Transport In Animals Flashcards
Why do larger organisms require specialised mass transport systems?
Increased transport distances
- exchange sites tend to be far away from other cells - large transport distance means diffusion not efficient as a transport system
Smaller SA:V ratio
- less SA For absorption of nutrients/gases
- more volume = longer diff distance to cells/tissues
Therefore, diffusion not efficient
Higher metabolic rate
- more demand for O2/nutrients - diffusion not efferent enough to meet demands
What are the 2 models of circulatory systems?
Single circulatory system- blood passes through the heart once during one complete circuit of the body
double circulatory system - blood passes through the heart twice during one complete circuit of the body
Explain the single circulatory system in fish?
- Deoxgenated blood pumped from HEART —> GILLS
- Gills are exchange site - blood becomes OXYGENATED
flows from GILLS —> REST OF BODY - Blood RETURNS TO HEART (has one atrium/one ventricle)
Explain double circulatory system in mammals?
Have left side/right side to deliver oxygenated/ deoxygenated blood
- blood on RHS —> LUNGS (pulmonary circuit)
- LUNGS —> LHS
- LHS —> REST OF BODY (systemic circuit)
- BODY —> RHS
Heart?
Hollow, muscular organs in chest cavity that pumps blood
Artery and arterioles?
Arteries : blood vessels that carry bloo away from heart
Arterioles : smaller arteries that branch from larger arteries/connect capillaries
Capillaries?
Tiny blood vessels that connect arterioles/venules
Veins and venules?
Veins - blood vessels that carry blood to heart
Venules - small veins that join capillaries to larger veins
Advantages of double circulation?
- Blood only passes through one capillary network before returning to the heart
So :
the double circulation maintains higher blood pressure and average speed of flow
Therefore, helps to maintain a steeper concentration gradient - efficient exchange of nutrients and waste with the surrounding tissues
What is an open and closed circulatory ssystem?
CLOSED : blood pumped around body/contained in a network of blood vessels
OPEN : blood not contained in blood vessels but pumped directly into body cavities
Structure of arteries?
Walls consist of 3 layers
TUNICA ADVENTITIA/EXTERNA: covers exterior of artery - COLLAGEN
- protect blood easels from damage by overstretching
TUNICA MEDIA:
smooth muscle cells: withstand high pressure /enable contract/narrow lumen
thick layer of elastic tissue - maintain blood pressure - stretches and recoils to even out fluctuations in pressure
TUNICA INTIMA: endothelial layer (one cell thick)
layer of connective tissue
layer of elastic fibres
Narrow lumen /pulse is present
Structure of arterioles?
- muscular layer- can contract /partially cut off blood flow to specific organs
- lower proportion of elastic fibres
Structure of veins?
Tunica media is thinner
- thinner muscular wall - don’t need to withstand high pressure
More collagen than arteries: structural support to hold larger vol of blood
Lumen is larger - ensures blood returns to heart at an adequate speed
- reduces friction between the blood and the endothelial layer of the vein
Has valves /no pulse
Structure of venules?
Large lumen
Few/no elastic fibres
structure of capillaries?
Very small diameter- forces the blood to travel slowly - allows for diffusion to occur
- only large enough for RBCs to pass in single file
Branch between cells - allow diffusion between cells and blood - short diff distance
Wall made from endothelial cells (1 cell thick) - reduce diff distance
- cells of wall have PORES: allow blood plasma to lead out/form tissue fluid
No muscle /elastic tissue
Explain tissue fluid formation?
At arterial end:
Hydrostatic pressure > osmotic pressure
- fluid moves out capillary
- proteins remain in blood as too large - creates WP GRADIENT between capillary and tissue fluid
At venous end:
Hydrostatic pressure in capillary reduced as INCREASED DISTANCE FROM HEART /SLOWER BLOOD FLOW when in capillaries /due to FLUID LOSS at arteriole end
Proteins in blood exert a high oncotic pressure, a type of osmotic pressure, in capillaries.
The water potential is lower in capillaries than in tissue fluid due to fluid loss.
Osmotic pressure > hydrostatic pressure*
- water flows back into capillary from tissue fluid BY OSMOSIS
10% of tissue fluid doesn’t return back to capillary/ remains as tissue fluid - collected by LYMPH VESSELS and returned to circulatory system
What causes Oedema?
If BP is high , then pressure at arterial end is GREATER
- pushes MORE FLUID OUT of capillary/fluid accumulates around tissues
What is hydrostatic and oncotic pressure?
HYDROSTATIC : pressure exerted by fluid
E.g blood pressure
ONCOTIC : osmotic pressure exerted by plasma proteins in blood vessel
- proteins lower WP so water moves into blood vessel by osmosis
What is plasma and tissue fluid?
Plasma - straw colour liquid that constitutes 55% of blood
- good solvent as mostly water
Tissue fluid : when plasma leaks out through gaps in walls of capillary and surrounds cells of body
Structure of lymph vessels? How is liquid moves along these vessels?
- Closed ends
- large pores that allow larger molecules to pass through
- have small valves in vessel walls
- liquid moves along by compression caused by body movement / backflow prevented by valves
Purpose of lymph/lymph vessels?
- Larger molecules that are not able to pass through capillary wall enter lymphatic system as LYMPH
- can return any plasma proteins that have escaped blood , back into blood
Difference in composition of tissue fluid vs plasma?
Plasma has :
Higher conc of GLUCOSE
Higher conc of GLYCEROL/FATTY ACIDS
Higher conc of PLASMA PROTEINS
A lower water potential
Pathway of blood through the heart?
VENA CAVA —> RA —> AV valve (tricuspid)—> RV —> Semi lunar valve —> pulmonary artery —> LA —> AV valve (bicuspid)—> LV —> Semi Lunar Valve —> Aorta
Cardiac cycle? What is systole and diastole?
Series of events that take place in one heart beat , including muscle contraction/relaxation
Systole = contraction of heart
Diastole = relaxation of heart
What happens in atrial systole?
Walls of atria CONTRACT / ventricles relax
- Atrial volume decreases
- Atrial pressure increases
pressure in the atria > pressure in ventricles, forcing (AV) valves open
- Blood is forced into the ventricles - pressure in ventricles increase a bit
What happens in ventricular systole?
walls of ventricles contract/ Atria relax (atrial diastole)
- Ventricular volume decreases
- Ventricular pressure increases
pressure in the ventricles > pressure in atria
- forces the AV valves to close, preventing back flow of blood
pressure in the ventricles > pressure in aorta/ pulmonary artery
- forces the SL valves open
What happens in diastole?
The ventricles and atria are both relaxed
pressure in the ventricles < pressure in aorta and pulmonary artery, forcing the SL valves to close
Blood returns to the heart via the vena cava and pulmonary vein/ atria fill with blood
Pressure in the atria > pressure in ventricles, forcing the AV valves open - Blood flows passively into the ventricles without need of atrial systole
The cycle then begins again with atrial systole
What is cardiac output? Equation?
Volume of blood that is pumped by heart per unit time
CO= Heart Rate x Stroke volume
What is heart rate and stroke volume?
HR : number of time a heart beats per minute
Stroke Volume: plume of blood pumped out the Left Ventricle during one cardiac cycle
Myogenic?
Heart will beat without any external stimulus
How is heart rate /rhythm controlled?
Sinoatrial node (SAN) : cells in RA
- initiates wave of depolarisation —> causes ATRIA TO CONTRACT
- reaches collagen fibres which prevents depolarisation spreading to ventricles straight away (DELAY - Allows ventricle to fill with blood)
Depolarisation carried to Atrioventricular node (AVN)
- AVN passes stimulation along BUNDLE OF HIS (conducting tissue in septum )
Divides into 2 conducting fibres - PURKYNE TISSUE / carries wave of excitation along them
Pukyne fibes spread around ventricles/initiate depolarisation of ventricles from bottom of heart —-> VENTRICULAR SYSTOLE ( blood pushes upwards/outwards)
Explain ECG diagrams?
P wave = Caused by the depolarisation of the atria, which results in atrial contraction (systole)
The QRS complex
Caused by the depolarisation of the ventricles, which results in ventricular contraction (systole)
- largest wave as ventricles have the largest muscle mass
The T wave
Caused by the repolarisation of the ventricles, which results in ventricular relaxation (diastole)
What is Tachycardia , Bradycardia , Ectopic Heartbeat and fibrillation?
Tachycardia : heart beats too fast (evenly spaced)
>100 bpm
Bradycardia : heart beats too slow (evenly spaced)
<60 bpm
Ectopic HR : early heartbeat followed by pause
Fibrillation : irregular heartbeat - disrupt rhythm of HR
- no P wave present - heart rate is controlled by SAN predominantly /its damaged in fibrillation
Structure of haemoglobin?
- contains 4 haem groups (containing iron) - each bond to molecule of O2
- quaternary structure
4 polypeptide chains
Reaction between oxygen and haemoglobin?
Oxygen + Haemoglobin —> Oxyhaemoglobin
- reversible
4O2 + Hb —> Hb4O2
3 ways CO2 is transported around body?
- Small % dissolved in blood plasma / transported in solution
- CO2 binds to haemoglobin —> carbaminohaemoglobin
- larger % transported in form of hydrogen carbonate ions (HCO 3-)
Formation of hydrogen carbonate ions?
CO2 diffuse from PLASMA —> RBCS
In RBCs , CO2 + H2O —> H2CO3 - combine with water to form CARBONIC ACID
- catalysed by CARBONIC ANHYDRASE - enzyme in RBCs
Carbonic acid dissociates :
H2CO3 —> HCO 3- + H+ ( into hydrogen carbonate ions and hydrogen ions)
H+ combines with haemoglobin = haemoglobinic acid - prevents H+ from lowering pH
- Haemoglobin is buffer
Hydrogen carbonate ions diffuse out RBC into plasma /transported in solution / chloride ions move into RBCs
- balance the charge
What is an oxygen dissociation curve ? What is partial pressure of oxygen?
Shows rate at which oxygen associates and dissociates with haemoglobin at different partial pressures of oxygen
Partial pressure of oxygen is measure of oxygen conc
Why is the dissociation curve an S-shape ?
- At first its difficult for oxygen to bind to haemoglobin due to its shape —> slower binding - shallow part at bottom
- After first molecule of O2 has binded , haemoglobin protein changes shape - conformational changes
- easier for next O2 molecule to bind = FASTER BINDING - steeper part - As haemoglobin approaches saturation , takes longer for 4th molecule to bind due to SHORTAGE OF BINDING SITES - levels off at top
Explain the oxygen dissociation graph ?
At low pO2 : Haemoglobin has LOW AFFINITY for oxygen , so binds slowly/dissociates easier
- saturation of haemoglobin is LOW
- dissociation slows (bc few O2 molecules left on binding sites/release of last O2 molecule is most difficult)
At medium pO2: oxygen binds more easily to haemoglobin /saturation increases quickly
- small increase in pO2 = large increase in saturation
- dissociates readily
At high pO2:
- haemoglobin has HIGH AFFINITY for O2 at high pO2
So binds easily
so saturation of O2 is high
- little dissociation
How and why is foetal haemoglobin different to adult haemoglobin?
Has higher affinity for oxygen than adult haemoglobin, at any partial pressure (dissociation curve moves left)
SO THAT:
- foetus can obtain oxygen from mother’s blood at placenta (which is low pO2) - can bind to oxygen as low pO2 by having higher affinity
After birth, adult haemoglobin replaces foetal - allows easy release of O2 for respiring tissues as larger metabolic rate
What is the Bohr effect?
Describes the change in affinity for oxygen , haemoglobin has , due to increased partial pressure of CO2
- changes in dissociation curve - shift right (lower affinity for O2 at any pp)
- lower affinity = OXYGEN IS RELEASED FROM BLOOD - haemoglobin gives up its oxygen more readily
(When Hydrogen ions bind to haemoglobin - causes release of O2)
Circulatory system in insects? Why do they have less efficient circulatory systems?
- have one main blood vessel - DORSAL VESSEL
- tubular heart pumps blood into dorsal vessel
- dorsal vessel delivers blood to BODY CAVITY
Blood surrounds ORGANS/reenters heart through valves called OSTIA - doesn’t need to have efficient circulatory system bc oxygen delivered to tissues via tracheae (in tracheal system)
PRACTICAL : heart dissection
External examination:
- look at outside of heart /identify 4 main vessels
Feel inside vessels to help (arteries are thicker than veins)
Draw sketch of both ventricles and atria
Internal examination: cut along lines to look inside ventricles
- measure/record thickness of ventricle walls
- cut open atria/note whether they’re thicker/thinner than ventricles
Find AV/SL valves and look at structure
Draw sketch showing valves/inside of ventricles and atria
Composition of tissue fluid compared to lymph ?
Both: no RBCS- remain in blood bc too large
No platelets
Very few proteins
Water/dissolved solutes
Lymph: WBCs/antibodies
