Midterm 2 Flashcards
(157 cards)
1
Q
What is emmetropia?
A
Normal resting condition of lens when ciliary muscle is relaxed and lens is flat.
2
Q
Describe step 13 of NMJ:
A
ATP bound to myosin split, energizing the myosin cross bridges: M°ATP–>M°ADP°Pi.
3
Q
What are the two distinct ways by which photoreceptor interact with bipolar and ganglion cells?
A
1) On-pathway
2) Off-Pathway
4
Q
What does the bind of an odorant activate in the cilia?
A
This activate a G-protein mediated pathway that increase cAMP that in turns opens nonselective cation channels and depolarizes the cell.
5
Q
What is central and command fatigue?
A
Occurs when appropriate regions of cerebral cortex fails to send excitatory signals to motor neurons.
6
Q
What is epylepsy?
A
A common neurological disease associated with abnormally synchronized discharges of cerebral neurons.
7
Q
Describe the sclera:
A
White outer connective tissue layer that maintain and protect the internal structures and provide muscle attachment point. Dense collagenous tissue with elastic fibers and collagen fibers are large and opaque.
8
Q
What is a state of consciousness?
A
The level of alertness, refers to whether a person is awake, asleep or in coma.
9
Q
Describe utricle hair cells:
A
Point nearly straight and respond when the tip of the head is away of horizontal plane or to linear accellaration on the horizontal plane.
10
Q
What are the two factors (and relative subfactors) controlling muscle tension?
A
1) Tnesion developed by each fibers
- action potential frequency
- fiber length
- fiber diameter
- fatigue
2) Number of active fibers
- numbers of fibers per motor units
- number of motor units active
11
Q
Describe convergence in retina:
A
Retina has a large amount of convergence: many photoreceptor can synapse on the same bipolar cell and many bipolar cells can synapse on the same ganglion cells. As a result, individual ganglion cells respond differently to the various characteristics of visual images.
12
Q
Describe step 2 of NMJ:
A
Ca2+ enters the axon terminal through voltage gated Calcium channels.
13
Q
Describe pigmented retina and its role:
A
Single layer of cells filled with melanin. Pigmented epithelium and choroid absorb light that bypass the photoreceptive cells preventing refelction and scattering.
14
Q
Describe receptors of salty submodality:
A
Most sensitive type of receptor are on the tip of the tongue. It shares lowest sensitivity with sweet perceptio. Na+ inter the cells (sometimes with other metal cations) and cause a depolarization.
15
Q
What are the neuronal pathways for taste?
A
Facial Nerves (VIII) carries sensation from the anterior third of the tongue. Glossopharyngeal nerves IX and vagus nerve X carry information from posterior two thirds of the tongue. Information goes to medulla where decussation takes place.
16
Q
List the 4 ATP functions in skeletal muscle contraction:
A
1) Hydrolisis of ATP by the Na+/K+-ATPase in plasma membrane maintain Na+/K+ gradient and allow to produced and propagate action potential.
2) Hydrolisis of ATP by the Ca2+-ATPase in the sarcoplasmi reticulum provides energy for the active transport of calcium ions into the reticulum, lowering cytosolic Ca2+ to prerelease concentrations, ending the contraction.
3) Hydrolisis of ATP to myosin dissociates cross bridges providing energy for force generation.
4) Binding of ATP to myosin dissociates cross-bridges bound to actin, allowing bridges to repeat their cycle.
17
Q
What is brain death?
A
Occurs when the brain no longer functions and has no possibility to function again.
18
Q
Describe Off-Pathway:
A
It generates AP in absence of light. Bipolar cells have ionotropic glutamate receptors that are nonselective cation channles. When glutamante binds, cell depolarizes and stimulate bipolar cells to release excitatory neurotransmiters to ganglion cells stimulating fire of AP.
19
Q
What does direction and roation determines?
A
It determinse the direction in which stereocilia are betn and which hair cells are stimulated.
20
Q
What are the two proteins embedded in the sarcoplasmi reticulum?
A
- Dihydropyridine receptor: acts as a voltage sensor
- Ryanodine receptor: forms a Ca2+ channel.
21
Q
What are the three ways in which muscle fibers can generate ATP?
A
1) Phosphorylation of ADP by creatine phosphate
2) Oxidative phosphorylation of ADP in mitochondria
3) Phosphorylation of ADP by glycolitic pathways in the cytosol.
22
Q
Describe step 11 in NMJ:
A
Cross-bridges binding triggers release of ATP hydrolysis products from myosin. This produces an angular movement at each cross bridge. A°M°ADP°Pi–>A°M+ADP+Pi
23
Q
Describe step 7 of NMJ:
A
Local current depolarizes adjacent plasma membrane to threshold potential, generaating an action potential that propagates over the muscle fibers and into fibers into T-Tubules.
24
Q
Describe Vallate papillae:
A
Largest and least numerous, they have taste buds
25
Describe alpha wave:
(8-12Hz). Best recroded over parietal and occipital lobes. It is associated with decreased level of attetion.
26
What do neurons originating in the brainstem do in awake state?
They release monoaminergic neurotransmitters norepinephine, serotonin and histamine that act as a neuromodulators. Their axons terminals are distirbuted throughout the brain where they enhance excitatory synpatic activity.
27
What do horizontal and amacrine cells do?
They provide lateral integration between neurons of the retina. They are present in the inner layer and modify the signal before it leaves the retina. They enhance the borders and contours increasing intensity at border of objects.
28
What is EEG arousal?
Transformation from alpha to beta rhytmn when people are attentive or focused.
29
What does the frequency of action potential from stereocilia in hair cells in the vestibular system depends on?
- Amount of force bending
| - Direction in which this force is applied.
30
Describe movement of tectorial membrane:
As pressure waves displace the basilar membrane, the hair cells move in relation to the stationary tectorial membrane and consequently, stereocilia bend.
31
What is the final results of off and on pathways?
The net result is that the two pathways respond exactly in opposite ways in the presence of light. The activity of both increase brain's ability to contrast at edges and borders.
32
What are oxidative fibers?
Most of ATP they produce is dependent upon blood flow to deliver oxygen and oxidative metabolites to the muscle. Muscles containing many of these are used for prolonged contraction. They contain myoglobin. Contains many mitochondria.
33
Describe stereocilia in both the succule and the utricle.
They are embedded in a gelatinous substance in which tiny crystals called otoliths are embedded. Otoliths make the gelatinous substance heavier thant the surround fluid and in case of accelleration the gel material pull against the hair cells.
34
Describe opsin:
G-protein coupled receptors that change shape when struck by light and separate into opsin and retinal. In absence of light they recombine to form rhodopsin.
35
What is orexin?
Neuropeptides that maintain awake state, is produced by neurons in the hypothalamus, orexin-secreting neurons innervate and stimulate action potentials firing from monoaminergic neurons in the RAS.
36
Describe off-center receprive field:
More Action Potential frequency when light is off or when light doesn't hit the center of the field.
37
What does the amygdala do with odours?
By receiving inputs direclty from the olfactory bub the amygdala ties odours into learning, memory, visceral satisfation.
38
Describe the cochlea and the third step in the transmission of sound in hearing:
Spiral-shaped, fluid-filled space in the temporal lobe. It is almost completely divided by a membranous tube called the cochlear duct that contain sensory receptors. Next step is transmission of pressure waves to the inner ear.
39
Describe hari cells in the succule:
Hair cells projects at right angles and they respond to gravitational effect from a laying to standing position or jump.
40
Describe cones:
Light-sensitive discs of cones are formed from the infolding of the surface plasma membrane. They are considerably less sensitive than rods but they are responsible for color vision and visual acuity.
41
Describe sliding filament mechanism:
Myosin and actin filaments slide along each thers via chemical interactions. Force generation produces shortening of a skeletal myofiber and thin filaments in each sarcomere move past each others.
42
Whata re the five characteristics of a myofiber?
1) Multinucleated
2) Contains many mitochondria
3) Has special structures called transverse tubules.
4) Has myofibirls and sarcomeres.
4) It has specific terms for some of the intracellular structure.
43
What is a sarcomere?
Overlapping actin filaments and myosin proteins. Actin is anchored to the Z-lines. Myosins are fixed to a central cytoskeletal protein called M-line.
44
Describe the side of the cochlear duct near the scala tympani:
Is formed by basilar membrane upon which sits the organ of corti that contains the ear receptors cells.
45
Describe the cupula and its function:
Floats in the endolymphs and is displaced by fluid movements. Cupula displacement is most intense when rate of the head movements changes.
46
Describe step 8 in NMJ:
Action potential in T-tubules induce DHP receptors to pull open ryanodine receptors channels and this release Ca2+ from terminal cisternae of sarcoplasmi reticulum.
47
Describe the function of the sensor tympani muscle and the stapedus:
Sensory tympany muscle attaches to the malleus and contraction of the muscle dampens the bone movements, stapedus attaches to the stapes in a similar way. Amount of energy can be lessend by contraction of these two skeletal muscles.
48
Describe sound waves:
They alternate zones of compresion (pressure is increased, molcules of air are tight together) to zone of rarefaction (pressure is lower, molecules are further apart).
49
Describe On-center receptive fields:
Generate more AP when light is directed on the center of the receptive field. Response is to intense light.
50
Describe rods:
Bipolar receptor cells found in most of the retina, but not in the favea. They are for black and white vision and responds to lower levels of illumination (they are more sensitive than cones).
51
Describe ciliary muscles:
Smooth muscles that control the lens shape.
52
Describe the muscle movement:
The force generated against the mass is amplified throught the lever arm, and is a torque: t=rFsin0
53
Describe the action of neurons during sleep:
Active firing of neurons in the sleep center. These neurons release inhibitory GAB onto neurons throughouth the barinstem and hypothalamus and this inhibition reduces the levels of orexin, norepinephinre, serotonin and histamine. This promote sleep.
54
Describe step 1 of NMJ:
Action potential is initiated in the motor neurons and propagates to the motor neuron axon terminal.
55
Describe On-Pathway
Glutamate released onto bipolar cells binds to metapotrobic receptors that cause enzymatic breakdown of cGMP. This hyperpolarize the bipolar cells and this prevent them from releasing excitatory neurotransmitters on the associated ganglion cells. In absence of light, ganglion cells are not stimulated to fire AP but when light strikes, the receptor glutamate release decline, ON-bipolar cells depolarize, excitatory neurotransmitters are released and ganglion cells depolarize and fire AP.
56
Where do optic nerve fibers project?
The majority pass from the lateral geniculate nucleus of the thalamus where the informtion from the different ganglion cell types is kept distinct. Input in the lateral geniculate nucleus also receive inputs from the brainstem reticular formation and input relayed back from the visual cortex.
57
Describe how the auditory cortex is arranged.
Neurons responding to different pitches are mapped along the auditory cortex in a manner that corresponds to region of the basilar membrane. Different areas of the auditory cortex are even further specialized.
58
Describe sensory transduction of photoreceptor when light strikes:
Retinal dissociate from opsin, opsin changes shape and interact with transducin, transducin activates cGMP phosphodiesterase. This enzyme degrades cGMP causing closure of ligand-gated cation channels and this results in an hyperpolarization of the cell.
59
Describe retinal:
It can be converted into Vitamin A from which it is derived and the grater the light intensity the more retinal is converted into vitamin A.
60
What is selective attention?
Avoiding distraction of irrelevant stimuli while seeking out and focusing on stimuli that are momentarily important. Cause shifts from alpha to beta rhythm.
61
What are the two regions that olfactory sensation reaches?
1) Hippocampus: learning and memory, turn short term memory into long term memory.
2) Amygdala: controls many primal responses to perceived threats, including conscious and visceral.
62
List the three isoforms of iodopsin:
L cones: long wavelength (red)
M cones: medium wavelength (green)
S cones: small wavelength (blue)
63
Describe step 10 in NMJ:
Energized myosin-cross bridges on thick filaments bind to actin: A+M°ADP°Pi--> A°M°ADP°Pi
64
Describe the waking state:
Far from homogeneous. The most prominent wave pattern is the alpha wave. Awake state is characterized by a widespread activation of the cortex and the thalamus.
65
Describe cones photopighment:
Is iodopsin, it has three isoforms that responds to blue, red and green light. The three isoforms have overlap in their response to light so is possible to interpret many graduation of colors.
66
What is muscle fatigue?
Decline in muscle tension as a result of previous contractile activity. Results in decreased shortening activity and slower rate of relaxation.
67
What are the two components that makes vision?
An optical component (the eye) that focuses the visual image on the receptor cell.
A neural component that transforms the visual image into a pattern of graded and action potential.
68
Why is the code of olfactory information both spatial and temporal?
Axons from sensory receptor cells that share a common receptor specificity synapse together on the same olfacotory bulb neurons allowing the membrane to determine which region has been stimulated.
69
What does acute fatigue from high intensity, short duration exercise involve?
Decrease in ATP concentration and increase in concentration of ADP, Pi, Mg+, H+ and oxygen free radicals.
70
What are the two differences between the on and off pathway?
1) Bipolar cells of the on pathway spontaneously depolarize in the absence of input whereas bipolar cells of the off-pathway hyperpolarize in the absence of input.
2) Glutamate receptors of On-pathway are inhibitory whereas glutamate receptors of off-pathway are excitatory.
71
Describe filiform papillae:
Filament shaped
Most numerous
No taste buds
72
Describe the structure of a photoreceptor:
- Tip: composed of stacked layers of membrane called discs.
- Inner segment: contains mitochondria and other organelles and has a synaptic terminal that connect it to other neurons.
73
What is RES:
Reticular formation plus all other components involved in regulating consciousness. Neurons of RAS project through the cortex as well as to those areas of the thalamus that influence EEG.
74
What are glycolitic fibers?
Have few mitochondria. Possess high concentration of glycolytic enzymes and large stores of glycogen. They make quick burst of activity.
75
Describe endolymp and perilymph:
Endolymph: extracellular fluid that has high K+ concentration and low Na+ concentration.
Perilymph: Similar to the cerebrospinal fluid.
76
What are taste buds?
Taste cells surrounded by supporting cells, they have microvilli extending into the taste pores and are non-neuronal epithelial cells (secondary receptors).
77
Describe the receptors for umami submodality:
Scattered sensitivity, caused by amino acid glutamate. It binds to receptor and cause depolarization through G-protein mechanism. Alpha subunit activates adenylyl cyclase that convert ATP into cAMP and cAMP opens Ca2+ channels causing depolarization.
78
Describe step 15 of NMJ:
Cytosolic Ca2+ concentration decreases as Ca2+-ATPase actively transports Ca2+ into Sarcoplasmi reticulum.
79
What are the two phases of sleep (and describe their main features)?
NREM (Non rapid eye movement), is the initial phase and is subdivided into 4 stages, each successive stage is characterized by lower frequencies and higher amplitudes.
REM: EEG characteristic of an alert, awake state, is associated with dreaming. O2 assumption is higher compared to both NREM and awake stte.
80
Describe what happens when the head moves:
The semicircular canalas and the attached bodies of hair cells move with it. The fluid retains its original position and the moving ampulla is pushed against the stationary fluid and this cause bending of stereocilia (and the alteration of the rate of release of neurotransmitters).
81
How is the transmission of sound in the middle ear achieved?
It is achieved through a movable chain of three small bones: malleus, incus, stapes. These bones act as a piston and couple vibration of tympanic membrane to the oval window.
82
Describe the three ways in which vestibular infomration are used:
1) Control the eye muscle so that it remain fixed.
2) Reflex mechanisms for maintaining upright posture and balance.
3) Conscious awareness of the position and accelleration of the body, perception of space surrounding the body and memory of spatial information.
83
Describe step 14 of NMJ:
Cross bridges repeat steps 10 to 13 and this produce movement. Cycles of cross bridges continues as long as Ca2+ remains bound to troponin.
84
What are the 4 different types of papillae?
1) Filiform
2) Fungifrom
3) Foliate
4) Vallate
85
What are the three poitns that favors a transition to full awake from sleep?
- Suprachiasmic nucleus
- Negative energy balance
- Limbic system activity.
86
Describe the receptors for bitter submodality:
Most sensitive receptors are on posterior side of the tongue. Highest sensitivity. Bitter tastants bind to receptor and cause depolarizatin through a G-proteins mechanism. Alpha subunit activates phospholipase C, which converts phosphoinotisol (PIP2) into inotisol triphosphate (IP3). IP3 cause release of Ca2+ from intracellular stores and this cause depolarization.
87
What is gamma rhytm?
High frequency oscillations (30-100Hz) that speed acros large regions of the cortex.
88
Describe retinal processing of signals:
A significant amount of signal processing occurs within the retina. Synapsese between receptors, bipolar cells and ganglion cells are interconnected by a layer of amacrine cells. This allow retina to process information such as basic shapes and direction of movement.
89
Describe the two ways by which the iris regulates the diameter of the pupil:
- Stimulation of parasympathetic fibers makes the pupil smaller.
- Stimulation of sympathetic fibers makes pupil larger
90
Describe step 5 of NMJ:
Ach binds to nicotinic receptors on motor end plate and this increase the permeability to K+ and Na+. Receptors is Na+ channels, K+ efflux is due to open of voltage gated channels.
91
What do lens consists of?
Consists of crystal proteins sorrounded by elastic, transparent capsule.
92
What is the difference between the membrane potential of photoreceptors and all the rest of receptor cells?
Photoreceptor is depolarized (-35 mV) at resting membrane potential and hyperpolarized (-70 mV) when exposed to its adequate stimulus.
93
What are the two anatomically separate groups of hair cells?
1) A single row of inner hair cells: stereocilia extends in the endolymph and transduce pressure waves.
2) Three raws of outer cells: stereocilia are embedded in an overlying tectorial membrane.
94
Describe sleep:
We have got a transition from beta to alpha rhytm and shifts toward lower frequencies, larger amplitueds wave patterns known as theta ryhtm (4-8Hz) and delta rhythm (<4Hz).
95
What does the vestibular apparatus consists of?
3 membranous semicircular canals and two saclike swellings called utricle and saccule.
96
Describe the second step in hearing:
Is the transmission of sound energy from the tympanic membrane through the middle ear cavity to the fluid-filled inner year.
97
What are the four phases of NREM (describe them)?
N1: theta waves begin to be interspersed among the alpha pattern.
N2: High frequency burst called sleep spindles and large amplitude K complexes occasionally interupt the theta rhytm.
N3: Delta waves with theta rhytm appear
N4: Dominant pattern is delta rhytm.
98
What are the three perpendicular axes?
Horizontal, verticlar and anterio/posterior.
99
Describe foliate papillae:
Leaf-shaped, in folds on the side of the tongue, contains most sensitive taste buds.
100
Describe step 9 in NMJ:
Ca2+ binds to troponin on the thin filaments, tropomyosin move away uncovering cross bridges binding sites on actin.
101
Describe Actin, Tropomyosin and Troponin:
Actin: contractile protein, each G actin has a binding site for myosin.
Tropomyosin: regulatory protein, overlaps binding myosin binding site on actin and inhibit interaction whe it's in relaxed state.
Troponin: regulatory protein, forms a complex with other two proteins. Troponin binds Ca2+ reversibily and once it is bound it changes conformation to pull tropomyosin away from the binding sites. Ca2+ binding regulates contraction because it moves the tropomyosin away and allow myosin to interact with actin.
102
What do axons of ganglion cells form?
They form the optic nerve (Cranial Nerve II).
103
What are the two types of atrophy?
1) Disuse atrophy
| 2) Numbers of active motor units.
104
Describe the path of the two optic nerves:
The two optic nerves meet at the base of the brain to form the optic chiasm where some of the axons cross and travel within the optic tract to the opposite side of the brainn.
105
Describe step 4 of NMJ:
Ach diffues acros the synpatic cleft to the motor end plate.
106
Where does the lateral geniculate nucleus sends action potentials?
It sends AP to the visual cortex. Different aspects of the visual information continue along parallel pathways coded by ganglion cells and then they are processed simultaneously in a number of independent ways in different pat of the cortex before they are reintegrated.
107
What happens when stereocilia are bent backwards?
This cause the closure of the channels because the tip links are slacken.
108
Describe the role of parvalbumin:
It is almost absent in slow fibers, and its presence gradually increase in more active fibers. Small, soluble, diffusible, high-affinity calcium bidning protein that carries calcium from miofibrils back to sarcoplasmi reticulum where SERCA pump it back inside (contributes to sloer or faster relaxation).
109
Describe ciliary body:
Produces acqueous humour that fills the anterior chamber.
110
Describe the semicircular canals:
Detect angular accelleration during rotation of the head along the three perpendicular axes.
111
Describe middle vascular (tunic) layer IRIS:
Colored part of the eye, controls light entering the pupil and smooth muscle determine the size of the pupil.
112
What are the two ways through which the wall fo the scala vestibuli can dissipate the waves?
The wall of scala vestibuli are bones.
1) Helicotrema: waves pass around the end of the cochlear duct into scala timpani
2) Dircelty across the cochlear duct into the scala tympani and this cause vibration fo the basilar membrane that activate the receptors of the organ of corti.
113
Describe fungiform papillae:
Mushroom shaped, they are scattered irregularly over the superior surface of the tongue and have taste buds.
114
Describe the cornea:
Layer of stratified squamous epithelium on the outer surface. Connective tissue matrix of small and transparent collagen fibers, elastic fibers and proteoglycans, with low water content.
115
Describe to what EEG is due:
Is due to synchronous graded potentials, summed postsynaptic potential in many neurons, especially in the pyramidal cells of the cortex.
116
Describe neural pathways of audition:
Cochlear nerve fibers enter the brainstem and synapse with interneuron there. Fibers from both ears often converge on the same neuron. Many of these neurons are influenced by arrival time and intensitites of input from the two ears.
117
How does the location of photosensitive proteins differs between rods and cones?
In rods forms intracellular structure while in cones they are continous with the plasma membrane.
118
How does sensory transduction of rods differs from cones?
Is identical except the membrane discs are contained in the cytosol and cGMP ligand-gated channles are on the surface membrane.
119
Describe neural pathway of vestibular info:
Information about hari cell stimulation is relayed from vestibular apparatus via vestibular branc of the vestibulocochlear nerve and pass from the thalamaus to finally arrive in the parietal lobe.
120
Descibe the utricle and the saccule:
They provide information about linear accellaration of the head and changes in head position relative to the force of gravity.
121
Describe olfactory neurons:
Olfactory neurons lie in olfactory epithelium on upper surface of the nasal cavity. Mature cells are specialized afferent neurons with a single enlarged denrite that extend on the surface of the epithelium. It has got several long nonmotile cilia that extends from the tip of the dendrite and lie along the olfactory epithelium.
122
Describe flow of information from the brainstem in auditory neural pathways:
From the brainstem the info is submitted via a polysynaptic pathway to the thalamus and on to the auditory cortex.
123
What are myofibrils?
Structures that give muscles its striate appearence, arrangments of thick and thin filaments made of actin and myosin.
124
Describe step 6 of NMJ:
More Na+ moves into the fiber at the motor end plate than K+ moves out and this result in a depolarization inducing a end plate potential.
125
Describe the receptors contained in the semicircular canals:
Receptor cells contain stereocilia encapsulated within a gelatinous mass called the cupula.
126
What is electroncephalogram?
A recording of the brain electrical activity.
127
Describe monocular and binocular vision:
With both eyes open, the outer regions of the visual field is perceived by one eye only (zones of monocular vision) whereas in the central portion of the field is perceived from the two eyes and overlap (zones of binocular vision).
128
What is a motor unit?
Motor neurons and skeletal muscle fibers it innervates. One motor neurons innervates many myofibers but one myofiber is innervated by just one motor neuron.
129
Why is olfaction unique compared to others senses?
It is unique among all sense because olfaction doesn't have to travel through the thalamic relay to reach its final CNS target.
130
What is conscious experience?
Experience a person is aware of during any state of consciousness.
131
What are the two ways in which we can define a person state of consciousness?
1) by behavior
| 2) by patterns of brain activity that can be recorded electrically.
132
Describe step 16 in NMJ:
Removal of Ca2+ from troponin restores blockin action of tropomyosin and cross bridges cycles cease and muscle fibers relaxe.
133
Describe the route made my odorants:
Odorants must first diffuse through the air and pass into the nose to the region of olfactory epithelium. Once there they enter the mucous that covers the epithelium and the bind to specific odorants on the cilia.
134
Describe scala vestibuli and scal tympani:
Scala vestibuli is above the cochlear duct and begins at the oval window. Scala tympani is below and connects the middle ear at the round window.
135
Describe hair cells:
Mechanoreceptors that have stereocilia protruding from one end.
136
What is the relationship between the distance the tympanic membrane moves and the loudness of the sound?
The distance the membrane moves, although very small, is a function of the force with which air molecules hit it.
137
Describe sensory transduction of photoreceptor in absence of light:
In absence of light, guanylyl cyclase converts GTP into cGMP at high concentration. cGMP maintain outer segment ligand-gated cation channles open and a persistent flux of Ca2+ and Na+ depolarize the cell.
138
What are the two characteristics of waves recorded by EEG (and what do they represent)?
1) Amplitude: indicates how much electrical activity of the same type is occuring beneath the electrode. Indicateds the degree of synchronous firing of neurons.
2) Frequency: how often it cycles from maximal to minimal amplitude and back.
139
Describe step 3 of NMJ:
Calcium entrance triggers the release of Ach from the axon terminal.
140
Describe light and dark adaptation of rods:
In bright light more rhodopsin is broken down to vitamin A whereas in darker conditon more rhodopsin is formed increasing sensitivity. In bright light condition the differential response of cones allow for a good color vision whereas in dim light only the highly sensitive rods are able to respond.
141
Describe the tympanic membrane:
Tympanic membrane is stretched across the end of the external auditory canal and as sound waves push against it the membrane vibrates. Under higher pressure the membrane bows inward, under lower pressure the membrane bow outward.
142
What happens when stereocilia are bent towards?
Fibrous connections called tip link pull open mechanically gated cation channels resulting in K+ efflux and consequent depolarization. Depolarization cause voltage-gated Ca2+ channels at the base of the cell to open triggering the release of neurotransmitters.
143
Describe receptors for sweet submodality:
Most sensitive receptors are on the tip of the tongue. Shares lowest sensitivity with salty. Sugars or artifical sweeteners bind to receptor and cause cell to depolarize via G-proteins coupled mechanisms. The alpha subunit of G-proteins activates adenylate cyclase which produces cAMP. cAMP activates a kinase that phosphorylate K+ channels causing themo to close.
144
Describe step 12 in NMJ:
ATP binds to myosin, breaking linkage between actin and myosin and thereby allowing cross-bridges to dissociated from actin. A°M+ATP-->A+M°ATP
145
What is coma?
Severe decrease in mental activity and function due to structural, physiological or metabolic impairment.
146
What are the two layers of the nervous tunic:
1) Pigmented retina: outer, pigmented layer consisting of pigmented cuboidal epithelium.
2) Sensory retina: inner layer of cone and rod cells sensitive to light.
147
Describe isometric and isotonic contractions:
Isometric contraction: generate tension but don't shorten the muscle, load is greater than forge generated by muscle.
Isotonic contractions: contractions shorten the muscle.
148
Describe T-Tubules and sarcoplasmic reticulum:
Ca2+ is stored in the sarcoplasmi reticulum (homologous to endoplasmic reticulum in normal cells). T-tubules and Sarcoplasmic reticulum are connected with junctions involving two integral membrane proeteins.
149
What are the three layers of the retina?
1) Photoreceptor
2) Bipolar
3) Ganglionic
150
Describe the resistence in relation to metabolic properties:
- Slow-oxidative myofibers can keep contracting indefinitely at maximum force output.
- Fast oxidative-glycolytic myofibers can keep contracting indefinitely at maximum force outpu.
- Fast-glycolytic myofibers lose their force producing ability within a few to several minutes.
151
Describe receptors for sour submodality:
Most sensitive receptor on lateral side of the tongue. Hydrogens ions from acids cause depolarization via three mechanisms:
1) Directly enter the cell via H+ channels.
2) Bind to gated K+ channels, closing it and preventing K+ efflux.
3) Bind to ligand gated ion channels for positive ions and by opening them they cause a depolarization.
152
Describe the first step in hearing:
Is the entrace of sund waves into the external auditory canal. Shapes of the outer ear and external auditory canal help amplify and direct the sound to the tympanic membrane.
153
What is habituation?
If a simulus is repeated but is irrelevant, behavioral response to stimulus progressively decrease. It involves a decrease in synpatic transmission in the involved pathways.
154
What does RES consists of?
Consits of clusters of nuerons and neural pathways originating in both the brainstem and hypothalamus.
155
What is the vestibular apparatus?
A connected series of endolymph filled membranous tubes that also connect with the cochlear duct.
156
By which type of cells are light signals converted into action potentials an why?
Light signals are converted into action potential by the interaction between photoreceptor with bipolar and ganglion cells. Bipolar and photoreceptor only undergo graded potentials because they lack the voltage gated channles for action potential. Thus, ganglion cells are the first to fire an Action Potential.
157
What are the three phases of twitch contraction?
1) Latent period: period from the action potential to the onset of the contraction.
2) Contraction phase: time that tension is developing due to cross bridges cycling.
3) Relaxation phase: tension is decreasing due to the amount of time it takes to get all Ca2+ back into the sarcoplasmi reticulum.
