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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
what are neurosecretory cells
nerve cells that produce secretions from the ends of their axons which either stimulate or inhibit release of hormones
26
what is the role of neurosecretory cells 1
produce substances that stimulate or inhibit the release of hormones from the anterior pituitary
27
what is the name of the substances produced from neurosecretory cells 1
releasing factors or release-inhibiting factors
28
what is the role of neurosecretory cells 2
produce secretions that are stored in the posterior pituitary and are released later as hormones
29
what cells is the hypothalamus made up of
neurosecretory cells 1/2
30
what hormones are released from the anterior pituitary
- thyroid-stimulating hormone - growth hormone (GH) - adrenocorticotrophic hormone (ACTH) - follicle stimulating hormone (FSH) - luteinising hormone (LH - prolatin
31
what hormones are released by the posterior pituitary
- oxytocin - antidiuretic hormone (ADH)
32
what is the role of thyroid-stimulating hormone
controls the secretion of thyroxin and triiodothyronine from the thyroid gland
33
what is the role of growth hormone (GH)
stimulates the growth of body cells and increases the build up of proteins
34
what is the role of adrenocorticotrophic hormone (ACTH)
controls secretion of some of the hormones of the adrenal cortex of the adrenal glands
35
what is the role of follicle stimulating hormone (FSH)
in females - stimulates ovaries to produce oestrogen and development of ova in the menstrual cycle in males - stimulates the testes to produce sperm
36
what is the role of luteinising hormone (LH)
in females - stimulates ovulation and formation of corpus luteum and prepares uterus for implanting in males - stimulates the testes to produce testosterone
37
what is the role of prolactin
stimulates and maintains production of milk by the mammary glands
38
what is the role of antidiuretic hormone (ADH)
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
what is the role of oxytocin
stimulates the muscles of the uterus to contract during labour and the contraction of cells in the mammary tissue
40
how do hormones work when they are not lipid soluble
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
what is cyclic AMP (cAMP)
formed from ATP triggers increased cellular respiration, increased contraction of muscle, relaxation of smooth muscle in blood vessels
42
how does adrenaline work
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
how do lipid soluble hormones work
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
what hormones are commonly lipid soluble
oestrogen and testosterone
45
why do plants need hormones
the rely on them to communicate between different parts of the plant and respond to factors such as light and gravity
46
what different factors of light affect plants
direction of light intensity of light length of exposure to light
47
what factors effect the growth of plants
gravity water temperature light
48
what is a tropism
plant growth responses to environmental cues
49
what are auxins
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
how do auxins move down the plant from the shoots to the roots
active transport and calcium ions
51
what is apical dominance
suppression of growth in lateral shoots so that one main stem grows fastest
52
what does the response of a plant to auxin depend upon
concentration of hormone and the region of the plant
53
explain the elongation of plant cells using hormones
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
why do plant cells become more rigid over time
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
how do plants grow towards light
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
what do gibberellins do
affect internodes of stems stimulate elongation of growing cells promote growth of fruit
57
how are gibberellins involved in seed germination
the are involved in breaking dormancy of seeds and stimulating formation of enzymes in seeds
58
what do cytokinins do
promote cell division in apical meristem and cambium
59
what is abscission
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
what name is given to hormones which work together, completing each other and giving a greater response
synergy
61
what name is given to hormones that have opposite effects and the balance between them determines the outcome
antagonism
62
what hormones work antagonistically together to maintain apical dominance
auxins and cytokinins
63
what 2 plant hormones have a synergy
auxins and gibberellins
64
how do auxins and cytokinins work antagonistically in the growth of plants
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
what would happen to a plant that wasn't given any light
the metabolism of a plant is severely disrupted and no chlorophyll is formed and no photosynthesis takes place and eventually the plant dies
66
what is photomorphogenesis
the process by which the form and development of a plant is controlled by the levels and type of light
67
what is the wavelength of light
580-660nm
68
what is the wavelength of far red light
700-730nm
69
what do plants use to detect red light and far red light
phytochromes
70
what are phytochromes
plant pigment that reacts with different types of light and affects the response of the plant
71
does red light stimulate or inhibit germination
red light stimulates germination
72
does far red light stimulate or inhibit germination
far red light inhibits germination
73
what phytochrome absorbs red light
Pr
74
what phytochrome absorbs far red light
Pfr
75
what occurs to Pr when is it exposed to red light
it is converted to Pfr
76
what occurs when Pfr when it is exposed to far red light
it is converted to Pr
77
what occurs to phytochromes as a seed germinates
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
what occurs to the formation of Pr and Pfr in the dark
Pfr is converted to Pr
79
is Pr or Pfr more biologically active
Pfr
80
is Pr or Pfr more stable
Pr
81
what is the photoperiod
amount of light an organism is exposed to in the 24hour period
82
what are short-day plants
plants flowering when days are short and nights are long
83
what are long-day plants
plants flowering when days are long and nights are short
84
what are day-neutral plants
plants where flowering is not affected by the length of time they are exposed to light or dark
85
how does red light affect flowering of plants
inhibits flowering of short-day plants stimulates flowering of long-day plants
86
what are etiolated plants
plants that grow in the dark with long internodes, thin stems, small or unformed leaves and white or pale yellow in colour
87
what are the typical characteristics of a germinating plant
- rapid stem lengthening but little thickening - relatively little root growth - no leaf growth - no chlorophyll

Biology (33 decks)

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