18. human and animal physiology chapter 18 the central endocrine glands

7/22/2019 18. Human and Animal Physiology Chapter 18 the Central Endocrine Glands

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Cha ter 18

The Central Endocrine Glands

Human Physiology by Lauralee Sherwood 2010 Brooks/Cole, Cengage Learning

Endocrine System

Consists of ductless endocrine glands scatteredthroughout body

Glands secrete hormones which travel throughblood to target cells

Target cells have receptors for binding with specifichormone

Regulates or directs particular function

Two hormone categories based on solubility Hydrophilic

Peptide hormones Adrenal medulla

Lipophilic

er ve rom yros ne

Adrenal cortex

reproductive

Catecholamines

ero ormones endocrine glands

Thyroid gland (Iodinated tyrosine) Thyroid hormone


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Hypothalamus

The hypothalamus lies just above the

ituitar land.

The hypothalamus produces releasing and,

anterior lobe. It also produces ADH and

oxytocine

Thyrotropin-releasing hormone (TRH)

Corticotropin-releasing hormone (CRH)

-

Control

release of

anterior

Growth hormone-releasing hormone (GHRH)

Somatostatin and dopamine.

antidiuretic hormone AHH and oc tocin.

pituitary

hormones

The pituitarys posterior lobe stores and

Chapter 18 The Central Endocrine GlandsHuman Physiology by Lauralee Sherwood 2010 Brooks/Cole, Cengage Learning

.

Pituitary glandThe pituitary gland lies just below the hypothalamus.

Vasopressin

Kidney tubules Increases H2O reabsortion

Anterior pituitary:

, ,

Stimulates thyroxine (T4) yro -s mu a ng

hormone (TSH)

Adrenocorticotro ic

yro

follicular cellsand triiodothyronine (T3)

hormones secretion

hormone (ACTH)

Growth hormone (GH)

secretion

Bone, soft tissues Direct metabolic

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Ovary,

testes

o cu ar grow ,

sperm productionOvary, Ovulation, estrogen and

Prolactin (PRL)

es es ,

Mammary

glandsMilk secretion


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Pineal gland

The pineal gland. Located in the center of the brain,

.

biological clocks, the overall level of activity, and

re roductive c cles.

Brain, anterior - Bodys biological

Melatoninpituitary,

reproductive

organs, immune

r y m w ex erna cues

- Inhibits gonadotropins

- Acts as an antioxidantsystem..etc..

- Enhances immunity


Thyroid gland

The bow-tie-shaped thyroid gland lies in front of

the trachea, ust below the lar nx. It roduces

thyroid hormones, which have roles in growth,

development, and metabolic control.

Tetraiodothyronine

- Most cell

- Increase metabolic rate

-

iodothyronine (T3) in body

- Never development

Calcitonin Bone- Decrease plasma Ca2+

concentration



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Parathyroid gland

The four parathyroid gland are located on the back

surface of the th roid land. The roduce

parathyroid hormone, which increase blood levers

of calcium ions.

Parathyroid Bone,

- Increases plasma Ca2+

concentration,

hormone (PTH) kidneys,

intestine

- Decrease plasma PO43-

concentration

- Stimulates vitamin D

activation


Parathyroid control of calcium metabolism

Parathyroid hormoneinduces living cells tosecrete enzymes that digest

enhances calciumreabsorption in the kidneys.

cells to secrete enzymesthat act on precursors ofvitamin D

Humans have four parathyroid gland on the posterior surfaceof the th roid land.

The glands secrete parathyroid hormone when the calciumlevel in the blood drops.


This hormone acts on cells in the bone and the kidney


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Thymus gland

The thymus gland produces the hormone thymosin,

which has roles in immunit

Th mosin T L m hoc tes- Enhances T lymphocyte

pro era on an unc on

There are two adrenal gland, one above

.

aldosterone. The inner medula secretes

e ine hrine and nore ine hrine.

Epinephrine

andSympathesis

- Reinforces

sympathetic nervous


norepinephine

throughout body,

regulation

Pancreatic gland

The islet cells of the pancreas produce insulin and

luca on, which act to maintain the concentration of

glucose in the blood

Insulin Most cells in- Promoter cellular uptake,

(Beta cells) bodyuse an s orage o

absorbed nutrients

-

(anpha

cells)

Most cells in

body

-

maintaining nutrient

levels in blood during

postabsorptive state

SomatostatineDigestive

system

- Inhibits digestion and

absorption nutrients

ce s - Inhibits secretion of all

pancreatic hormonesPancreatic

islet cells



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Gonads

The gonads produce sex hormones. In females,

ovaries produce estrogenes and progesterone.

In males, testes produce testosterone

- Promotes follicular

Estrogen

(Estradiol)

Female sex

organs, body as

eve opmen ,

development of

secondary sexual

characteristics,le

stimulates uterine and

breast growthem

- repares or pregnancy

Male

Testosterone

Male sex

organs,

body as a

- Stimulates sperm

production, development

of secondary sexual


whole c arac er s cs

Endocrine System

Overall functions of the endocrine system

Re ulate or anic metabolism and H O andelectrolyte balance

Induce ada tive chan es to hel bod co e with

stressful situations

development

Regulate red blood cell production

Along with autonomic nervous system, controland integrate both circulation and the digestion


an a sorp on o oo


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Endocrine System

Tropic Hormones

egu a es ormone secre on y ano er

endocrine gland

Stimulates and maintains their endocrine

target tissues

Example

yro -s mu a ng ormone

secreted from anterior pituitary

secretion by thyroid gland


thyroid gland

is influenced by:FEEBACK

. e ormone ra e o

secretion

CONTROL

2. The rate of Metabol icActivation or Conversion

Negative-

feedbackPositive-feedback

3. Transport

4. Inactivation T4 T3 (tri-iodothyronine)

5. Excretion



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Endocrine Dysfunction

Can arise from a variety of factors


Hyposecretion

Primary hyposecretion

Causes

Genetic

Chemical or toxic

Immunologic

er seaseprocesses suchas cancer

Idiopathic

Secondar h osecretion

Gland is normal but too little hormone is secreted due todeficiency of its tropic hormone



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Hypersecretion

Causes

continuously secrete excess hormone

Primary hypersecretion

Too much hormone is secreted due

to abnormality within gland

Secondary hypersecretion

xcess ve s mu a on rom ou s e e

gland causes oversecretion


Hormone can influence activity of another hormone

Permissiveness

ne ormone mus e presen n a equa e amoun sfor full exertion of another hormones effect

Occurs when actions of several hormones are

complimentary

Combined effect is greater than the sum of theirseparate effects

n agon sm Occurs when one hormone causes loss of


Reduces effectiveness of second hormone


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Pituitar Gland

Hypophysis

Small gland located in bony cavity just below

hypothalamus Thin stalk connects pituitary gland to

hypothalamus

Consists of two anatomically and functionally distinct

lobes

Posterior pituitary (neurohypophysis)

Composed of nervous tissueAnterior pituitary (adenohypophysis)

Consists of glandular epithelial tissue


Anatomy of the Pituitary Gland



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Pituitary Gland

Release of hormones from both anterior and

posterior pituitary is controlled by hypothalamus

Posterior pituitary

system

Stores and releases two small peptide hormones

Vasopressin

Conserves water during urine formation

Stimulates uterine contraction during

childbirth and milk ejection during


breast-feeding

Relationship of the Hypothalamus and Posterior Pituitary

1. The paraventricular and

supraoptic nuclei both contain

neurons that produce

vasopressin and oxytocin. The

hormone, either vasopressin or

oxytocin depending on theneuron, is synthesized in the

neuronal cell body in the

ypo a amus.

2. The hormone travels down the

axon to be stored in the neuronal

erm na s w n e pos er or

pituitary.

3. On excitation of the neuron, the

stored hormone is released from

these terminals into the systemicblood for distribution throughout


e o y.


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Pituitary Gland

Anterior Pitui tary

Secretes six different peptide hormones that it produces

Tropic hormones

Thyroid-stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)

Stimulates secretion of cortisol by adrenal cortex

Follicle-stimulating hormone (FSH)

n ema es, s mu a es grow an eve opmen o ovar an o c es;promotes secretion of estrogen by ovaries

In males, required for sperm production

Luteinizing hormone (LH)

In females, responsible for ovulation and luteinization; regulatesovarian secretion of female sex hormones

In males, stimulates testosterone secretion

Primary hormone responsible for regulating overall body growth;important in intermediary metabolism

Not a tropic hormone


ro ac n

Enhances breast development and milk production in females

Function of the anterior ituitar Pituitar

secretion of releasing or inhibiting hormones

on endocrine cells in the anterior pituitary


bloodstream.


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Function of the anterior Pituitary

1. Adrenocorticotroic hormone (ACTH)

Corticotropin acts on the adrenalg an s oca e a ove eackidney. It stimulates the releaseof adrenal steroid hormones bythe adrenal cortex.

2. Th roid-stimulatin hormone TSH

Thyrotropin acts on the thyroid

.the release of thyroid hormones.

Chapter 18 The Central Endocrine Glands



3. Follicle-stimulating

FSH acts on the gonads.

Estrogen secretionand egg maturation

spermproduction4. Luteinizing hormone (LH)

FSH acts on the gonads.

,

progesterone secretionand formation of the

,

stimulatestestosterone


sperm release


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5. Prolactin (PRL)

Prolactin acts on the mammary

glands. It stimulates and sustains

.

Somatotropin works throughoute o y y s mu a ng pro e n

systhesis and cell division. It has

profound influence over growth,spec a y o car age an one.


Function of the posterior pituitary

The cell bodies of secretor neurons in the h othalamussynthesize ADH and oxytocine.

These hormones are stored in axon endings in the posteriorp u ary.

Action potentials trigger their release into the bloodstream.



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Function of the posterior pituitary

1. Antidiuretic hormone (ADH)

ADH acts on cells in the

kidneys. It promotes water

must conserve water

. cy oc n

Ocytocin acts on the mammary glands, where

ducts

,muscle contractions.

Chapter 18 The Central Endocrine Glands


Summary of Anterior


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Inhibiting Hormones

Secretion of each anterior

pituitary hormone isstimulated or inhibited by

one or more hypothalamic

h o h siotro ic hormones


Vascular Link Between the Hypothalamus and Anterior Pituitary



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Growth depends on growth hormone but is influenced

by other factors as well

maximum growth capacity

Freedom from chronic disease and

stressful environmental conditions

-


Growth Rate

Not continuous

Factors responsible for promoting growth are not the

same throu hout rowth eriod

Fetal growth

GH plays no role in fetal development

os na a grow spur

Displayed during first two years of life

Pubertal growth spurt Occurs during adolescence



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production of somatomedins

Primary somatomedin is insulin-like growth factor (IGF-1)

Acts directly on bone and soft tissues to bring about mostgrowth-promoting actions

mu a es pro e n syn es s, ce v s on, an eng en ng

and thickening of bones

Exerts metabolic effects not related to rowth

Increases fatty acid levels in blood by enhancing

breakdown of triglyceride fat stored in adipose tissue

Increases blood glucose levels by decreasing glucoseuptake by muscles



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Growth hormone deficiency

Due to pituitary defect or hypothalamic dysfunction

Hyposecretion of GH in child is one cause of dwarfism Deficiency in adults produces relatively few symptoms

Growth hormone excess

os o en cause y umor o -pro uc ng ce s o

anterior pituitary

secretion begins

Gigantism Caused by overproduction of GH in childhood before

epiphyseal plates close

Acrome al


Occurs when GH hypersecretion occurs after adolescence

Summar

of growth


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Other hormones besides growth hormone are essential for

Thyroid hormone

Growth severely stunted in hypothyroid children

Hypersecretion does not cause excessive growth

Insulin

Hyperinsulinism often spurs excessive growth

Androgens

Play role in pubertal growth spurt, stimulate protein synthesisin many organs

Effects de end on resence of GH

Estrogens

Effects of estrogen on growth prior to bone maturation are


Tiny, pinecone-shaped structure

Located in center of brain

Secretes melatonin

Hormone of darkness Secretion falls to low levels during light of day

Helps keep bodys circadian rhythms in synchrony with light-

dark cycle

Promotes sleep

Influences reproductive activity, including onset of puberty

c s as an ox an o remove ree ra ca s

Enhances immunity



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Bodys master biological clock e - n uce cyc c var a ons n c oc pro e n

concentrations within SCN bring about cyclic

Cycle takes about a day

SCN must be set daily by external cues so bodys

levels driven by surrounding environment


rca an yt ms

Daily changes in light intensity

master clock

transmit them directly to SCN

pineal gland

18. human and animal physiology chapter 18 the central endocrine glands

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