Disorders of Transmission Flashcards
what are the components of the CNS?
- cerebrum
- cerebellum
- brainstem
- spine
what are the components of the PNS?
- cranial nerves
- spinal / peripheral nerves
Components of the Peripheral nervous system (PNS) –> systems
- autonomic NS –> para / sympathetic NS
- somatic NS –> motor peripheral nerves / sensory peripheral nerves
What is the function of a neuron?
to generate and conduct electrical impulses which are used to communicate across the body
What do dendrites do?
receive info from other neurons & take it to soma
What is the nucleus of a neuron in?
cell body / soma
What does the axon do?
transmits info away from the nucleus
Components of a neuron?
- dendrites
- axon
- myelin
- soma
- pre- synaptic terminals
What are the types of neurons?
- multipolar
- bipolar
- unipolar
What is a multipolar neuron?
typical multipolar neuron
What is a bipolar neuron?
typical special sensory neuron
What is a unipolar neuron?
typical somatosensory neuron
Where are multipolar neurons situated mostly?
spine
Where are bipolar neurons situated mostly?
eyes & nose
Where are unipolar neurons situated mostly?
from periphery to spinal cord
Defining feature of a multipolar neuron?
dendrites attach to the soma
Defining feature of a bipolar neuron?
1 dendrite & 1 axon attached to soma
Defining feature of a unipolar neuron?
peripheral axon attaches to the central axon and the soma is ‘outside’ it. i.e. hangs off the axons
In the BRAIN - is grey matter or white matter lateral?
Grey
What is grey matter made up of in the brain?
neuronal cell bodies & dendrites
What is white matter made up of in the brain?
axonal bodies & myelin
In the BRAIN - is white matter lateral?
nah medial
Ganglia definition
collections of cell bodies OUTSIDE the CNS
Nuclei definition
collections of cell bodies WITHIN the CNS
What are the stages of AP propagation by neurons?
- resting potential
- slow depolarisation
- fast depolarisation
- repolarisation
- hyperpolarisation
What happens in the Resting Potential stage of AP propagation?
Voltage-gated Na+ and K+ channels are CLOSED
What happens in the Slow Depolarisation stage of AP propagation?
Local potentials summate to depolarise the membrane.
Voltage gated Na+ and K+ channels remain CLOSED
What happens in the Fast Depolarisation stage of AP propagation?
when the summation of local potentials (part B) reaches a threshold potential, voltage-gated Na+ channels OPEN and Na+ rushes in.
Membrane quickly depolarises to a positive membrane potential.
What happens in the repolarisation stage of AP propagation?
Voltage-gated Na+ channels = inactived.
Many voltage-gated K+ channels are OPEN, K+ exits, taking positive charges out of the axon
What happens in the hyperpolarisation stage of AP?
Voltage-gated K+ channels remain OPEN.
K+ continues to leave the axon, restoring the polarised membrane potential.
What is an AP?
electrical signals that propagate along axons
When does an AP result?
if the reduction of the resting membrane potential reaches threshold
What is myelin produced by in the PNS?
Schwann cells
What is myelin produced by in the CNS?
Oligodendrocytes
What does myelin do?
insulates & speeds up the conduction of the AP along the axon
Which areas of the axon does the AP jump to?
Node of Ranvier (areas between Myelin)
What happens at a synapse?
info = transmitted from one neuron to a another/ neuron to muscle
What is a neurotransmitter?
chemical released from an axon terminal
What does the neurotransmitter act on ?
postsynaptic membrane
What can neurotransmitters be?
- inhibitory
- excitatory
What is an EXCITATORY neurotransmitter?
binding of the neurotransmitter causes depolarisation of the post-synaptic membrane –> if threshold met, AP will generate –> INFO = PROPAGATED DOWN AXON
What is an INHIBITORY neurotransmitter?
binding of the NT causes further polarisation of the post-synaptic membrane –> membrane moves away from threshold and so reduces the chance of an AP occurring –> INFO STOPS
What is a CONVERGENCE neuron?
Can have multiple neurons converging with a single neuron (3 neurons into 1 neuron)
What is a DIVERGENCE neuron?
Single neuron synapses with multiple neurons (1 neuron into 3 neurons)
Are neuromuscular junction neurotransmitters excitatory or inhibitory?
ALWAYS EXCITATORY
What are the conditions that affect neurotransmission?
- Multiple Sclerosis
- Guillain-Barre Syndrome (GBS)
- Myasthenia Gravis
- Botulinum Toxin
What is Multiple Sclerosis?
oligodendrocytes destroyed –> signals travel slowly / dont make it to the end of the neuron
What is GBS?
schwann cells destroyed so signal doesn’t make it to end of axon
What type of conditions are Myasthenia Gravis (MG) and Botulinum Toxin?
synaptic dysfunction conditions
What happens in Myasthenia Gravis (MG)?
abnormal immune response leads body to destroy Ach receptors on muscle fibres @neuromuscular junction –> antibodies bind to Ach receptors
What happens in Botulinum Toxin (BTX)?
acts on vesicles holding Ach in pre-synaptic neuron and prevents Ach from being released –> no muscle fibre contraction