Nerve and hormones Flashcards
What does the nervous system enable humans to do?
It enables humans to react to their surroundings and coordinate their behaviour.
What is a stimulus?
It is a change the the environment, which you may need to react to.
What are receptors?
They are a group of cells that are sensitive to a stimulus.
Name receptor and the stimuli they detect.
1) Receptors in the eyes - sensitive to light
2) Receptors in the ears - sensitive to sound, changes in position and enable us to keep our balance
3) Receptors on the tongue and in the nose - sensitive to chemicals and enable us to taste and to smell
4) Receptors in the skin - sensitive to touch, pressure, pain and to temperature changes
What is the central nervous system?
It is where all the information from the sense organs is sent, and where reflexes actions are coordinated.
It consists of the brain and spinal cord ONLY.
What are sensory neurons?
They are the nerve cells that carry signals as electrical impulses from the receptors in the sense organs to the CNS.
What are relay neurons?
They are the nerve cells that carry signals from the sensory neuron to the motor neuron inside the CNS.
What are the motor neurons?
They are the nerve cells that carry signals from the CNS to the effector.
What is an effector?
2 examples.
An effector brings about a response e.g.
- Muscle contract
- Glands secrete hormones.
What are synapses and how are nerve impulses transferred along it?
Synapses are a small gap in which two neurons connect
The nerve impulse is transferred by chemicals (neurotransmitters) which diffuse across the gap.
These chemicals then set off a new electrical signal in the next neuron.
What is meant by a reflex?
What is the benefit of reflexes?
Reflexes are rapid, automatics responses.
The benefit is that they can protect us from danger.
Stages in a simple reflex action.
- Impulses from a receptor pass along a sensory neurone to the central nervous system
- At a junction (synapse) between a sensory neurone and a relay neurone in the central nervous system, a chemical is released that causes an impulse to be sent along a relay neurone
- A chemical is then released at the synapse between a relay neurone and motor neurone in the central nervous system, causing impulses to be sent along a motor neurone to the organ (the effector) that brings about the response
- The effector is either a muscle or a gland, a muscle responds by contracting and a gland responds by releasing (secreting) chemical substances.
One word pathway of a reflex arc.
Stimulus—> Receptor—> Sensory neurone—> Relay neurone—> Motor neurone—> Effector—> Response.
What are hormones?
Hormones are chemical messengers which travel in the blood to activate target cells.
What are hormones secreted by?
Hormones are secreted by various glands such as the pituitary gland and the ovaries.
What is FSH?
Follicle stimulating hormone
- Secreted by the pituitary gland
- Causes eggs to mature in the ovaries.
- Stimulates the ovaries to produce oestrogen
What is oestrogen?
oestrogen
- Secreted by the ovaries
- Stimulates pituitary gland to produce LH
- Inhibits the further production of FSH
What is LH?
Luteinising hormone
- Produced in the pituitary gland
- Stimulates the release of eggs from the ovary around the middle of the menstrual cycle.
What does oral contraceptives contain?
- They contain hormones to inhibit FSH production so that no eggs mature.
- They may also contain oestrogen and progesterone to inhibit egg maturation.
How does oestrogen in the pill reduce fertility?
If oestrogen is taken everyday to keep the levels of it permanently high, it inhibits the production of FSH, and after a while egg development and production stops.
How does progesterone in the pill reduce fertility?
Progesterone stimulates the production of think cervical mucus which prevents any sperm getting through and reaching the egg.
Describe the problems with early contraceptive pills and how these were solved in modern versions.
Early contraceptive pills contained high doses of oestrogen and caused side effects.
Modern pills contain much lower doses of oestrogen or progesterone only. These have ewer side effects.
How can FSH and LH increase fertility?
Some women have levels of FSH that are too low to cause their eggs to mature. This means no eggs are released and the woman can’t get pregnant.
The hormones FSH and LH can be injected to stimulate egg release in their ovaries.
What does IFV involve?
IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs. The eggs are collected from the mother and fertilised by sperm from the father. The fertilised eggs develop into embryos. At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).
