Biology SAC 2

systems

Vascular Plants

• Groups of plants that contains vascular tissues (Xylem and Phloem)

• Having specialised systems that transports materials into, around and out of the plants

Xylem role and structure

• Xylem transports water and minerals from a plants roots to its leaves (one direction)

• Contains Xylem vessels and parenchyma cells

• Parenchyma cells contains a nucleus and controls the lignified xylem vessels

Movement in the Xylem

• Transpiration (passive process) is involved in the movement of water and minerals up the xylem due to negative pressure, and the evaporation of water from leaves via the stomata.

Transpiration process

• Osmosis- water enters root cells via osmosis (down concentration gradient) and enters xylem vessels

• Adhesion- attraction between water molecules and walls of xylem vessels, helping pull water upwards

• Cohesion- attraction between water molecules, helping pull water upwards

• Transpiration- evaporation of water via stomata

Phloem role and structure

• Transports sugars and other nutrients to all the cells of the plant (two directional)

• sieve cells are living hollow tubes that contains sieve plates, allowing water to pass through

• companion cells ensures sieve cells remain alive and regulates entry into the phloem.

Movement in Phloem

Translocation (active and passive process) that moves sugars and other substances from a source to other tissues within the plant.

Translocation process

• 1- Sucrose is produced in the leaf cell, pumped into the companion cell, then diffuses into the sieve cells.

• 2- Increased concentration in the sieve cells causing water to diffuse into the Xylem.

• 3- Increase in turgor pressure pushes substances into the phloem, where sucrose is transported into required cells

• 4- Once sucrose is unloaded, the concentration inside the phloem is reduced, and water is diffused back into the Xylem

Environmental conditions that effects transpiration rate

• Temperature- Increase

• Light- Increase

• Humidity- decrease

• Wind- Increase

• Water availability- Increase

Stomata and guard cells

• Guard cells regulates the opening and closing of the stomata

• Stomata allows for gas exchange with the environment (CO2, O2, H2O)

  When the Stomata is open, water vapour and gases can freely enter and exit, while if the stomata is closed transpiration, photosynthesis, and water loss is reduced

• Stomata open when guard cells are turgid, closed when flaccid

Digestion

The process of breaking down a substance into its basic components, so that it can cross the plasma membrane and be used by the body

Types of nutrients in Digestion

• Carbohydrates - provides a source of immediate energy

• Lipids (fats) - energy storage

• Proteins - Structural components of cells, cell receptors and enzymes

• Vitamins - required in small amounts, used to make enzymes

• Minerals - required in small amounts, used in many structural components of organisms

Types of Digestion

• Physical/mechanical digestion - mechanical movement of breaking down food into smaller pieces to increase its SA:V. Mechanical movement involves chewing, peristalsis, stirring of food and digestive juices by muscle movements

• Chemical digestion - breakdown of food into smaller molecules by digestive enzymes and stomach acid, so that they can be absorbed. Occurs by enzymes splitting food molecules in hydrolysis reactions by adding water molecules

Three major digestive enzymes

• Amylases - acts on carbohydrates

• Proteases - breaks down proteins

• Lipases - breaks down lipids/ fats

Process of digestion

• Ingestion - Food is taken into the body, teeth physically breaks down food, while enzymes in saliva chemically breaks down food into soft mass

• Digestion - Occurs along the digestive tract, soft mass travels further into the body - physical and chemical breakdown continues by various organs

• Absorption - once food macromolecules are broken down further, absorption across the plasma of digestive tract cells into the bloodstream occurs, energy available to use

• Elimination/Egestion - elimination of undigested food content -feaces

Organs of the digestive system

• Stomach - mechanical churning and digestive juices break down food. made up of enzymes - proteases and stomach acid

• Liver - Bile production, toxin removal, processing nutrients and stores excess glucose and glucagon

• Pancreas - Produces digestive enzymes, regulates blood sugar levels, and secretes bicarbonate to neutralize acids in chyme

• Small intestine - continued mixing, addition of enzymes, absorption of nutrients

• Large intestine - Absorption of water vitamins and minerals

Nutrient absorption in the small intestine

In the small intestine, Villi and Microvilli increases the SA:V of the intestinal cells, maximising absorption

Excretory system

Removes excess and unwanted substances from the body -waste, while maintaining a stable internal environment through the regulation of water and ion concentrations

The Urinary tract

• Kidneys - filters waste from the blood and produces urine

• Ureter - carries the urine to the bladder, storing it until it is ready to be released by the Urethra

• Urea - Is the main waste product produced and removed via the urinary tract, produced when proteins are broken down

  Kidneys - Ureter - Bladder- Urethra - Urea

Nephron

The functional unit of the kidneys, and create a large surface area to filter blood, reabsorb substances and secretes wastes.

Nephron structure

• Glomerulus - capillaries that delivers blood to the Bowmans capsule

• Bowmans capsule - (filtration) collects filtered blood from the Glomerulus

• Proximal convoluted tubule - (reabsorption) reabsorbs water via osmosis, ions, amino acids and glucose, while secreting ammonia and toxins.

• Loop of Henle - (reabsorption) recovering water and salts from filtrate

• Distal convoluted tubule - (reabsorption) optionally reabsorbs water, ions, while secreting ions and toxins

• Collecting duct - (reabsorption and secretion) taking final filtrate -urine- towards the bladder

Water balance

• Drinking lots of water - causes distal tubule and collecting duct to not reabsorb, resulting in diluted water

• Not drinking much water - distal tubule and collecting duct absorbs more, resulting in more concentrated urine

Endocrine system

Is a collection of glands responsible for producing hormones. Hormones are transported to a receptor of the target cell that responds to the signal

Hormone

Is a signalling molecule released from the endocrine glands, regulating the growth and activity of a target cell

Role of pancreas in endocrine system

• Pancreas - regulates blood sugar levels, by releasing hormones such as insulin (decreases glucose levels) and glucagon (increases glucose levels)

Homeostasis

Maintains the internal environment of an organism within set limits, so that cells and systems can function properly

Set points - Internal T, Blood S, Sodium and potassium C, blood PH

• Internal temperature - 36.5- 37.5

• Blood sugar - 4.0- 7.8 mmol/L

• Sodium concentration - 135-145 mmol/L

• Potassium concentrations - 3.5 - 5.0 mmol/L

• Blood PH - 7.35 - 7.45

• Fluid balance

Stimulus response model

1. Stimulus - Change in external or internal environment

2. Receptor - Stimulus detected by receptor in body

3. Modulator - Information from receptors sent to modulator

4. Effector - Is a molecule (usually a hormone), cell or organ that responds to a signal from the modulator and produces a response

5. Response - any change in the function of a target cell, cell, organ or organism)

Types of receptors (5)

• Thermo receptors - Detects changes in temperature

• Noci receptors - Detects painful stimuli

• Baroreceptors - Detects changes in pressure

• Chemo receptors - Detects changes in chemical concentrations

• Photoreceptors - Detects changes in light

Positive feedback systems

• Occurs when the response increases the initial stimulus (rare in the body)

Negative feedback loop

• Occurs when the response counters the stimulus (response attempts to revert the system back to its set point)

Cellular signalling

• Reception - Detection of a stimulus and transmitting it into a mechanical, electrical, or chemical signal.

• Transduction - Transmission of a cellular signal: sending a signal between organisms, across the body, to a neighbouring cell, or back to the original receptor cell.

• Response - Change in the function of a target cell, organ or organism.

Methods of heat transfer

• Conduction - Transfer of heat through physical contact with another object

• Convection - Transfer of heat via the movement of liquid or gas between areas of a different temperature

• Evaporation - loss of heat via the conversion of water from liquid to gas form

• Radiation - Transfer of heat via waves of light (does not require physical contact)

Thermoregulation

• Homeostatic process of maintaining a constant internal body temperature, the hypothalamus receives information detected by thermo receptors and regulates the bodies temperature (body thermostat)

Bodies reaction to increase in temperature

• Sweat glands - sweating

• Blood vessels - vasodilation

• Cerebral cortex - changes in behvaiour

• Arrector pili - flattening of hair

• Cells - decrease in metabolic rate

Bodies reaction to decrease in temperature

• Skeletal muscles - shivering

• Blood vessels - vasoconstriction

• Cerebral cortex - changes in behaviour

• Arrector Pili - Lifting of hair

• Cells - Increase in metabolic rate

• Brown fat - Burning of triglycerides (fat/lipids)

Regulation of blood glucose

• Glucose in the human body must be maintained within a narrow range in order for the body to function correctly.

• Blood glucose is maintained via negative feedback loops, involves pancreas releasing hormones (insulin and glucagon) to regulate blood sugar

Glycogen

• Branched Polysaccharide

• Stored form of glucose primarily found in the liver and muscles, serving as a reserve energy source that can be converted back into glucose when needed.

Stimulus response model - glucose too high (hyperglycaemia)

1. Stimulus - Increase in blood glucose levels

2. Receptor - Beta cells of the pancreas

3. Modulator - Insulin: sensitive cells of the hypothalamus, and beta cells of the pancreas secrete hormone insulin

4. Effector - Liver and body cells

5. Response - Decrease in blood glucose by: uptake by liver cells, conversion to glycogen and uptake by body cells

Stimulus response model - glucose too low (hypoglycaemia)

1. Stimulus - Decrease in blood sugar levels

2. Receptor - Alpha cells of the pancreas

3. Modulator - Alpha cells of the pancreas secrete the hormone glucagon

4. Effector - Liver and body cells

5. Response - liver cells release glucagon from glycogen, and other cells make glucose (gluconeogenesis)

Functions of water in the processes of the body

• production of urine

• removal of water (waste) heat via evaporation

• maintenance of blood pressure

• protection of brain and central nervous systems through cerebrospinal fluid

total water change

= water in + metabolic water - water out

stimulus response model - regulation of water balance

• Stimulus - change in water volume

• Receptor - baroreceptors and osmoreceptors

• Modulator - cells in kidneys, hypothalamus and pituitary gland

• Effector - cells in distal convoluted tubule, collecting duct and hypothalamus

• Response - realteration in the reabsorption of water, leading to changes in blood pressure and volume.

ADH (antidiuretic hormone) pathway - decrease in water levels

Occurs when increase in osmolality of the blood, and decrease in blood pressure and volume

ADH primary effects

• increases water reabsorption in the nephron of kidneys, by increasing number of aqauporins in the cells of distal convoluted tubule and collecting duct. Reducing urine output.

• ADH travels to thirst centre in hypothalamus, generating feeling of thirst.

Secretion of renin - decrease in water levels

Decrease in blood pressure and volume detected by Baroreceptors in the heart, neck and kidneys, causing:

• Baroreceptors send signals to hypothalamus, contributing to the release of ADH form the posterior pituitary gland.

• Baroreceptors trigger release of renin from kidneys, causing release of aldosterone from adrenal glands. Aldosterone activates sodium potassium pumps in cells lining of distal convoluted tubule and collecting duct. Increasing amount of sodium absorbed in these areas, and amount of potassium excreted in urine.

Stimulus response model - ADH pathway and renin systems

• Stimulus - decrease in water levels

• Receptor - Baroreceptors and Osmoreceptors

• Modulator - Release of renin in kidneys causing release of aldosterone. Hypothalamus releasing ADH from posterior pituitary gland.

• Effector - Activation of sodium potassium pumps. Aquaporins inserted in kidneys, stimulation of cells in thirst centre

• Response - increased reabsorption of water in kidneys, and water uptake.

Increase in water levels

• Causes decrease in osmolality of the blood and increase in blood pressure and volume.

• Thirst centre in hypothalamus suppressed

Stimulus response model- increase in water levels

• Stimulus - Increase in water levels

• Receptors - Baroreceptors and osmoreceptors

• Modulator - Hypothalamus suppresses release of ADH from posterior pituitary gland

• Effector - Decrease insertion of aquaporins, thirst centre suppressed.

• Response - decreased reabsorption of water in kidneys, decrease water consumption.