quiz 6 (section 2 quiz 3) Flashcards
which of the following are true about smooth muscle?
smooth muscle is typically innervated by the autonomic nervous system
which of the following are true for both skeletal and smooth muscle?
both types of muscles contract by the sliding filament mechanism
contraction is initiated by the binding of calcium to troponin in both types of muscle
which of the following are true about the nervous system?
the organs of the body, such as the lungs and stomach, are innervated by both the sympathetic and parasympathetic nerves
which of the following are true about synapses in the central nervous system?
the amount of neurotransmitter released at one synapse is typically not sufficient to elicit an action potential in the post synaptic neuron.
acetylcholine is a small molecule rapidly acting neurotransmitter.
which of the following are true about neuronal circuits?
a signal entering as an input to a circuit with amplifying divergence will be spread to a larger number of neurons.
reciprocal inhibition circuits are important for controlling antagonistic pairs of muscles
which of the following are true about sensory receptors?
as the amplitude of the receptor potential increases, the rate of action potentials sent down the neuron toward the central nervous system increases.
accommodation is one mechanism through which receptor adaption can occur.
activation of a G protein
metabotropic
opening and closing of sodium channels within one millisecond
ionotropic
sustained opening of a potassium channel for several hours
metabotropic
increase production of membrane receptor proteins
metabotropic
activation of gene transcription
metabotropic
muscle action potential
one peak
action potential with plateau
one peak with flatter top
slow wave rhythm with self excitation
two points at top of one peak. bottom looks like start and end of action potential curve
receptor potential with excitation
exponential increase (CC down) with lots of little peaks at the tops
inhibitory post synaptic potential
graph looks like a bowl. goes down once rather than up
neuron
functional unit of the nervous system
dendrites
receive input
soma
the cell body
axon
sends the output
axon hillock
site of initiation of action potential
axon terminals
interface between axon of presynaptic neuron and dendrites of postsynaptic neuron
motor neuron
-sends input to muscles
-efferent (away)
-myelinated and larger diameter
sensory neuron
-sends sensory information to central nervous system
-afferent (toward)
-pseudo-unipolar cells: axon extends in two directions from cell body. one branch goes to skin receptors the other to the spinal cord.
-no dendrites
-myelinated or unmyelinated
-signals only sent in one direction
multipolar-interneuron (CNS neuron)
-process information and transmits it to other neurons
-highly branched
-lots of dendrites. can receive input from 10,000 to 200,000 input neurons
central nervous system
brain and spinal cord
peripheral nervous system
autonomic and somatic nervous systems
autonomic NS
sympathetic division
parasympathetic division
somatic NS
sensory (afferent) NS (sensory input) and motor (efferent) NS (motor output)
spinal cord
transmission of signals; control of autonomic and instantaneous actions
subcortical structures
lower brain. control of subconscious processes and processes required to sustain life
cortex
higher brain. control of complpex processes and processes that require conscious thought
gray matter
contains all of the living cell bodies.
white matter
axons of passage. white bc more myelinated
spinal roots
start of the peripheral nerves. sensory root is dorsal and motor root is ventral
sensory (afferent) roots
dorsal root ganglion: contains the cell bodies of the sensory neurons. input of sensory information to spinal cord
motor (efferent) roots
motor axons carry signals away from spinal cord to muscles/glands. cell bodies in the grey matter of the spinal cord
brainstem
controls critical life processes
medulla
controls respiration; regulates cardiac and vascular function; regulates reflexes such as coughing, sneezing, swallowing, vomiting
pons
regulates sleep-wake cycle and breathing; junction for cranial nerves
midbrain
regulates eye movement
cerebellum
controls coordination, precision, and timing of movements. also involved in balance control
limbic system
regulates emotion, behavior, and memory
hippocampus
long term memory storage and spatial navigation
amygdala
regulates emotions, reward processing with motivation, association of emotion with memories
hypothalamus
control center for maintaining homeostasis - regulates food/fluid intake, sleeping, metabolism, body temp
basal ganglia
initiating voluntary movement, fine tuning motor function
thalamus
relays sensory and motor information between brainstem and cortex
frontal lobe
decision making, problem solving, planning, attention, speech, production, voluntary movement, personality
parietal lobe
somatosensory processing, spatial processing, sensory integration
occipital lobe
visual processing, interpretation, recognition
temporal lobe
auditory processing, language comprehension, memory
somatic peripheral NS
sends signals from sensory receptors and to peripheral effectors
sensory receptors
specialized cells that transduce a physical stimulus from the environment (or from within the body) into neural signals
types of sensory receptors:
-vision: retina in the eye
-hearing: hair cells in the cochlea in the inner ear
-touch: mechanoreceptors in the skin
-olfaction (small): olfactory nerve endings in the nose
-taste: taste cells on the tongue
effectors
perform the functions/activities of the body.
-contraction of skeletal muscles (somatic NS)
-contraction of smooth muscles (autonomic NS)
-secretion by exocrine and endocrine glands (autonomic NS)
autonomic NS
innervate many organs of the body to enable life processes
-neurons are lightly myelinated or unmyelinated
-two neuron chain from spinal cord to organ: preganglionic neuron and postanglionic neuron
-ganglia
ganglia
locations of cell bodies of the postganglionic neurons
sympathetic NS
fight or flight
-raises heart rate, promoytes vasoconstriction, releases glucose, inhibits digestion
-symapthetic nerves originate from thoracic and lumbar regions of spinal cord
-sympathetic ganglion chain
sympathetic ganglion chain
ganglia reside near spinal cord
parasympathetic NS
rest or digest
-promotes digestion of food, expulsion of waste, general maintenance of the body
-parasympathetic nerves originate from Brian and sacral region of spinal cord
ganglia reside in the effector organs
dual innervation
both sympathetic and parasympathetic nerves innervate most organs, but will have opposite effects
synapses:
junction between one neurons and the next
-transmit signals between neurons
-process information
how do synapses process information?
-send signals from one neuron to the next or from one brain region to another
-block transmission of a signal from one neuron to the next
-spread a signal to many neurons
-change a single neural impulse into repetitive impulses (or vise versa)
-integrate pulses across multiple neurons to cause highly intricate patterns of impulses in successive neurons
integrative function of synapses
routing info, selecting relevant info, and processing info to create appropriate mental and motor responses
long term potentiation
process through which a sequence of synapses increases its capability to transmit a specific signal due to repeated transmission of the signal
-synapses become so facilitated/strengthened that the impulses can be transmitted even without a sensory input
-basis of memory formation
-occurs in the cerebral cortex
chemical synapses
-neurotransmitters: traverse the synaptic space form the presynaptic to postsynaptic neuron.
-one way conduction (pre-post)
-involved in neuron to neuron or neuron to muscle communitcation
electrical synapses
-gap junctions: allow free movement of ions from one cell to another
-bidirectional conduction
-involved in coordinating activity among large groups of interconnected neruons
presynaptic terminals
portion of the presynaptic axon that is in close association with the dendrites of the postsynaptic neuron
-transmitter vesicles: stores neurontransmitter for eventual release
-mitochondria: produces energy to synthesize more neurotransmitters
neurotransmitter release process:
-action potentials reaching the terminal open voltage gated Ca+2 channels.
-influx of Ca+2 ions enables vesicles to release their stored neurotransmitter at release sites
-quantity of neurotransmitter released is directly related to the number of Ca+2 ions that enter
small molecule rapidly acting transmitters (acetylcholine, nonepinepherine)
-synthesized in cytosol of presynaptic terminal, tansported into vesicles in the axon terminal
-vesicles and/or transmitter precursors are recycled
-release and action on postsynaptic cell occurs within millisecond or less
neuropeptodes
insulin, gastrin. larger. synthesized by ribosomes.
-axonal streaming: vesicles travel from cell body to axon terminals very slowly.
released in smalll quantities, long term changes to postsynaptic cell
gaseous molecules
NO, CO.
synthesized immediately. diffuses out of axon terminal over a few seconds
acetylcholine
exicitory.
released by motor neurons, proganglionic neurons of autonomic NS, most postganglionic neurons
norepinephrine
excitatory or inhibitory.
released by brain stem and hypothalamus, postganglionic neurons of sympatheic NS
dopamine
inhibitory. released by sustained nigra and basal ganglia
GABA
primary inhibitory neurotransmitter. released in spinal cord, cerebellum, basal ganglia, cortex
glutamate
always ecitatory. released by sensory neruons entering CNS
serotonin
inhinitor of pain pathways. releaased in brain stem
ionotropic receptors
neurotransmitter receptors that directly gate ion channels. allows for very rapid control of postsynaptic neurons. typical receptor for small molecular transmitters
metabotropic receptors
neurotransmitter receptors that activate second messenger systems. allows for prolonged excitation or inhibition of the postsynaptic neuron. important for changing th elong term response characteristics of different neuronal pathways
second messengers:
increase or decrease specific cellular functions. most important mechanism is by changing gene transcription. leads to changes in cell structure or metabolism through formation of new proteins.
primary mechanism of excitation:
opening of sodium channels
primary mechanism of inhibition:
opening of chloride ion channels
excitatory postsynaptic potential (EPSP)
binding to an excitatory receptor increases sodium permeability, leading to an increase in membrane potential
inhibitory postsynaptic potential (IPSP)
binding to an inhibitory receptor increases chloride permeability, leading to a decrease in membrane potential (can also increase potassium permeability)
electrotonic conduction
direct spread of electrical current by ion conduction in the intracellular fluid of the dendrites. NOT action potential. most dendrites have few voltage gated sodium channels so cannot transmit action potentials
decremental conduction
decrease in membrane potential as the EPSP/IPSP spreads electrotonically along dendrites towards the soma. large part of the PSP is lost by leakage through the membrane before it can rwach the soma
many voltage gated sodium channels in the axon hillock and axon so action potential can self regenerate here
few voltage gated sodium channels in the soma/dendrites so AP cannot self regenerate here
action potential travels:
down the axon
spatial summation
summing simultaneous postsynaptic potentials across multiple axon terminals
temproal summation
summing successive discharges from a single presynaptic neuron
skeletal muscle
striated, tubular, multi nucleated, voluntary, attatched to skeleton
smooth muscle
non striated, branched and uninecleated, involuntary, covering walls of internal organs, organized in sheets
cardiac muscle
striated, branched and uninucleated, involuntary, covering the walls of the heart
smooth muscle orgasn
digestive system
urinary system
circulatory system
respiratory system
sensory system (eye)
which muscles contract (shorten the muscle)
skeletal and smooth
contratcion is mediated by actin myosin interactions.
myosin heads form cross bridges by binding to actin. mysoin walks along actin causing filament slidin
how is contraction initiated?
increase in intracellular calcium ions
what provides energy for contratcion?
ATP hydrolysis
what are the striations in skeletal and cardiac muscle?
sacromeres
side polar arrangement of smooth muscle
myosin heads on one side of the myosin filament hinge in one direction, and those on the other side hinge in the other direction
dense bodies
anchor point for actin filaments. similar to Z disk. some attatched to cell membrane, other dispressed throughout the cell. connection points between adjacent muscle cells allow for transmission of contractile force between cells
stress relaxation response
ability to return to the original force of contraction seconds to minutes after the smooth muscle has been stretched
caveolae
small invaginations in cell membrane, similar to T-tubules in function
most calcium ions enter the cell from the
extracellular fluid. slow process, diffusion over long distances
calmodulin
regulatory protein that initiates contraction by activating the mysoin cross-bridges
calium pump
pumps calcium ions out of the muscle fiber and back into the extracellular space. requires ATP. slower acting pump than SERCA in skeletal muscles
myosin phosphate
enzyme that splits the phosphate from the regulatory light chain of the myosin head.
latch mechanism
long term maintenance of smooth muscle force for hours without much expenditure of energy
stimuli to control contraction
neural signals, hormonal stimulation, stretch of the muscle, local tissue chemical factors
unitary
single unit, visceral, syncytial. hundereds to thousands of smooth muscle dfibers that contract together as a signle unit. control is mainly by non nervous stimuli
multi unit smooth muscle
each fiber operates independently. control is mainly by neural signals
varicosities
neurotransmitter filled bulges along the length of the axon
diffuse junctions
type of synaptic connection in smooth muscle
if a smooth muscle cell is excited by acetlycholine,
it will be inhibited by norepineephrine (and vise versa)
does excitation of an action potential in the muscle cell of smooth muscle need to occur for contraction to occur?
no
spike potentials
typical action potential, 10-50 ms duration
action potentials with plateaus
rapid depolarization, but repolarization is delayed up to 1 second
self excitatory action potentials associated with a slow wave rythm
slow wave: rythmic fluctuations in membrane potential
muscle streatch AP
rasies membrane potential making it more likely for a slow wave tot rigger an AP
neuronal pool
neural circuit. group of neurons that processes signals in a unique way
input neurons
each input neuron branches to form thousands of terminals which synapse with various neurons in the pool
stimulatory field
the neuronal area stimulated by each incoming nerve fiber
excitatory/suparthreshold stimulus
signal from an input neuron is sufficiet to elicit an action potential in an output neuron
subthreshold stimulus
signal from an input neuron increases membrane potential in an output neuron, but is not sufficient to elicit an action potential
discharge zone
all neurons in this zone receive sufficient input to trigger action potentials
facilitated zone
neurons in this zone receive excitatory input, but not sufficient to elicit action potentials
inhibitory zone
neurons in this zone receive inhibitory input, impeding the formation of action potentials
divergence
when a small number of weak signals entering the neuronal pool lead to excitation of many neurons leaving the pool.
amplifying divergence and divergence into multiple tracts
convergence
signals from multiple inputs unite to excite a single neuron. convergence from a single source or multiple sources
reciprical inhibition circuit
incoming signal to a neuronal pool causes an excitatory signal in one direction and a simultaneous inhibitory signal in another direction
after discharge
neural firing that lasts longer than the incoming signal
synaptic afterdischarge
prolonged firing of an output neuron due to prolonged elevation of membrane potential due to long acting neurotransmitters
reverberatory (oscillatory) circuit
positive feedback within tghe neuronal circuit back to re-excite the input of the same circuit
continuous signal output
when a pool of neurons continuously proceeds signals even in the absence of input
inhibitory circuits
prevent excessive spread of signals
synaptic fatigue
synaptic transmission becomes progressively weaker the more prolonged or more intense the excitation stimulus
synaptic sensitivity
how readily a synapse transmits signals
sensory receptors
specialized cells that transduce a physical stimulus from the enviornment (or from within the body) into neural signals
effectors
perform the functions/activities of the body
contraction of skeletal muscles
somatic nervous system
contraction of smooth msucles
autonomic NS
secretion by exocrine and endocrine glands
autonomic NS
mechanoreceptors
transduce mechanical stimuli (pressure, vibration, stretching)
thermoreceptors
transduce temperature
nociceptors
pain receptors detect physical or chemical damage to the body
electromagnetic (photoreceptors) receptors
transduce light
chemoreceptors
transduce chemical stimuli (taste, smell, blood oxygen, osmolality of body fluids)
differential sensitivity
each type of sensory receptor is highly sensitive to one type of stimulus but unresponsive to other types of sensory stimuli
receptor potential
change in membrane potential due to incoming sensory stimulus. graded potentials
receptor adaption
decrease in response of a receptor over time due to a continuous prolonged stimulus
slowly adapting receptors
detect continuous stimulus strength (tonic receptors). keeps the brain up to date on current state of the body
rapidly adapting receptors
detect changes in stimulus strength (rate receptors).
labelled line hypothesis
each neuron transmits information only about one modality of stimulus
receptive fields
area of the skin where a stimulus will excite the nerve fiber. fields overlap. each neuron branches to several terminals
innervation density
number of neurons supplying a region of the skin, per unit area
