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Biology > 9.1 > Flashcards

9.1 Flashcards

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1
Q

How do the nervous and chemical control systems interact to maintain homeostasis

A

changes in the body are detected by sensers/receptors which then sends a message to effectors, these then work to either reverse the change or increase it

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2
Q

why does water potential need to be maintained

A

to avoid osmotic effects that could damage or destroy cells

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3
Q

why does temperature need to be maintained

A

maintains optimum activity of enzymes
maintains integrity of membranes
controls movement of substances into and out of the cells

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4
Q

why does the pH need to be maintained

A

for structures of protein molecules to remain stable
allows enzymes to function at their optimum
structure of cell membrane is maintained

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5
Q

what are the mechanisms controlled in homeostasis

A

pH
temperature
water potential

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6
Q

define homeostasis

A

the maintenance of a state of dynamic equilibrium in the body, despite changes in external or internal conditions

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7
Q

what are sensors/receptors

A

specialised cells that are sensitive to specific changes in the environment

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8
Q

what are effectors

A

systems (usually muscles or glands) that work to either reverse, increase or decrease changes in a biological system

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9
Q

define negative feedback system

A

a way of maintaining a condition by recognising an increase by receptors and as a result effectors are stimulated to decrease it to maintain dynamic equilibrium

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10
Q

what are the effectors for hormonal communication

A

target organs

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11
Q

what are the effectors for nervous system communication

A

muscles and glands

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12
Q

define positive feedback system

A

effectors work to increase an effect that has triggered a response

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13
Q

explain the positive feedback system of contractions of the uterus during labour

A

brain stimulates pituitary to release oxytocin
oxytocin makes uterus contract harder pushing baby against cervix
baby pushes against cervix - cervix stretches
stretch receptors in cervix send impulses to brain

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14
Q

why are chemical messengers used in homeostasis control

A

effect lasts over a long period of time
reach the entire body

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15
Q

where are hormones released from

A

endocrine glands

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16
Q

outline what hormones do

A

organic chemicals produced in endocrine glands and released into the blood carried through the transport system to parts of the body that they bring about changes which may be widespread or specifically targeted

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17
Q

what are endocrine glands

A

produce hormones
do not have ducts
release hormones directly into the blood stream

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18
Q

what are exocrine glands

A

produce chemicals (e.g.enzymes) and release them along small tubes or ducts

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19
Q

what are the common forms of hormones

A

proteins, peptides, steroids

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20
Q

how are glands well adapted

A

always have a rich blood supply of capillaries to release their hormones and chemicals into

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21
Q

how is hormone release controlled by the nervous system

A

the endocrine gland is directly stimulated by a nerve resulting in the release of the hormone and doesn’t release the hormone when not stimulated

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22
Q

how is hormone release controlled by response to chemical stimulus in a negative feedback loop

A

increase in stimulating chemical -> increase in hormone release -> decrease in stimulating chemical -> hormone release decreased -> increase in stimulating chemical

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23
Q

what is the pituitary gland

A

a small gland in the brain that has an anterior lobe and a posterior lobe and produces and releases secretions that affect the activity of most endocrine glands

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24
Q

what is the hypothalamus

A

small area in the brain directly above the pituitary gland that controls the activities of the pituitary gland and coordinates the autonomic nervous system

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25
Q

what are neurosecretory cells

A

nerve cells that produce secretions from the ends of their axons which either stimulate or inhibit release of hormones

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26
Q

what is the role of neurosecretory cells 1

A

produce substances that stimulate or inhibit the release of hormones from the anterior pituitary

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27
Q

what is the name of the substances produced from neurosecretory cells 1

A

releasing factors or release-inhibiting factors

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28
Q

what is the role of neurosecretory cells 2

A

produce secretions that are stored in the posterior pituitary and are released later as hormones

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29
Q

what cells is the hypothalamus made up of

A

neurosecretory cells 1/2

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30
Q

what hormones are released from the anterior pituitary

A
  • thyroid-stimulating hormone
  • growth hormone (GH)
  • adrenocorticotrophic hormone (ACTH)
  • follicle stimulating hormone (FSH)
  • luteinising hormone (LH
  • prolatin
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31
Q

what hormones are released by the posterior pituitary

A
  • oxytocin
  • antidiuretic hormone (ADH)
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32
Q

what is the role of thyroid-stimulating hormone

A

controls the secretion of thyroxin and triiodothyronine from the thyroid gland

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33
Q

what is the role of growth hormone (GH)

A

stimulates the growth of body cells and increases the build up of proteins

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34
Q

what is the role of adrenocorticotrophic hormone (ACTH)

A

controls secretion of some of the hormones of the adrenal cortex of the adrenal glands

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35
Q

what is the role of follicle stimulating hormone (FSH)

A

in females - stimulates ovaries to produce oestrogen and development of ova in the menstrual cycle
in males - stimulates the testes to produce sperm

36
Q

what is the role of luteinising hormone (LH)

A

in females - stimulates ovulation and formation of corpus luteum and prepares uterus for implanting
in males - stimulates the testes to produce testosterone

37
Q

what is the role of prolactin

A

stimulates and maintains production of milk by the mammary glands

38
Q

what is the role of antidiuretic hormone (ADH)

A

decreases the urine volume by affecting the tubules of the kidney, can cause arteries to constrict after hemorrhage to prevent excess blood loss and raising blood pressure

39
Q

what is the role of oxytocin

A

stimulates the muscles of the uterus to contract during labour and the contraction of cells in the mammary tissue

40
Q

how do hormones work when they are not lipid soluble

A

if hormones are not lipid soluble they cannot cross the cell membrane so it binds to a receptor on the cell membrane which triggers a series of membrane-bound reactions that result in formation of a second chemical messenger inside the cell that then activates enzymes within the cell

41
Q

what is cyclic AMP (cAMP)

A

formed from ATP
triggers increased cellular respiration, increased contraction of muscle, relaxation of smooth muscle in blood vessels

42
Q

how does adrenaline work

A

it is not lipid soluble therefor it binds to receptor on the cell surface membrane
this activates membrane-bound proteins which activates adenylate cyclase for the formation of cAMP

43
Q

how do lipid soluble hormones work

A

the hormone passes through the membrane and inside the cell where it binds to a receptor and forms a hormone-receptor complex which can then pass through pores in the nuclear membrane so that it then acts as a transcription factor

44
Q

what hormones are commonly lipid soluble

A

oestrogen and testosterone

45
Q

why do plants need hormones

A

the rely on them to communicate between different parts of the plant and respond to factors such as light and gravity

46
Q

what different factors of light affect plants

A

direction of light
intensity of light
length of exposure to light

47
Q

what factors effect the growth of plants

A

gravity
water
temperature
light

48
Q

what is a tropism

A

plant growth responses to environmental cues

49
Q

what are auxins

A

plant hormones that act as powerful growth stimulants and are involved in apical dominance, stem and root growth, and tropic responses to unilateral light

50
Q

how do auxins move down the plant from the shoots to the roots

A

active transport and calcium ions

51
Q

what is apical dominance

A

suppression of growth in lateral shoots so that one main stem grows fastest

52
Q

what does the response of a plant to auxin depend upon

A

concentration of hormone and the region of the plant

53
Q

explain the elongation of plant cells using hormones

A

the molecule IAA binds to specific receptors on the cell surface membrane
activates pumping of H+ ions into the cell wall spaces to increase pH to 5
this provides the optimum pH for the enzyme that breaks bonds between cellulose microfibrils
the microfibrils slide past each other easily making the cell wall flexible
the cell then absorbs water by osmosis and due to turgor pressure the flexible cell wall elongates and expands

54
Q

why do plant cells become more rigid over time

A

as the cell matures the IAA is destroyed and the pH rises, the enzyme is inhibited, bonds form between cellulose microfibrils and becomes rigid

55
Q

how do plants grow towards light

A

light on one side of the plant is stronger than the other
light causes auxin to move laterally across the shoot away from the light
producing a greater concentration on the unilluminated side
the shoot tip acts as a photoreceptor
cell growth and elongation occurs on the dark side
resulting in shoot bending towards the light
until it grows directly towards the light and auxin concentration becomes even so it grows straight towards the light

56
Q

what do gibberellins do

A

affect internodes of stems
stimulate elongation of growing cells
promote growth of fruit

57
Q

how are gibberellins involved in seed germination

A

the are involved in breaking dormancy of seeds and stimulating formation of enzymes in seeds

58
Q

what do cytokinins do

A

promote cell division in apical meristem and cambium

59
Q

what is abscission

A

the shedding of leaves, flower parts or fruits from a plant after the formation of an abscission zone across the stem attaching the organ to the plant

60
Q

what name is given to hormones which work together, completing each other and giving a greater response

A

synergy

61
Q

what name is given to hormones that have opposite effects and the balance between them determines the outcome

A

antagonism

62
Q

what hormones work antagonistically together to maintain apical dominance

A

auxins and cytokinins

63
Q

what 2 plant hormones have a synergy

A

auxins and gibberellins

64
Q

how do auxins and cytokinins work antagonistically in the growth of plants

A

initially high concentrations of auxin to promote growth of lead shoot and as this increases cytokinins are inhibited until auxin concentration decreases then cytokinins become dominant and lateral buds are activated and grow

65
Q

what would happen to a plant that wasn’t given any light

A

the metabolism of a plant is severely disrupted and no chlorophyll is formed and no photosynthesis takes place and eventually the plant dies

66
Q

what is photomorphogenesis

A

the process by which the form and development of a plant is controlled by the levels and type of light

67
Q

what is the wavelength of light

A

580-660nm

68
Q

what is the wavelength of far red light

A

700-730nm

69
Q

what do plants use to detect red light and far red light

A

phytochromes

70
Q

what are phytochromes

A

plant pigment that reacts with different types of light and affects the response of the plant

71
Q

does red light stimulate or inhibit germination

A

red light stimulates germination

72
Q

does far red light stimulate or inhibit germination

A

far red light inhibits germination

73
Q

what phytochrome absorbs red light

A

Pr

74
Q

what phytochrome absorbs far red light

A

Pfr

75
Q

what occurs to Pr when is it exposed to red light

A

it is converted to Pfr

76
Q

what occurs when Pfr when it is exposed to far red light

A

it is converted to Pr

77
Q

what occurs to phytochromes as a seed germinates

A

as a seedling is germinating is it only exposed to far red light so it has Pr then as soon as it breaks through the surface of the soil it is exposed to red light and Pr is converted to Pfr

78
Q

what occurs to the formation of Pr and Pfr in the dark

A

Pfr is converted to Pr

79
Q

is Pr or Pfr more biologically active

A

Pfr

80
Q

is Pr or Pfr more stable

A

Pr

81
Q

what is the photoperiod

A

amount of light an organism is exposed to in the 24hour period

82
Q

what are short-day plants

A

plants flowering when days are short and nights are long

83
Q

what are long-day plants

A

plants flowering when days are long and nights are short

84
Q

what are day-neutral plants

A

plants where flowering is not affected by the length of time they are exposed to light or dark

85
Q

how does red light affect flowering of plants

A

inhibits flowering of short-day plants
stimulates flowering of long-day plants

86
Q

what are etiolated plants

A

plants that grow in the dark with long internodes, thin stems, small or unformed leaves and white or pale yellow in colour

87
Q

what are the typical characteristics of a germinating plant

A
  • rapid stem lengthening but little thickening
  • relatively little root growth
  • no leaf growth
  • no chlorophyll

Biology (33 decks)

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