Nervous System Flashcards
Define multipolar, unipolar and bipolar neurones
- MULTIPOLAR have 1 axon and MULTIPLE dendrites
- BIPOLAR have 1 axon and 1 dendrite
- UNIPOLAR have 1 axon and NO dendrites
Describe the arrangement of neurones in a nerve
- Single axons bundled together surrounded ENDONEURIUM
- Multiple bundles of axons form fascicles surrounded by PERINEURIM
- Multiple fascicles make up nerves surrounded by EPINEURIUM
Describe the structure of a myelinated neurone axon and how this relates to function
- Contains SCHWANN CELLS wrapped around multiple times forming a MYELIN SHEATH
- Discontinuous sheath which is separated by gaps called NODES OF RANVIER
- Nodes allow speedy transmission of action potentials via SALTATORY CONDUCTION
Describe the myelination of cells of the PNS and CNS
- Cells of PNS are myelinated by SCHWANN CELLS
- Cells of CNS are myelinated by OLIGODENDROCYTES
Are the nerve cells of the somatic nervous system myelinated?
- YES
- Myelination allows speedy conduction of action potentials to stimulate voluntary skeletal muscle contractions
What neurotransmitters are released from excitatory and inhibitory neurones respectively?
- EXCITATORY neurones release GLU/ASP neurotransmitters
- INHIBITORY neurones release GLY/GABA (gamma-aminobutyric acid) neurotransmitters
How does demyelination of neurones lead to a decrease in conduction velocity?
DECREASED SALTATORY PROPAGATION OF ACTION POTENTIALS so impulse has further to travel
Describe the pathophysiology of multiple sclerosis
- DESTRUCTION OF MYELIN SHEATH of axons which is replaced by SCAR TISSUE
- Damage to oligodendrocytes and axon
- SALUTATORY PROPAGATION CANNOT OCCUR and scar tissue does not permit conduction so renders the axon useless
Describe the components of a nerve cell body
- Nucleus
- Nucleolus
- Dendrites (some)
- NISSL SUBSTANCE (aggregations of RER)
- Golgi body
Explain the function of Schwann cells and the nodes of Ranvier
- Schwann cells are lipid laden and wrap around the axon INSULATING it
- Schwann cells CANNOT CONDUCT action potentials due to their lipid content
- Gaps between Schwann cells allow transmission of action potentials via SALUTATORY PROPAGATION at nodes of Ranvier
Explain the roles of glial cells
- SUPPORT NEURONES
- Maintain homeostasis
- FORM MYELIN SHEATH which insulate the axons
What is the role of oligodendrocytes?
GLIAL CELLS that are involved in MYELINATION of axons (up to 250 axons per cell)
What is the role of MICROGLIA?
IMMUNE AND INFLAMMATORY FUNCTIONS of both CNS and PNS
What is the role of astrocytes and where are they located?
- Form the BLOOD-BRAIN BARRIER in CNS
- Assist in the transfer of nutrients and waste
Name 3 types of glial cells present in the CNS
- Astrocytes
- MICROGLIA (also in PNS)
- Oligodendrocytes
What is a ganglion?
Swelling on nerve fibre formed from a collection of many nerve cell bodies in the PNS
Describe the structure of the nervous system
- Nervous system split into CNS and PNS
- PNS split into SOMATIC (voluntary) and AUTONOMIC (involuntary)
- AUTONOMIC split into SYMPATHETIC and PARASYMPATHETIC
What is the difference between grey and white matter of the CNS?
- Grey matter consists mainly of NERVE CELL BODIES (dark staining nuclei)
- White matter consists mainly of AXONS (light staining myelin)
How do Schwann cells associate with the axon?
- Wrap around the axon 100s of times to provide INSULATION
- 100μm in length separated at 1μm intervals known as NODES OF RANVIER which allows saltatory conduction of action potentials
What is the difference between a sensory neurone and a motor neurone?
- Sensory neurones carry signals FROM CNS TO TISSUES
- Motor neurones carry signals FROM TISSUES TO CNS
What is the difference between a pre-ganglionic and post-ganglionic neurone?
- PRE-GANGLIONIC neurones are immediately PROXIMAL TO GANGLION
- POST-GANGLIONIC neurones are immediately DISTAL TO GANGLION
What is the role of the autonomic nervous system?
- INVOLUNTARY CONTROL OF THE PNS including control of respiratory, cardiac, GI, urogenital and thermoregulatory systems
- MAINTAINS HOMESTASIS
Describe the layout of the autonomic nervous system
- 1 neurone in the CNS known as a PRE GANGLIONIC NEURONE which originates from the spinal cord
- 1 neurone in the PNS known as a POST GANGLIONIC NEURONE which connects to the EFFECTOR
Describe the neurotransmitter use of pre and post ganglionic neurones
- Pre-ganglionic neurones are CHOLINERGIC so use acetylcholine
- Post-ganglionic neurones are NORADRENERGIC so use noradrenaline
