Coordination and Response Flashcards
What is a tropism?
A directional response by plants to stimuli in their environment (positive=towards and negative=away)
What is the geotrophic response of roots?
Positive geotropism (towards gravity)
What is the geotrophic response of stems?
Negative geotropism (away from gravity)
Describe the phototrophic response of stems
The stem of a plant grows towards light (positive phototropism). Plants grow towards the light through the use of the hormone auxin. Auxin diffuses towards the shaded sign of a plant, causing cell elongation.
What is a stimulus?
A change in an organism’s environment
What is the sequence of events leading up to a response?
1) stimulus
2) receptor
3) coordination
4) effector
5) response
What is transduction?
The change of energy from one form to another (all receptors are transducers)
What is the role of receptors?
To detect the stimulus by changing its energy into the electrical energy of impulse
What is the difference between nervous and hormonal communication?
1) response is more short lived in nervous system compared to the hormonal system
2) nervous system works by nerve impulses transmitted through nerve cells whereas hormonal system operates by hormones transmitted through the blood
3) nerve impulses travel faster than hormones
4) nervous system has a localised effect whereas hormones are more widespread
What does the central nervous system (CNS) consist of?
The brain and the spinal cord
What does a motor neurone do?
Transmits nerve impulses from the CNS to the muscles and glands
What does a sensory neurone do?
Transmits nerve impulses from the muscles and glands to the CNS
What are dendrons?
Cytoplasmic extensions of the neurone cell body
What are dendrites?
Finer cytoplasmic extensions of the dense on which can join to other neurones
What is the myelin sheath?
Insulating fatty layer that covers the axon and speeds up the conduction of impulses
What are reflex arcs?
Involuntary, fast, preprogrammed responses to stimuli
What is the source of ADH?
Pituitary gland
What is the source of adrenaline?
Adrenal glands
What is the source of insulin?
Pancreas
What is the source of glucagon?
Pancreas
What is the source of testosterone?
Testes
What is the source of progesterone?
Ovaries
What is the source of oestrogen?
Ovaries
What is the role of ADH?
Control the water content of the blood
What is the role of adrenaline?
Prepare the body for action
What is the role of insulin?
Lower blood glucose levels
What is the role of glucagon?
Increase blood glucose levels
What is the role of testosterone?
Controls the développement of male secondary sexual characteristics
What is the role of progesterone?
Regulates the mistrial cycle
What is the role of oestrogen?
Controls the development of female secondary sexual characteristics
What is the effect of adrenaline?
prepares the body for action by…
1) Increasing the breathing rate so get more oxygen into the body and remove excess carbon dioxide
2) Increasing the heart rate to supply the muscles with more oxygen and glucose for respiration and remove waste products
3) Diverting blood from the digestive system to the muscles
4) Converting glycogen in the liver into glucose in the blood
5) Increasing mental awareness so reactions are faster
6) Dilating pupils so more sensitive to movement
What is the effect of insulin?
Insulin decreases blood sugar levels by turning glucose into glycogen, which is stored in the muscles and the liver
What is the effect of glucagon?
Glucagon raises blood sugar levels by turning stored glycogen into glucose
describe the process of a reflex arc
1) Stimulus detected by receptors in skin
2) Impulse enters CNS through sensory neurone in the dorsal root
3) In the spinal cord the sensory neurone connects to a relay neurone via a synapse
4) Relay neurone connects with motor neurone bypassing the brain
5) Motor neurone leaves the spinal cord via the ventral root
6) Impulse causes muscle to contract
describe the process of nerve impulses travelling through synapses
1) Impulse arrives down the axon of the first neurone
2) Neurotransmitters diffuse across the synapse
3) Neurotransmitters attach to receptors on the membrane of the second neurone
4) New impulse started in second neurone
5) Neurotransmitter broken down by an enzyme from the second neurone
what are rods?
cells in the retina which work in dim light to produce black and white images
what are cones?
cells in the retina which work in bright light to produce colour images
What is the function of the iris?
Expands and contracts to control the amount of light entering the eye
What is the function of the pupil?
Circular opening which lets light into the eye
What is the function of the cornea?
Transparent layer responsible for most of the refraction of light rays
What is the function of the sclera?
Tough outer coat that protects the eye
What is the function of the Lena?
Focuses light onto the retina
What is the function of the choroid?
Reduces reflections inside the eye as darkly coloured
What is the function of the retina?
Layer of the eye that contains light sensitive cells (rods and cones) which detect light
What is the function of the optic nerve?
Carries nerve impulses to the brain
What is the fovea?
Area of the retina with the highest concentration of rods and cones
What are the similarities between the mechanisms involved in reflexes in animals and tropisms in plants?
1) involve chemicals
2) involve receptors
3) involve effectors
What are the differences between the mechanisms involved in reflexes in animals and tropisms in plants?
1) reflex involves electrical impulses and tropism involves hormones
2) animal is fast and plant is slow
3) muscle contraction vs growth response
What is meant by the term hormone?
1) released from gland
2) travels in blood
3) to target cells/organs
4) effect/causes change
describe accommodation for a near object
Lens becomes thicker as…
1) cilary muscles contract
2) suspensory ligaments relax
describe accommodation for far away objects
Lens becomes thinner as…
1) cilary muscles relax
2) suspensory muscles contract
what happens to the pupil in bright light?
the pupil constricts as…
1) circular muscles in the iris contract
2) radial muscles in the iris relax
what happens to the pupil in dim light?
the pupil dilates as the iris relaxes as…
1) circular muscles in the iris relax
2) radial muscles in the iris contract
