(U2) T&EM - Circulatory System In Mammals Flashcards
1
Q
Give an account of the sequence of events which result in coordination of the flow of blood through the heart during one cardiac cycle
with regard to Atrial systole (4)
A
- cardiac muscle cells are myogenic
- excitation wave is initiated at the SA-node
- electrical impulses discharged across atrial muscle triggers atrial systole
- electrical impulses cannot pass directly to the ventricle muscle (sheet of non-conductive connective tissue between atria and ventricles)
2
Q
Give an account of the sequence of events which result in coordination of the flow of blood through the heart during one cardiac cycle
with regard to ventricular systole (10)
A
- AV-node “picks-up” the impulses from the atrial muscle
- impulses pass along the Bundle of His and Purkinje fibres to the ventricle wall
- ensures ventricular systole follows atrial systole
- ventricular systole increases pressure within the ventricles
- blood pressure increases from the base of the ventricles
- blood is forced against the AV-valves which close
- the chordae tendinae prevent the AV-valves blowing inside out (so preventing reflux of blood into the atria)
- closure of the AV-valves causes the first heart sound
- semilunar valves are blown open
- blood exits the ventricles via the pulmonary artery/aorta
3
Q
Give an account of the sequence of events which result in coordination of the flow of blood through the heart during one cardiac cycle
with regard to diastole (7)
A
- ventricular diastole results in a decrease in pressure within the ventricles
- semilunar valves close/as “pockets” fill with blood/ventricular pressure is less than the pressure in the artery
- closure of the semilunar valves causes second heart sound
- reflux of blood into the ventricles is prevented
- blood returns to the atria from the venae cavae or pulmonary veins (also during ventricular systole)
- as atria fill with blood, pressure increases/the AV-valves are pushed open during atrial diastole
- blood moves from atria to ventricles
4
Q
What is the purpose of the semilunar valves closing?
When do they close?
Why?
A
- Prevents reflux of blood from aorta / pulmonary artery back into ventricles
- diastole (heart not contracting)
- ventricular pressure is less than arterial pressure
5
Q
Why is the mammalian circulatory system referred to as being a double circulation?
A
Blood enters the heart twice in a complete circuit
6
Q
What term is used to describe the supply of blood to the lungs from the heart?
Which part of the heart pumps the blood?
A
- pulmonary circulation
- the right ventricular muscle wall (which is thinner than the left ventricular muscle)
7
Q
What term is used to describe the supply of blood to the body from the heart?
Which part of the heart pumps the blood?
A
- systemic circulation
- left ventricular muscle wall (comparatively thicker than right)
8
Q
How are arteries structured? (5)
A
- thin outer layer of fibrous tissue
- thick middle layer of smooth muscle and elastic tissue
- inner layer of squamous endothelial cells
- narrow lumen
- rounded shape
9
Q
How are veins structured? (6)
A
- thin outer layer of fibrous tissue
- thin middle layer of muscle and little elastic tissue
- inner layer of squamous endothelial cells
- large lumen
- less regular shape than arteries
- valves
10
Q
How are capillaries structured?
A
1 cell thick walls of squamous endothelium
11
Q
What is the general pressure in:
- arteries
- veins
- capillaries
A
- arteries: relatively high
- veins: relatively low
- arteries: reduction across capillary network
12
Q
What are the adaptations of arteries? (5)
A
- elastic tissue in the middle layer allows the artery to stretch as blood is pumped
- when the elastic tissue recoils between heartbeats, it helps push blood along the artery, maintaining blood pressure
- the muscle tissue in the middle layer provides support
- the muscle also allows vasoconstriction or vasodilation to limit or increase blood flow to organs
- contraction and narrowing of the lumen helps maintain blood pressure
13
Q
What are the adaptations of veins? (4)
A
- large lumen - little resistance to blood flow
- valves prevent back flow of blood
- fibrous outer covering and endothelial layer create a smooth surface, reducing friction as blood flows through
- due to low pressure; gravity and contraction of surrounding muscle is largely responsible for blood flow
14
Q
What are the adaptations of capillaries? (4)
A
- extensive network - large SA for diffusion of substances
- thin squamous epithelial cells and wall only 1 cell thick - short diffusion distance
- squamous epithelial cells are permeable to water and solutes, aiding diffusion
- proximity of RBCs to wall of capillary reduces diffusion distance
15
Q
How is a mammalian heart structured? (Not including nervous tissue) (8/9)
just features
A
- Upper chambers - atria
- Lower chambers - ventricles
- Atrioventricular valves
- Aorta out of left ventricle
- Pulmonary artery out of right ventricle
- Venae cavae - into right atrium
- Pulmonary vein - into left atrium
- Coronary arteries - break off from aorta
Left and right of the heart separated by the septum
16
Q
What are the features / roles of atria?
A
- thin wall of muscle
- receive blood from lungs (left atrium) or the body (right atrium)
- pump blood short distance to ventricles
17
Q
What are the features / roles of ventricles?
A
- thicker walls than atria; left ventricle thicker than right
- left ventricle pumps blood around the body, right pumps blood to lungs
- therefore left needs to pump with greater force
18
Q
What are the roles of the different types of valves?
And
Where are they situated?
A
- atrioventricular between atria and ventricles:
- open when pressure in atria exceeds pressure in ventricles
- these are anchored by chordae tendinae and papillary muscles to prevent going inside out
- bicuspid (2 flap) valve on left, tricuspid (3 flap) on right
- also semilunar valves at the base of the aorta and pulmonary artery:
- close when blood pressure in arteries exceeds pressure in the ventricles
- when blood is pumped into arteries, they push against the artery wall & don’t impede flow
19
Q
What is the role of the aorta? (2)
A
- carries oxygenated blood from left ventricle around the body
- branch into coronary arteries which supply coronary muscle with oxygenated blood
20
Q
What is the role of the pulmonary artery?
A
Carries deoxygenated blood from the right ventricle to the lungs
21
Q
What is the role of the pulmonary vein?
A
Carries oxygenated blood from lungs to the left atrium
22
Q
What is the role of venae cavae?
A
Carry deoxygenated blood from the body to the right atrium
23
Q
Give an account of atrial systole (not including nervous coordination) (6)
A
- walls of atria contract, forcing blood into ventricles
- AV valves open as pressure in atria exceeds pressure in ventricles
- blood continues to enter atria from venae cavae and the pulmonary vein
- walls of ventricle are relaxed
- ventricle volume increases as they fill with blood
- semilunar valves are closed
24
Q
Give an account of ventricular systole (not including nervous coordination) (6)
A
- walls of atria relax
- walls of ventricles contract
- AV valves close as pressure in the ventricles exceeds pressure in atria
- chordae tendinae prevent AV valves blowing inside out, but they do bulge slightly into atria
- ventricle pressure peaks, semilunar valves forced open, blood moves into arteries where pressure is lower
- ventricles reach smallest volume
25
Give an account of **diastole** (*not including nervous coordination*) (**5**)
- **atrial walls relax**
- blood *enters atria from venae cavae and the pulmonary vein*
- **ventricle walls also relax** and **semilunar valves close** - *arterial pressure > ventricular pressure*
- *reflux of blood into ventricles **prevented***
- **atrioventricular valves open**; *blood enters ventricles from atria*
26
What is the **order** of the **cardiac cycle**?
- atrial systole
- ventricular systole
- diastole
27
What does **myogenic** mean?
(The heart) can beat on its own *without external stimulation*
28
Where do **electrical stimuluses** in the **heart** *originate from*?
The Sinoatrial node (SAN)
## footnote
This is an area of muscle in the **right atrium**
29
**Why can’t** *electrical stimuluses pass directly* to the **ventricles from the SAN**?
How do they pass instead?
Why is this good?
- A layer of **non-conductive tissue** *between atria and ventricles*
- **atrioventricular node (AV node)** which conducts slowly (delaying ventricular systole)
- allows **ventricular systole** to **begin once atrial systole is complete** and *ventricles are filled with blood*
30
*After the AV node*, **where** does an **electrical stimulus travel**?
- *down the septum* via **bundle of His** to the *bottom of ventricles*
- then in **Purkinje fibres**, which *trigger contraction of ventricular walls*,
## footnote
Contraction from bottom to top of ventricle walls
31
What is the **cause** of the:
- P wave
- QRS complex
- T wave
In an *electrocardiogram*?
- P wave: *electrical stimulus* that causes **contraction of atria**
- QRS complex: *electrical stimulus* that causes **contraction of ventricles**
- T wave: **relaxation** of the **ventricles**
32
**Why** is the *R peak* *so much greater* than the **P peak** in an **electrocardiogram**?
R peak represents a **stimulus targeting the ventricles**, which have **thicker muscle** and thus **require a larger stimulus**
33
What is *represented* by the **short straight section** *between P and QRS* in an **electrocardiogram**?
The **wave of excitation** *passing through* the **AV node**
34
What are the **components** of the **blood**? (**4**)
| give different types where neccessary
1. platelets
2. plasma
3. red blood cells
4. White blood cells:
- monocytes
- polymorphs
- lymphocytes
35
What are **platelets**?
and
What is their **function**?
- cell fragments
- key role in **blood clotting** and **repairing minor breaks in blood vessels**
36
What is **plasma**?
and
What is its **function**?
- largely **aqueous liquid** that **holds blood components** *in suspension*
- transports *blood cells, glucose, amino acids & products of digestion, ions, CO2, urea, heat, prothrombin, fibrinogen, clotting factors* and other substances
37
What are the **adaptations** of **red blood cells**? (**5**)
1. their *number*:
- **increases capacity to carry oxygen** in blood
2. *small size*:
- *aids movement* **through capillaries**
- **proximity of haemoglobin** molecules *to cell surface* - **shorter diffusion distance**
3. *biconcave shape*:
- **increases SA** and **SA/V ratio**
4. *Lack a nucleus* or *organelles*:
- **increases volume** for **storing haemoglobin**
5. *Contain haemoglobin*:
- **carries oxygen** & *doesn’t impact water potential of plasma*
- by being in cells, **prevents blood becoming viscous**
38
What are the **general characteristics** of **polymorphs**? (**4**)
- **most common** white blood cell
- **multi-lobed nucleus**
- **granular cytoplasm**
- **phagocytic** and can *pass between squamous epithelium and capillary cells*, **destroy bacteria & other bodies** by **phagocytosis**
39
What are the **general characteristics** of **monocytes**? (**4**)
- **largest** but **least common** white blood cell
- **bean-shaped nucleus**
- **phagocytic** and can *move out of blood, develop into **macrophage** cells* that *destroy bacteria & other bodies* by **phagocytosis**
- **longer lifespan** than **polymorphs**
40
What are the **general characteristics** of **lymphocytes**? (**3**)
- make up about **20/25%** of white blood cells
- **very large nucleus**, *small amount of cytoplasm*
- **2 types**:
1. **B-Cells**, involved in *antibody production*
2. **T-cells**, involved in *cell-mediated immunity*
41
What is an **angiograph**?
What is it *used for*?
- a type of **X-ray** that **uses dye** - *added via a catheter*
- allows *identification* of the *extent* of **blood vessel narrowing, blockage** or **damage** e.g. diagnosing CHD, aneurysm and atherosclerosis
42
Outline the **processes** involved in **blood thrombosis** (**4**)
- damage to tissues / blood vessels
- *platelets* activated - **release thrombokinase** -> (this can form a plug to seal minor damage or reduce rate of blood loss)
- **thrombokinase catalyses** the *conversion* of **prothrombin to thrombin** - using *clotting factors* such as **Vitamin A and calcium ions**
- **thrombin catalyses** the *conversion* of **soluble fibrinogen to insoluble fibrin*
43
Outline the **formation** of **tissue fluid** (**5**)
- **hydrostatic pressure** created by *blood travelling through progressively narrower* vessels: **arteries, arterioles, arterial end of capilaries**
- **ultrafiltration** - liquid and small molecules *forced out of capillaries*
- **arterial end** of capillaries; **hydrostatic pressure** *exceeds* **force of osmosis into blood** (which has lower water potential) *and* the **hydrostatic pressure** of *tissue fluid* (**opposing inward flow**)
- **loss of fluid** *from capillary* causes a **reduction in hydrostatic pressure**. The *hydrostatic pressure of tissue fluid* **exceeds** *hydrostatic pressure of the blood* **at the venule end**
- also **lower water potential in blood**: *water diffuses back* into bloodstream
44
How is haemoglobin structured? (**2**)
What does it **form** when it **undergoes** a *reversible* **reaction with oxygen**?
1.
- **4 polypeptide** chains - *2 alpha and 2 beta* chains
- each has an **iron containing Haem prosthetic group**, making molecules **conjugated**
2. Forms oxyhaemoglobin
45
What is the **shape** of the **oxygen dissociation curve** for *haemoglobin*?
What does this mean? (**3**)
1. Sigmoidal (s shaped)
2.
- **high pO2** cause *oxyhaemoglobin to readily form*, **nearing full saturation**
- **haemoglobin remains saturated** *as pO2 falls*
- **low pO2** (i.e. in respiring muscle) *mean oxyhaemoglobin readily dissociates*, **oxygen is released**
46
What is **loading tension**?
The **partial pressure** at which **haemoglobin is 95% saturated** with oxygen
47
What is **unloading tension**?
The **partial pressure** at which **haemoglobin is 50% saturated** with oxygen
48
What is the **equation** for the *production* of **oxyhaemoglobin**?
Hb + 4O2 ⇌ HBO8
49
Explain what is meant by **co-operative loading** (**2**)
- when **1 oxygen molecule binds** to a *haem group*, a **conformational change** occurs in the *tertiary structure* of the haemoglobin molecule
- this change makes it **easier** for **other oxygen molecules to bind**
50
What is meant by a **fully saturated haemoglobin** molecule?
Where all 4 haem groups bind to oxygen
## footnote
- 50% saturated, only 2 oxygen molecules bind to haem groups
- blood is 50% saturated if 50% of haemoglobin carries oxygen
51
What **factors** cause the **Böhr effect**? (**3**)
- increased pCO2
- increased blood temp
- decreased blood pH
52
What is the **Böhr effect**?
*Why* is it *important*?
- when haemolgobin’s **affinity for oxygen decreases** (*oxygen released at higher pO2*)
- **more oxygen** is therefore available for **respiring tissues**
53
What **effect** does the **Böhr effect** have on the *oxygen dissociation curve for haemoglobin*?
Curve shifts **right** (so *unloading tension* shifts right too)
54
What is **Myoglobin**?
How is it **structured**?
- A **respiratory pigment** found in *red muscle*
- 1 polypeptide chain with 1 haem group
55
**Where** is the *oxygen dissociation curve* for **myoglobin** in *relation to haemoglobin*?
**Why**?
What does this mean it can be **used as**?
- To the **left**
- myoglobin has **greater oxygen affinity** and **only releases** oxygen at **very low pO2** (i.e. during highly strenuous exercise)
- oxygen store
56
What is the **benefit** of **myoglobin** as an **oxygen store**? (**3**)
- *only releases oxygen* when **haemoglobin reserves** are **depleted**
- **delays onset** of *anaerobic respiration* (aerobic respiration can continue)
- also *unsaturated myoglobin* can **bind to oxygen** that **dissociates from haemoglobin** *after exercise*
57
What is the *effect*of **acclimatisation at high altitudes**?
- **More red blood cells** created
- meaning **more efficient transport of oxygen**; *compensates for reduced saturation* of haemoglobin at the *low pO2*
58
For mammals that adapted to live at **high altitude**, what is the *difference* between their **haemoglobin oxygen dissociation curves** and normal ones? (**2**)
- curve is to the *left of normal* (**greater oxygen affinity**)
- haemoglobin **fully saturates at low pO2**
59
What is an **atheroma**?
What **factors** make it more likely?
- *build up* of **cholesterol deposits** within the **lumen of an artery**
- stress, smoking, high blood cholesterol, poor diet, lack of exercise, high salt intake etc.
60
How do **atheromas develop**? (**4**)
What does this **cause**?
1.
- **squamous endothelial** cells of artery **damaged**
- **macrophages migrate** from blood into the *artery wall, accumulate materials* like cholesterol, dead muscle cells, salts, fibrous tissue - **create hardened plaques** (atheroma)
- atheromas **bulge into lumen** - *narrows - blood flow restricted*.
-** Fibrous material loses elasticity** and *can’t conduct vasoconstriction / vasodilation*
2. Rising blood pressure, increased chance of more atheromas
61
What is **atherosclerosis**?
What does it **cause**?
- *disease* caused by **thickening of the artery wall** by *development* of **atheromas and plaques**
- **fibrous material** becomes *less elastic* —> *lumen* gets *narrower* —> *increase* in *blood pressure* —> **increased chance of thrombosis / embolism / aneurism** etc.
62
How does a **myocardial infarction occur**? (**6**)
| (via thrombosis)
- **cholesterol build** up on walls of **coronary arteries** leads to **narrowing**
- **increases** the **chance** of **thrombosis**
- this **reduces** the **amount of blood** *carrying oxygen and glucose* to *coronary muscle cells* for **respiration**
- as a result the **coronary muscle cells die** (**infarction**)
- this means the **muscle cells** of the heart have to **work harder**
- **myocaridal infarction** - heart attack occurs
