Unit 1: Chapter 2 - Coordination and Control Flashcards
Reflex Actions
What are reflexes for?
How do reflexes work?
What are synapses?
How do they work?
Reflexes are important to avoid danger take care of basic functions such as breathing. These are automatic responses.
Reflexes involve three different neurons:
- Sensory Neuron
- Relay Neuron (in the CNS and grey matter)
- Motor Neuron
These neurons make up the reflex arc.
HOW DO SYNAPSES WORK?
Nerves are not joined up. There are junctions (gaps) between them called synapses.
The impulses are converted to chemicals that are released through the gap and meet the receptor site. Chemicals attatch to the surface of the next neuron and set up a new electrical impulse.
Stimulus> Receptor> Coordinator> Effector> Response
Hormones and Menstrual Cycle
What is the menstrual cycle?
What hormones are involved?
The menstrual cycle lasts about 28 days and is controlled by hormones. Hormones can act quickly but the effect is slow and long-lasting.
FSH (Pituitary gland) - Follicle stimulating hormone matures eggs in ovaries that takes about 12 days.
Oestrogen (Ovaries) - stimulates lining of womb. It inhibits production of FSH.
LH (Pituitary gland) - releases egg at 12th - 16th day.
Progesterone (Placenta) - encourages growth of milk producing glands.
If pregnancy occurs, oestrogen and progesterone levels remain high.
Artificial control of hormones
What are contraceptive pills?
What is IVF?
Contraceptive pills contain oestrogen (sometimes progesterone) to inhibit production of FSH.
A correct amount of oestrogen produces less side effects.
WHAT IS IVF?
IVF (in vitro fertilisation) can help women who lack female hormones or women who have damaged fallopian tubes. Conception usually takes place in the fallopian tubes.
FSH can be injected to collect as many eggs as possible. And LH is alsp given. The eggs are collected and can be fertilised ouside the uterus. They can then be implanted back into the uterus. 1 or 2 is usually implanted back in to ensure at least one will grow and develop.
IVF is expensive and not always successful.
Homeostasis
Keeping the processes in your body is known as homeostasis. It involves the nervous system, hormone system and many of body organs.
- Kidneys control the salt and water levels and is controlled by nerves and hormones.
- your deep core body temperature is at 37C so you enzymes work effectively. Your nervous system is responsible for the body temperature.
- The pancreas secretes insulin to keep the concentration of glucose in blood constant. This means body cells can be provided with a constant supply and energy.
If any of these processes stop working, you would die.
Hormlmes and the control of plant hormones
What are plant hormones used for?
Plants are sensitive to light, water and gravity.
Plants ROOTS are sensitibe to water and gravity.
Plant SHOOTS are sensitive to gravity and light.
These stimuli and controlled by plant hormone called AUXIN. The response happens when there is an uneven distribution of the hormone.
In phototropism (light), the shoot will bend towards the light. Auxin moves to the side of the shoot on the unlit side causing and bend of the shoot. When light falls evenly on the shoot, the level of auxins will balance out.
Similarly, in the roots when gravitropism occurs, auxin gathers on the lower side, causing a bend.
USING PLANT HORMONES
Gardeners can take cutting to make identical plants. Plant hormones are used as rooting powder and stimulates growth of roots.
High dose of plant hormones can be used as weed killers. A rapid, uncontrolled growth kills them. Narrow leaved plants such as grass are not affected so lawn grows well.
Nervous system
What is it?
How does it work?
Your nervous system responds to changes (stimuli) with receptors.
Receptors are found usually in sense organs such as eyes, skin, ears and nose.
HOW DOES IT WORK?
It works by sending (electrical) impulses down neurons which make up nerves. These impulses are received by the central nervous system (CNS) i.e the brain or spinal cord. From the CNS, it travels to the MOTOR NEURON to the EFFECTOR ORGANS.
Receptor> Sensory Neuron> CNS>
Motor Neuron> Effector
