Gross Organisation and Anatomy of Nervous System Flashcards
What are the gross structural features of the nervous system?
Brain Spinal Cord Nerves - Cranial (12 Pairs) - Spinal (31 Pairs) Cavities Blood vessels Membranes encasing soft tissues Bones - Cranium/Skull - Vertebral column
How can you classify the nervous system?
Central nervous system
- Covered in meninges
- Complex
- Adaptable
- (Brain + Spinal Cord)
Peripheral nervous system
- Covered in endoneurium, perineurium and epineurium
- Less sophisticated in functional capacity
- Dependant on CNS
Why is it important to distinguish between CNS and PNS?
Because diseases can affect the different systems, so it is important to know the origin of the disease.
Name some diseases of the CNS
Raised intracranial pressure Multiple Sclerosis Affective disorders Alzheimer's Parkinson's
Name some characteristics of the CNS in relation to disease and damage.
No capacity to regenerate (currently)
Plasticity allows for some limited re-organisation
Susceptibility to advancing age
Name some diseases of the PNS and a characteristic of the PNS related to disease.
Nerve compression syndromes
Demyelinating polyneuropathies
Capacity to regenerate after injury
What is the clinical importance of tumours of the nervous system?
All PNS tumours are benign
Tumours of neurones in CNS are not malignant
Malignant tumours are a feature of Glia only.
What are the different cell types of the nervous system?
Neurones (10%
Neuroglia (or glia) (90%)
What is the basic structure of a neurone?
Some have dendrites that connect to the
Cell body which has an
Axon coming off of it which ends in an
Axon terminal
Describe gross structure of the brain.
Cerebral hemispheres (large tubey stuff) Thalamic masses Brainstem - Midbrain (top part) - Pons (bulb part/mid part) - Medulla (bottom part) Cerebellum (wrinkly part at the back) Cavities - ventricles - Lateral (first two, big spaces in centre / C-shaped) - 3rd ventricle (in-between the lateral, bit lower) - 4th ventricle (space behind brainstem, in front of cerebellum)
What is the significance of having two halves to a brain?
There is lateralisation of function with respect to some modalities
Some modalities are represented bilaterally with one side more dominant
- Speech, handedness, attention
The implications are that strokes can have different outcomes depending on the side of the brain it affects
What are the lobes of the cerebral cortex?
Many lobes
4 major lobes: (from front to back)
Frontal lobe
Parietal (superior to temporal)
Temporal (inferior to parietal)
Occipital
What is the gross structure of the spinal cord?
It is a continuation of the medulla
Cylindrical (approx.) in shape
Somewhat flattened from front to back
Gross shape changes from rostral to caudal
Shows two enlargements at cervical and lumbar levels
Ends in taper - The Conus Medullaris
- Filum terminale and Denticulate Ligaments
It has a central cavity throughout its length
Describe the appearance of the adult brain.
Shows mostly the cerebral cortex: Highly convoluted Convolutions consist of: - Grooves or depressions known as Sulci - Major sulci are known as Fissures -Ridges or elevations known as Gyri
Large Sulci are invariable between individuals and are used as important landmarks in brain mapping for surgery
Can also see cerebellum at back
and some brainstem
What divides the cerebral cortex into two?
Longitudinal fissures + Flax cerebri (Dura mater)
Hemispheres are normally interconnected by the corpus callosum and Commissures (anterior and posterior)
What is meant by the vesicles of the brain?
Segments of the brain more easily seen from medial aspect. They are visible from embryonic stages Initially three are seen - 3 Primary vesicles 2 additional others appear later - 5 secondary vesicles
Name the vesicles of the brain.
Forebrain
- Telencephalon (cerebrum)
- Diencephalon (centre of brain with the big space)
- containing the epithalamus, thalamus, hypothalamus,
and ventral thalamus and the third ventricle.
Midbrain
- Mesencephalon
Hindbrain
- Pons
- Medulla
What are the meninges of the brain?
They are membranous envelopes that completely cover the brain
They consist of three connective tissue layers:
- Dura mater (2 layers)
- Periosteal layer of dura mater
- Meningeal layer of dura mater
- Arachnoid mater
- Pia mater
They are continuous with the spinal cord
(dura mater is a single layer in the spinal chord)
What are the functions of the meninges of the brain?
They support and mechanically stabilise contents of the cranium
They act as “seatbelts” of the cranium
They organise (or divide) the cranial cavity into anatomical compartments
What are the anatomical spaces associated with the meninges?
(inner layer of cranium) Extradural space (dura mater) Subdural space (arachnoid mater) Sub-arachnoid space (pia mater)
What is the importance of the sub-arachnoid space?
Blood vessels are found within the subarachnoid space
- Arterial - site for intercranial bleeds
It is filled with cerebrospinal fluid (CSF)
What are some functions of CSF?
Bathes the brain
Cushions the brain against mechanical agitation
It is a reservoir for metabolic substrate for the brain
It dissolves and carries away products of metabolism from the brain
What is the significance of the brain and it’s blood supply?
The brain makes up 2% of body weight but receives 15% of cardiac output
Vasculature is intricate and substantial (400 miles)
Vasculature has ability to auto-regulate perfusion of the brain tissue
There is a blood brain barrier between the blood supply and the cells of the brain
