NERVOUS SYSTEM - LECTURE 1 Flashcards
What occurs before Parkinson’s
6-10 years before being diagnosed for Parkinson’s disease or a memory disorder (Alzheimer disease), they would have already lost their sense of smell
This is because the only set of neurons (olfactory neurons) that are directly exposed to the outside world is in the roof of the nose
Basics of the brain
Structure:
- ~1400 grams,
- Largely made up of fat - the fattiest organ in the body
- ~160 billion neurons
- The many neurons develop very specifically to ensure they are connected properly, produce the correct neurotransmitter and at the right time
- Arguably the most complex thing in nature
Function:
- It allows us to do everything we can do as humans
- It is likely the most ‘faithful’ organ in the human body
What is a nerve fibre
Note that a nerve fibre is the same as an axon
Location and function of the primitive part of the brain
The primitive section of the brain (the underneath side), is for primitive functions - smelling, mating, food finding
Location and function of the newer part of the brain
The newer/front part of the brain is for voluntary movement, coordination and higher-order thinking
Rat brain structure
- Surface of the forebrain brain is smooth/few wrinkles
- The cerebellum has some small folia
- The primitive section (the underneath side), is decently large in proportion
- The newer/front part of the brain is small (but still larger than the primitive side)
Why would a brain be smooth
The brain (e.g. of a rat) is smooth if the cells can fit without adding additional spaces
Describe the structure and purpose of Gyri and sulci
Gyri = ridges in the cerebral surface/cortex
Sulci = Grooves/valleys in the cerebral surface/cortex
Gyri and sulci exist to allow for more neurons to fit into a smaller area
Note: cerebrum = the lobes, & cerebral cortex = surface of cerebrum
Describe the folia
Folia are ridges of the cerebellum
Cat brain structure:
- Very distinct Gyri and Sulci
- In particular: Long Gyri that make up the forebrain that allow the cat to sense and also move body position according to senses
- Lobar divisions
- Cerebellum has many folia
- The primitive section of the brain takes up less
- The lobes, particularly the frontal cortex becomes bigger
Baboon brain Structure
- Gyri and sulci still distinct
- Gyri start to fold down
- Lobes are more defined - particularly the frontal lobe
- Primitive part of the brain is of a smaller proportion
- Cortex of the brain is larger
**** (the more cortex/over the top, it is meant to mean increased rational thinking and decision making, although due to different languages of the species this isn’t confirmed)
Human brain Basics
- Very complex and defined gyri
- Number of gyri is increased (increased neurons)
- Sulci also more defined
- Lobes become very clearly defined
- The primitive part of the brain is very small
- The frontal cortex is very large (defines us as humans)
Extra:
The olfactory bulb is a small structure in the brain (it can be seen from the bottom of the brain, located anteriorly on the right hemisphere), where several diseases start in the brain
What differentiates the structure of different species brains:
When we look at the structure of the brain, it is the cortical structure that differentiate species (particularly humans - it is what makes it so complex)
Due to the complexity of the brain and the lifespan of humans, we suffer from diseases in the brain (unlike most other species)
How can the brain be divided
The brain can be divided into a number of different ways, e.g. by:
Hemispheres: Left and right
Lobes: Frontal, parietal, temporal, occipital
Forebrain, midbrain, hindbrain
Functions
Cell types (and neurotransmitters released)
What is the central sulcus
A groove that divides the brain into a front and back half (ends before the btoom of the brain)
What is the preoccipital notch
A notch on the inferior of the brain that marks the division between the very back of the brain from the middle of the brain
What is the parieto occipital sulcas
The sulcas/groove that actually divides the very back of the brain from the middle of the brain (it is very hard to see in the lateral view - easier to see with a medial view of the brain)
What is the lateral sulcus/Sylvian fissure
A fissure (as crack/divide) that runs from roughly the bottom of the central sulcus (near the middle of the brain) to roughly the middle of the parietoocciptal sulcus, which separates the middle section of the brain into the parietal lobe (superior) and the temporal lobe (inferior)
What is the frontal lobe
The section of the brain in front of the central sulcas
It includes the precentral gyrus, the premotor cortex (including Exener’s and Broca’s area), and the frontal association cortex)
What is the precentral Gyrus
The gyrus in front of the central sulcus, which is often referred to as the primary motor cortex. This is because inside this cortex are many of the large motor neurons (neurons that control movement) that project their axon to the spinal chord (which will then communicate to the muscle) to control movement.
WIthin the primary motor cortex there is a map of what the body looks like that tells us what the body looks like and tells us where the neurons are that control certain functions in the periphery.
Starting from the bottom there is the neck, lips and face, nose, throat, eyes, hand, back. hips, legs - onto the medial aspect of the brain. Stimulating different areas causes movement of specific areas. This is called the homonculus or ‘body map’.
Therefore this regions is what executes motor movement.
What is the promoter cortex
The section of the frontal lobe that is in front of the precentral gyrus.
It is also referred to as the planning part of the cortex and also has a homuncular representation like the precentral gyrus. When we make movements there is both a planning and execution phase - therefore the planning areas are really important. The planning areas are very close/alligned with the execution areas corresponding with the parts of the body
What is included in the premotor cortex
Broca’s area and area within the premotor cortex that is responsible for planning controlling movement of mouth, lips, and throat for vocalisation.
Above Broca’s area there is an area responsible for planning the movement of the eyes
area is another area of the premotor cortex that is above the area that lans the movement of the eyes and it is responsible for the planning of the movement of the hands.
What is the frontal association cortex
The anterior section of the frontal lobe that is generally associated with (we don’t know much about it):
Cogntivie function
Intelligence
Mood
Personality
Behavior
What is the temporal lobe
Section of the middle part of the brain inferior to the lateral/sylvian fissure (all that fits between the central sulcus, parietoocipital sulcus, and belowthe lateral fissure)
It includes the primary auditory complex, the Wernicke’s area, and the temporal association cortex
What is the primary auditory cortex
The section of the brain under the lateral fissure that takes the sounds that come through the tempanic membrane (ear drum) and the cochlear and into the brain, and divides/breaks it down into the time and tone of the sound.
What is wernicke’s area
An area around the primary auditory cortex that takes the tones and timings that make up language and interpret and put them together to make some sense in terms of language (why it takes a while to understand an accent, but eventually you understand it)
What is the temporal association cortex
The area of the temporal lobe involved in:
Memory
Mood
Aggression
Intelligence
(again don’t know specifics or all that it does, arguably the biggest ‘black box’)
The more the temporal lobe you take away the higher the chance of amnesia (lack of memory)
What is the parietal lobe
A section of the middle part of the brain superior to the lateral/sylvian fissure (all that fits between the central sulcus, parietoocipital sulcus, and above the lateral fissure)
It includes the post central gyrus/primary somatosensory cortex, the angular and supranational gyri, and the parietal association cortex
What is the post central gyrus
An area that sits within the parietal lobe that is also referred to as the primary sensory cortex.
Its primary function is to allow us to sense what is happening in the periphery (e.g. in the hands).
What the primary sensor cortex can feel is called discriminitive type sensation information - through complex set of mechanisms peripherally, is informed about where the body is in space, and can tell two points of touch apart - e.g. hand vs back (due to different amounts of neurons), along with nondiscriminative type sensation (ie pain and temperature) in the periphery.
Similar to the homuncular map in the primary sensory cortex, there is a roughly similar map in the primary sensory cortex
What is the supramarginal gyrus
An area posterior to the post central gyrus (still in the parietal lobe) that helps with understanding and constructing reading (why we can understand scan across a page and understand words)
What is the angular gyrus
An area posterior to the supramarginal gyrus (still in the parietal lobe) that is largely to do with writing
What is the occipital lobe
Backmost section of the brain
It contains the primary and secondary visual cortexes
What is the primary visual cortex
An area of the brain that is posterior in the occipital lobe and take information in through the eyes and the thalamus from the perigphery, and organises the information based on colour and location
What is the secondary visual cortex
Area including the anterior sections of the occipital lobes and part of the temporal lobe that is responsible for taking the physical information and making sense/order of it, therefore with more experience you are less likely to be tricked by what you see in the world/context (it uses past experiences to interpreting what you see)
What is the arcuate fisciculus
A connection that go down into the white matter and back into the grey matter to connect Wernicke’s area and Broca’s area. It is arch shaped
What is a fisciculus
A fisciculus is a bundle of white matter - all of the neurons that have sent axons through the white matter out to connect with another region of the brain, there are millions of fasciculi within the brain. There are fasciculi all over the brain, including from Wernicke’s area to the Angular gyrus, and from the angular gyrus to Exener’s area, and from Broca’s area, to the corresponding area in the precentral gyrus
Why do we have Primary and Secondary areas of the cortex
The primary areas of the cortex is involved in simply dealing with the information coming in - agnostic to its meaning
Then there are secondary areas of the cortex responsible for interpreting meaning and understanding things in the real world
What is a Motor/Non-fluent/Broca’s Aphasia
When a lesion/disfunction occurs within the Broca’s area
Means you have lost fluency in language
“Tan” - a person (who dies of sepsis - wouldn’t happen these days) called leborne who could only say ‘tan’
What is Sensory/Fluent/Wernicke’s Aphasia
When a lesion occurs within the Wernicke’s area (can also get one in auditofy cortex but different)
Means you can’t interpret/understand spoken word, but you yourself can speak normally
One way to test is to see if one understands spoken language is to ask them to write a verbal response rather than a spoken response from spoken language
What is Connectional Aphasia
When a lesion/disruption of the Arcuate Fasciculus
Means you can interpret correctly and speak fluently but there is not conenction between the two (good listening, good vocalisation)
Very hard to work out in practice
What are the key language areas and where are they located
Wernicke and Broca together unified the concept of what it is that makes up the language areas of the brain and showed how different regions of the brain are responsible for different jobs
Importantly the language areas (Broca’s, wernicke’s areas, and Angular and Surpramarginal gyrus) are only present on the dominant hemisphere of the brain, which for 100% of right handers and 80% of the left handers in the world, is the left side of the brain.
Therefore the left side of the brain is dominant for language, while the right is responsible for other things. All other regions mentioned are on both sides
What is predominantly dealt with in the dominant hemisphere
Language
What is the non-dominant hemisphere for
In the non-dominant hemisphere, we have things like:
Conceptual understanding (abstract thought - a very paritel lobe function
Artistic/Musical skills (fun fact, some people that have strokes and can;t speak can still sing)
Non-verbal language (body language)
Emotional expression (tone of language)
Spatial skills (3D)
Therefore those who have injuries in the non-dominant hemisphere can be impacted in these functions/skills
What is the Calcarine sulcus
A distinct line that is easy to see with a medial view
The primary visual cortex is largely around this sulcus (within the ‘banks of the calcarine sulcus’).
The secondary visual cortex is everything else (including an area below and above the primary visual cortex from the medial view)
What is the cingulate gyrus
A gyrus which is responsible for getting information to and from different cortexes (a relay point to other regions of the cortex)
What is the corpus callosum
An area inferior to the majority of the cingulate gyrus that is responsible for carrying information form right to left and left ot right.
This is unique/very important to higher primates - not something existent in rodents (they use other systems)
Underneath this is a fluid filled space, which is on top of a ventricular system which is also a fluid filled space
What is the midbrain
A small area of the brain that is underneath the ventricular system that links to the pons - it is important for motor functions
What is the hindbrain
The hindbrain consists of the cerebellum, the pons, and the medulla oblongata
What is the cerebellum
Region of the hindbrain, where 80% of the brains neurons are - very dense, has amazing symmetry
What is the forebrain
The forebrain includes all of the cortexes already discussed (frontal, parietal, temporal, and occipital lobe)
What important thing happens to the brain during development
During development, if the brain can’t develop accurately early on, the body has a way to get rid of the pregnancy - as the brain is vitally important. As such, many of the initial milestones of development surround accurate development of the brain (it finishes development at week 12)
In New Zealand you get scans at week 12 nd 20 to check the brain is developed correctly
At about week 4 after fertilisation (two weeks afterwards woman’s first missed menstrual period), the brain starts development and we arrive at the ‘3 vescicle stage’
The first vescicle (fluid filled space) is the forebrain
The second vescicle is the midbrain
The third vesicle is the hindbrain
For just a few days these vesicles are equal in size, but by week five they will develop - the forebrain will develop to get a lot larger, the hindbrain develops somewhat, and the midbrain develpes very little
