Flashcards in ToB - Neurones, Nerves And ANS Deck (34):
What makes up the gross nervous system?
1). The brain and its 12 pairs of cranial nerves and the spinal cord and its 31 pairs of spinal nerves.
2). The brain, spinal cord and nerves.
What are the meninges made of and what order do they go in?
What form the leptomeninges and what is their function?
The arachnoid mater and pia mater.
Cerebrospinal fluid flows in between them.
What is CSF formed by and what is its function?
Formed by the choroid plexus of the arteries. It takes nutrients and O2 to the neurones of the CNS and removes waste. It also exerts CSF pressure.
What is nissl substance and what does it contain?
It is found inside a neurone cell body. It has aggregations of RER and many golgi to be able to synthesise and package neurotransmitters.
What type of neurone are dendrites normally found on?
What are spines of a dendrite linked to?
These are linked to the ability to learn.
What are the 2 classes of dendrite and their function?
Function is to increase s.a. For which an input can be received.
Proximal - a dendrite stems from the axon body
Distal - a dendrite stems from another dendrite
How can the arrival of an input at a dendrite be summated?
Temporal summation - with respect to the time it arrived (how many times the axon fired)
Spatial summation - with respect to where on the neurone the input arrived (how many axons fired at that one neurone together)
What is the function of the nodes of ranvier on an axon?
1). Allow nutrients in and out of the axon between myelination
2). Allows saltatory conduction of the impulse via de/repolarisation = much quicker
What is the axonal hillock?
It isn't always present but it is where the action potential summated from and fires down the axon (often at the base of the cell body)
What is the effect of demyelination of an axon and what disorder does this occur in?
No saltatory propagation can occur = much slower transmission of impulse.
Occurs in MS where myelinated tissue is replaced by scar tissue
What are the usual neurotransmitters released at excitatory synapses?
Glutamate and aspartate
What are the usual neurotransmitters released at inhibitory synapses?
GABA and glycine
What are the 3 ways in which synapses can occur?
1). Lightly - 1 to 1
2). Diverge - 1 to 10
3). Converge - 10 to 1
What are the 3 neurone types and their structure?
1). Multipolar - 2 or more dendrites, one axon
2). Bipolar - 1 dendrite, one axon
3). Uni/pseudopolar - no dendrites, one axon
What glial cells are present in the CNS and what is their function?
Oligodendrocytes - myelination
Astrocytes - form blood brain barrier and transport nutrients and waste
Microglia - immunity and inflammation
Ependyma - line centre of spinal cord for CSF circulation
Where do the sympathetic nerves flow through?
The spinal cord only
Describe the pre and post ganglion if neurones in the sympathetic nervous system.
Preganglionic - short, secretes acetyl choline
Postganglionic - long, secretes noradrenaline and contains nicotinic receptors
In what sections of the spinal cord is the sympathetic nervous system found?
12 in thorax division
2 in lumbar division
What forms the lateral horn in the spinal cord?
Collections of preganglionic cell bodies
What do effector organs in the sympathetic nervous system contain?
Alpha and beta adrenoreceptors (a1, a2, b1, b2).
They can both exhibit pre synaptic inhibition of each other.
How can termination at the ganglion occur in the sympathetic nervous system?
It occurs next to the vertebral column in paravertebral chain.
May not synapse at this chain
May synapse at the level corresponding to the level the preganglionic neurone originated.
May synapse at a different level to the origin
How does an impulse travel from the spinal cord?
Preganglionic neurone cell bodies in grey matter of spinal cord.
Travels down that to paravertebral chain.
Stimulates postganglionic neurone (ganglion in the paravertebral chain)
Travels to an effector
In the autonomic nervous system, which neurones are myelinated and unmyelinated?
The preganglionic neurone is myelinated, postganglionic is unmyelinated
How are organs innervated by the ANS?
Most organs are innervated by both the SNS and PNS, but sweat glands are sympathetic only.
The overall ANS tone is decided by the balance of input.
Where do the parasympathetic neurones flow?
Through the brain and spinal cord.
In what division is the parasympathetic nervous system?
Describe the neurones in the parasympathetic nervous system.
Preganglionic - long and secrete acetyl choline
Post ganglionic - short and secrete acetyl choline. Also express nicotinic receptors in the walls of effector organs.
What do effector organs express in terms of receptors?
They express muscarinic receptors.
These can be blocked by poisons such as atropine.
What happens if the PNS is overactive and what may cause this?
Dilation of blood vessels = over time, there is a shortage of blood to the brain as it is constantly sent to the GI tract.
Can be caused by certain infections.
What can an overactive SNS result in?
Constriction of blood vessels and therefore less blood to the peripheral tissues = extremities become gangrenous and die
What functions can the SNS do?
Reduce blood flow to GIT, skin etc to redirect to the heart