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ocr a level biology > M5-commincation and homeostasis > Flashcards

M5-commincation and homeostasis Flashcards

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1
Q

define homeostasis

A

its the maintenance of a constant internal environment

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2
Q

define positive feedback

A

positive feedback mechanisms amplify a change from the normal level, used to rapidly activate something

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3
Q

why is positive feedback not involved in homeostasis?

A

it does not keep your internal environment constant

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4
Q

what is a stimulus?

A

a change in the internal or external environment

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5
Q

what is a receptor?

A

they detect a stimuli and a re specific

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6
Q

what are effectors?

A

are cells that bring about a response to a stimulus to produce an effect

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7
Q

what does a sensory neurone do?

A

transmit nerve impulses from receptors to the CNS

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8
Q

what does a motor neurone do?

A

transmit nerve impulses from the CNS to effectors

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9
Q

what does a relay neurone do?

A

transmit impulses between sensory neurones and motor neurone

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10
Q

what is the CNS process?

A

stimulus - you see a friend waving

receptor - light receptors (photoreceptors) in you eyes detect the wave

CNS - CNS processes information and decides what to do about it

effectors - muscle cells are stimulated by the motor neurones

response - muscles contract to make your arm wave

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11
Q

what do sensory receptors convert stimulus energy to?

A

nerve impulses

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12
Q

where do axons carry nerve impulses?

A

Away from the cell body

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13
Q

where do dendrites and dendrons carry nerve impulses?

A

towards the cell body

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14
Q

what is the structure of sensory neurones?

A

short dendrites and one long dendron (receptor cells to cell body)

one long axon cell body to CNS)

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15
Q

what is the structure of a motor neurone?

A

many short dendrites (CNS to cell body)

one long axon (cell body to effector cells)

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16
Q

what is the structure of a relay neurone?

A

many short dendrites (sensory to cell body)

one axon (cell body to motor)

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17
Q

what does a bigger stimulus cause?

A

it causes more frequent impulses

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18
Q

what are the synapses called that use acetylcholine?

A

cholinergic synapses

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19
Q

what is acetylcholine broken down by?

A

an enzyme called acetylcholinesterase

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20
Q

what happens at the excitatory synapse?

A

neurotransmitters depolarise the postsynaptic membrane, making it fire an action potential if the threshold is reached

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21
Q

what happens at the inhibitory synapse?

A

when neurotransmitters bind to receptors on the postsynaptic membrane, they hyperpolarise the membrane (making the potential difference more negative), preventing an action potential from being fired

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22
Q

what is synaptic divergence?

A

when one neurone connects to many neurones and information can be dispersed to different parts of the body

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23
Q

what is synaptic convergence?

A

when many neurones connect to one neurone and information can be amplified

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24
Q

why does summation occur?

A

some stimulus are weak so little neurotransmitter is released into synaptic cleft meaning its not enough to excite the postsynaptic membrane to the threshold level and thus stimulate an action potential so summation can combine the effect of neurotransmitters

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25
Q

what is spatial summation?

A

when neurones converge

26
Q

what is temporal summation?

A

is where 2 or more nerve impulses arrive in quick succession from the same presynaptic neurone

27
Q

what does the hormonal system send information as?

A

chemical signals

28
Q

what are hormones?

A

chemical messengers

29
Q

why is hormone a first messenger?

A

because it carries the chemical message from the endocrine gland to the receptor

30
Q

why are signalling molecules the second messengers?

A

they carry the chemical message frim the receptor to other parts of the cell

they activate a cascade inside the cell

31
Q

what type of hormones does cortex secrete?

A

steroid hormones

32
Q

what are 2 examples of steroid hormones?

A

cortisol and aldosterone

33
Q

what type of hormone does medulla secret?

A

catecholamine hormones

34
Q

what are 2 examples of catecholamine hormones?

A

adrenaline and noraadrenaline

35
Q

what is the effect of catecholamine hormones?

A

increase heart and breathing rate

break down of glycogen to glucose

constriction of blood vessels

36
Q

what is the effect of steroid hormones?

A

supress the immune system

increase blood volume and pressure by increasing uptake of sodium ions and water by kidneys

stimulating the break down of proteins and fats, increasing energy available for brain and muscles to respond to the situation

37
Q

what is the endocrine tissue in the pancreas called?

A

islet of Langerhans

38
Q

what do the alpha cells secrete?

A

a hormone called glucagon

39
Q

what do the beta cells secrete?

A

a hormone called insulin

40
Q

under a light microscope, what colour do the alpha cells appear as?

A

pink

41
Q

under a light microscope, what colour do the beta cells appear as?

A

purple

42
Q

what is the stain used to differentiate beta and alpha cells?

A

chrome haematoxylin and phloxine

43
Q

what are ectotherms?

A

they cant control their body temperature internally they control their temperature by changing their behaviour

44
Q

what are 2 examples of ectotherms?

A

reptiles and fish

45
Q

what are endotherms?

A

they control their body temperature internally by homeostasis and they can also control their temperature by behaviour

46
Q

what are 2 mechanism that mammals do to reduce body temperature?

A

sweating - more sweat generated by sweat glands, water in sweat evaporates from surface of skin so skin is cooled

vasodilation - arterioles near the surface of the skin dilate, more blood flows through capillaries in the surface layers of the dermis. more heat is lost from skin by radiation and temp is lowered

47
Q

what are 2 mechanism that mammals do to increase body temperature?

A

vasoconstriction - arterioles near the surface of the skin constrict so less blood flows through capillaries reducing heat loss

hairs stand up - erector pili muscles contract which makes the hair stand up trapping more air and preventing heat loss

48
Q

what does the hypothalamus do?

A

control body temperature

49
Q

what type of food increases blood glucose concentration?

A

carbohydrates

50
Q

what does insulin do?

A

reduce blood glucose concentration when its too high

51
Q

what is the process activated by insulin?

A

glycogenesis

glucose - glycogen

52
Q

what does glucagon do?

A

raises blood glucose concentration when its too low

53
Q

what is the process that is activated by glucagon?

A

glycogenolysis

glycogen – glucose

gluconeogenesis

glycerol/amino acids to glucose

54
Q

what is an example of negative feedback?

A

control of blood glucose

control of body temperature

55
Q

what is an example of positive feedback

A

depolarisation

56
Q

what is type 1 diabetes?

A

it is an autoimmune disease, where no insulin is produced.

in children/ young adults

57
Q

what are the treatments for type 1 diabetes?

A

insulin therapy - regular insulin injections

diet and activity

58
Q

what is type 2 diabetes?

A

when beta cells dont product enough insulin or when the body cells dont respond properly to insulin

linked with obesity

59
Q

what are the treatments for type 2 diabetes?

A

lifestyle changes so exercise, diet,

medication - metformin ( acts on liver cells to reduce amount of glucose that they release into the blood)

60
Q

how can stem cells be used to cure diabetes?

A

they can be grown into beta cells

beta cells will then be implanted into pancreas of a person with type 1 diabetes

person would be able to make insulin as normal

61
Q

what are the pros for using genetically modified bacteria to make insulin?

A

cheaper than animal pancreases

larger quantities produced

religious and ethical reasons - pigs and animals

ocr a level biology (17 decks)

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