Zusammenfassung der Ressource
Chemical Control
+ Homeostasis
- Hormones
- Released by endocrine glands
- Affect specific target organs with
specific receptor proteins in membrane
- Specific because of specific tertiary structure which
means only complementary shaped hormone can
bind to (Receptors have specific binding sites
- Slow transmission speed
- Travel to all parts of body via blood
- Long lasting response
- Homeostasis =
maintaining a
constant internal
environment
regardless of
changes in
external
- Important for: Enzymes (pH and temperature so no
denature), Water potential so no osmotic problems and
allowing organisms to live in a range of environments
- Generally works via negative
feedback: Deviation from
norm -> Receptors detect ->
Effectors stimulated -> Norm
restored
- Temperature control
- Endotherms: body
temperature
independent of
environment (rely on
physiological means)
- Heat Gain Centre Stuff
- Vasoconstriction = skin
arterioles constrict +
shunt vessels dilate, so
blood goes away from
skin so less radiation
heat loss
- Piloerection = erector pili muscles
contract + hairs erect so more
insulation
- Increased metabolic
rate = adrenaline
secreted, metabolic
rate increased so
heat production
increased
- Shivering = rapid
contractions, increasing
respiration so more heat
released
- More Brown fat oxidation = tissue under skin, rapidly oxidising releases heat
- Heat Loss Centre Stuff
- Vasodilation =
Arteriole muscle
walls of skin relax
+ shunt vessels
constrict so more
heat lost by
radiation
- Decreased metabolic rate = less
adrenaline released so less heat
produced
- Sweating = vasodilation causes more blood
to sweat glands so more sweat released
- Sweat evaporates using heat
- Less brown fa is oxidised
- Ectotherms: rely on behavioural mechanisms
- Behavioural mechanisms
- Basking in the Sun to become more active
- Shifting between
Sun and shade
depending on
temperature/
retreating to
burrow
- Changing posture
- Ectotherms may also change skin
colour to absorb less heat or reduce
blood flow to areas
- Heat transfer mechanisms
- Conduction: Transferring
heat between molecules
- Convection: Transfer of heat between molecules moving in fluid
- Radiation: Heat transfer BC electromagnetic emission
- Temperature detected by skin
receptors which send impulses to
brain which initiates responses
- Hypothalimus = Controler
- Heat gain centre = generate and conserve heat
- Heat loss centre = causing heat to be lost
- Positive feedback
- Normally
happens when
a breakdown of
control
- When deviation from a
norm leads to further
deviation
- Hyperthermia = heat loss mechanisms
are overwhelmed causing elevated body
temp. Increased body temp causes
enzymes to work faster + so metabolic
rate increases. This produces more heat
so enzymes work even faster until
denature
- Normally prevented by thermoregulation
- Differs from fever BC fever is where norm is just elevated
- Hypothermia = heat gain system
overwhelmed, cold means decreased enzyme
activity and so metabolic rate slows, so less
heat is produced so enzymes slow further
from optimum. This may eventually result in
death
- Blood Glucose Concentration Control
- G Words
- Glycogenesis = making glycogen
- Glycogenolysis =
glycogen -> glucose
- Gluconeogenesis =
Making glucose
from non carbs
(amino acids)
- Pancreas: Islets
of Langehans
- Alpha cells secrete
glucagon (For low blood
sugar)
- So when low blood sugar, detected by
Islets of Langerhans which stimulate
alpha cells to produce glucagon,
which targets mainly liver cells. It
binds to specific receptor proteins on
cell membrane and increases blood
glucose levels by:
- Activating glycogenolysis enzymes
- Activating glucneogenesis enzymes
- Adrenaline is also
released which increases
blood sugar levels via
second messenger
model:
- Adrenaline binds to
receptor site, activating
membrane enzyme.
Enzyme converts ATP to
cyclic AMP, which activates
other enzymes which
convert glycogen to
glucose
- Beta cells secrete insulin
(For high blood sugar)
- So when high blood sugar, Islets
of Langerhans detects and beta
sells secrete insulin into blood,
going to liver to its target cells,
binding to specific glycoprotein
receptors Insulin then:
- Increases uptake
of glucose by cells
- Insulin inserts extra
carrier proteins into
the membrane from
cell's cytoplasm
(increasing
permeability)
- Activates glycogenesis enzymes
- Activates glucose -> fat enzymes
- Increases respiration rates of cells
- Diabetes =
Inability to control
blood glucose
levels effectively
- Type 1 = body cannot produce
insulin (Maybe due to body
destroying beta cells)
- Treated by insulin injections and monitoring blood glucose levels
- Type 2 = loss of responsiveness of target cells to insulin
- Treated by monitoring diet
- Chemical Mediators
- Secreted by cells to act
locally on themselves
and cells near them
- Inflammatory response
- Prostaglandins
- Vasodilates arterioles to increase blood flow so more phagocytes to area
- Clots blood so no infection
- Stimulate histamine production
- Histamines (Secreted
by mast cells)
- Makes capillary walls more permeable so plasma and phagocytes enter damaged tissue
- Responsible for allergic reactions
- Can be secreted
by not glands,
local response
and diffuse
quickly to target
cells