Nerves and Hormones
The nervous system is the sending of electrical impulse around the body. The Nervous system consist of receptors, muscles, neurone and Synapse. One main thing you need to remember is that the nervous system doesn't bypass the brain and happens within Millie-seconds of coming into contact with a stimulus. The nervous system is the reason we react and without it we would be a lot more seriously injured. An example of this is when you touch something really hot. The body sends the electrical impulse around the nervous system in order for you to move your hand away to stop serious burning.
Auxin = A hormone in plants.
Diffuse = Where a particles spread out and decrease in concentration as they more away from a source.
Effector = something that is triggered as a result of the electrical impulse.
Elongate = Something that increases in length.
Fertilised = to render the female sex cell capable of development by uniting it with the male sex cell.
Hormone = chemicals that are secreted by glands around the body.
Inhibits = Stops it from happening/ stops it from being produced.
Neurone = A collection of nerve cells that carry an electrical impulse.
Postsynaptic = The neurone after the synapse.
Presynaptic = The neurone before the synapse.
Receptor = Something that is triggered as a result of a change in environment.
Stimulates = to action something.
Stimuli = a change in environment.
Synapse = A gap between two neurones that stops an electrical impulse traveling backwards.
A sensory organ is an organ that detects stimuli. A stimuli is a change in your environment which you may need to react to. For example holding your hand near a hot pan. Your body constantly scans the local environment as a defence mechanism, meaning you can react quicker. You have 5 different sense organs which are: Eyes, Ears, Nose, Tongue and the biggest of them all the skin. Sense organs are able to detect at least one of these: Light, Sound, Touch, Pain, Temperature.
How it works .
The nervous system starts with a stimuli being picked up by a receptor. Receptor and Sensory organ are different. The sensory organ is what contains the receptors. Once the receptor detects a stimuli it sends an electrical impulse along the sensory neurone. A neurone is a collection of nerve cells that transmit the information across the Nervous System.
The sensory neurone then leads to the relay neurone and are linked by a synapse. The relay neurone is connected to the motor neurone by another synapse. The motor neurone is connected the effector. An effector is something that is triggered as a result of the electrical impulse. This covers from muscles contracting to glands producing hormones. The Nervous system doesn't bypass the brain and the entire process takes milliseconds.
The synapse is a junction between two neurones. The electrical impulse comes along the presynaptic neurone into the synapse. This triggers neurotransmitters that diffuse across the gap. When a high enough concentration reaches the postsynaptic neurone an electrical impulse is sent down the postsynaptic neurone. A synapse is the joint and stops the electrical impulse from travelling backwards in the system.
Hormones are chemicals that are secreted by glands around the body. For example the purity gland produces the hormone, amongst others, FSH. Hormones travel in the blood stream to the target organs and regulate the function of cells.
The Menstrual Cycle
Stage one is when the bleeding starts as the uterus lining breaks down for about 4 days,
The lining starts building up again (Days 4-14). The lining builds into a thick spongy layer full of blood vessels so the uterus can support a fertilised egg.
An Egg cell is released form the ovaries. (Released on day 14)
The wall is then maintained for about 14 days. If no fertilised egg is found the uterus lining starts to break down bringing the cycle back around to day one.
FSH (Follicle Stimulating Hormone):
- Produced in the Pituitary Gland.
- Stimulated the maturation of the egg cell.
- Stimulates the production of Oestrogen.
- Produced in the Ovaries .
- Inhibits the production of FSH
- Stimulates the production of LH
LH (Luteinising Hormone):
- Produced in the Purity Gland.
- Stimulates the release of egg cell.
- Inhibits the production of Oestrogen.
Plant Hormones (Tropism)
Auxin is the plant hormone that controls growth near the tips of shoots and roots. Auxin controls the growth of the plant in accordance to light (Phototropism) and Gravity (geotropism). Auxin is made in the tip of the plant and is distributed downwards in the elongation process, which occurs in the cells just behind the tip. Extra Auxin stimulates growth and inhibits the growth of roots, giving the desired effects,.
Shoots grow towards light:
When the tip of a shoot is exposed to light, more auxin collates on the side of the shade. This makes the cells elongate faster on the shaded side causing the shoot to bend towards the light.
Shoots Grow away from gravity:
When a shoot is growing sideways, the gravity causes all the Auxin to collate at the bottom of the tip. Then as the Auxin elongates the shoot grows upwards as the underside is growing faster.
Roots grow towards gravity:
When a root is growing sideways the root will have more auxin on the lower side but in a root extra Auxin inhibits growth meaning the cells elongate faster on the top causing the root to bend downwards.
Roots grow towards moisture:
An uneven amount of moisture produces more Auxin in the root. This inhibits the growth on the other side causing the root to bend towards the moisture.
This topic is covered by the Code Bi.15. and there is resources available in the THS store for this topic. Student worksheets are free and we have a range of quality lessons available for purchase, these include lesson plans, activity's and presentations for each lesson.