Cells and Tissues of the Nervous System Flashcards
what are the divisions of the nervous system?
PNS and CNS
then sensory (afferent) division and motor (efferent) divison
then motor division into somatic and autonomic
then autonomic into sympathetic and parasympathetic
what forms the CNS?
Brain and spinal cord
what forms PNS?
cranial and spinal nerves
what are the different cell types of the nervous system?
Neurons
Glial cells
how would you describe neurons?
Structural and functional unit
Excitable cells
Impulses carried as action potentials
how are a neurons impulses carried?
as action potentials
how can glial cells be described?
Non-excitable supporting cells
Much smaller than neurons
how does the size of glial cells compare to neurons?
Glial cells are much smaller
How many dendrites and axons does a typical neuron have?
multiple dendrites and one axon
how would you describe impulse transmission of a ap in a typical neuron?
in only one direction from cell body to synaptic terminal
what are dendrites?
Branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation towards the cell body (also known as soma)
what is an axon?
Long threadlike part of a nerve cell along which impulses are conducted from the cell body to other cells
what is a dendrite stimulated by?
the environmental changes or activities of other cells
what does the cell body of a neuron contain?
nucleus, mitochondria, ribosomes and other organelles/inclusions
describe the organelles within a neuron?
Mitochondria, rER( Nissl bodies), diffuse Golgi apparatus.
what is the metabolic rate of a neuron?
High metabolic rate
what are the cytoplasms in the cell body and axon known as?
Cytoplasm in the cell body is perikaryon, and in the axon is axoplasm.
how would you describe a neurons nucleus?
loose chromatin, prominent nucleolus
What direction does the impulse travel in the multipolar and in the pseudounipolar neuron?
dendrite to cell body in multipolar
In a pseudounipolar it goes through the dendrite, but then bypasses the cell body going straight, straight down the axon.
Where does the cell body of the multipolar neuron lie?
within the CNS
what about the location of the dendrite, cell body and axon of the pseudounipolar neuron?
These are what form the dorsal root ganglia of spinal nerves and they similarly form ganglia of cranial nerves, like, for instance, the trigeminal nerve has a trigeminal nerve ganglion, which sits just on either side of the pituitary fossa. So these ganglia are nothing but where the cell bodies of these sensory pseudounipolar neurones lie.
what are the three different types of neurons?
multipolar
pseudopolar
bipolar
what neurons are multipolar?
inter-neurons
motor-neurons
what neurons are bipolar?
olfactory mucosa
retinal nerve fibres
what neurons are pseudounipolar?
sensory neurons
What is amitosis?
Cell proliferation that does not occur by mitosis
Cell proliferation that does not occur by mitosis
Long living and amiotic
what is the function of the myelin sheath?
Increase conduction speed in axons by ‘saltatory conduction’
What is saltatory conduction?
Propogation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of the action potential
depending on the presence of the myelin sheath, what can neurons be?
Myelinated neurons
Non-myelinated neurons
What is the myelin sheath formed by in the CNS?
Oligodendrocytes
What is the myelin sheath formed by in the PNS?
Schwann cells
What are nodes of Ranvier?
Microscopic gaps found within myelinated axons, the function is too speed up the propagation of action potentials along the axons via saltatory conduction
What is an example of a condition that demonstrates the clinical important of the myelin sheath?
Multiple sclerosis (MS)
What is MS?
Patchy loss/scarring of mmyelin sheath, leads to nerve condiction across affected axons being abnormal
What is the cause of MS?
Unknown, potentially viral or autoimmune
What does an MRI show when investigating MS?
White plaques of demyelination
where in the world has the highest incidence of MS?
Scotland has the HIGHEST incidence in the world
what does white matter of the spinal cord contain?
myelinated axons
what does grey matter of the spinal cord contain?
neuronal cell bodies
What are some of the nerve tracts present in the spinal cord?
Ascending tracts
Descending tracts
Spinothalamic tract
Spinoreticular tract
Dorsal spinocerebellar tract
Ventral ispinocerebellar tract
Lateral corticospinal tract
Ventral corticospinal tract
Retrospinal tract
What are multipolar neurons?
Neuron that possesses a single axon and many dendrites allowing for integration of a great deal of information from other neurons
What are bipolar neurons?
Has two extensions (one axon and one dendrite)
They are specialised sensory neurons for the transmission of sense so are used for smell, sight, taste, hearing, touch, balance and proprioception
What are pseudounipolar neurons?
Kind of sensory neuron, contains one axon that has split into two branches where one travels to the periphery and one to the central nervous system
What are glial cells?
Surround neuron and provide support for insulation between them
What glial cells are present in the PNS?
Satellite cells
Schawnn cells
What is the function of satellite cells?
Surround neuronal cell bodies
What is the function of Schwann cells?
Myelination
What glial cells are present in the CNS?
Epidymal cells
Astrocytes
Oligodendrocytes
Microglia
What is the function of epidymal cells?
Line ventricles
What is the function of microglia?
Phagocytosis
Scar tissue formation
What is the function of oligodendrocytes?
Myelination
What is the function of astrocytes?
Surround synapses, capillaries, and help in K+ buffering
What is the blood brain barrier (BBB)?
Protective mechanism that helps to maintain a stable environment for the brain and prevent harmful amino acids and ions present in the bloodstream and blood cells from entering the brain
What forms the blood brain barrier?
Endothelium (tight junctions)
Thick basal lamina
Foot processes of astrocytes
What are circumventricular organs?
Structures in the brain characterised by their extensive and highly permeable cappilaries, unlike those in the rest of the brain protected by the BBB
What are some circumventricular organs where the BBB is absent?
Parts of the hypothalamus
Posterior pituitary
Pineal gland
What does the existence of circumventricular organs play a major role in?
Delivery of drugs to the CNS, which must be lipid soluble or use suitable vectors
What must drugs be to reach the CNS?
Lipid soluble of use suitable vectors
identify cerebrum, cerebellum, brainstem, diencephalon?
what is the function of the cerebrum?
Seat of consciousness
what is the function of the cerebellum?
Balance and coordination
what is the function of the brainstem?
Vital centres eg: cardiorespiratory,
Pathway for fibre tracts
what is the function of the diencephalon?
The diencephalon is involved in many crucial bodily functions including coordinating with the endocrine system to release hormones, relaying sensory and motor signals to the cerebral cortex, and regulating circadian rhythms (the sleep wake cycle).
What are the 3 parts of the brainstem?
Midbrain
Pons
Medulla
What is found in the brainstem?
Vital centres such as cardiorespiratory
Pathway for fibre tracts
What are some ventricles in the brain?
Lateral ventricles
III ventricle
Cerebral aqueduct
IV ventricle
What are ventricles?
Cavity or chamber that can be filled with fluid, such as the cerebral ventricles or heart ventricles
Where are the lateral ventricles found?
C-shaped cavities which lie in the cerebral hemisphere
What are the lateral ventricles connected by?
Interventricular foramen
Where is the cerebral aqueduct found?
Midbrain
Where is the IV venticle found?
Hindbrain (between pons and medulla in front and cerebellum at the back)
Where is III ventricle found?
Within diencephalon - the cavity within the diencephalon.
What are the meninges?
Membranous coverings of the brain and spinal cord
What are examples of structures that protects the brain?
Dural folds
Scalp
Skull bones
Meninges
What are dural folds?
The dural seperates into two layers at dural reflections which are known as dural folds
What are the 3 layers of the meninges?
Dura mater
Arachnoid mater
Pia mater
How can the dura mater be described?
Tough, fibrous layer
What layer of the meninges is vascularised?
Pia mater
What is the space called between the dura and arachnoid mater?
Subdural space
What is the subdural space?
Potential space which is traversed by blood vessels penetrating into the CNS
What is the space between the arachnoid and pia mater?
Subarachnoid space
Where is cerebrospinal fluid found?
Subarachnoid space
What is cerebrospinal fluid (CSF)?
Fluid inside the cavities of the brain (ventricles) and central canal of the spinal cord
What, to some extent, is CSF responsible for the maintenance of?
Intracranial pressure
Where is CSF formed?
By choroid plexus in each ventricle
Where is CSF absorbed?
By arachnoid villi into saggital sinus (venous channel in brain)
Explain the process of the circulation of CSF?
1) Beginning in the lateral ventricle flows through two passages into the third ventricle
2) Flows down the aquaduct of Sylvius into the fourth ventricle
3) Passes through three small openings (foramina) into the subarachnoid space
4) Absorbed through blood vessels over the surface of the brain back into the blood stream
5) Carried away and filtered by kidneys and liver
What channel does CSF flow from III ventricle to IV ventricle through?
Aquaduct of Sylvius
Is grey or white matter found on the inside of the spinal cord and brain?
Spinal cord - Grey matter, white on the outside
Brain - white amtter, grey on the outside
