Nervous Tissue And Organisation Of The CNS, PNS, ANS And Sensory Networks Flashcards
Define the CNS and PNS
The nervous system can be divided into two parts:
- Central nervous system (CNS): Brain and spinal cord. Contains relay neurones
- Peripheral nervous system (PNS): Cranial nerves and spinal cord. Contains sensory neurones and motor neurone.
Describe the structure of grey and white matter
Grey matter is found in the peripheral in brain and in ‘nuclei’. They are where the nerve cell bodies are found. They also consist of: dendrites, axon terminals, non-myelinated axons, neuralgia (support cells). Grey matter has a ‘butterfly shape’ in spinal cord. Contain ventral and dorsal horns and are connected by grey commissure.
White matter is found in the central in brain and peripheral in spinal cord. They consist of myelinated material.
Describe the structure of a neuron
Neurones are a normal complement of cell organelles. They are cytoplasmic projections and contain many dendrimers with just one axon.
The main cell body (soma), dendrites and proximal part of the axon are within the CNS. Often coated in myelin.
In the CNS, the myelin is produced by and is part of an oligodendrocyte. In the PNS, the myelin is produced by and is part of a Schwann cell
What are the types of neurones
Motor - Location: CNS to periphery. Function: Sends signals to effector tissues
Sensory - Location: Periphery towards CNS. Function: Send environmental signals to integrative centre
Integrative - Location: CNS. Function: Collate all information.
Anaxonic - Location: Retina. Function: Act as relay
Pseudo unipolar, bipolar and postsynaptic auto mic neurone cell bodies are found outside CNS.
Purkinje and pyramidal cells are restricted to CNS. Many have elaborate dendritic aborisation
Explain neurotransmitter synthesis
1) Synthesis of neurotransmitter and formation of vesicles.
2) Transport of neurotransmitter down axon
3) Action potential down axon
4) Action
What are the different types of synapses
Axosomatic - Direct to plasma membrane of nerve or cell
Axodendritic - Axon terminal synapses with a dendritic spine
Axoaxonic - Synapse at the axon if bouton. Axoaxonic synapse may enhance/I hit axodendritic synsapse
Dendritic-dendritic - Found at back of retina
Axo-axonal - Impinging dendritic/axonal synapse usually inhibits other inputs
Explain the connective tissue layers found in peripheral nerves
All 3 nerve fibres found in peripheral nerves. Separated by connective tissue layers:
- Endoneurium: Loose connect tissue that surround single nerve cells/axon
- Perineurium: Specialised connective tissue - transport proteins. Maintains ionic composition and surrounds clusters of axons (fascicle)
Epineurium: Dense irregular connective tissue that separates different types of nerves and fill spaces between fascicles
Paraneurium: fascia that separates nerves from surrounding structures.
What is myelin and how does myelination occur.
CNS - Myelin produced by oligodendrocyte
PNS - Myelin produced by a Schwann cell
Myelination
1) Axon sits in groove surround by a Schwann cell
2) The mesaxon membrane initiate myelination by surrounding the embedded axon
3) A sheet-like extension of the mesaxon membrane then wraps successively around axon, forming multiple membrane layers.
4) Cytoplasm extruded from between two appointments plasma membranes of Schwann cell, which compacts forming myelin.
What are astrocytes and Microglial cells
Astrocytes have a star-like structure. They have perineural ‘feet’ that contain gap junctions, for biochemical support of nutrients (lactate) from blood to nerve cells. They regulate nerve impulses by releasing glutamate. They contribute to the blood-brain barrier.
Microglial cells - Large cells with elongated nucleus and fewer processes emanating from cell body. Found throughout CNS. There is a resident macrophage which has immune function, removes damaged nerve cells and sense increased potassium ions
Explain the function of Schwann cells and node of Ranvier
Schwann cells are a type of glial cell that surrounds neurones keeping them alive and sometimes coving them with a myelin sheath and are the major glial cell type in the peripheral nervous system.
Nodes of Ranvier are microscopic gaps found within myelinated axons. Their function is to speed up propagation of action potentials along the axon via saltatory conduction
Explain the role of glial cells
Identify nerve fibres in both cross section and longitudinal section
Explain the structure of the spinal cord in the transverse section and their histological features
Explain the structure of ependymal cells
Explain the symptoms, sign and causes of multiple sclerosis
