2-Nerves & Hormones Flashcards
What does the nervous system allow organisms to do?
React to their surroundings.
What does the nervous system consist of?
The brain, the spinal cord, the neurones and receptors.
How does the nervous system work?
Information from receptors passes along sensory and relay neurones to the brain. The brain coordinates a response, which is carried out by an effector through motor neurones.
What can the effector be?
A muscle, which contracts in response.
A gland, which releases chemicals in response.
What are the three types of neurone?
Motor neurone.
Sensory neurone.
Relay neurone.
How does the impulse travel in a motor neurone?
Away from cell body.
How does the impulse travel in a sensory neurone?
Towards cell body.
How does the impulse travel in a relay neurone?
First towards then away from cell body.
What are neurones?
Specially adapted cells that can carry an electrical signal.
How is a neurone adapted to the body?
They are elongated to make connections between parts of the body.
They have branched endings so a single neurone can act on many muscle fibres.
Cell body has many connections that allow communication with other neurones.
What is the gap between neurones called?
A synapse.
How do neurones transfer impulses to other neurones?
Electrical impulse reaches gap via neurone A.
A chemical transmitter is released which activates receptors on neurone B.
The chemical transmitter is then destroyed.
What do stimuli do receptors detect?
Light-In the eyes
Sound-In the ears
Change if position-In the ears (balance)
Taste-In the tongue, sensitive to chemicals
Smell-In the nose, sensitive to chemicals
Touch,Pressure, Pain & Temperature-In the skin
Why do we have a reflex action?
As conscious action is sometimes too slow to prevent harm to the body.
How does a reflex action work?
- A receptor is stimulated by the stimulus (eg. Hot plate).
- Impulses pass along a sensory neurone into the spinal cord.
The sensory neurone synapses with a relay neurone, by-passing the brain. A chemical is released at the synapse which causes an impulse to be sent along a relay neurone. - A chemical is released when the relay neurone synapses the motor neurone. This causes an impulse to be sent down the motor neurone.
- This reaches the effector (eg. Muscles) causing them to react (eg. Move hand from hot plate).
What internal conditions need to be kept relatively constant?
Body temperature and the levels of water, salts (ions) and blood sugar.
How are many process within the body coordinated?
Using hormones.
What are hormones?
Chemicals, produced by glands, which are transported to their target organs through the bloodstream.
What do hormones that women produce cause?
The monthly release of an egg from her ovaries.
Changes in the thickness of the lining of her womb.
Where are the hormones that women produce produced?
The pituitary gland and the ovaries.
How is a woman’s fertility controlled by the body?
FSH (Follicle Stimulating Hormone):
Secreted by the pituitary gland, causes eggs to mature in the ovaries and causes ovaries to produce hormones, including oestrogen.
Oestrogen:
Produced in the ovaries, inhibits production of FSH and causes production of LH.
LH (Luteinising Hormone):
Produced in pituitary gland, stimulates release of an egg from the ovaries in the middle of the menstrual cycle.
How can fertility be artificially increased?
LH & FSH can be given in a fertility drug for women whose FSH levels are too low to stimulate eggs to mature.
How is IVF (In Vitro Fertilisation) done?
Several eggs stimulated to mature. They’re collected from the mother, are fertilised by the father’s sperm and develop into embryos. At this stage, when they’re tiny balls of cells, 1 or 2 embryos are inserted into the mother’s uterus (womb).
How can fertility be artificially decreased?
Contain hormones (oestrogen & progesterone) that inhibit FSH production so no eggs mature.