Neuroanatomy + Neurochemistry Flashcards
Pupillary light reflex
Some light travels directly to pretectal area (not LGN), to Edinger-Westphal nuclei, which controls pupillary constriction via CN III.
Visual pathway
Optic nerve -> optic chiasm -> optic tract -> lateral geniculate nucleus (thalamus) -> visual cortex (posterior occipital lobe)
Basal ganglia - Components
= group of subcortical nuclei situated at base of forebrain and top of midbrain.
Components:
- Caudate + putamen (dorsal striatum)
- Nucleus accumbens + olfactory tubercle (ventral striatum)
- Globus pallidus
- Substantia nigra
- Subthalamic nucleus
Basal ganglia - Function
Associated with a number of functions including voluntary motor control, procedural learning, habit learning, conditional learning, eye movement, cognition, emotion.
The basal ganglia are inhibitory. They work with the cerebellum, which is excitatory, to allow smooth coordinated movement.
Basal ganglia - Neurotransmitters
Predominantly GABA-ergic efferent fibres, modulatory cholinergic fibres, and significant dopamine (in VTA and substantia nigra).
Nucleus accumbens
Component of the basal ganglia.
Involved in addiction.
Part of the reward pathway.
Hypothalamus - Function
Homeostasis
Hypothalamus - Inputs
- Nucleus of solitary tract (visceral sensation)
- Reticular formation (from spinal cord)
- Retina (from optic nerve)
- Circumventricular organs (monitor substances in blood)
- Limbic and olfactory systems
- Intrinsic receptors
Hypothalamus - Neural outputs
The lateral hypothalamus projects to lateral medulla, which contains cells involved in autonomic control. In this way, the hypothalamus can control HR, vasoconstriction, digestion, etc.
Hypothalamus - Endocrine outputs
- Large hypothalamic cells send axons directly to posterior pituitary, where they can release oxytocin and vasopressin directly.
- Smaller cells send axons to base of pituitary and release releasing factors into capillaries of anterior pituitary, which secretes hormones in response, such as TSH, ACTH, etc.
Orexin
Also called hypocretin.
Produced by lateral hypothalamus, but not during sleep.
Deficient in narcolepsy.
Medial preoptic nucleus
Part of hypothalamus.
Contains sexually dimorphic GnRH nucleus which releases gonadotrophic releasing hormone.
Supraoptic nucleus
Part of hypothalamus.
Releases oxytocin and vasopressin.
Paraventricular nucleus
Part of hypothalamus.
Releases oxytocin, vasopressin, and corticotrophin releasing hormone.
Anterior hypothalamic nucleus
Part of hypothalamus.
Involved in thermoregulation.
Suprachiasmatic nucleus.
Part of hypothalamus.
Involved in circadian rhythm (some fibres from optic nerve project here).
Releases vasopressin.
Ventromedial nucleus
Part of hypothalamus.
Involved in satiety, sexual behaviour.
Arcuate nucleus
Part of hypothalamus.
Involved in feeding.
Releases dopamine.
Lateral nucleus
Part of hypothalamus.
Involved in hunger, thirst.
Dorsomedial hypothalamic nucleus
Part of hypothalamus.
Involved in BP and HR.
Mammillary nuclei
Part of hypothalamus.
Act as a relay for impulses coming from the amygdala and hippocampus, via the mamillothalamic tract to the thalamus.
Therefore involved in memory.
Thalamus - Function
Regulation of sleep/wake
Processing/relaying of sensory information
Arousal/consciousness
Thalamus - Connections
- to the hippocampus via mammillothalamic tract (mammillary bodies and fornix)
- to cerebral cortex via thalamocortical tract
- from spinal cord via lateral and anterior spinothalamic tracts
Thalamic syndome
Contralateral hemi-anaesthesia + mood swings
Frontal lobe - Function
“Action cortex”
Involved in actions such as skeletal and ocular movement, speech control, expression of emotions.
The prefrontal cortex is involved in reasoning.
Orbitofrontal syndrome
Impulsivity, disinhibition.
Also called pseudo-psychopathy, Witzelsucht.
Mediofrontal syndrome
Apathy, akinetic mutism
Dorsolateral frontal syndrome
Impaired executive function
Tests of frontal lobe function
- finger tapping
- design or verbal fluency
- Wisconsin card sorting test
- tests of language, numeracy or decision making
- Stroop test
- Tower of London
- trail-kaing
Anterior cingulate
Part of frontal lobe
Involved in detection of errors, anticipation and preparation for tasks, emotion regulation.
Involved in mood disorders.
Broca’s area
Dominant inferior frontal cortex
Involved in generation of speech
Non-dominant dorsolateral/orbitofrontal cortex & insula
Depersonalisation
Temporal lobe - Function
Involved in processing sensory information.
- Visual memories (communicates to hippocampus, mediated by amygdala)
- Processing auditory (primary auditory cortex and superior temporal gyrus) and visual (ventral temporal cortex) input
- Language recognition
- New memories (hippocampi in medial temporal lobe)