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Biology > Module 5.1 - Homeostasis and Communication > Flashcards

Module 5.1 - Homeostasis and Communication Flashcards

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1
Q

What is homeostasis? (2)

A
  • Maintenance of constant internal environment
  • Metabolic processes that respond to changes in an organism’s external and internal environment
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2
Q

Why does homeostasis occur? (1)

A
  • To increase the chances of survival by avoiding harmful environments
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3
Q

What is the change in the internal/ external environment called? (1)

A
  • Stimulus
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4
Q

Receptors? (3)

A
  • Detect stimuli
  • Specific to one type of stimulus
  • Can be cells or cell membrane proteins
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5
Q

Effectors? (2)

A
  • Cells that respond to stimulus
  • Muscles or glands
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6
Q

What is cell signalling? (4)

A
  • Cells communicated with other cells to produce a response
  • Nervous system communicate via secreting neurotransmitters
  • Hormonal system release hormones
  • Cell-surface receptors recognise these chemicals secreted
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7
Q

Why is homeostasis important? (2)

A
  • Controls internal environment to allow optimum functioning for cells
  • Controls temperature, pH and concentration of ions
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8
Q

Why is homeostasis important for enzyme control? (3)

A
  • Enzymes control the rate of metabolic reactions
  • If body temperature is too high, enzymes can become denatured leading to low metabolic activity
  • If body temperature is too low, metabolic rate & activity becomes slow
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9
Q

How do enzymes become denatured? (4)

A
  • Enzyme’s molecules vibrate too much
  • Hydrogen bonds break changing tertiary structure
  • Enzyme can no longer work as an efficient catalyst
  • Metabolic reactions are less efficient
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10
Q

What is negative feedback? (4)

A
  • Effectors responding to stimulus
  • To counteract a change where internal environment has been shifted away from the norm
  • Negative feedback may not work if change is too big
  • e.g. Huge drop in body temperature due to prolonged exposure to the cold
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11
Q

What is positive feedback? (4)

A
  • Effectors responding to stimulus to rapidly activate something
  • e.g. blood clot
  • To amplify a change to push internal environment away from its norm
  • Positive feedback isn’t apart of homeostasis
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12
Q

Describe the feedback process of a blood clot (4)

A
  • Platelets activated and chemical cascade begin
  • The increase in activating platelets is the positive feedback
  • Blood clot forms
  • Negative feedback begins to stop
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13
Q

What are the types of neurones? (3)

A
  • Sensory
  • Relay
  • Motor
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14
Q

Structure of a neurone generally? (3)

A
  • Cell body with nucleus
  • Dendrites and dendrons
  • Axon
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15
Q

Structure of myelin sheath? (2)

A
  • Made of Schwann cells
  • Between Schwann cells are nodes of Ranvier
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16
Q

Sensory neurone? (5)

A
  • Transmit impulses from receptors to CNS
  • Myelinated
  • Short dendrites
  • One long dendron
  • Short axon
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17
Q

Relay neurone? (3)

A
  • Transmit impulses between sensory and motor neurones
  • Non-myelinated
  • Many short dendrites
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18
Q

Motor neurone? (4)

A
  • Transmit impulses from CNS to effectors
  • Myelinated
  • Many short dendrites
  • Long axon
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19
Q

Steps in neuronal communications: (6)

A
  • Stimulus
  • Receptors detect
  • Impulses sent through the sensory neurone to CNS
  • CNS processes information and coordinates response
  • Impulses sent through the motor neurone to effectors
  • Effectors respond to stimulus
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20
Q

Why are sensory receptors known as transducers? (2)

A
  • They convert different forms of energy into electrical energy
  • Electrical energy = nerve impulses
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21
Q

Resting potential? (4)

A
  • Potential difference at rest = resting potential
  • Membrane is polarised at -70mV
  • Outside of membrane is relatively positively charged compared to inside membrane
  • As there are more positive ions outside of cell
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22
Q

Generator potential? (3)

A
  • Stimulus detected
  • Cell membrane excited
  • Difference in charge inside and outside cell = change in potential difference = generator potential
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23
Q

Action potential? (3)

A
  • The bigger the stimulus; the bigger the movement of ions; the bigger the change in potential difference
  • If potential difference is big enough it’ll trigger an action potential
  • Weak stimulus = weak generator potential = no action potential
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24
Q

Threshold level (1)

A
  • Level of generator potential needed for action potential
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25
Q

How is resting potential maintained? (2)

A
  • Membrane permeability
  • Sodium-potassium pumps
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26
Q

Membrane permeability: (4)

A
  • Membrane isn’t permeable to Na+
  • Na+ can’t diffuse back in
  • Creates sodium ion electrochemical gradient
  • Membrane is permeable to K+
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27
Q

Sodium-potassium pumps? (3)

A
  • 3 Na+ ions move out of neurone for every 2 K+ that move in
  • K+ move through K+ channels on membranes
  • ATP is used for this process
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28
Q

What is the cell membrane when it is stimulated? (1)

A
  • Depolarised
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29
Q

Sequence in action potential: (5)

A
  • Stimulus
  • Depolarisation
  • Repolarisation
  • Hyperpolarisation
  • Resting potential
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30
Q

What happens to the cell membrane when a stimulus is detected? (5)

A
  • Stimulus excites membrane
  • Na+ channels open
  • Membrane become permeable to Na+
  • Na+ diffuse in down Na+ electrochemical gradient
  • Inside of neurone becomes less negative
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31
Q

What happens to the cell membrane at depolarisation? (3)

A
  • Potential difference raised from -70mV to -55mV
  • More Na+ ions diffuse in
  • Positive feedback
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32
Q

What happens to the cell membrane at repolarisation? (5)

A
  • Potential difference raised from -55mV to +30mV
  • Na+ channels close
  • Voltage-gated K+ channels open
  • K+ diffuse out down K+ electrochemical gradient
  • Negative feedback as restoration to resting potential begins
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33
Q

What happens to the cell membrane at hyperpolarisation? (3)

A
  • K+ channels are slow to close
  • Overshoot of K+ diffusing out of membrane
  • Potential difference becomes more negative than resting potential
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34
Q

What happens to the cell membrane at resting potential? (2)

A
  • Ion channels are reset
  • Refractory period finishes
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35
Q

Refractory period? (3)

A
  • Period of cell membrane recovery
  • Na+ channels close during repolarisation
  • K+ channels close during hyperpolarisation
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36
Q

How does action potential move down the neurone? (4)

A
  • As a wave of depolarisation
  • Cell 1 depolarises and initiates cell 2 to depolarise
  • Cell 2 depolarises
  • Cell 1 enters refractory period
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37
Q

The “all or nothing” principle? (4)

A
  • When threshold is reached an action potential will fire
  • With the same change in voltage
  • No matter how big the stimulus is
  • Bigger stimulus do increase frequency of action potentials
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38
Q

Action potential in myelinated neurones? (6)

A
  • Saltatory conduction
  • Myelin sheath = electrical insulator
  • Schwann cells prevent impulse passing
  • Impulse needs to jump at node of Ranvier
  • Node of Ranvier can become depolarised
  • Faster
39
Q

Action potential in non-myelinated neurones? (2)

A
  • Impulses travel down whole length of axon membrane
  • Slower than saltatory conduction
40
Q

What is a synapse? (1)

A
  • A junction between a neurone and another neurone or a cell
41
Q

What happens at the presynaptic neurone? (6)

A
  • Action potential reaches synaptic knob
  • Triggers Ca2+ influx
  • Causes voltage-gates Ca2+ channels to open
  • Ca2+ diffuse into synaptic knob
  • Cause neurotransmitters vesicles to fuse with presynaptic membrane
  • Neurotransmitters leave via exocytosis
42
Q

What happens at the synaptic cleft? (4)

A
  • Neurotransmitters released into synaptic cleft
  • Diffuse across to postsynaptic membrane
  • Bind to specific receptors
  • Triggers action potential in the postsynaptic neurone
43
Q

What happens at the postsynaptic neurone? (2)

A
  • Action potential triggers opening of sodium channels
  • Influx in Na+ causes depolarisation
44
Q

What happens to the neurotransmitters after an impulse passes through the synapse? (2)

A
  • Neurotransmitters are removed from cleft and broken down by enzyme
  • They return to the synaptic knob to be reused
45
Q

What is an excitatory synapse? (1)

A
  • Depolarises postsynaptic neurone to trigger action potential
46
Q

What is an inhibitory synapse? (2)

A
  • Hyperpolarised postsynaptic neurone
  • Prevents an action potential
47
Q

What is an synaptic divergence? (2)

A
  • One neurone connect to many neurones
  • Information can be dispersed to many parts of the body
48
Q

What is an synaptic convergence? (2)

A
  • Many neurones connect to one neurone
  • Information can be amplified
49
Q

What is summation? (2)

A
  • Neurotransmitters combine to excite the postsynaptic neurone to meet the action potential threshold
  • Happens when the stimulus is weak
50
Q

Types of summation? (2)

A
  • Spatial
  • Temporal
51
Q

Spatial summation? (3)

A
  • Synaptic convergence
  • Many impulses can be coordinated into one amplified impulse
  • Increases chance of action potential threshold to be met
52
Q

Temporal summation? (3)

A
  • Two or more impulses arrive in quick succession from the same presynaptic neurone
  • Shortens frequency of impulses arriving
  • Increases chance of action potential threshold to be met
53
Q

Why are receptors only on the postsynaptic neurone? (1)

A
  • To ensure impulse only moves in one direction
54
Q

Hormonal system? (1)

A
  • Made of endocrine glands and hormones
55
Q

Endocrine glands? (1)

A
  • Secretes hormones
56
Q

Hormones? (3)

A
  • First messengers
  • Chemical messengers that travel through the bloodstream
  • Bind to specific receptors called target cells
57
Q

What happens when a first messenger binds to a target cell? (2)

A
  • Triggers an enzyme in the cell membrane
  • Which catalyse the production of second messengers
58
Q

What are second messengers? (2)

A
  • Signalling molecules
  • Activate a cascade inside cell
59
Q

Adrenaline? (3)

A
  • First messengers that binds to receptors and activate enzyme adenylyl cyclase
  • Activated adenylyl cyclase catalyses the production of cyclic AMP (cAMP) from ATP
  • cAMP activates a cascade for Glycogenolysis
60
Q

How can glands be stimulated? (2)

A
  • Change in concentration of a substance
  • Electrical impulses
61
Q

Structure of adrenal gland? (3)

A
  • Outer part called cortex
  • Inner part called medulla
  • Both structures are involved in the response to stress
62
Q

Cortex? (2)

A
  • Secrete steroid hormones
  • Cortisol and aldosterone
63
Q

Roles of cortisol and aldosterone? (3)

A
  • Triggers gluconeogenesis to increase amount of energy available so body can respond to situation
  • Increasing blood volume and pressure by up taking sodium ions and water by kidneys
  • Supress the immune system
64
Q

Medulla? (2)

A
  • Secretes catecholamine hormones (modified amino acids)
  • Secretes adrenaline and noradrenaline
65
Q

Roles of adrenaline and noradrenaline? (3)

A
  • Make energy by increasing heart and breathing rate
  • Glycogenolysis
  • Constricts blood vessels so that blood is diverted to the brain and muscle
66
Q

Ectotherms? (5)

A
  • Internal temperature is dependent on external temperature
  • Cannot regulate internal temperature through homeostasis
  • Rely on changing their behaviour
  • Metabolic rates are higher at higher temperatures
  • Generate little heat
67
Q

Endotherms? (3)

A
  • Internal temperature is not dependent on external temperature
  • Regulate internal temperature through homeostasis
  • Have high metabolic rates and generate a lot of heat
68
Q

Mechanisms to reduce body temperature: (3)

A
  • Sweating
  • Hair lie flat
  • Vasodilation
69
Q

Sweating? (1)

A
  • Water in sweat evaporates from the surface of the hot skin cooling the body down
70
Q

Hair lie flat? (3)

A
  • Erector pili muscles relax and hair lie flat
  • Less air is trapped in hairy insulating layer
  • Heat can be lost easier
71
Q

Vasodilation? (2)

A
  • Arterioles near skin dilate for more blood in the capillary
  • More heat is loss through radiation
72
Q

Mechanisms to increase body temperature: (5)

A
  • Shivering
  • Less sweat
  • Hair stands up
  • Vasoconstriction
  • Hormones
73
Q

Shivering? (2)

A
  • Muscles contract in spasms
  • Makes body shiver to produce more heat through increased respiration
74
Q

Less sweat? (1)

A
  • Less sweat is secreted to reduce heat loss via evaporation
75
Q

Hairs stand up? (3)

A
  • Erector pili muscles contract
  • Trapping more air within the hairy insulating layer
  • Reduces heat loss
76
Q

Vasoconstriction? (2)

A
  • Arterioles near skin constrict for less blood in the capillary
  • Less heat is loss through radiation
77
Q

Hormones? (2)

A
  • Adrenaline and thyroxine are released
  • Increase metabolism so more heat is produces
78
Q

What is role of the hypothalamus in controlling body temperature? (1)

A
  • Hypothalamus receives information from thermoreceptors and coordinates a response to increase or reduce temperature
79
Q

Types of thermoreceptors: (2)

A
  • Thermoreceptors in hypothalamus detects change in internal temperature (through blood temperature)
  • Thermoreceptors in the skin (peripheral temperature receptors) detect external temperature
80
Q

How are the levels of glucose controlled? (1)

A
  • Through the hormonal system with the help of insulin and glucagon
81
Q

From where are insulin and glucagon secreted from? (3)

A
  • From a cluster of cells called the Islets of Langerhans
  • Alpha cells secrete glucagon
  • Beta cells secrete insulin
82
Q

Role of insulin and glucagon: (2)

A
  • Insulin lowers blood-glucose concentration
  • Glucagon increases blood-glucose concentration
83
Q

How does insulin work? (3)

A
  • Binds to receptors on liver and muscles cell membranes which increases its permeability to glucose so that more glucose is taken up by cells
  • Activates enzymes involved in glycogenesis
  • Increases the rate of respiration of glucose
84
Q

How does glucagon work? (2)

A
  • Binds to receptors on liver cell membranes and activates enzymes involved in glycogenolysis and gluconeogenesis
  • Decreases the rate of respiration of glucose
85
Q

When do beta cells secrete insulin? (1)

A
  • When cells are depolarised
86
Q

How do beta cells secrete insulin? (5)

A
  • Glucose enters cell by facilitated diffusion
  • More glucose in beta cell causes the rate of respiration to increase
  • More ATP is produced which triggers K+ ion channels to close
  • This causes a build-up of K+ ions inside the cell and the cell become depolarised
  • Depolarisation triggers Ca2+ channels to aid insulin-stored-vesicles to leave the cell via exocytosis
87
Q

When does diabetes occur? (1)

A
  • When blood glucose concentration is not controlled
88
Q

Type 1 diabetes? (6)

A
  • Auto-immune disease where body attacks beta cells
  • No insulin is produced
  • So when blood glucose concentrations rises it remains high
  • Glucose can’t be absorbed by the kidney and is excreted through urine
  • Develops in children or young adults
  • Can be hereditary
89
Q

How do you treat Type 1 diabetes? (3)

A
  • Insulin therapy through insulin injections or insulin pumps
  • Islet cell transplantation
  • Lifestyle changes such as monitoring diet and increased physical activity
90
Q

Type 2 diabetes? (3)

A
  • Beta cells don’t produce enough insulin or insulin receptors are faulty
  • Develops later on in life
  • Linked to obesity
91
Q

How do you treat Type 2 diabetes? (3)

A
  • Lifestyle changes such as eating a balanced diet, regular exercise and loosing weight
  • Medication such as metformin, sulfonylureas and thiazolidinediones
  • Insulin therapy
92
Q

Why is using genetically modified bacteria to produce insulin a good alternative to animal pancreas extractions? (5)

A
  • Cheaper
  • Larger quantities
  • GM bacteria makes human insulin which more effective than using pig or cattle insulin
  • Less likely to trigger and immune response
  • May be ethically and religiously preferred
93
Q

How can stem cells be used to cure diabetes? (1)

A
  • Can be grown in beta cells for transplantation

Biology (10 decks)

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