possible short answer questions for neuroanatomy final

describe the afferent and efferent pathways of the 3 subdivisions of the amygdaloid complex

afferent basolateral

• thalamus

• visual cortex

• orbital cortex

afferent central

• hypothalamus

• septal nuclei

• periaqueductal grey

• basolateral amygdala nuclei

afferent corticomedial

• olfactory bulb

• olfactory cortex

efferent basolateral via amygdalofugal pathway

• thalamus (dorsomedial)

• ventral striatum (nuc. accumbens)

• prefrontal cortex

• insula

• hippocampus

• hypothalamus

efferent basolateral direct output

• visual cortex

efferent central via stria terminalis

• septal nucleus

• hypothalamus

efferent via amygdalofugal pathway

• brainstem sites, solitarius, vagal nuclei

efferent corticomedial

• anterior olfactory nucleus

• olfactory cortex

how do limbic connections contribute to motivational behaviors

Amygdala & limbic cortex project to ventral striatum, dorsomedial nucleus of thalamus, prefrontal cortex. Ventral striatum (VS), which includes nucleus accumbens, receives dense dopamine innervation from the ventral tegmental area. The VS is involved in the neural correlates of reward and the reinforcement of behavior. This enables association between sensory stimuli and behaviors that produce rewards and pleasure

describe and distinguish the layers of the dentate gyrus and the CA fields. include what projections are used in each

• dentate gyrus consists of molecular, granular, and polymorphic layer. granular neurons (mossy fibers) provide the main output for the dentate gyrus and project to the apical dendrites of pyramidal cells in the CA3 and CA4 fields.

• the CA fields consist of molecular, pyramidal, and polymorphic layers. pyramidal neurons provide the main output for the CA fields and use glutamate as a neurotransmitter.

describe the efferent and afferent pathways of the hippocampus formation

afferent cortical inputs via perforant pathway

• entorhinal cortex

• posterior cingulate

• orbital cortex (via unicate fasc.)

other afferent inputs via fimbria/fornix

• septal nuclei (cholinergic inputs)

• hippocampus commissure fibers

efferent diencephalic targets

• thalamus (anterior nucleus)

• mammillary bodies

• other hypothalamic sites

efferent telencephalic sites

• septal nuclei

• ventral striatum

• amygdala

• neocortex

distinguish between the precommissural and postcommissural fibers of the hippocampus

precommissural

• originate in CA1 and CA3

• project to septal nuclei and ventral striatum

postcommissural

• originate in subiculum

• project to mammilary body and thalamus

describe the trisynaptic pathway of the hippocampus

• entorhinal cortex to dentate gyrus via perforant pathway

• dentate gyrus to CA3 via mossy fibers

• CA3 to CA1 via Schaffer collaterals

the trisynaptic pathway uses glutamate as a neurotransmitter

describe the similarities and differences between the sympathetic and parasympathetic subdivisions of the ANS

sympathetic

• mediates stress responses (increased heart rate, pupil dilation, suppression of GI tract)

• uses cholinergic preganglionic neurons and noradrenergic postganglionic neurons

• has a diffuse organization

• preganglionic neurons are found in lateral horn of the thoracic-lumbar spinal cord

• postganglionic neurons are found in the paravertebral ganglia (sympathetic trunk), prevertebral ganglia in viscera, and chromaffin cells of adrenal medula

parasympathetic

• maintains body functions (reduces heart rate, pupil constriction, GI tract activation)

• uses cholinergic preganglionic and postganglionic neurons

• has a discrete organization

• preganglionic neurons are found in the cranio-sacral spinal cord and cranial nerve nuclei

• postganglionic neurons are found in ganglia of the head and neck and ganglia close to target organs

describe the four pathways of the sympathetic system

1. Postganglionic efferent fibers depart through the spinal nerve via the grey communicating ramus to innervate blood vessels and the skin. The ganglia at T1–T5 innervate the heart and lungs.

2. Ascending efferents often synapse on postganglionic neurons in the cervical ganglia. The superior cervical ganglion innervate the head, eyes, salivary gland, and heart (pupillary dilation). The middle cervical and stellate ganglia innervate the arms, lungs, and heart (bronchial dilation, tachycardia).

3. Descending efferent fibers synapse on postganglionic neurons in lumbar and sacral ganglia. The postganglionic fibers innervate the lower extremity (skin, blood vessels) via the lumbar and sacral plexuses (vascular dilation, sweating).

4. Autonomic efferents from the splanchnic nerve synapse on postganglionic neurons in the prevertebral ganglia that lie closer to visceral organs.

describe the ANS descending control pathways

visceral sensory afferents of cortex and amygdala → hypothalamus → brainstem → spinal cord (preganglionic neurons of ANS)

describe the cell proliferation and migration pattern of the myelencephalon, metencephalon, cerebellum, and mesencephalon

myelencephalon (medulla)

• alar plate migrate to form inferior olive

• roof plate enlarges for 4th ventricle

• alar and basal plates form sensory and motor nuclei, respectively

metencephalon (pons)

• alar plate migrate to form pontine nuclei

• floor plate is thickened by pontine fibers

• alar and basal plates form sensory and motor nuclei, respectively

cerebellum

• alar plate forms the rhombic lips, which form the cerebellar cortex

mesencephalon (midbrain)

• alar plates form the superior colliculi

• alar plate migrates to form the red nucleus and substantia nigra

• floor plate forms crus cerebri

• basal plate forms motor nuclei

describe three congenital effects that can occur during neural development

anencephaly: failure to close cranial (anterior) neuropore

spina bifida: failure to close dorsal vertabrae

hydrocephaly: blockage of ventricular systems

describe the segmentation of CNS from primary vesicles to secondary vesicles to fully formed brain structures

primary vesicles

• prosencephalon → telencephalon + diencephalon

• mesencephalon → mesencephalon

• rhombencephalon → metencephalon + myelencephalon

secondary vesicles

• telencephalon → cerebral hemispheres

• diencephalon → thalamus + hypothalamus

• mesencephalon → midbrain (pontine nuclei)

• metencephalon → pons (red nucleus, substantia nigra, crus cerebri)

• myelencephalon → medulla (inferior colliculi)

what are the steps of neural development?

• neurulation: induction of neural ectoderm

• segmentation and pattern formation

• cell proliferation

• cell migration and differentiation

• axonal growth and synapse formation

• synaptic stabilization

using the cladogram, describe the difference between shared primitive features, shared derived features, and homoplasous features

shared primitive features

• old traits from distant ancestors

• not monophyletic

• example: centralized nerve cords

• cladogram: 1 and 3 or 1 and 5

shared derived features

• newer traits that evolved in the most recent common ancestor of a group and is unique to that group

• monophyletic

• example: neocortex in mammals

• cladogram: 6 and 8 or 7 and 8

homoplasous features

• features that appear similar but arose independently

• example: gyri

• cladogram: 2 and 4 or 4 and 7

describe the criteria for determining phyletic homology of brain structures

Topological similarity

Topographical organization

embryological development similarity

Neuronal subtype/morphology similarity

Neurochemical/neurotransmitter similarity

Neurophysiological properties

Gene Expression

describe the neuromeric model and its criticisms

• CNS has a long RC axis ending at the lamina terminalis

• Embryonic CNS is subdivided by neuromeres, each forming a ring around the RC axis

• Each neuromere has two longitudinal domains: an alar plate and a basal plate

• major criticism: the forebrain does not possess well-defined segments

what characters were present in the first nervous system?

• Minimal number of cellular specializations

• Reactive to external stimuli

• Transduce external information into electrochemical signals

• Produce an effector response

compare the three proposed methods in which the nervous system evolved

describe the differences between a fully-connected network and a regular network, explain which network is optimal for mammals and why

fully-connected (proportional) network

• each neuron is directly connected to every other neuron

• not possible because he membrane area of a neuron is not large enough to accommodate the synapses, and the metabolic costs of the extra axons would too high

regularly-connected (absolute) network

• neurons primarily connect to a small, localized region of adjacent neurons

• easy to maintain, but increase the transmission time between brain regions that are widely-separated

describe the three different ways in which brain regions may have evolved

• purely mosaic: if the size of a brain region changes independently of other regions

  • example: visual cortes grows for better sight but other regions are unchanged)

• purely concerted: if homologous brain regions show constant proportional changes

  • example: the forebrain, cerebellum, and brainstem all grow in concert

• mildly mosaic: some brain systems show coordinated (concerted) changes, while other regions show independent (mosaic) variation, allowing for specialized adaptations

  • example: mosaic changes in song-control nuclei of songbird but concerted changes in basic brain structures

describe two species that exhibit examples of mosaic evolution

• in mormyrid electric fish, the valvula (part of the cerebellum) is much larger in size compared to other teleocasts, exceeding allometric expectations

• olfactory bulbs are smaller in simians than in prosimians, but simian olfactory cortex is much larger than predicted from their small olfactory bulbs

describe and compare the nuclear-to-layered hypothesis and nuclear-to-claustrum/amygdala hypothesis

nuclear-to-layered hypothesis

• states that a common ancestor of birds and mammals had a nuclear-based pallium, which evolved into a laminar (layered) structure in the mammalian lineage

• direct evolution of ancestral nuclear structures to cortical layers (shared ancestry)

• ectostriatum → layer iv, neostriatum → layer ii & iii, archistriatum → layer v & vi

nuclear-to-claustrum hypothesis

• states that the avian dorsal ventricular ridge (DVR) represents an elaboration of the mammalian amygdala and claustrum, and that the connectivity that the DVR shares with the neocortex evolved independently

• convergent evolution

• both avian DVR and mammalian amygdala have nuclear organization and similar connections

compare two systems between mammals, birds, and reptiles

visual and auditory

describe how the central autonomic network integrates autonomic, endocrine, motor activities

Visceral sensory inputs ascend to the brain via pathways to the NTS and parabrachial nucleus, which relay visceral data to the hypothalamus & amygdala

Descending pathways:

• cortex, amygdala → hypothalamus → brainstem → spinal cord

describe the projections of visceral afferent fibers in the ANS. why is visceral pain perceived on the body wall or extremity rather than the affected organ (referred pain)?

Visceral afferent fibers synapse on preganglionic neurons to form an autonomic reflex arc. Second order sensory neurons project to the brain via the spinothalamic tract to convey visceral pain sensations. Visceral pain is perceived on the body wall or extremity rather than at the affected organ (referred pain) because of the convergence of visceral and somatic fibers on second-order neurons in the dorsal horn.

explain why Edward Lewis proposed that duplicate genes play a critical role in evolution

1. homeotic genes are duplicates of a primordial gene that regulates development of the body.

2. the original gene of a duplicate gene still performs the old function.

3. duplicated genes provide extra genes from which new ones arise.

4. mutations of the duplicated genes enable the performance of new functions