Ch 50 - Sensory and Motor Mechanisms
Terms in this set (75)
a muscle fiber is
-a long muscle cell with >1 nucleus
-a bundle of myofibrils
a muscle contains bundles of
skeletal muscle is an organ comprised of
-bundles of muscle fibers
-fibrous connective tissues
myofibrils are made up of chains of repeating subunits called...
each sarcomere in a myofibril contains
-thin filaments of actin that anchor to Z disk
-thick filaments of myosin that attach to thin filaments
what causes the striations in skeletal muscles?
alignment of the z-discs due to parallel myofibrils
why are there no striations in smooth muscles?
the z-discs are not aligned b/c the myofibrils are not parallel to allow contraction in multiple directions
skeletal muscle contracts via...
microfilaments crawling along actin
movement of skeletal muscle for contraction is produced by...
changes in conformation of myosin head
a contracting muscle shortens, the filaments that bring about contraction....
stay the same length
muscle contraction requires repeated cycles of
binding and release, where myosin head freed from cross-bridge cleaves to newly bound ATP and binds again to actin
when a muscle is at rest, what prevents muscles from contracting all the time?
myosin binding sites on thick actin are blocked by tropomyosin protein
when a muscle switches from being at rest to contracting, what allow the muscles to contract again?
calcium binds to troponin, which moves tropomyosin to unblock the myosin binding site on actin
how does rigor mortis occur after death?
calcium gets released and muscles contract
but ATP levels drop(no more being made) so myosin head can't release to relax muscles
what role to motor neurons play?
propogate action potential into muscle tissue
what does action potential do once propogated to muscle tissue from motor neurons?
it causes calcium release, which leads to muscle contraction
what are the 5 types of sensory receptors?
physical deformation caused by mechanical energy
list the 4 types of mechanoreceptors
pressure, stretch, motion sensitive hairs, membranes
motion sensitive hairs and membranes detect...
substrate, air, or fluid movements
mechanoreceptors: pressure receptors
stacks of cells with neuron dendrites b/w layers
-occur in dermis
instensity felt in pressure receptors may depend on...
-which receptors/neurons are activated(strong pressure - in deeper layers)
-rate of action potentials(strong = high freq)
-# of receptors activated
mechanoreceptors: stretch receptors
responsive to distention of various organs and muscles
carotid artery stretch receptors detect...
increase in blood pressure
pulmonary stretch receptors detect...
when lungs are inflated
muscle spindles(stretch receptors) detect
changes in length of its muscle
muscle spindles induce action potential by...
opening stretch-gated ions
mechanoreceptors: motion sensitive hairs
detect objects, predator/prey movements, water movement/current, low frequency vibrations(sound)
how to motion sensitive hairs detect anything?
sensory neuron dendrite wind around base of hair
where do spiders have motion sensitive hairs?
on their legs
where do manatees have motion sensitive hairs?
on their face
motion sens. hairs on australian crayfish
they have hair pit organs
hair pit organs and lateral line systems detect...
water currents, predator prey movements and low frequency vibrations (sound)
lateral line system
-occurs in most aquatic vertebrates
-includes canal made of hair cells, sensory hairs, cupula(gelatinous), and nerve fibers
motion sensitive hairs: sharks have...
hair pit organs(dorsal) and a lateral line system
how does the trap jaw ant detect prey?
they have sensitive trigger hairs near jaw that tells it when to snap shut
how to insect hear?
hairs of varying length / thickness that detect different frequencies
hearing in invertebrates
tympanal organ varies in location(body, head, leg)
ears are basically
tympanic membranes stretched over air chamber w/ hairs
hearing: organ of corti
translates vibrations into action potential in auditory nerve
in vertebrates, the ear conveys ____ and _______
volume(amplitude) and pitch(frequency)
how is the ear able to pick up different frequencies and volumes?
basilar membrane varies in width/thickness so that diff part responds to diff freq
-higher volume = faster portion vibrates
chemoreceptors respond to
- individual kinds of molecules
-solute concentration of solution
gustation and olfaction are governed by
binding of molecules(oderants or tastants)
describe chemoreceptors on grasshopprs
-taste receptors on hairs on feet and moutparts
-smell receptors on antannae
describe chemoreceptors on dogs
in nose and on tongue
in mammals, taste buds are...
a group of modified epthelial cells with receptor proteins
list the 5 types of taste that taste bud cells can signal
sweet, sour, umami, bitter, sour, salty
a single taste bud cell can signal..
only 1 taste
a single taste bud can..
have cells sensitive to each of 5 tastes, though some might have more of a certain taste cell
in mammals, oflaction(small) cells are
specialized neurons with receptors on dendrites that bind with odorants
smell in insects
odorants pass into pores on hairs on antannae
secreted or excreted chemical factor that triggers a social response in members of the same species
- sex, alarm, feeding...
Electromagnetic receptors respond to
electromagnetic energy(light, electricity, magnetism)
Electromagnetic receptors in snakes
pit organs beneath nostrils can detect radiant heat in infrared wavelengths
Electromagnetic receptors in platypus
use 40K electroreceptors &
60K mechanoreceptors on their bill to hunt
Electromagnetic receptors in electric fish
used for navigation, object detection, and communication
Electromagnetic receptors in elasmobranchs, sturgeon, etc
Ampullae of Lorenzini help them hunt
light detecting organ: simple eye cup
provides light intensity and direction but NO images
light detecting organ: compound eye
many light detectors(ommatidium) where each sees small part of big pic and has own lens
-effective at detecting movement
planarians(flatworms) have what light detecting organ?
simple eye cup
arthropods have what light detecting organ?
light detecting organ: single lens eyes
-pupil/iris regulate light intensity
-adjustable lens focuses light into retina
single lens eyes: cornea
lets in light and acts as a fixed lens
single lens eyes: photoreceptors
light sensitive cells contained in the retina
single lens eyes are found in
spiders, mollusks, jellies, and vertebrates
single lens eyes in mammals
changes in lens shape finely focuses light
retina has 2 types of light sensitive cells (photoreceptors):
Rods - light‐sensitive; no colors
Cones - less light‐sensitive; distinguish colors
contains pigments consisting of 2 bonded components:
Retinal - light absorbing molecule (derived from vitamin A)
Opsin - a protein(diff opsin = diff pigment)
retina rods: pigments
Retinal + opsin = Rhodopsin
-Light causes conformational change in Rhodopsin, inducing action potential in cell body and then optic nerve
retina cones: pigments
Retinal + opsin = photopsin
-3 different photopsins (w/ dif opsins) detect different wave lengths
color blindness is due to either
• Defective opsins
• Lesions of visual cortex
concerned with color vision
naked dendrites in epidermis
-respond to excess heat/pressure, chemicals released from damaged tissues
thermoreceptors respond to
have diff receptors for diff temp changes
-capscaisin activates high temp receptor
-menthol activates low temp receptor
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