2. Parts of the brain - Lecture notes 2 PDF

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Summary

Brain linguistics Superior means above Anterior means in front of Posterior means behind Inferior means below Dorsal = towards the back of the body (is actually towards the top of the brain because we stand upright Ventral = towards the stomach Caudal = towards the tail (so towards our feet and towa...

Description

Brain linguistics -

Superior means above

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Anterior means in front of

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Posterior means behind

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Inferior means below

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Dorsal = towards the back of the body (is actually towards the top of the brain because we stand upright

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Ventral = towards the stomach

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Caudal = towards the tail (so towards our feet and towards the back

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Rostral = Toward the beak (so the front)

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Lateral = away from the midline

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Medial = toward the midline

Ways of slicing a brain -

coronal (width ways),

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sagittal (lengthways)

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Transverse (horizontal, half way from bottom and top)

Information processing -

Info comes in through the brain stem and does circuits through the brain to be processed -

Inputs from sense outputs to muscles and organs

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If you slice through the medulla, pons and cerebellum you find a lot of white matter

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Also find some nuclei which is grey matter

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White matter is connections between brain areas

Brain = Input (sensations) -> Computation (cognition/processing) -> Output (effect = observable behaviour) The nervous system produces movement in a perceptual world that the brain constructs.

Central Nervous System (CNS) Part

that does the computation Brain +spine Spinal cord –> neural tissue encased and connects with structures in brain

Peripheral Nervous System (PNS) Collects input and sends out signals leading to observable behavior All the nerves that branch off the Brain + Spine Works in both directions to collect info and send out motor outputs

Parts of the PNS Sensory division (afferent) -

Picks up sensory stimuli through Sensory neurons U sense stuff (neurons tell central nervous system about environment)

Motor division (Efferent) -

Motor Neurons that tell u do do stuff

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Sends info from ur brain to the muscles and glands - This contains the somatic nervous system and the autonomic nervous system.

Somatic nervous system (SNS) ( Voluntary actions) Senses and makes effect on the external environment -

e.g. removing hand from something hot

Your skin sends in a sensory neuron and has a synapse (the outlet) into the spinal cord. -

It has a sensory neuron soma in the middle of the cell body.

Conscious decision -

Sensory neurons go from skin into the spinal cord to the brain which activates a motor neuron to tell the muscle what to do.

Reflex: -

Automatically generated from within the spinal cord

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Don’t need to go to the brain for very quick reflex actions.

Spinal cord: -

Is made of white matter and grey matter

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Grey matter (sensory pathways)

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The cell bodies that do the processing between cells and synapse

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To take info from the brain

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Regulating reflexes pain etc

White matter (motor pathways) -

Axons of cells (information highways)

Each part of ur spinal cord is connected (through nerves) to different areas of ur body. -

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Shingles (Dermatomes sensation ) -

Each vertebrae attaches sensation to one specific part of your body

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Is a rash that messes with a single nerve which is connected to a single part of the spinal cord

Myotomes movement (motor neurons) -

Send information to specific parts of the body

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Injury on different parts of the vertebrae will affect movement in specific body parts -

Break of spinal cord on top will have more parts affected than the bottom of ur spinal cord.

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Dorsal root

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Neural inputs come in to spinal cord through

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Ventral root

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Output to muscles or to control muscle function goes out through (lower surface of spinal cord))

Autonomic nervous system (ANS) (involuntary) Deals with monitoring and affecting internal sensations and actions that are controlled involuntarily -

Eg: internal organs reacting to signal (heart rate increase)

Divided into 2 divisions of nerves which have opposing actions. -

Sympathetic division (fight or flight response) -

Arouses body for action Increase muscle, dilate pupils, increase heart rate, restrict vessels to digestive system, stimulate release of sugar from the liver

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Parasympathetic (rest and digest) -

Preparing body to rest and digest by reversing the alarm response

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Increase digestion, no blood to muscles,etc

Enteric nervous system: -

Network of neurons embedded in lining of gut

Parts of the brain Spinal cord: -

Where info (signals) from the body go up from the muscle to the brain then back down to the muscle.

Brainstem

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Made of midbrain, pons and medulla

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Core of everything

Cerebellum -

Aka little brain

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Behind the brainstem (posterior caudal hemisphere of the brain)

Forebrain -

Made up of 2 parts -

Cerebral hemisphere

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Diencephalon -

Made up of thalamus and hypothalamus

Ventral view = front

Dorsal = back

Brain stem

From the outside White matter -

Majority of brain stem = tracks of white matter (nerves) Processes from neurons and axons

Cranial nerves (the sprout looking things) -

Signals to and from head and face

Pyramid: - Carry descending info from the motor cortex to the spinal cord Brain organisation : Decussation of information -

The info from one half of your body is going to be crossed over to the other side of the brain.

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The information will ‘decussate’ from one side of the body to the other side of the brain. The crossing over happens in the brainstem -

Motor information decussates in the pyramid then will go to the brain.

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Somatosensory information (sensory info) that switches sides in the medulla and the brainstem

Superior colliculus - Seen in the middle of the two thalamus (in dorsal view) -

Takes in sensory info and generates fast responses.

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Important area for fast basic movements.

- ex : someone makes a noise, u turn ur whole body + eyes to see what happened quickly From the inside, There are nuclei (collections of brain cells) -

The info from the cranial nerves either come or go from. -

Could be sensory info - Ex: the cochlear nucleus (in blue) receives info from the ear.

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It could also be motor outputs -

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Ex: The oculomotor nucleus will take information and send it out to control ur eyes.

The info could also go from the vagus nerve, which gives info to regulate autonomic function - Controls automatic functions like heart rate or breathing.

Reticular formation -

Center of the brainstem from the medulla to the midbrain

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Has circuits that control the heart rate and breathing (which means if u damage it, u stop living)

The nuclei on the top of the brain stem (colorful circles) - Contain neurotransmitters : regulate many things

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Dopamine

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Acetylcholine

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Noradrenaline Serotonin

They send neurons from the brainstem across the brain -

This way, they can control a lot of neuron activity.

Medulla

Pons

Midbrain

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At the top of the spinal cord

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Where it flattens out

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Connections pass through

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Many connections pass through pons

medulla on way up/down from

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brain -

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(collections of cell bodies, same appearance) -

Regulates many autonomic functions -

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e.g. breathing, heart rate, sneezing, etc.

Damage can be fatal – essential functions are controlled here

Deep in the brain so less vulnerable to damage

And from forebrain to/from

Just above the pons Important relay as with medulla and pons

from spinal cord to diencephalon and cortex,

Consists of different nuclei

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Two structures are: - Superior colliculus -

cerebellum -

Many nuclei having specific or multiple functions -

Eg:: auditory processing, breathing rate, state, sleep etc

receives both visual and auditory information

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- Critical toorienting behaviour Substantia nigra is critical to motor control -

Eg: parkinson's disease

Cerebellum ‘little brain’ -

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Very folded structure, -

Organised structure :

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layers of big neurons called “Purkinje cells” | | Small packed cells called ‘ granular cells” ( between the purkinje cells)

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White matter -> in between the granular cells, the core of the cerebellum.

full of lots of info + from the cerebral cortex, the spinal cord and the thalamus

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Sends out info to motor regions and brain Sits behind the brain stem

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Used in refining sequences movement -

e.g. thoughts or learning a sequence

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It can do this because it can take in a lot of info about sensory and motor input and associate them together. -

(because of its organised structure, the massive dendritic trees (the granular cell layer) collect info and associate them together to produce an output that ties them together.

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Layered cortical structure with cells on outside, connections through middle

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Inputs from cerebral cortex and spinal cord (via pons), thalamus

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Outputs via cerebellar nuclei, to pons on to cerebral cortex and spinal cord

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Functions include modifying descending (motor) commands to make adaptive and accurate

Diencephalon -

Main structure is the thalamus and hypothalamus (underneath thalamus) Thalamus – Connecting station

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Contain collections of neurons

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is the information hub

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Relays on ascending and descending information from widespread brain areas

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Very organised. Diff parts of the thalamus takes in diff kinds of info.

So the info that comes into the thalamus is slightly diff than the one that goes to the diff parts of the brain.

Hypothalamus - Controls autonomic function -

lots of nuclei

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Links brain to the hormonal system (connects to the pituitary gland)

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Autonomic functions like: breathing, temperature control, sexual behaviour, feeding, drinking etc.

Cerebrum (‘little brain’:) -

Contains the cerebral cortex -

Folded structure on top of ur head.

Subcortical structures within the cerebral cortex Basal ganglia : coordinating movement functions and motivated behavior (via dorsal striatum) -

Info comes from cortex and hippocampus through basal ganglia and thalamus then back to cortex.

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Modulated by dopamine from VTA/Substantia nigra

Hippocampus – associative learning, spatial memory, and pattern completion -

Thinner than the cerebral cortex (only has 3 layers)

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Curves like a rams horn behind the brainstem.

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To also reactivate old memory (pattern completion)

Amygdala – emotional processing ( e.g. fear )

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Key connections with all the regions that surround it.

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Known for emotional learning

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Associate environment with an emotive state and behave accordingly (automatic behaviors like startled when fear)

Corpus callosum – connections from one side of the brain to another

Cerebral cortex Divided into series of lobes -

Frontal lobe

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Parietal lobe

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Occipital lobe

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motor and executive functions tactile functions

visual functions

Temporal lobe -

visual, auditory and gustatory functions

6 layers in cortex (made of grey matter) -

Different layers (made cells) have different functions.

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Processing units organised vertically away from the surface, critical in way in which

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The first 3 layers

cortex works -

Have integrative functions -

To integrate intracortical information

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The middle (4th layer)

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The bottom 2 layers

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Receives sensory input Output to regions outside the brain/lower brain regions.

Ventricles -

Fluid filled spaces

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Highly folded to increase surface area

Bloody supply: -

Specialised blood supply as brain needs lots of energy

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Stroke: blocked cerebral blood vessels starve the area fed by that vessel

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- Stroke: burst blood vessel leads to local damage and starvation of area beyond burst

Mammalian brains have a broadly similar structure -

develop from a simple sunken tub early in development

Summary 1. As a whole, the nervous stern takes inputs (senses), performs computations and generates an output (behaviors) 2. Diff parts of the brain (nervous system) do diff things a. Diff parts of the nervous system perform diff computation but are interconnected 3....