Theme B: B3 Organisms - B3.2 Transport Flashcards
coronary arteries
arteries that supply blood to cardiac muscle. it feeds oxygen and nutrients directly into the muscle tissue of the heart.
plaque
the build up of cholesterol and other substances in the lumen of the arteries. the restriction in blood flow causes an occluison. plaque build up is progressive amd can severely decrease the artery’s blood flow. if the occulded artery s a coronary artery, it may result in a heart attck becasue the cardiac muscle in one of more areas of the heart will be deprived of oxygen.
cohesion-tension theory
the tension force generated by transpiration.
In order to bring water and dissolved minerals up from the roots, a plant relies on a tension force generated by transpiration.
Transpiration is the evaporation of water from leaves through open stomata. The water is located in the air spaces created by the spongy mesophyll layer of the leaf. The loss of water by transpiration causes water to be pulled through the cell walls of nearby xylem tissue by capillary action.
This creates tension (a negative pressure) at the upper end of each xylem tube. The tension results in the movement of water up the xylem, and the entire column of water moves up because of cohesion. This upwards movement of water with dissolved minerals is called the cohesion-tension theory.
formation of xylem tubes
- Imagine many cylinder-shaped plant cells stacked up on each other to make a long tube.
- When alive these cells would have had complete cell walls, plasma membranes and typical plant cell organelles.
- Now imagine that all of these cells die leaving behind only their thick cylinder-shaped cell walls.
- Even the end walls where the cells were joined to each other in the tube completely or partially degenerate.
structure of xylem tubes
Xylem vessels are composed of elongated, hollow cells that are dead at maturity, facilitating efficient water transport. the partial or total lack of cell walls between adjoining cells of the xylem tube allows unobstructed water flow upwards.
Xylem also has small pits (microscopic holes) in its sidewalls that allow the easy flow of water in and out as needed.
The walls of these vessels are thickened with lignin, a complex polymer that provides structural support and prevents collapse under the tension generated during water transport.
Dicotyledonous
Dicotyledonous is one of the two categories of flowering plants: monocotyledons are the other category.
the 5 dicotyledonous stem tissues and their functions
1) epidermis: prevents water loss and provides protection from microorganisms
2) cortex: an unspecialised cell layer that sometimes store food reserves
3) xylem: transport tubes that bring water up form the roots
4) phloem: transports carbohydrates, usually from leaves to other parts of the plant
5) vascular bundle: contains multiple vessels of both xylem and phloem
tissues in a dicotyledonous root
1) Epidermis: Grows root hairs that increase the surface area for water uptake
2) Cortex: An unspecialized cell layer that stores food reserves
3) Xylem: Transport tubes for water and minerals, starting in the roots
4) Phloem: Transport tubes that receive sugars from leaves
5) Vascular bundle: The area in the centre of the root containing xylem and phloem
tissue fluid
In order for cells to chemically exchange substances with blood, there has to be a fluid between the cells and blood. That fluid is called tissue fluid. Think of tissue fluid as the solution that bathes all cells.
tissue fluid is contsntaly renewed by being released from the side of a capillary bed closest to the arteriole.
pressure filtration
Within the capillary bed, blood pressure is highest at the arterial end as blood enters from the arterioles, driven by the heart’s pumping action. This high pressure forces plasma, containing oxygen, nutrients, and other small molecules, out of the capillaries into the surrounding tissues, forming tissue fluid. This process is known as pressure filtration.
difference in pressure within the capillary bed
At the arteriole end of the capillary bed, high hydrostatic pressure forces fluid, nutrients, and gases out of the capillaries into the surrounding tissue, forming tissue fluid. At the venule end, hydrostatic pressure drops due to a loss of fluid and the decreased distance form the heart’s pumpin action. osmotic pressure (due to plasma proteins) draws most of the tissue fluid back into the capillaries, maintaining fluid balance and enabling waste removal.
chemical makeup of blood plasma and tissue fluid
The chemical makeup of blood plasma and tissue fluid is very similar, because of the largely unregulated passage of substances through very porous capillary membranes and gaps under arteriole pressure.
* Red blood cells and large proteins do not exit the capillaries, and thus remain in the blood stream, because they are too large to exit through the capillary walls.
* Some white blood cells are able to squeeze through capillaries into tissue fluid.
arterioles
the smallest of arteries. capillaries receive their blood from arterioles. within body tissues, an arteriole branches into a capillary bed.
capillary bed
a network of capillaries that all receive blood from the same arteriole. a single capillary bed will drain its blood into a venule.
venule
the smallest of veins
how does the lumen of a capillary affect red blood cells passing through?
blood cells line up in single because the lumen (inside diameter) of each capillary is only large enough to accommodate one cell at a time.
composition of a capillary
each capillary is a small tube composed of a single-cell thickness of inner tissue and a single cell thickness of outer tissue. both these cell layers are very permeable to many substances either through the membranes or between the membranes forming the tube.
much shorter than you would expect
reasons for the composition of a capillary bed
the total surface area and extensive branching of a capillary bed is very high, so no cell in the body is far from a capillary.
highly vascular tissue
some metabolically active tissues are especially enriched with capillary beds. this is known as highly vascular tissue
fenestrated capillaries (+ fenestrations)
some tissues that have capillary beds designed to be even more permeable to substances than a typical capillary. these capillaries are said to be fenestrated.
fenestrations are small slits/opening that allow relatively large molecules to exit or enter the blood and allow increased movement of all molecules in a given time period.
examples of fenestrated capillaries:
numerous small capillaries of kidneys and areas of intestine where molecule movement needs to be rapid.
how are capillaries adapted to their function?
1) having smaller inside diameter (small lumen)
2) thin walled
3) permeable
4) large surface area
5) fenestrations (some)
arteries
blood vessels that receive blood from the heart and takes that blood to a capillary bed.
since they directly reduce blood form the heart, the blood is under relatively high pressure. Therefore, arteries are lined with a thick layer of smooth muscle and elastic fibres. the lumen of arteries is relatively small vs veins.
vein
receives blood from a capillary bed and takes that blood back to the heart.
veins receive low pressure blood form capillary beds. they’re relatively thin walled because the blood is under lower pressure, so they don’t need to withstand high pressures. The walls contain less smooth muscle and elastic tissue compared to arteries, making them more flexible and less rigid. They have a larger lumen to carry the slow moving blood.
the autonomic nervous system (ANS) and arteries
each artery is lined with a relatively thick layer of smooth muscles controlled by the autonomic nervous system (ANS). the ANS controls those functions in the body that are necessary but not controlled consciously.
smooth muscle and arteries
Chat definition: Smooth Muscle: Involuntary, non-striated muscle found in the walls of internal organs and blood vessels. It contracts slowly and rhythmically to control functions like digestion and blood flow.
Each artery has a relatively thick layer of smooth muscle. Smooth muscle changes lumen diameter of arteries to help regulate blood pressure.
elastin and collagen (in artery walls)
each artery wall contains the proteins elastin and collagen (in addition to smooth muscle). muscular and elastic tissues allow arteries to withstand the high pressure of each blood surge and it keeps the blood continuously moving.
when blood is pumped into an artery, the elastin and collagen fibres are stretched and allow the blood vessel to accommodate the increased pressure.
Once the blood surge has passed the elastic fibres recoil and provide further pressure, propelling the blood forwards within the artery. In this way the blood in arteries maintains a high pressure between pump cycles of the heart.
pulse rate (heart rate)
A measurement of the number of times your heart beats in a minute. Each time the heart contracts and sends blood directly into arteries, the “pulse” of pressure can be felt in an artery.
You can take your own pulse rate by feeling for the pulse using your index and middle fingers at two possible locations.
* The carotid artery - feel for this artery on either side of your trachea (windpipe)
in your neck.
* The radial artery - feel for this artery on your wrist with the palm of your hand facing upwards. You should feel the pulse 2 cm from the base of your thumb.
Adaptations of veins for the return of blood flow
Veins are blood vessels that return blood back to the heart after the blood has passed through a capillary bed. Blood loses a great deal of pressure and velocity in capillary beds. To account for this:
* veins have thin walls and a larger internal diameter.
* The unidirectional flow of the relatively slow-moving blood in veins is aided by internal valves that help prevent backflow of the blood.
* In addition, the thin walls of veins are easily compressed by surrounding muscles. One of the many reasons to stay active!
How do molecules with natural concentration gradients bypass a body cell’s plasma membrane?
Many of the molecules that have natural concentration gradients, such as oxygen, carbon dioxide and glucose, diffuse directly through the cell’s plasma membrane or diffuse through protein channels in a process called facilitated diffusion.
Body cells are in constant need of oxygen and a variety of nutrients. In turn, body cells produce waste products such as carbon dioxide and a waste product of amino acid metabolism called urea.
& specifically refer to K+ and Na+ ions
How do cells regulate the presence of various ions?
Unlike the very porous membranes of capillaries, plasma membranes of cells often use active transport mechanisms to regulate the presence of various ions.
The concentration of potassium ions (K+) is typically many times higher in cytoplasm compared to tissue fluid. Conversely, the concentration of sodium ions (Na+) is many times higher in the tissue fluid compared to cytoplasm. The cell must use adenosine triphosphate (ATP) in active transport mechanisms to keep the high concentrations of these and other ions more concentrated on one side of the plasma membrane.
lymphatic capillaries
Some of the tissue fluid does not re-enter the venous side of the capillary bed but does enter into small tubes called lymphatic capillaries. The small lymphatic capillaries are very thin walled and contain gaps between adjoining cells to facilitate easy movement of water and solutes. Fluid that enters lymphatic capillaries is called lymph. The collection of tissue fluid in lymph vessels prevents fluid build-up around body cells.
lymph vessels and their similarities to veins
Lymph vessels are similar to veins in that they have internal valves to keep fluid moving in one direction. Like veins they rely on skeletal muscle contractions to squeeze the vessels and one-way valves to keep the lymph fluid moving. Also like veins, lymph vessels join together into larger and larger lymph ducts, eventually taking lymph fluid back to veins so that it can become part of blood plasma once again.
lymph nodes
Fluid entering small lymphatic vessels is often routed through structures called lymph nodes before returning to a vein. Lymph nodes filter bacteria, viruses and sometimes even cancer cells out of the lymph fluid and are considered to be part of the immune system.
single circulation of bony fish
A circulatory system where blood passes through the heart once per circuit. The heart pumps deoxygenated blood to the gills for oxygenation, and the oxygenated blood flows directly to the rest of the body before returning to the heart. This creates a single, continuous loop.
The circulation pattern of fish is simple but limiting.
* Fish have a two-chambered heart, one chamber to receive blood and another chamber to pump the blood out.
* When blood is pumped out it is sent to the gills for oxygen and carbon dioxide exchange.
* The reoxygenated blood is collected from the gill capillaries and sent to capillary beds in body tissues.
* The deoxygenated blood is then returned to the heart to be pumped to the gills once again.
* The limitation of this circulatory pattern is the loss of blood pressure when the blood is within the capillaries of the gills.
double circulation of mammals
Mammals use a double circulation pattern via a heart that has four chambers.
* One side of the heart is used to pump the blood to capillaries in the lungs for reoxygenation. This is called the pulmonary circulation.
* The blood is returned to the other side of the heart to be pumped out to capillaries in body tissues, to supply the oxygen to where it is needed. This is called the systemic circulation.
The additional trip to the heart allows the blood pressure to be restored.
Advantage of the double circulation of mammals
The advantage of this double-sided pattern is that both lung and body capillaries can receive blood from arteries and arterioles. This allows pressure filtration to occur in all capillaries.
anatomy of the four chambered mammalian heart
use diagrams from the textbook to study
the human heart
The human heart is a double-sided pump, with the right side involved with pulmonary circulation (to and from the lungs) and the left side the systemic circulation (to and from the body tissues). The heart has a variety of adaptations to ensure that both atria contract simultaneously, followed by both ventricles contracting simultaneously. In addition there are four heart valves to make sure that there is only a one-way flow of the blood.
just list them
adaptations of the human heart for efficient blood flow
- Cardiac muscle
- A pacemaker (a.k.a the sinoatrial node or SA node)
- Atria
- Ventricles
- Atrioventricular valves
- Semilunar valves
- Septum
- Coronary vessels
cardiac muscle
a highly vascular tissue making up the heart muscle. It’s especially thick in the ventricles of the heart. The muscle making up the wall of the left ventricle is the thickest, as it pumps blood out to locations in the entire body.
a pacemaker (sinotrial node / SA node)
The SA node is a group of modified cardial muscle cells (or specialised cells) located in the thin wall of the rigth atrium.
Cardiac muscle is capable of spontaneous contractions without stimulation from the nervous system, but it is not able to control the timing of the contractions. The SA node or “pacemaker” provides an electrical stimulation to regulate the contractions and is capable of generating electrical impulses at a regular frequency.
e.g. If your myogenic or resting heart rate is 72 beats min’, your SA node is generating an electrical impulse every 0.8 second.
The action potentials from the SA node spread out almost instantaneously and result in the thin-walled atria undergoing systole. The SA node action potential also reaches a group of cells known as the atrioventricular (AV) node.
atria
thin muscular chambers of the heart designed to receive low pressure blood from the capillaries of the lungs or body tissues by way of large veins entering the heart. The atria send blood to the ventricles.
ventricles
thick muscular chambers that pump blood out under pressure to the lungs or body tissues.
antrioventricular valves
valves located between the atria and ventricles that close each heart cycle to prevent any backflow of blood into the atria.
semilunar valves
valves that close after the surge of blood into the pulmonary artery or aorta, to prevent backflow of blood into the ventricles.
septum
a wall of muscular and fibrous tissue that separates the right side of the heart from the left side.
coronary vessels
blood vessels that provide oxygenated blood to the heart muscle.
the cardiac cycle
The cardiac cycle is a series of events that is commonly referred to as one heartbeat.
The frequency of the cardiac cycle is your heart rate, and is typically measured in beats per minute. If you have a resting heart rate of 72 beats min’, you are performing 72 cardiac cycles each minute.
systole
when a chamber of the heart contracts there is an increase in pressure on the blood within the chamber, and the blood leaves the chamber through any available opening.
both atria undergo systole (or, in other words, contract) at the same time. both ventricles also undergo systole simultaneously, just a fraction of a second after atrial systole.
diastole
when a chamber is not undergoing systole, the cardiac muslce of the chamber is relaxed.
atrioventricular node (AV node)
This node is also located in the right atrium, in the septum between the right and left atria.
The AV node receives the impulse coming from the SA node and delays for approximately 0.1 second. The AV node then sends out its own action potentials that spread out to both ventricles.
In order to get the action potentials to reach all of the muscle cells in the ventricles efficiently, since the walls of the ventricles have much thicker muscle tissue than the walls of the atria, there is a system of conducting fibres that begin at the AV node and then travel down the septum between the two ventricles. At various points these conducting fibres have branches that spread out into the thick cardiac muscle tissue of the ventricles. Reception of this impulse results in both ventricles undergoing systole simultaneously.
electrocardiogram (ECG)
An electrocardiogram (ECG) is a graph plotted in real time, with electrical activity (from the SA and AV nodes) plotted on the y-axis and time on the x-axis. Electrical leads are placed in a variety of places on the skin in order to measure the small voltage given off by these two nodes of the heart. Every repeating pattern on an ECG is a representation of one cardiac cycle.
How to read a ECG trace
- P wave: this part shows the voltage given off by the SA node, thus it marks atrial systole.
- Point Q: this is the point at which the AV node sends its impulse.
- QRS complex: this is where the impulse from the AV node spreads down the conducting fibres in the septum between the ventricles and out to the cardiac muscle of the ventricles. This is known as ventricular systole.
- T wave: the AV node is repolarizing in preparation to send the next set of electrical signals.
deciduous
(of a tree or shrub) shedding its leaves annually.
How can plants move water into and up the xylem without the use of negative tension provided by transpiration?
refers to when leaves on deciduous plants have not yet grown (springtime) or when leaves are present but transpiration is not possible (highly humid conditions)
Root cells can create a low water potential by the active transport or diffusion of mineral ions into cells. Water will then follow by osmosis. Root hairs growing from even the smallest branches of a root system will take in water by osmosis in this manner.
The mineral ions can then diffuse or be actively transported across the epidermis and cortex of the root until the minerals reach the xylem tubes in the centre of the root. Specifically, the epidermis, cortex and then into the xylem in the central part of the root.
Some mineral ions can be selectively moved cell by cell by active transport. Water will always follow these solutes by osmosis, as the presence of mineral ions creates an area of low water potential. This will not only allow the water to enter the xylem but also create a positive fluid pressure pushing the column of water upwards.
phloem
Phloem is the vascular tissue in plants that transports sap, a fluid rich in sugars (mainly sucrose) and other organic nutrients, from parts that produce or store them (called sources, like leaves) to parts that need or store them (called sinks, like roots, fruits, or growing tissues). This movement is called translocation.
what is the direction of movement in the phloem based on?
The direction of movement is based on a single principle: the movement from a source to a sink.
* A source is a plant organ that is a net producer of sugar, either by photosynthesis or by the hydrolysis of stored starch. Leaves are the primary sugar sources as they are responsible for photosynthesis.
* A sink is a plant organ that uses or stores sugar. Roots, buds, stems, seeds and fruits are all sugar sinks.
It is possible for some structures to be both a source and a sink. For example, a root structure can store sugar or break down starch to provide sugar, depending on the season: root storage structures such as potatoes act as sinks in the summer and as sources in the early spring.
cellular structure of phloem
The cellular structure of phloem is based on two types of cells that pair together into a functional unit and ultimately create a tube-like vascular network throughout the plant.
1. phloem sieve tubes
2. companion cells.
sieve tube elements
Individual phloem sieve tube cells are connected to one another by porous sieve plates to form sieve tube elements. Sieve tube elements do not contain a nucleus and many other important cell organelles, because they are designed to be nearly empty in order to serve their function as vessels carrying a fluid.
The sieve tube elements cannot remain alive without the numerous metabolic activities of the companion cells.
companion cells
Specialized living cells in the phloem that support sieve tube elements by providing metabolic functions, proteins, and ATP. They are connected to sieve tube elements by plasmodesmata, allowing the exchange of substances.
plasmodesmata
Companion cells and sieve tube elements have multiple connections called plasmodesmata. These allow the cytoplasm of the tube cells to be shared and are the origin of the proteins and ATP needed by the highly specialized sieve tube elements.
how does sap travel through the phloem?
Sap does not travel through the cytoplasm of either phloem sieve tube cells or companion cells, but through the tube-like area of the sieve tube elements, where the plasma membrane and cytoplasm are greatly reduced.
translocation
The movement of sap within the sieve tube elements. it occurs because a water pressure is created at the source.
* The pressure begins at any portion of the plant that has sugars (such as sucrose) that need to be transported elsewhere.
* Companion cells in the source actively transport sugar molecules in, and the sugars pass through the plasmodesmata into the sieve tube elements in that area.
* The movement of sugars into an area of sieve tube elements creates an area of low water potential because of the high number of solutes.
* A nearby xylem vessel will release water into the sieve tube element, as water will move from an area of high water potential (xylem) to low water potential (phloem) by osmosis.
* The influx of water into the sieve tube elements results in the cells expanding outwards because of the increased pressure. Because of this pressure the water, now rich in sugars, will begin moving through the sieve plates within the tube created by the sieve tube elements.
* The water will go to wherever along the tube there is the lowest pressure. That area will be wherever sugars are being downloaded out of the sieve tube elements, into companion cells and then into an area where the sugar is needed for energy or storage.
* In the area of the sink, because solutes are being removed, water will return to a xylem vessel by osmosis.
