Forebrain and Limbic System

Question 1

divisions of forebrain

Answer 1

1. diencephalon
2. internal capsule
3. limbic system

Question 2

divisions of diencephalon

Answer 2

1. epithalamus: pineal gland, habenula
2. thalamus: all sensory (minus olfaction) paths relay here, composed of distinct nuclei
3. hypothalamus
4. subthalamus

Question 3

divisions of limbic system

Answer 3

1. hippocampus
2. hypothalamus
3. amygdala

Question 4

subdivisions of thalamic nuclei (as defined by internal medullary lamina)

Answer 4

1. ant: ant nucleus, important limbic relay, sits in split in IML
2. med: dorsomedial
3. lat: 1. dorsal tier- lateral dorsal, lat post, pulvinar 2. ventral tier- vent ant, VPL, VPM, med and lat geniulates
   * largest subdivision*
4. intralaminar: centromedian, parafascicular
5. reticular nuc: regulatory role
6. midline nuc

Question 5

theme of all thalamic nuclei (except reticular)

Answer 5

• projection neurons: provide output from thalamus
• interneurons: small, inhibitory

*proportions vary

Question 6

3 categories of thalamic nuclei

Answer 6

1. relay nuc: receive well defined specific input from subcortical source and project to well defined area of cortex
2. association nuc: receive specific inputs and regulatory from association cortex and project abck
3. intralaminar and midline nuc: receive distinct set of specific inputs, project to cortex, BG, and limbic structures

Question 7

reticular nucleus

Answer 7

• imp source of regulatory input to thalamus
• no projections to cortex
• input: cortex and thalamus
• output: inhib axons to thalamus

Question 8

sensory system relay nuclei

Answer 8

VPL and VPM

Question 9

motor system relay nuc

Answer 9

VA and VL

Question 10

limbic system relay nuc

Answer 10

anterior, LD

Question 11

main association nuc

Answer 11

DM (prefrontal lobe)

pulvinar (parietal-occipital-temporal)

Question 12

internal capsule

Answer 12

• thalamocortical and corticothalamic fibers pass thru

- collects and forms cerebral peduncle (corticopontine/bulbar/spinal fibers descend thru)

Question 13

5 parts of internal capsule (based on relationship to lenticular nucleus)

Answer 13

1. ant limb: lenticular nuc, caudate
2. post limb: lenticular nuc, thalamus
3. genu: btwn A and P limbs
4. retrolenticular: behind lenticular nuc (inf visual field)
5. sublenticular: not seen in horiz sections, sup visual field

Question 14

hypothalamus

Answer 14

critical in autonomic, endocrine, emotional, and somatic fnctns, maintains homeostasis

Question 15

3 types of hypothalamus connections

Answer 15

1. interconnected w limbic system
2. output to pituitary
3. interconnects visceral/somatic nuc

Question 16

hypothalamic control of pituitary

Answer 16

sup hypophyseal br: cap bed in infundibulum and 2nd cap bed around endocrine cells, caps drain into portal vessels in ant lobe

inf hypophysela br: neurohypophysis , caps drain into cavernous sinus, delivers ant and post pit hormones to systemic circ

Question 17

what controls pituitary secretions

Answer 17

neuroendocrine cells

Question 18

2 types of neuroendocrine cells

Answer 18

1. parvocellular: end in median eminence (short axons)

2. magnocellular: end in post lobe (long axons)

Question 19

what do parvocellular cells give rise to

Answer 19

tuberoinfundibular tract

Question 20

2 hormones released by neurons in paravent and supraoptic nuclei

Answer 20

1. ADH/vasopressin

2. oxytocin: contract labor mm

Question 21

hypothalamic functions

Answer 21

1. autonomics
2. feeding
3. fight or flight
4. sleeping/waking, sexual arousal, memory

Question 22

hypothalamus and autonomics

Answer 22

ant hypo: stim produces parasymp effects (dec HR, constrictpupils, peristalsis)
post hypo: stim produces symp effects (increase HR, BP, dilate pupils)

Question 23

hypothalamus and feeding

Answer 23

-lat and VM nuc create appetite set point, can be altered by serotonin (anorexia = increased, bulemia = decreased)
stim lat nuc->feeding, lesion->refuse food
stim VM nuc->refuse food, lesion->feeding

*areas also key to fear and rage

Question 24

hypothalamus and fight or flight

Answer 24

• corticotrophin RH released by paravent nuc->ACTH release pituitary->increased cortisol from adrenal gland
• activation in lat prefrontal cortex

Question 25

other hypothalamic fnctns

Answer 25

- sleeping/waking - sexular arousal - memory

Question 26

hypothalamic inputs

Answer 26

1. forebrain (limbic structures): | 2. BS/SC

Question 27

forebrain as hypothalamic input

Answer 27

- info to mediate autonomic/somatic of some emotional states | - amygdala via stria terminalis, VAP

Question 28

BS/SC as hypothalamic input

Answer 28

- visceral and sensory info (IX and X) | - mainly DLF

Question 29

limbic system

Answer 29

- mainly cingulate and parahippocampal gyrus) - feelings/emotions from sensory inputs, evolved to promote survival so activity varies depending on physiologic needs - bridges autonomic/voluntary responses to environmental changes

Question 30

2 parts of limbic system

Answer 30

1. limbic cortex: 3 layeres allocortex of hippocampus and septal area and mesocortex in parahippocampal gyrus, cingulate, and insula 2. subcortical nuclei: amygdala (emotional responses), hypothalamus, nucleus accumbens and reticular form

Question 31

hippocampus

Answer 31

specialized area of cortex rolled up into medial temp lobe, critical to memory formation, esp declarative memory

Question 32

parts of hippocampus

Answer 32

1. dentate gyrus 2. hippocampus proper 3. subiculum

Question 33

hippocampus afferents

Answer 33

input from septal nuc and entorhinal cortex

Question 34

hippocampus afferent connections

Answer 34

1. afferent fibers from sensory cortex 2. entorhinal cortex projects to dentate gyrus 3. dentate neuron projects to CA3 4. CA3 neuron projects into fimbria and CA1 5. CA1 neuron projects to subiculum 6. subiculum projects to fimbria (alvear path) 7. subicular neuron projects to entorhinal cortex 8. entorhinal neuron projects to sensory cortex

Question 35

hippocampus efferents

Answer 35

- fimbria is an imp efferent - entorhinal neuron is largest efferent - fornix is continuation of fimbria, does outputs from subiculum and entorhinal cortex

Question 36

papez circuit

Answer 36

MEMORY 1. neurons in cingulate gyrus project back 2. projection into entorhinal cortex 3. projection into hippocampus 4. fornix 5. mammilary tract 6. projections from ant nucleus of thalamus to cingulate cortex

Question 37

types of memory

Answer 37

- short term: hold info briefly (phone number) - long term: stored, can be retrieved (explicit: facts/events, implicit: performing a learned motor fnctn) - working: needed for task at hand - consolidation: process of storing new info in long term

Question 38

amygdala

Answer 38

-primary association with fear

Question 39

nuclear groups of amygdala

Answer 39

1. medial: olfaction 2. central: hypothalamus, PAG, emotional responses 3. basolateral (HUGE): cortex; cent nuclei; emotional responses

Question 40

amygdala afferents

Answer 40

- all sensory assoc area have direct input to lat nuc | - all areas also linked to prefrontal cortex via assoc fibers so sensations can be cognitively evaluated

Question 41

amygdala efferent paths

Answer 41

1. stria terminalis (to hypothalamus and septal nuclei) | 2. ventral amygdalofugal path: also synapses with nuc accumbens

Question 42

kluver-bucy syndrome

Answer 42

- bilat temp lobe injury, iinvolves amygdala, parahippo gyrus - fearless, placid, no emotion, males are hypersexual: amygdala damage - inordinate attn to all sensory stim, pick up same object repeatedly: visual assoc cortex damage

Question 43

nucleus accumbens

Answer 43

stim: sense of well being, feeling "high" due to dopamine release AKA ventral striatum

Question 44

limbic loop in BG

Answer 44

- pleasure increases ventral striatal dopamine release from ventral tegmental area in midbrain - drive related info to influence movement/behavior - assoc stim with reward