coordination and response Flashcards
define homeostasis
the maintenance of a constant internal environment.
what does a co-ordinated response require?
a stimulus, a receptor and an effector
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Explain how auxins cause a positive phototropism.
- Auxin diffuses from the tip to the shaded side, causing elongation
- Therefore the shaded side is longer, causing the stem to bend towards the light.
How do shoots respond to gravity?
They grow up (negative geotropism).
When a plant is laid on its side, the auxins produced collect in the lower side of the stem. Auxins sped up growth in the lower side of the shoot, so the shoot curves up.
How do roots respond to gravity?
They grow down (positive geotropism)
If a plant is laid on its side, the auxins produced collect in the lower side of the root. Auxins slow down growth on the lower side of the root, so the root curves down.
describe nervous coordination
coordination from a nervous system involving a network of nerve cells that carry impulses between parts of body.
describe hormonal coordination
coordination from an endocrine system involving glands that produce and secrete hormones to stimulate change in the body
describe two differences between hormonal and nervous coordination
- Nervous communication is electrical, hormonal communication is chemical
- Nervous Communication is faster, hormonal communication is slower
what does the central nervous system consist of?
the brain and the spinal cord
give two adaptations of a nerve cell
- long fibre (axon) which is insulated by a fatty sheath
- tiny branches (dendrons) which branch further as dendrites at each end
Name the neurones going into the coordination centres
Sensory neurones
Name the neurones going out of the coordination centre
Motor neurones
Describe how a normal response works
Stimulus -> receptor -> (sensory neurone) -> coordination centre -> (motor neurone) -> effector -> response
What is a synapse
The gap between where one neurone ends and another begins
Describe the 4 stages of electrical impulses crossing synapses.
- An impulse arrives at the synapse, vesicles containing neurotransmitters move to the membrane.
- The vesicles release the neurotransmitters into the gap.
- The neurotransmitter crosses the synapse and binds to receptors in the end of the next neurone, beginning a new electrical impulse
- The neurotransmitter is broken down by enzymes in the second neurone
Describe the reflex arc
- Sensory receptors
- Impulse in sensory neurone travels to grey matter of spinal cord
- Sensory -> relay neurone
- Relay -> motor
- Effector
Function of cornea.
The transparent lens that refracts light as it enters the eye.
Function of iris.
Controls how much light enters the pupil.
Function of lens.
The transparent disc that can change shape to focus light onto the retina.
Function of the pupil.
The hole that allows light to enter the eye.
Function of the retina.
Contains light receptor cells (rods which detect light intensity and cones which detect colour)
Function of the optic nerve.
A sensory neurone that carries impulses between the eye and the brain.
What happens to the radial muscles when there is dark light/ bright light?
Dark light= contracted
Bright light= relaxed
What happens to the circular muscles when in dark light/ bright light?
Dark light= relaxed
Bright light= contracted
What happens to the pupil size in dark light/ bright light?
Dark light= wide
Bright light= narrow
Definition of accommodation
The process of changing the shape of the lens to focus on near or distant objects
What happens to -ciliary muscles - suspensory ligaments -lens When an object is close by?
- ciliary muscles: contracted
- suspensory ligaments: slack
- lens: fatter
What happens to - ciliary muscles - suspensory ligaments - lens When an object is far away?
- ciliary muscles: relaxed
- suspensory ligaments: pulled tight
- lens: thinner
How does refraction of light change when an object is close by/ far away?
Close by: refraction of light increases.
Far away: refraction of light is less.
How do the light rays change when an object is close by/ far away?
Close by: light rays are diverging
Far away: light rays are parallel.
Definition of myopia (short sightedness)
You can see objects at a short distance away, but struggle to see objects at a distance.
Why does myopia occur?
The eyeball is too long for the strength of the lens
The cornea is too sharply curved.
When the eye attempts to produce and image, it falls short of the retina.
How can you correct myopia?
Myopia can be corrected by a concave lens which diverges the light rays before they reach/enter the eye.
Definition of hyperopia (long sightedness)
You can see objects at long distances away, but struggle to see near objects.
When does hyperopia happen?
It happens when the lens is too weak because it is not thick enough.
When the eyeball is too short.
The cornea is not curved enough.
When the eye attempts to produce an image, it falls behind the retina.
How can hyperopia be corrected?
It can be corrected by a x lens which diverges the light rays before they reach/ enter the eye.
3 things that happen when body is too cold
Vasoconstriction, prevents heat from radiating to surroundings
Hair erector muscles contract, creating insulation layer
Muscles shiver, forcing body to produce (heat) energy
3 things that happen when body is too hot
Sweating, cools down the skin.
Vasodilation, allows heat to radiate from blood to surroundings.
Hair erector muscles relax.
State the source of adrenaline
The adrenal gland, when ACTH is released by the pituitary gland.
Give 3 effects of adrenaline
- increased heart rate + breathing rate
- initiates conversion of glycogen into glucose in the liver
- blood is diverted from the digestive systems to the muscles in the limbs
State the source of insulin
Pancreas
What is the role and effect of insulin.
To restore normal glucose levels when they are too high by stimulating the liver to convert glucose into glycogen.
Why is adrenaline not an example of negative feedback?
As adrenaline does is not reverting conditions back to normal/optimal levels.
Define a hormone
A chemical messenger released by glands into the blood and carried to a target organ
give the source, role and effect of testosterone
- testes
- main sex hormone in males
- Development of secondary sexual characteristics in males
give the source, role, and effect of progesterone
- ovaries
- maintains pregnancy
- Maintains the uterus lining to cushion fertilized egg and allow it to develop
give the source, role and effect of oestrogen
- ovaries
- main sex hormone in females
- Development of secondary sexual characteristics in females and controls menstrual cycle
give the source, role and effect of ADH
- pituitary gland
- Controlling the water content of the blood
- Increases reabsorption of water from urine in the collecting ducts of the kidneys
give the source, role and effect of FSH
- pituitary gland
- Causes ovary to develop a mature egg cell
- Stimulates the development of egg cells in the ovary and the release of oestrogen
give the source, role and effect of LH
- pituitary gland
- Causes ovary to release a mature egg cell
- Stimulates the release of an egg cell from the ovary (ovulation) and the release of progesterone
