UNIT 8 - DIENCEPHALON AND BASAL GANGLIA Flashcards
DIENCEPHALON & BASAL GANGLIA
Four structures in Diencephalon
Thalamus
Hipothalamus
Subthalamus
Epithalamus
CNS develops
As a hollow tube that develops swellings that become forebrain, midbrain, and hindbrain
Role of thalamus (CENTRE OF FOREBRAIN)
The thalamus is the gateway to the cerebral cortex
Conveys sensory, motor, and autonomic information from the brainstem and spinal cord
All sensory projections are first processed through the thalamus
Except for the olfaction
What are the series of nuclei that the thalamus is sub divided by?
They divide in (Thalamic) into: - Anterior - Medial - Lateral Divided by internal Y-SHAPED medullary lamina (White matter)
Also divided into functions:
Specific
Non-Specific
Association Nuclei
Intralaminar nuclei vs reticular lamina
Intralaminar nuclei: they play a role in activating or maintaining arousal of the cortex
Reticular nuclei: play a role in the sleep-wakefulness cycle
Specific nuclei (VENTRAL PART)
RELATION BETWEEN BODY AND BRAIN:
- Specific nuclei that receive specific sensory signals and project to specific sensory and motor areas of the cortex
E.g ventral posterior (VP) nucleus receives somatosensory information to the trunk, limbs, and head that relied on a specific part of the primary somatosensory cortex
(Most signals sent to nuclei specific)
Non-Specific Nuclei (Dorsal Part)
SAME AS SPECIFIC BUT IN DIFFERENT AREA
PART OF THE GENERAL AROUSAL SYSTEM (association areas & limbic system)
Can also be association nuclei: cause they do not receive sensory signals, but receive input from other areas of the brain -> then sent to the cortex
Function of anterior nuclei group:
Receive signals from the hypothalamus and project the cingulate gyrus.
-Attention, memory, learning
Thalamic nuclei somatosensory information seen in:
Somatosensory: Retrograde thalamic denigration.
LGN (lateral geniculate nucleus): Damage to the left occipital lobe reduces activity in the left (vision)
Thalamic nuclei somatosensory information seen in:
Retrograde thalamic denigration.
LGN (lateral geniculate nucleus): Damage to the left occipital lobe reduces activity in left (vision)
Role of hypothalamus
The main controller of ANS - AUTOMATIC NERVOUS SYSTEM
(like feeding, drinking, sex, sleep)
- Connects with the body through blood stream
- Homestatis
- Influence ANS and CNS to release hormones into the bloodstream
HYPOTHALAMUS (HOMOASTASIS)
- Help maintain homeostasis (in internal + external environment)
Raphe nucleus (brainstem) controls temperature regulation behavior
HYPOTHALAMUS (PITATRY GLAND)
It is an endocrine gland attached to the hypothalamus via the pituitary stalk
- System blood vessels connect hypothalamus + anterior pituitary gland
- ALSO hypothalamus stimulates the release of hormones from the posterior pituitary gland via neural connections, rather than blood cell
“Gonodatroping-releasing hormone released by hypothalamic neurosecretory cells causes the anterior pituitary gland to release gonadotropic hormones into the bloodstream” Gondotropic (physiology + behavior)
Hypothalamus
- Lateral Zone
- Periventricular zone
- Medial Zone
Lateral Zone: Controls food and water intake
- (Lack of eating = aphagia)
- (Lack of drinking = adipsia)
Periventricular zone: Role in regulating the release of hormone from the pituitary gland
Medial Zone (various nuclei) - Suprachiasmatic nucleus: detect sensory fiber from the retina to communicate via pineal gland to control the sleep cycle
- Mammillary nucleus in the mammillary body: Inputs from the hippocampus (via fornix); to anterior nuclei of thalamus - memory
- Limbic system (Papez Circuit) = important for motivation and emotion
Role of sub-thalamus
Voluntary movement
Subthalamus - Contains two nuclear groups:
- Subthalamic nucleus: (ventral) = important for movement, the ability to stop yourself.
(substantia nigra + globus pallidus) - Zona incerta: (brainstem) = movement control
Role of epithalamus
Regulate sleep cycle and resistance agains nicotine
What structure does Epithalamus consist of?
Consist of two structure:
- Pineal Gland
- Habenula
Epithalamus (PINEAL GLAND) + phototherap?
The pineal gland lies just above the superior colliculus (midbrain) it’s an endocrine gland that synthesizes and secretes melatonin.
Governed by (suprachiasmatic nucleus): regulate the release of melatonin from the pineal gland.
Phototherapy: exposure to bright light for several hours a day: during different times of day, they can bring or push back melatonin secretion to resynchronize sleep and melatonin cycle, reducing symptoms
Epithalamus (HABENULA)
Role in addiction: inhibit the reinforcing effect of nicotine
(those who are less sensitive - are more likely susceptible to addiction)
Basal Ganglia: (CPG)
IMPORTANT FOR VOLUNTARY MOVEMENT (Motor cortex)
- It makes the composition of input and output form LOOPS, which allow DIRECT and INDIRECT CONTROL of voluntary movement
Lies beneath the cortex and consists of the:
- CAUDATE NUCLEUS & PUTAMEN (collectively known as the striatum):
lentiform. - GLOBUS PALLIDUS. (internal-external)
Basal ganglia (DIRECT + INDIRECT MOVEMENT)
Motor and somatosensory send axon to > striatum (caudate nucleus + putamen) which tun connect to internal and external globus pallidus.
> the internal and external globus pallidus. turn connect to the cortex to form a loop.
= Therefore basal ganglia have access to somatosensory info & to movement
Excitatory = increase activity (GLUTAMATE)
Inhibitory decrease activity (GABA)
Direct pathway (EXCITATORY): facilitates movement (when we want them to occur) - Globus pallidus does not inhibit the thalamus
Indirect pathway (INHIBITORY) inhibition of movement (when we don’t want them to occur)
Basal Ganglia (HYPERDIRECT)
Pre supplementary motor area which directly excites the subthalamus:
> INHIBIT MOVEMENT > Inhibits movement much faster
E.g out running, you stop at a red light (indirect pathway) light turns green, you initiate movement (direct pathway). The car comes by fast and you immediately stop (hyper direct)
Basal Ganglia: DOPAMINERGIC PATHWAY
Substantia nigra - stratum (niigrostratal system)
- important for influencing voluntary movement
They use dopamine (excitatory or inhibitory) to degeneration causes: Parkinson disease
Basal Ganglia: HUNTINGTON DISEASE
Neurodegenerative disease caused by degeneration of GABAeric and CHOLINERGIC (acetylcholine) neurons in the striatum.
- Indirect pathway (when we don’t want them to occur) = stopping unwanted body movement
