Lecture 10 : Nerve 3 Flashcards
What are opioids?
Weak: codeine, tramadol
Strong: morphine, fentanyl
Used for: pain modulation, useful analgesics; reward systems - addictive
What are ionotropic receptors?
- Faster
- The ion channel is the receptor - neurotransmitter binding to the receptor opens the channel, ions flow across membrane
Give 3 examples of ionotropic receptors and their neurotransmitter:
- Acetylcholine - nicotinic receptors (mostly Na+ channels)
- Glutamate - AMPA/NMDA receptors
- GABA - GABA receptors (mostly Cl- channels)
What are metabotropic receptors?
- Slower
- Neurotransmitter binds to receptor
- Activates intracellular signalling pathway (cAMP)
- Triggers ion channels or cellular processes/gene transcription
Give 4 examples of metabotropic receptors:
- Dopamine - dopamine receptors
- Noradrenaline - adrenergic receptors
- Glutamate - metabotropic glutamate receptors
- Acetylcholine - muscarinic receptors
What is the difference between chemically-gated and voltage-gated ion channels?
Chemically-gated:
- Local potentials
- Graded - stronger stimulus will open more channels, will lead to greater depolarisation
- Dendrites – Cell body
Voltage-gated:
- Action potentials
- All or nothing
- -60mV open, +30mV closed (Na+ channels)
- Axon hillock -> axon -> axon terminals
What is the puffer fish toxin and what does it do?
Tetrodoxin (TTX)
- Blocks voltage-gated ion channels
What is the function of analgesia?
- Pain control for patients with chronic neuropathic pain without improvement to other treatments - Lidocaine or bupivacaine
- Reversible blockage of voltage-gated Na+ channels at the injection site
- Intra-articular injection (in the joint) of lidocaine immediately before a physiotherapy session relieves pain during stretching and mobilization of the affected joint, enhancing the treatment effect
What are glial cells?
Support cells
* Astrocytes
* Microglia
* Ependymal cells
* Oligodendrocytes
* Schwann cells
What are the functions of astrocytes?
- Maintain ion balance
- Supply nutrients
- Blood brain barrier
- Ensheath capillaries
- Nerve growth
What are the functions of microglia?
- Immune cells of CNS
- Engulf and destroy microorganisms
- Brain development
What are the functions of oligodendrocytes?
- Support the nerves
- Ensheath CNS nerves with myelin
What is the function of schwann cells?
- Ensheath peripheral nerves
What are many neurological disorders caused by?
An imbalance in supporting cells of the nervous system
Describe the development of the nervous system:
- Cells start as stem cells- undifferentiated, able to divide, form all neurons and glia cells
- Not lost in adults , but capacity drops significantly with age
- From 1-3 years many neurons are formed
- Then connections are strengthened, or refined by apoptosis programmed cells
- Only specific brain regions have a few remaining stem cells - limited replace/repair capacity
How is the direction of axon growth determined?
Chemotaxis and durotaxis (mechanical) from astrocytes, microglia and effector cells
What structures do developing axons have?
Growth cone with filopodia
Describe the adaptation of the nervous system:
When stimulation lasts hours to days:
- Hyperresponsiveness – long term potentiation (LTP)
When inhibition lasts hours to days:
- Hyporesponsiveness – long term depression (LTD)
Multiple postsynaptic mechanisms
Describe the repair of motor neurons:
Injury: Crushing and bruising of nerves due to blunt trauma or surgical procedures
1. Nerve regeneration: If not extensive damaged, the peripheral nerve can repair itself via axonal sprouting and guiding by the Schwann cells
2. A muscle fibre that will no longer be innervated will atrophy (and can eventually die)
