General neuroanatomy terms and structures

Question 1

Commissure

Answer 1

(joining structure) – in the brain refers to a bundle of nerve fibers traversing the midline (longitudinal fissure) to interconnect the cerebral hemispheres. Examples include Anterior commissure, Posterior commissure, Corpus collosum

Question 2

Peduncle

Answer 2

(stalk attaching a tissue mass) – a large bundle of fibers serving as major source of input or output to large brain structures. Examples include Cerebral penduncles, Cerebellar penduncles

Question 3

Fasiculus

Answer 3

slender bundle of fibers; tracts

Question 4

Funiculus

Answer 4

bundles of fasiculi; columns

Question 5

Lemniscus

Answer 5

(ribbon or band) usually flat bundle of fibers. Examples include Medial lemniscus, Lateral lemniscus

Question 6

Decussation

Answer 6

(cross over) – crossing from on side to the other as in an X shape

Question 7

Central/Peripheral Nervous System

Answer 7

The CNS consists of the brain, spinal cord and retina, while the PNS is the spinal and cranial nerves, ganglia, and nerve roots (which project into the spinal cord).

Question 8

Somatic and Autonomic Nervous System

Answer 8

Somatic (body) refers to innervation of the body wall (meaning skeletal muscle, skin, mucous membranes), while autonomic refers to innervation of the smooth muscle and glands controlling internal organs (viscera) and blood vessels.

Note the enteric division has its own (intrinsic) sensory and motor reflexes independent of the CNS and controls GI (smooth muscle) motility and secretions. The other two divisions of the ANS provide extrinsic control of the walls of GI tract (not depicted here)

Question 9

Efferent/Afferent

Answer 9

If your point of reference is within the central nervous system, then Efferent = exit = output (usually motor function), while Afferent = arriving = input (usually sensory function)

Question 10

Cerebrum/Cerebellum

Answer 10

Cerebrum refers to the hemispheres of the cerebral cortex, while cerebellum is a distinct structure lying on the ventral caudal surface of the cerebral cortex.

Question 11

Sulcus/Gyrus

Answer 11

used in the context of surface topology (of the brain). Sulcus is the fissure, invagination or valley and gyrus is the hills.

Question 12

White and Gray Matter

Answer 12

white matter refers to white-colored myelinated axons, while gray matter refers to (non-white) cell bodies of neurons.

Question 13

Upper/Lower Motor Neuron (Disorder)

Answer 13

“Upper” refers to motor neurons originating in the cerebral cortex and their (axonal) projects to the “lower” motor neurons originating in the brain stem or spinal cord and its projections to the muscle

Question 14

Direct and indirect pathway

Answer 14

In context of connections between two basal ganglia structures: striatum and the internal globus pallidus (GPi). “Direct” pathway refers to the monosynaptic connection between these structures, while “indirect” pathway refers to the polysynaptic connections (and a number of intervening structures) between them

Question 15

Foramen

Answer 15

(opening) – such as in bone or interconnecting ventricles

Question 16

Colliculus

Answer 16

(bump) – a small elevation on a surface. Examples include Inferior colliculli and Superior colliculli

Question 17

Tectum

Answer 17

(roof) – dorsal part of the midbrain responsible for visual and auditory reflexes

Question 18

Ganglion

Answer 18

(mass) – a collection of neuronal cell bodies forming a localized nerve center (typically outside the CNS)

Question 19

CNS divisional nomenclatures

Answer 19

forebrain- equivalent to the prosencephalon in development. contains the telencephalon and the diencephalon

midbrain- mesencephalon in developement

hindbrain- rhombencephalon in development. Contains the cerebellum, medulla, and pons

Question 20

Frontal

Answer 20

Movement Execution; Primary Motor Cortex
Premotor/Supplementary Motor Area
Frontal Eye Fields – rapid eye movements & directed attention

Mood; Dorsolateral prefrontal cortex, subgenual cortex

Impulse; Orbito(pre)frontal cortex

Language (production/comprehension); Broca’s Area – motor expression of language: semantics, phonetics and verbal understanding

Question 21

Parietal

Answer 21

Somatosenory Perception; Primary Somatosensory Cortex

Integration of visual and somatospatial information; Visual & Somatosensory Association Areas

Question 22

Occipital

Answer 22

Visual Perception; Primary Visual Cortex

Integration of visual and somatospatial information; Visual & Somatosensory Association Areas

Question 23

Temporal

Answer 23

Auditory Perception,
Olfactory Perception; Primary Auditory Cortex (Heschl’s Gyrus)
Primary Olfactory Cortex (Piriform Cortex)
respectively

Memory, Emotion/Motivation ; Harbors the hippocampus, amygdala

Language (Reception); Language Cortex (Wernicke’s area) – language reception: verbal & reading comprehension

Question 24

Corpus Callosum

Answer 24

Interconnects all positions of the cerebral hemispheres. Rostral portions subserve more rostral cortex etc.

There is a somatotopy along the sagittal plane indicated by subdivisons in the naming. Can be born without one: callosal agenesis. Lesion results in inability of right-handers to name/describe an object in the left hand and inability to retrieve by hand objective palpated by other.

Question 25

Anterior Commissure

Answer 25

Interconnects temporal lobes, orbitofrontal cortex, particularly amygdala and carries decussating fibers of olfactory tracts

Much smaller than corpus callosum and serves primarily temporal lobe structures. Involved in visual memory tasks as such visual traces are apparently bilateral. Compensates for lesions to splenium of corpus callosum (subserving vision).

Question 26

Posterior Commissure

Answer 26

interconnects the pretectal nuclei, mediating the consensual pupillary light reflex. Fibers projecting to oculomotor & trochlear nuclei pass through this commissure.

Much smaller than corpus callosum and serves occipital lobe structures. Lesioning results in upward gaze paralysis

Question 27

Internal Capsule

Answer 27

Is comprised of motor neuron axons from cortex and brainstem (bulbar) traveling to the spinal cord

Pass through the basal ganglia, but do not send collaterals to synapse there. Damage to the anterior portion of the poster limb can result in a pure motor stroke

Question 28

Cerebral Peduncles

Answer 28

The internal capsule becomes part of the cerebral peduncles

Motor fibers passing through the cerebral peduncles will become the pyramids on their way to the bulbar or spinal cord

Question 29

Cerebellar Peduncles

Answer 29

Carry input or output fibers to or from cerebellum

Superior peduncle carries output from and the middle and inferior carry input to the cerebellum

Question 30

Thalamus

Answer 30

Relays information from brainstem to cortex and between cortical regions

Serves as a major brain relay station and has many subdivisions

Question 31

Superior colliculus

Answer 31

Sensory relay nucleus involved in vision

SC -> LGN -> visual cortex (BA17/18/19)

Note: Lateral Geniculate Nucleus (LGN) and Medial Geniculate Nucleus (MGN) are sometimes referred to as the metathalamus

Question 32

Inferior colliculus

Answer 32

Sensory relay nucleus involved in hearing

IC ->MGN -> primary auditory cortex (BA41/42)

Note: Lateral Geniculate Nucleus (LGN) and Medial Geniculate Nucleus (MGN) are sometimes referred to as the metathalamus

Question 33

Hypothalamus

Answer 33

Involved in regulation of thirst, appetite, sex drive and autonomic function and neurocrine function

Role in regulating mood

Question 34

Pituitary

Answer 34

Releases hormones regulating growth, blood pressure, production of breast milk, sex organ and thyroid gland functions, regulation of water/osmolarity and temperature

Under the control of the hypothalamus and connected to it by the infundibulum (pituitary stalk)

Question 35

Pineal Gland

Answer 35

Modulation of circadian rhythms: wake/sleep and seasonal cycles

Produces the sleep hormone melatonin. Not enclosed by BBB.

Pituitary gland is encased in bone. The pineal gland is outside the blood-brain-barrier and together with the eye regulates circadian rhythms

Question 36

Cerebellum

Answer 36

Coordinates and fine tunes voluntary movement, Posture and balance. Motor learning and memory (e.g., stereotyped movements)

Somatopically organized. Has several subdivisons. Lots of motor issues depending upon region damaged: ataxia, falling, past pointing, inability to rapidly supinate and pronate.

Question 37

Caudate

Answer 37

Modulates movement

Input structure of basal ganglia. Degenerates in Huntington’s disease. Produces some acetylcholine.

Question 38

Putamen

Answer 38

Modulates movement

Input structure of basal ganglia. Degenerates in Huntington’s disease. Produces some acetylcholine.

Question 39

Globus pallidus

Answer 39

Modulates movement

Has two portions named interior and exterior. GPi is output structure of basal ganglia. GPe is part of indirect pathway.

Question 40

Substantia Nigra

black substance

Answer 40

Input to the basal ganglia

Has two portions compacta and reticulata. SNc provides input into the basal ganglia and produces dopamine. This area degenerates in Parkinson’s disease

Question 41

Subthalamic Nucleus

Answer 41

Modulates movement

Part of the indirect pathway. Lesion results in hemiballism.

Question 42

Hippocampus

Answer 42

Memory formation especially spatial orientation memory

Located in the temporal lobe and caudal to the amygdala. Lesions impair new memory formation.

Question 43

Amygdala

Answer 43

Emotion, especially fear – conditioned fear

Has a role in learned memories

Question 44

Mammillary Bodies

Answer 44

Involved in memory processing, specifically recollection.

Susceptible to thiamine deficiency. Atropy in alcoholics and lesions result in amensia. Receives input from hippocampus via fornix

Question 45

Cerebellum

Answer 45

Motor learning and memory (e.g., stereotyped movements)
Coordinates and Fine Tunes Movement

Learned stereotypic motor skills like swimming, typing. Vermal atrophy in alcoholics leading to ataxia

Question 46

Anterior Commissure

Answer 46

Involved in visual memory which requires bilateral connections

Also interconnects amygdali

Question 47

Pons & medulla

Answer 47

Contains structures involved in control of autonomic functions and some cranial nerves. Relays Sensory Info between Cerebrum & Cerebellum

Harbors structures for arousal/consciousness, sleep, facial expressions, feeding, breathing, blood pressure and heart rhythms

Question 48

Nucleus basalis of Meynert

Answer 48

Involved in sleep and wakefulness

Produces acetylcholine. Degenerates in Alzheimers.

Question 49

Septal Nuclei

Answer 49

Involved in sleep and wakefulness

Located in the basal forebrain. Produces acetylcholine. Degenerates in Alzheimers.

Question 50

Nucleus accumbens

Answer 50

Reward center

Located at the point at which the dorsal and ventral striatum converge

Question 51

Uncus

Answer 51

Involved in processing olfactory and emotional information

Located at the anterior end of the parahippocampal gyrus. Part of the olfactory cortex (BA34) and seizures here cause unpleasant odors.

Question 52

Olfactory Bulbs/Tracts

Answer 52

Tracts carry olfactory nerves

Damage to these areas bilaterally result in anosmia (can’t smell)

Question 53

Dorsal (posterior) Column also known as the medial lemniscal system

Answer 53

carries ascending somatosensory information (touch, joint sensation, two-point discrimination, vibrational sense and motion sense) via the spinal cord to cortex.

Involved in perception of mechanic stimuli and conscious awareness of body position and limb movement. Pathway characterized by faster conducting fibers and limited number of synaptic connections on the way to the cortex. Sensory deficit is on ipsilateral side below the level of the lesion.

Question 54

Spinothalamic Tract also known as the ventrolateral system

Answer 54

Carries ascending nocioceptive (mechanical, chemical and thermal pain) as well as crude touch and changes in skin temperature information via the spinal cord to cortex.

Pathway characterized by slower conducting fibers and more synaptic connections on the way to the cortex. Sensory deficit is on contralateral side below the level of the lesion.

Question 55

Cortiospinal Tract also known as the pyramidal tracts

Answer 55

Carries descending motor information for the body from the cortex to the spinal cord.

Pathway comprised of pyramidal cell axons that become the (anterior portion of posterior limb of) internal capsule, then the cerebral peduncles, then pyramids. Motor deficit is on the contralateral side for lesions rostral to the decussation, e.g., at level of cerebral peduncles and above.

Corticobulbar tract is similar but subserves the face and terminates in brainstem nuclei

Question 56

Gate’s “Rule of Four” for vascular brainstem syndromes

Answer 56

1. Four ‘midline’ structures begin with the letter M: Motor (corticospinal) Tract (M-CST), Medial Lemniscus (ML), Medial Longitudinal Fasciculus (MLF), Motor (Cranial) Nucleus and Nerve (M-CN) [CN3, 4, 6 or 12].
2. Four (lateral) ‘side’ structures begin with the letter S: Spinocerebellular Tract (SCT), Spinothalamic Tract (STT), Sensory 5th (Cranial) nucleus (S-CN5), Sympathetic Tract (Sym).
3. There are four cranial nerves in the medulla [CN9-12], four in the pons [CN5-8] and four above the pons (two in the midbrain [CN3-4]).
4. Ignoring CN1 and 2, the four CN motor nuclei along the midline are those that divide equally into 12: 3, 4, 6 and 12. Thus CN5, 7, 9 and 11 are in the lateral brainstem).

Question 57

Schetz’s simplified “Rule of Three” for vascular brainstem syndromes

Answer 57

1. The ‘midline’ structures begin with the letter M: Motor (corticospinal) Tract (M-CST), Medial Lemniscus (ML), Motor (Cranial) Nucleus and Nerve (M-CN) [CN3, 6 or 12].
2. Three (lateral) ‘side’ structures begin with the letter S: Spinocerebellular Tract (SCT), Spinothalamic Tract (STT), Sensory 5th (Cranial) nucleus (S-CN5).
3. Starting with three double the number, the three most important CN motor nuclei along the midline are 3, 6 and 12. Starting with five add two, CN5, 7, 9 and 11 are lateral.