Transcript AP Biology Ch 29

2013
 Maintaining
specific parameters of the
internal environment
 It’s important to maintain because all
parameters (pH, ion concentration, oxygen
and CO2 levels, temperature) need to stay at
an optimal steady state
Insulin is an effector, as it’s activity reduces the
amount of glucose in the blood
 Optimal concentration of glucose in the blood is
the set point.
 The actual level of glucose in the blood is the
feedback information
 Insulin is an effector signal in that when it binds
to receptors on target cells, it changes the
activity of these effectors in that they increase
their rate of glucose absorption. – This reduces
the glucose level in the blood, removing the
stimulus that caused insulin secretion by the
pancreas – this is negative feedback

 Positive
feedback
 The increase in pepsin formation leads to
more pepsin formation
 Rather than returning the system to a
setpoint, the process amplifies the
conversion of pepsinogen to pepsin.
 Negative
Feedback
 It is a drinking response to low bp
 When low bp causes sensory neurons to
provide feedback information that bp has
decreased, reflexes are activated to restore
optimal bp
 Positive
feedback
 Clumping of platelets reduces the loss of
blood from an injured vessel
 Clumped platelets at an injury site release a
chemical signal that further enhances
clumping of more platelets, helping to seal
the leak in the injured vessel and reduce the
loss of precious blood
 Temperature
equilibrates to the
increasing
environmental
temperature
 Forces the animal
to slow its
biochemical
reactions
 Internal
temperature
remains constant
due to metabolism
 Lipid
soluble – so
they can pass thru
phospholipid
membranes of cells
 Don’t dissolve well
in watery blood
plasma, so they
circulate to carrier
proteins
 Water
soluble – so
they are easily
transported in the
blood
 They can’t cross
membranes easily
(due to size) but the
receptor proteins
for these signals are
on the plasma
membranes of
target cells
 “downregulation”
reduces an organism’s
sensitivity to the hormone
 So in Type II diabetes, chronically high levels
of the hormone insulin (usually caused by
excessive carb intake) downregulate
production of insulin receptors throughout
the body
 Cells become less sensitive to the hormone
insulin
a.
b.
c.
FALSE – Hypothyroid goiter results when
there is not enough circulating thyroxine to
turn off thyroid-stimulating hormone or
TSH production
TRUE – The levels of TSH are high in people
with hypothyroid goiter because there is
not enough thyroid hormone cirulating to
turn off TSH production in the anterior
pituitary gland
TRUE – The levels of TRH are abnormally
high for the same reason as give in part b
 Ingestion
of excessive amounts of foods high
in Ca will cause calcium levels in the
bloodstream to rise
 This inhibits the secretion of parathyroid
hormone (PTH)
 Therefore the PTH levels of “Uncle” will be
low relative to a person with a more normal
diet
a.
b.
c.
d.
e.
f.
I
A
I
I
A
A
 Proteins
that bind
specifically to
antigenic sites of
molecules/cells
that are identified
by the immune
system as
“nonself”
 Specific for a
certain pathgen
 Can
bind small
peptides to cell
surfaces so that
antigens can be
recognized
 Can bind a variety
of potential
peptide targets
Similar in that they
are both types of
WBC’s that originate
in the bone marrow
 Part of the natural
immune system
 Each represents one
of the 2 major classes
of WBC’s

Different in that
phagocytes are nonspecific destroying
invading
microorganisms by
phagocytosis where
lymphocytes are
specific to one
antigen
 Phagocytes are
involved in innate and
adaptive.
Lymphocytes are only
involved in adaptive

 The
skin presents a physical barrier that
bacteria can rarely penetrate.
 Saltiness and acid on skin does not promote
bacterial growth
 Numerous bacteria and fungi that normally
reside on skin compete with pathogens for
space and nutrients
 Saliva
prevents infection by bacteria because
it contains lysozymes – enzyme that cleaves
bacterial cell walls
 If it gets into nasal passage, mucus provides
line of defense.
 If it get swallowed, peristalsis and cilia
movement helps move it to the acidic
stomach
 Stomach

– hostile environment for bacteria
Gastric juice is deadly for bacteria

HCl and proteases
 Old
people have been exposed to more
pathogens in their lifespan
 Immune systems “remember” that pathogen
 Older people thus have more antibodies
 Both
possess special membrane receptors
that bind to antigens on cell surface
 Response is different


T helper cell binding results in activation of
adaptive immune response
Cytotoxic T cell binding results in the death of
the cell carrying the antigen
 Pathogen
 Innate
immune system
 Physical
 No
– cold virus
barrier – skin
infection – pathogen does not enter bodyh
Pathogens in seawater swallowed
 Innate immune system
 First line of defense – digestive system mucus
and gastric juices
 Some pathogens are destroyed
 Some pathogens survive and invade
 Second line of defense – phagocytes, natural
killer cells, MHC, interferons, inflammation
 Rise in internal body temperature
 Pathogens destroyed
 Body temperature returns to normal

 Project
to central
nervous system
 Information coded
from them affects
what happens next
in the central
nervous system
 Project
OUT of the
central nervous
system
 Information coded
from them effect
change in the
periphery, such as
muscle contraction
or gland secretion
 Sodium
potassium pump uses the energy of
ATP hydrolysis to actively expel Na+ out of
the cell and K+ comes into the cell
 This causes the concentration of Na+ to be
higher outside the cell and the K+
concentration to be higher inside the
cytoplasm
 creates a concentration gradient for both
ions