50 Sensory and Motor Mechanisms Flashcards
(371 cards)
1
Q
What is the purpose of the star on the star-nosed mole?
A
These 11 pairs of appendages are sensitive to touch. (not smell or light and thy can’t be used for grasping)
2
Q
What are the basic stages of the sensory pathways?
A
Sensory reception, transduction, transmission and perception.
3
Q
What is sensory reception?
A
The detection of a stimulus by sensory cells.
4
Q
What are most sensory cells?
A
Specialised neutrons or epithelial cells.
5
Q
What are some examples of internal stimuli detected by sensory receptors?
A
Blood pressure, temperature and body position.
6
Q
What is transduction?
A
The conversion of a physical or chemical stimulus to a change in membrane potential.
7
Q
How does sensory transduction occur?
A
In all cases the stimuli triggers ion channels of the receptor to open or close. This affects membrane potential. This change is called ‘receptor potential’ and acts are a form of graded potential.
8
Q
What are the two classes of sensory receptors based on how the signal reaches an afferent neuron?
A
1) The ‘receptor is afferent neuron’
2) ‘Receptor regulates afferent neuron’
9
Q
What happens in neurons where ‘receptor is afferent neuron’?
A
The influx/outflow of ions in the ‘receptor potential’ triggers an action potential that carries the signal to the spinal cord.
10
Q
What happens in neurons where ‘receptor regulates afferent neuron’?
A
When the ’sensory receptor cell’ detects a stimulus the movement of ions leads to a receptor potential.
This triggers the release of neurotransmitters form vesicles. These neurotransmitters bind to ‘receptor proteins’ on the afferent neuron which carry the signal to the CNS.
11
Q
How is stimulus intensity portrayed?
A
Since action potentials are ‘all or nothing’ the strength of each signal can not be adjusted.
One alternative is for sensory receptors to trigger action potentials to send action potentials at a low frequency when the stimulus is low. When the stimulus increases action potentials are sent at a higher rate.
The stronger the pressure is on the skin, the more receptors it will activate. Therefore the strength of some stimuli can be conveyed through the number of receptors activates.
12
Q
What is perception in terms of sensory reception?
A
The conversion of the stimuli to perceptions i.e. colours, smells, sounds and tastes.
13
Q
How is the source of the action potential identified?
A
Each sensory neuron has its own nerve fibres. Therefore when that fibres is activated, the brain knows which specific receptor it came form.
14
Q
What is the collection of multiple inputs called?
A
Integration
15
Q
What is an important feature of the sensory transduction pathway?
A
It amplifies the signal so that a low-energy photon can still yield a meaningful response.
16
Q
Besides amplification, what can effect the strength of the signal before it reaches the brain?
A
Adaption.
17
Q
What is adaptation and why is it important?
A
After continued stimulation many receptors undergo a decrease in sensitivity called adaption. This is important as otherwise one would be aware of every heartbeat etc.
This would distract the person from important stimuli.
18
Q
What are the basic types of sensory receptors?
A
Mechanoreceptors, chemoreceptors, electromagnetic receptors, thermoreceptors and pain receptors.
19
Q
What is the basic change mechanorecepotrs detect?
A
Physical deformation caused by mechanical energy such as pressure, touch, stretch, motion and sound.
20
Q
What is the typical structure of a mechanoreceptor and thus how does it sense deformation?
A
Ion channels that are linked to structures outside of the cell such as cilia. The ion channels may also be attached to the cytoskeleton.
If the surrounding tissue is deformed tension will be present in the cilia/cytoskeleton. This opens ht sion channels leading to a ‘receptor potential’ and thus the stimulus has been transduced.
21
Q
Where is a specific place mechanoreceptors are found outside the skin?
A
“Vertebrate stretch receptors” are dendrites of sensory neutrons that spiral round some skeletal muscle fibres. Groups of about 2 to 12 of these fibers, formed into a spindle shape and surrounded by connective tissue, are distributed throughout the muscle.
When the muscle is stretched, the spindle fibres also leading to a signal being transuded.
22
Q
Where is a large concentration of mechanoreceptors found?
A
In the skin.
23
Q
What are the layers of the skin?
A
Form top to bottom: Epidermis, Dermis and Hypodermis
24
Q
What is the hypodermic of the skin?
A
The bottom layer of the skin that contains the nerves.
25
Where are the various mechanoreceptors of the skin found?
Receptors that detect gentle pressure, vibration, and temperature are close to the surface of the skin. Receptors that respond to strong pressure are in deep skin layers.
"Naked dendrites” (dendrites on their own) wind around the base of hairs to detect movement of that hair. Naked dendrites in the epidermis respond to pain
All of these receptors, except the naked dendrites of the epidermis, are found in the dermis layer of the skin.
26
Why are the naked dendrites that surround the hairs important?
They allow the deflections of the hair to be detected. This is especially important in cats etc. that use their whiskers to feel around.
27
What are chemoreceptors divided into?
'General receptors’ that measure total solute concentration and ’specific receptors’ that respond to specific chemicals.
28
What is an example of a ‘general receptor’ chemoreceptor?
“Osmoreceptors” in the brain that detect changes in the solute concentration of the blood and use this to stimulate thirst when osmolarity increases.
29
What are some examples of specific molecules that ’specific receptors’ are often found for?
Glucose, oxygen, carbon dioxide and amino acids.
Also H+ ions to detect pH.
30
What is a common use of chemical receptors outside of mammals?
To detect pheromones.
31
What are electromagnetic receptors?
Sensory receptors that detect electromagnetic energy such as in the forms of light, electricity and magnetism.
32
What are some examples of electromagnetic receptors that detect light?
Photoreceptors in eyes.
Snakes have photoreceptors that are specialised to detect infrared and thus act as thermal cameras to detect the heat of their prey.
33
What are some examples of electromagnetic receptors that detect electricity?
Platypuses have electroreceptors on their bill that detect the electric fields generates by the muscles of crustaceans, frogs and fish etc.
Some fish generate electric currents and then use their electroreceptors to locate prey or other objects that disturb those currents.
34
What are some examples of electromagnetic receptors that detect magnetism?
Many animals such as salmon, pigeons, sea turtles, HUMANS, bees, some molls and a few protists/prokaryotes contain the mineral magnetite.
This magnetite can then be used to detect the earths magnetic field for navigation etc.
35
Where are the thermoreceptors of the skin primarily located?
In the anterior hypothalamus and in the skin.
36
What is the purpose of thermoreceptors in the anterior hypothalamus?
They detect the temperature of the blood and relay this to the posterior hypothalamus (the bodies ’thermostat')
37
How does thermoreception work?
Mammals have a number of kinds of thermoreceptors, each specific for a particular temperature range. At least 6 types of thermoreceptors belong to the TRP (transient receptor potential) family of ion channel proteins.
38
Why does ‘capsacin’ feel hot? What other chemical triggers an opposite response>
It activates the same receptor that is also activated in temperatures greater than 42º C
Menthol (found in mint) feels cold as it activates the same receptors as when temperatures are less than 28ºC
39
How are different temperatures senses?
They body has at least 6 receptors that are activated with different thresholds. For example one activates in temperatures greater than 42ºC and another activates at temperatures less than 28ºC.
40
What are pain receptors formerly called?
Noccioceptors.
41
In humans what form are most noccioceptors?
Naked dendrites that act as nociceptors by detecting noxious thermal, mechanical, or chemical stimuli.
42
How does the inflammatory response directly lead to pain?
The damaged tissues release ‘Prostaglandins’ what make nearby noccioceptors more sensitive and thus increase the pain felt.
43
How is gravity detected in animals?
By statocysts.
44
How do statocysts work?
They consist of a sac covered by cilia on the inside of the wall. The stack contains balls called ’statoliths’ which are grains of sand etc.
As the animal’s orientation changes the statoliths move around the statocyst. This means different cilia and thus different ‘ciliated receptor cells’ are activated.
45
What is the basic principle of sound transduction?
Cilia vibrate in response to sound waves and thus can trigger mechanoreceptors.
Different frequencies cause cilia of different lengths to vibrate and thus pitch can be determined.
46
How do males detect female insects besides with pheromones?
The males have hairs that are tuned to the specific frequency of the wings of a female beating.
47
What is the structure of the ear divided into?
The ‘outer ear’, ‘middle ear’ and the ‘inner ear'
48
What does the ‘outer ear’ include?
The ‘pinna’ (the fleshy bit we see) and the auditory canal which carries sounds collected by the pinna and carries it to the inner ear.
49
What does the middle ear include?
The ’tympanic membrane’ (eardrum) which vibrates as it is hit by sound waves from the auditory canal.
These vibrates hit the malleus (hammer) bone which strikes the incus (anvil bone) and in turn the stapes (stirrup) bone.
The stapes then hits the ‘round window’ causing the sounds to be transferred into the fluid drilled cochlea.
The middle ear is connected to the ‘Eustachian tube’ which leads to the pharynx and thus equalises the pressure of the inner ear to prevent the ’tympanic membrane’ from bursting.
50
What does the middle ear include?
The ’semicircular canals’ which which function in equilibrium, and the coiled cochlea, a fluid-filled bony chamber that is involved in hearing.
51
What is the structure of the cochlea?
When takes in cross section:
The basic structure of the cochlea is a hollow ring of bone.
The upper portion of this ring is the ‘vestibular canal’ and the lower-portion is the ’tympanic canal’. Both canals are enclosed and filled with fluid.
Between the vestibule and tympanic canals is the ‘cochlear duct’ The ‘basilar membrane’ (floor) of this canal has the ‘organ of corti'
52
What is the structure of the ‘organ of corti'?
The organ of Corti is on the floor (basilar membrane) of the basilar membrane
It contains the mechanoreceptors of the ear in the form of hair cells whose hairs project into the cochlear duct. Many of the hairs are attached to the tectorial membrane, which hangs over the organ of Corti like a canopy..
Sound waves make the basilar membrane vibrate, which results in bending of the hairs and thus depolarisation of the hair cells.
53
How specifically do the hairs get deformed enough to trigger a signal?
Vibration of the basilar membrane in response to sound raises and lowers the hair cells, bending the hairs against the surrounding fluid and the tectorial membrane.
54
Why is it important that sound waves travel from the air and into the fluid of the cochlea?
This amplifies them and thus makes them more perceptible.
The ‘hair cells’ also move more in the fluid.
55
What is the fluid in the cochlea called?
Perilymph
56
Where do pressure waves travel after being initiated by the stirs striking the oval window?
Upon entering the vestibular canal, the pressure waves push down on the cochlear duct and basilar membrane. This causes the basilar membrane and its attached hair cells to move up and down and thus leading to the detection of sound.
57
How do the hair cells communicate that they have moved?
In a typical resting state they release a steady stream of neurotransmitters.
As the hairs of the hair cells are hit by the pressure wave they deflect. This triggers mechanoreceptors to increase the rate at which neurotransmitters are being released.
As the pressure wave ends the hairs get pushed in the opposite direction. This causes even less than normal neurotransmitters to be released.
58
What prevents pressure waves from reverberating within the ear/
Once pressure waves travel through the vestibular canal, they pass around the apex (tip) of the cochlea. The waves then continue through the tympanic canal, dissipating as they strike the round window.
59
How does the ear convey volume?
A louder sound leads to greater deflection and thus more frequent action potentials of the cells.
60
How does the ear convey pitch?
The basilar membrane is not uniform along its length: it is relatively narrow and stiff at the base of the cochlea near the oval window and wider and more flexible at the apex.
Therefore each region is tuned to a specific frequency and thus the region with the most action potentials denotes the pitch.
61
Besides hearing, what is a major function of the ear?
‘Equilibrium’ i.e. sensing motion and orientation
62
What are the parts of the ear that determine orientation and motion called?
The vestibular system
63
What are the major structures of the vestibular system?
The semicircular canals, the utricle and the saccule.
64
What are the primary variables the vestibular system detects?
Anglular motion, linear motion and the direction of ‘up'
65
With what is angular motion detected?
The semicircular canals.
66
With what is linear motion detected?
The utricle and saccule
67
With what is the direction on ‘up’ detected?
The utricle and saccule.
68
What is the structure of the semicircular canals?
There are three rings with one on each plane i.e. X, Y and Z.
69
How do the semicircular canals detect angular momentum?
Each of the semicircular canals is filled with fluid (perilymph)
As the canals experience angular momentum this fluid moves through the canal. This causes the hair cells to bend triggering nerve impulses as the frequency of action potentials increases in direct proportion to the angular momentum experienced.
70
What is the structure of the hair cells in the semicircular canal?
Each hair cell is in a small group. This group is then protected by begin enclosed in a “cupula” which is a gelatinous cap that acts as a ’sail’ to increase the surface area exposed to the moving perilymph
71
What is the structure of the utricle and how does this allow them to detect linear motion and the direction of gravity?
The utricle are chambers that are filled with a gelatinous material. Hairs from the wall of these chambers protrude into the fluid.
Embedded in the gelatinous material are many tiny pieces of calcium carbonate called ‘otoliths’
As the head moves these otoliths press on hairs protruding into the gel and thus trigger the ‘hair cell receptor'
72
How are the utricle and saccule arranged and what does this lead to?
The utricle is orientated horizontally and the saccule vertically. Therefore motion can be detected in the forward-back and up-down directions
73
What causes dizziness?
When spinning the fluid and canal eventually come to equilibrium and remain in that state until you stop. At that point, the moving fluid encounters a stationary cupula, triggering the false sensation of angular motion that we call dizziness.
74
How do fishes hear?
Their hearing apparatus does not open to the outside nor contains an eardrum or cochlea.
Instead they have inner ears inside their head. As pressure waves are conducted through the skeleton in moves ‘otoliths’ in this ear. This stimulates hair cells and thus the perception of sound.
75
Besides the inner ear, how can fish detect pressure waves?
They have a ’lateral line’ running down their side.
76
How does a ‘lateral line’ work?
Between their scales is a tube, called the ‘lateral line canal’ through which water can flow.
Along this canal are clusters of hair cells that are encapsulated in a gelatinous cap called the ‘cupula’ Based on the direction and velocity of water flow through the ‘lateral line canal’ the hair cell is depolarised.
77
What is the lateral line system used for?
It detects how fast the fish is swimming and can gauge the direction and velocity of water currents.
It can also detect water movements or vibrations triggered by prey and predators etc.
78
What is the hearing system of amphibians?
Many amphibians have lateral lines in the juvenile form i.e. as tadpoles.
As adults on land they have an ear with the tympanic membrane on the body surface. A single bon conducts the sounds from this tympanic membrane to the cochlea.
79
What is the structure of an eye in simple invertebrates?
They often have two small patches of photoreceptors called ‘ocelli’ on the head region.
A layer of darkly pigmented cells surrounds the ocellus on three sides so that it receives light from only one side.
80
How are ocelli useful?
Because of the dark pigmented cells they only receive light from one direction. Because there is one ocellus on each side of the head the organism can compare the strength of light on the left or the right to move towards or away from the light.
81
What is an example of an organism that uses ocelli to see?
Planarians
82
What type of eyes do insects and crustaceans have?
They have compound eyes made of ‘omatidia'
83
What is the structure of a compound eye?
It consist of many ‘omatidia’
84
What is the structure of an omatidia?
Each omatidia has at the top its own ‘cornea’ then below it a ‘crystalline cone’ These together acts as the ‘lens’ to focus the light.
The focused light is sent into a tube called the ‘rhabdom’ which traps the light. The wall of this tube is made of photoreceptors cels which measure the strength of the light.
85
What are the advantages of ‘omatidia’?
They have a very high “frame rate” so are good at detecting movement which is beneficial in insects.
86
Besides those with ocelli or omatidia, what type of eyes do invertebrates have?
’Single-lens eyes'
87
What are some examples of invertebrates with single lens eyes?
Some jellies and polychaete worms, as well as in spiders and many molluscs.
88
What are the basic structures found in a single lens eyes?
It has a small opening, the pupil, through which light can enter. The pupil can be dilated or contracted by the surrounding iris.
Behind the pupil a single lens per eye focuses this light not the layer of photoreceptors.
89
What basic type of eye do vertebrates have?
Single lens eyes
90
How do the signle lens eyes seen in vertebrates differ from this in invertebrates?
In invertebrates and fish the foci is adjusted by moving the lens forward or backwards.
In vertebrate excluding fish this focusing is achieved by muscles which change the actual shape of the lens.
91
What are ‘omatidia’?
The individual photoreceptor units of a compound eye.
92
What is the the structure of a human eye?
It has the basic shape of a ball. The front edge of the ball is made up of transparent ‘cornea’ while the rest of the eye ball is surround by white ’sclera.’ Interior to the sclera is a thin layer of chorioid which contains many blood vessels to feed the retina which is interior to it.
Behind the cornea is the iris, with aqueous humour between these structures. Light passes through the pupil, a hole in the iris, and passes through the ‘lens’. The shape of the lens is adjusted by the ’suspensory ligament.’
The light passing through the lens reaches the interior of the eyeball, which is filled with vitreous humour. This light is focused onto the retina, a sheet of cells that covers most of the eyeball.
At the far back of the retina is the ‘optic disk’, a blindspot which has not photoreceptors. Behind this is the optic nerve and the ‘central artery’ and ‘central vein’ which provided blood flow to the eye.
93
What is the white exterior of the eye called?
Sclera
94
What is internal to the sclera?
The ‘choroid'
95
What is ’sclera’?
The opaque white exterior of the eye
96
What is ‘choroid’?
The layer of the eye ball between the sclera and the retina. It has many blood vessels to supply the retina.
97
What is the ‘fovea’?
A concentration of cones on the retina meaning this area has particularly acute visual detail i.e. not-peripheral
98
What is region of the retina with many photoreceptors called?
The fovea.
99
What is the outermost layer of the eye through which light can pass?
The cornea.
100
What is the cornea?
The front transparent bit of the eye through which light can pass.
101
What are the liquids of the eye called?
The aqueous humour and the vitreous humour
102
What is the aqueous humour?
The fluid between the cornea and iris
103
What is the vitreous humour?
The fluid in the main interior of the eye i,e, where the retina is.
104
What is the fluid between the cornea and iris called?
Aqueous humour
105
What is the fluid in the main cavity of the eyeball called?
The vitreous humour
106
What is the structure which adjusts the size of the lens called?
The suspensory ligament
107
What is the layer of tissue with blood vessels to supply the retina called?
The choroid
108
What is glaucoma?
A disease in which the ducts which drain the aqueous humour are clogged causing fluid to accumulate.
This puts pressure on the optic nerve, possibly causing blindness.
109
How does aqueous humour differ from vitreous humour in terms of physical properties?
Aqueous humour has a consistency of water whereas vitreous humour is jellylike.
110
What causes the blind spot in humans?
The optic nerve is covered by the optic disk, which lacks photoreceptors.
111
What is the structure of the retina?
The outermost layer is a single-cell thick layer of pigmented epithelium. Photoreceptors i..e rods and cones extend into this layer.
‘bipolar cells’ are neurons that gather input from multiple photoreceptors. Multiple bipolar cells attach to ganglion cells which relay their information to optic nerve fibres.
Horizontal cells integrate information from multiple photoreceptors and convey this to bipolar cells. Amacrine cells integrate information form multiple horizontal cells and sends this to the ganglion cells.
Note that most photoreceptors/bipolar cells link directly to horizontal/ganglion cells whereas in other this information is integrated first by horizontal/amacrine cells.
112
What are the main cells involved in the conduction of signals from the photoreceptors to the optic nerves?
Horizontal cells, bipolar cells, amacrine cells and ganglion cells.
113
What are ‘omatidia’?
The individual photoreceptor units of a compound eye.
114
What is the the structure of a human eye?
It has the basic shape of a ball. The front edge of the ball is made up of transparent ‘cornea’ while the rest of the eye ball is surround by white ’sclera.’ Interior to the sclera is a thin layer of chorioid which contains many blood vessels to feed the retina which is interior to it.
Behind the cornea is the iris, with aqueous humour between these structures. Light passes through the pupil, a hole in the iris, and passes through the ‘lens’. The shape of the lens is adjusted by the ’suspensory ligament.’
The light passing through the lens reaches the interior of the eyeball, which is filled with vitreous humour. This light is focused onto the retina, a sheet of cells that covers most of the eyeball.
At the far back of the retina is the ‘optic disk’, a blindspot which has not photoreceptors. Behind this is the optic nerve and the ‘central artery’ and ‘central vein’ which provided blood flow to the eye.
115
What is the white exterior of the eye called?
Sclera
116
What is internal to the sclera?
The ‘choroid'
117
What is ’sclera’?
The opaque white exterior of the eye
118
What is ‘choroid’?
The layer of the eye ball between the sclera and the retina. It has many blood vessels to supply the retina.
119
What is the ‘fovea’?
A concentration of cones on the retina meaning this area has particularly acute visual detail i.e. not-peripheral
120
What is region of the retina with many photoreceptors called?
The fovea.
121
What is the outermost layer of the eye through which light can pass?
The cornea.
122
What is the cornea?
The front transparent bit of the eye through which light can pass.
123
What are the liquids of the eye called?
The aqueous humour and the vitreous humour
124
What is the aqueous humour?
The fluid between the cornea and iris
125
What is the vitreous humour?
The fluid in the main interior of the eye i,e, where the retina is.
126
What is the fluid between the cornea and iris called?
Aqueous humour
127
What is the fluid in the main cavity of the eyeball called?
The vitreous humour
128
What is the structure which adjusts the size of the lens called?
The suspensory ligament
129
What is the layer of tissue with blood vessels to supply the retina called?
The choroid
130
What is glaucoma?
A disease in which the ducts which drain the aqueous humour are clogged causing fluid to accumulate.
This puts pressure on the optic nerve, possibly causing blindness.
131
How does aqueous humour differ from vitreous humour in terms of physical properties?
Aqueous humour has a consistency of water whereas vitreous humour is jellylike.
132
What causes the blind spot in humans?
The optic nerve is covered by the optic disk, which lacks photoreceptors.
133
What is the structure of the retina?
The outermost layer is a single-cell thick layer of pigmented epithelium. Photoreceptors i..e rods and cones extend into this layer.
‘bipolar cells’ are neurons that gather input from multiple photoreceptors. Multiple bipolar cells attach to ganglion cells which relay their information to optic nerve fibres.
Horizontal cells integrate information from multiple photoreceptors and convey this to bipolar cells. Amacrine cells integrate information form multiple horizontal cells and sends this to the ganglion cells.
Note that most photoreceptors/bipolar cells link directly to horizontal/ganglion cells whereas in other this information is integrated first by horizontal/amacrine cells.
134
What are the main cells involved in the conduction of signals from the photoreceptors to the optic nerves?
Horizontal cells, bipolar cells, amacrine cells and ganglion cells.
135
What is the structure of a photoreceptor?
It has a synaptic terminal and cell body.
At the other end is a stack of membranous 'disks' in which visual pigments are embedded. These disks are surrounded by an ‘outer segment’ membrane. In ‘cones’ the disks and outer segment is conical, in rod it is cylindrical.
136
What is the structure of a visual pigment in a human eye’s photoreceptor?
Vertebrate visual pigments consist of a light-absorbing molecule called retinal (a derivative of vitamin A) bound to a membrane protein called an opsin. Seven α helices of each opsin molecule span the disk membrane.
137
How do the visual pigments in a rod work?
The opsin bound to the retinal is called ‘rhodopsisn'
In the absence of light the retinal is in its ‘cis isomer’, existing as a bent chain. The presence of light stimulates its conversion into its ’trans isomer’ form which is a strait chain.
In the absence of light enzymes convert the trans isomer into the cis isomer. Therefore by measuring the ratio of retinal in its ’trans isomer’ to ‘cis isomer’ the light level can be deduced.
138
What is retinal?
The general term for a light-absorbing molecule in the vertebrate eye.
139
What from does retinal enter when exposed to light?
It enters its ’trans isomer’ phase which consists of a straight line.
140
What is ‘rhodopsin’?
The molecule bound to the light-absorbing retinal pigment in rods.
141
What are the basic stages in the generation of a receptor potential in a rod cell?
Light converts cis-retinal to trans-retinal, activating rhodopsin.
Active rhodopsin activates a G protein called 'transducer'.
Transducin activates the enzyme phosphodiesterase which detaches cGMP from Na+ channels in the plasma membrane by hydrolysing cGMP to GMP.
The Na+ channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes (becomes more negative), generating a membrane potential.
142
What is ’transducin’?
The G protein activated by rhodopsin in the rods of a vertebrate eye.
143
What is the basic difference between rods and cones?
Rods detect light/dark, cones detect colour.
144
How are signals relayed from the photoreceptors?
When exposed to light the activation of rhodopsin causes Na+ channels to close and thus the rod becomes hyper polarises.
This negative voltage inhibits the release of glutamate into the synapse. This depolarises or hyperpolarises the post-synaptic bipolar cell, depending on it glutamate receptors.
145
Why are horizontal cells important?
When an illuminated rod or cone stimulates a horizontal cell, the horizontal cell inhibits more distant photorecep- tors and bipolar cells that are not illuminated.
The result is that the region receiving light appears lighter and the dark surroundings even darker. This form of integration is called 'lateral inhibition’ and improves the sharpness and contrast of the image.
146
What does ‘receptive field’ refer to?
Is the region of photoreceptors which link to a single ganglion.
Therefore in the peripheral vision areas each ganglion has a large receptive field, whereas in the fovea it is smaller and thus a finer image is formed.
147
What is the area from which a ganglion revives visual input from photoreceptors called?
Its ‘receptive field'
148
What is ‘lateral inhibition’?
The idea that when activated horizontal cells inhibit photoreceptors far from the activated photoreceptor to increase the image’s contrast
149
What is the area of the eye with the greatest concentration of retinal ganglion cells called?
The fovea
150
What is the fovea?
The area of the retina which the highest concentration of photoreceptors/ganglion cells.
151
What is the path visual information takes from the eyes to the correct part of the brain?
Information form both eyes travels vis the optic nerve to single optic chiasm at the front of the brain. Information from the right visual field (includes some from both eyes) is relayed to the left side of the brain and vice versa.
Once sent to eh correct side of the brain visual information reaches the right or left ‘lateral geniculate nucleus’ which is near the centre of the brain.
From the lateral geniculate nuclei the visual information is relayed to the primary visual cortex at the back of the brain.
152
What is the ‘optic chasm’?
The place where visual information from both eyes converges so that it can be sorted into visual fields
153
What is the ‘lateral geniculate nucleus’?
The region in the middle of the brain where signals of the opposite side’s visual field is relayed onto the primary visual cortex.
154
What organism have colour vision?
Most fish, amphibians and reptiles + bird.
Very few mammals have colour vision, excluding primates like humans.
155
How does colour vision work in humans?
There are three types of cones with three different pigments (R, G or B)
These different visual pigments are called photopsins and are due to the binding of retinal with 3 slightly different opsin molecules, which are sufficiently different to give the photoreceptor the correct wavelength.
The action spectra of the various cones overlap. This means that the brain can perceive colours other than R, G or B based on the proportion of Red cones to Green cones activated etc.
156
Why do many mammals lack colour vision?
A fair few are nocturnal, such as cats, and thus evolved to have high concentrations of rods
157
At approximately what angle can humans see, including peripheral vision?
Almost 180º
158
What is the fovea?
An area on the retina with a high concentration of cones and almost no rods.
159
How is the eye focused?
To focus on near objects ‘ciliary muscles’ contract, forcing the chord towards the lens. This relaxes the ’suspensory ligaments’ causing the lens to become more spherical.
To focus on distant objects the ciliary muscles relax which pulls the choroid away from the lens. This is carried by the suspensory ligaments which pull the lens into a more flat shape.
160
What is the sense of taste formally known as?
Gustation
161
What is the sense of smell formally known as?
Olfaction
162
What does olfaction refer to?
The sense of smell
163
What does gustation refer to?
The sense of taste
164
What is a tastant?
A chemical that leads to a taste
165
What is an odorant?
A chemical that can be detected as a smell
166
What is a chemical that acts as a smell called?
An odorant
167
What is a chemical that acts as a taste called?
A tastant.
168
How do insects taste/smell things?
They have ‘olfactory hairs’ which contain chemoreceptors to detect airborne odourants
169
How do insect repellants work?
They block the olfactory receptors in mosquitos.
170
What are the basic animal taste types?
Sweet, Sour, Salty, Bitter and Umami
171
How localised is taste?
Contrary to popular belief it does not have specify regions so all areas of the tongue can taste each basic taste.
However each taste bud consists of multiple receptor cell, with each begin specialised to a particular taste i.e. sweet, sour.
172
What is the structure of a the tongue and its taste buds?
It has many raised bumps called papillae which increase its surface area.
Across its surface area are many taste buds, with each begin essentially a pit.
Food particles enter this “pit” through a hole called a ’taste pore.’ They then enter the centred of the taste bud which is lined with multiple sensory receptors, with each begin tuner for sweet, or sour etc.
173
True or false: there are multiple types of ’sweet’ receptors etc.
True, there are multiple types of receptors for sweet etc, with each responding to a particular chemical i.e. one for glucose, one for sucrose
174
How can multiple ligands all lead to the perception of taste?
There are multiple receptors per basic taste i.e. sweet.
One type binds to glucose, one to sucrose and so on. (note that most taste receptors actually bind to multiple tastants)
175
What does GPCR refer to?
A ‘G protein coupled receptor‘
176
What does ’TRP' stand for?
'Transient receptor potential’
177
What is a ’TRP’/ Transient receptor potential protein?
A receptor which when activated leads to a cellular response by triggering a change in an ion channel leading to depolarisation and thus activation of the sensory neuron.
178
How can taste receptors be divided chemically?
Sweet, umami and bitter taste receptors are GPCR (G protein coupled receptors)
The receptors sour tastants are TRP proteins in which activation of the receptor causes an ion channel to open or close. This leads to depolarisation and thus activation of a sensory neuron.
179
What are receptors which detect smells called?
Odorant receptors (OR)
180
What does ’OR’ refer to?
Odorant receptor
181
What class of receptors are odorant receptors?
They are all GPCRs (G-protein coupled receptors)
182
Who does the binding of an odorant to an OR trigger the sensory neuron?
The binding of the odorant to the OR triggers the production of cyclic AMP which opens channels in the plasma membrane that are permeable to both Na+ and Ca2+. The flow of these ions into the receptor cell leads to depolarization of the membrane, generating action potentials.
183
What is the pathway from odorant to signals to the brain?
In the nose is a layer of mucus enclosed with epithelium.
Chemoreceptors are located in this epithelium and have cilia that extend into the mucus and bind to odorants.
This triggers action potentials down the sensory neutrons which pass through the skull into the ‘olfactory bulb’ of the brain.
The olfactory bulb integrates signals and relays them to the rest of the brain.
184
What is the olfactory bulb?
A region of the brain which integrates olfactory information sent by the chemoreceptors of the nose.
185
What is the sense of taste formally known as?
Gustation
186
What is the sense of smell formally known as?
Olfaction
187
What does olfaction refer to?
The sense of smell
188
What does gustation refer to?
The sense of taste
189
What is a tastant?
A chemical that leads to a taste
190
What is an odorant?
A chemical that can be detected as a smell
191
What is a chemical that acts as a smell called?
An odorant
192
What is a chemical that acts as a taste called?
A tastant.
193
How do insects taste/smell things?
They have ‘olfactory hairs’ which contain chemoreceptors to detect airborne odourants
194
How do insect repellants work?
They block the olfactory receptors in mosquitos.
195
What are the basic animal taste types?
Sweet, Sour, Salty, Bitter and Umami
196
How localised is taste?
Contrary to popular belief it does not have specify regions so all areas of the tongue can taste each basic taste.
However each taste bud consists of multiple receptor cell, with each begin specialised to a particular taste i.e. sweet, sour.
197
What is the structure of a the tongue and its taste buds?
It has many raised bumps called papillae which increase its surface area.
Across its surface area are many taste buds, with each begin essentially a pit.
Food particles enter this “pit” through a hole called a ’taste pore.’ They then enter the centred of the taste bud which is lined with multiple sensory receptors, with each begin tuner for sweet, or sour etc.
198
True or false: there are multiple types of ’sweet’ receptors etc.
True, there are multiple types of receptors for sweet etc, with each responding to a particular chemical i.e. one for glucose, one for sucrose
199
How can multiple ligands all lead to the perception of taste?
There are multiple receptors per basic taste i.e. sweet.
One type binds to glucose, one to sucrose and so on. (note that most taste receptors actually bind to multiple tastants)
200
What does GPCR refer to?
A ‘G protein coupled receptor‘
201
What does ’TRP' stand for?
'Transient receptor potential’
202
What is a ’TRP’/ Transient receptor potential protein?
A receptor which when activated leads to a cellular response by triggering a change in an ion channel leading to depolarisation and thus activation of the sensory neuron.
203
How can taste receptors be divided chemically?
Sweet, umami and bitter taste receptors are GPCR (G protein coupled receptors)
The receptors sour tastants are TRP proteins in which activation of the receptor causes an ion channel to open or close. This leads to depolarisation and thus activation of a sensory neuron.
204
What are receptors which detect smells called?
Odorant receptors (OR)
205
What does ’OR’ refer to?
Odorant receptor
206
What class of receptors are odorant receptors?
They are all GPCRs (G-protein coupled receptors)
207
Who does the binding of an odorant to an OR trigger the sensory neuron?
The binding of the odorant to the OR triggers the production of cyclic AMP which opens channels in the plasma membrane that are permeable to both Na+ and Ca2+. The flow of these ions into the receptor cell leads to depolarization of the membrane, generating action potentials.
208
What is the pathway from odorant to signals to the brain?
In the nose is a layer of mucus enclosed with epithelium.
Chemoreceptors are located in this epithelium and have cilia that extend into the mucus and bind to odorants.
This triggers action potentials down the sensory neutrons which pass through the skull into the ‘olfactory bulb’ of the brain.
The olfactory bulb integrates signals and relays them to the rest of the brain.
209
What is the olfactory bulb?
A region of the brain which integrates olfactory information sent by the chemoreceptors of the nose.
210
What type of receptors are Odorant Receptors?
GPCR chemoreceptors
211
What is the basic structure of a muscle?
It is composed of many myofibrils (muscle fibres) of which each is an elongated cell with multiple nuclei.
With in each myofibril are thick filaments and thin filament arranged in sarcomeres
212
What are muscle fibres also known an?
Myofibrils
213
What are myofibrils?
Muscle fibres i.e. elongated cell with multiple nuclei
214
What is the contractile unit of a muscle?
Its sarcomeres
215
What are sarcomeres?
The contractile unit of muscles
216
What is the structure of a sarcomere?
It has short segments of Thick filaments (myosin) which are connected by Thin filaments (actin)
The gap between the thick filaments is bridged by thin filaments (actin) which are joined by an M line. The multiple parallel thick filaments are joined vertically by the Z line.
217
What is skeletal muscle also known as and why?
Striated muscle.
This is because the parallel muscle fibres (myofibrils) give it a stripy appearance.
218
What are the Thick filaments of a muscle composed of?
Myosin
219
What are the thin filaments of a muscle composed of?
Actin
220
What type of muscle filament does actin form?
Thin filament
221
What type of muscle filament does myosin form?
Thick filament.
222
What does the Z line refer to?
The structure that joins parallels thin filaments
223
What does the M line refer to?
The structure that joins parallel thick filaments (M for Myosin)
224
What is the structure that joins Thick filaments called?
The M line
225
What is the structure that joins thin filaments?
The Z line
226
What model explains how muscles contract?
The “Sliding-Filament model"
227
What is the basic idea behind the ’sliding-filament model'
The actual lengths of the thin and thick filaments do not change. Instead during contraction they become more overlapped.
228
What is the structure of a myosin?
It has a long “tail” region and a globular “head"
229
What are the chemical steps in skeletal muscle contraction?
The myosin head begins bound to ATP and is in its low-energy configuration and not bound to the myosin.
The myosin head hydrolyzes
ATP to ADP and inorganic phosphate (Pi) and is in its high-energy configuration where it is raised up and perpendicular to the rest of the filament.
The myosin head binds to actin, forming a cross-bridge.
Releasing ADP and P i, myosin
returns to its low-energy configuration, sliding the thin filament.
Binding of a new molecule of ATP releases the myosin head from actin, and a new cycle begins.
230
What role does each filament play in the sarcomere?
The 'thick filament' (myosin) has heads which act to move the passive ‘thin filaments’ (actin)
231
How is the ATP needed for muscle contraction provide to the thick filaments?
Transfer of a phosphate group from creatine phosphate to ADP synthesises ATP.
ATP stores are also replenished when glycogen is broken down to glucose, which can be used to generate ATP through aerobic respiration or fermentation.
232
What is the basic concept by which the contraction of muscles is regulated?
Actin can be modelled as a small globular protein with a binding site for myosin.
Normally the chain of individual actin proteins is surrounded by a long chain ’tropomyosin.’ This blocks the myosin binding sites on the actin and thus muscle contraction can not occur.
Along the length of the tropomyosin is multiple ’troponin complexes’. When bound to Ca2+ they shift the tropomyosin so that the myosin binding sites are exposed. Therefore muscular contraction occurs.
233
What does ’tropomyosin’ refer to?
The protein which wraps around the actin so it can’t bind to myosin.
234
What does ’troponin complex’ refer to?
The receptors along the tropomyosin which when bound to Ca2+ shift the tropomyosin so that the myosin binding sites are exposed and thus muscular contraction can occur.
235
How is muscular contraction regulated from a motor neuron’s action potential?
Acetylcholine (ACh) released at synaptic terminal of the motor neuron diffuses across synaptic cleft and binds to receptor proteins on muscle fiber‘s plasma membrane, triggering an action potential in the muscle fibre.
Action potential is propagated along plasma membrane and down T tubules.
Action potential triggers Ca2+ release from sarcoplasmic reticulum (SR) of the muscle cell.
Calcium ions bind to troponin in thin filament; myosin-binding sites exposed and muscular contraction occurs.
236
How is muscular contraction ended once the action potential ends?
Cytosolic Ca2+ is removed by active transport into SR after action potential ends.
Tropomyosin blockage of myosin-binding sites is restored; contraction ends, and muscle fiber relaxes.
237
What type of receptors are Odorant Receptors?
GPCR chemoreceptors
238
What is the basic structure of a muscle?
It is composed of many myofibrils (muscle fibres) of which each is an elongated cell with multiple nuclei.
With in each myofibril are thick filaments and thin filament arranged in sarcomeres
239
What are muscle fibres also known an?
Myofibrils
240
What are myofibrils?
Muscle fibres i.e. elongated cell with multiple nuclei
241
What is the contractile unit of a muscle?
Its sarcomeres
242
What are sarcomeres?
The contractile unit of muscles
243
What is the structure of a sarcomere?
It has short segments of Thick filaments (myosin) which are connected by Thin filaments (actin)
The gap between the thick filaments is bridged by thin filaments (actin) which are joined by an M line. The multiple parallel thick filaments are joined vertically by the Z line.
244
What is skeletal muscle also known as and why?
Striated muscle.
This is because the parallel muscle fibres (myofibrils) give it a stripy appearance.
245
What are the Thick filaments of a muscle composed of?
Myosin
246
What are the thin filaments of a muscle composed of?
Actin
247
What is Myasthenia gravis?
An autoimmune disease in which a person produces antibodies to the acetylcholine receptors on skeletal muscle fibers.
As the number of these receptors decreases, synaptic transmission between motor neurons and muscle fibers declines.
248
What type of muscle filament does myosin form?
Thick filament.
249
What does the Z line refer to?
The structure that joins parallels thin filaments
250
What does the M line refer to?
The structure that joins parallel thick filaments (M for Myosin)
251
What is the structure that joins Thick filaments called?
The M line
252
What is the structure that joins thin filaments?
The Z line
253
What causes muscle fatigue?
- Depletion of ATP
- Dissipation of Ca2+ ion gradients
- Accumulation of lactate
254
How can muscle fatigue be minimised?
Fatigue occurs when the sarcomeres become contracted for a long time.
To mitigate this if only half the sarcomeres are contracted the nervous system can alternate which are contracted.
Also with the presence of myoglobin, a protein which stores oxygen and thus prevents anaerobic respiration.
255
What is the structure of a myosin?
It has a long “tail” region and a globular “head"
256
What are the chemical steps in skeletal muscle contraction?
The myosin head begins bound to ATP and is in its low-energy configuration and not bound to the myosin.
The myosin head hydrolyzes
ATP to ADP and inorganic phosphate (Pi) and is in its high-energy configuration where it is raised up and perpendicular to the rest of the filament.
The myosin head binds to actin, forming a cross-bridge.
Releasing ADP and P i, myosin
returns to its low-energy configuration, sliding the thin filament.
Binding of a new molecule of ATP releases the myosin head from actin, and a new cycle begins.
257
What role does each filament play in the sarcomere?
The 'thick filament' (myosin) has heads which act to move the passive ‘thin filaments’ (actin)
258
How is the ATP needed for muscle contraction provide to the thick filaments?
Transfer of a phosphate group from creatine phosphate to ADP synthesises ATP.
ATP stores are also replenished when glycogen is broken down to glucose, which can be used to generate ATP through aerobic respiration or fermentation.
259
What is the basic concept by which the contraction of muscles is regulated?
Actin can be modelled as a small globular protein with a binding site for myosin.
Normally the chain of individual actin proteins is surrounded by a long chain ’tropomyosin.’ This blocks the myosin binding sites on the actin and thus muscle contraction can not occur.
Along the length of the tropomyosin is multiple ’troponin complexes’. When bound to Ca2+ they shift the tropomyosin so that the myosin binding sites are exposed. Therefore muscular contraction occurs.
260
What does ’tropomyosin’ refer to?
The protein which wraps around the actin so it can’t bind to myosin.
261
What does ’troponin complex’ refer to?
The receptors along the tropomyosin which when bound to Ca2+ shift the tropomyosin so that the myosin binding sites are exposed and thus muscular contraction can occur.
262
How is muscular contraction regulated from a motor neuron’s action potential?
Acetylcholine (ACh) released at synaptic terminal of the motor neuron diffuses across synaptic cleft and binds to receptor proteins on muscle fiber‘s plasma membrane, triggering an action potential in the muscle fibre.
Action potential is propagated along plasma membrane and down T tubules.
Action potential triggers Ca2+ release from sarcoplasmic reticulum (SR) of the muscle cell.
Calcium ions bind to troponin in thin filament; myosin-binding sites exposed and muscular contraction occurs.
263
How is muscular contraction ended once the action potential ends?
Cytosolic Ca2+ is removed by active transport into SR after action potential ends.
Tropomyosin blockage of myosin-binding sites is restored; contraction ends, and muscle fiber relaxes.
264
How are signals from the motor neuron carries to the rest of the muscle?
Along traverse (T) tubules
265
What are transverse (T) tubules?
In-foldings of the plasma membrane of the muscle cells which carry electrical signals from the motor neuron to the SR
266
What are T tubules also known as?
Transverse tubules
267
How can the ability of a muscle to withstand fatigue be improved with exercise?
If a muscle is used repeatedly some fast glycolytic fibers can develop into fast oxidative fibers.
Because fast oxidative fibers fatigue more slowly than fast glycolytic fibers this forms a muscle that is more resistant to fatigue.
268
Where do the Ca2+ ions needed for muscle contraction originate?
The SR (sarcoplasmic reticulum)
269
What does ’SR’ refer to?
The sarcoplasmic reticulum.
270
What are the major muscular diseases?
ALS and Myasthenia gravis
271
What is ALS?
Amylotrophic lateral sclerosis in which motor neurons in the spinal cord and brainstem degenerate, and the muscle fibers with which they synapse atrophy.
272
What is ALS also called?
Lou Gehrig’s disease
273
What is Lou Gehrig’s disease also known as?
ALS
274
What is Myasthenia gravis?
An autoimmune disease in which a person produces antibodies to the acetylcholine receptors on skeletal muscle fibers.
As the number of these receptors decreases, synaptic transmission between motor neurons and muscle fibers declines.
275
How are signals from the motor neuron carries to the rest of the muscle?
Along traverse (T) tubules
276
What are transverse (T) tubules?
In-foldings of the plasma membrane of the muscle cells which carry electrical signals from the motor neuron to the SR
277
What are T tubules also known as?
Transverse tubules
278
What is the sarcoplasmic reticulum?
A specialised form of an ER (endoplasmic reticulum) which stores the Ca2+ needed for muscle contraction.
279
Where do the Ca2+ ions needed for muscle contraction originate?
The SR (sarcoplasmic reticulum)
280
What does ’SR’ refer to?
The sarcoplasmic reticulum.
281
What are the major muscular diseases?
ALS and Myasthenia gravis
282
What is ALS?
Amylotrophic lateral sclerosis in which motor neurons in the spinal cord and brainstem degenerate, and the muscle fibers with which they synapse atrophy.
283
What is ALS also called?
Lou Gehrig’s disease
284
What is Lou Gehrig’s disease also known as?
ALS
285
What is Myasthenia gravis?
An autoimmune disease in which a person produces antibodies to the acetylcholine receptors on skeletal muscle fibers.
As the number of these receptors decreases, synaptic transmission between motor neurons and muscle fibers declines.
286
What is the basic idea behind the nervous control of muscle?
Each motor neuron connects to one or more muscle fibres.
This motor neuron and the muscle fibres controls is collectively called a ‘motor unit'
287
What is a motor neuron and the muscle fibres it controls called?
A motor unit.
288
What does ’motor unit’ refer to?
A motor neuron and the muscle fibres it controls called
289
How can the force that a muscle exerts be attenuated?
The nervous system can increase the force of a muscle by increasing the number of motor units and thus muscle fibres which it activates.
The activation of progressively more muscle fibres is called ‘recruitment'
290
What does ’recruitment’ refer to in the context of muscles?
'The nervous system can increase the force of a muscle by increasing the number of motor units and thus muscle fibres which it activates.
The activation of progressively more muscle fibres is called ‘recruitment'
291
What causes muscle fatigue?
- Depletion of ATP
- Dissipation of Ca2+ ion gradients
- Accumulation of lactate
292
What is the basic idea behind the nervous control of muscle?
Each motor neuron connects to one or more muscle fibres.
This motor neuron and the muscle fibres controls is collectively called a ‘motor unit'
293
What is a motor neuron and the muscle fibres it controls called?
A motor unit.
294
What does ’motor unit’ refer to?
A motor neuron and the muscle fibres it controls called
295
How can the force that a muscle exerts be attenuated?
The nervous system can increase the force of a muscle by increasing the number of motor units and thus muscle fibres which it activates.
The activation of progressively more muscle fibres is called ‘recruitment'
296
What does ’recruitment’ refer to in the context of muscles?
'The nervous system can increase the force of a muscle by increasing the number of motor units and thus muscle fibres which it activates.
The activation of progressively more muscle fibres is called ‘recruitment'
297
What causes muscle fatigue?
- Depletion of ATP
- Dissipation of Ca2+ ion gradients
- Accumulation of lactate
298
How can muscle fatigue be minimised?
Fatigue occurs when the sarcomeres become contracted for a long time.
To mitigate this if only half the sarcomeres are contracted the nervous system can alternate which are contracted.
299
How are smooth contractions of skeletal muscles achieved?
Each action potential causes a brief jerky contraction and thus was could non-smooth motion.
To mitigate this multiple action potentials are sent in a short space of time. If the second action potential arrives before the muscle has relaxed from the first these two impulses are ’temporally summed’.
The smooth movement this results in is called Tetanus.
300
What is the smooth movement of muscles called?
Tetanus
301
What does ’tetanus’ refer to? (not the disease)
The smooth contraction of muscles through temporal summation.
302
How are muscles connected to bone?
With ’tendons'
303
What are ‘tendons'?
Structures that connect muscles to bones.
304
How can skeletal muscle fibres be classed?
Whether they are Oxidative or Glycolytic.
Or by whether they are Fast-Twitch or Slow-Twitch.
305
What are oxidative muscle fibres?
Fibres which derive much of their energy through aerobic respiration. Therefore they have have many mitochondria, a rich blood supply, and a large amount of an oxygen-storing protein called myoglobin
306
What are glycolytic muscle fibres?
Muscle fibres that use glycolysis as their primary source of ATP. They have a larger diameter and less myoglobin than oxidative fibers and thus fatigue much more readily.
307
How can oxidative and glycolytic muscle fibres be distinguished visually?
Oxidative fibres appear redder do to the presence of myoglobin.
308
What is myoglobin?
brownish red pigment which binds tightly to oxygen enabling oxidative fibers to extract and store oxygen from the blood efficiently.
309
How do fast-twitch and slow-twitch fibres differ?
Fast fibers enable brief, rapid, powerful contractions. Slow fibers, often found in muscles that maintain posture, can sustain long contractions.
A slow fiber has less sarcoplasmic reticulum and pumps Ca2+ more slowly than a fast fiber. Because Ca2+ remains in the cytosol longer, a muscle twitch in a slow fiber lasts less time.
The difference in contraction speed between slow-twitch and fast-twitch fibers reflects the rate at which their myosin heads hydrolyze ATP.
All slow-twitch fibers are oxidative, fast-twitch fibers can be either glycolytic or oxidative.
310
Where are fast-twitch and slow-twitch muscle fibres found in the body?
Most human skeletal muscles contain both fast and slow- twitch fibers, although the muscles of the eye and hand are exclusively fast-twitch.
311
How can the ability of a muscle to withstand fatigue be improved with exercise?
If a muscle is used repeatedly some fast glycolytic fibers can develop into fast oxidative fibers.
Because fast oxidative fibers fatigue more slowly than fast glycolytic fibers this forms a muscle that is more resistant to fatigue.
312
True or false: muscles can contract more frequently than action potentials arrive?
True.
This is seen in the flight muscles of some insects and is due to the fact that individuals motor neutrons are triggered by action potentials at different times.
313
What is cardiac muscle and how does it differ from skeletal muscle?
The muscle found in heart tissue.
Cardiac muscle cells have ion channels in their plasma membrane that cause rhythmic depolarizations, triggering action potentials without input from the nervous system.
‘Intercalated disks’ between the muscle fibres allow these action potentials to propagate
314
What are the structures that conduct action potentials in cardiac muscle?
Intercalated disks
315
How does smooth muscle differ in terms of structure?
They lack striations as their actin and myosin filaments are not regularly arrayed along the length of the cell.
Instead, the thick filaments are scattered throughout the cytoplasm, and the thin filaments are attached to structures called dense bodies, some of which are tethered to the plasma membrane.
There is less myosin than in striated muscle fibers, and the myosin is not associated with specific actin strands.
316
How does smooth muscle differ in term of how is is regulated?
Smooth muscle cells have no troponin complex or T tubules, and their sarcoplasmic reticulum is not well developed. During an action potential, Ca2+ enters the cytosol mainly through the plasma membrane.
Calcium ions cause contraction by binding to the protein calmodulin, which activates an enzyme that phosphorylates the myosin head, enabling cross-bridge activity.
317
What is ‘calmodulin’?
The protein in smooth muscle which when bound to Ca2+ activates an enzymes that phosphorylates the myosin head, leading to muscular contraction.
318
What does ‘patella’ refer to?
The bone that acts as the ‘knee cap'
318
What does ‘metatarsals’ refer to?
The bones of the actual fleshy foot.
318
What are the basic types of skeletons?
Hydrostatic, exoskeletons and endoskeletons
318
What is the technical term to describe the fact that muscles act in pairs?
They are ‘antagonistic'
318
What does ’antagonistic’ refer to in the context of muscles?
The fact that they act in pairs to oppose each other.
318
Based on the fact that they are antagonistic, how are muscles labelled?
The ‘extensor’ muscle extends the limb etc. whereas the ‘flexor’ muscle decreases the angle of the limb.
318
What does ’extensor muscle’ refer to?
A muscle that acts to extend the limb
318
What does ‘flexor muscle’ refer to?
A muscle that acts to decrease the angle of the limb i.e. bring the arm close to the body.
318
What is the structure of the hand in terms of bones?
It consists of carpals, phalanges and metacarpals.
Carpals are bones that form the wrists. They branch of into 5 metacarpals which form the webbed hand and terminate in phalanges which are the fingers.
318
What is the structure of the shoulder in terms of bones?
The shoulder bones are collectively called the ’shoulder girdle.’
This consists of a ’scapula’ which contains a ball & socket joint and a ‘clavicle' located above to provide support.
318
In terms of bones, what is the shoulder called?
The ’shoulder girdle'
318
What does ’carpal’ refer to?
One of the bones in the wrist
318
What does ‘metacarpals’ refer to?
One of the 5 bones that make up the webbed bit of the hand
318
What does ‘phalanges’ refer to?
The bones that make up the actual fingers or toes.
318
What are the bones that make up the wrist called?
Carpals
318
What are the bones that make up the actual hand called?
Metacarpals
318
What are the bones that make up the fingers called?
Phalanges
318
What is the structure of the arm in terms of bones?
The top of the arm is composed of a ‘humerus’ which runs from the scapula (shoulder) to the elbow.
The elbow is connected to the hand by a ‘radius' and an ulna. The 'radius' is larger and runs to the outer edge of the hand.
318
What is/are the bone(s) that make(s) up the upper arm called?
The humerus
318
What is/are the bone(s) that make(s) up the lower arm called?
The radius and the ulna
318
What does ’humerus’ refer to?
The bones which makes up the upper arm i.e. shoulder to elbow
318
What does ‘radius’ refer to?
The larger of the two bones that make up the lower arm
318
What does ‘ulna’ refer to?
The narrower of the two bones that make up the lower arm.
318
What is the structure of a leg?
The upper leg consists of a single large femur which terminates in a knee. The knee is protected by a “knee cap” called the ‘patella.’
From the knee a large ’tibia’ extends down to the foot. A smaller ‘fibula’ follows the same path for support
318
What does ‘femur’ refer to?
The large leg bone which extends form the hip to the knee
318
What is the bones that extends from the hip to the knee called?
The femur
318
What is the bones that protects the knee called?
The ‘patella'
318
What is the main bone of the lower leg?
The tibia
318
What is the supporting bone of the leg?
The fibula.
318
What does ’femur’ refer to?
The large leg born which extends from the hips to the foot.
318
What does ’tibia’?
The large main bone of the lower leg
318
What does ‘fibula’ refer to?
The thinner of the two bones in the lower leg. It functions as additional support.
318
What is the structure of the foot in terms of bones?
The ankle is composed of the tarsals, the metatarsals make up the actual foot and the phalanges form the toes
318
What does ’tarsals’ refer to?
The bones of the ankle
318
What are the bones of the ankle called?
The tarsals
318
What are the bones of the fleshy foot called?
The metatarsals
318
What are the the bones of the toes called?
Phalanges
318
What are hydrostatic skeletons?
"Skeletons" in which fluid held under pressure is used in motion.
318
How can motion be achieved with hydrostatic skeletons?
Hydras close their mouth and use contractile cells to decrease the diameter of its gastrovascular cavity. Since water is incompressible this elongates its body.
Worms move by ‘peristalsis’ (explained in another card)
318
What is the process by which worms move sign their hydrostatic skeleton called?
Peristalsis
318
How do worms move using peristalsis?
Their body contains many fluid filled cavities separated by ’septa.’ Along the length of their bodies are many movable ‘bristles.’ Each fluid filled cavity has circular muscles that wrap around it and longitudinal muscles which can shorten or extend the section.
Using bristles it anchors its tail end to the ground. It then contracts the circular muscles and relaxes (extends) the longitudinal muscles in the mid section so that the head moves forward. It then anchors the head in place with the bristles so that the tail end can be released and shorten by similar methods.
This happens in a wave, hence the term ‘peristalsis'
318
In what organisms are hydrostatic skeletons often found?
Cnidarians, flatworms, nematodes, and annelids
318
What is the structure of exoskeletons in molluscs?
It is composed of calcium carbonate/
319
What is the exoskeleton of insects called?
Its ‘cuticle'
320
What does ‘cuticle’ refer to in terms of animals?
The exoskeleton of an insect.
321
What is the structure of an insect ‘cuticle’?
It has fibrils of chitin embedded in a protein matrix.
The cuticle may be hardened with organic compounds that cross-link the proteins of the matrix, and in crustaceans such as lobsters, calcium salts may also be added.
322
What are the shells of molluscs called?
Mantles
323
What are ‘mantles’ in the context of animals?
The shells of molluscs
324
What are ‘mantles’ composed of?
Calcium carbonate.
325
What are the basic types of skeletal joint?
Ball-and-socket, ‘hinge joint’ and ‘pivot joint'
326
What is a hinge joint?
Those that restrict motion to a single plane i.e. elbow.
| like the hinge of a door
327
What is a ‘pivot joint’?
A joint which allows rotation in on axis. For example pivot joints connect the ulna and radius to the humerus at the elbow.
(like the axle of a car, with the bone being the wheel.)
328
Define locomotion.
Active travel from place to place
329
What is perilymph?
The fluid of the cochlea and semicircular canals
