Communication and Homeostasis

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Any change in the environment that causes a response
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A change in behaviour or physiology as a result of a change in the environment
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the maintenance of a constant internal environment despite external changes
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Negative Feedback
A process in which any change in a parameter brings about the reversal of that change so that the parameter is kept fairly constant.
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Positive Feedback (and example)
A process in which any change in a parameter brings about an increase in that change. Example: Releasing oxytocin during labour to stimulate a contraction, which then pushes the baby, stimulating this cycle once more
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An organism that relies on external sources of heat to regulate body temperature
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Ectotherm physiological response examples
1. Horned lizard expands its ribcage to increase its surface area 2. locust increases its abdominal breathing movements to increase water loss when hot
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Ectotherm behavioural response examples
1. Snakes expose their bodies to the sun so more heat is absorbed 2. locusts orientate their bodies towards the sun to expose a large surface area
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An organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body temperature
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Endotherm physiological response examples
1. Sweat glands 2. panting to increase water evaporation from lungs, tongue, other moist surfaces 3. hairs on skin when hot they lie flat providing little insulation, and when cold they stand up, insulating the skin
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Endotherm behavioural response examples
1. When hot: move into shade, remain inactive and spread out to increase surface area 2. When cold: move into sunlight, move about to generate heat in muscles
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Receptor for sound
Auditory receptors
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Receptor for temperature
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Receptor for light
Rods and Cones (Photoreceptors)
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Receptor for taste
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Receptor for smell
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Receptor for pressure
Pacinian corpuscles
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Receptor for position
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Name of pumps in neurones and what they do
Sodium- potassium pumps that pump sodium ions out of the cell and potassium ions into the cell
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Motor neurone characteristics
1. A cell body at the end with a large nucleus and lots of rough ER and golgi bodies 2. Many short dendrites that carry impulses to the cell body 3. A long axon which carries an impulse from the cell body to the effector
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Sensory neurone characteristics
1. Long processes on either side of the cell body 2. A dendron carrying nerve impulses from a receptor to the cell body 3. An axon carrying an impulse from the cell body to the central nervous system.
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How is the resting potential established and maintained?
Resting potential: -60mV 1. Sodium-Potassium pumps actively transport 3Na+ ions out and 2 K+ ions in 2. The axon contains organic anions, which the membrane is impermeable to. 3. Membrane is impermeable to Na+ ions
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Occurs when the sodium gated channels open, causing sodium ions to enter, so the inside of the cell becomes less negative
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Threshold Potential
When the membrane depolarises it eventually reaches the threshold potential of -50mV.
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When the cell tries to repolarise too many potassium ions leave the cell, causing it to reach a potential of between -75 and -90, the membrane is hyper polarised.
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What does a synaptic knob contain?
1. Many mitochondria 2. A large amount of smooth ER 3. Vesicles containing acetylcholine 4. Voltage gated sodium ion channels in the membrane
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What does a post synaptic membrane contain?
Specialised sodium ion channels that will only open when acetylcholine binds to them
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Endocrine gland
A gland that secretes hormones directly into the blood, they have no ducts
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Exocrine gland
A gland that secretes hormones directly into a duct that carries the molecules to where they are used
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Target tissue
A group of cells that have receptors embedded in the plasma membrane that are complementary in shape to specific hormone molecules. Only these cells will respond to the specific hormone
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First messenger
The first messenger is the hormone that transmits a message around the body, e.g. adrenaline
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Second messenger
The second messenger, e.g. cAMP transmits a signal inside the cell.
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Two regions of the adrenal glands
The cortex region and the medulla region
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Glucocorticoids (target tissue and role)
Target: Liver, Role: Stimulates synthesis of glycogen
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Mineralalocorticoids (target tissue and role)
Target: Kidney and gut, Role: Increases uptake of Na+ and raises blood pressure
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Adrenaline (target tissue and role)
Target tissues: 1. Heart, where it increases the heart rate 2. Liver, where it stimulates breakdown of glycogen to glucose 3. Smooth muscle, where it inhibited peristalsis
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Alpha cells in islets of Langerhans
Manufacture and secrete glucagon
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Beta cells in islets of Langerhans
Manufacture and secrete insulin
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Exocrine function of pancreas
To manufacture and release digestive enzymes into the pancreatic duct, which goes into the small intestine. Fluid contains: Amylase-a carbohydrate, trypsinogen (an inactive protease), and lipase. Also contains sodium hydrogen carbonate, an alkaline.
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Normal blood glucose concentration
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Effects of insulin inside the cell
More glucose channels placed on cell membrane, more glucose enters cell, glucose converted to glycogen, more glucose converted to fats, more glucose used in respiration
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Effects of glucagon inside the cell
Glycogen converted to glucose, more fatty acids used in respiration, amino acids and fats converted to glucose, more glucose in bloodstream
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Converting glucose to glycogen
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Converting glycogen to glucose
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Converting amino acids and fats to glucose
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Diabetes Mellitus
A disease in which blood glucose levels cannot be controlled effectively. This can lead to very high concentrations of glucose (hyperglycaemia) or very low concentrations of glucose (hypoglycaemia)
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Type 1 diabetes (and type of treatment)
Auto-immune response in which body's beta cells are attacked and insulin cannot be produced Treatment: Injections and blood glucose concentrations are closely monitored
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Type 2 diabetes (and type of treatment)
Body can produce insulin but insulin receptors lose ability to detect and respond to insulin (more common with older people) Treatment: Monitoring and controlling diet and may be supplemented by injections
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Positives in using genetically modified bacteria to treat diabetes
1.Exact copy of human insulin - Faster acting, More effective 2. Less chance of rejection 3. Cheaper 4. More adaptable to demand 5. Less likely to have moral objections.
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What mechanism causes the heart to speed up
Action potentials sent down the Accelerator Nerve to the heart; from the Cardiovascular centre of the medulla oblongata
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Why might the heart rate increase
Movement of limbs detected by stretch receptors in muscles (extra oxygen needed) 2.Drop in pH detected by chemoreceptors in the carotid arteries, the aorta and the brain (exercising produces CO2, this may react w/ H2O in the blood and reduce the pH)
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Card 2




A change in behaviour or physiology as a result of a change in the environment

Card 3




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Card 4


Negative Feedback


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Card 5


Positive Feedback (and example)


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