Bio 225 Unit 2

key differences of smooth muscle from skeletal muscle

-no sarcomeres

-no t-tubules

-often connected by gap junctions

-contract in all dimensions

-different mechanism of EC coupling

-regulated by nerves, hormones, and physical conditions

neurogenic muscle

muscle stimulated by neurotransmitters

what prevents summation or tetanus in cardiac muscle?

long refractory periods

features of action potentials in cardiac muscle

-action potential with prolonged repolarization

-contraction similar to slow-twitch

-long refractory period prevents summation

-high frequency stimulation causes arrhythmic cardiac muscle contractions

steps of action potential in cardiac muscle

-depolarization of plasma membrane(sarcolemma) opens DHPR, allowing Ca2+ to enter the cell

-elevated Ca2+ triggers opening of RyR, allowing Ca2+ to escape the SR. elevated cytoplasmic Ca2+ triggers actino-myosin ATPase

-after repolarization, ion pumps begin returning Ca2+ to resting locations, outside the cell and in the SR

what types of animals usually do not have a circulatory system?

usually small, aquatic animals

three main components of circulatory system

-pump(heart)

-system of tubes, channels, or spaces(blood vessels)

-fluid that circulates through the system(blood or hemolymph)

how are fluids moved through circulatory system in relation to pressure?

pressure of fluid is increased in one part of the body, causing the fluid to flow down its pressure gradient

what are the benefits of closed circulatory systems?

-rapid adjustments in O2 and nutrient delivery to specific tissues

-ultrafiltration of the blood

-supports relatively high pressures

law of bulk flow

Q = ΔP/R

how will flow be in a closed circuit?

flow will be uniform at all points

multipolar neuron

many processes extend from the cell body; many dendrites one axon

bipolar neuron

two main processes from cell body

unipolar neuron

one main process from cell body

sensory neuron(afferent)

carries impulses from periphery to the central nervous system

interneuron

connects neurons to other neurons

motor neuron

carry impulses from central to effector organ

general organization of nervous systems

incoming stimulus triggers sensory receptors, which leads to the stimulation of afferent neurons. signals are sent to the integrating center through interneurons and then sent to the effector organs through efferent neurons

nuclei

groups of neuronal cell bodies within the CNS

ganglia

groups of neuronal cell bodies in the PNS/outside the CNS

tracts

bundles of axons in the CNS

nerves

bundles of axons in the PNS/outside the CNS

sympathetic nervous system

-most active during stress or physical activity

-"fight or flight"

-increases heart rate and breathing, directs blood to working muscles

parasympathetic nervous system

-most active during periods of rest

-'resting and digesting"

-redirects energy toward maintenance activities, such as digestion

where are sensory stimuli detected?

in neurons or accessory cells

types of sensory receptors

-chemoreceptors

-mechanoreceptors

-photoreceptors

-thermoreceptors

-electroreceptors

-magnetoreceptors

chemoreceptors

detect the presence of chemicals in environment

mechanoreceptors

detect pressure and movement, including proprioception

photoreceptors

detect light

thermoreceptors

detect temperature

electroreceptors

detect electrical fields

magnetoreceptors

detect magnetic fields

adequate stimulus

non-preferred (most sensitive) stimulus modality

polymodal receptors

sensitive to more than one stimulus modality

nociceptors

detect various strong, potentially damaging stimuli

polymodal nociceptors

transduce thermal, mechanical, chemical cues into signals sensed as pain

what encodes modality info from polymodal receptors?

pattern of action potentials

what info is used to convert info ab stimulus into action potentials?

-stimulus modality

-stimulus location

-stimulus intensity

-stimulus duration

what is true about afferent neurons and receptors?

afferent neuron associated with one type of receptor

-follows a particular pathway for integration

what is perception based on?

receptor/path, not stimulus

receptive field

region of sensory surface that causes response when stimluated

what does a smaller receptive field result in?

precise location of stimulus

how can the ability to localize stimuli be improved?

-using more than one sensory receptor cell

-lateral inhibition

acuity

ability to resolve fine detail of stimulus

how do sensory neurons code stimulus intensity?

changes in action potential frequency

-strong stimuli=high frequency

dynamic range

range of stimulus intensities over which a receptor exhibits an increased response

threshold of detection

weakest stimulus that produces a response in a receptor

saturation

top of dynamic range(maximal response)

discrimination

ability to detect differences between two stimuli

narrow dynamic range

small change in stimulus causes large change in action potential frequency

-good sensory discrimination

large dynamic range

large change in stimulus causes small change in action potential frequency

-poor sensory discrimination

how does sensory discrimination improve?

distributing responses amongst receptor population

tonic receptors

slowly adapting receptors that respond for the duration of a stimulus

phasic receptors

rapidly adapt to a constant stimulus and encode changes in stimulus

sensory adaptation

decreased response to stimulus as duration increases

types of chemoreceptors

exteroceptors and interoceptors

where is the vertebrate olfactory system located?

located in roof of nasal cavity

what type of receptor cells are in the vertebrate olfactory system?

bipolar neurons with cilia

odorant binding proteins

allow lipophilic odorants to dissolve in mucus

what do odorant receptor neurons express?

G-protein coupled receptors

odorant binding process

-binding of odorant to receptor causes conformational change

-activated G-protein(G-olf) moves through membrane and activates adenylate cyclase

-adenylate cyclase converts ATP into cAMP

-cAMP opens cAMP ion-gated ion channels

-Ca2+ and Na+ enters cell causing generator potential

-Ca2+ opens Ca2+ activated Cl- channels causing Cl- to leave the cell, increasing depolarization

-generator potential opens voltage-gated Na+ channels, triggering action potentials

what does odorant binding cause?

-formation of cAMP

-opening of ion channels

-depolarization

if afferent odorant receptor neurons have the same G-PCR, where do they bind?

same region of olfactory bulb(glomerulus)

what are tastebuds?

vertebrate gustatory receptors

what are vertebrate gustatory receptors composed of?

neuroepithelia(taste receptor cells)

salty taste pathway

-Na+ from food enters through Na+ channel

-resulting depolarization opens voltage-gated Ca2+ channels

-influx of Ca2+ causes neurotransmitter release

sour taste pathway

-H+ ions from sour foods activate Otop1 channels

-H+ ions enter cell and lower pH

-low pH activates Na+ channels and Na+ enters the cell

-voltage gated Ca2+ channels open

-influx of Ca2+ causes neurotransmitter release

sweet pathway

-substance binds to receptor which leads to a conformation change

-activated G-protein activates phospholipase C(PLC)

-PLC catalyzes conversion of PIP2 into second messenger IP3

-IP3 causes the release of Ca2+ from intracellular stores

-Ca2+ activates TRPM channels(non-selective) and Na+ enters cell

-depolarization causes a voltage gated channel to open

-ATP is released and acts as a neurotransmitter, binding to receptors on afferent neuron

how does vertebrate and invertebrate olfaction/gustation differ?

location and mechanism

mechanism for mechanoreceptors

couple mechanical stimuli to ion channels

variations on mechanoreception

-touch/pressure

-proprioception

-equilibrium/balance

-hearing

-baroreception (blood pressure sensing)

proprioceptors

monitor the position and movement of skeletal muscles and joints

what are mechanoreceptors for hearing and balance in vertebrates?

hair cells

what are hair cells "bathed in" and what does it cause?

endolymph; causes there to be high amounts of K+ outside of the cell relative to the inside

what causes the opening of mechanically-gated cation channels?

movement of stereocilia

what happens when there is bending towards the longest stereocilia?

more K+ channels are open, which causes depolarization

what happens when there is bending away from the longest stereocilia?

less K+ channels are open, which causes hyperpolarization

where are mechanoreceptors for equilibrium located?

inner ear

what detects linear acceleration and tilting?

maculae of the utricle and saccule

what detects angular acceleration?

cristae of the semicircular canal

what does the excitation and inhibition of angular acceleration depend on?

direction of movement and location of hair cells

ossicles

transform sound waves into deflections of basilar membrane

endolymph

fluid that fills the cochlear duct

-high K+, low Na+

perilymph

fluid that fills the vestibular and tympanic ducts

-high Na+, low K+

cochlea

a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

where do hair cells detect basilar membrane movements?

organ of corti

how do outer hair cells amplify sounds?

somatic electromotility

how does somatic electromotility work?

-change length in response to stimulation

-increase deflection of basilar membrane

-amplify sounds to inner hair cells

sound transduction pathway

-sound waves vibrate tympanic membrane

-middle ear bones transmit vibration to oval window

-oval window vibrates

-pressure waves in perilymph of vestibular duct

-basilar membrane vibrates in relation to tectorial membrane

-stereocilia on inner hair cells bend

-hair cells depolarize

-hair cells release glutamate

-glutamate excites afferent neuron

photoreceptive opsins

seven membrane-spanning GPCRS; localize to membranes in outer segments of vertebrate photoreceptors

how does phototransduction occur?

chromophore isomerization

summary of light-induced events

-opsins covalently bind vitamin-A derived chromophores

-photons cause isomerization of chromophore

-isomerization of chromophore leads to changes in opsin

-conformational change in opsin--> dissociation of chromophore from opsin

-G-protein signaling events cause changes in membrane potential

ciliary photoreceptor pathway

-11-cis retinal absorbs light and isomerizes into all-trans retinal

-all-trans retinal dissociates from opsin

-activated opsin activates PDE which converts cGMP into GMP

-decreased cGMP closes Na+ channel

-Na+ entry decreases, hyperpolarizing cell

rhabdomeric photoreceptor pathway

-11-cis-3-hydroxy absorbs light and isomerizes into all-trans 3-hydroxy retinal

-all-trans 3-hydroxy retinal dissociates from opsin

-activated opsin actives Gq protein

-activated Gq activates PLC, converting PIP3 into DAG and IP3

-DAG activates TRP cation channel

-Ca2+ and Na+ enter cell, depolarizing it

what do ciliary photoreceptors signal through?

Gi and transducin

what do rhabdomeric photoreceptors signal through?

Gq protein

why do muscle fibers of iris change pupil diameter?

this is done in response to light

what causes nocturnal animals to have eyes that "glow" in the dark?

reflective layer(tapetum lucidum) reflects and amplifies dim light

where does most refraction occur?

cornea

what does the most focusing?

cornea