7. Human body systems

What do unicellular organisms rely on for gas exchange?

Outer surface diffusion

How many gases do organisms absorb and release in gas exchange?

Organisms absorb one gas and release another

What do larger animals need for gas exchange?

Specialised gas exchange systems, transport systems to provide cells with sufficient oxygen for respiration.

Why do gas exchange surfaces need a large surface area?

To increase the quantity of gas particles exchanged.

Why do gas exchange surfaces need moisture?

To allow the gases to dissolve and diffuse rapidly

Why do gas exchange surfaces need a thin tissue layer?

To reduce the time/distance it takes for gases to diffuse

Why do gas exchange surfaces need to be permeable?

To allow oxygen and carbon dioxide to diffuse

Why do gas exchange surfaces need to have a high concentration gradient?

To allow gases to diffuse from a high concentration to low concentration.

Which gases are consumed and produced in respiration?

Oxygen is consumed and carbon dioxide is produced

What order are the structures in mammalian lungs in?

Trachea → bronchi → bronchioles → alveoli

How thick are alveoli and capillaries?

One cell thick

What is the function of a dense capillary network in mammalian lungs?

Maintains concentration gradient

What is the function of surfactant in mammalian lungs?

Reduces surface tension, prevents collapse

What is the function of elastic fibres in mammalian lungs?

Allows recoil during exhalation

Why is a dense network of capillaries needed to maintain high concentration gradients?

Increases blood supply to the exchange surface, bringing more oxygen and carrying away more carbon dioxide

Why is a continuous blood flow needed to maintain high concentration gradients?

Ensures that blood with low oxygen and high carbon dioxide is constantly replaced

Define ventilation

The movement of air in and out of the alveoli in the lungs, facilitating gas exchange, aka breathing

Define respiration

The release of ATP energy from organic compounds (food), which occurs in cells

Why are branching bronchioles important as adaptations of the lungs?

They connect to many alveoli

Why have alveoli evolved to have large surface areas?

For faster gas exchange

Why are Type I pneumocytes thin?

To ensure a short diffusion pathway

What do Type II pneumocytes secrete?

Alveolar fluid

What is the role of alveolar fluid?

Moistens the surface of the alveoli, allowing gases to dissolve into the surfactant before diffusing across the wall of the alveoli and capillary into the blood

What does alveolar fluid contain?

Surfactant, a mixture of lipids and proteins

What is the role of surfactant?

Reducing the surface tension of the alveoli, which helps to prevent alveolar collapse during exhalation

What do internal intercostal muscles do in inhalation?

Relax

What do external intercostal muscles do in inhalation?

Contract, moving the ribcage up and out

What happens to the volume in the thorax in inhalation?

Increases

What happens to the pressure in the lungs in inhalation?

Decreases

What does the diaphragm do in inhalation?

Contracts and moves downwards

What do external intercostal muscles do in exhalation?

Relax

What do internal intercostal muscles do in exhalation?

Contract, moving the ribcage down and inwards.

What happens to the volume in the thorax in exhalation?

Decreases

What happens to the pressure in the lungs in exhalation?

Increases

What does the diaphragm do in exhalation?

Relaxes, moves up and in

How can age affect human lung capacities?

Lung capacities tend to increase with age up to about 25 years of age

How can body composition affect human lung capacities?

Larger people tend to have larger lungs and so have larger lung capacities

How can biological sex affect human lung capacities?

In general, males tend to have larger lung capacities than females

How can respiratory diseases affect human lung capacities?

Diseases such as chronic obstructive pulmonary disease (COPD) and asthma can reduce lung capacities

How can levels of physical activity affect human lung capacities?

Regular exercise can increase lung capacities

Define tidal volume

The volume of air that moves in and out of the lungs in a normal breath.

Define inspiratory reserve

The additional volume of air that can be inhaled with maximum effort.

Define expiratory reserve

The additional volume of air that can be exhaled with maximum effort.

Define vital capacity

The greatest volume of air that can be expelled from the lungs after the deepest possible breath.

How has the waxy cuticle adapted for gas exchange in leaves?

Covers the epidermis cells and reduces the evaporation of water from the leaf.

How has the epidermis adapted for gas exchange in leaves?

Provides protection for the mesophyll cells within the leaf. Are transparent, allowing light to reach the mesophyll cells where photosynthesis is carried out.

How has the spongy mesophyll adapted for gas exchange in leaves?

Irregular shape increases the surface area for gas exchange, are surrounded by air spaces.

How have air spaces adapted for gas exchange in leaves?

Facilitate the diffusion of gases between the surrounding atmosphere and the mesophyll cells.

How have stomata adapted for gas exchange in leaves?

Allow gases to enter and exit the leaf. Usually more common on the lower epidermis of the leaf. Open and closed by guard cells.

How have veins adapted for gas exchange in leaves?

Provide support for the leaf, contain xylem and phloem tissue. Xylem tissue transports water and dissolved minerals, and phloem tissue transports sugars and amino acids

Define transpiration

The loss of water vapour through the leaves, stems, and other above-ground parts of the plant.

How does light intensity affect the rate of transpiration?

As it increases, more stomata open. If there are more open stomata, then more water can diffuse out of the leaf, increasing the rate of transpiration.

How does temperature affect the rate of transpiration?

As it increases, water particles gain kinetic energy, and move faster. Faster moving water particles diffuse through the stomata of the leaf at a faster rate.

How does humidity affect the rate of transpiration?

As it increases, the concentration of water outside the leaf increases. This decreases the concentration gradient between the inside and outside of the leaf. Water particles will diffuse slower, resulting in a slower rate of transpiration.

How does air flow affect the rate of transpiration?

It moves water vapour away from the leaf, reducing the concentration of water outside the stomata of a leaf. This increases the concentration gradient, resulting in an increase in the rate of transpiration

Define stomatal density

The number of stomata per mm² of leaf surface

What does higher stomatal density mean?

Greater CO₂ uptake but higher water loss

How are narrow lumen an adaptation of capillaries for exchange of materials?

Forces red blood cells through single file

How are one cell thick walls an adaptation of capillaries for exchange of materials?

Reduce diffusion distance

How are permeable pores an adaptation of capillaries for exchange of materials?

Allow exchange of materials between cells in the tissue and the blood in the capillary.

How is the dense branching area an adaptation of capillaries for exchange of materials?

Large surface area, increases rate of diffusion

What is the structure of a capillary?

Very small lumen, single-cell wall

What is the structure of an artery?

Thick outer walls, thick layer of muscles and elastic fibres, small lumen

What is the role of arteries?

Transport high pressure blood away from the heart

What is the structure of an vein?

Thin outer wall, thin layer of muscle and elastic fibres, large lumen, valves

What is the role of veins?

Return blood to the heart at a low pressure

How are thick muscular walls in arteries adapted for blood transport?

Allow arteries to withstand high blood pressure

How are elastic fibres in arteries adapted for blood transport?

Allow the arteries to stretch and recoil as pressure increases and decreases due to heart beats.

How are smooth endothelial cells in arteries adapted for blood transport?

Reduces resistance/friction as blood flows.

How are narrow lumen in arteries adapted for blood transport?

Helps maintain high blood pressure

How is collagen in the outer wall of arteries adapted for blood transport?

Strengthens the artery to withstand high blood pressure.

How are smooth muscle in arteries adapted for blood transport?

Can contract to maintain blood pressure between heart beats.

Define pulse

Pressure waves from ventricular contraction

How to measure pulse?

Radial pulse at wrist or carotid pulse at neck

What digital devices can measure pulse?

Oximeters, fitness trackers

How are one-way valves in veins adapted for return of blood?

Prevent backflow

How are skeletal muscle contractions in veins adapted for return of blood?

Compress veins to move blood back to the heart

How are thin walls in veins adapted for return of blood?

Allow the vein to be compressed by skeletal muscles

Define atherosclerosis

Hardening and narrowing of the arteries due to the build of cholesterol, triglycerides and other substances on artery walls.

What is the occlusion of coronary arteries caused by?

Atherosclerosis (plaque buildup)

What risk factors of atherosclerosis are out of our control?

Genetics, age, gender

What risk factors of atherosclerosis are within our control?

High fat diet, smoking, hypertension, diabetes, inactivity

What could atherosclerosis lead to?

Angina, myocardial infarction, heart failure, arrhythmias

What are coronary arteries?

They branch off of the main artery, the aorta, and supply the heart with oxygen and nutrients.

How can coronary arteries be blocked/narrowed?

By deposits of fat called atheroma (plaque), made of lipids and cholesterol. A blockage is referred to as an occlusion.

What happens if a plaque ruptures?

Blood clotting is triggered, forming a thrombus (blood clot) that restricts blood flow.

What is the Pearson correlation coefficient (r) used for?

To quantify correlations between variables and allow the strength of the relationship to be assessed.

What can be assumed if the correlation coefficient is close to zero?

There is no relationship between the two variables - this can disprove a hypothesis

Define transpiration

The movement of water through a plant, and its evaporation from aerial parts of the plant such as leaves.

What is the role of transpiration pull in water transport in plants?

Generates negative pressure

What is the role of cohesion in water transport in plants?

Keeps water molecules linked

What is the role of adhesion in water transport in plants?

Water molecules stick to cellulose in the cell wall, preventing collapse of water column

What is the role of capillary action in water transport in plants?

Aids upward flow

How are dead cells an adaptation for transport of water in the xylem vessel?

Allows for a column of water to move up the plant.

How are no cell contents/plasma membrane an adaptation for transport of water in the xylem vessel?

Allows unimpeded flow of the transpiration stream.

How are pits an adaptation for transport of water in the xylem vessel?

Allow water to move between the xylem and adjacent cells.

How is lignin an adaptation for transport of water in the xylem vessel?

Strengthens the cell walls of xylem which allows the xylem vessels to resist the inward pressures created by transpiration.

What is the role of the epidermis in the dicotyledonous stem?

Provides protection for the stem.

What is the role of the cortex in the dicotyledonous stem?

Provides structural support for the stem, and stores starch in the root of plants.

What is the role of the vascular bundle (xylem and phloem) in the dicotyledonous stem?

Transport materials up and down the plant.