Title: Homeostasis
1Homeostasis
2When things work...
3Homeostasis
- homeostasis constant physiological adjustments
of the body in response to external environment
changes - also known as dynamic equilibrium
- What happens to your body when you exercise?
4Exercise and Homeostasis
- evaporation of sweat to cool off
- heart rate increases to increase blood flow (to
get O2 levels back up) - pancreas signals breaking down of biomolecules to
get energy needed to exercise
- body temperature increases
- O2 levels being used up
- increased cellular metabolism
5Homeostatic Control System
- Receptor organs that detect changes or sense
when conditions are not within normal range - Control Centre organs which process information
it receives from the receptor and send signals to
another part of the body - Effector coordinating centre sends signals to
an organ / tissue which will normalize the
original organ
6dynamic equilibrium
7Analogy
dynamic equilibrium
8Feedback Systems
- negative feedback system - buildup of the end
product of the system shuts the system off
blood pressure drops
brain
nerve pathway
blood pressure rises
heart rate increases
arteries constrict
- The response counteracts further change in the
same direction
9Feedback Systems
- positive feedback (feed-forward) system - a
change in some variable that triggers mechanisms
that amplify the change
Decrease in progesterone
Uterus (contractions)
Baby creates pressure on cervix
increased contractions
hypothalamus
Oxytocin released
10How are external signals converted to responses
in the cell?
- Cells in a multi-cellular organism communicate
via chemical messengers - Local and long-distance signaling
11Local Signaling
- Animal and plant cells
- Have cell junctions that directly connect the
cytoplasm of adjacent cells
12Specificity!
13- In other cases, animal cells
- Communicate using local regulators
14Long-distance signaling
- Both plants and animals use hormones
15How are external signals converted to responses
in the cell?
- Three stages of cell signaling
16Step 1 Reception
- The binding between signal molecule (ligand) and
receptor is highly specific - A conformational change in a receptor is often
the initial transduction of the signal - Can have intracellular and membrane receptors
17Intracellular Receptors
- Are proteins found within cytoplasmic or nucleus
- Signal molecules that bind are small or
hydrophobic - can readily cross the plasma membrane
18Membrane Receptors
- There are three main types of membrane receptors
- G-protein-linked
- Tyrosine kinases
- Ion channel
19G-protein-linked receptors
Yeast mating factors, epinephrine, many hormones
and neurotransmitters
Seven a helices
active
20Receptor Tyrosine Kinases
Important in cell growth and reproduction!
e.g. growth factor
21Ion Channel Receptors
- E.g. ligand-gated ion channels
- Region acts like a gate
- E.g. Sodium and Calcium channels important in the
nervous system
22Step 2 Transduction
- Multistep pathways
- Can amplify a signal
- Provide more opportunities for coordination and
regulation
23Signal Transduction Pathway At each step in a
pathway the signal is transduced into a different
form, commonly a conformational change in a
protein
24Second Messangers
- Are small, nonprotein, water-soluble molecules or
ions - Cyclic AMP (cAMP)
- Is made from ATP
25- Many G-proteins
- Trigger the formation of cAMP, which then acts as
a second messenger in cellular pathways
Figure 11.10
26Step 3 Response
- Each protein in a signaling pathway
- Amplifies the signal by activating multiple
copies of the next component in the pathway - In the cytoplasm
- Signaling pathways regulate a variety of cellular
activities
27- Other pathways
- Regulate genes by activating transcription
factors that turn genes on or off
28Thermoregulation
29Thermoregulation
- Process by which animals maintain an internal
temperature within a tolerable range. - Critical to survival because biochemical and
physiological processes are sensitive to changes
in temperature. - Enzymatic reactions
- Properties of membranes
30Modes of Heat Exchange
31Balancing Heat Loss and Gain
- Insulation
- Circulatory Adaptations
- Cooling by Evaporative Heat Loss
- Adjusting Metabolic Heat Production
32Insulation
- Feathers, hair or fat layers
- Reduces the flow of heat between an animal and
its environment - Lowers the energy cost of keeping warm
33- In mammals, the insulating material is associated
with the integumentary system (skin, hair and
nails)
Hair
Epidermis
Sweat pore
Muscle
Dermis
Nerve
Sweat gland
Hypodermis
Adipose tissue
Blood vessels
Oil gland
34- Most land animals and birds react to cold by
raising their fur or feathers - Traps a thicker layer of air
- Increasing its insulating power (the more still
air the better!)
35Goosebumps
- Raise hair on our body
- Inherited from our furry ancestors
- We rely more on a layer of fat just beneath the
skin
36Circulatory Adaptations
- We can alter the amount of blood (and hence heat)
flowing between the body core and the skin.
Vasodilation Muscles in superficial blood
vessels relax Increases the diameter of vessels
more blood Increases heat transfer, warming
the skin
37- Vasoconstriction
- Muscles in superficial blood vessels contract
- Smaller diameter of blood vessels less blood
- Reduces heat transfer, preventing heat loss
- Keeps blood (and heat) in interior of body where
it is needed
38Evaporative Heat Loss
- When environmental temperatures are above body
temperature we - Sweat, pant, bathe, spread saliva over body
surfaces - Heat is carried away with water molecules as they
change into a gas
39Adjusting Metabolic Heat Production
- Shivering and Moving - Heat production is
increased by muscle activity - Non-shivering Thermogenesis (NST) - Certain
hormones can cause mitochondria to increase their
metabolic activity and produce heat - Brown Fat Specialized tissue for rapid heat
production (has higher concn of mitochondria)
40What regulates our temperature?
- Hypothalamus - contains a group of nerve cells
that function as a thermostat
41Cold Response
42Heat Response
43Extreme Cold
- Why does your body allow you to get frost bite?
- Why is hypothermia such a concern?
44Classwork/Homework
- Section 7.1 Pg. 337 1-5, 7-9
- Section 7.2 Pg. 341 1-9,11