WEAKNESSES - Coordination and Response

what is the CNS made of?

brain and spinal cord

what reflex is an automatic response?

withdrawal reflex

how do neurons transmit information?

high speed electrical impulses

iris response to bright light

CCRR

circular contract

radial relax

iris response in dim light

CRRC

circular relax

radial contract

what is accommodation?

changing the shape of the lens to focus light on the retina

how does the eye focus light for distant objects

• ciliary relax

• suspensory contract

• lens thinner

• refracts light less

how does the eye focus light for near objects?

• ciliary contract

• suspensory relax

• lens fatter

• refracts light more

define reflex

automatic responses to stimuli

define hormone

chemical messengers transmitted in the blood

differences between nervous and hormonal responses (5)

• hormones produced in glands, nervous from stimuli

• hormones are chemicals, nervous use electrical impulses

• hormones are slow, nervous are rapid

• hormones are long lasting, nervous are shorter

• hormones target a general area, nervous target specific places

define homeostasis

maintenance of a constant internal environment

what does a coordinated response require?

stimulus

receptor

effector

examples of homeostasis (2)

• body temperature

• water content

why do smaller organism cool down/warm up quicker? (3)

• larger SA to volume ratio

• gain/lose heat faster

• greater area for heat transfer

examples of plants responding to their environment (3)

• grow towards light = ↑photosynthesis

• gravity = roots grown down

• climbing plants have a sense of touch so they can climb things and reach sunlight

how do auxins move throughout the plant?

dissolved in water

how do shoots respond to light?

POSITIVELY PHOTOTROPHIC

• auxin moves to side of shoot in shade

• elongates the cells on the shaded side

• the shoot bends towards the light

how do shoots respond to gravity?

NEGATIVELY GEOTROPHIC

• on a sideways shoot, gravity causes auxin to collect on the lower side

• cell elongation so the shoot bends upwards

how do roots repond to light?

NEGATIVELY PHOTOTROPHIC

• in light auxin accumulates on the shaded side

• auxin inhibits cell growth so the cells on top grow faster and the root bend down

how do roots respond to gravity?

POSITIVELY GEOTROPHIC

• roots growing sideways will cause auxin to accumulate on the lower side

• auxin inhibits cell growth on the lower side so the top cells grow faster

• the root bend downwards.