Hormones Revision Notes
Two communication systems used by the human body to respond to externals
stimuli are the nervous system and the hormone system.
The nervous system is many electrical messages sent along nerves to different
parts of the body.
Hormones are chemical messages sent around the blood to organs.
Hormones are slower but they also last much longer.
The central nervous system consists of the brain and the spinal cord. They are the
control between receptor the effectors.
Impulses are carried along by neurons. They have branched ends to spread out
the impulse. Covered by the insulator called myelin.
Neurones don’t touch each other. There is a gap called a synapse. A chemical is
released into the synapse when an impulse reaches it and then when it reaches
the next neurone in a high enough concentration, a new impulse is triggered.
The eye is a sensory organ and its component parts include the conjunctiva,
cornea, pupil, iris, lens, aqueous and vitreous humours, retina and optic nerve.
The retina contains the receptor cells called rods (black and white) and cones
(colour).
Accommodation is the process of producing a fine focused image on the retina
carried out by the action of ciliary muscles and suspensory ligaments on the lens.
A voluntary action is carried out consciously to carry out a response. This involves
the brain as a co-ordinating and decision-making centre. Spinal reflex actions are
automatic and quick. They speed up the response time by by-passing the brain
and the spinal cord acts as the coordinator. The impulse is passed directly from a
sensory neurone - association neurone - motor neurone
Homeostasis is the process by which the body maintains a constant internal
environment.
Insulin is produced in response to blood glucose levels.
Osmoregulation is a homeostatic process in the body. It controls the amount of
water in the blood and other body fluids.
Water is gained by the body mainly via drinking, eating and cell respiration.
Water is lost by the body mainly via urine, sweating, breathing and faeces.
Antidiuretic hormone causes the kidney to reabsorb more water from urine, thus
reducing its volume.
Plants respond to external stimuli using hormones; one of which is called auxin.
Phototropism is in response to the uneven distribution of auxin, which promotes
cell elongation and thus growth in the shaded side of a plant.
Two communication systems used by the human body to respond to externals
stimuli are the nervous system and the hormone system.
The nervous system is many electrical messages sent along nerves to different
parts of the body.
Hormones are chemical messages sent around the blood to organs.
Hormones are slower but they also last much longer.
The central nervous system consists of the brain and the spinal cord. They are the
control between receptor the effectors.
Impulses are carried along by neurons. They have branched ends to spread out
the impulse. Covered by the insulator called myelin.
Neurones don’t touch each other. There is a gap called a synapse. A chemical is
released into the synapse when an impulse reaches it and then when it reaches
the next neurone in a high enough concentration, a new impulse is triggered.
The eye is a sensory organ and its component parts include the conjunctiva,
cornea, pupil, iris, lens, aqueous and vitreous humours, retina and optic nerve.
The retina contains the receptor cells called rods (black and white) and cones
(colour).
Accommodation is the process of producing a fine focused image on the retina
carried out by the action of ciliary muscles and suspensory ligaments on the lens.
A voluntary action is carried out consciously to carry out a response. This involves
the brain as a co-ordinating and decision-making centre. Spinal reflex actions are
automatic and quick. They speed up the response time by by-passing the brain
and the spinal cord acts as the coordinator. The impulse is passed directly from a
sensory neurone - association neurone - motor neurone
Homeostasis is the process by which the body maintains a constant internal
environment.
Insulin is produced in response to blood glucose levels.
Osmoregulation is a homeostatic process in the body. It controls the amount of
water in the blood and other body fluids.
Water is gained by the body mainly via drinking, eating and cell respiration.
Water is lost by the body mainly via urine, sweating, breathing and faeces.
Antidiuretic hormone causes the kidney to reabsorb more water from urine, thus
reducing its volume.
Plants respond to external stimuli using hormones; one of which is called auxin.
Phototropism is in response to the uneven distribution of auxin, which promotes
cell elongation and thus growth in the shaded side of a plant.
