Transport in animals Flashcards
Module 2
What is the difference in surface area to volume ration in small and large organisms
Small organisms have a Large SA to Vol ratio
Large organisms have a small SA to Vol ratio
Why do large organisms need a specialised system
More metabolically active
Distance is too great for the molecules to travel
Diffusion is too slow
O2 and nutrients would all be used up in the first layers
What are the types of circulatory systems
Open
Closed
Double
Single
Partially double
What is an Open circulatory system
Found in Invertebrates/Insects
No/very few blood vessels
Gas exchange takes place in the tracheal system - has haemolymph
Haemolymph flow cannot be adjusted
Why do mammals need more energy than reptiles
mammals are endotherms and so will need more energy to maintain the homeostasis of temperature
What is a Closed circulatory system
In vertebrates
Has blood vessels
Blood flow can be adjusted
Haemoglobin
What is a Double circulatory system
In birds + mammals
Most efficient
Has two separate circulations
- heart to lungs
- heart to rest of the body
High pressure + blood flow can be maintained
What is a Single circulatory system
Found in fish
Blood passes through two sets of capillaries before it returns to the heart
Slower as high pressure is not maintained
Provides less energy
What is a partial double circulatory system
In amphibians and some reptiles
One circuit goes to lungs then tissues, another straight to tissues
Not efficient as deoxygenated and oxygenated blood mixed
this means some RBCs that go to tissues are empty
What are the different components + their functions in blood vessels
Elastin fibres - stretch and recoil so provide flexibility
smooth muscle - change size of lumen
collagen fibres - provides structural support
Features of arteries
Maintain pressure
- elastin fibres stretch and recoil
Withstand pressure
- Thick walls
- lots of collagen and folded endothelium
What are arterioles
link arteries and capillaries
more smooth muscle that can contract to reduce blood flow
less elastin than arteries
What is vasoconstriction
When the smooth muscle in the arteriole contracts, it constricts the vessel and prevents blood flowing into the capillary
What are capillaries
Microscopic blood vessels that link arterioles with the venules
They form an extensive network throughout the body
What are the parts of the capillary
Capillary wall and lumen
What is special about the capillary walls
They have large gaps between endothelial cells where substances can pass through
- The exception is capillaries in CNS
How are capillaries adapted for their role
Provides large S.A for diffusion
Cross section of capillaries>cross section of arterioles - slow blood flow
Single Cell thick
Features of Veins
Have valves
Have a larger lumen
has skeletal muscle pump
What happens at the venule end of the capillary
Lowered
Why is the left ventricle thicker
Needs more pressure to be able to pump blood all around the body
What is the heart muscle tissue called
Cardiac muscle/myocardium tissue
What is the definition of myogenic
When a muscle can contract or relax without nervous stimulation
What is the process of the cardiac cycle
During Diastole:
- 4 chambers relax
- blood flows in from veins (70% in ventricles)
Atrial systole starts:
- L + R atrium contract
- Increase in blood pressure causes the remaining 30% of blood to move to the ventricles
- AV valves close
Ventricular systole starts:
- Ventricular contraction starts at apex
- blood pushed up
- SL valves opens and blood enters arteries
What is the process of the control of the cardiac cycle
SAN produces wave of excitation, atrial walls contract
Non conducting tissue delays wave from passing to ventricles
AVN picks up wave
Wave passes down the septum in purkyne fibres and causes ventricles to contract
Ventricular contraction starts at apex
