plant hormones, reflex arcs, thermoregulation

Question 1

Hypothalamus

Answer 1

controls body temp

Question 2

CNS

Answer 2

Central Nervous System = the spinal cord and brain

Question 3

PNS

Answer 3

Peripheral Nervous System = the collection of neurons connected to the CNS

Question 4

Order of human nervous system

Answer 4

stimulus - cooking food
receptor - nose
CNS
effector - salivary glands
response - produce saliva

Question 5

Neurotransmitter

Answer 5

A chemical that passes messages around the brain from neuron to neuron

Question 6

thermoregulation

Answer 6

how our body controls our temperature

Question 7

how is our body temperature detected

Answer 7

receptors in our hypothalamus detect it

Question 8

ectotherms

Answer 8

amphibians, frogs, lizards etc

= cold blooded, gain heat from their surroundings

Question 9

endotherms

Answer 9

humans, mammals etc

• warm blooded
• gain heat metabolically

Question 10

Steps in which the body controls its temperature

Answer 10

1- receptors in skin detect external temperature
2- information sent to hypothalamus
3- instructions sent to brain
4- effectors in skin increase or decrease vasodilation
5- blood flow to the skin’s surfaces increases or decreases
6- the temperature of body returns to the correct level

Question 11

keeping warm (4)

Answer 11

• body temp drops, impulses sent from thermoregulatory system to body to prevent cooling down, reducing energy transferred to surroundings
  capillaries in skin = become narrower = restricts blood flow (vasoconstriction)
  sweat glands = stop working =reduces evaporation = less energy to environment
  skeletal muscles contract and relax rapidly = shivering= raises body temp

hair pulled erect to rap insulating layer of air

Question 12

cooling down (3)

Answer 12

• body temp rises, impulses sent from thermoregulatory system to body so more energy is transferred to surroundings

vasodilation (capillaries wider, increase blood flow/skin flushes) = cools you down/warms surroundings

sweat from sweat glands in skin = evaporation of water from skin cools you down = so in humid conditions harder to cool down as less evaporation

hair lies flat so insulating layer of air is not trapped

Question 13

heat exhaustion vs heat stroke

Answer 13

exhaustion - dehydration, sweating, headache, nausea, fatigue, muscle cramp
stroke - stop sweating, body reaches 40 c, enzymes denature, organ failure, death

Question 14

why do reflex reactions happen

Answer 14

as a result of electrical impulses following a specific path (reflex arc)
= keep us away from danger, unconscious decision

Question 15

Reflex Arc

Answer 15

1) a stimulus detected by receptors
2) electrical impulses from receptor passes along a sensory neuron to central nervous system (the co-ordinator e.g spinal cord )
3) when impulse from sensory neurone arrives at a synapse with a relay neurone, a chemical is released diffusing across the synapse
4) this sets off an electrical impulse travelling across the relay neurone
5) impulse reaches synapse between relay and motor neurone and another chemical is released and diffuses to the motor neurone, starting a new electrical impulse travelling down motor neurone to effector
5) stimulates response of effector eg a muscle - responds by contracting, gland - responds by releasing chemical substances

Question 16

order of reflex arc( not detailed)

Answer 16

stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response

Question 17

Growth hormone (produced in, functions, effects of deficiency or over production of hormone)

Answer 17

produced in hypothalamus
functions; gigantisism = massive growth
effects: too much causes people to grow taller than normal

Question 18

Phototropism

Answer 18

A plants response to light.
- If the part of the plant grows towards the light it means it is positively phototrophic
= This happens at the shoot tip (meristem)
- Negative phototropism is when the plant bends away from the light
= This happens at the root

Question 19

Tropism

Answer 19

How a plant responds to its environment

Question 20

Geotropism

Answer 20

The plant responds to gravity
- If the plant is positive geotropism that means it grows towards the way of gravity
=This happens at the roots
-If the plant is a negative geotropism that means it grows the opposite way of gravity
= This happens at the root tips.

Question 21

Auxin (plants)

Answer 21

A hormone which controls the moisture, gravity and light the plant responds to
= The response happens as the hormone is distributed unevenly, leading to the shoots bending towards the sun.

Question 22

What happens on the dark/light sides of plants?

Answer 22

dark - cells absorb more water so are more elongated(auxin produced on shady side which makes it absorb more water as it increases moisture!)
light - normal size cells

Question 23

How does auxin control geotropism?

Answer 23

1) Auxin slows growth in the root , so they grow down
2) Auxin stimulates growth in meristem , so stem grows upwards
= uneven distribution

Question 24

The three plant hormones

Answer 24

1) Auxin - controls the moisture, light and gravity the plant responds to (uneven distribution, more auxin means more growth)
2) Gibberellins (GAs) - regulates growth and influence various developmental processes including; stem elongation, germination (ending seed dormancy) and flowering
3) Ethene - involved in fruit ripening (like in bananas, green to yellow)

Question 25

Germination?

Answer 25

Germination is the process by which an organism grows from a seed or spore

Question 26

RP 8 -> plant responses

Investigate the effect of light intensity on the height of seedlings

Answer 26

IV-> light intensity CV-> volume of water/type of seeds/number of seeds
DV-> height of seedlings

1) place cotton wool in the three Petri dishes and wet them in equal volumes of water using a pipette cv
2) then place 10 seedlings in each dish, type of seed is cv
3) next, leave dishes in a warm place to allow them to germinate. Water them every day, with the same volume of water
4) after seeds germinate, make sure each dish has the same number of seedlings -> cv
5) use a ruler to measure the height of each seedlings (hold stems to make sure they are straight, be careful!)
6) place the three dishes in three different conditions; full sunlight (windowsill), partial light (back of lab), darkness (cupboard)
7) measure height of seedlings every day for at least five consecutive days and record in table, calculate mean seedling height, draw diagrams to show different light intensity effects

Question 27

RP 8 RESULTS (SEEDLINGS LIGHT)

Answer 27

Full sunlight and partial sunlight experience phototropism as chlorophyll is very efficient at absorbing light energy so plant does not need full sunlight to grow.
= auxin concentrates on the side of seedling furthest from light so causes elongation

Darkness seedling germinates underground and grows rapidly to reach light.
Small and yellow leaves as once energy stores used up it cannot photosynthesize.

Question 28

RP 8 -> plant responses

investigate the effect of gravity on seedlings

Answer 28

• dish of seedlings placed on its side in darkness
• shoots grow upwards against direction of gravity, roots grow downwards towards direction of gravity
• auxin inhibits the cell growth in roots. Gravity causes auxin to buildup on lower side of route. So grows slower than upside, makes roots grow in direction of gravity