Human Bio WACE Exam

Validity

-       Testing what is meant to be tested

Data represents the phenomenon you are measuring

Reliability

An experiment gives the exact same result each time it is performed

Exocrine

-       secretes into a duct that exits the body

                    - Eg, sweat and salivary glands

Endocrine

secretes hormones into the extracellular fluid that surrounds the cells that make up the gland.

Cellular effects of hormones

-       Activates a gene/s

-       Changes shape of enzymes

-       Changes the rate of transcription and translation

Protein and amine hormones

Water soluble, Attaches to receptor proteins on the membrane of the target cell, The combination of the hormone with the receptor causes a secondary messenger to be released and diffuse through the cell and activate particular enzymes

Steroid hormones

Lipid soluble, Combines with a receptor inside the cell. Activates the genes to synthesise a particular protein

Functions of the hypothalamus

-       Controls secretions to the pituitary gland via releasing and inhibiting factors

-       Regulates body temperature, water balance and heart rate (homeostasis)

-       Produces hormones that are carried to the pituitary gland

-       Hormones produced here either inhibit or stimulate hormone production in the anterior pituitary

-       Other hormones pass through the nerve fibres to the posterior where they are secreted

-       Makes hormones for posterior pituitary

Structure of the Pituitary Gland

-       Lies under the hypothalamus and is joined to it by the infundibulum

-       Consists of an anterior and posterior lobe

-       Anterior lobe is at the front and is connected to the hypothalamus by a complex network of blood vessels

-       Posterior lobe is to the rear and is joined to the hypothalamus by nerve fibres, does not make hormones

-       Secretes hormones that control other endocrine glands

What hormone does the thyroid produce and what effects does it have

Thyroxine,

targets most cells,

increases metabolic rate and therefore oxygen consumption and heat

What hormone does the parathyroid produce and what effects does it have

Parathyroid hormone (PTH)

targets bones, kidneys

bones release calcium, reabsorption of calcium

What hormone does the thymus produce and what effects does it have

Thymosins,

targets t lumphocytes

stimulates development and maturation of t lymphocytes 

What hormone does the pineal gland produce and what effects does it have

melatonin,

controls sleep patterns and circadian rhythms, stimulated by darkness and inhibited by light

Adrenal cortex

aldosterone- kidney, reduces amounts of sodium and increase amount of potassium in the urine

cortisol- most cells, promotes normal metabolism, helps the body deal with stress, promotes repair of damaged tissue

What hormone does the Adrenal Medulla produce and what effects does it have

Adrenaline and Noradrenaline- most tissues, prepares the body for fight or flight responses. increases rate and force

Pancreas

Insulin- most cells, stimulates uptake of glucose. lowers blood glucose levels.

Glucagon- liver and fat storage, stimulates the breakdown of glycogen and fat to increase blood glucose levels

What hormones do the testes produce and what effects do they have

Androgens- many tissues, stimulates sperm production, growth of skeleton and muscles and secondary sexual characteristics

What hormones do the ovaries produce and what effects do they have

Estrogen- many tissues, stimulates the development of the female characteristics and regulates the menstrual cycle

Progesterone- uterus and mammary gland, regulates the menstrual cycle, pregnancy and prepare the mammary glands for milk secretion

Enzyme amplification

-       Series of chemical reactions

-       1 hormone activates 1000’s of enzyme molecules

-       1 hormone causes a hormonal cascade which could trigger the production of over a billion enzyme molecules

Hormone clearance

-       Hormone is turned off

-       The breaking down of a hormone once it’s finished its job

-       Broken down at kidney or liver

-       Excreted in bile or as urine

How are hormone secretions regulated

by negative feedback

Negative Feedback Loop

-       Negative feedback is when the response produced by the secretion of the hormone is the opposite of the stimulus that caused the secretion

-       Releasing factors stimulate the release of a hormone

-       Inhibiting factors slow down the secretion of a hormone

What is a neuron

A nerve cell

What is a nerve

A bundle of nerve fibres (Any long extension of cytoplasm of a nerve cell body, although the term usually refers to an axon) held together by connective tissue

CNS vs. PNS

Central Nervous System: Consists of the spinal cord and the brain.

Peripheral Nervous System: Nerves that connect the central nervous system with the receptors, muscles and glands of the body

Myelinated vs. Unmyelinated fibres

Myelinated fibres: An axon with the myelin sheath covering

Unmyelinated fibres: An axon without the myelin sheath covering

Grey matter vs. White matter

 

Grey matter: Consists of nerve cell bodies and unmyelinated fibres

White matter: Composed of myelinated fibres (fatty tissue)

Sensory/receptor neurons (unipolar) structure and function

Carry messages from receptors in the sense organs or skin to the central nervous system (brain and spinal cord)

Carry messages from receptors in the sense organs or skin to the central nervous system (brain and spinal cord)

Motor/effector neurons (multipolar) structure and function

Carry messages from the central nervous system (brain and spinal cord) to the muscles and glands

Has 1 axon and multiple dendrites extending from the cell body

Interneurons (bipolar) structure and function

Connects sensory and motor neurons together, found in the spinal cord and for reflexes in the grey matter of the spinal cord

Cell body is to one side of the axon

Synapse-

-       The junction between the branches of adjacent neurons, -       Occurs between a branch at the end of an axon and a dendrite or the cell body of another neuron

Transmission across a synapse-

1)    An action potential arrives at the pre-synaptic axon terminal

2)    Local depolarisation causes voltage gated calcium ion channels to open

3)    Calcium ions from the extracellular fluid diffuses through the presynaptic membrane of the axon terminal and enters the cytoplasm of the axon terminal

4)    The calcium ions cause neurotransmitter vesicles to migrate to the pre-synaptic membrane of the axon terminal

5)    The neurotransmitter leaves the vesicles and enters the synaptic cleft through exocytosis

6)    The neurotransmitter diffuses across the synapse to the post-synaptic membrane of the dendrite of the adjacent neuron

7)    Sodium ions flood in, causing depolarisation in the postsynaptic dendrite

8)    An action potential will be generated

Nerve impulse-

1)    A resting neuron has a positive charge on the outside of the membrane and a negative charge on the inside (resting membrane potential -70mV)

2)    There is a high concentration of positive sodium ions on the outside and a high concentration of positive potassium ions on the inside

3)    There is a greater concentration of negatively charged ions on the inside of the membrane than positive potassium ions making the inside negatively charged

4)    A stimulus causes voltage gated sodium ion channels to open and sodium ions rush into the intracellular fluid

5)    -55mV is threshold for voltage gated sodium channels

6)    The inward movement of positively charged sodium ions reverses the charges either side of the membrane

7)    The cell becomes depolarised, the charge on the inside is positive and the charge on the outside is negative

8)    After the inside of the membrane becomes flooded with sodium ions, gated potassium channels open and allow the potassium ions to move to the outside

9)    As soon as the potassium ions are released, the sodium ion channels close (membrane is repolarised)

10) The sodium potassium pump restores the concentration of sodium and potassium ions when the membrane is a resting state

Nerve impulses in myelinated vs. unmyelinated fibres

Unmyelinated	Myelinated
Depolarisation of one area of the cell membrane causes an action potential to flow onto the membrane immediately adjacent to the stimulus. (1)	Depolarisation of one area of the cell membrane causes an action potential to jump from one node of Ranvier to another. (1)
The nerve impulse/exchange of ions (NOT action potential) moves along the entire length of the neuron/axon. (1)	The nerve impulse/exchange of ions (NOT action potential) only occurs at the nodes of Ranvier or cannot occur where the axon is myelinated. (1)
Lower concentration gradient of ions either side of the membrane. (1)	Higher concentration gradient of ions either side of the membrane at the nodes of Ranvier. (1)
The nerve impulse / message (NOT action potential) travels along the whole length of the fibre, reducing its speed. (1)	The action potential jumps from one node of Ranvier to the next on the myelinated fibre (saltatory conduction), the impulse can travel faster. (1)

Saltatory conduction-

when the nerve impulse jumps from one node of Ranvier to the next

Divisions of the PNS

Afferent (sensory)

Somatic: Carries impulses from receptors around the muscle and skin to the CNS

Visceral: Carries impulses from the internal organs to the CNS

Efferent (motor)

Autonomic: Carries impulses from skeletal muscles to the CNS

Somatic: Carries impulses to the heart and other involuntary muscles

Autonomic

Sympathetic: Fight or flight response, prepares body for strenuous activity

Parasympathetic: Rest and digestion, maintains body during quiet and restful conditions

Autonomic vs. Somatic

Characteristic	Autonomic	Somatic
Effectors	Involuntary muscles/organs	Skeletal muscles (voluntary)
General function	Adjustment of the internal environment	Response to the external environment
Efferent (motor) pathway	2 nerve fibres from the CNS to the motor neuron with a synapse in a ganglion.	One nerve fibre from the CNS to the motor neuron, no synapse and no ganglion
Neurotransmitter at effector	Noradrenaline = sympathetic Acetylcholine = parasympathetic	Acetylcholine at neuromuscular junction
Control	Involuntary	Voluntary
Nerves to target	2 sets, sympathetic and parasympathetic	One set, excitation of skeletal muscles
Effect target organ	Excitation or inhibition	Always excitation

Effects of the Sympathetic vs. Parasympathetic NS

Neurotransmitter	Noradrenaline	Acetylcholine
Heart	Increases rate and strength of contraction	Decreases rate and strength of contraction
Lungs	Dilates bronchioles	Constricts bronchioles
Stomach	Decreases movement	Increases movement
Liver	Increases breakdown of glycogen and released as glucose	Increases uptake of glucose and synthesis of glycogen
Iris of the eye	Dilates pupils	Constricts pupils
Sweat glands	Increase sweat secretion	No effect
Salivary glands	Decreases saliva secretion	Increases saliva secretion
Blood vessels of:   Skin   Skeletal muscles   Internal organs	Vasoconstriction   Vasodilation   Vasoconstriction (except heart and lungs)	Little effect   No effect   Little effect
Urinary bladder	Relaxes muscles of wall	Constricts muscles of wall
Adrenal medulla	Stimulates hormone secretion	No effect

Compare the Nervous System and the Endocrine System

	Nervous System	Endocrine System
Speed	Rapid	Slow
Duration	Quick	Long
Transmission	Neurons	Hormones
Nature	Electro-chemical	Chemical
Cells affected	Muscles and glands	All body cells
Type of response	Specific/local	Widespread

What things are responsible for the protection of the NS

Bone (outer)	Cranium and vertebral canal = tough outermost protective layer
Meninges (connective tissue)   -       Outer layer (dura matter) -       Middle layer (arachnoid matter) -       Inner layer (pia matter)	Tough and fibrous Loose mesh of fibres Contains blood vessels that stick closely to the brain and spinal cord
Cerebrospinal fluid (between pia and arachnoid matter)	Shock absorber, cushions the brain and spinal cord

Function of the cerebral cortex

Higher order functions such as thinking, reasoning, memory, learning and conscious awareness of surroundings. Comprised of 4 lobes

Function of the corpus callosum

Nerves fibres that allow communication between the 2 cerebral hemispheres

Function of the cerebellum

Coordination of fine contraction of voluntary muscle for smooth movements, balance and posture

Function of the hypothalamus

Homeostasis; appetite, thirst, metabolism, body temperature, response to fear, water levels, sleeping

Function of the medulla oblongata

Regulates heart, breathing and diameter of blood vessels

 

Cardiac centre- Regulates rate and force of heart beat

 

Respiratory centre- Regulates rate and depth of breathing

 

Vasomotor centre- Vasoconstriction and vasodilation of blood vessels

Function of the spinal cord

Made up of grey matter and surrounded by white matter

 

contains sensory axons carrying impulses towards the brain (ascending tract)

 

contains bundles of motor axons carrying impulses from the brain to the muscles (descending tract)

 

Responsible for spinal reflexes, which are reflexes by nerve cells in the spinal cord without input from the brain

What is homeostasis

the ability of an organism to maintain a constant internal environment/steady state despite changes in either internal or external conditions to maintain optimal functioning of cells/cell processes/metabolic processes

Types of Receptors-

Receptor	Location	Detects
Thermoreceptors	Hypothalamus (central) Skin (peripheral)	Core body temperature External temperature
Osmoreceptors	Hypothalamus	Osmotic pressure
Chemoreceptors	Nose Mouth Blood vessels Medulla oblongata	Regulation of chemicals in the body. pH levels
Touch receptors	Skin (lips, fingertips, eyelids and genitals)	Responds to touch
Pain receptors	Skin Mucous membranes Most organs (not brain)	Damaged tissues
Pressoreceptors	Aorta Right carotid artery Right atrium	Blood pressure

Define a reflex and describe its properties

A rapid autonomic response to a change in the internal or external environment

Properties

1)    Requires a stimulus

2)    Involuntary and occurs without conscious thought

3)    Response is rapid, only a small number of neurons involved

4)    Response is stereotyped, the impulse travels the same way each time it happens

What occurs in a spinal reflex arc?

Pathway of a nerve impulse travels from a receptor to an effector

1)    A receptor which is on a sensory neuron reacts to a change in the internal or external environment by initiating a nerve impulse along the sensory neuron

2)    A sensory neuron carries the impulse from the receptor to the CNS (brain or spinal cord)

3)    The nerve impulse is passed to an interneuron via a synapse which is in the grey matter of the spinal cord

4)    The impulse is then passed to the motor neuron via a synapse in the grey matter of the spinal cord.

5)    The motor neuron carries the nerve impulse to an effector

6)    The effectors carry out the appropriate response, normally a skeletal muscle cell or secretory cells

Label the parts of a spinal reflex

Parts of the negative feedback loop (sister ruby munches eggs really fast)

Stimulus: the change in environment causing the system to operate, Eg core temp above 37

Receptor: detects the change, Eg thermoreceptors

Modulator: the control centre, process the information from the receptor and sends the information to the effector to act. Hypothalamus

Effector: carries out appropriate response. Eg, sweat glands

Response: counteracts the effect of the stimulus, Eg sweat secretion

Feedback: the original stimulus has been changed by the response, Eg core temp lowered to 37

Positive Feedback loop-

-       No role in homeostasis

-       Response to stimulus is intensified

-       For body processes that must be completed quickly

-       Release of oxytocin from posterior pituitary during child birth

Feedback loop- heat

Feedback loop- osmoregulation

Feedback loop- blood sugar

Feedback loop- blood oxygen

Compare insulin and glucagon and their role in blood glucose regulation

Insulin (beta cells)	Glucagon (alpha cells)
Decrease blood sugar levels	Increase blood sugar levels
1)    Accelerates transport of glucose from the blood inti the cells, especially skeletal muscles	Converts glycogen into glucose
2)    Accelerates the conversion of glucose into glycogen	Glucose is released into blood, increasing blood sugar levels
3)    Also stimulates conversion of glucose into fat and adipose tissues	Produce new sugar molecules from fats and amino acids (gluconeogenesis)
Chemical sensors in beta cells stimulate secretion of insulin
Glycogenolysis	Glycogenesis

What is Insulin’s role in BG regulation?

Effector: Beta cells

Processes ·      Glycogenesis – conversion of glucose to glycogen in liver/muscles. ·      Lipogenesis – conversion of glucose to lipids in adipose tissue

What is glucagon role in BG regulation?

Effector: Alpha cells

Processes ·      Glycogenolysis – conversion of glycogen to glucose in liver/muscles. ·      Gluconeogenesis – conversion of lipids and amino acids to glucose in the liver

What is adrenaline/noradrenaline’s role in BG regulation?

Effector: Adrenal medulla

Processes ·      Glycogenolysis – conversion of glycogen to glucose in liver/muscles. ·      Glycogenolysis (Cori cycle) – lactic acid produced can be transported to liver and converted into glucose

What is thyroxine’s role in BG regulation?

Effector: Thyroid gland

Processes ·      Increases absorption of glucose from the small intestine into the bloodstream ·      Increases rate of cellular respiration, leading to increased rate of glucose absorption into all cells of the body.

Define glycogenesis

Conversion of glucose into glycogen from other carbohydrates, especially glucose

Define glycogenolysis-

Breakdown of glycogen to glucose

Define gluconeogenesis

Conversion of fats and amino acids into glucose

How is breathing stimulated?

-       As carbon dioxide is dissolved in water, it forms carbonic acid which then dissociates to form hydrogen and bicarbonate ions

-       Increase in hydrogen = decrease in pH

-       Hydrogen/carbon dioxide stimulate peripheral chemoreceptors (aortic and coarotid bodies) which then send impulses to the respiratory centre of the medulla oblongata

-       The impulses from the medulla stimulates the diaphragm and intercostal muscles via the phrenic and intercostal nerves respectively

Describe the receptors responsible for stimulating breathing

Central chemoreceptors	Peripheral chemoreceptors
In medulla oblongata	In aortic and carotid bodies
Detect CO2 concentration, pH of blood plasma and cerebrospinal fluid	Measures changes in pH (hydrogen ion concentration), CO2 and O2 of blood plasma
Takes a few minutes to respond and communicate	Responds quicker due to their location
Responsible for majority control of breathing	Small control over O2 breathing rate

hyperventilation-

-       Rapid and deep breathing to provide more oxygen and remove more carbon dioxide than necessary

-       More O2 in, more CO2 out-       Can occur due to severe physical and emotional stress

-       It will correct itself as the chemoreceptors will not be stimulated since they are more receptive to co2  and breathing will not be required until it returns to normal

-       Can be done intentionally to hold breath

-       However, as the breathing reflex responds to CO2, the person may require O2 before CO2 levels rise to the point where the body stimulates the breathing reflex.

This could result in a lack of oxygen to the brain, causing the person to fall unconscious

Disruptions to homestasis: Diabetes-

high blood glucose levels where insulin is not being produced or not enough of it is being produced

Type 1 vs. Type 2

	Type 1	Type 2
Causes	Caused by autoimmune response on beta cells in the pancreas	Caused by lifestyle factors, eg overweight, lack of exercise
Insulin	Does not produce insulin but cells do respond to it	Does produce insulin but cells don’t respond to it
Treatment	Requires daily injections of insulin to manage conditions	Require management of diet, eg increase activity
When	Normally begins in childhood/early life	Normally begins onwards of 40

effects of high blood glucose levels-

-       Damage to blood vessels

-       Blindness

-       Kidney failure

-       Cardiovascular disease

-       Loss of sensation

-       Ulcers and gangrene

-       Amputation of toes or foot

Causes of hyperthyroidism

-       Thyroid gland produces too much thyroxine

-       Overactive thyroid

Diseases

Graves’ disease = immune system attacks thyroid

symptoms of hyperthyroidism

-       Increased metabolism

-       Rapid heart beat

-       Unexplained weight loss

-       Increased appetite

-       Fatigue

-       Sweating

-       Anxiety

Protruding eyeballs

Treatment for hyperthyroidism

-       Surgery to remove part of the thyroid gland

Drugs that block the thyroids’ use of iodine

hypothyroidism- causes, symptoms, treatment, diseases

Causes	-       Lack of iodine available to the thyroid gland -       Thyroid not producing enough thyroxine
Symptoms	-       Slow heart rate -       Unexplained weight gain -       Fatigue -       Lack of energy -       Intolerance to cold
Treatment	-       Synthetic hormones containing iodine
Diseases	Hashimoto’s disease

Infectious disease

a disease passed from one person to another by infection with micro-organisms

Pathogen

a disease-causing organism

Vector

an agent capable of transferring a disease-causing organism from one person to another

Non-specific defences-

defences of the body that act against all pathogens

Specific defences-

defences of the body that are directed against specific pathogens

Structural features of bacteria and their functions

Structure	Description
Slime layer	For protection of the bacteria from antibiotics
Cell wall	Made of peptidoglycan, a combined carbohydrate protein
Cell membrane	Controls movement of substances in and out of the cell
DNA	No nuclear membrane, so DNA forms a tangle inside the cells. Some DNA is in the form of loops called plasmids
Plasmids	DNA in loops inside the bacteria
Flagella	Allow for movement
Cytoplasm	Where the organelles hang out in
Capsule	Formed of complex carbohydrates for protection.

Methods of Transmission for pathogens

Transmission	Description	Example
Transmission by contact	Direct: physically touching an infected person Indirect: touching an object which has been touched by an infected person	STI’s
Transmission of body fluids	From an infected person which comes into contact with the mucous membrane or bloodstream of the uninfected person	HIV Hepatitis B and C
Droplets	Contains the pathogen which is breathed in or ingested. Emitted through coughing, sneezing or breathing	Measles Colds Influenza
Ingestion	Eating or drinking food which had been contaminated with pathogens	Typhoid fever Salmonella Dysentery
Airborne	Similar to transmission by droplets. If virus and bacteria survive it can cause infection once inhaled	Chickenpox Measles
Vectors	An agent which is capable of transferring a pathogen from one person to another. Vectors can spread directly or indirectly. Vectors are specific to a disease	Malaria = mosquitos Dengue fever

Bacteria vs. Virus

Feature	Bacteria	Virus
Size	0.5-5 micrometres	20-400 nanometres
Protein coat	No	Yes
Cell wall	Yes	No
Plasma membrane	Yes	No
Cytoplasm	Yes	No
Nucleus	No	No
Membrane-bound organelles	Yes	No
DNA/RNA	DNA and RNA	DNA or RNA
Diseases caused	Salmonella Pneumonia Norovirus Listeria E. coli.	HPV HIV AIDS Common cold Warts

External non-specific pathogens-

External non-specific defences	Description	Location
Skin	Physical barrier. Secretes sebum which is an oily fluid which kills pathogens. Fatty acids and salts in sweat also prevent micro-organisms from growing	Outside of the body
Sebum	An oily secretion produced by sebaceous glands which kill some pathogenic bacteria	Secretes into the blood
Sweat	Secreted by sweat glands and contains salts and fatty acids which prevent the growth of many micro-organisms	Skin Mucus membranes
Mucous membrane	Lines the body cavities that open to the exterior. Secrete mucus which prevents the entry of micro-organisms to the body	Lines the body cavities

Internal non-specific responses- phagocytes

Cells which ingulf and digest micro-organisms and cell debris

Internal non-specific responses- leucocyte

Have the ability to leave the blood capillaries and migrate through tissues to the place of infection

Macrophage

macrophages are involved in specific and non-specific defences. Non-specific = engulfing pathogens. they Secrete substances that kill bacteria Specific = alerts the immune system to the presence of foreign material. They are phagocytic

Internal non-specific responses- inflammation

Shows signs of redness, swelling, heat and pain. Occur as a result of the process which shows in response to an infection

Internal non-specific responses- fever

Elevation of body temperature caused by an increase in the body’s thermostat (controlled by hypothalamus). Inhibits growth of bacteria/viruses and speeds up the rate of chemical reactions which allow cells the repair at a faster rate

Internal non-specific responses- pyrogens

Chemicals released by white blood cells during an inflammatory response which acts directly on the hypothalamus, causing it to increase body temperature

what happens during an inflammatory response

1)    When stimulated by mechanical or chemical damage, mast cells release histamine, heparin and other substances. Mast cells stimulate and co-ordinate inflammation by releasing chemicals

2)    Histamine increases blood flow through the area and causes the walls of the blood capillaries to become more permeable so that fluid is filtered from the blood. This increase in blood blow causes the heat and redness associated with inflammation, and the escape of fluid from the blood causes swelling

3)    Heparin prevents clotting, so the release of heparin from the mast cells prevents clotting in the immediate area of the injury. A clot of the fluid around the damaged area does form and this slows the spread of the pathogen into healthy tissues

4)    The chemicals released by the mast cells attract phagocytes. Macrophages and leucocytes actively consume micro-organisms and debris by phagocytosis

5)    The abnormal conditions in the tissue stimulate pain receptors, and so the person feels pain in the inflamed area

6)    The phagocytes, filled with bacteria, debris and dead cells, begin to die. The dead phagocytes and tissue fluid form a yellow liquid called pus

7)    New cells are produced by mitosis and repair of the damaged tissues takes place

Specific Resistance: Humoral vs. cell mediated responses

Characteristics	Humoral (antibody-mediated response)	Cell mediated
Type of cell	B-cells	T-cells
Where are they produced	Bone marrow	Bone marrow
Location of maturation	Bone marrow	Thymus gland
Where are they found	Lymphoid tissue Lymph node Spleen Thymus gland Tonsils
Location of resistance to infection	Extracellular fluid (blood, lymph)		Intracellular fluid

How antibodies act on pathogens

1)    Combine with foreign enzymes or bacterial toxins to inactivate them

2)    Bind to the surface of viruses and prevent them from entering cells

3)    Coat bacteria to make them easier to be consumed by phagocytes

4)    Agglutination, making phagocytosis easier.

5)    Dissolve organism/antigen/pathogen

6)    Combining with soluble antigens to make them insoluble

Response to a Foreign antigen in body

1)    B-cells are sensitised by non-self-antigens in the extracellular fluid

2)    B-cells enlarge and divide into groups called clones

3)    Most of clones become antibody-secreting plasma cells, the rest become memory cells

4)    Antibodies circulate in the blood, lymph and extracellular fluid

5)    Antibodies combine with antigens to form antigen-antibody complexes

6)    Memory cells spread to all body tissues, so that a rapid response can occur should the antigen enter the body again

Antigen

any substance capable of causing a specific immune response. Proteins on surface of cell

Antibody

substance produced in response to a specific antigen. Combines with the antigen to neutralise it or destroy it

First response vs. Secondary response 

Primary response	Secondary response
First exposure to non-self-antigen	Second exposure to non-self-antigen
Slow response	Fast response
B-cells to multiply and differentiate into plasma cells	There’s already heaps of plasma cells and memory cells from the primary response
Takes several days to build up large amounts of antibodies	Antibodies are released straight away preventing severe symptoms

Killer T-cells

migrate to site of infection and attach to invading cells and secrete a substance that will destroy the antigen

Helper T-cells

Intensifies the immune response by attracting more macrophages, intensifies the phagocytic activity of macrophages

Suppressor T-cells

slows down immune response after infection is dealt with successfully. Releases substances that inhibit T and B cell activity