ToB S9 - Nerves Flashcards
Describe the structure of a peripheral nerve
- Cell body with nucleus, dendrites, nissl substance
- Axon Hillock
- Myelinated axon with Schwann cells and Nodes of Ranvier, Terminal buttons
What is an efferent nerve fibre?
Transports signals from the CNS to effectors Motor neurones
Which cells maintain myelination in the CNS and in the PNS?
CNS - Oligodendrocytes (1 cell per 250 axons)
PNS - Schwann cells (1 cell per axon)
What are the nodes of Ranvier?
- Gaps in the myelination of an axon
- Enable saltatory conduction
What are the three types of connective tissue sheaths found in the nervous system?
Epineurium - Covers entire nerve
Perineurium - Covers fascicles of nerve fibres
Endoneurium - Covers single cell axons
What are the consequences of demyelination?
Action potential must travel further along the axon as saltatory conduction is inhibited so action potential cannot jump between nodes of Ranvier
What makes up a neurone?
Axon, cell body, dendrites
Can be uni-polar (sensory), bi-polar (retina of eye) or multi-polar (majority)
What is white and grey matter?
White - axons
Grey - cell body
Describe the features of a nerve cell body
Nissl substance, nucleus, nucleolus, dendrite
What is the role of glial cells?
Support neurones, maintains homeostasis and form myelin/insulate neurones
List the glial cells found in the CNS, PNS and both
CNS - astrocytes, oligodendrocytes
PNS - Schwann cells, satellite cells
Both - microglia
Where are myelinated and unmyelinated neurones found?
Myelinated - Somatic
Both - Autonomic
What are ganglia?
Collections of nerve cell bodies in the PNS (swelling)
What two reciprocal components make up the autonomic nervous system?
Sympathetic and parasympathetic system
What are effectors of the ANS
Smooth muscle, cardiac muscle, glands, visceral organs
List the functions of the sympathetic NS
Involved in fight or flight response mechanism
- Increase heart rate
- Increase blood pressure
- Divert blood to muscles and heart
- Hyperventilation
List the functions of the parasympathetic NS
Involved in the resting state
- Promotes sleep
- Promotes digestion
- Promotes normal bodily functions such as bladder emptying
- Reduced heart rate and force of contraction
What neurones and receptors are involved in the sympathetic NS ?
Pre-ganglionic neurone - Cholinergic
Post-ganglionic receptors - nicotinic
Post ganglionic neurone - noradrenergic
What type of neurotransmitter and receptors are involved in the parasympathetic NS?
Pre-ganglionic neurone - Cholinergic
Post-ganglionic receptors - nicotinic
Post ganglionic neurone - cholinergic
What do excitatory and inhibitory neurones release?
Excitatory- glutamate/aspartate neurotransmitter
Inhibitory- glycine/GABA neurotransmitter
What function do astrocytes have?
- Make up the blood brain barrier
- Assist in transfer of nutrients and waste
What function do oligodendrocytes have?
Myelination of the central nervous system, myelinating up to 250 axons/cells
What function do microglia have
Immune and inflammatory functions
