Introduction to neuroanatomy
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What is the fundamental function of the nervous system?
To detect changes in the internal and external environments and generate appropriate responses in muscles, organs and glands.
What four functions dominate the nervous systems of relatively primitive organisms?
Homeostasis, response to threats, finding food and mating.
What additional capabilities evolved in higher nervous systems?
Learning, memory, cognition, self-awareness, intellect and personality.
Why is the human brain considered unique in evolution?
It is the most complex and versatile product of evolution.
Why is neuroanatomy important clinically?
It allows correlation of nervous system structure with neurological function and dysfunction.
What types of processes can damage the nervous system?
Developmental abnormalities, inherited disorders, disease, trauma, metabolic disorders and neurodegeneration.
What organisation publishes the Terminologia Anatomica?
The Federative International Programme on Anatomical Terminology.
Why do many neuroanatomical structures have unusual names?
Many are derived from Latin and describe shape, colour or historical observations.
What does hippocampus mean?
Sea horse.
What does substantia nigra mean?
Black substance.
What is an eponym in neuroanatomy?
A structure named after a person associated with its discovery or description.
Give two examples of neuroanatomical eponyms.
Circle of Willis and foramen of Monro.
What are the three standard anatomical planes?
Sagittal, transverse (horizontal) and coronal.
What is another name for the transverse plane used in radiology?
The axial plane.
What does medial mean?
Closer to the midline.
What does lateral mean?
Further from the midline.
What does superior mean?
Towards the top of the body.
What does inferior mean?
Towards the bottom of the body.
What does anterior mean?
Towards the front of the body.
What does posterior mean?
Towards the back of the body.
What does rostral mean embryologically?
Towards the head end.
What does caudal mean embryologically?
Towards the tail end.
What does dorsal mean embryologically?
Towards the back.
What does ventral mean embryologically?
Towards the belly.
Why are rostral and superior not always equivalent in the brain?
The developing brain becomes flexed during development.
Why are rostral, caudal, dorsal and ventral retained in neuroanatomy?
To describe positions relative to the long axis of the nervous system.
How are transverse sections of the spinal cord traditionally oriented in neuroanatomy?
Dorsal at the top and ventral at the bottom.
How are axial radiological images conventionally orientated?
As if viewed from the feet looking towards the head.
In neuroradiological images where is the anterior aspect shown?
At the top of the image.
Why can neuroanatomical and radiological images appear different?
They use different orientation conventions.
What is the structural and functional unit of the nervous system?
The neurone.
Approximately how many neurones are present in the human nervous system?
About 10^10.
What are the three major functions of neurones?
Receive information, integrate information and transmit information.
What are effector organs?
Muscles, organs and glands under neural control.
What is a synapse?
A specialised region where information passes between adjacent cells.
What is the soma?
The neurone cell body containing the nucleus.
What are dendrites?
Branching receptive neuronal processes that receive incoming information.
How many synapses may be present on a neurone's dendrites?
Often many thousands.
How may dendrites be specialised in sensory neurones?
They may directly detect changes in the internal or external environment.
What is the axon?
The neuronal process that carries information away from the cell body.
What are axon collaterals?
Branches of an axon that distribute information to multiple destinations.
What are terminal boutons?
Presynaptic endings at the ends of axons.
What specialised synapse occurs between motor neurones and skeletal muscle?
The neuromuscular junction.
What is the membrane potential?
The electrical potential difference across a neurone's membrane.
What is the resting membrane potential of most neurones?
Approximately -60 to -70 mV.
How is the inside of a resting neurone charged relative to the outside?
Negatively charged.
What is an action potential?
A brief reversal of membrane polarity that propagates along the axon.
What triggers neurotransmitter release?
Arrival of an action potential at the presynaptic terminal.
Where are neurotransmitters stored before release?
In synaptic vesicles.
How do neurotransmitters act on the postsynaptic cell?
They bind to specific receptors on the postsynaptic membrane.
What is depolarisation?
A membrane potential change towards the threshold for action potential generation.
What is hyperpolarisation?
A membrane potential change that makes action potential generation less likely.
What are neuroglial cells?
Non-neuronal cells that support nervous system function.
Do glial cells directly process information?
No.
Which glial cell produces myelin in the CNS?
The oligodendrocyte.
What is myelin?
A lipid-rich membrane sheath surrounding many axons.
What is a major function of myelin?
It greatly increases the speed of action potential conduction.
How do neuroglia compare numerically with neurones?
They outnumber neurones by approximately an order of magnitude.
What structures make up the CNS?
The brain and spinal cord.
What structures make up the PNS?
Cranial nerves, spinal nerves and peripheral ganglia.
What is the major role of the PNS?
To connect the CNS with structures throughout the body.
What are ganglia?
Collections of neuronal cell bodies located in the peripheral nervous system.
What is the brachial plexus?
A network in which spinal nerve fibres destined for the upper limb are redistributed.
What is the lumbar plexus?
A network in which spinal nerve fibres destined for the lower limb are redistributed.
What is the somatic nervous system?
The part of the nervous system concerned with sensation from the external environment and control of movement.
What is the autonomic nervous system?
The part of the nervous system concerned with the viscera and maintenance of homeostasis.
What structures are innervated by the ANS?
Smooth muscle, cardiac muscle and glands.
What are the two divisions of the ANS?
Sympathetic and parasympathetic divisions.
How do sympathetic and parasympathetic effects usually relate to one another?
They are generally antagonistic.
What is an afferent neurone?
A neurone carrying information towards the CNS.
What is another name for an afferent neurone whose information reaches consciousness?
A sensory neurone.
What is an efferent neurone?
A neurone carrying information away from the CNS.
What is another name for an efferent neurone supplying skeletal muscle?
A motor neurone.
What is an interneurone?
A neurone located entirely within the CNS.
What is grey matter?
Regions enriched in neuronal cell bodies.
What is white matter?
Regions enriched in axons, particularly myelinated axons.
Why is white matter pale in colour?
Because it contains large amounts of myelin.
What is a nucleus in neuroanatomy?
A collection of neuronal cell bodies with related functions and connections.
What is a tract?
A bundle of axons sharing common functions and connections.
What is decussation?
The crossing of a neural pathway from one side of the CNS to the other.
How are the cerebral hemispheres generally related to the body?
Each hemisphere functions primarily with the contralateral side of the body.
What are the three meningeal layers?
Dura mater, arachnoid mater and pia mater.
Which meningeal layer is outermost?
The dura mater.
What is the characteristic of the dura mater?
A tough fibrous membrane surrounding the CNS.
Which meningeal layer is innermost?
The pia mater.
How does the pia mater relate to the brain surface?
It closely follows all contours of the CNS surface.
What is the arachnoid mater?
A translucent collagenous membrane between dura and pia.
What lies between the dura and arachnoid mater?
The subdural space.
What lies between the arachnoid and pia mater?
The subarachnoid space.
Where does cerebrospinal fluid circulate?
In the subarachnoid space.
What is the falx cerebri?
A dural reflection located between the two cerebral hemispheres.
What lies immediately beneath the free edge of the falx cerebri?
The corpus callosum.
What is the tentorium cerebelli?
A horizontal dural reflection separating the cerebellum from the occipital lobes.
What are dural venous sinuses?
Venous drainage channels formed between layers of dura mater.
What is the superior sagittal sinus?
A dural venous sinus along the attachment of the falx cerebri.
What artery supplies much of the cranial dura?
The middle meningeal artery.
What arteries supply the brain?
The internal carotid and vertebral arteries.
What vascular ring is formed by anastomosis of carotid and vertebral systems?
The circle of Willis.
What arteries reinforce the blood supply of the spinal cord?
Radicular arteries.
How many pairs of spinal nerves are attached to the spinal cord?
31 pairs.