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06. Neuroscience > L1. Functional Organisation of the CNS > Flashcards

L1. Functional Organisation of the CNS Flashcards

1
Q

Describe the difference between the CNS and the PNS (different parts of the one nervous system)

A

CNS = brain and spinal cord PNS = nerves and ganglia

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2
Q

The basic structure of the brain contains … (label the diagram)

Cerebrum Cerebellum Brainstem (pons, midbrain, medulla, spinal cord, hypothalamus, thalamus, basal ganglia and limbic system)

A
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3
Q

What is the limbic system?

A

A group of forebrain structures that includes…

  • hypothalamus
  • amygdala
  • hippocampus (connected to the hypothalamus by the fornix)

They are involved in motivation, emotion, learning and memory

They are the structures where the subcortical structures meet the cerebral cortex.

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4
Q

What is the difference between the grey and white matter of the brain?

A

GREY MATTER: making up the cortex and outer part of the brain made up of neurons, somata (cell bodies) and glia, with dendrites and synapses. WHITE MATTER: the inner part (core) of the brain containing axons and glia. The white matter is the wiring and connections between places in the brain.

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5
Q

Why is it important to know the organisation of white and grey matter in a fixed section of the brain?

A

Because CT and MRI imaging techniques are able to visualise grey and white matter in the same detail

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6
Q

Why are diffusion weighted MRI techniques becoming very useful in CNS imaging?

A

Because they show white matter tracts in the brain - they are tuned in a way to see only white matter and thus how the axons are orientated in the brain.

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7
Q

The brain has a major kink between the midbrain and diecephalon. What does this mean for relative anatomical directions in the nervous system?

A

Above the brainstem, the major longitudinal axis of the brain is through the forehead and thus DORSAL is referring to the top of the head. At the level (and below) the brainstem, the major axis is vertical and the same as body axis so the DORSAL direction is the back of the neck.

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8
Q

The two cerebral hemispheres are separated by what fissure?

A

A longitudinal Fissure The halves are not joining together until the level of the corpus callosum

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9
Q

Describe the surface of the brain (the cerebrum)

A

It is the cortex Ridges called Gyri/gyrus Grooves called sulci/sulcus The left and right cortices are linked by the corpus callosum

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10
Q

What is the major function of the cerebrum?

A

Site of language, memory, emotions, self awareness Hence damage leads to loss of aspects of ‘you’ as a person Eg. dementia

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11
Q

What are the four main divisions of the cerebral cortex? What is the significance of this division system?

A

Frontal, Parietal, Temporal and Occipital Limited functional significance as most of the boundaries don’t map functionally significant changes

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12
Q

Do the different gyri and sulci have functional significance?

A

Not really

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13
Q

What are the Brodmann areas of the brain?

A

Organisational description of the brain based on the cellular differences (histology)

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14
Q

What is meant by functional labelling of the brain?

A

Evidence based labelling of the brain based on known functions of the brain

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15
Q

Describe the significance of functional imaging (eg. fMRI)

A

It reflects neural activity while performing specific tasks

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16
Q

Describe the cellular structure of the grey matter of the cortex

A

A LAYERED STRUCTURE containing different shaped neurons (PYRAMIDAL + INTERNEURONS + Other) organised in different layers giving different functions.

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17
Q

Describe the functionality of the Cerebellum

A

It is a key element in MOTOR CONTROL It compares what you want to do with what you are actually doing by feedback loops for REAL TIME ADJUSTMENT for smooth and successful movement - refines execution. Cerebellar damage thus appears as clumsiness

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18
Q

What is the basal ganglia and where is it located?

A

Set of nuclei (collection of cell bodies) gathered together doing the same task. They are located at the core of the brain in the telencephalon

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19
Q

What are the main parts of the basal ganglia?

A

Caudate nucleus Putamen (also called striatum) Globus pallidus Subthalamic nucleus Substantia nigra

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20
Q

What is the functionality of the basal ganglia?

A

Important in MOTOR CONTROL Forms LOOPS with the cortex as it selects and initiates VOLUNTARY movements Damage to the basal ganglia thus appear as motor disorders like Parkinson’s Disease and Huntington’s Disease

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21
Q

What is the thalamus and where is it located?

A

There are two oval shaped thalami on either side of the brain that make up part of the diencephalon in the centre of the brain.

22
Q

What is the main function of the thalamus?

A

A major sensory RELAY centre to the cortex. Sensory information from the periphery feeds to the brain aiming for the cortex to be perceived by the individual. But first it is PROCESSED BY THE THALAMUS (the gateway to the cortex)

23
Q

The thalamus has SUBNUCLEI, what is the significance of these?

A

They are subdivisions of the thalamus each representing a subdivision of the cortex. Hence there is mapping of the cortex and thalamus together.

24
Q

The thalamic nuclei project information in three ways, what are these?

A
  1. Sensory info to specific areas of the cortex
  2. Non-sensory info from cortex and basal ganglia to specific areas of the cortex
  3. Global projection of information to the cortex to cause arousal and sleep.

Note: The thalamus lies in the basal ganglia loop (so motor information is also relayed across the thalamus)

25
Q

What is the hypothalamus and where is it?

A

It is a tiny v shaped region on the ventral surface of the brain in the midline just below the thalamus (very small section in the order of mm). Forms part of the diencephalon

26
Q

What is the function of the hypothalamus?

A

It regulates homeostasis (temperature, blood pressure and volume, ion concentration, pH, O2 levels, glucose regulation and reproduction) Also controls pituitary gland (is the master endocrine gland) - the pituitary hangs off the bottom of the hypothalamus

27
Q

Describe the controls of the brainstem

A

Controls… Facial muscles Sensation from the face and head Contains the cardiorespiratory control centres (works with the hypothalamus) Arousal, sleep/wake cycle (with the thalamus)

28
Q

Where do the cranial nerves originate from? What do they do?

A

The brainstem They provide sensory and motor supply to the face and deeper structure via 10 (of the 12) cranial nerves

29
Q

What type of nerves (motor/sensory) are the cranial nerves?

A

They can be purely motor, purely sensory or mixed nerves

30
Q

The spinal cord forms part of the CNS. Where does it originate from and what is it protected by? At what level does the spinal cord end?

A

Originates from the medulla of the brainstem (ie. the distal most part of the brainstem) and is enclosed in the vertebrae The spinal cord ends at L1/2

31
Q

Describe the anatomy of the spinal cord

A

Core of GREY MATTER in a H-shaped or butterfly shape with 4 horns sticking out The grey matter is surrounded by WHITE MATTER

32
Q

What are the main parts of the grey matter of the spinal cord?

A

The dorsal (posterior) horns The ventral (anterior) horns Intermediate zone in the middle

33
Q

What makes up the white matter of the spinal cord?

A

Axons running up and down the spinal cord connecting local circuits the the brain (sensory) or motor information to the spinal cord.

34
Q

The spinal cord changes in shape and characteristics as it descends. What are the two main enlargements and why is this?

A

Cervical and lumbar enlargements (with more grey matter) at the level of the limbs which have more sensory and motor requirements.

35
Q

What is a spinal segment?

A

For each vertebra, there are spinal roots/segments that gives rise fo a pair of spinal nerves that leave that verebrae

36
Q

Each spinal nerve is formed by dorsal and ventral roots joining together. What is the difference between function of the dorsal vs. ventral roots?

A

The Dorsal root is purely sensory - Cell bodies of the dorsal root are in the dorsal root ganglia (ie not part of the CNS) Ventral root is exclusively motor in function for control of skeletal muscles of the body. - Cell bodies of the ventral root are in the ventral horn

37
Q

What are 2 other names synonymous to Dorsal Root Ganglia (DRG)

A

Primary afferent neurons Sensory neurons

38
Q

Where are the dorsal root ganglion?

A

They are hidden between vertebrae (part of the PNS) lying very close to the spinal cord

39
Q

Since the Dorsal Root Ganglion cell bodies are in the DRG, they are described as branching neurons (one arm going either side of it). Describe this

A

One branch is through the peripheral system and DETECTS SENSORY STIMULUS and carries information towards the soma in the DRG to be processed. One branch enters the dorsal horn via the dorsal root and goes towards the brainstem. [note some cranial nerves have cranial nerve ganglia - equivalent in function to DRG]

40
Q

What kind of nerves (motor/sensory) are spinal nerves? What does this mean in terms of pathology?

A

Because dorsal and ventral roots combine together to form the spinal nerves, it means the spinal nerves are MIXED NERVES and damage to a spinal nerve gives a mixture of motor and sensory dysfunction.

41
Q

What are dermatomes?

A

The region of the body innervated by a bilateral pair of dorsal root ganglia (sensory- touch and skin sensation mainly)

42
Q

What are the ventricles?

A

Hollow centres of the brain (embryonic remnants of the neural tube) that contains circulating CSF

43
Q

Why is the 3D shape of the ventricles important?

A

They are a landmark structure in MRI and CT imaging (can tell what part of the brain you are looking at based on the ventricle)

44
Q
A
45
Q

What are the different ventricles of the brain?

A

2 lateral ventricles third ventricle fourth ventricle cerebral aqueduct

46
Q

What is the vascular choroid plexus?

A

It is present in the ventricles (lining them) and forms the CSF (which is an ultra filtrate of the plasma).

47
Q

Why is CSF important for the brain?

A

The brain has no internal connective tissue and structure thus cannot support itself. The CSF allows it to float

48
Q

Describe circulation of CSF

A

CSF flows through the connected ventricular system of the brain and then flows out of the fourth ventricle into the narrow subarachnoid space and then reabsorbed by major veins at arachnoid granulations in the large sinuses.

49
Q

What are the falx cerebri and tentorium cerebellum?

A

Extensions of the dura mata that divides the cerebral hemispheres and the cerebellum from occipital lobe respectively. it is important as swelling of the brain is limited by these

50
Q

What is extracellular fluid of the brain protected by?

A

The blood brain barrier. Especially important as neurons are sensitive to fluctuations in ion concentration

51
Q

Describe the blood brain barrier

A

Formed by endothelial cells of capillaries forming both a physical and a functional barrier. There is no pinocytotic transfer and there are very strong and impermeable TIGHT JUNCTIONS Most transport through the blood brain barrier is ACTIVE

52
Q

Describe the lipid solubility of the blood brain barrier

A

The more lipid soluble, the better able the molecule is able to cross the blood brain barrier

06. Neuroscience (31 decks)

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