TEACHER POINTS IN REDUnit 1 F214 Communication, homeostasis and energy

Module1: Communication and homeostasisModule 1 4.1.1 Communication

Module 1 4.1.2 Nerves4.1.3 Hormones

Module 1 4.1.1-4 CommunicationOCR Book pages 4-11

Extension reading: Biological Sciences review articles: Homeostasis May 2000Keywords:

Homeostasis, stimulus, response, receptor, effector, excretion, cell signalling, Neuronal system, hormonal system, hormones, negative feedback, optimum, positive feedback, oxytocin, ectotherm, endotherm, physiological, anatomical, hypothalamus, arterioles.Tasks:

1. By the end of the unit you should have compiled a glossary to include all the key terms above, and any others that help you understand this module.

2. Why do cells need to maintain a certain limited set of conditions inside their cells?Enzymes control cellular activities (temp, pH, stable aqueous environment)

3. Define stimulus and response Stimulus is any change in the environment that causes a response. Response is a change in behaviour or physiology as a result of a change in the environment

4. Complete the word fill exercise on stimulus and response:External environment:

All living organisms have an external environment that consists of the : air, water or soil around them.

This external environment will change, as it changes it may place stress on the living organism. Such as, a cooler environment will cause greater heat loss.

If the organism is to remain active and survive, the changes in the environment must be monitored and the organism must change its behaviour or physiology to reduce the stress.

The environment change is a stimulus and the way in which the organism changes its behaviour or physiology is its response. The environment may change slowly, such as the seasons or Global warming

These changes will elicit a gradual response. However the environment may change more quickly. The change (stimulus) must be monitored and the organism must respond to the change

Internal environment:

Most multicellular organisms have a range of tissues and organs. Many of these are not exposed to the external environment; they are protected by epithelial tissues and organs. (E.g. skin and bark.)

In animals the internal cells and tissues are bathed in tissue fluid, this is the environment of the cells. As cells undergo their various metabolic activities they use up substrates and produce products. Some of these may be unwanted or toxic. These substances diffuse of the cells into the tissue fluid. Therefore, the activities of the cells alter their own environment. One waste product is carbon dioxide. If this is allowed to build up in the tissue fluid outside the cells it could disrupt the action of enzymes by changing the pH of the environment around the cell. Accumulation of waste or toxins in this internal environment must act as stimulus to cause removal of these wastes. This may act directly on the cells which respond by reducing their activities so that less waste is produced. However, this response may not be good for the whole organism.

5. Find 2 examples of a stimulus and response to environmental changes and two for the internal environment. Should have researched own examples here:------------ fur colour…internal loop of Henle etc

6. State the key features of a good communication system. Cover whole organism, allow cells to communicate, specific communication, rapid, short and long term responses.

7. Revise cell signalling from AS and summarise your understanding into 6 bullet points. (page 20-21) Process that leads to communication and coordination between cells, e.g. hormones; binding to their receptors (protein molecules); on the cell surface membrane; the molecule has a complimentary shape to the receptor to trigger a response or reaction inside the cell; it allows for cell recognition and the coordination of the action of different cells. Hormones are chemical messengers; these bind to complementary receptors on target cells; often the hormone is the primary messenger; triggers a reaction inside the cell with a secondary messenger.

8. Give a definition for Homeostasis and list some of the factors that need to be kept constant in the body. Maintenance of a constant internal environment despite external changes: solute levels; blood glucose levels; temperature; carbon dioxide concentrations; blood pressure

9. Define Negative feedback, draw a flow chart to explain and give an example. A process that brings about the reversal of a change to the norm, to ensure optimum conditions can be maintained. (see flow chart page 6)

10. Define positive feedback, draw a flow chart to explain and give an example. A process that increases any change detected. Mainly harmful, homeostatic mechanism gone wrong!

11. EXTENSION: Can you give an example of positive feedback that is not harmful? Opening of Na+ channels after the first stimulation/ depolarisation; a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism. (Others acceptable: look up!!)

12. Give a definition for ectotherm and name 5 examples. An organism that relies on external sources of heat to regulate temperature: Snakes, locusts, Lizards, frogs……

13. Describe the advantages and disadvantages of being an ectotherm. A: use less food in respiration, need to find less food and eat less food’ more energy from food used for growth; D: less active in cool temps, greater risk of predation,must have sufficient energy store to last a winter where they cannot be active (hibernation)

14. Research your own behavioural and physiological adaptations of ectotherms and complete into a table: Do not use the examples from the text book!!YOU JUDGE!

Adaptation How it helps regulate temperature Type of adaptation

Example

15. Give a definition for endotherm and name 5 examples. An organism that can use internal sources of heat, such as that from metabolism in the liver, to maintain its body temperature.

16. Describe the advantages and disadvantages of being an endotherm. Constant body temp with fluctuating ext temp; activity possible when cool; inhabit colder parts of the planet D: significant part of energy intake= maintenance of temp; less energy from food used to grow.

17. Using the figure below: Summary of temperature regulationa) What is the norm value for human body temperature? 37.5 degrees Cb) Using different colours, shade in and label the boxes in Figure 1 that represent the

stimulus receptors, control mechanism, effectors and responses involved in this example of homeostasis.

c) Which response by effectors occurs in humans but produces little effect and is more significant in most other mammals? Hair erector muscles

d) What behavioural changes could a person make to prevent their temperature dropping? Move to warmer place, put on more clothes etc!!

e) Complete the tables To explain the responses if it is too hot or too cold:

If TOO COLD:

Thermoregulation Thermoregulation Thermoregulation Thermoregulation

Receptor Thermo receptors in skin and

hypothalamus

Thermo receptors in skin and

hypothalamus

Thermo receptors in skin and

hypothalamus

Thermo receptors in skin and

hypothalamus

Processing centre

Hypothalamus Hypothalamus Hypothalamus Hypothalamus

Effector Skeletal muscle Liver and muscle tissue

Smooth muscle in skin and blood

vessels

Hair erector muscles muscles

Effect Spontaneous contractions

Rate of metabolism increased: respiration

Vaso constriction: less heat radiated

Contract:trap layer of insulating air

If TOO HOT: Thermoregulation Thermoregulation Thermoregulation ThermoregulationReceptor Thermoreceptors in

skin and hypothalamus

Thermoreceptors in skin and

hypothalamus

Thermoreceptors in skin and

hypothalamus

Thermoreceptors in skin and

hypothalamus

Processing centre

Hypothalamus Hypothalamus Hypothalamus Hypothalamus

Effector Skeletal muscle Liver and muscle tissue

Smooth muscle in skin and blood

vessels

Sweat glands in the skin

Effect No contractions Rate of metabolism reduced

Vasodilation: more hear radiated

Sweat more: latent heat of evaporation.

Summary of temperature regulation

See SNAB teachers sheet attached (at back)

18. Complete review exam question on this attached See MS attached 19. Review the Learning outcomes for Module 1 4.1.1-4 Communication20. Ask for the exam question pack for this module to be e-mailed to you to complete as final

review of this topic.

Module 1.1. 5-9 NervesOCR Book pages 12-21

Extension reading: Biological Sciences review articles: Refractory period April 2008Pacinian corpuscle January 200

Keywords:Sensory receptors, transducers, neurones, sensory neurones, motor neurones, polarised, depolarised,

hyperpolarised, generator potential, resting potential, action potential, voltage gated channels, threshold potential, repolarisation, refractory period, local currents, salutatory conduction, myelin

sheath, nodes of Ranvier, synapse, cholinergic, neurotransmitter, synaptic knob, presynaptic membrane, post synaptic membrane, acetylcholinesterase, exocytosis, synaptic cleft, summation,

temporal summation, spatial summationTasks:

1. By the end of the unit you should have compiled a glossary to include all the key terms above, and any others that help you understand this module.

2. Outline the roles of sensory receptors in mammals in converting different forms of energy into nerve impulses: page 12. a. Complete the table below to show the receptors and the energy changes they detect see

page 12 textbook

Type of receptor Stimulated by Receptor Energy change detected

Chemoreceptor Volatile chemicals

Chemoreceptor Soluble chemicals

Mechanoreceptor Vibrations

Photoreceptor Light

Thermoreceptor Heat/cold

Pressure receptor Pressure on skin

Proprioreceptor Muscle length, and muscle tension,

b. What happens to the stimulus from all these receptors? What word is used to describe this? Transducers: convert one form of energy to another.

3. Describe, with the aid of diagrams, the structure and functions of sensory and motor neurones: page 12-13Neurones are cells specialised to transmit electrical signals of nerve impulses very quickly from one part of the body to another.a. What features of a neurone are typical of Eukaryotic cells? Cytoplasm, nucleus, plasma

membrane, mitochondria, RER SER GAb. What types of neurone are there and what are their functions?c. Draw and label a motor and sensory neurone see page 13d. Describe how a motor neurone and a sensory neurone are adapted to their function:

State the adaptation and describe its function e.g. see page 13Long: to transmit action potential over long distanceGated ion channels in plasma cell surface membrane: Control the movement of ions like Na+ K+

e. Complete the table to compare the structure, location and function of Motor and Sensory neurones:

Motor Sensory

General structure

Cells have cell body, short dendrites and long axon.

Cells have cell body, long dendrites and short axon.

Location of cell body relative to

CNS

Cell body and dendrites inside CNS, axons outside CNS.

Cell body and dendrites outside CNS. Cell body is in dorsal root ganglia at entrance route to the spinal cord.

Dendrites Dendrites synapse with other neurones in CNS.

Dendrites synapse with sensory receptor cells.

Axons Axons synapse with effector cells (muscles and glands).

Axons synapse with other neurones in CNS.

Function Conducts impulses from the CNS to the effector.

Conduct impulse from the receptor to the CNS.

4. Describe and explain how the resting potential is established and maintained: page 14a. SYNOPTIC: remind yourself here of AS: How can molecules move across

membranes? State the processes and the structures involved. Pupil needs to discuss diffusion:/lipid bilayer /channel proteins, facilitated diffusion/ channel/ carrier proteins, active transport/protein pumps, osmosis/ plasma membrane, endo and exocytosis/ plasma membrane.

b. What is the resting potential? Is the pd, voltage across a membrane while neurone is at rest, -60mV inside

c. What is the role of the organic anions inside the neurone? Maintain the –ve voltage.

d. By what processes do the ions move across the membrane in a resting potential? Diffussion of K+, electrochemical gradient K+’ protein channels

e. Explain the changes in the potential difference during the resting potential by producing a flow chart with 10 bullet points. These are the key words that should be used and explained: Resting potential, polarised, sodium-potassium pump, plasma membrane, permeable, diffusion, electrochemical gradients, negative potential, equilibrium, -70Mv, Na+ gated channels, K+ gated channels, protein channelso When not conducting an impulse, the potential difference across the membrane is -

60mV.This equilibrium is maintained by:o Sodium-Potassium pumps actively transport 3Na+ ions out for every 2 K+ ions into

the cello The axon contains large organic anions, which the membrane is impermeable to.o Slight loss of K+ ions through the permeable membrane: diffusion/electrochemical

gradiento Membrane impermeable to Na+ ions

5. Describe and explain how an action potential is generated: page 14-15a. Give a definition for action potential Is depolarisation of the cell membrane so the inside

is more positive +40mVcompared to the outsideb. What is a generator potential? A small depolarisation caused by Na+ ions entering the

cell c. Why are action potentials described as ‘all or nothing’? All action potentials are the

same size, irrespective of the intensity of the stimulusd. List the key words you would need to use and understand to describe an action

potential: Polarised Stimulus, voltage dependent sodium ion channels, diffusion, depolarises, -60mV, -50mV, +40mV, K+ voltage dependent gated channels, repolarisation, hyperpolarisation, action potential, refractory period.

e. Sort the statements in the table below to the correct order to ‘Describe how an action potential is generated’:

Statement OrderVoltage-gated sodium ion channels open and many Na+ ions enter. As more Na+ ions enter, the more positively charged inside the cell becomes compared to outside.

4

Na+ ion channels open and some Na+ ions diffuse into the cell 2K+ ions diffuse out of the cell, bringing the potential difference back to negative inside compared with the outside; this is repolarisation.

7

The original potential difference is restored, so the cell returns to its resting state. 9The potential difference overshoots slightly, making the cell hyperpolarised. 8The membrane is at resting state; -60mV inside compared to outside: polarised. 1The Na+ ion channels shut and the K+ ion channels open. 6

The membrane depolarises- it become less negative with respect to the outside and reaches the threshold potential of -50mV.

3

The potential difference across the membrane reaches +40mV. The inside is now positive compared to the outside. This is the action potential

5

f. By what process in an action potential do the ions move across the membrane? Diffusion

g. What causes the voltage-gated channels to open in an action potential? When membrane first becomes depolarised at threshold value 0f -50mV

h. After each action potential there is a period of time when another action potential cannot be stimulated in a cell membrane. What is this known as and why is it important? Refractory period, impossible to stimulate the cell membrane, allows cell to recover and ensures impulse goes in one direction only.

6. Describe and explain how an action potential is transmitted in a myelinated neurone, with reference to the roles of voltage-gated sodium ion and potassium ion channels: pages 16-a. Complete the following:b. Axons and dendrons have cells wrapped around them that nourish and protect

them; these are called Schwann cells. In mammals these cells are wrapped many times around, producing multiple layers of the cell surface membrane which is called the myelin sheath. The gaps between the individual cells are called the Nodes of Ranvier.

c. What is the function of the myelin sheath? Means that action potentials can only happen in the gaps between Schwann cells, nodes of Ranvier, this speeds up transmission of action potential.

d. What is saltatory conduction? Action potential jumps from node to nodee. What are the advantages of salutatory conduction? Increases speed of

conduction of action potential.f. How does the action potential travel along the neurone? Sort the statements

below to explain:The answer

1) An action potential is generated at one point in the membrane as sodium voltage-gated channels open

2) Na+ ions diffuse into the cell as they are at a higher concentration outside the cell. This depolarises the membrane at that point

3) The outside of the cell at that area to become more negative due to the loss of positively-charged Na+

4) As the Na+ ions enter the cell, the concentration at that point increases inside the cell5) This creates a concentration gradient to the adjacent areas which have a low

concentration of sodium ions, causing the ions to diffuse along sideways to these areas 6) This in turn depolarises slightly that part of the membrane, causing the voltage-gated

sodium channels to open in that area, so even more sodium ions diffuse into the cell, depolarising the membrane further – inducing an action potential

7) This leads to another concentration gradient of sodium ions to the next area along the membrane and the process repeats – transmitting the impulse all along the membrane

7. Interpret graphs of the voltage changes taking place during the generation and transmission of an action potential: page 15a. Onto the diagram below annotate to describe what is happening in the conduction of an

impulse. Ensure you include all of the following:Stimulus, Na/K pump, Threshold,Resting potential, action potential, Voltage dependent Na+ channels, Voltage dependent K+ channels, Polarised, depolarised, hyperpolarised, -50Mv, +40Mv, K+ Protein channel, refractory period

Other labels to be added as above!

b. Look on line and find a good link that helps you visualise what is happening in the conduction of an impulse. E-mail any good ones to me to forward to the class. Look at these too, which we looked at in class:http://media.pearsoncmg.com/intl/snab_2009/topic_8/interactives/8_2/topic_8_2.html https://www.youtube.com/watch?v=YP_P6bYvEjE https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html http://www.mrothery.co.uk/images/nerveimpulse.swf

c. What are A,B,C,D, E and F on the graph:Answers: A and F show resting potential B is depolarisation (2,3 and 4) C is depolarised (5)D is repolarisation (6 and 7) E is hyperpolarisation (8)

8. Outline the significance of the frequency of impulse transmission: pages 14,21Action potentials do not change in size as they travel – an action potential will always reach + 30 mV all the way along an axon. A neurone will either conduct an action potential or not; this is described as an ___________ ________________ _________. A stimulus at the higher intensity does not cause a larger impulse; they will cause the sensory neurons to produce more _________________ ______________so more frequent action potentials in the sensory neurone. This means more vesicles released at the synapse, a higher frequency of action potentials in the postsynaptic neurone and a higher frequency of impulses to the brain.Answer: All or nothingresponse, generator potentials

9. Compare and contrast the structure and function of myelinated and non-myelinated neurones: page 21a. Compare the structure and function of myelinated and non-myelinated neurones by

producing a table with comparative pointsAnswer:

Myelinated neurones Non-myelinated neurones

100-120ms-1 2-20ms-1Long distances: Up to 1m transmission distance

Short distances: mm or cm transmission distance

Fast response time Slow response timeUsed in movement Co-ordinating body functions: breathing

and digestion1/3 of all neurones 2/3 of all neuronesOne neurone is surrounded by one Schwann cell, wrapped round many times to form the myelin sheath, with gaps called Nodes of Ranvier where there is no myelin sheath.

Associated with Scwann cells, but several neurones are enclosed by 1 loosely wrapped Schwann cell.

10. Describe, with the aid of diagrams, the structure of a cholinergic synapse: pages 18-19 Outline the role of neurotransmitters in the transmission of action potentials: page 19

a. Watch this link at any point during independent study, I would suggest at the beginning and at the end: http://media.pearsoncmg.com/intl/snab_2009/topic_8/interactives/8_4/ topic_8_4.html

b. What is a synapse? A junction between two or more neurones.c. What is the synaptic cleft? Small gap between the 2 neuronesd. What is a neurotransmitter? A chemical that diffuses across the cleft of the synapse to

transmit a signal to the post synaptic neurone.e. What is a cholinergic synapse? Are those that use acetylcholine as their transmitter

substancef. How is the presynaptic knob adapted to its function? Mitochondria lots, vesicles containing

neurotransmitter, voltage dependent gated Ca2+ channels

g. How is the post synaptic membrane adapted to its function? Specialised Na+ channels: complimentary receptors to neurotransmitter

h. What is acetylcholinesterase? An enzyme found in synaptic cleft that hydrolyses acetylcholine

i. Why is it important that the synaptic cleft contains acetylcholinesterase? Removes acetylcholine from the cleft: stops transmission of signals so action potentials are not produced in post synaptic membrane

j. Onto the diagram below, with numbered points describe the ‘transmission of a signal across the synaptic cleft from the arrival of the impulse’. Ensure the following key words are added/labelled/used: Synaptic knob, presynaptic membrane, post synaptic membrane, mitochondria, smooth endoplasmic reticulum, vesicle, acetylcholine, myelin sheath, calcium ion channel, Ca2+, Action potential, diffuse, exocytosis, receptor sites, sodium ion channels, generator potential, excitatory post synaptic potential, threshold, action potential, acetylcholinesterase,

11. Outline the roles of synapses in the nervous system: page 20a. What is the main role of synapses? Primarily, the role of synapses is to connect two

neurones together to pass a signal from one to the other.b. Use the diagram below to explain synaptic

divergence: Several presynaptic neurones may diverge to several post synaptic neurones, this allows one signal to be transmitted to several parts of the nervous system

c. Use the diagram below to explain synaptic convergence: Several presynaptic neurones may converge together to allow signals from different parts of the nervous system to create the same response.

d. How do synapses ensure signals are transmitted in the right direction? They ensure that signals are transferred in only one direction- only the presynaptic knob contains acetylcholine in vesicles.

e. How do they filter out low level stimulus? Why is this important? They can filter out unwanted low-level signal, possibly created by a low level stimulus. Several vesicles of acetylcholine must be released for an action potential to be created in the post synaptic neurone. Ensures that the organism focuses on the important stimuli.

f. Use the diagrams below to explain what summation is and the differences between temporal and spatial summation:

Answer: Low level signals can be amplified by summation (when several small potential charges combine to produce one larger charge in the potential membrane). Sometimes neurotransmitter released by a single neurone is insufficient to depolarise the postsynaptic neurone; however simultaneous release of neurotransmitter from the synapses several neurones; (sometimes from other nerve circuits – known as integration) will be sufficient to cause sufficient depolarisation to generate nerve impulses this is called SUMMATION.

Temporal summation

A single presynaptic bulb fires a number of times in rapid succession with neurotransmitter released each time – causing a build-up of neurotransmitter. Effect of neurotransmitter released on repeated stimulation is added together to initiate an action potential in the postsynaptic neurone

Spatial summation

A number of presynaptic neurones converge onto and form synapses with a single postsynaptic neurone. Effect of neurotransmitter released from many neurones is added together to initiate an action potential in the postsynaptic neurone

g. Explain why we get used to a smell, or the aeroplanes flying above us, the class of chatty pupils. Why is this advantage? Acclimatisation- after repeated stimulation, a synapse may run out of vesicles containing the transmitter substance. The synapse is said to be fatigued. This helps avoid overstimulation of an effector, which could damage it. It ensures we also focus on the important stimuli.

h. Why is the creation of specific pathways important? The creation of specific pathways in the nervous system is thought to be the basis of conscious thought and memory.

12. Review the Learning outcomes for Module 1.1. 5-9 Nerves WWW/EBI?13. Ask for the exam question pack for this module to be e-mailed to you to complete as final

review of this topic.

4.1.3 10-13 HormonesOCR Book pages 22-29

Extension reading: Biological Sciences review articles:

Keywords:Hormones, endocrine, target cells, adenyl cyclase, adrenal gland, adrenaline, alpha cells, beta

cells, pancreas, islets of Langerhans, insulin, hepatocytes, glycogenesis, gluconeogenesis, glycogenolysis, blood glucose concentration, cAMP, diabetes mellitus,Type I, Type II,

hyperglycaemia, hypoglycaemia, genetically engineered, stem cells, cell metabolism, myogenic, pacemaker, SAN,medulla oblongata, cardiovascular control centre, blood pressure, second

messenger.1. By the end of the unit you should have compiled a glossary to include all the key terms

above, and any others that help you understand this module.2. Define the terms endocrine gland, exocrine gland, hormone and target tissue: pages 22-23

a. Define these terms above

Endocrine gland: a gland that secrets hormones directly into the blood. Endocrine glands have no ducts.

Exocrine gland: a gland that secrets molecules directly into a duct that carries the molecules to where they are used.

Hormone: a molecule released into the blood which acts as a chemical messenger

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.

b. Secretion is carried out by glands. There are two main categories of gland, compare in the table below

Endocrine Gland Exocrine GlandSecretes hormones directly into blood Secretes hormones into a duct

No ducts Ducts

Transported all over the body Duct carries molecules to where the

c. Endocrine Glands On the diagram below identify some of the organs of the endocrine system and name some of the hormones they secrete

d. There are 2 types of hormone: Complete the table to compare:

Type of molecule Protein/peptide Steroid

Can it pass through a membrane?

no yes

Location of receptor Receptor on the outside of the cell Enter the cell to bring about the effect

Examples adrenaline Sex hormones

3. Describe the functions of the adrenal glands: pages 22-23a. Where are the adrenal glands? Anterior( above the kidneys)b. Describe the structure of the adrenal glands. 2 regions, medulla and cortex.c. Using the diagram explain the roles of the adrenal medulla and the adrenal cortex

The adrenal glands have two distinct regions- the cortex region and the medulla region. The adrenal medulla releases adrenaline, which:

• Relaxes smooth muscle in the bronchioles• Increases the stroke volume of the heart• Increases heart rate• Causes general vasoconstriction- raising blood pressure• Stimulates conversion of glycogen to glucose• Dilates the pupils• Increases mental awareness• Inhibits the action of the gut• Causes body hair to erect

The adrenal cortex releases corticosteroid hormones which are made from cholesterol. Mineralalocorticoids help control the concentrations of Na and K in the blood Glucocorticoids help control the metabolism of carbohydrates and proteins in the liver4. Explain the meaning of the terms first messenger and second messenger, with reference to

adrenaline and cyclic AMP (cAMP): pages 22-3a. What is a first and second messenger?

First messenger is the hormone (adrenaline) which transmits the signal around the body. The second messenger is a protein (cAMP) which transmits a signal inside the cell

b. Use the diagram and your text book to explain how the hormone causes an effect inside the cell?

5. Describe, with the aid of diagrams and photographs, the histology of the pancreas, and outline its role: page 24a. Where is the pancreas located?

Adrenaline in the blood binds to a specific receptor on the cell surface membrane. The adrenaline molecule is the first messenger.

When it binds to the receptor it activates an enzyme called adenyl cyclase. The enzyme converts ATP to cAMP, which is the second messenger inside the cell.

The cAMP can then cause an effect inside the cell by activating enzyme action.

b. What is the role of the Pancreas?The exocrine cells of the pancreas secrete digestive enzymes into the pancreatic duct, which transports them to the small intestine. These cells make up the majority of the pancreas. The endocrine cells are found in the Islets of Langerhans and consist of α and β cells. The α cells manufacture and secrete glucagon, whereas the β cells manufacture and secrete insulin. They are involved in the regulation of blood glucose levels.

c. Find good diagrams and photographs to put into your independent learning pack to show the histology of the Pancreas. Check, are they good pictures/well labelled?

d. Clearly label these diagrams to show you understand.6. Explain how blood glucose concentration is regulated, with reference to insulin, glucagon

and the liver: pages24-5 Look in book and check!a. Complete the following diagram, showing how we are able to control blood sugar levels.

Name the organ(s) where each stage occurs.

b. Define the following terms:

Term Definition Occurs when blood

concentration is HIGH

Occurs when blood

concentration is LOW

Glucose Hexose sugar yes no

Glycogen Polysaccharide, storage in animals Not in blood Not in blood

Glucagon Hormone that causes blood glucose concentrations to rise

no yes

Glycogenesis Glucose converted to glycogen for storage

yes no

Gluconeogenesis Production of glucose by conversion from amino acids/fats

no yes

Glycogenolysis Conversion of glycogen to glucose no yes

TIP: What does neo mean? New Lysis mean? Breaking down Genesis mean?creation

Rise in blood glucose

concentration

Glucose concentration

falls

Fall in blood glucose

concentration

Glucose concentration

increases

Normal blood glucose concentration:

7. Outline how insulin secretion is controlled, with reference to potassium channels and calcium channels in beta cells: page 26

a. Complete the flow chart and add numbers to the diagram to show how insulin secretion by beta cells is regulated.

TEACHER: See page 26 for diagram and 7 points.

i. The cell membranes of the β cells contain Ca2+ and K+ ion channels.ii. The K ion channels are normally open, and the Ca ion channels are normally shut. K ions

diffuse out of the cell, making the inside more negative. (at rest pd =-70mV)iii. When glucose concentration outside of the cells is high, more glucose molecules diffuse

into the cell.iv. The glucose is quickly metabolised to ATP.v. The extra ATP causes the K ion channels to close.

vi. The K ions can no longer diffuse out, so the cells become more positive inside.vii. This change in potential difference opens the Ca ion channels.

viii. Ca2+ ions enter the cell and cause the secretion of insulin by making the vesicles containing insulin move to the cell surface membrane and fuse with it, releasing insulin by exocytosis.

ix. Compare and contrast the causes of Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes mellitus page 27a. Complete a table to compare the 2 types of diabetes and their cure; ensure you have a

comparative statement e.g.

Type 1 diabetes is insulin-dependent diabetes

Type 11 diabetes is non-insulin-dependent diabetes.

Body is unable to produce (enough) insulin / does not secrete insulin / produces ineffective insulin

Body can produce insulin but insulin receptors lose the ability to detect and respond to insulin

The insulin-producing cells (beta cells) are destroyed by the (body’s own) immune system. This is an auto-immune disease. It can be genetic. It can be triggered by a virus

Late onset (more prevalent over 40)Risk increased by

increasing age family history / genetic /

hereditary being males being African / Afro-

Caribbean / Asian / Hispanic / Oceanic

being obese / overweight / having fat around abdomen

high / frequent, intake of sugar / highly processed food / high GI food

lack of physical activity / sedentary lifestyle

high blood pressure excessive alcohol intake

Treatment: insulin injections Treatment-monitoring and controlling diet

b. Why is insulin injected rather than taken in tablet form? It would be digested: protein.c. Complete the boxes to explain the shape of the curve: page 27

x. Discuss the use of insulin produced by genetically modified bacteria, and the potential use of stem cells, to treat diabetes mellitus page 27a. What are genetically engineered bacteria? Those bacteria in which the DNA has been

altered (recombinant DNA).b. What are stem cells? Unspecialised cells that have the potential to develop into any type

of cell.c. Describe the use of insulin produced by genetically modified bacteria. Used for people

with diabetes.d. What are the advantages/issues?

GM bacteria:• Exact copy of human insulin.

o Faster acting.o More effective.

• Less chance of developing tolerance.

• Less chance of rejection.• Cheaper.• More adaptable to demand.• Less likely to have moral

objections.

e. Describe the use of stem cells to produce insulin. Used for type 1 diabetes; precursor to pancreas cells found in mice, can develop into a variety of cell types, if similar cells could be found in human pancreas then could be used to produce new beta cells.

xi. Outline the hormonal and nervous mechanisms involved in the control of heart rate in humans pages28-29

a. What is cell metabolism? The result of all of the chemical reactions taking place in the cytoplasm of the cell.

b. Why is it important that the heart should be able to adapt its rate? Because the requirements of the cell ( oxygen, glucose, wastes like carbon dioxide) vary according to their level of activity, it is vital that the heart can adapt to meet these needs.

c. Define myogenic? Muscle tissue that can initiate its own contractions.d. What is the pacemaker of the heart? SANe. Describe what happens when the pacemaker generates an action potential SAN, wave of

excitation over atria walls, to AVN, down Purkyne fibres, base of ventricles, contract.f. What can affect the frequency of contraction of the pacemaker? Nerves from medulla

oblongata, action potentials sent from medulla oblongata to SAN down an accelerator nerve, increases heart rate, vagus nerve, decreases HR. Adrenaline can also affect HR.

g. What is the cardiovascular centre? Specific region of the Brain in the medulla oblongata that receives sensory input about levels of activity, blood carbon dioxide levels and blood pressure from a variety of receptors. Sends impulses to San, to alter the frequency of the excitation waves. Accelerator nerve increases and vagus nerve decreases.

h. What hormone can affect the heart rate? Adrenalinei. Draw flow diagrams explaining :

i. The effect of a low pH on heart rateWhen we exercise we produce more carbon dioxide: A drop in pH detected by chemoreceptors in the carotid arteries, the aorta and the brain (when we exercise we produce CO2, this dissolves in H2O in the blood and forms carbonic acid, reducing the pH).

o CO2+H2O → H2CO3

o H2CO3→ H+ + HCO3-

The chemoreceptors send impulses to the cardiovascular center which increases HR to get rid of carbon dioxideii. The effect of a high pH on heart rate

Stop exercising, carbon dioxide levels fall, reduces activity on accelerator pathway, HR slows

iii. The effect of high blood pressure on heart rateBlood pressure monitored by stretch receptors in walls of carotid sinus (carotid artery), High blood pressure, and signals sent to CVC, responds by reducing HR, vagus nerve.

iv. The effect of low blood pressure on heart rate converse of above.j. Draw a time line explaining the development of pacemakers. (see text book page 29)k. Check the learning outcomes for this sectionl. Request the exam questions for this module as a final check of your understanding.

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