Flashcards in ToB 16 The Nervous System Deck (111)
How many pairs of cranial nerves does the human body possess?
How many pairs of segmental/spinal nerves does the human body possess?
What type of cell constitutes ~90% of the nervous system?
Glial cell (Glia)
Neuronal cells constitute what percentage of the nervous system?
What is the (greek) origin of the word 'glia'?
What is the main function of glia?
To bind and hold the neurones of the nervous system together
What type of embryonic tissue is microglia derived from?
Haemopoetic stem cells
What type of embryonic tissue is macroglia derived from?
How many types of macroglia are present in the CNS, and name them:
What is the name of the type of glia which causes the differentiation of the capillary endothelial cells in the brain, creating the blood-brain barrier?
What is the main function of Oligodendrocytes?
Myelination of neuronal axons
Why can the death of 1 oligodendrocytes have a very significant effect?
1 oligodendrocyte can myelinate up to 250 different axons at 1 time, so the death of that cell will ahve significant effects on the speed of conduction of many different axons.
What are the 4 types of glia present in the CNS:
What is the function of ependymal cells?
Line the ventriclar system of the brain and central canal of spinal cord, and is involved in production of cerebrospinal fluid.
Where are ependymal cells found?
Lining the ventricular system of the brain, and the central canal of the spinal cord
Which type of glial cell increases the speed of conduction of a nerve in the central nervous system?
Which type of glial cell lines the ventricular system of the brain?
Which type of glial cell line the central canal of the spinal cord?
What is the main function of microglia?
Immune cells of the central nervous system
Name the 2 types of macroglia present in the peripheral nervous system:
1) Schwann cells
2) Satellite cells
In the peripheral nervous system, how many axons can be myelinated by 1 glial cell?
What type of glial cell myelinates axons in the peripheral nervous system?
In the central nervous system, how many axons can be myelinated by 1 glial cell?
Up to 250 axons
What type of glial cell myelinates axons in the central nervous system?
What is the role of satellite glial cells?
Physically support neurones in the peripheral nervous system
What type of glial cell are present in both the cental and peripheral nervous systems?
What is the maximum number of cell bodies contained within a neurone?
1 cell body per neurone
What is the maximum number of axons that a neurone can have?
1 axon per neurone
What is the main function of neuronal dendrites?
To increase the surface area of the cell, in order to contact other cells.
What are the two necessary parts of a neurone?
1) Cell body
What structure do many neurones have to increase their surface area?
Name the different types of neuroglia:
5) Schwann cells
What is 'Nissl substance'?
The granular substance surrounding the nucleus in the cell body of a neurone, consisting of rER and free ribosomes, and is the site of protein synthesis.
What is contained within the cell body of a neurone?
- Nissl substance
- Golgi apparatus
What is the main function of the Golgi apparatus within the cell body of a neurone?
To package neurotransmitter into vesicles
What is the approximate size of a cell body of a neurone, in micrometres?
~ 4-120 um
What is the name of the membrane which prevents crystal violet dye from being taken up by the nucleus of a neurone?
What stain allows us to see the cell body of a neurone?
Crystal-violet (taken up by Nissl substance)
In unstained brain slices, why do cell bodies appear a different colour to the axon of a neurone?
Cell bodies contain high amounts of Nissl substance, which absorbs the light creating a grey colour,
Axons do not contain Nissl substance, so reflect the light appearing white.
Which part of the neurone contributes to the white matter of the brain tissue?
Which part of the neurone contributes to the grey matter of the brain tissue?
What is the name given to collections of cell bodies in the peripheral nervous system?
What does 'ganglia' mean?
used to describe cysts and raised nodes, also
collections of nerve cell bodies in peripheral nervous system
Where is the 'initial/initiation segment' of a neurone?
The first part of the axon leaving the cell body, is rarely myelinated, so the section between the cell body and the first myelin sheath is the initial/initiation segment
In what part of the neurone is an action potential created?
The initial/initiation segment
When an action potential is created in a neurone, why is it sent in 2 directions?
To the cell body to inform the cell, and
to the axon terminal to be passed onto another neurone/cell
What is the name of the axon membrane beneath a myelin sheath?
Why do thicker axons tend to conduct an AP faster than thinner axons?
Thicker axons tend to be myelinated, which increases the speed of conduction
Why does myelination affect the location of certain ion channels on an axon?
Voltage-gated Na+ channels only need to be present at nodes of ranvier when the axon is myelinated, rather than across the whole of the axon if unmyelinated
Name 3 polyneuropathy diseases which demyelinate neurons:
2) Multiple sclerosis
3) Guillain-Barré syndrome
What is the name of the thin unmyelinated axons which have a faster conduction velocity than if they were myelinated?
Where does depolarisation of a myelinated axon occur?
At the initial/initiation segment, and nodes of Ranvier
What is the approximate length of a node of Ranvier?
~ 1 um
What gives most nerves a reflective shiny whitish appearance?
What is the name of the connective tissue sheath which surrounds the individual nerve fibres of a peripheral nerve?
The connective tissue sheath which surrounds the individual nerve fibres of a peripheral nerve.
What is the name of the connective tissue sheath which surrounds a fascicle of nerve fibres within a peripheral nerve?
The connective tissue sheath which surrounds a fascicle of nerve fibres within a peripheral nerve
What is the name of the connective tissue sheath which surrounds a peripheral nerve?
The connective tissue sheath which surrounds a peripheral nerve
What is the name of the tough outermost meninges which surround the brain and spinal cord?
Define 'dura mater':
The toughest outermost meninges which surrounds the brain and spinal cord
How many meninges surround the brain and spinal cord?
Name the three meninges:
1) Pia mater
2) Arachnoid mater
3) Dura mater
What is the name given to the delicate middle meninges?
Define 'arachnoid mater':
The thin fibrous middle meninges which surrounds the brain and spinal cord,
What is the name given to innermost meninges?
Define 'pia mater':
The innermost meninges covering the brain and spinal cord
Which meninges are highly vascularised?
- Dura mater
- Pia mater
Which meninges is avascular?
The cell body of a neurone tends to swell and peripherally displace the nucleus if the axon of the neurone is damaged/cut. Why is this?
The cell body is undergoing rapid protein synthesis to begin axon regrowth
What is chromatolysis?
The disintegration of the granular Nissl substance within a neuronal cell body, usually occurring due to peripheral nerve damage
What is the meaning of the word 'afferent'?
Travelling towards a center
What is the meaning of the word 'efferent'?
Travelling away from a center
Define 'preganglionic neuron':
A neurone whose cell body lies within the CNS, and whose axon terminates at a ganglion in the peripheral nervous system, synapsing with postganglionic neurones
Define 'postganglionic neuron':
A neurone whose cell body lies within the autonomic peripheral nervous system
Is a sensory neurone afferent or efferent?
Is a motor neurone efferent or afferent?
Which structures encase the CNS?
By definition, are sensory neurones within or distinct from the CNS?
Distinct from the CNS
The autonomic nervous system can be split into which 3 components?
1) Sympathetic NS
2) Parasympathetic NS
3) Enteric NS
Is the enteric NS somatic or autonomic?
Define 'somatic nervous system':
The part of the nervous system which controls skeletal muscles under voluntary control
Define 'autonomic nervous system':
The part of the nervous system which works without conscious control
What is the effector organ of the somatic nervous system?
Which nervous system is inactivated during sleep?
Which nervous system is responsible for maintaining homeostasis in the body?
What are the 2 opposing systems within the autonomic nervous system?
What are the 4 types of effector organs stimulated by the autonomic nervous system?
1) Visceral organs
2) Smooth muscle
3) Cardiac muscle
4) Secretory glands
What type of neurone reaches from the CNS to a peripheral ganglion?
Pre-ganglionic neurone (afferent)
What type of neurone reaches from a peripheral ganglion to an effector organ?
Post-ganglionic neurone (afferent)
What type of neurones are always myelinated (in normal circumstances)?
What type of neurone is never myelinated (under normal circumstances)?
Which nervous system induces the 'fight or flight' response?
Sympathetic nervous system
What effect does the sympathetic nervous system have on heart rate?
It increases heart rate
The human vertebral column is split into which five segments? (In order from top to bottom)
In which segments of the vertebral column does the sympathetic nervous system have cell bodies in?
Pre-ganglionic sympathetic neurones all secrete which neurotransmitter?
Post-ganglionic sympathetic neurones all express what type of receptor?
Nicotinic Acetylcholine Receptors (NAchRs)
Post-ganglionic sympathetic neurones secrete which neurotransmitter? What is the exception?
Acetylcholine is released by the nerves innervating sweat glands
Where do most of the pre-ganglionic sympathetic neurones (efferent) synapse?
What are the 2 classes of adrenoceptors?
What name is given to the receptors which respond to adrenaline?
What effect does the parasympathetic nervous system have on heart rate?
Reduces heart rate
Which branch of the autonomic nervous system promotes digestion?
What part of the CNS does the parasympathetic pre-ganglionic nerves arise from?
Sacral region of spinal cord
Which branch of the autonomic nervous system has long pre-ganglionic nerves?
Which branch of the autonomic nervous system has short pre-ganglionic nerves?
Which branch of the autonomic nervous system has long post-ganglionic nerves?
Which branch of the autonomic nervous system has short post-ganglionic nerves?