01 endocrine

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BIOL 4345Human Physiology

Course Instructor

– Tuesdays 7:00-9:50pm– Dr. Liz Warren– Office Phone: 281-283-3770– Email: [email protected]

– Also available for help – Dr. Rick Puzdrowski– Office phone: 281-283-3750– Email: [email protected]

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Review of Course Informationon Syllabus

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How To Do Well In This Class

• READ THE BOOK BEFORE LECTURE• Take notes and ask questions during lecture• Form a study group to meet once per week and

take turns EXPLAINING material to each other• Review your notes weekly• Don’t wait for a test to study• LEARN the material, not memorize the material• Use BlackBoard for class info, updates, lecture

notes, grades, messages, etc– Call Blackboard support at 281-283-2828 for

assistance

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Let’s Begin: Chapters 6, 7, & 8

Today’s lecture will cover:• Definition of physiology• Review of organ systems• Function and process• Introduction to homeostasis• The Endocrine System• Start of Nervous System

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• Physiology: Study of the functions and processes that occur in living organisms.

• The cell is the basic unit of life:• Cell physiology describes the functions and

process that occur within cells.

Fig 1-1

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Review of Organ Systems

• We will study the physiology of 7 organ systems in the human body:– Endocrine– Nervous– Musculoskeletal– Cardiovascular– Respiratory– Renal– Gastrointestinal and Metabolism

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• Homeostasis: The maintenance of a relatively stable internal environment.– Several mechanisms work together to maintain

the internal environment within a fairly narrow range of conditions

– Example: Body temperature set point is 98.6°

98.5

Temperature sensors in hypothalamus

Temp drop ->activatemechanisms to increase temp

98.7

Temp increase ->activatemechanisms to decrease temp

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The Endocrine System and Nervous System work together to maintain homeostasis by

regulating and coordinating activities of cells and tissues.

These two systems regulate the physiologic processes in all the other organ systems.

To understand the physiology of all the other systems, you have to understand

how these two systems work!

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Endocrine System Nervous systemNature of signal Hormones: chemical

signals released into the blood

Electrical Signals and Neurotransmitters released directly on target cell

Specificity of Target Cells

Not very specific: one hormone may contact several cells

Very specific: Neurotransmitters are released directly onto a target cell

Speed of Signal Delivery to Target

Relatively Slow. Takes time for hormone to be delivered to target by blood.

Fast. Electrical signals = msec. Neurotransmitters only diffuse short distance

Duration of Effect on Target Cells

Long-lasting, from minutes to years

Short duration: usually only msecs.

Coding of signal Intensity

More hormone released = stronger signal to target cell

More nerve impulse frequency and more neurotrans = stronger signal to target cell

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Endocrine System Chapter 7

Figure 7-2

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The Endocrine System uses hormones to affect physiologic activities in target cells in

3 basic ways:

1. Control the rate of enzymatic reactions in target cells (speeding them up or slowing them down).

2. Control the transport proteins inserted into the cell membrane of target cells.

3. Turn genes on or off.

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• The time required to reduce a hormone’s plasma concentration by ½.– Used as a measure of how long a hormone is

active in the body after it has been secreted.– Longer half life = longer hormone is active.

The Half-Life of a hormone:

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Three Classes of Hormones, based on their chemical structures

1) Peptide (protein) hormones

2) Steroid Hormones

3) Amine hormones

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Peptide Hormones

• Largest class of hormones• Composed of chains of amino acids• Short half life of only a few minutes• Effects on target cells occur rapidly

– Used to regulate body functions that require rapid adjustments (ex. blood glucose levels)

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Figure 7-3, step 1

ECFCytoplasm Plasma

Capillaryendothelium

Messenger RNA on the ribosomes binds amino acids into a peptide chain called a preprohormone.The chain is directed into the ER lumen by a signal sequence of amino acids.

mRNA

Ribosome

Endoplasmic reticulum (ER)

Preprohormone

1

1

Peptide Hormone Synthesis, Packaging, and Release

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Figure 7-3, steps 1–2

ECFCytoplasm Plasma



Enzymes in the ER chop off the signal sequence, creating an inactiveprohormone.

mRNA

Ribosome

Prohormone

Signalsequence


Preprohormone

1 2

1

2


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Golgi complex

ECFCytoplasm Plasma




The prohormone passes from theER through the Golgi complex.

mRNA

Ribosome

Prohormone

Signalsequence

Transportvesicle


Preprohormone

1 2 3

1

2

3


21


4

Active hormone

Golgi complex

Secretoryvesicle

ECFCytoplasm Plasma

Peptidefragment





Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments.

mRNA

Ribosome

Prohormone

Signalsequence

Transportvesicle


Preprohormone

1 2 3

1

2

3

4


22


4 5

Active hormone

Golgi complex

Secretoryvesicle

ECFCytoplasm Plasma

Peptidefragment

Releasesignal



The secretory vesicle releases its contents by exocytosis into the extracellular space.




mRNA

Ribosome

Prohormone

Signalsequence

Transportvesicle


Preprohormone

1 2 3

1

2

3

4

5


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4 5

To target

Active hormone

Golgi complex

Secretoryvesicle

ECFCytoplasm Plasma

Peptidefragment

Releasesignal



The secretory vesicle releases its contents by exocytosis into the extracellular space.

The hormone moves into the circulation for transport to its target.




mRNA

Ribosome

Prohormone

Signalsequence

Transportvesicle


Preprohormone

1 2 3 6

1

2

3

4

5

6


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Peptide hormones are hydrophilic (water soluble “likes water”) so can be transported free in the blood, but they are lipophobic (insoluble in lipids), so cannot

enter their target cell.

Binding of the peptide hormone onto the Target cell receptor activates a Second Messenger system in the Target cell thatproduces the overall desired hormone response.

Test Yourself

• Why is homeostasis important to living organisms?

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Steroid Hormones• Derived from cholesterol

– Functional groups determine function of different steroid hormones.

– Synthesized on the smooth ER (SER)– An abundance of SER is characteristic of endocrine cells

that synthesize steroid hormones.

Functional groups

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• Steroid hormones are lipophilic (soluble in lipids, “likes cell membranes”). So, these hormones cannot be stored inside the cell or secretory vesicles.

– Endocrine cells that synthesize steroid hormones don’t start synthesizing their hormone until a signal is received.

– Hydrophobic, so they need to be attached to carriers in the blood (plasma proteins, which help protect the steroid hormone from enzymatic breakdown)

– Because protected from breakdown, long half life (remain active in blood 60-90min)

Steroid Hormones

• Can enter target cell and bind to target receptors found inside the target cell (cytoplasmic receptors) or in the nucleus (nuclear receptors).

• The steroid hormone-receptor complex activates or represses genes for protein synthesis. - (ex. Contractile proteins in muscle cells)

• A few steroid hormones (ex. Estrogen) also bind to receptors on target cell membrane and activate second messenger system in target cell.

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Steroid Hormones

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Figure 7-7, step 1

Most hydrophobic steroids are bound to plasma protein carriers. Only unbound hormones can diffuse into the target cell.

Cellmembrane

Interstitialfluid

Nucleus

Bloodvessel

Proteincarrier

1

1

Steroid Hormones: Action

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Steroid hormone receptors are typically in the cytoplasm or nucleus.

Cellmembrane

Interstitialfluid

Cytoplasmicreceptor

Nucleus

Nuclear receptor

Steroidhormone

Bloodvessel

Proteincarrier2

1

1

2

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Figure 7-7, steps 1–2a


Some steroid hormones also bind to mem-brane receptors that use second messenger systems to create rapid cellular responses.


Cellmembrane

Interstitialfluid

Cytoplasmicreceptor

Nucleus

Nuclear receptor

Rapid responses

Steroidhormone

Bloodvessel

Proteincarrier

Cell surface receptor

2

1

2a

1

2

2a

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The receptor-hormone complex binds to DNA and activates or represses one or more genes.

Cellmembrane

Interstitialfluid

Cytoplasmicreceptor

Nucleus

Nuclear receptor

DNA

Rapid responses

Steroidhormone

Bloodvessel

Proteincarrier


2

3

1

2a

1

2

2a

3

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Activated genes create new mRNA that moves into the cytoplasm.

Cellmembrane

Interstitialfluid

Cytoplasmicreceptor

Nucleus

Nuclear receptor

DNA

Rapid responses

Transcriptionproduces mRNA

Steroidhormone

Bloodvessel

Proteincarrier


2

3

1

4

2a

1

2

2a

3

4

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Translation produces new proteins for cell processes.




Activated genes create new mRNA that moves into the cytoplasm.

Cellmembrane

Interstitialfluid

Cytoplasmicreceptor

Endoplasmicreticulum

Nucleus

Nuclear receptor

DNA

Translation

Rapid responses

Transcriptionproduces mRNA

Steroidhormone

Bloodvessel

Proteincarrier

Newproteins


2

3

1

4 5

2a

1

2

2a

3

45

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• Steroid Hormones are made by:– The gonads (sex steroid hormones)– Cortex of the adrenal gland (aldosterone & cortisol &

some sex steroids)

• There is a lag time between release of the steroid and the production of an effect in the target cell (gene activation, etc. takes time!)– Therefore, steroid hormones do not generally result in

rapid responses, so are not used for regulating physiologic process requiring rapid responses.

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Amine Hormones

• Derived from one of two amino acids:– Tryptophan– Tyrosine

• Ring structure

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Adrenal Gland Medulla Thyroid Gland

Tyrosine-derived amine hormones:

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Tryptophan-derived Amine Hormones

• Melatonin– Synthesized in pineal gland from the amino

acid tryptophan– Involved in regulation of circadian rhythm

• Sleep/wake cycle

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Melatonin & Catecholamines behave like peptide hormones

• Soluble in water so can be transported freely in blood

• Bind to cell membrane receptor on target cell membrane

• Activate second messenger system in target cell

• Have short half-life

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Thyroid hormones behave like steroid hormones

• Transported bound to plasma proteins• Have nuclear receptors in target cells• Activate or repress genes, changing the

proteins that target cell is synthesizing• Have long half-life

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Hormone Action Must Be Terminated

• When the hormone has done its job to regulate body functions, its signal activity is terminated by any of the following:

1) Enzymes in plasma can degrade peptide hormones bound to cell membrane receptors

2) Receptor-hormone complex can be internalized into the cell and digested by lysosomes

3) Many intracellular enzymes can also metabolize hormones that enter the cell

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Hormones act on their target cells by _______.

a. controlling the rates of enzymatic reactions

b. controlling the transport of ions or molecules across cell membranes

c. controlling gene expression and the synthesis of proteins

d. A and C

e. A, B, and C

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Hormones act on their target cells by _______.

a. controlling the rates of enzymatic reactions

b. controlling the transport of ions or molecules across cell membranes

c. controlling gene expression and the synthesis of proteins

d. A and C

e. A, B, and C

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If a particular cell in the body does not have a receptor for a specific hormone, _________. a. this hormone will bind directly to the DNA

in this cell

b. this hormone will have no effect on this cell

c. this hormone is no longer present in the body

d. none of the cells in the body have receptors for this hormone

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If a particular cell in the body does not have a receptor for a specific hormone, _________. a. this hormone will bind directly to the DNA

in this cell

b. this hormone will have no effect on this cell

c. this hormone is no longer present in the body

d. none of the cells in the body have receptors for this hormone

a. steroid

b. amino acid-derived

c. peptide

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Which of the hormone classes is most likely to undergo post-translational modification?

a. steroid

b. amino acid-derived

c. peptide

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Which of the hormone classes is most likely to undergo post-translational modification?

a. travels only to cells with receptors for that hormone

b. travels to all cells but elicits responses only in cells with receptors for that hormone

c. must return to the endocrine cell to elicit a response

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A hormone traveling in the bloodstream _____.

a. travels only to cells with receptors for that hormone

b. travels to all cells but elicits responses only in cells with receptors for that hormone

c. must return to the endocrine cell to elicit a response

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A hormone traveling in the bloodstream _____.

Lipophilic signal molecules can bind to ______.a. cytosolic receptors

b. nuclear receptors

c. membrane receptors

d. A and B

e. A, B, and C

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Lipophilic signal molecules can bind to ______.a. cytosolic receptors

b. nuclear receptors

c. membrane receptors

d. A and B

e. A, B, and C

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Which of the following represents the correct order of the steps in a reflex control pathway?

a. stimulus → input signal → integrating center → sensor → output signal → target → response

b. stimulus → sensor → input signal → integrating center → output signal →target→ response

c. stimulus → sensor → input signal → output signal → target →integrating center → response

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Which of the following represents the correct order of the steps in a reflex control pathway?

a. stimulus → input signal → integrating center → sensor → output signal → target → response

b. stimulus → sensor → input signal → integrating center → output signal →target→ response

c. stimulus → sensor → input signal → output signal → target →integrating center → response

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01 endocrine

Documents

cell membrane of target

systems work

cell physiology

target cellslonglasting

review of organ systems

activities of cells

nervous system work

stronger signal