Biology - Coordination and Control

Introduction

Your nervous system makes you know what is going on in the world around you. This enables you to react to your surroundings and coordinate you behaviour.

You do this quickly because the impulses travel from 1 to 120 metres per second.

Nervous System

Your receptors pick up stimuli (changes) in your surroundings.

Receptor cells are like any animal cells. They are usually clustered in sense organs.

Your tongue and nose are used for taste and smell of chemicals. Ears are sensitive to sound and the balance of your body. Eyes are sensitive to light and skin is sensitive to touch, pressure, pain and temperature.

1. The information from a receptor pass along the sensory neuron.(Bundles of neurons are called nerves).

2. The impulse will then reach the central nervous system made up of the spinal chord and the brain and pass the relay neuron.

3. The brain will then send another impulse that passes the motor neuron.

4. Finally the impulse will tell what the effector organs how to respond. Your muscles will contract and the glands will produce chemicals.

Introduction

Reflexes are so quick that you will ract before you have time before you can think and feel any pain.

Automatic responses like this are calle reflexes.

Reflexes

Your reflexes are caused by the reflex arch made up of sensory neurons, relay neurons and motor neurons. They pass from one to another via the brain.

The goal for doing this is so your reactions are as quick as possible.

Receptor - Sensory Neuron - Synapse - Relay Neuron - Synapse - Motor Neuron - Effector Organ

Hormones are defined as a chemical released from the glands that stimulate cells and tissues.

Hormones are carried around in your blood stream.

The hormones of the menstrual cycle are made in her pituitary gland and ovaries.

The levels of the three hormones used rise and fall in a regular pattern.

The menstrual cycle lasts 28 days, and in this time the lining of the uterus thickens to support a baby and the egg matures.

On day 14 the egg is released from the ovaries, this is called ovulation.

If the egg is fertilised then pregnancy may take place and the womb will supply the baby with protection and food, if not the lining of the womb are shed from the body.

The hormones released come from the pituitary gland (in the brain) and from the ovaries.

• Follicle Stimulating Hormone (FSH) is secreted in the pituitary gland, it makes the eggs mature and stimulates to production of oestrogen.

• Oestrogen is made by the ovaries, it stimulates the lining of the womb and inhibits the production for FSH.

• Luteinising Hormone inhibits the production of oestrogen and releases the egg.

• Progesterone maintains the lining of the womb.

One of the main ways to decrease the fertility rate is to take a contraceptive pill.

The pill contains a mixture of hormones but mainly oestrogen. This inhibits FSH and does not allow the egg to mature, therefore the woman cannot get pregnant.

If they do not take the pill regularly, the natural hormones take over and a mature egg can be produced easily providing a possible baby. 

The first contraceptive pills contained only oestrogen whch led to high blood pressure and head aches. Now there is less amount of oestrogen and some progesterone.

There are some pills with only progesterone but they do not work as well because they are not as good at keeping the egg from maturing.

There are many problems where women cannot make enough FSH therefore have a less likely chance of fertility.

However, there are drugs containing FSH that allow the egg to mature and cause the production of oestrogen.

Fertility drugs are also used in IVF. If the womans fallopian tube is damged they cannot reach the womb so doctor collect eggs from the ovary and sperm and fertilise them outside the womb.

When the embryos are formed they are placed into the uterus to grow into a baby.

Durinf IVF, FSH is released to increase the chance of fertility.

IVF is expensive and not always successful.

If too much water moves in and out of your cells they can be destroyed.

How much it moves depends on the mineral ions, such as salt.

You take in water and minerals through what you eat and drink. You then secrete them through breathing (water), urine and sweating (water and minerals) which is made in your kidneys.

Your kidney decides how much water and salt you lose to keep the balance between them and your kidney is controlled by nerves and hormones.

The pale the urine the more concentrated it is, the more concentrated it is the more you have been drinking water.

It is vital for your deep core body temperature to be at 37 degrees enzymes work best at this temperature.

It can kill you if you body temperature is a few degrees above of below this.

Your nervous system is important to the way your body responds, you sweat to cool down and shiver to warm up.

If your body goes to 35 degrees you can die of hypothermia.

If it goes over 40 degrees you can die of a heat stroke.

Controlling Blood Sugars 

There is a high percentage of glucose when you have eaten in your blood.

The concentration of the glucose is kept constant in the pancreas.

Without it, after a meal the levels would shoot up then go very low a few hours later, this would cause chaos. 

Summary

All three things above are controlled to keep the internal environment the same.

If the internal environment keep on changing the organs cannot function.

The processes inside your body to keep control is called homeostasis.

It is important when a seed germinates the roots go down (to get minerals and water) and the shoot to go up (to photosynthesis).

The plant roots are sensitive to water and gravity and shoots are sensitive towards gravity and sunlight.

The main plant hormone is auxin.

The hormone makes the shoots go towards light which is called phototropism while the roots go towards gravity which is gravitropism.

This is so that no matter which way the seed is the shoot and roots will go in the right direction.

Auxin bends towards the side of the shoot where is is dark, this makes the cells grow more so the plant bends toward the light.

Auxin in the roots inhibits growth, this is why the shoot and roots respond differently to gravity.

Some people disagree with using hormones because some think it is unnatural.

Auxin make effective weed killers and auxin can be made in factories.

They are affective as the do not affect grass.

However, in Vietnam War weed killers were used (Agent Orange) by Americans to kill the forests to find the enemy.

However, the chemicals affected thousands of people very badly.