Midterm 2 Flashcards
What is emmetropia?
Normal resting condition of lens when ciliary muscle is relaxed and lens is flat.
Describe step 13 of NMJ:
ATP bound to myosin split, energizing the myosin cross bridges: M°ATP–>M°ADP°Pi.
What are the two distinct ways by which photoreceptor interact with bipolar and ganglion cells?
1) On-pathway
2) Off-Pathway
What does the bind of an odorant activate in the cilia?
This activate a G-protein mediated pathway that increase cAMP that in turns opens nonselective cation channels and depolarizes the cell.
What is central and command fatigue?
Occurs when appropriate regions of cerebral cortex fails to send excitatory signals to motor neurons.
What is epylepsy?
A common neurological disease associated with abnormally synchronized discharges of cerebral neurons.
Describe the sclera:
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.
What is a state of consciousness?
The level of alertness, refers to whether a person is awake, asleep or in coma.
Describe utricle hair cells:
Point nearly straight and respond when the tip of the head is away of horizontal plane or to linear accellaration on the horizontal plane.
What are the two factors (and relative subfactors) controlling muscle tension?
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
Describe convergence in retina:
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.
Describe step 2 of NMJ:
Ca2+ enters the axon terminal through voltage gated Calcium channels.
Describe pigmented retina and its role:
Single layer of cells filled with melanin. Pigmented epithelium and choroid absorb light that bypass the photoreceptive cells preventing refelction and scattering.
Describe receptors of salty submodality:
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.
What are the neuronal pathways for taste?
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.
List the 4 ATP functions in skeletal muscle contraction:
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.
What is brain death?
Occurs when the brain no longer functions and has no possibility to function again.
Describe Off-Pathway:
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.
What does direction and roation determines?
It determinse the direction in which stereocilia are betn and which hair cells are stimulated.
What are the two proteins embedded in the sarcoplasmi reticulum?
- Dihydropyridine receptor: acts as a voltage sensor
- Ryanodine receptor: forms a Ca2+ channel.
What are the three ways in which muscle fibers can generate ATP?
1) Phosphorylation of ADP by creatine phosphate
2) Oxidative phosphorylation of ADP in mitochondria
3) Phosphorylation of ADP by glycolitic pathways in the cytosol.
Describe step 11 in NMJ:
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
Describe step 7 of NMJ:
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.
Describe Vallate papillae:
Largest and least numerous, they have taste buds
Describe alpha wave:
(8-12Hz). Best recroded over parietal and occipital lobes. It is associated with decreased level of attetion.
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.
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.
What is EEG arousal?
Transformation from alpha to beta rhytmn when people are attentive or focused.
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.
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.
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.
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.
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.
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.
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.
Describe off-center receprive field:
More Action Potential frequency when light is off or when light doesn’t hit the center of the field.
What does the amygdala do with odours?
By receiving inputs direclty from the olfactory bub the amygdala ties odours into learning, memory, visceral satisfation.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
Describe On-center receptive fields:
Generate more AP when light is directed on the center of the receptive field. Response is to intense light.
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).
Describe ciliary muscles:
Smooth muscles that control the lens shape.
Describe the muscle movement:
The force generated against the mass is amplified throught the lever arm, and is a torque: t=rFsin0
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.
Describe step 1 of NMJ:
Action potential is initiated in the motor neurons and propagates to the motor neuron axon terminal.
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.
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.
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.
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.
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.
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.
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.
List the three isoforms of iodopsin:
L cones: long wavelength (red)
M cones: medium wavelength (green)
S cones: small wavelength (blue)
