Comparative sensory physiology Flashcards
1
Q
What are photoreceptors
A
cells that contain molecules (opsins) which absorb photons in their external membrane. Absorb light
2
Q
How can photoreceptors increase efficiency of trapping light
A
the cell is expanded into discs or finger like rods. More membrane, the more receptive you are to light
3
Q
Vertebrate rods and cones
A
has photoreceptive opsin molecules. Stacked discs. Connecting cilum. Light is hyperpolarised
4
Q
Invertebrate retinula cells
A
cell body. Rhabdomere formed by microvilli. Light depolarises
5
Q
Vertebrate eye
A
Cornea - 70% of focusing power.
Lens - 30% of focus
Photoreceptors around outside.
Optic disc (blind spot). Optic nerve
6
Q
Why do we have discs in the eye
A
Opsins are membrane bound so having the discs greatly increase their number in each photorector greatly improving light trapping efficiency.
7
Q
Are cones or rods more responsive to light
A
rods
8
Q
Are rods colour sensitive
A
no
9
Q
Why do rods remain active at low light levels
A
Rods have more discs and so more opsin – containing membrane in the outer segment
10
Q
How are Na+ and Ca2+ channels kept open in the dark
A
by high levels of cGMP
11
Q
Depolarization of photoreceptors
A
increases transmitter release - do not produce action potentials
12
Q
What does light activate
A
Transducin to break down cGMP into GMP
13
Q
What do low levels of cGMP cause
A
ion channels to close, hyperpolarising the cell and reducing transmitter release
14
Q
What are4 the 4 photoreceptors
A
blue cones, green cones, red cones and rods
15
Q
Which photoreceptor is active at low light levels
A
rods - we have no colour perception
16
Q
Colour perception in bright light
A
sensitive to red, green and blue light (trichromatic vision)
17
Q
Which animals have no visual processing in their forebrain
A
reptiles, amphibians and fish because they have small rudimentary forebrains
18
Q
Where does visual processing take place in reptiles etc
A
in the visual part of the mid brain (the optic tectum)
19
Q
Visual area in the midbrain in mammals
A
involved in visual reflexes, turning to look at new objects appear in the visual fields
20
Q
Lens in the eye for a bird
A
has a foveal base which acts to create a telephoto system. Visual activity in the medial fovea is 2-3 x that of a man
21
Q
Avian vision
A
medial fovea - side vision. Retina and a fovea
22
Q
What is the problem with avian vision
A
when the bird dives the head faces forward but the visual axis of the telephoto system is at 40 degrees to the direction of flight - turning head increases drag. Their solution is to fly along a curved flight path to keep prey image in the medial fovea
23
Q
In invertebrates what does light activate
A
phopholipase C to break down PIP2 to IP3 and DAG. This opens ion channels causing photorecptor to depolarise (no action potentials)
24
Q
Photoreceptors in polychaete (marine worm) and in a flat worm
A
rhabdome, pigment cell
25
photoreceptor in cnidarian (box jelly fish)
cornea, lens, pigment cell, rhabdome, pigment granules
26
What are compound eyes made up of
photoreceptor units each with its own lens (may vary in sensitivity)
27
What does the shape of compound eyes allow for
bulbous shape provides all round vision
28
Compound eyes - fossil recording
First appeared in fossil recording early predators such as the 500 million year old (pre-Cambrian) Anomalocaris found in deposits in Kangaroo Island, Australia and the Burgess shales in Canada
29
What is the optical unit that makes up the compound eye
ommatidium
30
Ommatidium structure
lens, pigment cells, photoreceptors (R1-8), rhabdomeres
31
What can central rhabdomeres sometimes be sensitive to
UV light
32
What light is detected in compound eyes
light polarised parallel to the direction microvilli is detected
33
What do the outer rhabdomeres (1-6) detect
the direction of the microvilli
34
Microvilli in the central rhabdomeres (7 lies on top of 8)
microvilli only run in one direction so they are sensitive to light polarisation. This aids navigation as the light is polarised in concentric circles around the sun
35
What do flowers pollinated from these insects usually have
patterns visible in UV light that guide them to the source of nectar and pollen (co-evolution)
36
Why do flies have limited behavioural repetoire
Computational resources in the invertebrate nervous system are limited have – e.g., the fly brain contains only around 250,000 neurones
37
What can the fly visual system also recognise
1. Movement (which may indicate danger or mating displays)
2. Looming (approaching) objects e.g., for collision avoidance when flying
3. Visual field slippage – indicates movement relative to the ground an also turning
38
Simple eyes (ocelli) features
smaller than compound eyes. Many receptors under a single lens
39
Hunting spiders simple eye distribution
distributed around the head to provide a wide field of view
40
What do insects with simple eyes usually have
have 3 simple eyes arranged in a triangular patten. When flying, these eyes act as a horizon detector so that the insect can maintain a stable flight path
41
What can Cephalopods (octopus/squid) do
They can change their skin colour patterns and texture rapidly for camouflage and signalling
42
Cuttle fish visual subterfuge
The male is displaying to the female to encourage her to mate. The side of his body facing her shows male patterning. This could attract rival males who would try to compete with him for the female. So on the side of his body away from the female he shows female patterning
43
Infra-red vision in snales
detect heat. Part of the somatosensory system and does not recieve signals from their eyes. Works because of the snakes low body temperature so receptor is kept cool
44
Where is visual processing carried out in snakes
in the mid brain optic tectum because the forebrain is primitive
45
How are the 2 types of information superimposed for snake infra-red vision
because the infrared vision of the pit organs also maps onto the optic tectum
46
Which other animals also have information overlap in the optic tectum
Owls, in their auditory and visual maps. Done so their fine directional hearing arguments visual input which may be poor at night
47
How does the pit organs work
The receptor (TRPA1) is like the one in our skin and mouth that detects both noxious heat and chemical heat sensation e.g., chilli powder (caoaicin)
In rattle snakes this becomes sharply active at 28 degrees
Rat snakes does not have effective infrared ‘vision’
48
Parts of the ear
pinna, external ear cannal, ear drum, nerves
49
What does the pinna do
causes vibration of the ear drum, critical in the transduction.
50
Where does transduction take place
cochlea
51
How is sound detected
. Sound is initially detected because it sets up vibrations in the eardrum (tympanic membrane) and amplified by the movement of the ear ossicles in the middle ear
52
Frequency analysis in the cochlea
High frequency selected at the base, lower frequency at the apex.
53
where are cilia present in the ear
against tectorial membrane
54
What does sound cause the basilar membrane to do
causes it to vibrate, causing seterocilia to push against tectorial membrane. Hair cell activates auditory nerve
55
What does how far the wave travels depend on
the frequency
56
insec4t hearing - function of the tympanum
its a thin cuticle that plays the same role as the eardrum in the vertebrates that vibrates more than normal cuticle
57
What calls fo bats use for navigation and catching prey
echolocating calls
58
Bat call frequencies
25-100 kHz
59
What do moths use auditory systems for
to detect predators and take evasive action
60
What can bats detect when hunting
can detect insect wing movement as well as judging how far away they are (size, species)
61
What do male mosquitos use hearing for
to find/detect females by the humming of their wing beats
62
What does the antenna do
resonates at the female wingbeat frequency (360-400 Hz)
63
How do mosquitos detect airbourne vibrations
detected by Johnston;s organ at the base of the antenna. Active processes in the sensory neurones amplify the signal making it extremely sensitive at this frequency
64
What is olfaction
smell
65
What is gustation
taste
66
Insect v vertebrate hearing - complexity
insects do a few things well and have a simple nervous system. Vertebrates have a more complex nervous system and have more flexibility
67
Insect v vertebrate hearing - detecting vibrations
insects detect vibration with a membrane or appendage (antenna/leg). Vertebrates detect them by a tympanic membrane
68
Insect v vertebrate hearing - amplification
insects amplify through active responses of sensory dendrites. Vertebrates have several amplification stages (external hera, ossicles, cochlear amplifier)
69
Insect v vertebrate hearing - tonotopic representation of frequency
insects only rarely present in CNS. vertebrates represent at many levels of the CNS
70
Insect v vertebrate hearing - importance of sound detection
important for insect behaviour (specifc, simple and few signals). Vertebrates also important for behaviour but is more complex
71
Insect v vertebrate hearing - detecting subsonic vibration
important for insect but usually via ahirs, appendages (antennae, cerci). Present in vertebrates (pacinian corpuscles, lateral line organs in fish contain hair cell receptors)
72
5 types of taste sensation
sweet, salt, bitter, sour (acid), umami (glutamate)
73
What does sweet taste indicate
indicates source of energy and ripeness (fruit)
74
What does a bitter taste indicate
poisonous plants/fruits/insects
75
What does a sour taste indicate
spoilage of foodstuffs
76
What is an umami taste
'meaty' taste (MSG)
77
What causes other aspects of flavour
olfaction
78
Taste cell for salt and acid
have Na+ and H+ channels. They depolarise the cell, opening Ca2+ channel and triggering neurotransmitter release
79
Taste cell for bitter, sweet and umami
Have g-protein coupled receptors that bind to molecules causing ion channels to open, thus triggering transmitter release
80
olfactory transduction on olfactory neuron ciliary membrane
Odour molecule bind causing a g protein subunit to stimulate adenylyl cyclase (amplification). This increases levels of cAMP which opens ion channels in the cell membrane causing it to depolarise which causes an action potential to be generated
81
Odour receptor genes in mammals
Mammals have up to 1000 odour receptor genes that allow discrimination of around 10,000 odours
82
sensory transduction - invertebrates
ion channel is opened (gated) by binding an odour molecule
83
sensory transduction - invertebrates
ion channel is opened (gated) by binding an odour molecule
83
sensory transduction - invertebrates
ion channel is opened (gated) by binding an odour molecule
84
Where is the chemosensory receptor located in an invertebrate
on the outer membranes of the cilia
85
Structure of a chemosensory hair
pore, cehmosensory dendrite, cuticle, epidermal cell, mechanosensory dendrite, chemosensory neurones, axon
86
What are pheromones
molecules released by one sex to attract the other e.g., moths. Pheromone receptors can be activated by a single molecule
87
What are on antennas
have a range of different sensory hairs not only olfactory, but also very long fine hairs (airflow) and shorter hairs (tactile) to pick up odours
88
Where do sensory neurons have processes
in the skin/ muscle (tendons/joints), that run into spinal cord cell bodies in the dorsal root ganglia
89
What do sensory neurons give information on
temperature, pain, touch, muscle length/tension to help pick up something
90
what is exteroception
touch, temperature and pain from external stimuli
91
what is proprioception
inside the body like at muscles, tendons and visceral organs
92
what are exteroceptors
sensory endings that monitor interactions with external environment
93
what do glial cells do
encapsulate nerve endings below the surface and modify properties
94
what type of sensation does a naked ending sensory ending detect
pain, temperature
95
what type of sensation does a hair follicle ending sensory ending detect
hair movement
96
what type of sensation does a Merkel's ending (dense on finger pads)sensory ending detect
sustained pressure - detailed mapping oof texture and shape (slow adapting)
97
what type of sensation does a Melssner's ending sensory ending detect
touch - brief response, effective for transient contact (rapid adapting)
98
what type of sensation does a pacinian corpsucle ending sensory ending detect
vibration
99
what type of sensation does a ruffini ending sensory ending detect
shear stress
100
How are axons sent
sent to different ascending tracts (spinal cord to brain) via thalamus project to primary sensory cortex
101
Which two tracts can do similar jobs in different species
spinothalamic or spinocervical
102
What is the primary somatosensory cortex involved in
involved in sensation, proprioception goes there and to the cerebellum
103
What are proprioreceptors
receptors monitoring muscles and joints. Within muscle fibres , to produce the power, there are small spindle shaped structures whose length is monitored by sensory and controlled by motor, Specialized, intrafusal muscle fibres. Spindle – like. Grain of wheat. Power is extrafusal.
104
What are the 3 proprioreceptors
muscle spindles, golgi tendon organs, joint receptors
105
How do muscle spindles work
When the muscle is stretched, the sensory axon in the spindle responds. When the signal reaches the spinal cord, the alpha motorneurons contract the muscle – this may make the spindle slack so it cannot respond to further stretch. So gamma motor neurons fire and the spindle contracts, restoring its responsiveness. Necessary to transmit sensation and keep the system responsive
106
What controls extrafusal fibres
alpha motorneurons
107
What control intrafusal fibres
gamma motor neurons
108
What do golgi tendon organs monitor
stretch in tendons, endings sit in tendons
109
where does our awareness for the relative positions of different parts of the body come from
the activity of the muscle spindles plus the Golgi tendon organs
110
Joint receptors
These endings in the capsule and the supporting ligaments of joints give sensations of pain and discomfort when the joint is moved beyond its range of normal movement. Not indicative if just their positions but more their normal range.
111
example of exteroceptor in invertebrates
Touch/wind sensitive hairs on exoskeleton (trichoid sensillum - “thread like”). Q
Air movement – necessary to flap its wings
112
What is the sensory hair in invertebrates like
quite stiff. Some less stiff are much longer, flexible socket, allow to move. Short – contact
113
What is underneath the sensory hair in invertebrates
have sensory neuron. Contain a modified cilia. Monitors movement. Support cells make up a little package. Action potential then runs to the central nervous system
114
In animals with exoskeletons what mediates exteroception
mechanosensory hairs. These detect not only touch but also air currents and are therefore also important in maintaining flight movements
115
Somatotropy in insects
ganglian for each segment. Thorax, 3 legs, 2 pairs of wings. There are maps; 3 ganglions refer to 3 legs and also possibly a wing on each.
116
What are campaniform sensillae (wasps)
depressions with a floor of very thin cuticle which monitor distortion (loading) of the insect exoskeleton. They buckle under pressure. Under each is a sensory neuron, they are triggered by deformation and fire action potentials.
117
External structures in wasps for detection
insect hair plates and campaniform sensilla
118
Stings from wasps
As the femur rotates upwards, its surface contacts the hair plate on the coxa indicating that it can travel no further. This fulfils the same role as vertebrate joint receptors.
Sting apparatus from the wasp, tells whether sting retracted or pushed out. Joint on the end of the abdomen on wasp. Sting extended, hairs extended. As ting is withdrawn long hairs pressed down
119
What modifies the hind wings in insects
haltere, tell you if its turning and monitors movement of the cuticle
120
How of the oscillating halteres work (insects)
act like gyroscopes as they tend to resist changes in the direction of their movement. When the insect turns during flight this creates strains in the shaft of each haltere that are detected by the arrays of campaniform sensillae that lie at its base (detect deformation as animal rotates)
121
What is at the end of halteres
Have a mass on the end, very thin stalk, move up and down out of phase with wings. Same frequency as wing beat
122
What is the chordotonal organ (insect proprioception)
This lies inside the exoskeleton and is a stretch receptor which has its own tendon, here attached to the fibia crossing joint.
123
What does the chordotonal organ do when the joint is flexed
different sensory neurons detect the position of the joint and the speed of the movement
A group of sensory neurons that respond differently – some slow, some large movement
124
What does the chordotonal organ give information about
movement, detect position of the joint and speed of movement
125
What form muscle receptor organs (crustaceans)
Formed from small accessory muscles that are supplied by the same nerve cells that control the power muscles (I.e., in parallel)
126
What is the muscle receptor organ analogous to (crustacean)
the muscle spindle
127
What movements does the muscle receptor organ monitor
powerful tail flips that are used for escape. DO NOT provide movement
128
Muscle receptor organs - what ae the sensors attached to
special muscle fibres, which adjust the length of these to be put in optimum range
129
Where are ampullae of lorenzi found and what is their function
Found on the sharks and rays, these sensory structures detect the electric fields associated with muscle activity in potential prey species. They also detect temperature.
130
Electroreceptors in other animals
present in the monotremes e.g. duck billed platypus (aquatic) and echidna (terrestrial – spiny anteater) which have ampullae like receptors on the beak/snout.
131
Ampullae of lorenzi - where are the sensory nerve endings
Sensory nerve endings lie at the base of a pit filled with a conductive gel. Prey can be detected even when not visible (murky water or under sand/sediment
132
What are electrical fields used for in fish
detection of prey, navigation and communication
133
What detects the electrical fields
modified muscle cells (which are stacked up like batteries)
134
Why is the signal amplitude kept low in fish
because producing the electric discharge is energetically expensive and can be detected by some predators.
135
How long do elongated muscle cells work for communication in fish
work like battery – different types which stun prey (just a big pulse). Communication, series of pulses for navigation. By the wall, higher frequency
136
Why do birds use magnetic fields
for dircetion during migration but how this is achieved remains highly controversial
137
How can birds detect a magnetic field - magnetic metals
magnetic metal crystals (magnetite – similar to a compass needle) if these were present in nerve cells. - Magnetite granules are present around the beak in some birds but in macrophages, not neurons.
138
How can birds detect a magnetic field - electrorecptors
might be activated by moving through a magnetic field….. but birds don’t appear to have such receptors
139
How can birds detect a magnetic field - magentics and vision
Magnetic sense seems to be linked to vision - It is only present when birds are under full spectrum white light. The current favoured theory is that the magnetic field alters the spin state of high energy electrons generated when photopigments absorb light energy.
