Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

IB biology > topic 11 > Flashcards

topic 11 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

every organism has —– ——– on the surface of their cells

A

unique molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

antigens on the surface of red blood cells

A

stimulate antibody production in a person with a different blood group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

describe the presence and absence of antigens on the surface of blood cells from different blood groups

A
  • all three alleles involve a basic antigen sequence called antigen H
    A: this is modified by the addition of molecule N-acetylgalactosamine
    B: additional molecule is galactose
    AB: both types of antigen
    O: neither surface glycoprotein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what happens if a recipient is given a transfusion involving the wrong type of blood?

A

an immune response occurs. antibodies are produced, agglutination (clumping) occurs, followed by hemolysis where red blood cells are destroyed and blood may coagulate in vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe an immune response

A
  1. macrophage ingests pathogen and displays antigens on it
  2. helper T cell specific to the antigen is activated by the macrophage
  3. B cell specific to the antigen is activated by proteins from the helper T cell
  4. B cell divides repeatedly to produce antibody-secreting plasma cells
  5. B cell also divides to produce memory cells
  6. antibodies produced by the clone of plasma cells are specific to antigens on the pathogen and help destroy it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how does activation of helper T cells work?

A

they have an antibody-like receptor protein in their plasma membranes, which can bind to antigens displayed by macrophages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how does the structure of plasma cells relate to their function?

A
  • the cytoplasm contains an extensive network of rough endoplasmic reticulum (rER), which manufactures, modifies, and transports proteins (antibodies).
  • The range of genes expressed is lower than a typical cell as the cell produces a lot of the same protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

define clonal selection

A

the generation of large numbers of plasma cells that produce one specific antibody type

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

give and explain 4 ways in which antibodies aid the destruction of pathogens

A
  1. opsonisation- make the pathogen more recognisable to phagocytes so they are more readily engulfed. also, once bound, they can link the pathogen to phagocytes
  2. neutralisation of viruses and bacteria: antibodies prevent viruses from docking to / entering host cells
  3. neutralisation of toxins- bind to the toxins produced by pathogens, preventing them from affecting susceptible cells
  4. activation of complement- antibodies activate a complement cascade which leads to the formation of a membrane attack complex that forms a pore in the membrane of the pathogen allowing water and ions to enter the cell and causing lysis
  5. agglutination of pathogens, preventing cell entry and aiding ingestion by pathogens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the complement system?

A

a collection of proteins which ultimately lead to the perforation of the membranes of pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what does immunity depend upon?

A

the persistence of memory cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe how vaccines lead to immunity

A

they contain antigens that trigger immunity by causing a primary immune response but do not cause the disease

if the actual pathogen enters the body, it will be destroyed by the antibodies in a secondary immune response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what was the first infectious disease of humans to have been eradicated by vaccination?

A

smallpox

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

give 3 reasons why the smallpox eradication campaign was successful

A
  • only humans can catch and transmit smallpox. there is no reservoir where the disease could be maintained and re-emerged
  • symptoms of infection emerge quickly and are readily visible allowing teams to ‘ring vaccinate’ all of the people who might have come into contact with the afflicted person
  • immunity is long-lasting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

pathogens can either be

A

species-specific or able to cross species barriers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define a zoonosis

A

a pathogen which can cross a species barrier
these are a growing health concern

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

when and how are histamines released?

A
  • by mast cells (immune cells found in connective tissue) secrete histamine in response to infection
  • by basophils which circulate in the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

state the effect of histamine on blood vessels

A

causes the dilation of the small blood vessels in the infected area causing the vessels to become leaky. This increases the flow of fluid containing immune components to the infected area and allows for some of the immune components to leave the blood vessel resulting in both specific and non-specific responses.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Sensitization: Initial exposure to allergen and

Allergic Reaction: Secondary exposure to same allergen

A
  1. when a specific B cell first encounters the allergen, it differentiates into plasma cells and makes large quantities of antibody (IgE)
  2. the IgE antibodies attach to mast cells, effectively ‘priming’ them towards the allergen
  3. upon re-exposure to the allergen, the IgE-primed mast cells release large amounts of histamine which causes inflammation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

symptoms of an allergic reaction

A

nose: itching, fluid build-up, sneezing, mucus secretion and inflammation
allergic rashes and dangerous swelling (anaphylaxis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

define monoclonal antibodies

A

highly specific, purified antibodies that are produced by a clone of cells derived from a single cell. they recognise only one antigen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the use of monoclonal antibodies?

A

the treatment and diagnosis of diseases; eg the test for malaria or the creation of antibodies for injection into rabies victims

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

define a hybridoma cell

A

the cells formed by fusion of antibody-producing plasma B cells and myeloma (tumour) cells, which produce monoclonal antibodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

describe how hybridoma cells are created

A
  1. antigen recognised by the antibody is injected into a mouse or other mammal
  2. the mouse’s immune system makes plasma B cells that are capable of producing the desired antibody
  3. plasma cells are removed from the spleen of the mouse and fused with cancer cells called myeloma cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

describe how pregnancy tests work with a diagram

A

kits use monoclonal antibodies to detect hCG, which is produced during pregnancy by the developing embryo and the placenta. the urine of pregnant women contains detectable levels of hCG

  1. free monoclonal antibodies specific to hCG are conjugated to an enzyme that changes the colour of a dye
  2. a second set of monoclonal antibodies specific to hCG are immobilised to the dye substrate
  3. if hCG is present in urine, it will interact with both sets of monoclonal antibody (forming an antibody ‘sandwich’)
  4. when both sets of antibody are bound to hCG, the enzyme is brought into physical proximity with the dye, changing its colour
  5. a third set of monoclonal antibodies will bind any unattached enzyme-linked antibodies, functioning as a control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

function of bones and exoskeletons

A

provide anchorage for muscles and act as levers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

define exoskeletons

A

external skeletons that surround and protect most of the body surface of animals such as crustaceans and insects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

describe a first class lever and give an example

A

E (down), F, R (up)

Example - when a person nods their head backwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

describe a second class lever and give an example

A

F, R, E (down)

Example - someone walking, the moment where they stand on their tiptoes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

describe a third class lever and give an example

A

F, E (up), R (down)

Example - flexing forearm down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

skeletal muscles are

A

antagonistic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

define antagonistic muscles

A

when one muscle contracts, the other relaxes - they thus produce opposite movements at a joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

give a example of an antagonistic muscle pair

A

in the elbow, the triceps extends the forearm while the biceps flex the forearm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

give an example of antagonistic pairs of muscles in an insect

A

in the leg of a grasshopper, which is specialised for jumping.

  1. when the grasshopper prepares to jump, the flexor muscles will contract
  2. this will bring the tibia and tarsus into a position where they resemble the letter Z and the femur and tibia are brought closer together (flexing). extensor muscles relax during this phase
  3. extensor muscles contract extending the tibia and producing a powerful propelling force.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

draw a diagram of insect legs and their antagonistic muscle pairs

A

478

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

draw a diagram of a human flow as an example of a synovial joint

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

define a synovial joint

A

a freely moveable joint that allows a wide range of movement (articulation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

cartilage

A
  • tough, smooth tissue that covers the regions of bone in the joint
  • prevents contact between regions of bone that might otherwise rub together, helping prevent friction
  • absorbs shocks that might cause bones to fracture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

synovial fluid

A
  • fills a cavity in the joint between the cartilages on the ends of the bones
  • lubricates the joint so helps to prevent the friction that would occur if the cartilages were dry and touching
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

joint capsule

A
  • tough ligamentous covering to the joint
  • seals the joint and holds in the synovial fluid
  • helps prevent dislocation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

radius bone

A

to which the biceps is attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

biceps

A

flexes the joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

humerus bone

A

to which the biceps and triceps are attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

triceps

A

extends the joint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

ulna bone

A

to which the triceps is attached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

synovial joints allow

A

certain movements but not others

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what determines the movements that are possible in a body part?

A

the structure of a joint, including the joint capsule and the ligaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

the knee joint can act as

A

a hinge joint, which allows only flexion (bending) and extension (straightening). It can also act as a pivot joint when flexed, which is when it has a greater range of movement

52
Q

the hip joint can act as

A

a ball and socket joint that can flex and extend, rotate, and move sideways (abduction) and back (adduction).

53
Q

state the three types of muscle

A
  • striated (skeletal muscle)
  • smooth muscle
  • cardiac muscle
54
Q

function of striated/skeletal muscle

A

muscles attached to bones that are used to move the body

55
Q

what is striated muscle composed of?

A

bundles of muscle cells known as muscle fibres

56
Q

state the main features of muscle fibres

A
  • sarcolemma
  • many nuclei
  • sarcoplasmic reticulum
  • mitochondria
  • myofibrils
57
Q

sarcolemma

A

single plasma membrane that surrounds each muscle fibre

58
Q

why are muscle fibres much longer than typical cells and contain many nuclei?

A

embryonic muscle cells fuse together to form muscle fibres

59
Q

what is the sarcoplasmic reticulum and what does it do?

A

it is a modified version of the endoplasmic reticulum and wraps around every myofibril, conveying the signal to contract to all parts of the muscle fibre at once. It also stores calcium.

60
Q

where are mitochondria stored?

A

between the myofibrils

61
Q

muscle fibres contain many…

A

myofibrils

62
Q

describe a myofibril

A
  • alternating light and dark bands, which give striated muscle its stripes
  • in the centre of each light band is a disc-shaped structure (Z-line)
63
Q

each myofibril is made up of…

A

contractile sarcomeres.

64
Q

define a sarcomere

A

the functional unit of a myofibril, located between one Z-line and the next.

65
Q

what is the pattern of light and dark bands in sarcomeres due to?

A

a precise and regular arrangement of two types of protein filament - thin actin filaments and thick myosin filaments

66
Q

location of actin filaments

A

attached to a Z line at one end

67
Q

location of myosin filaments

A

interdigitated with actin filaments at both ends and occupy the centre of the sarcomere

68
Q

describe the ratio of actin to myosin filaments and their function

A

each myosin filament is surrounded by six actin filaments and forms cross-bridges with them during muscle contraction.

69
Q

draw a labelled diagram of the structure of a sarcomere

A

p481

70
Q

how is the contraction the skeletal muscle achieved?

A

by the sliding of actin and myosin filaments; the myosin filaments pull the actin filaments inwards during the centre of the sarcomere. this shortens each sarcomere and therefore the overall length of the muscle fibre

71
Q

what causes the sliding motion of actin and myosin filaments?

A

myosin filaments: they have heads that can bind to special sites on actin filaments, creating cross-bridges, through which they can exert a force, using energy from ATP

72
Q

how is it that many cross-bridges can form at once?

A

the myosin heads are regularly spaced along the actin filaments

73
Q

what is the M-line?

A

another line in the centre of the sarcomere

74
Q

what is the visible difference between a relaxed and a contracted sarcomere?

A

in a relaxed sarcomere, there is a more visible light band on either side of the M-line

75
Q

what controls muscle contractions?

A

calcium ions and the proteins tropomyosin and troponin

76
Q

describe how calcium ions, tropomyosin and troponin work to control muscle contractions

A
  • in a relaxed muscle, tropomyosin (a regulatory protein) blocks the binding sites on actin
  • when a motor neuron sends a signal to a muscle fibre to make it contract, the sarcoplasmic reticulum releases calcium ions
  • Ca ions bind to troponin which causes tropomyosin to move, exposing actin’s binding sites.
77
Q

describe the process of muscle contraction

A
  1. myosin filaments have heads which form cross-bridges when they are attached to binding sites on actin filaments
  2. ATP binds to the myosin heads and causes them to break the cross-bridges by detaching from the binding sites
  3. ATP is hydrolysed to ADP and phosphate, causing the myosin heads to change their angle. The heads are said to be cocked in their new position as they are storing potential energy from ATP
  4. the heads attach to binding sites on actin that are further from the centre of the sarcomere than the previous sites
  5. the ADP and phosphate are released and the heads push the actin filament inwards towards the centre of the sarcomere (called the power stroke)
78
Q
A
79
Q

what to spermatogenesis and oogenesis both involve?

A

mitosis, cell growth, two divisions of meiosis and differentiation

80
Q

define oogenesis

A

the production of egg cells in the ovaries

81
Q

describe the pre-puberty stage of oogenesis

A
  1. starts in the ovaries of a female fetus
  2. germ cells in the fetal ovary divide by mitosis and the cells formed move to distribute themselves through the cortex of the ovary
  3. when the foetus is four or five months old, these cells grow and start to divide by meiosis
  4. by the seventh month, they are still in the first division of meiosis and a single layer of cells (follicle cells) has formed around them.

no further development takes place until after puberty

82
Q

define a primary follicle

A

the cell that has started to divide by meiosis, together with the surrounding follicle cells

83
Q

describe the post-puberty stage of oogenesis

A

no more primary follicles are produced, but at the start of each menstrual cycle a small batch are stimulated to develop by FSH. Usually only one goes on to become a mature follicle, containing a secondary oocyte.

84
Q

difference between a mature ovarian follicle and a primary follicle

A

a mature ovarian follicle has many more follicle cells, outer and inner follicle cells and cavities, and the oocyte is more fully developed

85
Q

define spermatogenesis

A

the production of sperm in the testes

86
Q

describe the testes

A

composed of a mass of narrow tubes, called seminiferous tubules

87
Q

describe the germinal epithelium

A
  • outer layer of cells of seminiferous tubules.
  • where process of sperm production begins
  • contains cells in various stages of sperm production, with the most mature stages closest to the fluid-filled centre of the ST
88
Q

Sertoli cells

A

large nurse cells in the wall of the tubule

89
Q

spermatozoa

A

cells that have developed tails

90
Q

draw a diagram and describe the stages of spermatogenesis

A
  1. an outer layer called germinal epithelium cells (2n) divide endlessly by mitosis to produce more diploid cells
  2. diploid cells grow larger and are then called primary spermatocytes (2n)
  3. each primary spermatocyte carries out the first division of meiosis to produce two secondary spermatocytes (n)
  4. each secondary spermatocyte carries out the second division of meiosis to produce two spermatids (n)
  5. spermatids become associated with nurse cells (Sertoli cells) which help the spermatids to develop into spermatozoa (cell differentiation)
  6. sperm detach from Sertoli cells and are eventually carried out of the testis by the fluid in the centre of the seminiferous tubule
91
Q

draw a diagram and describe the stages of oogenesis

A
  1. The process begins during foetal development, when a large number of cells (oogonia) are formed by mitosis before undergoing a period of growth
  2. These cells begin meiosis but are arrested in prophase I until puberty
  3. At puberty, some follicles continue to develop each month is response to FSH secretion
  4. These follicles complete the first meiotic division to form two cells of unequal size
    The cell with less cytoplasm is a polar body (which degenerates), while the larger cell forms a secondary oocyte
  5. The secondary oocyte begins the second meiotic division but is arrested in prophase II (until fertilisation)
  6. It is released from the ovary (ruptured follicle develops into corpus luteum) and, if fertilisation occurs, will complete meiosis
  7. The second meiotic division will produce an ovum and a second polar body
92
Q

draw and annotate an egg

A
  • two centrioles
  • haploid nucleus
  • cytoplasm (or yolk) containing droplets of fat
  • cortical granules
  • layer of gel composed of glycoproteins (zona pellucida)
  • layer of follicle cells (corona radiata)
  • plasma membrane
  • first polar cell
93
Q

draw and annotate a sperm

A
  • acrosome
  • plasma membrane
  • haploid nucleus
  • centriole
  • helical mitochondria
  • mid-piece
  • tail
  • microtubules in a 9+2 arrangement
  • protein fibres to strengthen the tail
94
Q

differences between oogenesis and spermatogenesis:
Location
Number of gametes produced
Gametes per germ cell
Beginning of process
Timing of gamete formation
End of process
Timing of gamete release
Meiotic divisions
Germ line epithelium

A

Testis
Life long production (millions)
Four
Begins at puberty
Continuous (any time)
Fertility is life long but reduces
Any time
Uninterrupted
Involved in gamete production

Oogenesis
Ovary
Fixed amount (only - 400 mature)
One
Begins during fetal development
Once a month (menstrual cycle)
Fertility stops at menopause
Monthly cycle
Arrested
Not involved in gamete production

95
Q

define polyspermy

A

when multiple sperm enter the egg

96
Q

state the 3 mechanisms that occur after sex

A
  1. the acrosome reaction
  2. penetration of the egg membrane
  3. the cortical reaction
97
Q

the acrosome reaction

A

when the sperm binds to the zona pellucid and the contents of the acrosome are related, the enzymes from it digest the zona pellucida.

98
Q

describe the acrosome

A

a large membrane-bound sac of enzymes in the head of the sperm

99
Q

penetration of the egg membrane

A
  • acrosome reaction exposes an area of the membrane on the tip of the sperm that has proteins that can bind to the egg membrane.
  • the first sperm that gets through the zona pellucid therefore binds and the membranes of sperm and egg fuse together
  • the sperm nucleus enters the egg cell (fertilisation)
100
Q

cortical reaction

A
  • sperm causes activation of the egg
  • the cortical granules (vesicles located near the egg membrane) release their contents from the egg by exocytosis
  • cortical vesicle enzymes result in the digestion of binding proteins so that no further sperm can bind, as well as a general hardening of the zona pellucida
101
Q

fertilisation in animals can be

A

internal or external

102
Q

internal fertilisation

A
  • terrestrial animals
    + ensures gametes do not dry out and sperm and ova are placed in prolonged close proximity to each other,
    + developing embryo is protected inside female
103
Q

external fertilisation

A
  • aquatic animals
    + animals have behaviours that bring eggs into proximity with sperm
  • risks including predation and susceptibility to environmental variation such as temperature and pH fluctuations and pollution
104
Q

fertilisation -> implantation

A
  1. fertilised ovum divides by mitosis to become an embryo
  2. there is migration of cells, giving the embryo the shape of a hollow ball (blastocyst)
  3. at 7 days old, the blastocyst reaches the uterus, having been moved down the oxidant by the cilia of cells in the oviduct wall
  4. at this age the zona pellucida (surrounded + protected embryo) breaks down
  5. obtains needed supply of food by sinking into endometrium/uterus wall (implantation)
105
Q

implantation onwards

A
  1. outer layer of blastocyst develops finger-like projects allowing it to penetrate uterus lining and exchange materials with mother’s blood
  2. embryo grows and develops
  3. by 8 weeks, it has started to form bone tissue and is considered a foetus rather than embryo
106
Q

role of hCG in early pregnancy

A

early in pregnancy the embryo produces human chorionic gonadotropin, which stimulates the corpus lute in the ovary to continue to secrete progesterone and oestrogen, which stimulate the continued development of uterus wall, which supplies the embryo with everything that it needs

107
Q

two main roles of placenta

A
  • facilitate exchange of materials between mother and embryo
  • secrete estrogen and progesterone
108
Q

why is the placenta needed?

A

because the body surface area to volume ratio becomes smaller as the foetus grows larger

109
Q

describe the structure of the placenta

A
  • chorionic villi extend into the intervillous space (lacuna) and exchange materials between mother and fetus
  • villi are lined by microvilli to increase SA for material exchange
  • fetal capillaries within the villi lie close to the surface to minimise diffusion distance from blood in the lacunae
  • materials such as oxygen, nutrients, vitamins, antibodies and water diffuse from the lacunae into fetal capillaries
  • fetal waste diffuses from the lacunae into the maternal blood vessels
110
Q

amniotic sacs

A

series of membranes developed by the foetus, which contain amniotic fluid which supports and protects the developing fetus

111
Q

what is the basic functional unit of the placenta?

A

a finger-like piece of fetal tissue (placental villus)

112
Q

why do these villi increase in number during pregnancy?

A

to cope with the increasing demands of the foetus for the exchange of materials with the mother

113
Q

where does maternal blood flow in the placenta?

A

in the intervillous spaces around the villi

114
Q

where does foetal blood flow in the placenta?

A

in blood capillaries, close to the surface of each villus

115
Q

placental barrier

A

cells that separate maternal and fetal blood (selectively permeable)

116
Q

draw a diagram of placenta

A

p507

117
Q

describe exchange of materials between mother and foetus

A

mother -> foetus:
- oxygen (diffusion)
- glucose (facilitated diffusion)
- antibodies (endocytosis)
- water (osmosis)

foetus -> mother:
- urea
- carbon dioxide (diffusion)
- water (osmosis)

118
Q

role of placenta in oestrogen and progesterone production

A

by about the 9th week of pregnancy, the placenta secretes these hormones in large enough quantities to sustain the pregnancy so the corpus luteum is no longer needed

119
Q

what is birth mediated by?

A

positive feedback involving oestrogen and oxytocin

120
Q

role of progesterone in parturition

A

during pregnancy, progesterone inhibits secretion of oxytocin by the pituitary gland and contractions of myometrium (contractions of the muscular outer wall of the uterus).

at the end of pregnancy, hormones produced by the foetus signal to the placenta to stop secreting progesterone, and oxytocin is therefore secreted

121
Q

role of oxytocin in parturition

A

positive feedback system:
- oxytocin stimulates contractions of the muscle fibres in the myometrium
- these contractions are detected by stretch receptors, which signal to the pituitary gland to increase oxytocin secretion
- this makes contractions more frequent and vigorous

122
Q

what is the advantage of this positive feedback system?

A

causes a gradual increase in the myometrial contractions, allowing the baby to be born with the minimum intensity of contraction

123
Q

describe parturition

A
  1. relaxation of muscle fibres in the cervix causes it to dilate
  2. uterine contraction bursts amniotic sac and amniotic fluid passes out
  3. further uterine contractions push the baby out through the cervix and the vagina
  4. placenta and umbilical cord expelled rom body
124
Q

precocial state

A

hatched or born in an advanced state and able to feed itself and move independently almost immediately.

125
Q

mammals with a large body size are more likely to be

A

precocial - this is correlated with a long gestation period

126
Q

altricial state

A

relatively helpless, incompletely developed offspring

127
Q
A

IB biology (60 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions