Transcript Endocrine_ppt

 Chapter
45 ~
Chemical Signals in
Animals
Objectives
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1. Outline the two ways hormones affect target organs
2. Draw and annotate both positive and negative feedback
in the regulation of homeostasis by hormones.
3. Explain the control of blood glucose concentration,
including the roles of glucagon, insulin and ά and ß cells in
the pancreatic islets.
4. Distinguish between type I and type II diabetes.
5. List the glands of the endocrine system, name the
hormones produced and state their functions.
Regulatory systems
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Hormone~ chemical signal secreted into body fluids (blood)
communicating regulatory messages with in the body.
– Produced and secreted by cells of endocrine glands.
 Transported in the bloodstream but act only at specific sites
called “Target Organs”
– Modified a.a. tyrosine (ex. Thyroxin from the thyroid gland),
peptides (ex. ADH) or steroid molecules (ex. Sex hormones)
– Help control and coordinate body activities
– Only circulate in blood for short periods and is broken down in
the liver and excreted by the kidneys.
 Long acting hormones must be secreted continuously to be
effective
Target cells~ body cells that respond to hormones
Endocrine system/glands~ hormone secreting system/glands
(ductless); exocrine glands secrete chemicals (sweat, mucus,
enzymes) through ducts
Review Homeostasis
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How do organisms respond to environmental changes?
– Regulator – an animal that is able to maintain a constant
internal environment
 Mammals & birds – can maintain a constant internal
temperature over wide range of external temperatures.
– Non-regulators – an animal that is unable to maintain a
constant internal environment
 reptiles
Mammals, regulation of body temperature, blood sugar level,
and the amounts of water and ions in blood and tissue fluid are
regulated by negative feedback.
Detectors: specialized cells in the brain or other organs
Effectors: skin, liver and kidneys
– Information past between them via nerves system or
hormones or both
Explain that homeostasis involves monitoring levels of
variables and correcting changes in levels by negative
feedback mechanisms.
(previous objective)
Input:
Change to
the system
Output:
Condition
restored
to set value
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Negative feedback is
the type of control in
which conditions
being regulated are
brought back to a set
value as soon as it is
detected that they
have deviated from
it.
Effector:
Brings about a
second change
to system
(in opposite
direction to
the input)
Detector:
Measures level
Of the variable
Control unit:
Level of operation is
set here, and
Information from
detector received and
compared with set value,
and commands to
effector dispatched
from here
Positive vs. Negative
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Determine the following:
The chlorine level of a swimming pool decreases when the chlorinator is
turned off.
– positive
An increase in blood sugar concentration increases the amount of hormones
that stores sugar as glycogen.
– negative
A decrease in calcium concentration increases the amount of the hormone that
releases calcium from the bone.
– negative
There is a decrease in water pressure when the faucet is slowly turned off
– positive
A decrease in blood sugar concentration increases the amount of the hormone
that converts glycogen to sugar
– negative
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Draw and annotate both positive and negative feedback in the
regulation of homeostasis by hormones.
Neurosecretory cells~
actual cells that secrete
hormones
Many chemicals act as
both hormones and
nerves system signals
– Ex. Epinephrine
 Fight or flight
hormone
 A neurotransmitter
in nervous system
Feedback mechanisms ~
negative and positive
Positive feedback
 What
type of feed back is “Baby suckles –
sensory cells – nerves signal the brain –
triggers a hormone release – causes milk to
secrete”
– Positive feed back
 What type of feedback maintains
homeostasis, many endocrine and nervous
mechanisms
– Negative feedback
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 Hormones
in
mollusks tell it
to release its
eggs but inhibit
anything that
would interfere
with
reproduction
 Insects molt
Local regulators: cells adjacent to or near point of secretion
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Growth factors ~
peptides and proteins for cell proliferation
Nitric oxide (NO) ~
gas; local regulator; neurotransmitter; cell destruction
(some bacteria and cancer cells); vessel dilation
Prostaglandins ~
modified fatty acids secreted by placenta and
immune system; also found in semen; can cause pain
to tell you something is wrong with your body,
something harmful is happening (aspirin or ibuprofen
inhibit prostaglandins)
– PGE – relax
– PGF - contract
Outline the two ways hormones affect target organs
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Hormones –blood stream – all cells in body
Alter the metabolic reactions only in certain cells – must have
specific receptor molecules (no receptor molecules=no effect on
cell)
Hormones impact differently depending on chemical
composition of hormone:
– 1. Steroid hormones – cross plasma membrane, causes
activation of a specific gene in nucleus.
 Trigger synthesis of particular protein (enzyme) which
brings about change
– 2. Protein, peptide or amine hormones – binds to receptor on
membrane of target cell. (remains on outside of cell).
Causes secondary messenger on inside of plasma membrane.
This causes activation of existing protein which then brings
about specific changes in metabolism
Steroid: steroid
Peptide: peptide
 Reception
of the signal molecule binds to a
specific receptor protein, which is either
built into the plasma membrane of the target
cell or located inside the target cell
Mode of Action: Chemical Signaling
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1- Plasma membrane reception (peptide hormones)
• signal-transduction pathways (neurotransmitters, growth factors, ADH, FSH, LH,
most hormones)
2- Cell nucleus reception
steroid hormones, thyroid hormones, estrogen, progesterone, testosterone, some
local regulators
Signal transduction pathway
 Chemical
signals may bind to receptors in
the plasma membranes of certain cells and
this triggers a signal transduction pathway,
consists of a series of molecular events that
initiates a response to the signal.
Same signals can bring about different
responses in different target cells.
Why is it that some body cells respond differently
to the same peptide hormones?
 A. different target cells have different genes.
 B. each cell knows how it fits into the body’s
master plan
 C. a target cell’s response is determined by the
product of a signal transduction pathway
 D. the circulatory system regulates responses to
hormones by routing the hormones to specific
targets.
 E. the hormone is chemically altered in different
ways as it travels through the circulatory system
 Answer C
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Vertebrate Endocrine System
 Hormones
can affect one tissue, a few
tissues, or most of the tissues in the body
(like sex hormones), or they may act as
tropic hormones, which have other
endocrine glands as their targets.
Vertebrate Endocrine System
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Tropic hormones ~
a hormone that has another
endocrine gland as a target
Hypothalamus~pituitary
Pituitary gland
Pineal gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Gonads (ovary, testis)
 List
the glands of the endocrine system,
name the hormones produced and state
their functions.
The hypothalamus & pituitary, I
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Releasing and inhibiting hormones
Anterior pituitary:
Growth (GH)~bones
√gigantism/dwarfism
√acromegaly
Prolactin (PRL)~mammary glands;
milk production
Follicle-stimulating (FSH) &
Luteinizing (LH)~ovaries/testes
Thyroid-stimulating (TSH)~ thyroid
Adrenocorticotropic (ACTH)~
adrenal cortex
Melanocyte-stimulating (MSH)
Endorphins~natural ‘opiates’; brain
pain receptors
The pituitary, II
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The posterior pituitary:
Oxytocin~
uterine and mammary gland
cell contraction
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Antidiuretic (ADH)~
retention of water by kidneys
The pineal, thyroid, & parathyroid
 Melatonin~ pineal gland;
biological rhythms
 Thyroid
hormones:
Calcitonin~
lowers blood calcium
Thyroxine~
metabolic processes
 Parathyroid
(PTH)~
raises blood calcium
– (tetany – several muscle
spasms)
The pancreas
 Islets
of Langerhans
 Alpha cells:
•glucagon~ raises blood glucose levels
 Beta
cells:
•insulin~ lowers blood glucose levels
 Type
I diabetes mellitus
(insulin-dependent; autoimmune
disorder)
 Type
II diabetes mellitus
(non-insulin-dependent; reduced
responsiveness in insulin targets)
The adrenal glands
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Adrenal medulla (catecholamines): •epinephrine & norepinephrine~
increase basal metabolic rate (blood glucose and pressure)
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Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise blood
glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+
The gonads
Steroid
hormones:
– precursor is cholesterol
androgens
– (testosterone)~ sperm formation; male secondary sex
characteristics; gonadotropin
estrogens
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– (estradiol)~uterine lining growth; female secondary sex
characteristics; gonadotropin
progestins
– (progesterone)~uterine lining growth
Explain the control of blood glucose concentration,
including the roles of glucagon, insulin and ά and ß
cells in the pancreatic islets.
 Normal
levels of glucose is 90mg in every
100cm3 of blood
– Ex. Extended period without food or
prolonged physical activity can fall to 70
mg
– Ex. Eating a meal heavy in carbs can
raise the glucose in the blood to 150 mg
Cont.
Maintenance important for 2 reasons
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1. respiration continuous
process in all cells, to maintain
metabolism cells need regular
supply of glucose
Most cells hold reserves in
glycogen converted to glucose
during prolonged physical
activity
Reserves quickly used up
Brain no reserves
Falls 60mg – hypoglycemia –
faint, convulsions, coma
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2. hyperglycemia – abnormally
high concentration of blood
glucose
This lowers water potential of
blood plasma, water drawn into
cells through osmosis from
tissues causes blood volume to
increase then excreted in kidney
– body is dehydrated,
circulation deprived of fluid.
Blood pressure can’t be
maintained
Cont.
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Responses to high blood glucose
levels
B cells in pancreatic islets produce
insulin
Insulin stimulates the liver and
muscle cells to absorb glucose
from the blood and convert it to
glycogen. Granules of glycogen
are stored in the cytoplasm of
these cells. Other cells are
stimulated to absorb glucose and
use it in cell respiration instead of
fat. These processes lower the
blood glucose level
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Responses to low blood glucose
levels
A cells in the pancreatic islets
produce glucagon.
Glucagon stimulates liver cells to
break glycogen down into glucose
and release the glucose into the
blood
This raises the blood glucose
level.
Glucose regulation by negative feedback
Muscle and other tissues take
glucose and converts it to
glycogen increases fatty
acids, fat and cell respiration
Islet of
Langerhans of
pancreas
Insulin secreted
by ß cells
Rise after
meal
Insulin
secretion stops
Glucagon
secretion stops
Rise in blood
glucose
Starvation,
physical
activity
Islet of
Langerhans of
pancreas
Secreted by
ά cells
Glycogen and a.a. are
converted into glucose
Glucose = a.a or
glycogen or fat
glucose
Brain cells
import glucose
as required but
do not store
glycogen
Small intestine
glucose absorption
Blood circulation
connects all organs
directly or indirectly
Liver imports
glucose when
blood level is
high; exports
glucose when
blood glucose
level is low
Pancreas contains
special cells of two
types that are
sensitive to the level
of sugar in the blood
glucose
glycogen
Most
tissues can
import or
export
glucose
Muscles can
import glucose but
do not export it
glucose
glycogen
ß cells secrete
insulin when glucose
level is high, insulin
causes lowering of
blood glucose level
ά cells secrete
glucagon
when glucose
level is low,
glucagon
causes raising
of blood
glucose level
Distinguish between type I and type II diabetes.
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Type I
‘early onset diabetes’
Below age of 20
Due to destruction of ß cells on the islet of
Langerhans by the body’s own immune
system
Symptoms
– Constant thirst
– Undiminished hunger
– Excessive urination
– Insulin injections are used to control
glucose levels
– Diet itself cannot control this
condition
Treatment
– Injection of insulin into blood stream
daily
– Regular measurement of blood
glucose level
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Type II
‘late onset diabetes’
90% of all cases of diabetes are this type
Common in people over 40 years,
overweight, increasing effect on human
societies around the world, including
young people and children in developing
countries, due to poor diet
Symptoms
– Mild – sufferers usually have
sufficient blood insulin, but insulin
receptors on cells have become
defective
– Usually after childhood
– Target cells insensitive to insulin
Treatment
– Largely by diet alone (low carb. diets)
– Insulin injections are not usually
needed
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