Structure and Functions in Living Organisms - Coordination and Response Flashcards
how are organisms able to repsond to changes in their environment?
- all living organisms need to respond to changes in environment for survival
- the nervous system allows body to respond to changes in environment
what factors are needed for an organism to respond to environment?
- a stimuli
- a receptor (cell that detects changes in the environment)
- an effector (part of body that carries out response)
what is homeostasis?
maintenance of a constant internal environment#
for example: body water content and body temperature
what does a coordinated response require?
a stimulus, a receptor and an effector
do plants respond to stimuli?
yes, as they are living organisms
for example: geotropism and phototropism
what is the geotrophic response of plant stems?
- auxin produced at the tip accumulates on the underside of the stem due to gravity
- auxin promotes the growth of cells in the stem, so cells on the underside elongates. cells on the upperside are unaffected
- as a result, the stem will grow upwards
what is the geotrophic response of plant roots?
- auxin produced at the tip accumulates on the underside of the root due to gravity
- auxin inhibits the growth of cells in the root, so cells on the underside will not grow. cells on the upperside will continue to grow
- as a result, the root will grow downwards
what is the phototrophic response of plant stems?
- auxin produced at the tip will accumulate at the shaded side
- auxin promotes the growth of cells in the stem, so cells on the shaded side elongates. cells on the unshaded side are unaffected
- as a result, the stem will grow towards the light
what is the phototrophic response of plant roots?
- auxin produced at the tip will accumulate at the shaded side
- auxin inhibits the growth of cells in the root, so cells on the shaded side don’t grow. cells on the unshaded side continue to grow
- as a result, the root will grow away from the light
what is nervous coordination?
nervous system comprising a network of nerve cells that carry impulses between parts of body
what is hormonal coordination?
endocrine system comprising glands that produce and secrete hormones to stimulate change in the body
what are the differences between nervous and hormonal coordination?
- nervous communication is electrical, while hormonal communication is chemical
- nervous communication is faster, while hormonal communication is slower
- nervous communication is short - lived, while hormonal communication is long - lived
what does the central nervous system contain?
the brain and the spinal cord linked to the sense organs by nerves
what does stimulation of receptors result in?
electrical impulses are sent along the nerves into and out of the central nervous system, resulting in rapid responses
what is the role of neurotransmitters at synapses?
- when an electrical impulse reaches a synapse, neurotransmitters are released
- neurotransmitters diffuse across the synapse and bind to receptors on the membrane of the neuron
what is the structure of a reflex arc?
stimulus, receptor, sensory neurone, cns, motor neurone, effector, response
what core structures does the eye contain?
the cornea, the iris, the lens, the retina, the optic nerve, the pupil and the ciliary muscles
what is the cornea?
transparent convex lens that refracts light
what is the iris?
a pigmented membrane that controls the diameter and size of pupil to alter the quantity of light reaching the retina
what is the lens?
transparent disc that changes shape to focus light onto the retina
what is the retina?
light-sensitive nerve tissue containing rods and cones to convert light into electrical impulses to be interpreted by the brain for visual recognition
what is the optic nerve?
a nerve located in the back of the eye that contains sensory neurons to send electrical impulses to be interpreted by the brain for visual recognition
what is the pupil?
an opening in the centre of Iris that allows light to enter the eye
what are the ciliary muscles?
circular muscle surrounding the lens that that contracts and relaxes to adjust the thickness of lens
