+

Area of Study 2:EXPECTED LEARNINGTo revise homeostasis and immunity

+Quiz What are two differences between the endocrine and

nervous systems?

What are the 5 plant hormones and what do they do?

What is the main difference in the signal transduction pathway between amine/polypeptide and steroid hormones?

Describe the three lines of defence and the major parts/cells of the immune system involved in each

What is an autoimmune disease? What is an immunodeficiency disease? (definition and eg)

What is involved in an allergic response?

+Homeostasis

The maintenance of a constant internal environment despite changes in external environment

NB. Internal environment = The medium in which the body cells of multicellular organisms are bathed (i.e. extracellular fluid, interstitial fluid, plasma, lymph)

+What needs to be kept within narrow limits?

M.I.T.G.O.W.B + pH + wastes

Metabolites (eg blood glucose concentration)

Ions (eg salts)

Temperature

Gases (eg CO2 and O2)

Osmolarity (ie water balance)

Wastes (e.g. urea)

Blood Pressure

pH

+

Mechanoreceptors respond to mechanicalenergy (e.g. ear drum)

Thermoreceptors respond to heat or cold (e.g. nerve endings in skin)

Electromagnetic receptors respond to electromagnetic energy (e.g. ampullae of Lorenzini in sharks)

Photoreceptors respond to visible light and UV radiation (e.g. eyes).

Chemoreceptors respond to chemicalstimuli (e.g. olfactory)

Detecting signals from external environment

+Stimulus-response model

Response

Stimulus Receptor

Control centre

Effector

Transmission - nerves

Transmission – nerves or hormones

+Stimulus-response model exampleNegative Feedback

Increase in blood CO2

Receptor in arteries and

veins

Respiratory centre in

brain

Respiratory muscles in

lungs

More CO2 exhaled

Transmission - nerves

Transmission - nerves

Negative feedback – response counteracts the stimulus

+Two Types of Feedback

Positive Feedback Negative FeedbackOrgan or Gland Organ or Gland

Releases a substance to act on a system

Releases a substance to act on a system

System Acted Upon

System Acted Upon

Releases a secondary substance which acts on the gland or organ

Releases a secondary substance which acts on the gland or organ

Inhibits (stops) further release of the original substance

Promotes or encourages more of the original substanceto be released

+Feedback Loops

+Endocrine System

Uses chemical signals for cell to cell communication

Coordinates the function of cells

Response to an endocrine signal occurs within minutes to hours

+Endocrine System

Endocrine glands Release hormones into the bloodstream.

Hormones Chemicals released in one part of the body that travel through the bloodstream and affect the activities of cells inother parts. body.

+Hormones Cell to cell communication molecules

– Made in gland(s) or cells

– Transported by blood

– Distant or local target tissue receptors – can only communicate message to cell with the corresponding receptor (on cell membrane or within cytosol)

– Activate physiological response

– Negative feedback prevents hormone overproduction

+Types of hormones

+

Made in endocrine cells

Transported via blood to act at a site distant from the secreting cell or gland

Receptors on target cells

Long Distance Communication: Endocrine Hormones

+ Local communication: Paracrine and Autocrine Hormones

Act locally, either on the secreting cell or a neighbouring cell

Diffuse to target Autocrine – receptor on same cell

Paracrine – neighbouring cells

e.g. cytokines in immune system

+Neurocrine Hormones

+PheromonesChemicals released by animals to communicate with

other members of their own species

Can be used for: Attracting mates

Inducing mating activity

Marking territory

Signalling alarm

Marking food trails

+Plant tropisms

A plant growth response to an external stimulus Light = phototropism Gravity = geotropism

Thigmotropism = touchhttp://www.youtube.com/watch?v=1ZuZ_1cQnv4&feature=related

Growth towards the stimulus is a positive tropism

Growth away from the stimulus is a negative tropism

Responses rely upon chemical signals that initiate a signal transduction pathway in plant cells to produce a growth response.

+Plant hormones

+ Auxin

Indole acetic acid and related molecules

Photo-and gravitropism

Stimulates cell elongation

Made in the shoot apex

Travels down the stem

Apical dominance

Prevents leaf abscission (ie leaf shedding)

Enhances fruit growth

+Cytokinin

Cytokinins delay and even reverse senescence

Release buds from apical dominance

Stimulate cell division Cytokinins

Auxin

+ Gibberellins

Essential for stem elongation

Found as the toxin produced by some fungi that caused rice to grow too tall

Dwarf plant varieties often lack gibberellins

Gibberellins are involved in bolting of rosette plants

Promote cell division and elongation

Gibberellins are used to improve grapes

Gibberellins are involved in seed germination– gibberellins will induce genes to make enzymes that break down starch

+Ethylene gas

The smallest hormone

Important in seed germination, fruit ripening, epinasty (i.e. downward bending of leaves), abscission of leaves

Sex expression in cucurbits (i.e. pumpkins, zuccini)

+Abscisic acid (ABA)

Generally acts as an inhibitor

Important in water stress and other stresses

Causes stomatal closure

Prevents premature germination of seeds

Changes gene expression patterns

+Responding to light Plants possess light-sensitive enzymes –

phytochromes

Exist in two forms that interchange according to the light they are exposed to. active form (Pfr) at sunrise (i.e. red light) inactive form (Pr) at sunset (ie far-red light)

when exposed to red light the enzyme is able to catalyse a number of reactions within the cell, leading to altered transcription of genes in the nucleus, or activation of proteins already in the cell

influences responses such as seed germination, stem elongation, and formation of leaves, flowers, fruits, and seeds

+ Photoperiodism Photoperiodism is a biological response to a change in

relative length of daylight and darkness as it changes throughout the year.

Phytochrome, and other chemicals not yet identified, probably influence flowering and other growth processes.

"Long-day plants" flower in the spring as daylength becomes longer (e.g. spinach).

"Short-day plants" flower in late summer or early autumn when daylength becomes shorter (e.g. broad beans).

"Day-neutral plants" flower when they are mature.

+Signal transduction pathway

A mechanism linking a mechanical or chemical stimulus to a specific cellular response.

Communicating cells may be close together or far apart

+Cell communication

1. Production of extracellular signalling molecule (called a ligand) by a cell

2. Detection of this ligand by a receptor protein on or in target cell

3. Transduction of ligand through cell

4. Cellular response

5. Control or regulation of ligand or response

+2. Detecting the signalTo stimulate a response, hormones bind to specific receptor on OR in the target cell to form hormone-receptor complex

The cell targeted by a particular signal has a receptor molecule complementary to the signal molecule, or ligand.

Most amine and polypeptide-based hormones are not able to move through cell membrane – receptor proteins are on the cell membrane

Steroid hormones move through membrane and bind with receptors in cytoplasm

+ Receptor locations

Cytosolic or Nuclear– Lipophilic ligand enters cell– Often activates gene– Slower response

Cell membrane– Lipophobic ligand can't enter

cell– Outer surface receptor– Fast response

Figure 6-4: Target cell receptors

+3. Transduction

Converts the change in the receptor to a form that can bring about a cellular response.

This might involve a series of steps - a signal transduction pathway - that alters and amplifies the change.

Small amounts of signalling molecule can produce a significant response or even multiple responses due to amplification.

+3. Transduction

Once a hormone-receptor complex is formed, the way the signal is transferred depends on the type of hormone:

Amine and polypeptide hormones: Second messenger is produced that stimulates cell response.

Steroid hormones: hormone can enter the cell easily, binding

to receptor and initiating response. Tends to be slower, but longer lasting than second messenger response.

+Non-steroidal, lipophobic hormonesUsually involves the binding of extracellular

signalling molecules, like hormones and neurotransmitters, to receptors that face outwards from the membrane and trigger events inside the cell.

The binding of a hormone with a receptor often stimulates the action of a second protein (e.g. G protein), or an enzyme, within the cytoplasm.

This enzyme can then stimulate the activity of other enzymes to bring about a response.

+

+

+Steroidal, lipophillic hormones Lipid soluble hormone travels in bloodstream via a

carrier protein( insoluble in water) and passes through the cell membrane.

Binds to receptor protein found only in target cells. Hormone-receptor complex then enters the

nucleus. Binds to specific regulator site for the targeted

gene. Stimulates the gene to produce mRNA. mRNA is read by ribosomes to produce a specific

protein.

+

+4. Response

the transduction process brings about a cellular response.

can be one of many different cellular activities, such as: activation/inhibition of a certain enzyme rearrangement of the cytoskeleton regulate protein expression through activation of specific

genes. Open or close protein channels, etc

Once the cellular response is initiated, the ligand is degraded by cell enzymes

+Summary

+Summary

+The nervous system

This communication system controls and coordinates functions throughout the body and responds to internal and external stimuli.

Maintains homeostasis by detecting change and coordinating action of effector organs

Responsible for unidirectional, fast communication

brain

Spinal Cord

Cerebellum

Cerebrum

Medulla Oblongata

The Central Nervous System (CNS)

Consists of the brain and spinal cord

+The peripheral nervous system (PNS)

Nerves extending out to the rest of the body from the CNS

Includes all sensory neurons, motor neurons, and sense organs

+Nerve cells: NeuronsThe basic functional unit of the nervous system.

Send impulses to and from the CNS and PNS and the effectors (muscles/glands)

+ Types of Neurons

+The nervous systemSensory receptors monitor changes in the

environment

Afferent or sensory nerve cells transfer messages to the central nervous system (CNS)

Efferent or motor nerve cells transfer messages from the CNS to effector organs

(See Jacaranda diagram)

+Nerve impulses

Information is transferred in the form of an electrical impulse

The cell membrane of a nerve cell is polarised i.e. there is a difference in charge between the inside and

outside of the cell

+Neuron at rest: Resting potential

A condition where the outside of the membrane is positively (+) charged compared to the inside which is negatively (-) charged.

Neuron is said to be polarized.

+How is resting potential maintained?

Ion Distribution

+Nerve impulses: Action potentialAs an impulse moves along an axon, the

permeability of the membrane changes

Positive sodium ions move into the neuron Potassium ions move out of the neuron The inside of the membrane is positively (+) charged

compared to the outside which is negatively (-) charged.

This is called an ACTION POTENTIAL

+Nerve impulses

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

+Neuron Communication: SynapsesA synapse is the junction between two nerve

cells (e.g. axon bulb of one neuron and the dendrite or cell body of a second neuron).

A very small gap, called the synaptic cleft, lies between the two neurons.

Molecules called neurotransmitters relay messages across the synaptic cleft between the two neurons. The communication between neurons is chemical in nature.

+Neuron Communication: Synapses

+Neuron Communication: Synapses

Communication across the synapse involves:

Release of neurotransmitters (e.g. actylcholine) from secretory vesicles of presynaptic neuron

Exocytosis of neurotransmitter across the presynaptic membrane and release into the synaptic cleft

Attachment of transmitter to protein receptors on the postsynaptic membrane, opening protein channels, leading to stimulation of the neuron or effector cell

Deactivation of neurotransmitter by enzymes and reabsorption into presynaptic neuron

http://www.youtube.com/watchv=HXx9qlJetSU&feature=related

+Reflex arc

An involuntary response that is processed in the spinal cord not the brain.

Reflexes protect the body before the brain knows what is going on

Definitions

Immunity The ability of the body to fight infection

and/or foreign invaders by producing antibodies or killing infected cells.

Immune System The system in the body responsible for

maintaining homeostasis by recognizing harmful from non-harmful organisms and produces an appropriate response.

Foreign Invaders

Pathogens Cellular or non-cellular

agents that cause disease/immune response.

Antigens Compounds, usually

proteins, on the outside of pathogens that can trigger the immune system to respond.

+Major Parts of the Immune System

1. Blood - White Blood Cells in particular.

2. Lymphatic system - vessels carry a type of fluid named lymph, which bathes the tissue of the body and also is a ‘transport network’ for immune cells.

3. Lymph nodes - the centre of activity where lymphocytes (a type of white blood cell) are continually circulating from tissue in the body, to the lymph nodes and back again by using the bloodstream and lymphatic vessels.

4. Thymus Gland – Produces T Lymphocytes

5. Bone Marrow – Produces B Lymphocytes

•Self= cells and other substances that are a part of the organism and carry “self” markers (i.e. MHC markers) •Non-self = organisms, cells and other substances that are not part of the organism and carry antigens

What is self and non-self?

Major Histocompatibility Complex

• Simple terms: Major Histocompatibility complex is a cluster of genes that produce proteins that form the markers on our cells. These markers are known as MHC Class 1 molecules.

• Each person’s MHC markers are different

MHC

Inside the cell...

MHC marker protein recognised

BANG!!R.I.P.

Edward Non-Self

How does the body fight pathogens?

The Body’s THREE lines of Defense

FIRST LINE

SECOND LINE

THIRD LINE

+

Pathogen Invades Tissue

Non-Specific Defences

Barriers to EntrySkinMucousSecretionsNatural Flora

Physiological MechanismsFever

Chemical Mechanisms Complement proteins Interferons

MechanismsPhagocytes (granulocytes,Macrophages), Natural killer cells (cytotoxic)

Inflammation Mast cellsRelease of Histamine

Specific Defences

Second line of defenseFirst line of defense

+

Pathogen Invades Tissue

Non-Specific Defences

B-cells T-cells

Specific Defences

Third line of defense

Plasma cells – produce antibodies

Memory cells – remember antigen

Helper T-cells (Th) - stimulate B cells

Cytotoxic t-cells (Tc) kill body cells infected with a pathogen

+

ANTIGENS: Any substance foreign to the body that triggers a response from the immune system, such as producing antibodies in order to neutralise it.

- Usually made up of proteins but can be polysaccharides

- All have unique shapes

- A way to remember:antigens = antibody generators

- Antibodies are generated to attack thepathogen behind the antigen being detected

Antigens.

Antibodies/Immunoglobulins

The third line of defense involves the production of antibodies:

Y-shaped protein molecules

Produced by B-cells

Made up of variable (recognizes antigen) and constant regions.

Function: Recognize antigens, bind to and deactivate them.

+ANTIGENS AND ANTIBODIES.

http://www.youtube.com/watch?v=Ys_V6FcYD5I

+IgG IgA IgM IgD IgE

Approx. Concentration in serum (mg/mL) 12 2 1 0.04 0.000.02

Ability to cross placenta yes no no no no

Present in saliva and tears no yes no no no

Present in milk yes yes no no no

Active against viruses yes yes some no no

Active against some bacteria yes yes yes no no

Involved in allergy reaction no no no no yes

Immune Response Summary

Antigen

Helper T - Cell

Active Cytotoxic T-Cell Active B - Cell

Kills Infected Cells Memory T- Cell Plasma Cell Memory B-Cell

Antibodies

Deactivates Antigens

Displays copy of antigen on surface of cell

Cellular ImmunityHumoral Immunity

+Clonal selection

+Acquiring immunity

Long lasting vaccines

Short lasting vaccines

+Autoimmune Diseases

Autoimmune diseases cause antibodies in the immune system to act against the body’s tissues!

There are 80 different types (e.g. MS, Chrohn’s disease etc)

The cause is unknown…

BUT, it is genetic and can pass through your family.

An autoimmune disorder may result in:

-The destruction of body tissue

-Abnormal growth of an organ

-Changes in organ function

+Immunonodeficiency diseases

Immunodeficiency refers to a malfunction or deficiency in one or more components of the immune system.

PRIMARY IMMUNODEFICIENCY:Disorders where part of the immune system is missing or not functioning properly. Most are genetic disorders.

SECONDARY IMMUNODEFICIENCY:Same as Primary Immunodeficiency, but is caused by a secondary nature, e.g. caused by another disease, drug treatment or environmental exposure to toxins (e.g. HIV leading to AIDS)

+Allergies

Overreaction of immune system to harmless antigens (e.g. dust, pollen etc)

Mast cells are immune cells involved in allergic responses. Circulating basophil cells are also involved in allergic responses, but to a much lesser extent. Both kinds of cells contain large granules of histamine.

IgE binds to mast cells and, to some extent, to basophils. IgE antibodies are made against antigens such as dust, pollen and plant spores.

If a person contains IgE antibodies for a particular antigen, they are said to be sensitised to that antigen.

If the person is further exposed to the same antigen, cross links are

formed between the antibody on the mast cells and the antigen. These antibody–antigen cross links trigger mast cells to release active agents such as histamine (which causes contraction of smooth muscle.

+Quiz What are two differences between the endocrine and

nervous systems?

What are the 5 plant hormones and what do they do?

What is the main difference in the signal transduction pathway between amine/polypeptide and steroid hormones?

Describe the three lines of defence and the major parts/cells of the immune system involved in each

What is an autoimmune disease? What is an immunodeficiency disease? (definition and eg)

What is involved in an allergic response?