Biololgy Communication and Homeostasis.
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- Created by: Phil
- Created on: 06-04-13 13:28
Define Homeostatis.
The maintenance of the internal environment in a "constant" state despite changed in the environment.
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What is meant by cell singalling?
The method by which a cell communicates with another by releasing a chem that is detected by another that leads to a response.
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4 Conditions required for enzymes to work efficiently?
Suitable pH, suitable temp, an aqueous environment that keeps the substrates and products in the solution, freedom from toxins and inhibitors.
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What are the two major systmes that work by Cell signalling ?
The hormonal system and the neuronal system?
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How does the neuronal system work?
Uses an interconnected network of neurones that signal to each other across synapse junstions. Very quick response to stimuli that may be changing quickly.
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How does the hormonal system work?
Hormone is secreted into the blood by an endocrine gland.It is carried all over the body but only recognised by specefic target cells. Long term response.
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What is negative feedback?
A process that brings about a reversal of any change in conditions. It ensures that an optimum state can be maintained.
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3 structures for negative feedback to work and what do they do?
Sensory receptors such as temp receports, if they detect a change they send a message. A Communication sys such as hormonal sys, used to tramsit a message from receptor cells to effector cells.Effector cells such as muscle cells,Bring about a respons
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What is positive feedback?
A process that increases any change detected by the receptors, tends to be harmful and not lead to homeostasis.
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Example of positive feedback involving enzymes?
If temp too low enzymes become less active meaning exoergonic reactions that release heat release less heat so the body becomes cooler again.
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Non-harmful eg of postive feedback?
When cervix starts to stretch the hormone Oxytocin is released which increases contractions and therefore stretch the cervix more which therefore releases more oxytokin etc.
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What is an ectotherm?
An organism that relies on external sources of heat to regulate it's body temp and is not able to increase respiration to generate heat internally. Thereforce body temp tends to fluctuate with extermal temp.
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What is an endotherm?
An organism that can use internal source of heat such as heat generated from metabolism in the liver, to maintain it;s body temp within fairly strict limits. They are largely independent of external temp.
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Why is core temp important?
All vital organs are found within the main part of the body.
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3 Advantages of being an extotherm?
Less food udes in respiration. Need to find less food and may be able to survive longer without eating. A greater proportion of energy gained from food can be used for growth.
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2 Disadvantages to being an ectotherm?
Less active in cooler periods, may need to warm up in the morning before doing anything which makes them at a greater risk of predation. They may not be capable of activity during winters, so they must have sufficient stores of energy.
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When an ectotherm is cold it will...
Change it's behaviour or physiology to increase heat absorption and .
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Examples of ways in which ectotherms regulate body temp (behaivoral)?
Orientate body to/away from sun (exposes larger/lower SA to sun). Hide in burrows.
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Example of an anatomical way an ectotherm can regulate temperature?
By altering it's body shape, exposing more or less SA to the sun.
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A Physiological way in which ectotherms can reg temp?
Increasing breathing movements, thus more water is evaporated and more heat it lost.
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3 Advantages of being an endotherm?
Fairly constant body temp regardless of external temp, can be active during cooler temps, can inhabit cooler locations.
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3 Disadvantages to being an endotherm?
More food required to survive, More energy used to maintain body temp, Less energy used for growth.
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3 behavioural mechanisms to maintain body temp if too hot in endotherms.
Move into shade/ hide in burrow, orientate body to decrease SA exposed to sun, Remain inactive and spread out limbs to inc SA.
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3 behavioural mechanisms to maintain body temp if too cold in endotherms?
Move inot sunlight, Orientate body to increase SA exposed to sun, Move about to generate heat in muscles.
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In extreme cold, how does an ectotherm's behavious change?
Keep still and roll into a ball to decrease SA.
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6 physiological components in endotherms that regulate temp?
1. Sweat glands in skin. 2. Lungs, mouth and nose, 3.Hairs on skin 4. Arterioles leading to cappilleries in skin. 5. Liver cells. 6. Skeletal muscles.
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How do sweat glands help reg temp in endotherms?
If too hot, secrete more sweat, water in sweat evaporates using heat from blood to supply latent heat of vaporisation.. If too cold, Less sweat is secreted, less evap of water so less loss of latent heat.
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How do the lungs, mouth and nose help reg temp in endotherms?
If too hot, panting increases evap of water from lungs, tongue and other moist surfaces, using latent heat. If too cold, animal does not pant so less latent heat is lost through evap.
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How do hairs on the skin help reg temp in endotherms?
If too hot, hairs lie flat, providing little insulation so more heat lost by convection and radiation. If too cold, hairs raise up providing insulation and prevent loss of heat via radiation and convection.
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How do the arterioles leading to capilleries in the skin help reg temp in endotherms?
If too hot, Vasodilation occurs, allowing more blood into cappilleries of skin surface and more heat can be radiated from the skin. If too cold vasoconstriction occurs, reducing ammount of blood in cappilleries near the surface of the skin reducing r
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How do liver cells in endotherms help reg temp?
If too hot, rate of metabolism is reduced so less heat is generated from exergonic reactions such as resp. If too cold opposite.
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How do skeletal muscles in endotherms help reg temp?
If too hot no spontateous contractions, if too cold, spontanuous contractions occur to generate more heat as it causes muscles to respire more.
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What is the optimum core tmep of an endotherm?
37C
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Where is temp regulated in endotherms?
In the thermoregulatory centre in the hypothalamus.
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How does the thermoregulatory centre react if there is a rise in core temp (3 stages).
1. detects change, 2.Nervouse sys and hormonal sys carry signals to the skin liver and muscles. 3. Less heat is generated and more heat is lot. Resulting in temp decreasing.
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How does the thermoreg centre react if there is a fall in core temp?
1. Thermo reg centre detects change in temp. 2. Nervous and hormonal systems carry signals to the skin liver and musicles. 3. More heat is generated and less heat is lost. Resulting in an increase in temp.
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How the thermo-regulatory centre reacts to changes in core body temp is an example of...?
Negative feedback.
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Sensory receptors are energy ....?
Transducers, they can convert one type of energy into another.
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Diagram : Neurones...... pg 13
k.
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What is resting potential?
-60mV
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How does the sodium/potassium ion pump work at resting potential?
3 na+ are actively transported out, 2 K+ are actively transported in. Continuously working.
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When is the cell membrane polarised?
When it is at restin potenital.
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What is threshold potential and what happens if it is reached?
Around -50mV, if it is reached, an action potenital is generated,
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What is depolorisation?
The loss of polarisation across the membrane, it occurs when sodium ions enter the cell.
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What is repolarisation and when does it occur?
When the pd across the membrane is brought back to a negative value, occurs after an ap is generated and K+ channels open.
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What is hyperpolarisation and when does it occur?
When the pd is slightly less than what it is at resting potential (~-70mV), occurs after repolarisation.
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What is the refactory period and what is the importance of it?
During r period it is impossible to generate another ap, it occurs during hyperpolarisation and it allows the cell to recover after an ap and ensures that ap's are only transmitted in 1 direction.
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Process of generated an ap (8)
1)Stimulus 2)Na+ channels open, diffuse in. 3)Threshold 4)VG Na+ open. 5)AP gen 6)Na+ close, K+open7)K+ slow to close (rperiod)9) resting period.
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How are local current created and what do they cause?
Created by Na+ channels opening when an ap occurs. They cause Na+ channels further along the membrane to open.
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Process: how local currents are created in depth.
hg
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What is the myelin sheath and what does it doe.
It is an insultaing layer of fatty material that surrounds the cell. It provide protection from damage, electrical insulation and speeds up transmission.
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What is conduction on myelinated neruones called and how does it occur?
Saltatory conduction, occurs in between gaps in the sheath called node of Ranvier.
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What is a synapse and what is a synaptic cleft?
Synapse is a junction between two of more neurones and a synaptic cleft is the gap between the neurones.
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How does an ap get across the synaptic cleft?
It doesn't, instead it causes a chemical to be produced which diffuses across and causes a new ap to be generated on the postsynaptic neurone.
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What is the synaptic knob?
A swelling at the end of the presynaptic neurone.
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What 4 specialised features does the syn knob contain?
Many mitochondira, a large amount of SER, Vesicles containing acetylcholine, Voltage gated calcium ion channels.
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Process-Transmission across the membrane.
fdh
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Name the enzyme in the synaptic cleft ans state it's purpose.
Acetylcholinesterase, it breaks down acetylcholine to prevent it from generating more ap.
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What are hormones?
Molecules that are released by endocrine glands directly into the bloodsteam. They act as messengers carrying a signal from the endocrine gland to a specific target organ or tissue.
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What is an endocrine gland?
A DUCTLESS gland that secretes hormones directly into blood.
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What is an exocrine gland?
A gland that secretes molecules into a duct that carries the molecules to where they are used. Do not release hormones.
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Example of exo gland?
Salivary glands, secrete saliva into duct that flows into the mouth.
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What do target cells contain? What are a graoup of target cells called?
Specific complementary receptors on their plasma membrane, in which the hormone binds to. Target Tissues.
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What are the two types of hormone? examples?
Protein and peptide hormones eg. adrenaline, insulin and glucagon. And steroid hormones eg sex hormones.
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What is the main difference between the two types of hormones?
Protein hormones are not soulble in the phospholipid bilayer so cannot enter the cell, steroids however can pass through the membrane.
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How does a protein hormone work?
The hormone binds to the receptor which causes ATP to be converted to cAMP inside the cell. cAMP can then bind to an inactive enzyme inside the cell to bring about a response.
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How does a steroid hormone work?
Passes through the bilayer and binds to a receptor inside the cytoplasm. This causes a gene to be activate in the nucleus. This gene is then transcribed and translated into a protein that brings about a response.
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Diagrams (steroid/protein hormones and adrenaline).
rdegf
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What is the enzyme associated with adrenaline called and where is it located?
Adenyl cyclase. Located on the inside of the CSM
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How does adrenaline work?
Binds to receptor, which activates Adenyl cyclase, which converts ATP to cAMP which activates the enzyme to bring about the response.
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Define "First messenger". Give an example.
The fm is always the hormone that transmits the signal around the body. eg Adrenaline.
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Define "second messenger". Give an example.
The molecule that causes an effect inside the cell. eg cAMP.
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Where are the adrenal glands found and how can the gland be divided up?
Found just above the kidneys (one on either side of the body. Can be divided into a medulla region and a cortex region.
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What do cells in the adrenal medulla do?
Manufacture and release adrenaline in response to stress.
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What do cells in the adrenal cortex do?
Use cholesterol to produce certain steroid hormones.
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Two types of hormones produced by cortex and their roles?
Mineralocorticoids, help control conc of sodium and potasium in blood. Glucocorticoids, help to control the metabolism of carbohydrates and proteins in the liver.
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Where is the pancreas found and why is it an unusual organ?
Just below stomach. Unusual bc is had bothe endo and exo glands.
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Diagram : Pancreas.
gfg
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What is the exo function of the pancreas, and where are the cells found?
To manufacture and release digestive enzymes. They are found next to tiny tubules in which they release the enzymes into.
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What is the duct called that carries the product of the exo glands in the pancreas, how is it formed and where does it lead?
Pancreatic duct, formed by the joining of the tubules surrounding the exocrine cells. It leads to the small intenstine.
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What is the product of exo glands and what does it contain?
Pancreatic juice. Contains amylase (a carbohydrase), Trypsinogen (an inactive protease), Lipase and sodium hydrogen carbonate (helps neutralise acidic chyme.
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What is the endo function of the pancreas and where are the endo cells found?
To regulate blood glucose levels. The cells (alpha and beta) are found on the islets of Langerhans.
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If blood gluc levels too high, what is this detected by and what is the response, and what are the target cells to this response?
Detected by beta cells on the islets of Langerhans. Beta secrete insulin, target cells hepatocytes and muscle cells, among others.
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If blood gluc levels too low, what is this detected by and what is the response, and what are the target cells to this response?
Detected by alpha cells on islets of Langerhans. Alpha secrete Glucagon, target cells hepatocytes.
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What 5 effects do insulin have on cells
1. Increased number o glucose channels in CSM. 2.More glucose enter cells. 3. Glycogenesis. 4. More glucose converted to fats. 5. More glucose used in resp.
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Define Glycogenesis.
Conversion of glucose to glycogen for storage.
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What are the 3 source of blood glucose?
Diet, Glycogenolysis, Gluconeogenesis.
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Define glycogenolysis.
Breakdown of glycogen.
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Define Gluconeogenesis.
Production of glucose by conversion of amino acids and fats.
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What 3 processes occur in response to glucogon.
1.Glycogenolysis, 2. More fatty acids used in rep 3. Gluconeogenesis.
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What 2 processes does adrenaline cause to happen in relation to glucose levels?
Glycogenesis, if no glycogen is available then cortex releases cortisol which causes gluconeogenesis.
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At rest, pd of beta csm is...?
-70mV.
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How does an increase in glucose levels outsie the beta cell, lead to the pd inside the cell increasing?
More glucose outside=more glucose move into cell=more glucose metabolised to make ATP. Increased ATP cause K+ ions to close, thus increasing pd.
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How does an increase in pd cause the secretion of insulin in beta cells?
Increased pd causes calcium ions channels to open and caclium ions move into cell. The ions cause the vesicles containing insulin to move to csm and fuse with it, releasing insulin by exocytosis.
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What is the enzyme inside of Beta cells and what does it do?
Glucokinase, catalyses the reaction that results in glucose being metabolysed into ATP.
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What is Diabetes Mellitus?
A disease in which blood glucose levels cannot be controlled efficiently.
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What is Hyperglycaemia? What is the opposite?
A state in which glucose levels are too high. Hypoglycaemia.
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What is type I diabetes?
Where the body is no longer able to produce sufficient inuslin and cannot store excess glucose as glycogen.
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What is thought to be the cause of type I diabetes?
An autoimmune response wherre the immune sys attacks beta cells and destorys them.
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What is type II diabetes?
Can still produce insulin but there ability to respond to insulin has declined. Levels produce may also decline.
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Factors that increase the risk of type II diabetes?
Obesity, a diet high in sugars (refined), being asian/ afro-caribbean, family history.
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How is type II diabetes treated?
Control of diet. Match carbohydrate intake and use. Drugs may also be used to slow down absorption of glucose.
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How is type I diabetes treated?
Insulin injections.
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Advantages to using genetically engineered insulin? (3)
Exact match so less risk of rejection, less moral objection, Lower risk of infection
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Diagram HEART.
dg
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3 ways in which the heart adapts to increase glucose and oxygen levels.
Increase bpm heart rate, increase strength of contractions, increase stroke volume (volume of blood pumped per beat.
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What control hr, where is it found?
Cardiovascular centre, is a region of the medulla oblongata.
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How does movement of lims affect hr and why and how is this change detected?
Increases sue to muscles needing more o2 and glucose for resp. Detected by stretch receptors in msucles.
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How does exercising affect heart rate and why and how is this change detected?
Increases, due to pH levels in the blood plasma reducing due to the increase in co2 which binds with water to produce more H ions. Detected by chemo receptors in carotid arteries,
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How does stopping exercise affect hr, why and what is this change detected by?
Decreases due to less co2 being produced so less co2 binding with water, so less H+ ions, so decrease in pH levels o fblood plasma. Detected bu chemo receptors in carotid arteries.
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How does stress/excitement,shock etc affect hr, why ?
Increases due to the release of adrenaline.
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How does High bp affect hr, what is this detected by?
Decreases, to decrease BP. Detected by strectch receptors in the walls of the carotid sinus.
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Other cards in this set
Card 2
Front
What is meant by cell singalling?
Back
The method by which a cell communicates with another by releasing a chem that is detected by another that leads to a response.
Card 3
Front
4 Conditions required for enzymes to work efficiently?
Back
Card 4
Front
What are the two major systmes that work by Cell signalling ?
Back
Card 5
Front
How does the neuronal system work?
Back
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