Cell and tissues of the nervous system Flashcards
Cell types
- Neurons
- Structural and functional unit
- Excitable cells
- Impulses carried as action potentials
- Glial cells
- Non-excitable supporting cells
- Much smaller than neurons
- Non-excitable supporting cells
Whats the divisions of the nervous system
What describes a typical neuron
Multiple dendrites, one axon
- Nucleus- loose chromatin, prominent nucleolus
- Cell organelles - Mitochondria, rER (Nissl bodies bodies), diffues Golgi apparatus
- High metabolic rate
- Cytoplasm in the cell body is perikaryon, and in the axon is axoplasm
- Long living and amitotic
Impulse transmission is by action potential which can travel:
In only one direction from cell body to synaptic terminal
Types of neurons
Axons and their envelopes
- Myelin sheath: Increse conduction speed in axons by ‘saltatory conduction’
- Depending on presence or absence of myelin sheath, neurons may be:
- Myelinated neurons
- Non-myelinated neurons
- Myelin sheath formed by:
- Schwann cells in PNS
- Oligodendrocytes in CNS
Clinical importance of the myelin sheath: Multiple Scelrosis (MS)
- Patchy loss/scarring of myelin sheath (demyelination)→ nerve conduction across affected axons abnormal
- Idiopathic
- MRI shows whitish plaques of demyelinatiion
- Prognosis variable
- Scotland has the highest incidence in the world
White matter
Myelinated axons
Grey matter
Neuronal cell bodies
Spinal cord histology
Spinal cord diagram
Cell types glial cells
Blood Brain Barrier
Is a protective mechanism that helps maintain a stable environment for the brain and prevents harmful amino acids & ions present in the bloodstream and blood cells from entering the brain.
BBB is absent in a few ‘circumventricular’ organs: parts of hypothalamus, posterior pituitary.
Plays a major role in drug delivery to CNS. Drugs have to be lipid soluble or use suitable vectors.
Cerebrum
Seat of consciousness
Cerebellum
Balance and coordination
Brain stem
Vital centres eg: cardiorespiratory, Pathway for fibre tract
Midbrain
Pons
Medulla
Ventricles
- The lateral ventricles are C-shaped cavities which lie in the cerebral hemispheres.
- The interventricular foramen connects them with the 3rd ventricle – the cavity within the diencephalon.
- The cerebral aqueduct lies in the midbrain.
- The diamond-shaped 4th ventricle lies in the hindbrain
- Within cerebral hemispheres (x2) = lateral ventricle (x2)
- Within Diencephalon = III ventricle
- Within Midbrain = Cerebral aqueduct
- Between Pons + medulla (in front) and Cerebellum (at the back) = IV ventricle
Meninges - 3 coverings of the CNS
- The dura mater is tough, fibrous and has dural folds.
- The pia mater is vascularised and dips into the folds of the brain.
- The subdural space is a potential space which is traversed by blood vessels penetrating into the CNS
- The subarachnoid space contains cerebrospinal fluid.
Cerebrospinal fluid (CSF)
- Is the fluid inside the cavity of brain (ie the ventricles) and central canal of spinal cord.
- Is to some extent responsible for the maintenance of the “intracranial pressure”
- Is also present surrounding the brain and spinal cord in between the layers of meninges which are coverings of the brain (between the pia and arachnoid)
CSF- what you need to know
Where’s it present?
Ventricles
Where is it formed?
Choroid plexus
Where is it absorbed?
Arachnoid villa
How does the CSF circulate?
Enters subarachnoid space
Choroid plexus
Ventricles are
Spaces in brain containing CSF
How are neurons organised
Into grey matter, nucleii, ganglia, white matter, fibre tracts and peripheral nerves
Types of cells in NS
Neurons and Glial cells
NS divided into
CNS
PNS
