Neuroanatomy Part 2 Flashcards
Forebrain: Diencephalon
>. Thalamus >. Hypothalamus >. Pituitary Gland >. Pineal Gland: HPA axis neuroendocrine control system for initiating /regulating/terminating secretion of glucocorticoids.
Thalamus
(relay station for sensory input)
> . Lateral geniculate nucleus (LGN) relay for vision. Receives fibers to retina via the optic tract, and projects to primary visual cortex
> . Medial geniculate nucleus (MGN) relay for hearing. Receives input from auditory system and projects fibers to primary auditory cortex.
> . Ventral lateral nucleus (VL) relay for the motor system. Receives inputs from the cerebellum and basal ganglia sends axons to the primary motor areas of the cortex.
Diencephalon: Hypothalamus
- Located at inferior portion of thalamus.
- Combined with the pituitary and adrenal glands, it regulates hormone (endocrine) function
- Hunger, thirst, body temperature, sexual arousal, perspiration, BP, Heart rate, pupil dilation, circadian rhythms, sleep
- Plays a major in homeostasis, control and regulation of the autonomic system
Diencephalon: Pituitary and Pineal Glands
> . Pituitary Gland: Known as Master gland through which hypothalamus controls other endocrine glands (e.g., the adrenal glands)
. Pineal Gland: Secretes melatonin which influences sexual development and sleep cycles
. Mammillary bodies: A protrusion of the bottom of the brain at the posterior end of the hypothalamus, involved with recognition memory and olfactory memory
Forebrain: Telencephalon
> . Cerebral Cortex - The outermost layer of gray matter making up the superficial aspect of the cerebrum. Mostly composed of Neocortex. Made up of mostly glia (support cells), cell bodies, dendrites and interconnecting axons of neurons Neurons in the cerebral cortex are arranged vertically in columns.
. Neocortex - Cerebral cortex very convoluted, 2/3rd brain surface is found in sulci and fissures
. Fissures: Very deep grooves on the surface of the brain (e.g the longitudinal fissure separates left and right hemispheres)
. Sulci/Sulcus: a groove (or depression) in the surface of the cerebral hemisphere, smaller than a fissure. E.G., the central sulcus separates the frontal lobe from the parietal lobe
. Gyri/Gyrus: a convolution (ridge) of the cortex of the cerebral hemispheres, separated by sulci or fissures
Cortical Connections & Cortex Lobes:
Myelinated axons run in three directions
- Association fibers connect places within a hemisphere, e.g., the visual system
- Commissural fibers connect one gyri in one hemisphere to the corresponding gyri in the other hemisphere (e.g., corpus callosum)
- Projection fibers transmit impulses to and from the cerebral cortex and spinal cord (eg internal capsule)
Frontal Lobe
Frontal lobes are interlocked with the limbic system and striatum
“Senior executive” of the brain and personality
Divided into three areas
-Motor cortex
-Premotor and supplementary
-motor cortex
-Prefrontal cortex
Parietal Lobe
> . Two broad functions: Somatosensory processing and sensory integration
. Damage can result in difficulty reading, recognizing people and objects, ability to multitask, mathematical ability, poor spatial ability
Occipital Lobe
Primary function visual processing
Two main areas primary visual cortex (striate cortex) and visual association cortex
Damage results in visual perception and cortical blindness,
Temporal Lobe
Auditory information - Receptive language (Wernicke’s Area) - Higher order visual processing - Learning and memory Damage can result in disturbance of visual perception, selective attention of auditory and visual input, language comprehension, impaired long term memory, altered personality and sexual behaviour
Limbic System: Hippocampus
•Plays a significant role in the consolidation
of new memories, facts and events
•Case of H.M (Henry Molaison)
•Bilateral medial temporal lobectomy
to cure his epilepsy.
•Neurosurgeons performed surgical resection of anterior section of his hippocampi, amygdala
Profound memory deficits
Limbic System: Amygdala
- Group of nuclei located deep in medial temporal lobes
- Receives input from somatosensory areas and limbic structures
- Primarily controls autonomic responses involved in processing emotional states (fear and arousal)
- Bodies “alarm” system for fear
- Result of amygdala hyperactivity contributes to hypervigilance, emotional dysregulation, and disturbed interpersonal relations.
- Anxiety Disorders , PTSD and Social Phobias as a result of hyperactivity in Amygdala
Limbic System: Cingulate Cortex
Situated in medial aspect of cerebral cortex, lies above corpus callosum
•Receives input from thalamus and neocortex and projects to entorhinal cortex
•Involved in emotional processing, learning and memory
>. Fornix “c” shaped fibre bundle
>. Interconnects cerebral hemispheres, septum and hypothalamus
>. Damage to fornix results in memory loss, in particular recalling long term information
Basal Ganglia: Striatum
- Includes caudate nucleus, putamen and ventral striatum
- Major point of entry into basal ganglia circuitry
- Receives input from most of the cortical areas and projects inhibitory outputs to globus pallidus and substantia nigra
- Involved in planning and selection of movement
Basal Ganglia: Substantia Nigra
•Latin for black substance •Located in midbrain •Two parts: pars compacta (input to Basal ganglia circuit, supplies dopamine to striatum) & pars reticulate (output from basal ganglia to other structures) •Important role in reward and movement •High level dopaminergic neurons •Parkinson Disease: results from loss of dopamine in Substantia Nigra
