Week 4 (Exam 2): Sensory Systems; Muscles & Skeletal Systems Flashcards
sensory receptor cells
sensory neurons with specialized membranes in which receptor proteins are embedded
sensory organs
a group of sensory receptors that converts particular physical & chemical stimuli into nerve impulses that are processed by a nervous system and sent to the brainmk
sensory transduction
the conversion of physical or chemical stimuli into nerve impulses
chemoreceptors
receptors that respond to molecules that bind to specific protein receptors on the cell membrane of the sensory receptor
first step of smelling
olfactory sensory neurons sense odorants that bind to specific receptors on chemosensitive hairs that project into the mucus
second step of smelling
action potentials produced in response to the binding of odorants to membrane receptors are sent to the olfactory interneurons
third step of smelling
interneurons integrate the odorant info received by olfactory receptors before sending it to the brain
process of smelling
odor molecules bind to sensory receptors —> intracellular G protein-coupled receptors activate —> opening of Na+ and Ca2+ ion channels —> depolarize the receptor & produce EPSPs —> interneurons in the olfactory bulb transmit the combined info to the brain
is an action potential fired with taste buds?
no
mechanoreceptors
respond to physical deformations of their membrane produced by touch, sound, stretch, pressure, or motion
hair cells
specialized mechanoreceptors that sense movement and vibration
-orient the animal’s body wrt gravity, detect motion, & hear
stereocilia
nonmotile cell-surface projections on hair cells whose movement causes a depolarization of the cell’s membrane
statocysts
a type of gravity sensing organ found in most invertebrates
statolith
a dense particle that moves freely within a statocyst, enabling it to sense gravity
vestibular system
a system in the vertebrate inner ear made up of 2 statocyst chambers and 3 semicircular canals
components of the outer ear
pinna, auditory canal, & tympanic membrane (eardrum)
middle ear components
malleus, incus, tapes
function of the middle ear bones
amplify the vibrations of the tympanic membrane & transmit them to a thin membrane of the cochlea
cochlea
a coiled chamber within the skull containing hair cells that convert sound (pressure) waves into an electrical impulse that travels to the brain
what do vibrations in the membrane do?
create fluid waves in the cochlea
what do the fluid waves in the cochlea do?
induce motion of the basilar membrane
what does motion in the basilar membrane do?
bends the stereocilia & stimuulates the hair cells to release EPSPs
electromagnetic receptors
respond to electrical, magnetic, or light stimuli
photoreceptors
molecules whose chemical properties are altered when they absorb light
opsin
a photosensitive protein that converts the energy of light photons into electrical signals in the receptor cell
- arranged in cylindrical groups in vertebrates
retinal
a derivative of vitamin A that absorbs light & binds to rhodopsin
rhodopsin
a transmembrane in the photosensitive receptor cells in the retina of vertebrates
types of eyes
eyecups, compound eyes, single-lens eye
eyecups
an eye structure found in flatworms that contains photoreceptors that point up & to the left or right
compound eyes
consists of a number of ommatidia
ommatidia
individual light-focusing elements
-the number of ommatidia determines the resolution of the image
single-lens eyes
works like a camera to produce a sharply defined image of the animal’s visual field
retina
a thin tissue in the back of the vertebrate eye that contains the photoreceptors & other nerve cells that sense & initially process light stimuli
rod cells
a type of photoreceptor cell on the vertebrate retina that detects light and shades ranging from white to shades of gray & black, but not color
cone cells
a type of photoreceptor cell on the vertebrate retina that detects color
which animals had the first muscle fibers?
cnidarians
fiber
a muscle cell which produces forces on an animal’s body & exerts forces on the environment
-uses ATP generated through cellular respiration
what do all muscle fibers contain?
actin & myosin
filaments
a thin thread of proteins that interacts with/ other filaments to cause muscles to shorten
what are the two groups of muscles?
striated & smooth
striated muscle appearance
striped under a light microscope due to regular thick (myosin) & thin (actin) filament spacing
two types of striated muscle
skeletal & cardiac
skeletal muscle function
connects to the body skeleton to move an animal’s limbs & torso
-elongated & multinucleated
cardiac muscle function
make up the walls of the atria & ventricles & contract to pump blood through the heart
-less elongated
-branched
-contain fewer nuclei per cell
where are smooth muscles found
in the walls of arteries, the respiratory system, the digestive, & excretory systems
-appears uniform under the light microscope
myofibrils
long rodlike structures in muscle fibers that contain parallel arrays of actin & myosin filaments
where is tropomyosin found?
in the grooves formed by the actin helices
what does troponin do
helps to make more tropomyosin
-regularly spaced along the thin filament
what does each myosin molecule consist of?
2 long polypeptide chains arranged in parallel to form a thick filament
z discs
a protein backbone found regularly spaced along the length of a myofibril
sarcomere
the region of myofilaments located within muscle myofibrils that span from one z disc to the next
what is the basic contractile unit of a muscle?
the sarcomere
what is at the middle of a sarcomere?
myosin thin filaments
what is at the middle of thick filaments?
myosin heads that reversed their orientation in each half of the sarcomere
how are the thin filaments related to the myosin thick filaments?
they overlap
what links the myosin filaments to the z discs at the end of the sarcomere?
titin protein
what gives striated muscle its appearance?
the regular pattern of actin & myosin filaments within sarcomeres along the length of the fiber
what sort of lattice are thick and thin filaments arranged in?
hexagonal lattice
sliding-filament model
the hypothesis that striated muscles produce force & change length by the sliding of actin filaments relative to myosin filaments
when does actin-myosin overlap decrease?
when myofibrils are stretched
when does actin-myosin overlap increase?
when myofibrils are relaxed
what causes nearly all length change during a muscle contraction?
the sliding of actin filaments with respect to myosin filaments within individual sarcomeres
what is a cross-bridge
the binding of the head of a myosin molecule to actin at a specific site between the myosin & actin filaments
what is the cross-bridge cycle?
repeated sequential interactions between myosin heads that bind to & release from sites on actin filaments, forming & unforming cross-bridges, that cause the thin filament to slide relative to the thick filament & a muscle fiber to contract
first step of the cross-bridge cycle
the myosin head binds ATP
-myosin head detaches from actin & readies it for attachment to actin again
second step of the cross-bridge cycle
the myosin head hydrolyzes ATP to ADP & inorganic phosphate
-hydrolysis of ATP leads to a conformational change with the myosin head cocked back
-ADP & inorganic phosphates remain bound to myosin head
-myosin head is in a high-energy state
third step of the cross-bridge cycle
myosin head binds to actin, forming a cross-bridge
fourth step of the cross-bridge cycle
myosin head releases ADP & inorganic phosphate
-results in the power stroke
power stroke
the stage in the muscle cross-bridge in which the myosin head pivots & generates a force, causing the myosin & actin filaments to slide relative to each other
what is the motor endplate?
the postsynaptic region on a muscle cell where acetylcholine birds w/ receptors
first step of excitation-contraction coupling
action potential —> release of acetylcholine & depolarization of skeletal muscle cell
second step of excitation-contraction coupling
depolarization is conducted into the interior of the fiber by the infoldings of the cell membrane
third step of excitation-contraction coupling
depolarization —> release of Ca2+ from the sarcoplasmic reticulum
fourth step of excitation-contraction coupling
Ca2+ binds to the troponin, which causes movement of tropomyosin, exposure of myosin-binding sites on actin, & formation of cross-bridges to generate force & produce shortening of the muscle
what is the sarcoplasmic reticulum?
a modified form of the endoplasmic reticulum surrounding the myofibrils of muscle cells
what is the excitation-contraction coupling?
the process that produces muscle force & movement, by coupling the excitation of the muscle cell by a motor neuron to contraction of the muscle
what are antagonist muscles?
muscle pairs that pull in opposite directions at a joint to produce opposing muscles
flexion
the joint motion in which bone segments rotate closer together
extension
the joint movement that moves bone segments apart
agonist muscles
muscle pairs that combine to produce similar motions
what does the muscle’s ability to generate force depend on?
how much it is stretched
isometric
describes the generation of muscle force without a change in muscle length
lengthening contraction
the contraction of a muscle against a load greater than the muscle’s force output, leading to a lengthening of the muscle
triten contraction
a muscle contraction that results from a single action potential
tetanus contraction
a muscle contraction of sustained force resulting from multiple action potentials
motor unit
a vertebrate motor neuron & the population of muscle fibers that it innervates
what senses do the three semicircular canals in the mammalian inner ear provide?
a sense of angular motion and balance
what type of sensory receptor is a hair cell?
mechanoreceptor
Aging can sometimes lead to an increase in the stiffness at the base of the basilar membrane.
What affect would this have on a person’s hearing?
The person would lose the ability to hear high-pitched sounds.
What is the primary function of a statolith?
to determine the direction of gravity
the conversion of physical or chemical stimuli into nerve impulses is known as
sensory transduction
how are sound vibrations amplified in a vertebrate ear?
by movement of the tympanic membrane, the bones in the middle ear, and the fluid-filled region covered by the oval window
hair cells function by:
releasing neurotransmitters
what type of channel is associated with ion transport in stereocilia?
stretch-gated channel
what determines the specific wavelength of light absorbed by a cone cell?
the type of opsin present in the membrane
what structure is the opening in the eye through which light passes called
the pupil
within the human eye, photoreceptors are located within the:
retina
cone cells most likely evolved from:
rod cells
is color vision in vertebrates made possible by cone cells?
yes
what structure is the light-absorbing compound used by photoreceptors?
retinal
You take a human smooth muscle cell and block the release of calcium from the sarcoplasmic reticulum. What effect does that have on contraction of that smooth muscle cell, and why?
contraction still occurs because Ca2+ can enter the cell directly through Ca2+ channels in the plasma membrane and bind to calmodulin
what event does the power stroke correspond to in muscle contraction?
the sliding of actin relative to myosin filaments
vertebrate smooth muscle cells are activated when Ca2+ binds to:
calmodulin
why is calcium necessary for muscle contraction?
calcium is needed to activate troponin so that tropomyosin can be moved to expose the myosin-binding sites on the actin filament
which molecule binds calcium?
troponin
what stimulates a skeletal muscle cell to contract?
an impulse from a motor neuron
ATP hydrolysis allows for what component of skeletal muscle contraction?
cocking of the myosin head to its high-energy position
what is the basic contracting unit of a skeletal muscle
sarcomere
what is a muscle fiber?
a single cell of a muscle
what is tetanus?
a muscle contraction of sustained force resulting from repeated action potentials
maximum force is generated by a muscle contraction when:
the sarcomere is at intermediate length before contraction begins
in an antagonist muscle pair:
one muscle undergoes flexion, whereas the other undergoes extension
during ___ bone segments move closer together, whereas during ___ bone segments move further apart
flexion; extension
muscle contractions have ___ force at slower shortening velocities compared to higher shortening velocities
increased
a single motor neuron and the population of muscle fibers that it innervates is called a:
motor unit
when skeletal muscles contract such that bone segments move closer together, this action is known as:
flexion
