Module 2: The brain and neurons Flashcards
what are the 3 major parts of the brain?
cerebrum
cerebellum
brainstem
what is the biggest part of the brain?
the cerebrum
Talk about the features of the cerebrum
It is the biggest part of the brain.
splits into the 2 cerebral hemispheres.
how are the cerebral hemispheres connected from the surface?
through the longitudinal fissure/interhemispheric fissure
internally, how are the hemispheres connected?
through the corpus callosum, a thick layer of axons
is there any contact between the cerebral hemispheres?
on the surface, NO. they ONLY communicate through the corpus callosum.
define cortex.
The cortex is basically the grey matter and it is the surface of the brain.
It is 2.4 mm thick and contains the major neurons that compose the functioning of the brain
what is found in the cortex?
the cell bodies of neurons
why is the surface folding pattern important?
Because we want to fit all billions of millions of neurons into this very small organ (the brain in the skull) and so it needs to be condensed and folded to fit everything in it.
what is below the grey matter?
the white matter. contains axons and dendrites of neurons
What is the main role of the white matter?
connects the neurons from the cortex to the spinal cord which diffuses the messages to the targeted organs
what are the four lobes and the location?
1) occipital lobe, to the back of the head
2) temporal lobe, above the brainstem close to the ears
3) frontal lobe, to the front of the head
4) parietal lobe, central line of the brain; anterior to the frontal and posterior to the occipital
What is Broca’s region?
the region in the frontal lobe that is essential for speech production. People with damage to this region can understand language perfectly but cannot produce speech; slow sentences that make 0 sense.
what is Wernicke’s area?
Region in the temporal lobe responsible for speech understanding.
Any damage to this area will cause the individual to not understand language and speech, but can produce it well.
what are the function of the occipital lobe?
- Shelters the primary visual cortex.
- Responsible for all perception.
- Modular system/regions in the occipital lobe to detect different aspects of the visualized thing: edges, colors, shape, orientation.
what kind of system reigns in the occipital lobe?
A modular system
what is a modular system?
when different regions of the brain/the lobe have different groups of neurons with different functions each, to detect different aspects.
what are the functions of the frontal lobe?
-Shelters the primary motor cortex.
-Responsible for all movements/muscle contractions in our body.
-Responsible for executive functions: decision making, analytical thinking, planning, inhibitory control.
Important in speech production.
What are the function of the parietal lobe?
- Shelters the primary somatosensory cortex.
- takes input from the occipital lobe (visual perception) and helps build a representation of space and orientation.
- what we see is a very messy “video” that the parietal lobe organizes and makes clear. detects objects from backgrounds, moving objects from still objects, etc…
- most important function is that it links action to vision and helps fine controlled movement based on what we see.
What are the functions of the tempral lobe?
- Shelters the primary auditory cortex.
- Perception of sounds.
- Understanding language and speech
- Limbic system
What is a particular region of the temporal lobe?
The limbic system;
it is made up of
1) the amygdala: activates the alert system in the face of danger. Very quick to activate and alert us from incoming threats.
2) the hippocampus: important in learning and memory. Any damage to the hippocampus -> cannot form new memories.
what is the corpus callosum made up? and what use is it to destroy it?
Made of axons of neurons.
It is the ONLY mode of communication between the 2 cerebral hemispheres.
With epileptic patients, cutting the corpus callosum stops the spreading of the seizure from one hemisphere to the other, and makes it more bearable.
also it is important to evaluate each hemisphere functioning independently.
what did we rely on to evaluate brain functions before MRI existed?
case studies
what is the most poplar case study?
that of Phineas Cage in 1848
what year did Paul Broca identify the Broca region in the left side of the frontal lobe?
1861
what do we call disorders of language and speech?
Aphasias
Define aphasia.
Disorder of language and speech
What are the two popular aphasias in the brain and where are they located?
- Broca’s aphasia ; left side frontal lobe
- Wernicke’s aphasia ; left posterior temporal lobe
how long did Phineas Cage survive after his accident in 1848?
12 years
how long did Phineas Cage survive after his accident in 1848?
12 years
what happened to Phineas Cage in 1848?
A 1 m long rod whet up through his skull and landed on the floor on the other side of the road.
He remained conscious during and after the accident.
what areas were damaged in Phineas Cage’s brain?
His frontal lobe
Who identified the importance of the frontal lobe for executive control of behavior?
John Harlow after observing changes in personality in Phineas after his accident
what is phrenology?
Mapping out the bumps on the skull to determine the functions of each brain region.
how did John Harlow describe Phineas Gage after the accident?
“A man who was no longer a man”
When was the Broca region identified first? (before Broca named it and researched it)
mid 1800’s
When was the Broca region identified first? (before Broca named it and researched it)
mid 1800’s
define anomia?
the difficulty to find appropriate words.
What are the consequences of damages to the Wernicke’s area?
Can speak fluently with normal rhythm.
Can’t understand a thing.
Their speech sounds normal but makes 0 sense.
Deficits of Wernicke aphasia are….
- Deficit in connecting meaning to language.
- Deficit in understanding people’s speech.
a) In the mid 1950s, how did we map out the brain functions?
b) Who was the scientists?
c) According to which 2 lobes?
d) And what was the name of the resulting map?
a) Through electrical simulations to specific areas of the brain during surgery.
b) Wilder Penfield
c) according to the primary somatosensory cortex and the primary motor cortex. (frontal and parietal lobes)
d) the homonculus
What was the size of the different cortexes on the map proportional to?
- The level of fine motor control with that part of the body.
- The level of sensory discrimination we have with that part of the body.
what are the most important areas/largest areas on the homunculus and why?
a) finger and hands -> sensory and fine movements
b) lips, tongue and mouth -> speech requires very fine controlled movements.
what are the 3 roles of the brainstem?
1) connects the cerebral hemispheres to the spinal cord.
2) carries information between cerebral hemispheres and cerebellum, cerebral hemispheres and spinal cord.
3) drives the autonomic nervous system.
split the nervous system into its diff components.
CNS - PNS
PNS -> Autonomic and somatic
autonomic -> parasympathetic and sympathetic.
what is the CNS made of?
brain + spinal cord
what is the PNS made of?
all the neurons scattered around the body, outside brain and spinal cord
What are the functions of the somatic nervous system?
Domain of physiology
1) control voluntary movement.
2) Motor + sensory
nerves go from somatic nervous system to….
muscles
what are the function of the autonomic nervous system?
Domain of biology
1) controls involuntary movement.
heart rate and respiratory rate.
2)Fight or flight / Rest and digest
What is the sympathetic nervous system part of and what are its functions?
Part of the autonomic NS -> PNS
responsible for the fight or flight response: when subject to danger, a survival mechanism activates everything in the body to face the danger.
increased heart rate, increased respiratory rate, sweaty palms, high adrenaline, etc…
What is the parasympathetic nervous system part of and what are its functions?
Autonomic NS -> PNS
“Rest and digest”
in times of calmness and no danger, calms the body down
processes for digestion continue and are enforced, steady heart rate, etc…
what drives the autonomic NS?
The brainstem and the medulla/ medulla oblongata.
What is the main function of the brainstem?
Maintain Homeostasis in the body.
keep the central core warm to keep the vital organs functioning and healthy.
What is the medulla?
- The center of control of heart rate, respiration, blood pressure regulation, and body temperature.
- The center of reflexes. the messages that are controlled from the spinal cord and only make it to the brain after the response movements is done.
Give an example of how the medulla keeps us alive through reflexes.
When we are coughing or vomiting -> these are reflexes to keep our airways open and keep us alive.
what is the scientific term for “coma”?
And what is it characterized by?
- Persistent Vegetative State
- loss of conscious awareness
what causes a persistent vegetative state?
Severe damage to the upper brain
upper brain = hemispheres and cortexes
how come patients in a persistent vegetative state can maintain a steady heart rate and respiration, along with facial and eye movements?
If the brainstem is intact, all the autonomic functions remain.
As for the eyes and facial expression, cranial nerves stem from the brainstem to those organs and control their movements.
what is the diseases that results in locked in syndrome?
ALS = amyotrophic lateral sclerosis or motor nueron disease
what causes ALS?
Loss of motor neurons or loss of connection between the cerebral hemispheres and the spinal cord or brain injury
Can everything be intact and a person still suffer from ALS?
YES.
even if both the cerebrum AND the spinal cord are intact, if they are not connected, THERE IS NO MOTRICITY.
in this case, cognitive functions are still intact, mental health is perfect, there just is NO RESPONSIVENESS
What did Owen Adrian find in patients in a persistent vegetative state?
Through MRI, he found that people in a persistent vegetative state could still follow instructions and activate certain areas of their brain upon demand.
they have conscious intentions and exerience.
what do people in a persistent vegetative state and locked in patients have in common?
their cortex is fully functionnal
they can still activate regions of their brain upon commands.
Low level and High level functions of the brain.
-Low level = brainstem.
Critical for survival, not unique to us as humans.
-high level = cerebrum
unique to us as humans
highly evolved and complex in our language and problem solving and reasoning.
why can’t we tickle ourselves?
because of the feedback loop between the action and the sensory information we get as the action is performed.
When I’m about to tickle myself, my brain makes a prediction of wat it’s going to feel like. when I do it, it matches my prediction -> I’m not tickled.
when someone else tries tot tickle me, my brain has no access to the motor plan of the other person (It happens in their own brain) so my brain cannot make predictions -> no feedback loop.
what does our control and coordination of skilled movements rely on?
on the feedback loop between the movemetn we make and the senation we get as we are performing the movement.
what does the feeback loop give us?
the sense of agency over our own actions and the ability to identify if the things happening around us are CAUSED by us.
what are the functions of the cerebellum?
- adjust posture and balance in an involuntary fashion, constantly. (autonomic N.S)
- Involved in motor learning of skilled fine movements (movement adjustment)
What are the adjustments done by the cerebellum based on?
on the feedback loop
what is the basis of balance?
the center of mass should be adjusted above our feet at all time.
unconscious and no-concentration required for the posture adjustments.
where is this feedback loop the highest in?
the primary motor cortex and the primary sensory cortex.
what is meant by movemetn sequencing?
Each signal sent by the motor cortex will contract A SINGLE MUSCLE. However, complex movements require the contraction of multiple muscles at one; the brain sets out a sequence of signals that are sent out sequentially, in order to perform the higher complexity movement.
Main criteria for the brain sequencing of motor signals is __
it is SEQUENTIAL.
different muscles contracted at different times (milliseconds apart)
what happens to a skill when we learn it?
it is stored in our memory/hippocampus
The brain will either creat a program ___(1)___ or ___(2)___ like a signature
1) right before the movement
2) retrieve a program of a learned skill than perform it
why is the feedback loop important in learning new complex skills?
it helps us fixe our mistakes
why are skilled movements considered so complex?
Because the program is created immediately before the performance and DURING the program, sensory info is being sent back to the brain to give a feedback
what is proprioception?
all our muscles are covered in sensors to inform us of how stretched our muscles are. gives us a sense of where our limbs are compared to our body.
what is proprioception?
all our muscles are covered in sensors to inform us of how stretched our muscles are. gives us a sense of where our limbs are compared to our body.
what was Raymond Cajals doctrine on neurons in the late 1800’s?
the brain and the nervous system are made of individual discrete cells, the neurons.
what are neurons made of?
1) cell body englobing the nucleus.
2) the axon
3) axon terminal
what makes neurons so special? (one structure only found in neurons)
- The cell body of neurons is covered with dendrites that receive input signals.
- > 1 neuron has many dendrites and each dendrite receives signals from thousands of other neurons.
what is the longest axon in our body?
axon from toes to base of spine = 1 meter long