Central Nervous System Flashcards
Describe the meninges of the CNS
Describe the blood brain barrier
Highly selective semipermeable border (endothelial cells) that prevents solutes
in the circulating blood from non-selectively crossing into the CSF
What is the hindbrain also known as
rhombencephalon
What are the brain and spinal cord enclosed in
In bony tissue
Name the regions of the hindbrain
-pons
-medulla oblongata
-cerebellum
Describe the medulla oblongata
Connection to (and nuclei of) 7th to 12th cranial nerves
Contains the cardiovascular and respiratory centres
Contains ascending and descending tracts
Describe the autonomic functions of the medulla
Heart rate and blood pressure
Breathing
Digestion
Swallowing
Sneezing
Conduction pathway for nerve tracts
Sensory nuclei
Role of the medulla in adjusting blood pressure
Role of medulla in adjusting breathing rate
Explain the importance of the medulla
Houses the spinal nucleus of the trigeminal nerve - plays a major role in the processing of sensory information from the mouth and face
extremely important in the processing of inputs related to pain and temperature from the oro-facial region
Acts as a conduction pathway for all nerve tracts passing from the spinal cord into the higher levels of the brain
What happens to the medulla under pressure
If anything causes accumulation of fluid within the cranial cavity, the intracranial pressure is raised.
As the cranial cavity is closed, the medulla is displaced downwards into the spinal canal of the cervical vertebrae and is compressed - “Coning”.
The cardiovascular and respiratory centres are compromised – this is LIFE THREATENING
Describe what the pons contains
ascending and descending tracts
The nuclei of the 5th (trigeminal – main sensory nucleus),
6th (abducent) cranial nerves and vestibular nuclei
Nuclei that connect motor pathways to the cerebellum
Functions of the pons
Assists in controlling autonomic functions
Relays sensory information between the cerebrum and cerebellum
Arousal
Sleep
Cross-section of the pons
What the role of the cerebellum
Coordinates movement
What happens if the cerebellum is diseased or damaged
motor movement becomes inaccurate (cerebellar ataxia)
What are signs of cerebellar ataxia
Signs include nystagmus (uncontrolled eye movement), dysarthria and wide-based staggering gait
What are the 3 subdivisions of the cerebellum
Spinocerebellum
Cerebrocerebellum
Vestibulocerebellum
Describe the vestibulocerebellum
The oldest part of the cerebellum in evolutionary terms
Participates in balance and spatial orientation
Primary connections are with the vestibular nuclei (nucleus of 8th cranial nerve)
Damage to this region causes disorders of balance and gait.
Describe the spinocerebellum
Functions to fine-tune body and limb movements
It receives proprioceptive inputs from muscles and joints from the dorsal columns of the spinal cord and the trigeminal nerve
Input from the visual and auditory systems
It sends outputs to both the cerebral cortex and brainstem
Provides fine control of descending motor systems
Describe the cerebrocerebellum
This is the largest functional division of the human cerebellum
Receives input from the cerebral cortex and sends output to the thalamus (in turn connected to motor areas of the of the cerebral cortex)
It is involved in the planning and timing of movements and also plays a role in cognitive functions.
What is the midbrain also known as
Mesencesphalon
Describe the midbrain
The midbrain is small
Posteriorly it has small bumps – the colliculi
Anteriorly the cerebral peduncles connect the hindbrain and spinal cord to the cerebrum
Which cranial nerves arise from the midbrain
3rd and 4th cranial nerves
-Oculomotor and trochlear nerves
Functions of the midbrain
Body movement
Controlling responses to sight
Eye movement
Pupil dilation
Hearing
Describe the appearance of the superior and inferior colliculi and overall function of both
Appearance:
These appear as distinct bumps on the posterior surface of the midbrain, superior colliculi positioned rostrally
Overall function:
Integrate inputs to localize the source of various sounds and identify them as coming from a specific direction; can initiate head and body turning to orientate towards sound sources
Describe the function of the superior colliculi
The superior colliculi receive input from the retina and vision-related areas of the cortex; they are involved in visual processing, in particular in the control of eye movements
describe the function of the inferior colliculi
The inferior colliculi receive input from brainstem auditory nuclei and the auditory cortex
Name the two important pairs of nuclei in the anterior part of the midbrain
The red nuclei – where information from the cerebellum joins motor pathways
The substantia nigra
(part of a wider system)
Describe the function of the substantia nigra
uses dopamine as a neurotransmitter and
inhibits unwanted movement
amplifies desired movement
Describe Parkinson’s disease
In the neurodegenerative disease, Parkinson’s Disease, dopamine is deficient so these effects do not occur producing
tremor at rest (= unwanted movement)
poverty of movement (= no amplifying of movement)
What is the forebrain also known as
prosencephalon
Name the subdivisions of the forebrain
Telencephalon:
Cerebrum (pair of large cerebral hemispheres)
Cerebral cortex
Basal ganglia
Diencephalon:
A group of structures deep within the cerebrum including: thalamus, hypothlamus
Diagram of the forebrain, name the 4 lobes
Frontal lobe
Temporal lobe
Parietal lobe
Occipital lobe
Diagram of the forebrain, what features allow division between the lobes
Central sulcus
Lateral fissure
How many layers does the cerebral cortex have
Divided into 6 layers
Thickness of layers correlates with function
Describe the different areas of the forebrain
Primary areas:
deal with a specific function.
Secondary areas:
integrate information from several sources and allows us to interpret signals.
Association areas:
control higher functions such as mood, personality and complex behaviour.
Describe the sensory and motor areas
Are both somatotopic (provide a map of the body)
What are the functions of the left hemisphere
Speech
Writing
Calculation
Language comprehension
Analytic thought processes
Language areas are in the left hemisphere in c 90% of the population
What are the functions of the right hemisphere
Spatial relationships
Conceptual non verbal ideas
General thought processes
