Functional Neuroanatomy: Exam 1
Terms in this set (100)
What are the two main components of the Central Nervous System (CNS)?
Brain and spinal cord
What are the three parts of the brain stem?
Medulla, Pons, Midbrain
Name the two regions of the brain that occur as hemispheres.
1. Cerebral hemisphere
2. Cerebellar hemisphere
Give two features by which you can distinguish a T1 weighted from a T2 weighted MRI image.
In T1 gray matter appears gray and white matter appears white. In T2 gray matter is light gray, white matter dark gray. T1 water (CSF) appears black, in T2 appears white.
What is a computerized tomography (CT) scan most useful for?
For quick examination of brain for signs of bleeding or major contusions.
What is an Electroencephalogram (EEG)?
A recording of overall electrical activity of the brain measured at the surface of the skull with scalp electrodes or within the brain with depth electrodes.
What is a neuron?
It is the anatomic, trophic, genetic and functional unit of the brain.
What are the specializations of neurons that make it different from other cells and makes the brain function differently from other organs?
Distinctive cell shape
Outer membrane capable of generating nerve impulses.
A synapse for transferring information from one neuron to another.
What is the distinctive structure of a dendrite?
It is an extension of the cell body of a neuron that has large diameter nearer the cell body and gradually narrows away fro, the cell body. It also receives synapses from other neurons.
What is the distinctive structure of a axon?
It is a single extension of a neuron that carries nerve impulses away from the neuron. Its final endings for terminal buttons or swellings, which contain neurotransmitter vesicles.
What is the distinctive structure of a synapse?
It is the junction between two neurons.
What are the 5 classes of proteins found on neuronal membranes and what do they do?
1. Structural - helps anchor other molecules to the membrane. There are molecules such as integrins and cadherins which are structural proteins. Then there are proteins, which contribute to desmosomes and tight junctions and helps hold synapses together.
2. Channel - forms channels in the membrane for movement of ions
3. Pumps - form molecular pumps for exchanging ions across the membrane
4. Receptor - capable of responding to neurotransmitters and neuromodulators
5. Enzyme - there are usually linked to receptors and help activate them through catalyzing molecular reactions.
Distinguish between the axon hillock, initial segment and axon of a neuron. What are their specific functions?
Axon hillock is a slight elevation from the neuron cell body where all the synaptic inputs are summated (temporal and spatial summation). The initial segment is the portion of the axon adjacent to the axon hillock, where an action potential is triggered or initiated. It is unmyelinated and has a high density of sodium channels.
What is a bipolar neuron, a unipolar neuron, a pseudo-unipolar neurons, and a multipolar neuron.
Bipolar has two poles, one dendrite and one axon.
Unipolar neurons has a single fiber one end which is specialized to function like a dendrite and the other as an axon. The cell body does not participate in the transmission of nerve impulses. Only plays a trophic role.
A pseudounipolar neuron is one which starts as a bipolar neuron and then becomes unipolar (e.g human dorsal root ganglion neurons)
A multipolar neuron has several dendrites.
What is a projection neuron and an intrinsic or local circuit neuron or interneuron?
A projection neuron has a long axon which extends outside of its immediate vicinity to contact distant neurons in subcortical locations such as the corpus striatum, brain stem, spinal cord, or thalamus.
An interneuron on the other hand modulates neuronal activity between two communicating neurons, thereby creating neural circuits. One kind of interneuron is found between sensory and motor neurons, controlling reflexes such as the knee jerk reflex.
Afferent neuron or axon and efferent neuron or axon; distinguish between them.
An afferent axon is one that brings nerve impulses to a neuron (input).
An efferent axon is one that carries nerve impulses away from a neuron (output).
What do you understand by the "nuclear" arrangement of neurons and the 'laminar" arrangement of neurons?
Nuclear - grouping of neurons into clusters.
Laminar - arrangement of neurons in layers.
What are the different types of glia found in the nervous system and how do you differentiate between them. After reviewing their functions, describe one main function for each.
All glia lack an axon and do not generally receive synapses from neurons.
Astrocyte - Macroglia (largest of glia). Cell body has many extensions in a star-like manner. Distinguished by the presence of a filamentous protein called glial fibrillary acidic protein. Many functions - clears dying neurons, participate in the removal of some neurotransporters from synaptic cleft, involved in neuronal excitation through Ca+ waves, diffuses local increases in K+ ions in extracellular spaces through intracellular diffusion, produces inflammatory molecules.
Oligodendroglia: are smaller than astrocytes and function to provide the myelin covering of axons.
Microglia: are smallest of glia, and have few extensions that end in claw-like processes. Their main role is to remove dying brain tissue.
What are the names of the 3 membranous coverings (Meninges) surrounding the brain.
a) Dura Mater
b) Pia Mater
c) Arachnoid Mater
The falx cerebri and the tentorium cerebelli: What are these and what is their functional role?
These are deep extensions of the meningeal layer of the dura dividing the cranial cavity into sub chambers. The falx cerebri separates the two cerebral hemispheres, while the tentorium cerebelli separates the cerebellum from the cerebral hemispheres.
epidural space in the brain
epidural space in the spinal cord
What is a "dural" sinus?
A space creates by the separation of he periosteal and meningeal dura in certain places.
Name the dural sinuses:
Supra saggital sinus
What do dural sinuses do?
They act as channel into which CSF (via arachnoid granulations) and venous blood empty (by the opening of veins into them) and eventually drains out the venous blood by emptying into the jugular veins.
What are Cisterns?
They are enlarged regions of the subarachnoid space.
What is the cisterna magna?
The space surrounding the openings from the 4th ventricle (foramen Megendie and foramen Lushka)
What is the lumbar cistern?
The subarachnoid space in the lumbar region between L2 and the sacrum. It has mainly nerves before exiting the vertebral canal, is filled with CSF, and is a place for safely collecting CSF for clinical investigation.
Arachnoid granulations - what are they and what do they do?
These are extensions of the arachnoid membrane (covered by ependymal cells) into the suprasagital sinus, which function as one-way valves for the flow of CSF from subarachnoid space into the sinus.
In what part of the brain are the ventricles located?
Lateral Ventricles - Cerebral hemispheres.
Third Ventricle - Diencephalon (between the two thalami).
Cerebral Aqueducts - Midbrain.
4th Ventricle - Pons and Medulla.
Foramen of Monroe - Opening between lateral ventricle and third ventricle.
Foramina of Luschka and Magendie - At the caudal ends of the medulla.
In which parts of the ventricle is choroid plexus found.
Lateral ventricles, third ventricle and caudal part of the fourth ventricle.
Identify the unique features of the choroid epithelium
1. Cuboidal cells whcih are tightly bound to each other laterally by tight junctions so water and solutes cannot follow into the ventricle between them.
2. The basal membrane and the luminal membrane (ventricular side) are specialized to selectively move required ions and molecules into the cells and out of the ventricle respectively because of the presence of specialized transporter and channel molecules.
3. The blood vessels entering the plexus are fenestrated (leaky) and allow serum to leak into the choroid.
What is the blood-CSF (cerebrospinal fluid) barrier?
It is the cuboidal epithelium of the choroid plexus.
What are the differences in the composition of CSF compared to blood?
1. More proteins in the blood whereas hardly any in the CSF.
2. Lower K+ and slightly hgiher Mg+ and Cl- in CSF and blood.
How does the choroid plexus function and form cerebrospinal fluid (CSF)? Identify the critical mechanisms.
1. Action of the carbonic anhydrase.
2. Function of the Na/K+ ATPase pump
3. Function of Na/K/Cl- co-transporter
What are the effects of the action of carbonic anhydrase in the formation of CSF?
It is an enzyme, which catalyzes the break down of carbonic acid into bicarbonate ions and hydrogen ions. The latter ions are traded for sodium and chloride ions into the cell.
What is the function of the Na+/K+ -ATPase pump in the formation of CSF?
Exchanges Na+ for K+ by a process that needs energy (ATP) for function. The ATPase Catalyzes a reaction that converts ATP into ADP and a phosphate ion, which is fueled for driving the pump.
What is the function of the Na+/K+/Cl- co-transporter in the formation of CSF?
It is a molecule that transports Na+ and K+ along with 2 Cl- molecules (co-transporters) across a membrane.
How does water get into the ventricles in the formation of CSF?
Water gets moved in when the ionic concentration in ventricles is higher than in the choroid epithelial cells, by the operation of water transporter molecules (Aquaporin 1).
Identify at least 4 functions of CSF.
1. Maintains the required ionic composition of the extracellular fluid for proper neuronal activity
2. Mechanical support for the brain reducing its effective weight
3. Drainage pathway for metabolic waste products
4. Import route for essential micronutrients reaching the neurons in extracellular space.
5. Route for neuronal communication by carrying hormones and even glutamate (paracrine function)
What is hydrocephalus?
Increased water (fluid) in the ventricles of the brain.
What is the blood-brain- barrier? What is it made up of?
It is a barrier between the blood in the capillaries of the brain and the surrounding brain tissue (also called brain parenchyma) such that blood does not freely flow into the surrounding tissue. Only required molecules from the blood can pass through this barrier. It is made up of endothelial cells whose ends overlap and are tightly joined to each other by tight junctions.
How do non-lipid soluble substances (e.g. glucose) get through the blood-brain-barrier (BBB)?
They are moved through endothelial cell membranes by glucose transporter molecules embedded in the membrane.
Name the major arteries that bring blood to the brain.
Vertebral artery and the internal carotid artery.
What is the circle of Willis and what are its component blood vessels?
It is the anastomotic (connected to each other) ring of blood vessels, which encircle the stalk of the pituitary gland. Its components include the internal carotid artery, the anterior and cerebral artery, anterior communicating artery, posterior communicating artery, and the posterior cerebral artery.
What are the brain territories supplied by the anterior cerebral artery?
The medial surface of the cerebral hemispheres and a small portion (about 2 fingers width) of adjacent dorsal surface of the cerebral hemisphere.
What are the brain territories supplied by the middle cerebral artery?
The lateral surface of the cerebral hemisphere.
What are the brain territories supplied by the posterior cerebral artery?
The occipital pole and the lateroventral portion of the temporal lobe.
Name the major arteries that supply blood to the brainstem and spinal cord.
Vertebral artery and Basilar artery
What is an aneurysm (aneurism)?
A ballon like bulge from the wall of an artery
What is the Neural plate?
It is a specialized portion of the ectoderm of the gastrula from which the entire brain will develop.
What are neural folds?
These are the dorsal edges of the ectodermal plate before they fuse to form the neural tube.
What is the neural tube?
A longitudinal tube of ectoderm cells enclosing a central cavity, from which the entire brain and spinal cord develop.
Anencephaly: what does the term mean, and how is it caused?
Is it an incompletely formed brain and head region due to the failure of the anterior neuropore to close.
What is the cause of spina bifida?
An incompletely formed or open posterior end of the neural tube resulting from a failure of the posterior neuropore to close.
What are the 3 primary vesicles of the embryonic brain formed from the neural tube?
What are neural crest cells and what parts of the adult nervous system do they give rise to?
These are groups of cells left outside of the neural tube when the neural folds coalesce. These cells give rise to the peripheral and autonomic nervous systems.
What components of the adult spinal cord do the alar and basal plates give rise to?
The Alar plate gives rise to the dorsal horn (sensory), and the basal plate gives rise to the ventral horn (motor).
From where and how does the cerebellum develop?
The cerebellum develops through the proliferation of cells from the rhombic lip area of the metencephalon. The rostral part of the rhombic lip then gives rise to layers of the cerebellum. The caudal part gives rise to he inferior olive, pontine nuclei, and cochlear nuclei.
What are the three regions of the adult cerebral hemispheres that develop from the embryonic telencephalic vesicles?
- Basal ganglia → striatal area at the base of the brain that controls motor function
- Suprastriatal cortex → cerebral cortex
- Rhinencephalon → "nose brain", the olfactory system, pyriform cortex, parahippocampal cortex, hippocampus, cingulate cortex and amygdala.
What number of spinal cord segments are there in the cervical, thoracic, lumbar and scaral regions of the spinal cord?
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
What are the spinal cord segments (extent) that are identified as the Cervical enlargement?
C5 - T1
The arms and hands have many muscles, and therefore need to have many more neurons to control fine movements. Since these regions need to receive more sensory input in order to have more control of them, there is a greater population of neuron in this region - making this region larger in the spinal cord.
What are the spinal cord segments (extent) that are identified as the Lumbar enlargement?
L2 - S3
The lower limbs, such as the legs and feet, also need very fine motor control. This accommodation is made by having a higher number of neurons on the lower end of the spinal cord - making this region also larger.
Name the component parts of the spinal gray matter.
Lateral horn (only in thoracic spinal cord segments)
Name the component parts of the spinal white matter.
Dorsal funiculus (dorsal columns), lateral funiculus, and ventral funiculus
Where is the Dorsal Horn located and what is it's major functions?
Processes sensory information, is gray matter and found in all spinal cord segments.
Where is the Ventral Horn located and what is it's major functions?
Ventral gray matter of spinal cord, involved in motor function, found at all spinal cord levels. It is large a the cervical and lumbar enlargements.
Where is the Lateral Horn located and what is it's major functions?
Found from T1 - L1, has visceromotor neurons.
Where is the Dorsal nucleus of Clark located and what is it's major functions?
T1 - T12; group of neurons at the base of the dorsal horn, receives proprioceptive inputs from lower body. Gives rise to the dorsal and ventral spinocerebellar tracts.
Where is the Dorsal Columns located and what is it's major functions?
These compose the dorsal funiculus, and carry somatosenosry information from the body below the head to the dorsal column nuclei (gracilis and cuneatus).
Where is the Tract of Lissauer located and what is it's major functions?
Is a bundle of fibers at the apex of the dorsal horn and the fibers in it are mostly thinly myelinated or unmyelinated axons.It is involved in pain and temperature information transfer from the body.
Location of the corticospinal tract?
Found in the dorsal half of the lateral funiculus
Location of the rubrospinal tract?
Located just ventral to the corticospinal tract
Location of the spinothalamic tract?
Located in the ventrolateral part of the lateral funiculus
Location of the dorsal and ventral spinocerebellar tract?
Along the lateral edge of the lateral funiculus
What are the component parts of a spinal reflex pathway?
Muscle receptors, Axons from receptors entering spinal cord via the dorsal roots, direct synapse onto a motor neuron in ventral horn, and its axon innervating the flexor muscles.
Dermatomes and myotomes, and what are their relationship to spinal peripheral nerves?
Dermatomes are portions of the skin associated with a particular peripheral nerve.
Myotome - group of muscles that are innervated by motor fibers that originate from a single motor nerve root
What are the three main parts of the brain stem?
To which part of the brainstem is the cerebellum connected?
Name the three peduncles connecting the cerebellum to the brainstem.
- middle cerebellar peduncle
- inferior cerebellar peduncles
- superior cerebellar peduncles
What are the major landmarks on the dorsal surface of the midbrain named?
Superior (Vision) and Inferior (Audition) Colliculi are collectively known as the corpora quadrigemina
How many cranial nerves are there?
Name the Cranial Nerves:
1 - olfactory
2 - optic nerve
3 - oculomotor
4 - trochlear nerve
5 - trigeminal
6 - abducens
7 - facial nerve (pons)
8 - vestibulocochlear nerve (pons)
9 - glossopharyngeal
10 - vagal nerve
11 - accessory nerve
12 - hypoglossal nerve
Which cranial nerves are associated with the midbrain?
3 - Occulomotor
4 - Trochlear
Which three cranial nerves control the muscles of the eye?
3 - Occulomotor
4 - Trochlear
6 - Abducens
Name the cranial nerves that have a purely sensory function:
1 - Optic
2 - Olfactory
8 - Vestibular Cochlear (hearing and balance)
What is a mixed cranial nerve? Name the mixed cranial nerves.
A mixed cranial nerve is a nerve that has both sensory and motor functions.
5 - trigeminal
7 - facial
9 - glossopharyngeal
10 - vagal nerve
How many cranial nerves mediate purely motor control, and what is the origin of the motor neuron groups associated with the mixed cranial nerves?
3 - oculomotor
4 - trochlear
6 - abducens
11 - accessory
12 - hypoglossal
They originate from the brachial arches.
Be able to name the somatomotor, visceromotor, viscerosensory and somatosensory nuclei associated with the mixed cranial nerves.
•CN 5 - Motor nucleus of Trigenimal
•CN 7 - Facial motor nucleus
•CN 9 - nucleus ambiguous
•CN 10 - nucleus ambiguous
•CN 5 - N/A
•CN 7 - Superior Salivary nucleus
•CN 9 - Inferior Salivary nucleus
•CN 10 - Vagal motor nucleus
•CN 5, 7, 9, 10 - Trigeminal sensory nucleus (which includes principal sensory nucleus and trigeminospinal nucleus)
•CN 5 - N/A
•CN 7 - Nucleus solitarius
•CN 9 - nucleus solitarius
•CN 10 - nucleus solitarius
When you examine the internal organization of the brainstem there are usually elements of 4 components that are encountered. Name these components.
1. Cranial Nerve nuclei
2. Ascending and Descending Tracts
3. Reticular Formation
4. Connections with Cerebellar
In which part of the medulla is the inferior olivary nucleus located?
mid to rostral medulla.
Where in the medulla are the 2 nuclear groups on which the axons of the dorsal column synapse, and what are they named??
Caudal medulla near the obex:
Where in the medulla is the hypoglossal nucleus and which muscles do they control?
Mediodorsal region of rostral medulla. Controls the muscles of the tongue.
Where are the vestibular and cochlear nuclei?
Dorsolateral region of the rostral medulla close to the medulla pons junction.
What are the pyramids of the medulla and is it an ascending or descending tract?
They are a triangular collection of axons on the ventral surface of the medulla. They are descending (corticospinal and corticobulbar) tracts
What is the medial lemniscus, what information does it carry, and is it an ascending or descending tract?
It is a bundle of sensory fibers carrying somatosensory (excluding pain and temperature) information from the body below the neck. It carries somatosensory information (touch, pressure, 2-point discrimination, and proprioception). It is an Ascending tract.
What sort of information is carried through the inferior cerebellar peduncle, and where in the medulla is it located?
Proprioceptive information, and is located in the dorsolateral region of the rostral medulla and into the pons.
The medial longitudinal fasciculus; what nuclear groups does it interconnect?
The medial longitudinal fasciculus interconnects the vestibular nucleus to the ocularmotor nerve (3), the trochlear nerve (4), and the abducens nerve (6) nuclei.