Chapter 2: what is the nervous system's functional anatomy? (P2) Flashcards
what is the somatic Nervous system: transmitting information?
SNS
- monitored & controlled by the CNS
- in the PNS realm
- in charge of everything (needs to go to the spinal nerves = which is the SNS)
- has cranial nerves by the brain (movement and sensation)
- spinal nerves by the spinal cord segments
Cranial Nerves
- includes 12 nerve pairs – that control sensory/motor functions of the (head, neck, and internal organs)
functions
1. afferent functions
- incoming into the CNS
- sensory information & goes into the spinal cord to the brain
- efferent functions
- both functions **some might be in charge of both sensory aspects
what are cranial nerves?
- these are nerves coming out of the brainstem
**we can also take a look at all the nerves coming out of it
- olfactory
function = smell
–> sensory - optic
function = vision
**we can check the eye pressure, which can constrict the optic nerve
**if there’s a problem with the optic nerve we won’t be able to see
–> sensory - oculomotor
function = eye movement
- this can constrict the pupils
- the pupils splinter –> modulated by the oculomotor
–> motor - trochlear
function = eye movement
**these are the up and down movements of our eyes
–> motor - trigeminal
function =masticatory movements & facial sensations
**this is chewing & facial sensation
–> both (sensory + motor) - abducens
function = eye movement
–> motor - facial
function = facial movement & some taste sensation
**this is smiling and moving the eyebrows / taste sensation
–> both - auditory vestibular
function = hearing & balance
**hearing infection or vertigo
- the nerve is in charge of our balance
–> sensory - glossopharyngeal
function = tongue & pharynx movement & sensation
**mucus going down our throat = pharynx
–> both - vagus
function = heart, blood vessels, viscera, movement of larynx & pharynx
**cranial nerve important for the ANS
**In charge of heart rate, blood vessels
–> both - Spinal accessory
function = neck movement
–> motor - hypoglossal
function = tongue movement
–> motor
What are spinal nerves?
spinal cord
- inside bony spinal column made of small bones called = vertebrae
**this is part of our CNS
Vertebrae
- categorized into 5 anatomical regions
1. cervical = neck
2. Thoracic = upper mid back
3. lumbar = lower back
4. sacral = bottom of the spine
5. coccygeal = at the very bottom of the spine
body segments
- body segments corresponding to spinal cord segments = dermatomes (w sensory and motor nerves)
: sends info to the skin
: Dermatomes - if you have spinal cord damage (C7) –> you are likely not to move from the spinal cord down
**quadrapalegic –> can’t have sensation from the neck down (C7-C8)
- above the C7 can be dangerous (might not be able to breath without a ventilator)
- lumbar = motor commands will stop there
- anything from L2 down –> we can’t move and it’s not sensed by the brain
Ways which people find out they have dermatomes:
- shingles
- this is a type of herpes that makes people have lots of rashes (lots of connections between our nerves and skin)
- when our spinal cord is infected by shingles (will show up as a rash in the shape of a dermatome)
spinal cord segment
- interconnected so adjacent segments can operate together to direct complex coordinated movements
- motor movement/pertaining to the part of the body its sensing
- also have connections from one side to the other one
- complex motor movement that can happen due to the spinal cord
What are the SNS connections?
- the SNS = bilateral (2-sided)
nerve fibers
1. posterior
- dorsal in 4-legged animals
- fibers are afferent = they carry info from the body’s sensory receptors
**dorsal = sensory receptors & afferent
- Anterior root
- ventral in animals
- fibers are efferent = they carry info from the spinal cord to the muscles
**anterior (ventral) = motor commands - Law of bell and Magendie
- doesn’t change form person to person
describe the spinal nerve connections
1(a)
- fibers entering posterior root = bring sensory info from sensory receptors
**sensory neuron
**made of neurons
2(b)
- fibers leaving anterior root = carry motor info to the nucleus
**motor neuron
**sometimes sends directly to the motor neurons
- (c)
- collateral branches of sensory neurons may cross to other side/influence motor neurons there - (d)
- white-matter fiber tracts carry info to / from the brain
What is Bell Palsy?
- diagnosed by exclusion
- caused by inflammation of facial (7th) nerve
**probably by infection w virus or some other inflammatory agent
: one side will be successful, the other one will not bc of the inflammation in the 7th nerve
- 7th nerve travels through fallopian canal / becomes inflamed, swells, and stops nerve functioning
- 1 in 65 ppl = afflicted some time in their life
**most people fully recover –> few are profoundly affected - can completely damage the nerve itself and be paralyzed
EX: those who have TBI can impact the nerves
**usually the nerves are affected
EX2: whip-lash
**usually something not that serious (justin bieber had this)
what are the Autonomic and Enteric Nervous Systems: Visceral Relations?
- control of the viscera (internal organs) including:
- heart
- gut
- liver
- lungs
(all require complex neural systems) - ANS & ENS = hidden partners
- functioning in the background as CNS controls perceptions / behaviors - ANS & ENS interact w the CNS
**however, each has distinctive anatomy and functions
ANS
- in charge of a lot of things
- things that we usually can’t control (heart beat)
**both of the nervous systems can work together but also can work independently
What is the ANS: regulating internal functions?
ANS
- regulating internal functions (without conscious awareness)
- sympathetic division
- forms ipsilateral connections
- arouses the body for action
EX: increases heart rate & blood pressure) - mediates the fight or flight response
- in charge of arousing
- Parasympathetic division
- opposite of the sympathetic –> prepares the body to rest and digest
- reverses the fight or flight response
**both can be active at the same time
- can be separate but also on –> at the same time
- we can see if one’s more than the other (increase in heart rate)
Describe the ANS diagram figure
sympathetic ganglion
- groups of nerves together that serves a function
- the 2 ANS pathways exert opposing effects
- all fibers connect at “stops” –> this is formed by the ganglia from the CNS to target ANS organs
Left
- arousing sympathetic fibers that connect to chain of ganglia near the spinal cord
Right
- calming parasympathetic fibers that connect individual ganglia near target organs
What is the Enteric Nervous system: Controlling the Gut?
ENS
- network of neurons embedded in the lining of the gastrointestinal tract
What it controls:
1. bowel motility
2. secretion
3. blood flow to permit fluid & nutrient absorption
4. support waste elimination
**functions largely independently of the ANS
- brain & ENS connect through the ANS **especially through the vagus nerve
EX: helps out with the digestion aspect
**the ENS is sometimes called the “second brain”
- very complex
- lots of sensations by the microbiota
EX: people who have anxiety and depression
- they don’t have the same bacteria and organisms that are living in normal individuals **essentially the gut doesn’t work the same
Describe the Enteric Nervous System (ENS) *need to know this
ENS
- formed by network of neurons embedded in the lining of the gastrointestinal tract
- congregation of neurons form = ganglia
–> the ganglia then sends projections to the ANS and CNS (in part through the vagus nerve) = also known as cranial nerve 10 to control the gut
What is Microbiome?
ENS
- interacts with gut bacteria known collectively as = microbiome
: 3.9 x 10^13 microbiota populate the adult gut **that outnumbers the host cells by a factor of 1:3
: microbiota influences the nutrient absorption
ex: IBS
- we can take bacteria from someone whose healthy and put it into their own intestines
**the microbiota can be helpful for the intestines
: is the source of neurochemicals that regulate array of physiological/psychological processes
- this relationship inspired development of class of compounds known as psychobiotics
**live microorganisms used to treat behavioral disorders)
: micro can influence both CNS and ENS = leading to changes in behavior
EX: its important to know what we eat
–> we tend to eat things that have prebiotic (such as yogurt or fermented foods)
–> these microbiotas are in charge of keeping us healthy and our minds healthy and normal
What are the Ten Principles of Nervous system Function? (1)
neural circuits = series of neurons interconnected by synapses that subserve a function when activated
Sherrington & Adrian
- neuron = excitable cell
Monosynaptic cell
EX: Patellar
–> this goes directly to the dorsal root
(most of the things we do is monosynaptic)
Polysynaptic cell
What are the 10 principles of the Nervous system function? (2)
- sensory & motor division pervade the Nervous system
: segregation of sensory & motor functions exists throughout the nervous system
**described by the law of Bell and magendie that exists throughout the nervous system
- intrafusal muscle system
- groups of fibers that are really deep within the muscle
Main function
- sensory of the muscle functions and tendons
- Extrafusal muscle system
**does most of the work
- sensory & motor functions = divided in cortex in 2 ways
- separate sensory & motor cortical regions process particular set of sensory inputs
- entire cortex = organized around sensory & motor distinction
What are the 10 principles of nervous system function? (3)
- CNS functions on multiple levels
- is organized hierarchically and in parallel
: nature of the neural connectivity –> suggest the brain has both serial (or hierarchical) & parallel
circuitry
: unconnected regions **must have widely differing functions
–> this is bc not all cortical regions are connected to one another
- hierarchical circuit hooks up linear series of all regions concerned w a particular function
EX: vision
– in serial system: the info from the eyes goes to regions that detect simplest properties (such as color or brightness)
- this info is passed along to another region that determines shape –> then to another that measures movement
**and so on until at the most complex level the information is understood
**essentially, information flows sequentially from regions that make simpler discrimination –> to regions that make more complex discrimination in the hierarchy
Figure 2-34: Modules of Neural information Processing
A) simple hierarchical model of serial cortical processing
1. primary
2. secondary
3. tertiary
B) in distributed hierarchical processing model
–> each of several processing streams have multiple levels **areas at each level interconnect
Additional Notes
- although the brain has many serial connections –> many expected connections are missing
EX: visual system
- not all cortical regions are connected to one another
figure 2-34B
- shows the information flow in a distributed hierarchy
- although these multiple parallel pathways are connected to one another
–> those connections are more selective than connection in a purely serial circuit
What are the 10 principles of nervous system function? (4)
many brain circuits = crossed
- each hemisphere receives sensory stimulation from the opposite (contralateral) side of the body
**also controls muscles on the contralateral side
EX: most hemisphere will receive info from the opposite side of the body
**when we’re smelling from one nostril –> it will go into a separate region
**motor commands are contralateral
- A crossed nervous system have to join both sides of the perceptual world together
–> in order to do so: innumerable neural connections **links brain’s left & right sides
–> connecting cable = corpus callosum (200mill) nerve fibers join left/right cerebral hemispheres
**allowing them to interact
: 4 important exceptions to crossed-circuit principle:
- olfactory sensation & somatic
- autonomic
- enteric PNS connections
crossed organization
- explains why people who have a stroke or other damage to the left cerebral hemisphere –> have difficulty sensing stimulation to the right side of the body **or moving body parts on the right side
**also true for people whose stroke occurs in the right cerebral hemisphere
what are the 10 principles of the nervous system function? (5)
brain functions = localized & distributed
- Broca, wernicke/others demonstrated particular functions are = localized
EX: Broca
when damage occurs to ventroposterior region of the frontal lobes –> people are unable to produce spoken language
EX 2: Wernicke
- found that damage occurs to a different region
–> left posterior superior temporal gyrus pronounced deficits in language comprehension result
Result
- Broca/Wernicke showed that particular functions are localized
- some brain regions are prime importance to adults
**function is still being distributed, although its localized
- within a brain region –> function is among neurons that do the information processing
**if some neurons are destroyed –> remaining neurons can continue carrying out the function - only when majority of neurons within specific functional region = destroyed we see catastrophic failure of the associated function to occur
what is the 10 principles of the nervous system function? (6)
the brain is symmetrical/asymmetrical
- hemispheres look like mirror images –> some dissimilar features exist
: cortical asymmetry = essential for integrative tasks
(including language and body control)
EX: language
- if language zone existed in both hemispheres –> each connected to one side of the mouth (we would be able to talk out of both sides of our mouth at once)
**that would make talking awkward
solution
- locate language control of the mouth on one side of the brain –> orgaining the brain allows us to speak w a single voice
- language = typically situated on left side
–> spatial functions = right side - hemispheres have different functions although they look similar
EX: logic vs creative (this is the reason why the brain is asymmetrical
what are the 10 principles of the nervous system function? (7)
- the NS works by juxtaposing excitation & inhibition
: in addition to making movements
–> the brain also prevents
1. movements
- excitation (increased neural activity)
–> to produce some action - inhibition (decreased neural activity)
- to prevent other actions
EX: tourettes & Parkinsonism
: a brain injury in a region that initiates speech may render a person unable to talk (a loss of behavior)
Tourettes
- a person w an abnormality in a region that inhibits inappropriate language (swearing) **may be unable to inhibit this form of speech
**inhibition isn’t working properly
Parkinsons
- can have uncontrollable shaking of hands
**bc neural system that inhibits movements has failed
- often have difficulty initiating movements/ appear frozen bc they can’t generate excitation needed to produce deliberate movements
- juxtaposition of excitation & inhibition = central to the way the brain produces behavior **can also be seen at level of individual neurons
- All neurons evince a spontaneous activity rate –> can either increase (excitation) or decrease (inhibition)
what are the 10 principles of nervous system function? (8)
- the brain divides sensory input for object recognition & motor control
: sensory systems
- evolve 1st for influencing movement **before thing recognition
**2 separate processes
- visual information (in cortical circuit)
–> travels from eyes to thalamus to visual regions of the occipital lobe
–> from the occipital cortex (info then diverges along 2 separate pathways)
- ventral stream
- leads to temporal lobe for object identification
ventral stream injuries
- blind for object recognition
**cannot distinguish a cup from a spoon
**however, they can shape their hands correctly when being asked to reach for an object they can’t identify
- dorsal stream
- which goes to the parietal love to guide movements relative to objects
dorsal stream injuries
- can recognize objects –> but can be clumsy in reaching movements bc they don’t know the correct form for hand postures until they contact objects
- important implications for understanding brain organization
3 important implications
1. dorsal/ventral visual systems = exemplify parallel information processing in the brain
- we might think we’re aware of our entire sensory world **sensory analysis required for some movements = not conscious
- unconscious/conscious brain processing underlies important difference in our cognitive functions
**unconscious movement system
- always acting in present
- in response to ongoing sensory input
**conscious object recognition system
- allows us to escape present / bring to bear info from the past (forming neural basis of enduring memory)
what are the 10 principles of the nervous system function? (9)
- the NS produces movement in perceptual world the brain constructs
EX; relation to sensations, memories, and myriad other forces/factors
: individual realities –> both between/ within species = are mere approximations of what is actually present
EX: we only have 3 primary colours that make up our perception vs the rainbow shrimp that has many color receptors than us
: the brain of individuals develops in a particular set of environmental circumstances on a plan common to that species
**the behavior the brain produces is directly related to the world that the brain has constructed
what are the 10 principles of the nervous system function? (10)
neuroplasticity = hallmark of nervous system functioning
- experience alters the brain’s organization –> neuroplasticity = required for memory & learning
- neural connection changes = required for information storage
**forgetting = due to loss of memory connections - plasticity can be beneficial
- recovery from brain injuries/diseases
- normal aging
