Exam 6: February 20-24 Flashcards
what are the opposite impacts that the sympathetic and parasympathetic systems have?
opposites
they’re part of the autonomic branch of the efferent PNS
pupils: dilate vs. contract
cardiac output: increase vs. decrease
bronchiole: relax vs. contract
digestive activity: increase vs. decrease
what is another name for the PNS?
sensory nervous system
what is the function of the sensory nervous system?
to detect and relay information to the CNS
PNS is the eyes and the ears for our CNS - the CNS Is encased in bone so it’s very isolated so needs info to be brought to it
need to also look at what’s happening inside your body as well as outside of your body! you were generating heat and were cool on the way to class but because you were working those muscles and doing equation 2 more to generate heat, when you got here and were in a warmer environment you get hot because of the internal heat you generated
what part of the reflex template is our sensory nervous system?
the first part!
we have a stimulus being detected by a receptor and our afferent system is taking the info to our CNS
what is a stimulus?
a detectable change
what are modalities? what are examples?
we only detect certain things in certain ranges
modalities are the things that our body actually pays attention to and has receptors for and can register changes in
ex. heat, light, pressure, temperatures, chemicals
other things in the environment could be detected – we don’t register the same things as other organisms – we can’t detect changes in CO in our environment
how does our sensory nervous system detect changes?
via receptors but within limits
the receptors won’t be able to detect all changes, just sufficient amounts = adequate
you either have a modality for something or you don’t but then within that modality you have a range of adequacy
what kinds of receptors does our sensory nervous system have?
1) photoreceptors
2) mechanoreceptors
3) thermoreceptors,
4) osmoreceptors
5) chemoreceptors
6) nociceptors
what are photoreceptors?
register light
what are mechanoreceptors?
register pressure and stretch
what are thermoreceptors?
register heat and cold
what are osmoreceptors?
register changes in concentration of solutes in the ECF
what are chemoreceptors?
register changes in a specific compound like Na or Ca
what are nociceptors?
detect tissue damage by cutting open or heating cells
what are the types of receptor design in the sensory nervous system?
1) directly by afferent neuron
2) receptor cell to afferent neuron
what does a receptor design that is directly by afferent neuron in the sensory nervous system entail?
our afferent neuron is acting as the receptor and as the afferent pathway
what does a receptor design that is receptor cell to afferent neuron in the sensory nervous system entail?
a separate cell is the receptor cell and then the afferent neuron takes the information from it so it’s just acting as the afferent pathway here
what type of receptor design in the sensory nervous system is faster?
directly by afferent neuron
what receptor design is typically seen in the sensory nervous system?
receptor cell to afferent neuron due to trade offs
when we try to make the afferent neuron do different things and be capable of registering very specific stimuli and not other ones, we’re asking it to do two very different things at the same time
when there’s a separate receptor cell they can do their individual jobs better even though that takes a little more time you get more precise information
however, where speed is important our system will use a receptor that is directly by afferent neuron
what is sensory transduction?
taking a change in our environment and changing it into something our CNS can interpret
key information is turned into a code for the CNS so that it knows what it is that changed, how much it changed, and where that change is
location is important so you know to go away from a fire for example
what is signal transduction?
taking a chemical in our body and turning it into response in the cell
different from sensory transduction!
what are the components of sensory transduction?
intensity and location
what is the intensity coding component of sensory transduction?
you start with a variable stimuli which is just different stimuli of different amounts
the stimuli are registered by a receptor and them changed into a graded potential → a smaller stimulus gives us a smaller graded potential
graded potentials decrease with distance so they won’t go all the way to the brain so if the graded potential is big enough, it triggers an AP
the AP triggers the exocytosis of neurotransmitters where the afferent talks to the interneurons in our CNS
brain registers numbers of NTs
what is the relationship between graded potentials and AP in relation to intensity coding?
when a stimulus is changing into a graded potential, it doesn’t stay as a graded potential because they decrease with distance and wouldn’t be able to get all the way to the brain
our neuron is an excitable cell that can help us travel distance because they are capable of action potentials!
if the graded potential is large enough to be a threshold potential, it will trigger an action potential
the number of AP made is based on the size of the graded potential aka how long the graded potential can stay above the threshold potential to trigger more AP
a bigger stimulus gets a larger graded potential which gets us a higher frequency of AP
what do AP do in relation to intensity coding?
graded potentials get changed into a certain number of AP so there’s a variable AP pattern but not variable amplitude
why do we want AP? Because at the end, AP trigger exocytosis of neurotransmitter where the afferent talks to the interneurons in our CNS
fewer AP causes the release of fewer NTs, while more AP get us more NT release
what does your brain register in terms of intensity coding from the PNS?
a higher frequency of AP causes the release of more neurotransmitters
in the end your brain doesn’t see the stimulus or the graded potential or the AP, it only sees number of neurotransmitters which translates to the intensity
more NT means higher intensity signal
what are receptor potentials?
receptor potentials are just graded potentials happening in our receptor areas
what is the summary of intensity coding in the PNS?
bigger stimulus gets us bigger AP frequency moving along the axons which is going to get us a bigger number of neurotransmitters which is what the brain is registering
can you feel pain without even touching your PNS?
yes!
Bronson can make you feel intense pain without even touching you your PNS by going into your CNS and flood the appropriate synapse with the appropriate NT so that your brain thinks your in pain even though there’s nothing happening to your pinky finger
when NTs breakdown it results in a bigger response
what are the three parts of location coding?
1) which specific receptor is sending the information
2) receptive field
3) lateral inhibition
how does which specific receptor is sending information play a role in location coding?
different receptors go to different parts of our CNS
axon is like a direct wire connection
this is why neurovascular surgeons need to be careful when connecting things up so they don’t connect axons wrong
modality of information so what is it that we’re gathering information about (cerebral cortex of cerebrum)
how does receptive field play a role in location coding?
area covered by the axon terminal
this coverage activated and send a message about whether one thing are impacting receptive field or if multiple are – it’ll combine them all up and get sent as one message
is a smaller or larger receptive field better?
a smaller is better because a smaller receptive field helps us localize wherever this point is better than a bigger receptive field
inverse relationship between receptive field and localization ability
helps us with sensitivity and discrimination because bigger receptive field lumps the two touches as one and you can’t discriminate that there’s two touches but smaller receptive field will get two message and will know there’s two spots being touched so it’s more sensitive so this is important for our hands (unlike our back)
overlap of receptive fields is possible kind of like a venn diagram so then a stimuli hitting in one circle of the diagram, the brain will know that it’s just coming from part A and it will eliminate the overlap area or else it would be getting signals from A and B so overlap helps with localization
how does lateral inhibition play a role in location coding?
sharpens contrast
causes the biggest thing to get attention
this is because of a job that our afferent neurons have – their first job is take the message back to the CNS
our afferents also inhibit their neighbors – it’s like something really cool is happening a ways away and a bunch of people are running to get there; how do you make sure you get there faster? Inhibit them – this inhibitory job is directly related to the first job in strength – the stronger the intensity of the message that is being sent to the brain, the stronger it’s going to inhibit its neighbors
what are the consequences of lateral inhibition?
not everyone sends the same level of message to the brain – everybody in the area of the signal ends up being inhibited = all ANs inhibited
if we can lower some that they just go away we can focus on the main area and narrow down the area of the signal
there’s a direct relationship between how much they can inhibit and how much of the message they can send back
the ones on the edge that aren’t sending as much of a message aren’t going to inhibit the big message but the ones on the side that aren’t sending the messages are getting inhibited a lot by the big one
what our brain sees is a reduction of the big one and an elimination of the ones on the side which helps us with location
what are alternate uses of lateral inhibition?
decrease pain and itch – you rub the area that you bumped and it eliminates your pain
what you’re doing is rubbing the side areas so they start sending messages and therefore further reducing the transmission
you use your efferent skeletal part to activate the lateral part if you don’t want the signal to come through
increasing the activity of the neighbors around the itch area so that their activity goes up and their ability to suppress what’s happening in the middle area increases
we’re activating this process from the efferent side but the process happens in the afferent pathway
what is the pathway for the sensory nervous system?
afferent neurons carry message into CNS which passes it to spinal cord → brain stem → thalamus → cerebral cortex
there are times where the thalamus takes over the activity and get to do movements as a result of the information coming in
what happens to the information when it comes into the cerebral cortex?
there’s a crossing over when the information coms into the cerebral cortex = information coming in from your left hand goes to the right side of the brain
where does information go when it gets to the cerebral cortex?
within the cerebral cortex, there are specific processing centers
the information coming from your ears, eyes, touch go to different areas
can the pathway from the PNS to the CNS be interrupted? why would this happen if it’s how the brain gets info from the outside?
We create mechanical lateral inhibition as an efferent process to change the afferent input coming in
another way is inhibitory efferent neurons who’s job is to reduce or prevent the afferent neurons from sending messages to the brain
this is because your brain is getting bombarded with afferent information so your brain can do some reduction later on but sometimes it activates the efferents in that area to suppress the afferents – you can’t feel that you have clothes on and that they’re rubbing against you
what are the parts of the sensory NS?
1) somatosensory
2) visual
3) auditory
4) vestibular
what information does the somatosensory system provide?
gives information from your skin, muscles, joints, bones, and tendons
it’s also our proprioception
what is a tendon?
connects muscle to bond
what is proprioception?
somatosensory is our sense of touch but it’s also our proprioception system which helps our brain determine where our body is in space (we can close our eyes and touch our nose with our fingers
what receptors does our somatosensory system use?
this system is just used in our afferent neurons
this system has our afferent neurons gathering information which is the faster system but the reason we don’t use just this system in the rest of our body is because it has limited modifications, you can’t get too detailed of information from it
can you adjust the receptors of the somatosensory?
somatosensory system is only used in our afferent neurons
we can make adjustments to these afferents so they respond to certain modalities
you can turn the afferents into thermoreceptors for heat, mechanoreceptors for pressure, nociceptors
why would you give up more detailed information from your somatosensory system?
Why do we want these senses to be on our faster system?
Because we need this information to react to it
you’re going to feel a mosquito land on you faster than you’ll hear or see it
where is the somatosensory system spatially positioned in the brain?
all this information coming from our skin, bones, tendons comes up to this same spot in the brain - in doing so it comes up in an ordered pattern relative to where it is in the body
however this information gets distorted because there’s a lot more information coming in from our hands than our elbow = cortical projection
what is cortical projection? can it be changed?
homonuculus which means little man
this picture of yourself can be changed but it’s limited – you can get more information or more sensitivity from say your forearm and expand this area a little bit but that means something else will lose space
what happens to cortical projection for people that have lost a limb?
they’ve lost axon parts but they still have the rest of the afferent going in – they still have an area of the brain dedicated to that
sometimes we can activate things on those axons even though it’s not from the original axon terminal and the brain translates it as if it was coming from the original axon
what is the information that the visual component of the sensory nervous system gives?
electromagnetic waves in the environment that we’re registering aka photons/energy waves
light is one category of electromagnetic waves - receptors have limitations so that’s why we don’t pick on IR or x-rays, we only pick up on the visual spectrum
what can photons do?
change the shape of proteins
what receptors does the visual component of the sensory NS use?
photoreceptors
sensitive to particular amounts of energy that hit them and then they respond
what are the components of the visual component of the sensory nervous program?
cornea and lens and retina
what do the cornea and lent do?
focus energy waves that are coming in right to the receptor
why do people need glasses?
it’s because the shape of their eyeball doesn’t match what their cornea and lens are doing
either the eyeball is too long or too wide
what is the retina?
the back of your eye that has the receptors in it
what does the retina do?
this is where we transform the energy units into something the brain will understand
light comes in and hits some cells first but the receptors are actually all the way in the back
where are the afferent neurons located in the eye?
afferent neurons are in the front and are hit by the energy units first but they can’t respond to them, they dissipate some of the energy before it gets to the receptors
yes we lose some of the capacity to see things however we do things in a bright environment so it’s okay to have a little bit of shading
what do animals have in their eyes to make sure they see the most?
cats and dogs have extra reflectors in the back to make sure they pick up light while other animals have receptors in the front and afferents in the back
what is a blind spot?
afferent neurons need to take the information to the brain but when we need to send afferent neurons out, we can’t have two things in one place so where the axons are going out and blood supply is going in and out, we can’t have receptors so we can’t see in that field of our eye which is referred to as our blind spot
your blind spot is your brains best guess of what’s supposed to be there – you don’t see your blind spot
what is the path of visual information?
information goes to receptors in the back of the eye, then turns around goes to the front to the afferent neurons then turns back around and goes to the brain and the visual cortex
how do we make the picture in front of us that we’re seeing?
encoding by our retina
what are the two parts of the retina that encode?
rods and cones
rods and cones are supposed to b registering the energy waves that hit them
what are rods? what shape are they? what color do they pick up on?
cylindrical shaped
register shades of grey
they’re bigger so if you only have a few energy waves coming in, the bigger rods are more likely to have the energy hit them
rods are more sensitive and more likely to pick up on electromagnetic waves coming in because they’re bigger
what are cones? what shape are they? what color do they pick up on?
cones are pointy and less sensitive because they’re smaller so they don’t pick up as much since it’s harder to energy to hit them
they register color vision
if you take away your cones, you’ll still be able to see but only in shades of grey
