine

    • 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

  • The release of epinephrine and norepinephrine occurs in response to nerve signals from the hypothalamus


Vertebrate endocrine systems7

Vertebrate Endocrine Systems

  • Epinephrine and norepinephrine are amine hormones. They bind to two types of receptors in target cells: a-adrenergic and b-adrenergic

  • Norepinephrine acts mostly on the alpha type, so drugs called beta blockers, which inactivate only b-adrenergic receptors, can be used to reduce fight-or-flight responses to epinephrine.

  • The beta blockers leave the alpha sites open to norepinephrine and its regulatory functions.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-21

Stress

Nervesignals

Hypothalamus

Spinal cord

Releasinghormone

Nervecell

Anterior pituitary

Blood vessel

ACTH

Adrenal medulla

Adrenal cortex

Adrenalgland

Kidney

(a) Short-term stress response

(b) Long-term stress response

Effects ofmineralocorticoids:

Effects ofglucocorticoids:

Effects of epinephrine and norepinephrine:

1. Glycogen broken down to glucose; increased blood glucose

1. Retention of sodium ions and water by kidneys

1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose

2. Increased blood pressure3. Increased breathing rate4. Increased metabolic rate

2. Increased blood volume and blood pressure

2. Possible suppression of immune system

5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-21b

Adrenal medulla

Adrenalgland

Kidney

(a) Short-term stress response

Effects of epinephrine and norepinephrine:

1. Glycogen broken down to glucose; increased blood glucose

2. Increased blood pressure3. Increased breathing rate4. Increased metabolic rate

5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Fig. 45-21c

Adrenal cortex

Adrenalgland

Kidney

(b) Long-term stress response

Effects ofmineralocorticoids:

Effects ofglucocorticoids:

1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose

1. Retention of sodium ions and water by kidneys

2. Possible suppression of immune system

2. Increased blood volume and blood pressure


Vertebrate endocrine systems8

Vertebrate Endocrine Systems

  • Adrenal cortex cells use cholesterol to produce three classes of steroid hormones called corticosteroids:

    • Glucocorticoids influence blood glucose concentrations and other aspects of fuel molecule metabolism.

    • Mineralocorticoids influence extracellular ionic balance.

    • Sex steroids stimulate sexual development and reproductive activity. These are secreted in only minimal amounts by the adrenal cortex.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Figure 42.11 The Corticosteroid Hormones are Built from Cholesterol


Vertebrate endocrine systems9

Vertebrate Endocrine Systems

  • The main mineralocorticoid, aldosterone, stimulates the kidney to conserve sodium and excrete potassium.

  • The main glucocorticoid, cortisol, mediates the body’s response to stress.

  • The fight-or-flight response ensures that muscles have adequate oxygen and glucose for immediate response.


Vertebrate endocrine systems10

Vertebrate Endocrine Systems

  • Shortly after a frightening stimulus, blood cortisol rises.

  • Cortisol stimulates cells that are not critical to the emergency to decrease their use of glucose.

  • It also blocks the immune system reactions, which temporarily are less critical.

  • Cortisol can therefore be used to reduce inflammation and allergy.


Vertebrate endocrine systems11

Vertebrate Endocrine Systems

  • Cortisol release is controlled by ACTH from the anterior pituitary which, in turn is controlled by adrenocorticotropin-releasing hormone from the hypothalamus.

  • The cortisol response is much slower than the epinephrine response.

  • Turning off the cortisol response is also critical to avoid the consequences of long-term stress.

  • Cortisol has negative feedback effect on brain cells that decreases the release of adrenocorticotropin-releasing hormone.


Vertebrate endocrine systems reproduction

Vertebrate Endocrine Systems- Reproduction

  • The gonads (testes and ovaries) produce steroid hormones synthesized from cholesterol.

  • Androgens are male steroids, the dominant one being testosterone.

  • Estrogens and progesterone are female steroids, the dominant estrogen being estradiol.

  • Sex steroids determine whether a fetus develops into a male or female.

  • After birth, sex steroids control maturation of sex organs and secondary sex characteristics such as breasts and facial hair.


Vertebrate endocrine systems12

Vertebrate Endocrine Systems

  • Until the seventh week of an embryo’s development, either sex may develop.

  • In mammals, the Y chromosome causes the gonads to start producing androgens in the seven-week-old embryo, and the male reproductive system develops.

  • If androgens are not released, the female reproductive system develops.

  • In birds, the opposite rules apply: male features are produced unless estrogens are present to trigger female development.


Vertebrate endocrine systems13

Vertebrate Endocrine Systems

  • Sex steroid production increases rapidly at puberty, or sexual maturation, in humans.

  • Control of sex steroids (both male and female) is under the anterior pituitary tropic hormones called luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

  • These gonadotropins are controlled by the hypothalamic gonadotropin-releasing hormone (GnRH).

  • Before puberty, the hypothalamus produces low levels of GnRH.


Vertebrate endocrine systems14

Vertebrate Endocrine Systems

  • At puberty GnRH release increases, stimulating gonadotropin production and, hence, sex steroid production.

  • In females, increased LH and FSH at puberty induce the ovaries to begin female sex hormone production to initiate sexually mature body traits.

  • In males, increased LH stimulates cells in the testes to make androgens which induce changes associated with adolescence.


Vertebrate endocrine systems15

Vertebrate Endocrine Systems

  • Synthetic androgens (anabolic steroids) can exaggerate body strength and muscle development.

  • Negative side effects in females include more masculine body features, such as shrinking the uterus and causing an irregular menstrual cycle.

  • In males, the negative side effects include shrinking of the testes, enlarged breasts, and sterility.

  • Continued use of anabolic steroids may increase risk of heart disease, some cancers, kidney damage, and personality disorders.


Melatonin and biorhythms

Melatonin and Biorhythms

  • The pineal gland, located in the brain, secretes melatonin

  • Light/dark cycles control release of melatonin

  • Primary functions of melatonin appear to relate to biological rhythms associated with reproduction


Vertebrate endocrine systems16

Vertebrate Endocrine Systems

  • Many other body organs, such as the gut and the heart, produce hormones.

  • When blood pressure stretches the heart wall, its cells release atrial natriuretic hormone.

  • This hormone increases sodium ion and water excretion by the kidney, lowering blood pressure and blood volume.


Hormone actions the role of signal transduction pathways

Hormone Actions:The Role of Signal Transduction Pathways

  • Hormones are released in very small amounts, yet they cause large and very specific responses in target organs and tissues.

  • Strength of hormone action results from signal transduction cascades that amplify the original signal.

  • Selective action is keyed to appropriate receptors of cells responding to hormones.

  • Specific receptors can also be linked to different response mechanisms, as is the case with receptors for epinephrine and norepinephrine.


Hormone actions the role of signal transduction pathways1

Hormone Actions:The Role of Signal Transduction Pathways

  • The abundance of hormone receptors can be under feedback control.

  • Continuous high levels of a hormone can decrease the number of its receptors, a process called downregulation.

  • High levels of insulin in type II diabetes mellitus result in a loss of insulin receptors.

  • Upregulation of receptors is a positive feedback mechanism and is less common than downregulation.


Figure 42 16 dose response curves quantify response to a hormone

Figure 42.16 Dose-Response Curves Quantify Response to a Hormone


Hormone actions the role of signal transduction pathways2

Hormone Actions:The Role of Signal Transduction Pathways

  • Anything that changes the responsiveness of a system to a hormone is reflected in the dose–response curve. These may include:

    • The number of receptors in the responding cells

    • Changes in signaling pathways

    • Changes in rate-limiting enzymes

    • The availability of substrates or cofactors


Hormone actions the role of signal transduction pathways3

Hormone Actions:The Role of Signal Transduction Pathways

  • Hormone responses may also vary in their time course.

  • The length of time for the concentration of a hormone to drop to one-half of the maximum is called its half-life.

  • Epinephrine’s half-life in the blood is only 1–3 minutes. Cortisol or thyroxine half-lives are on the order of days.

  • Half-life is partially determined by degradation and elimination processes.

  • Most hormones are broken down in the liver, removed from the blood by the kidney, and excreted in the urine.


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Table 45-1b


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Table 45-1c


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Table 45-1d


You should now be able to

You should now be able to:

Distinguish between the following pairs of terms: hormones and local regulators, paracrine and autocrine signals

Describe the evidence that steroid hormones have intracellular receptors, while water-soluble hormones have cell-surface receptors

Explain how the body regulates general metabolism, Glucose and Calcium homeostatis.

How does the body responds to long tern stress?

Distinguish between hypothyroid and hyperthyroid goitre


Signals can be of many kinds light sound smell touch etc many of which are due to chemicals

Explain how the hypothalamus and the pituitary glands interact and how they coordinate the endocrine system

Explain the role of tropic hormones in coordinating endocrine signaling throughout the body

List and describe the functions of hormones released by the following: anterior and posterior pituitary lobes, thyroid glands, parathyroid glands, adrenal medulla, adrenal cortex, gonads, pineal gland.

Explain how these hormones are regulated.

Explain the general mechanisms of hormone action.

Distinguish signaling by the nervous system vs. the endocrine system


  • Login