biology notes on coordination and control

Coordination and Response
Nervous Control in Humans

The nervous system consists of two parts:

Central nervous system (CNS) consisting of the brain and spinal cord, which are the
areas of coordination

Peripheral nervous system (PNS) made up of nerves and neurones, which
coordinate and regulate bodily functions.

Involuntary actions: not under conscious control e.g. reflex action

Voluntary actions: are done if we decide to carry them out

Types of Neurons

Nerve impulse: an electrical signal that passes along nerve cells called neurones

Motor Neurone:

Sensory Neurone:

Relay (connector) neurone:

Reflex arc

A reflex action is an involuntary, quick action to respond to a stimulus, in order to protect
the body from danger

E.g. quickly removing your hand from hot metal surface

They involve three neurones: a sensory neurone, relay neurone and motor neurone.

The gap between neurones is called a synapse.

How the reflex arc works:

A stimulus affects a receptor (cell or organ that converts a stimulus into an electrical

A sensory neurone carries impulse from the receptor to the CNS

Connector/relay neurone carries impulse slowly (because it has no myelin sheath)
across the spinal chord

Motor neurone carries impulse from the CNS to the effector

Effector (either a muscle or a gland) carries out the response

Reflex action: means of automatically and rapidly integrating and coordinating stimuli with
the responses of effectors (muscles and glands)


Synapse: a junction between two neurones, consisting of a gap across which impulses pass
by diffusion of a neurotransmitter

Synaptic cleft: small gap between each pair of neurones

Inside the neurones axom, there are 100s of tiny vacuoles (vessicles each contain a chemical
called neurotransmitter)

When an impulse arrives, the vessicles move to the cell membrane and empty their content
into the synaptic cleft

The neurotransmitter quickly diffuses across the tiny gap and attaches to receptor molecules
in the cell membrane of the relay neurone

This can happen because the shape of the neurotransmitter molecules is complimentary to
the shape of the receptor molecule

Many drugs e.g. heroin act upon synapses

Antagonistic Muscle

A muscle that opposes the action of another; e.g. biceps and triceps are antagonistic
muscles or circular and radial muscles in the eye

Agonist: a muscle that contracts while another relaxes; e.g. when bending the elbow, the
biceps are the agonist

Antagonist: a muscle that relaxes while another contracts; e.g. when bending the elbow, the
triceps are the antagonist

Sense organ: groups of receptor cells responding to specific stimuli: light, sound, touch,
temperature and chemicals.

The Eye

The sense organ responsible for sight

Cornea: refracts light

Iris: controls how much light enters pupil

Lens: focuses light onto retina

Retina: contains light receptors, some sensitive to light of different colours

Optic nerve: carries impulses to the brain


Adjusting for near and distant objects.

Near Object

Distant Object

Ciliary muscles contract

Ciliary muscles relax

Ligaments relax

Ligaments are tight

Lens becomes short and fat

Lens becomes long and thin

Pupil Reflex

Adjusting for high and low light intensity

Low Light Intensity

High Light Intensity

Radial muscles (straight lines) contract and
become shorter to pull the pupil (black dot)
making it wider, to let more light enter, to form a
clear image on retina

Circular muscles (circular lines) contract
and become shorter to reduce the size of
the pupil to protect retina from

Rods and Cones



Provide low detail, black & white images, good
for seeing in low intensity light (at night).

Provide detailed, coloured images; they
work in high light intensity.

Packed most tightly around edge of retina so
you can see things most clearly when not
looking directly at them.

Most tightly packed at centre of retina, so
objects are seen most clearly when being
directly looked at.


Part of the retina where the receptor cells are pushed most closley together

Where light is focused when you look straight at an object


A chemical substance, produced by a gland, carried by the blood, which alters the activity of
one or more specific target organs and is then destroyed by the liver.


A hormone secreted by the adrenal gland.

It increases pulse rate, makes the glycogen in muscles is converted to glucose and released
into blood, makes you breathe deeper and more rapidly, airways become wider, and makes
skin become pale as blood is diverted away.

Increases blood glucose concentration for respiration.

Adrenaline is secreted for example: while bungee jumping or riding a rollercoaster




Adrenal gland


Prepares body for vigorous action



Reduces conc. of glucose in blood



Causes development of male sexual characteristics



Causes development of female sexual characteristics

Nervous and Hormonal Systems

Nervous system

Endocrine system

Speed of action

Very rapid

Can be slow


Nervous system

Endocrine system

Nature of message

Electrical impulses,
travelling along nerves

Chemical messenger (hormones)
travelling in bloodstream

Duration of response

Usually within seconds

May take years (puberty)

Area of response

Localized response (only
one area usually)

Widespread response (in many

Example of process

Reflexes such as blinking

Development of reproductive system

Hormones are used in food production, for example oestrogen is used to boost growth rate
of chickens.

Advantage: chickens grow quickly meaning more profit.

Disadvantages: this may cause human males to develop feminine characteristics, and it is


The maintenance of a constant internal environment.

Homeostasis is the control of internal conditions within set limits

Negative Feedback

Feedback controls the production of hormones – the hormones regulate their own

A negative feedback control is when the change in hormone level acts as a signal to cancel
out that change, so when blood hormone level is low, hormone production is stimulated,
when it is high, it is inhibited.


Blood glucose levels are monitored and controlled by the pancreas

The pancreas produces and releases different hormones depending on the blood glucose

Insulin is released when blood glucose levels are high – the liver stores excess glucose as

Glucagon is released when blood glucose levels are low – the liver converts stored glycogen
into glucose and releases it into the blood

When the control of blood glucose does not work, a person is said to have diabetes

Type 1 diabetes is caused by the death of the cells that secrete insulin

Symptom: hyperglycaemia (feel unwell, dry mouth, blurred vision and feel thirsty) or
hypoglycaemia (tired, show confusion and irrational behaviour)

Treatment: eating little and often and avoiding large amount of carbohydrates,
injecting insulin to reduce blood glucose concentration


Constant body temperature is maintained by:

Insulation: provided by fatty tissue retains heat. Hairs become erect to trap warm air by
contracting erector muscles and vice versa.

Vasodilatation: when it is hot, arterioles, which supply blood to the skin-surface capillaries,
dilate (become wider) to allow more blood near to skin surface to increase heat loss (face

Vasoconstriction: when it is cold, arterioles, which supply blood to the skin-surface
capillaries, constrict (become smaller) to allow less blood near to skin surface to decrease
heat loss

Sweating: the water evaporates giving a cooling effect

Skin receptors: sense heat and sensory neurons send impulses to the hypothalamus

Shivering: muscular activity generates heat

Thermoregulatory centre: in the hypothalamus, it controls the use of corrective
mechanisms (e.g. sweating and shivering).

Homeostatic Organs

Cells: change composition of blood as they remove nutrients and O2 and add wastes and

Heart: keeps blood pressure constant to deliver oxygen and nutrients around body

Skin: to maintain heat exchange with external environment

Kidneys: regulate water and salt levels (osmoregulation) and the removal of wastes like urea

Lungs: regulate gas exchange

Intestines: supply soluble nutrients and water to blood

Liver: regulates blood solutes and removes toxins

Tropic Responses


Plant hormones or growth substances

Controls tropisms

It is produced by cells at the tip of roots and shoots of plants

Gravitropism: a response in which a plant grows towards (positive) or away (negative) from

Auxins’ role in gravitropism:

Tend to settle at the bottom end of the root.

However, this does not make the cells of the tip of the root grow longer; auxins
prevent cells at bottom tip of root from growing, making cells at top of root grow

When cells of top of the root grow faster, they push root deeper into soil and root
gets longer.

The root grows in direction of the gravitational pull.

Phototropism: a response in which a plant grows towards (positive) or away (negative) from
the direction from which light is coming.

Auxins’ role in phototropism:

If sun shines on right side of a plant’s shoot, auxins will accumulate on dark opposite
left side.

Auxins accumulating makes cells on left side grow faster than cells on right side.

When left side of shoot starts growing faster than right side, shoot will start to bend
to right side towards sunlight.

Hormones can be used as weed killers: spraying with high concentrations of hormone (2,4D) upsets normal growth patterns. It affects different species differently so might only kill
one species not the other (this is good).


Drugs: Any substance taken into the body that modifies or affects chemical reactions in the


Antibiotics work by stopping a metabolic practice performed by the bacteria you are trying
to get rid of, but not performed by human cells.

Some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics

Development of resistant bacteria such as MRSA can be minimised by limiting use of
antibiotics only when essential and ensuring treatment is completed

Antibiotics don’t work on viruses because they are not really living and they make the host
cell perform the tasks for them.

Effects of the abuse of heroin: a powerful depressant

Problems of addiction

Severe withdrawal symptoms (vomiting, restlessness)

Malnourishment as drug depresses appetite

Financial problems – stealing, loss of job

Infection from sharing needles e.g. HIV/AIDS

Heroin affects the nervous system by its effect on the function of synapses

Effects of excessive consumption of alcohol –a depressant:

Causes coronary heart diseases

Reduced self-control


Effect on reaction times

Damage to liver – cirrhosis

Some effects of tobacco smoke:

Drying effect and heat irritate lungs – destroys cilia

Nicotine is addictive, it is also a stimulant, it increases pulse rate and narrows blood vessels
which can cause damage

Tobacco smoking can cause chronic obstructive pulmonary disease (COPD), lung cancer and
coronary heart disease

Tar causes cancer, and is an irritant so causes coughing.

There are other irritants in tobacco smoke including: smoke particles, ammonia, and sulphur

Emphysema: walls between alveoli break making large sacs, reducing surface area massively
and making you breathless after a couple of steps

Loss of limbs due to poor circulation, CHD and lower sperm-count

Carbon monoxide irreversibly bonds with haemoglobin which can lead to oxygen starvation

Cancer of the stomach, pancreas and bladder etc.

Liver is the site of breakdown of alcohol and other toxins

Hormones and Sports

Hormones: can be used to improve sporting performance


Improved hand-eye coordination

Improved body-fat composition

Increased muscle mass

Anabolic Androgenic Steroids

Affects limbic system

Mood swings

Impaired judgement

High blood pressure

Kidney failure

Increased risks of prostate cancer (male)

Inconsistencies of menstrual cycle (female)

Changes in blood cholesterol

Asexual Reproduction

The process resulting in the production of genetically identical offspring from one parent.


Reproduce by binary fission, each bacterium divides into two.

The generation time is the time taken for a cell to divide into 2.


Single-celled yeast reproduces by binary fission.

All other fungi produce via spores.

When the sporangium bursts it spreads the spores.

Spores land and grow mycelium (roots) for example mushrooms


The shoot from a potato goes back underground and the stem swells to form a new
genetically identical potato.

The swollen stem acts as a storage organ.



Fast: no need to find mate, fertilise etc.

No variation

Good characteristics are kept

Harmful genes transferred


Overcrowding- fighting for food

Sexual Reproduction

Sexual reproduction: process involving the fusion of the nuclei of two gametes (sex cells) to
form a zygote and the production of offspring that are genetically different from each other

Fertilisation: the fusion of gamete nuclei

Nuclei of gametes are haploid and that the nucleus of a zygote is diploid



Produces genetically different

Takes lots of time and energy

don’t all die from change in the

Good characteristics can be lost

Energy on improving appearances or pollen volume for
pollination (plants)
Sexual Reproduction in Plants

Insect pollinated, dicotyledonous flowering plant: foxglove

Wind pollinated flower structure: grass


Sepal: protect the flower bud.

Petal: brightly coloured and scented and may have nectarines which are all used to attract
insects, petals in wind pollinated flowers are tiny, and used for pushing the bracts (leaf-like
structures) apart to expose stamens and stigma

Anther: has pollen sacs with pollen grains which contain the male nucleus (male gamete).

Stigma: platform on which pollen grains land

Ovary: hollow chamber, ovules grow from the walls.


Pollination: transfer of pollen grains from the male part of the plant (anther of stamen) to
the female part of the plant (stigma).

Agents of pollination: insects, birds, mammals, water and wind

Insect Pollinated

Wind Pollinated

Large colourful petals – attract

Dull petals

Sweetly scented

No scent


No nectaries

Insect Pollinated

Wind Pollinated

Moderate amount of pollen

Huge amount of pollen

Pollen is spiky/sticky

Pollen round and smooth

Anther & stigma inside flower

Anther & stigma hangs out

Stick stigma

Stigma hairy

Flowers have stripes which act as guide-lines for insects

Pollen tube: pollen grain lands on stigma and creates a tunnel down the style, through the
micropyle, to the ovules.

Structure of non-endospermic seed:

Formation of a seed: the zygote divides many times by mitosis to form and embryo. The
cotyledon is the food store. The testa stops drying out of embryo.

Wind and animal dispersal are used by plants to colonise new areas; done because new
areas have less competition for light, space and nutrients, so seeds are more likely to

Wind Dispersed Seed

Animal Dispersed Seed


Apple (internal)

Wind Dispersed Seed

Animal Dispersed Seed


Bur (external)


A process controlled by enzymes

Water: activates enzymes to turn insoluble food stores into soluble substances, and makes
tissues swell so that the testa splits

Oxygen: enters through the gaps in the testa (along with water), and is used in aerobic

Temperature: must be suitable for enzymes to work (at optimum temperature).


Sexual Reproduction In Humans

Male reproductive system:

Testes: have many coiled tubes which produce sperm, and the cells between tubes produce

Scrotum: holds testicles

Sperm duct: carries sperm from testicles to urethra.

Prostate gland: makes seminal fluid

Urethra: carries semen from sperm duct to tip of penis

Penis: male sex organ, used to transfer semen to the female.

Female reproductive system:

Ovary: contains follicles which develop into the ova and produces progesterone and

Oviduct (fallopian tube): carries the ovum to uterus

Uterus (womb): where the fetus develops.

Cervix: neck of uterus: a strong rigid muscle, moist by mucus with a small opening

Vagina: receives penis during intercourse, and way out for baby at birth. Moist tube of
muscle, flexible and secretes mucus

Menstrual Cycle

Day 1 to 5:

In the ovary, FSH secreted by the Pituitary Gland to stimulate the maturation of
ONE follicle in the ovary.

In the uterus: the endometrium breaks down; menstruation

Day 5 to 12:

In the ovary the follicle keeps maturing

In the uterus, oestrogen is secreted by follicle and the ovarian tissues to prepare
the endometrium

Day 13/14/15:

In the ovary, LH is also secreted by the Pituitary Gland to trigger the release of the
egg from follicle into the fallopian tube

Day 15 to 28:

In the ovary, LH triggers formation of Corpus Luteum

In the uterus: progesterone is secreted by Corpus Luteum to
keep endometrium thick, waiting for possible embryo implant.

Day 28 – Scenario 1: Egg not fertilized

No implantation takes place, the Corpus Luteum degenerates, causing a lack of

This means that endometrium is no longer thick, back to Day 1

Day 28 – Scenario 2: Egg is fertilized

Implantation occurs.

This makes the hormones to keep the Corpus Luteum maintained which means
that progesterone is high.

This keeps the Endometrium thick for pregnancy

Hormones in Menstrual Cycle

Oestrogen is secreted by the ovaries. It stops FSH being produced – so that only one egg
matures in a cycle and it stimulates the pituitary gland to release hormone LH.

Progesterone is a hormone secreted by ovaries. It maintains the lining of the uterus during
the middle part of the menstrual cycle and during pregnancy.

Follicle stimulating hormone (FSH) is secreted by the pituitary gland. It causes an egg to
mature in an ovary and it stimulates ovaries to release hormone oestrogen

Luteinizing hormone (LH): is also secreted by pituitary gland and causes mature egg to be
released from ovary.

Sexual Intercourse

Penis fills with blood and becomes erect

Vagina walls secrete a lubricant.

Rubbing of the glans (end of penis) against the vagina wall sets of a reflex action, causes
sperm to be released from the testes, and is transported by peristalsis along sperm ducts
and urethra, where seminal fluid is added to make semen.

The exit of semen from the penis is called ejaculation.

Sperm then swim through the cervix and oviducts to the first third of the oviduct (from the
ovary) where one combines with the egg.


The fusion of an ovum and a sperm to form a zygote.

Development of zygote:

One sperm penetrates

Ovum membrane alters to form barrier against sperm

Head of sperm (male nucleus) approaches and then fuses with the nucleus of the

Zygote divides over and over, to make a ball of cells called an embryo.

It implants itself in the wall of the nucleus (implantation) which is followed by

Development of foetus: zygote is changed through growth (mitosis) and development
(organization of cells into tissues and organs)

Umbilical cord: contains umbilical artery which carries deoxygenated blood and waste
products from foetus to placenta and umbilical vein which carries oxygenated blood and
soluble food from placenta to foetus. (Contains foetus’ blood)

Placenta: organ for exchange of soluble materials such as foods, wastes and oxygen
between mother and foetus; physical attachment between uterus and foetus. (Contains
mother’s blood)

Amniotic sac: membrane which encloses amniotic fluid, broken at birth.

Amniotic fluid: protects foetus against mechanical shock, drying out and temperature

Antenatal Care:

Change in diet:

More proteins → growth of foetus

Slightly more fat → the new cells’ cell membrane

More vitamin C and D → blood vessel walls and bones

Iron → haemoglobin

Calcium → growth of bones and teeth

Guidance on motherhood

Checks on foetus and mother including: weight check, blood tests, urine tests, blood
pressure checks, ultrasound scanning etc.

Labour and Birth

Labour: The uterine muscular wall contract and cervix tries to relax, then contractions get
more frequent. Contractions cause amniotic membrane to break and release amniotic fluid.

Expulsion: Powerful Contraction pushes baby out.

Afterbirth: Placenta is expulsed out. All contraction & pain gone






Very mobile – use its tail

Many more



Immobile – moved by peristalsis

Fewer and limited

| Damage beauty | | No additives /preservatives | | | Builds mother-child bond | | | No
cost/preparation | | | Causes decline in uterus size | |
Bottle feeding:


Less painful

More likely to develop illness

Other people can feed baby

Risk of wrong mixture

May contain supplement vitamins and minerals


Sex Hormones

At puberty, the pituitary gland starts to stimulate the primary sex organs; the testes in males
and the ovaries in females.

Sex hormones – testosterone in males and oestrogen in females are released into the

They only affect the target organs which have receptors which can recognize them.

Causes secondary sexual characteristics such as the growth of pubic hair and maturation of
sexual organs.

Methods of Birth Control


Abstinence: don’t have sex

Rhythm method: don’t have sex during the fertile period, only during the safe period


Progesterone-only pill: pill which affects the uterus and makes implantation difficult

Spermicide: a chemical applied as a gel, cream or foam which kills sperm. It is very
unreliable on its own but makes barrier methods of contraception more effective.


Condom: thin rubber covering over penis, it protects from impregnation and STDs,
used by man

Diaphragm: used by woman, prevent sperm entering uterus, reliable, must stay in
place 6 hours after sex, needs a correct size

Femidom: closed end, has a ring which gets pushed through cervix and open end’s
ring lies against the labia

IUD: plastic-coated copper coil, can be left inside for months or even years, has a
string which is used to remove it out of the vagina, reliable, it irritates uterus wall
preventing implantation


Vasectomy: sperm ducts are cut and tied

Female sterilization: oviducts are cut and tied

Artificial Insemination

By donor: man’s sperm has a problem, making impregnation impossible, so a donor gives his

In vitro fertilization: an ovum is fertilized outside a woman’s body. The fertilized ovum is
implanted into the uterus.

Fertility drugs: drugs which enhance reproductive fertility. For women, fertility medication is
used to stimulate follicle development of the ovary. The side effect is multiple pregnancies.
They contain varying amount of FSH and LH.

Human Immunodeficiency Virus (HIV)

Transmission: Intercourse, blood transfusion, organ transplant or sharing needle with
infected person


Avoid intercourse with many partners

Use a condom

Don’t come in contact with other people’s blood

How it affects the immune system:

Infects and destroys lymphocytes

Decreases efficiency of immune system

Body becomes liable to infection by other pathogens

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