B1.2 - The Nervous System Flashcards
What does the nervous system allow humans to do?
React to their surroundings and coordinate their behaviour.
What are receptors?
Cells that detect stimuli (changes in the environment)
Give 3 examples of receptors and the stimui they detect:
- receptors in the eyes are sensitive to light
- receptors in the ears are sensitive to sound
- receptors in the ear are sensitive to changes in position and balance
- receptors in the skin are sensitive to touch, pressure, pain and temperature
What is the structure of a light receptor cell like?
They have a nucleus, cytoplasm and cell membrane like most animal cells
How does information form receptors reach the brain?
It passes along neurones in nerves
What are reflex actions?
They are automatic and rapid, and often involve sensory, relay and motor neurones.
How are impulses form a receptor sent to the central nervous system?
Along a sensory neurone
How is the impulse passed from a sensory neurone to a relay neurone?
Across a synapse, a chemical is diffused across it which causes an impulse to be sent down the relay neurone
How does the impulse reach the effector (a muscle or gland)?
A chemical is diffused across the synapse between a relay neurone and motor neurone in the CNS, causing impulses to be sent along the motor neurone to the effector
How does the effector respond to the impulse?
A muscle responds y contracting, and a gland responds by releasing chemical substances
How does water enter/leave the body?
Water leaves the body via the lungs when we breathe out and via the skin when we sweat to cool us down, and excess water is lost via the kidneys in the urine
Ho do ions enter/leave the body?
Ions are lost via the skin when we seat and excess ions are lost via the kidneys in urine
Why does temperature need to be controlled in the body?
To maintain the temperature at which enzymes work best
Why do blood sugar levels need to be maintained within the body?
To provide the cells with a constant supply of sugar
What are chemical processes in the body coordinted by?
Hormones
How do hormones travel in the body?
Hormones are secreted by glands and are usually transported to their target organs by the bloodstream
How do hormone effect a woman’s body once a month?
Eggs being released from her ovaries and the changes in the thickness of the lining of her womb are controlled by hormones secreted form the pituitary gland and the ovaries
What is FSH?
The follicle stimulating hormone, it causes eggs to mature in the ovaries. It also stimulates the ovaries to produce hormones including oestrogen
What is LH?
The lutenising hormone, it stimulates the release of eggs from the ovaries
What does oestrogen do?
It inhibits the further production of FSH
What do oral contraceptive pills often contain?
Oestrogen and progesterone to inhibit egg maturation
What did the first birth control pills contain?
large amounts of oestrogen. This resulted in women suffering significant side effects
What benefit do progesterone only pills have?
They come with less side effects
What can be in a ‘fertility drug’
FSH and LH
What effect can a fertility drug have?
For women whos levels of FSH are too low to stimulate eggs to mature, the drug can help her to concieve
What can be done during IVF (In Vitro Fertilisation)?
The eggs are collected from the mother after she has been given the fertility drug, and fertilised by the father’s sperm. The fertilised eggs develop into embryos. Once they are balls of cells, one or two are inserted into the mother.
What 3 things are plants sensitive to?
light, moisture and gravity
How do plants coordinate and control growth?
Auxin, a hormone, controls phototropism, gravitropism and geotropsim.
How do plants respond to light, gravity or moisture?
They can be seen to grown towards the factor, due to unequal distribution of hormones, causing unequal growth rates
How can plant hormones be used in agriculture and horticulture?
Plant growth hormones, as weed killers and rooting hormones
