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Biology 2 > Animal Physiology > Flashcards

Animal Physiology Flashcards

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1
Q

List the processes involved in animal physiology

A
  • Energy
  • Maintenance
  • Moving
  • Sensing & Coordination
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2
Q

What is the term used to describe the inside of an internal environment?

A

-Extracellular fluid

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3
Q

Where did the word ‘Homeostasis’ come from?

A
  • 1872 Claude Bernard ‘Constancy of the internal environment is the condition of free life’
  • Walter Cannon then coined ‘Homeostasis’
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4
Q

What are the proportions of total body water in vertebrates?

A
  • 1/5 is blood plasma
  • 4/5 is interstitial fluid
  • 1/3 is extracellular fluid in non-vertebrates
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5
Q

What is the resting membrane potential?

A
  • A difference in electrical voltage across a cell membrane, forming a ‘cell battery’
  • The inside is maintained at 60 to 80 mV to the outside
  • Measured using a intracellular microelectrode
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6
Q

Why is the ‘Cell battery’ important?

A
  • Used to make electrical signals

- Move things across the membrane, absorption in gut, water and salt balance in teleost fish, regulate cell volume…

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7
Q

How is the cell’s resting potential maintained?

A
  • Unequal distribution of K+ ions between inside and outside of cel;
  • Selective permeability of resting cell membrane to K+
  • There is a equilibrium between the two gradients across the membrane, electrical gradient and concentration gradient
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8
Q

Which proteins Maintain the cell resting potential?

A
  • Sodium-potassium exchange pump - uses ATP to export 3 Na+ ions and import 2 K+ ions in the cell
  • Potassium channel - no ATP required just allows for K+ ions are able to pass through the aqueous pore, use diffusion
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9
Q

What did Walther Nernst win the Nobel prize for?

A
  • The Nernst equation - to work out the K+ equilibrium

- Problem is that resting membrane is slightly permeable to Na+

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10
Q

What is the function of neurons?

A
  • Receive, sort out and transmit electrical signals
  • Signals produced by currents flowing through ion channels in cell membrane
  • Signals within a single neuron are called spikes/action potentials/impulses
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11
Q

What is the major difference in dendrite and axon channel activation?

A
  • Dendrite is chemically activated

- Axon is voltage activated

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12
Q

What are cells that make cause spikes called?

A

-‘Excitable’

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13
Q

Describe a spike

A
  • Brief, pulse-like electrical event
  • Travels by propagating
  • Triggered when local electrical signal is strong enough/exceeds threshold
  • Stereotyped event (all-or-none)
  • Membrane potential reverses in polarity, inside becomes more +ive than outside
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14
Q

Describe the nature of stimulating a spike

A
  • Spikes usually around 1ms

- Amplitude of stimulus doesn’t affect the mV of spike

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15
Q

What are the structure of a axon?

A
  • Dendrite
  • Cell Body
  • Axon hillock
  • Axon
  • Axon terminals
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16
Q

What are dendrites used for?

A
  • Collect signals from other neurons

- If signals from dendrites is enough to excite the axon hillock, spike it formed

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17
Q

What is the function of a spike?

A
  • Boosts the size of a small signal
  • Carries electrical excitation along axon
  • Without spikes signals would fade in a short distance
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18
Q

How long does a spike take to travel from the base of your spine to your toe?

A

-1/100s

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19
Q

What are the factors that affect the speed of which a spike travels?

A
  • Axon width
  • Temperature
  • Myelin
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20
Q

What type of travel does myelin sheath cause?

A

-Saltatory conduction - jumping from node to node

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21
Q

What are the 5 phases of a spike?

A
  • Resting potential
  • Threshold
  • Rising phase
  • Falling phase
  • Recovery
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22
Q

Which ion channels are involved in causing a spike?

A
  • Potassium ion channels

- Voltage-gated Sodium ion channels

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23
Q

Describe how Voltage-gated Sodium ion channels act during a spike

A
  • If excited Na+ channels open
  • Na+ enters via diffusion
  • This makes axon less negative, opening more Na+ channels.
  • Na+ channels then close and become inactive
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24
Q

Describe how Potassium ion channels act during a spike

A
  • Open after the Na+ channels are closed and K+ leaves the axon via diffusion
  • Different to the K+ channels used to maintain resting potential
  • Open more slowly than the Na+ channels, to allow for spike to occur
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25
Q

How long is a refractory period?

A

-1/2 ms

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26
Q

Where has most spike information come from?

A

-A giant axon from squid in the english channel used to cause jet propulsion in squid

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27
Q

What did Hodgkin and Huxley find?

A
  • The resting potential of +50mV
  • The cytoplasm ion composition was different than bathing fluid
  • Intracellular recording found polarity reversed
  • Separate out currents carried by Na+ and K+
  • Sequence of events
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28
Q

List three types of neurons

A
  • Cerebral cortex (Pyramidal cell) - Some neurons brand over a broad area, communicate over long distances via long axons
  • Retina (bipolar cell) - Short axon with few dendrites
  • Cerebellum (purkinje cell) - Bushy dendrites collect information from many other cells
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29
Q

List 4 structure specialised to synapses

A
  • Junctional fold
  • Synaptic cleft
  • Active zone with synaptic vesicles
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30
Q

List two neurotransmitters

A
  • Acetylcholine

- Glutamic acid

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31
Q

How does a synapse work?

A
  • Neurotransmitter is released when presynaptic terminal is excited
  • Vesicles fuse with presynaptic membrane
  • Transmitter crosses narrow synaptic cleft
  • Some bind to and opens ion channels on surface of post-synaptic membrane
  • Ions carry electrical current through channels
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32
Q

What evidence is there for most synapses being chemical?

A
  • Physical gap between 2 neurons at a synapse
  • Applying a particular chemical to a postsynaptic site causes an electrical response
  • Vesicles in presynaptic terminals contain the same chemical that produces the postsynaptic cell’s electrical response
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33
Q

How do electrical synapses work?

A

-Electric current flows directly between neurons

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34
Q

What triggers the release of neurotransmitters?

A
  • Excitation in the presynaptic terminal causes voltage-gated Ca2+ channels
  • Ca2+ enters the presynaptic terminal under a strong electrochemical gradient
  • A increase in Ca2+ triggers a cascade of enzyme-like events that cause vesicles to fuse with presynaptic membrane and release neurotransmitter
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35
Q

Evidence for neurotransmitter release

A
  • Squid giant synapse
  • Involved in jet propulsion
  • Stained two axons in a ‘relay’ synapse
  • Measured presynaptic and postsynaptic terminals
  • Found that pre-potential regulates the amount of neurotransmiter and that regulates size of postsynaptic potential
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36
Q

What is the evidence for Ca2+ entering the presynaptic terminal?

A
  • (Linas and Nicholson 1975)
  • Found that protein Aequorin form jelly fish glows blue in the presence of Ca2+
  • Found light emitted was proportional to postsynaptic potential size
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37
Q

How do ‘non-spiking neurons work?

A
  • Spikes aren’t required and only electrical excitation to open Ca2+ channels in the presynaptic terminal
  • E.g retina
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38
Q

How long is the small delay at the chemical synapse?

A
  • 0.5ms

- Time for Ca2+ channels to open

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39
Q

How do neurotransmitters cause PSPs?

A
  • Neurotransmitters bind to receptor site, causing channel to open
  • Several kinds of neurotransmitter and some inhibit neuron instead of excite
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40
Q

How can we tell if a post-synaptic terminal is excited?

A
  • Patch clamping

- Take one fine channel protein which can be used to measure electrical pulses which run through the neuron

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41
Q

Compare a spike and a psp

A
  • Spike - Voltage-gated channels, 1/10 V, Discrete and fixed amplitude and travel via propagation
  • Psp - Chemical-gated channels, generally few mV, adds with other psps and cannot travel far
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42
Q

How do psps form a spike?

A

-Several psp join to form a spike, which enables nervous system to amke descisions - intergration

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43
Q

How do inhibitory synapses work?

A
  • GABA opens Chlorine channels, allowing for Cl- ions to diffuse into the Post-synaptic terminal
  • Cl- binds with Na+ to reduce psp amplitude
44
Q

Which toxins target Na+-K+ exchange pump?

A
  • Ouabain and digoxin
  • Alkaloid which sticks to the ATPase site on the protein
  • Used clinically for heart treatment
  • Slow-acting around 1.5 hours to reach maximum
45
Q

Which toxins target voltage-gated Na+ channels?

A
  • Tetrodotoxin, found in pufferfish and other
  • Weird biochemical, produced by bacteria in organs and skin
  • Saxitoxin is similar and produced by dinoflagellates
  • TTX forms a strong bond in the ion channel and ‘corks’ the channel
46
Q

Which toxins target Na+ channel inactivation?

A
  • Atracotoxin, found in funnel-web spider

- Toxic to apes

47
Q

Which toxins target voltage-gated K+ channels?

A
  • Tetraethylammonium
  • Apamine, found in bees
  • Dendrotoxin - mambas
48
Q

What are cone snails?

A
  • Largest marine invertebrate genus of 500 spp
  • Diversified rapidly
  • Sub-tropical
  • Dangerous
  • Varied diet-worms, molluscs and fish
  • Modified radula as a toxin-bearing harpoon
49
Q

Which toxins target voltage-gated Ca2+ channels?

A
  • Conotoxins
  • 15-30 amino acid peptides
  • Lots of disulphide bridges
  • ~100 distinct toxins per species
  • 50,000 toxins in genus
50
Q

What types of conotoxins are there?

A
  • Alpha-conotoxins, nAch receptor
  • mu-conotoxins, muscle v-gated Na+ channels
  • Omega-conotoxins, v-gated Ca2+ channels
51
Q

Which toxins target neurotransmitter release?

A
  • Exocytosis inhibited
  • Botulinum toxin blocks exocytosis
  • Black widow spider venom causes uncontrolled exocytosis
52
Q

What are the various neurotransmitters used?

A
  • Vertebrates - Acetylcholine

- Arthropods - Glulatic acid

53
Q

How does alkaloid curare work?

A
  • Stops acetylcholine form binds to receptors
  • Muscle relaxant used in clinics
  • E.g Alpha bungarotoxin
54
Q

Give a brief description of snake venoms

A
  • 2,700 spp but only 300 toxins

- Can either be haemotoxic or neurotoxic

55
Q

Give a brief description of spider venoms

A
  • Multi-component polypeptides which block glutamate receptors
  • E.g Strychnine, blocks glycine receptors
56
Q

What does Eserine do?

A
  • Interacts with acetylcholinesterase

- A potentiator

57
Q

Define ‘transduction’

A

-Conversion of one form of energy into another

58
Q

What is special about sensory neurons?

A

-Contain dendrites which specialise in transduction of particular stimuli e.g pressure, heat and light

59
Q

How does stimulus transduction work?

A

-Alters the ion flow across cell membrane to cause a receptor potential

60
Q

Describe the abdominal stretch receptor in a crayfish

A
  • ‘Muscle receptor organ’
  • Mechanoreceptor
  • 4 per segment
  • Detects downward tail bending in specialised receptor muscle
  • If stimulus is sufficient then axon hillock will produce a spike
61
Q

Define a ‘proprioceptor’

A

-A sense organ that monitors the position or a change in position of an animal’s body parts

62
Q

What is linked to spike strength?

A

-The stronger the spike the higher the spike rate

63
Q

What is adaptation? (sensory neuron)

A
  • Allows sensitivity to changing stimuli
  • ‘Anti-tickle’
  • Be able to distinguish from fatigue and habituation
64
Q

What are hair cells in vertebrates?

A
  • Found in lateral line system of fish
  • Signals about water movement
  • Found in balance organs of other vertebrates
  • Cells with cilia that are able to be excited
65
Q

How are hair cells used to detect sound?

A
  • Sounds are pressure waves

- Need to distinguish between tone (tonotropic organisation), loudness (amplitude of potentials) and source

66
Q

List the range of tones for Humans, Dogs and Bats

A
  • Humans - 10 Hz to 20 kHz
  • Dogs - 40 Hz to 60 kHz
  • Bats - 20 Hz to 150 kHz
67
Q

List the structures of the mammalian inner ear

A
  • Tectorial membrane
  • Outer hair cells
  • Inner hair cells
  • Basilar fiber
68
Q

How do hair cells transduct sound?

A
  • Detect vibrations from the tympanic membrane
  • 3,500 inner hair cells directly release transmitter
  • 40,000 sensory axons in brain which cause spikes to occur
  • 12,500 outer hair cells, regulating the sensitivity of the ear
  • The basilar membrane can regulate it’s stiffness
69
Q

What is tonotopic organisation?

A

-When the best tone for a receptor cell depends on it’s location along the basilar membrane

70
Q

Define ‘metabotropic’ and ‘ionotropic’

A
  • Metabotropic - Receptors which are indirectly linked to the ion channels
  • Ionotropic - Receptors which are directly linked to the ion channels
71
Q

What are photoreceptor cells?

A
  • Cells that transduce light into receptor potentials
  • Vertebrates have 2 types: Rods - Broad colour sensitivty and low light levels, Cone - Particular colours (three types) and good for detail in bright light
  • Contain photo-pigments called discs
  • Metabotropic receptors
72
Q

Describe the function of a photoreceptor cell

A
  • In dark, Na+ channels are kept open, resting potential is kept at -35 mV (held open by cGMP)
  • Light causes the transducin to change shape, activating phosphodiesterase (PDE)
  • PDE hydrolyses cGMP to GMP, closing the Na+ channels
73
Q

Define ‘rhodopsins’

A
  • The photo-pigments
  • Two parts - Opsin (protein) and 11-cis-retinal (light-absorbing aldehyde) turns to all-trans-retinal with absorption of light
74
Q

List the enzyme-like reactions that rhodopsins induce

A
  • Activates transducing in disc membrane
  • Activating phosphodiesterase, which hydrolyses cGMP
  • Causing hyperpolarisation in vertebrates, depolarisation occurs in invertebrates
75
Q

How does a photoreceptor adapt to dark light?

A
  • One photon of light causes 1-5mV receptor potential
  • But under normal like, hundreds of thousands of photon/per sec
  • As light intensity increases, sensitivity decreases
76
Q

How are photoreceptor cells coded?

A

-Equal contrasts in stimulus strength cause equal increments in response

77
Q

How are images processed in the retina?

A
  • 5 layers of neurons with photoreceptors at the back
  • Front have retinal ganglion cells, long axons which go into the brain (use spikes), more ganglion cells then photoreceptor cells
  • Bipolar cells connect photoreceptor cells to ganglion cells
  • Horizontal cell, which modify signals to bipolar cells
  • Amacrine cell modify signals passing from bipolar to retinal ganglion cells
78
Q

What is lateral inhibition?

A
  • Responses in one area inhibit responses in neighbouring areas
  • Small spots generate larger responses than blobs
  • Enhances the detection of edges in images
  • Basis of several illusions
79
Q

List 7 areas of the mammalian brain and their functions

A
  • Cerebral hemisphere
  • Thalamus - Relay station for sensory information
  • Hypothalamus and Pituitary - control centre for hormones
  • Cerebellum - ‘Little brain’ coordinates movement sequences
  • Pons and Medulla - Autonomic function
80
Q

What is the cerebrum?

A
  • 2 cerebral hemispheres
  • Small in fish, amphibia and reptiles
  • Larger but smooth in birds
  • Large and folded in mammals and cetaceans
  • L and R hemisphere receive sensory information from opposite sides of body
  • Major roles in sensory perception, learning, memory and conscious behavior
  • 6 layers of neurons
81
Q

Describe the pyramidal neuron

A

-Pyramid-shaped cell body
-Most numerous excitatory cell type in cerebrum
-Inputs from thousands of excitatory and inhibitory synapses
-

82
Q

Describe the spindle neuron

A
  • Fewer dendrites than a pyramidal neuron and a smaller cell body
  • Very rare
  • 2 brain regions of apes, they are very prevalent
83
Q

What is a sensory homunculus?

A

-A ‘nerve-weighted man’

84
Q

What are mirror neurons?

A
  • Visual neurons which respond to the sight of objects moving in particular ways
  • Certain action doesn’t have to be committed by oneself
85
Q

How does facial recognition work?

A

-Part of temporal lobe as it becomes active when subject is shown faces

86
Q

What is the ‘Grandmother cell’ concept and what is a more accepted concept of facial recognition?

A
  • Somewhere in your brain there is a neuron which allows you to recognise your grandmother
  • More likely it’s the combining of several features in the brain
87
Q

Define ‘receptive field’

A

-The area of space within which a stimulus causes a response in the neuron

88
Q

Describe a Retinal ganglion receptive field

A
  • Two parts, the centre and surround, which have opposite effects on the ganglion cell’s response
  • Centre-surround receptive field shown by Kruffler 1953
  • Define where edges and boarders
  • Some are ‘on-centre’ and some ‘off-centre’
89
Q

What did Hubel & Wiesel find? (1959)

A
  • Found that light spots and dark spots didn’t give much response
  • Found line and edges give vigorous response
90
Q

What types of primary cortex cells are there and what are their functions?

A
  • ‘Simple’ cells to see edges and lines
  • ‘Complex’ cells to see orientation
  • ‘Hypercomplex’ cells tp see shapes more complex than a single bar
91
Q

How do muscle spindles work?

A
  • Act as a mechanoreceptor for muscles

- Stretch to cause a receptor potential

92
Q

What is spatial summation?

A

-The process of multiple psps joining together to form a spike

93
Q

Why are antagonistic muscles important?

A

-To prevent any damage from occurring in the muscle cells

94
Q

What is temporal summation?

A

-The process of multiple psps joining together over a period of time to form a spike

95
Q

Describe the gill withdrawal process in Aplysia

A
  • Graded in strength with stimulus
  • Temporal & spatial summation
  • 24 sensory neurons
  • 6 motor neurons
  • Direct chemical synapses
96
Q

Describe the inking process in Aplysia

A
  • Same sensory neurons as gill withdrawal but different muscles and motor neurons used
  • Strong signal needed due to shared electrical neurons
97
Q

Describe ‘habituation’ and ‘facilitation’

A
  • ‘Habituation’ - wane in response with repeated stimulus

- ‘Facilitation’ - increased response when preceded by a different noxious stimulus

98
Q

What are muscle cells specialised in?

A

-Generation of force and movement using ATP, require switching on and off

99
Q

What various types of muscles are there?

A
  • Skeletal muscles - used for voluntary movements

- Muscle fibres - cylindrical cells fuse end-to-end, formed from fibre bundles called myofibrils

100
Q

What do myofibrils contain?

A

-Contractile proteins,, actin, myosin and control proteins

101
Q

What are sarcomeres?

A
  • Reapeating units along myofibrils, basic functional units of muscle
  • 2.0-2.6um long in vertebrate skeletal muscle
  • Z lines border adjacent sarcomeres, provide an anchor for actin filaments and for titin
102
Q

How the contractile proteins function?

A
  • Myosin head site binds to actin, forming ‘cross bridge’

- Myosin head has ATPase activity

103
Q

How to take a muscle to bits

A

-‘Skinning’ - place in cold glycerol to remove cell and other lipid membranes, so you can alter the fluid bathing the filaments
-Separate actin and myosin from each other when no Ca2+ is present
-

104
Q

What did Huxley and Huxley find?

A

-Length of thick and thin filaments does not change when muscles contract and the extent of their overlap does change

105
Q

How does the cross bridge cycle work?

A
  • A cross bridge attaches actin to myosin giving the sarcomere strength
  • The cross bridges rotate, moving actin past myosin and shortening the sarcomere
  • The greater the number of cross bridges formed the stronger the sarcomere is
106
Q

Explain the sliding filament theory

A

-

Biology 2 (10 decks)

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