B3-Organism-level systems Flashcards
Tropism
Plant growth in response to stimulus
Positive Phototropism
Growth towards light
Positive gravitropism
Growth towards gravity
Negative tropism
Opposite of positive tropism
Fruit ripening hormone
Ethene
Hormone triggering growth after dormancy (plant)
Gibberellins
Homeostasis
State of steady internal, physical and chemical conditions
Thermoregulatory response to high temperatures
-hairs lower to stop heating being trapped -sweat produced -capillaries vasodilate (to increase heat loss by radiation)
Thermoregulatory response to cold temperatures
-hairs rise to creat heat trapping air layer -rapid muscle contraction and relaxation (shivering) for heat from respiration -Capillaries vasoconstrict to reduce heat loss by radiation
Blood sugar levels
-rise after meals -insulin lowers level by converting glucose-> glycogen in liver
Response to low blood sugar levels
-glucagon converts glycogen into glucose
Response to high sugar levels
-insulin lowers level by converting glucose to glycogen in the liver
How are blood water levels controlled
-urine produced in nephrons in kidneys to maintain water balance -controlled by hormone ADH -If water potential too low: Higher ADH = Higher water reabsorption in nephron = less urine production
Higher auxin levels
-elongate cells in tropism -root grows on side with less auxin shoot grows with more auxin
Nervous system response
-quicker response -more targeted -short acting
Endocrine system response
-slower response -acts over wide area -longer lasting -endocrine glands secrete hormones into the blood -triggers response in specific cells in target organs
Adrenaline
Hormone produced in the adrenal gland prepares body for intense action (fight or flight)
Hormones
Chemical messengers
Thyroxine
-Hormone produced in thyroid gland -regulates metabolic rate -levels controlled by negative feedback
Nervous response to stimulus (including CNS)
Receptors->sensory neurones->spinal cord->brain->spinal cord->motor neurones->effectors
Effectors
Muscles or glands that cause response
Central nervous system
Decides appropriate response (relay neurons) Made up of the brain and spinal cord