The Human Brain Flashcards by Poppy Aves

What does failure of the spinal cord closing cause?

Spina bifida or anencephaly

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What prevents most neural tube defects?

Folic acid

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What are the primary brain vesicles?

Prosencephalon
Mesencephalon
Rhombencephalon
Spinal cord

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What are the secondary brain vesicles?

Telencephalon
Diencephalon 
Mesencephalon 
Metencephalon 
Myelencephalon 
Spinal cord

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What does a dorsal fold in the rhombencephalon make?

Metencephalon

Myelencephalon

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What does the prosencephalon become?

Telencephalon

Diencephalon

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What are the adult derivatives of the telencephalon?

Olfactory lobes
Hippocampus
Cerebrum

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What are the adult derivatives of the diencephalon?

Retina (optic vesicle)
Epithalamus
Thalamus

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What are the adult derivatives of the mesencephalon?

Midbrain

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What are the adult derivatives of the metencephalon?

Cerebellum

Pons

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What are the adult derivatives of the myelencephalon?

Medulla

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Meninges of the spinal cord

Dura mater (outermost)
Arachnoid 
Pia mater (innermost)

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Where is most of the cerebrospinal fluid formed?

Cerebral ventricles

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Sites of origin of CSF?

Choroid plexus
Ependyma
Parenchyma

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What is the function of CSF?

To act as a buffer/cushion for the brain’s cortex providing basic mechanical and immunological protection to the brain

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Where does CSF occupy?

Subarachnoid space

Ventricular system around the inside of the brain and spinal cord

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What does it mean if CSF pressure is elevated?

Cerebral blood flow may be constricted

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What is hydrocephalus?

Abnormal accumulation of CSF in the brain ventricles

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What causes hydrocephalus?

Impaired flow of CSF

Impaired reabsorption or excessive production of CSF

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What is a lumbar puncture?

CSF is extracted through a needle between the 3rd and 4th lumbar vertebrae

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What is aqueductal stenosis?

Narrowing of the aqueduct of Sylvius which blocks the flow of CSF in the ventricular system
Life threatening in a short period of time
Restricts blood flow to the brain

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What is an ependymal cell?

A type of neuronal support cell that forms the epithelial lining of the ventricles of the brain and central canal of the spinal cord

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Structure of a ependymal cell

Have cilia on their surface

Influence the flow of CSF, bringing nutrients to neurons and filtering harmful molecules

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What is the function of the layer of ependymal-derived cells surrounding the blood vessels of the choroid plexus?

To produce CSF through selective uptake of water and other molecules from blood into cells
Then transported across cells
Secreted into lateral ventricles as CSF

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Where are tanycytes found?

The lining of the floor of the third ventricle of the brain

Structure of tanycytes?

No cilia Long processes and large end feet that connect to brain capillaries and neurons distant from ventricle Connected to one another by tight junctions

What do tanycytes do?

Facilitate transport of hormones and other substances in the brain

What is the blood-brain barrier?

A highly selective, semi-permeable membrane barrier which separates circulating blood from the brain extracellular fluid in the CNS

What forms the BBB?

Endothelial cells connected by tight junctions

What does the BBB allow to pass through passive diffusion?

Water Some gases Lipid-soluble molecules

What does the BBB allow selective transport of?

Glucose | Amino acids crucial to neural function

What cells are necessary to create the BBB?

Astrocytes

Where does the BBB occur?

Across all capillaries

What is the average rate of cerebral blood flow in adults?

750ml per minute | About 15% cardiac output

How is cerebral blood flow safeguarded?

Autoregulation | Small arteries - arterioles - constrict and dilate under complex physiological control systems

What is metabolic regulation?

Negative feedback system which balances cerebral blood flow to demand

What is myogenic regulation?

Transmural blood pressure changes are detected by vascular smooth muscles in arterioles Calibres are then adjusted to maintain blood flow

What is neurogenic regulation?

Vascular smooth muscle in the resistance arterioles are controlled via sympathetic innervation, input from the appropriate brainstem autonomous control centre Nitric oxide released by parasympathetic fibres may also play a part

What is the brainstem composed of?

Medulla oblongata Pons Mesencephalon

What does the brainstem do?

Regulates vital cardiac and respiratory functions | Ascending and descending tracts travel through the brainstem

What does the cerebellum do?

Muscle tone Co-ordination Motor error Learning

What is cerebellar ataxia?

Loss of cerebellar neurons | Jerky imprecise movements

What does the diencephalon do?

Links midbrain to cerebrum | Contains the thalamus, hypothalamus and pineal

What is the cerebrum?

2 cerebral hemispheres | 6 lobes

What are the lobes of the cerebrum?

``` Frontal Parietal Occipital Temporal Central Limbic ```

Function of the medulla oblongata?

``` Regulates breathing Heart and blood vessel functions Digestion Sneezing and swallowing Large lesions = death ```

Functions of the pons?

Bridges the sides of the cerebellum | Connects to cerebellum via peduncles

Functions of the thalamus?

Processing and relay centre All special sense except smell Arousal/emotion Higher functions

Functions of the pineal?

Endocrine organ | Produces melatonin and serotonin

Functions of the hypothalamus?

Eating Drinking Sexual behaviour Stress

What is Broca's Aphasia?

``` Damage to the left frontal lobe Impaired speech (grammar, syntax and word structure) ```

What is Wernicke's Aphasia?

Posterior temporal lobe damage | Superficially fluent speech but the inability to understand more than the most basic words

Types of modern brain mapping

PET scans fMRI Regional blood flow

What is lateralisation?

Right hand controlled by the left side of the brain and vice versa

What makes up the limbic system?

``` Limbic lobe Hippocampus Amygdala Thalamus Hypothalamus ```

What is the limbic system involved in?

Memory Emotions Motivation

Where is the basal ganglia located?

Deep within the hemispheres

What diseases is the basal ganglia implicated in?

Parkinson's | Huntington's

What do association fibres do?

Link areas within a hemisphere

What do commissural fibres do?

Connect between hemispheres

What do projection fibres do?

Link to non-cortical areas

What is the role of the upper motor neurons?

Taking impulses from the relevant part of the brain down to the synapses with the lower motor neurones.

What is the role of the lower motor neurons?

Connect with the target muscle | They run between the UMN synapse and the final action point

What is the role of the lower motor neurons?

Connect with the target muscle | They run between the UMN synapse and the final action point