Lecture 12 - the Ancient Forebrain - Hypothalamus and Thalamus Flashcards
What are the wrinkles in the brain called?
Gyri and Sulci
Gyri - raised ridges of tissue
Sulci - rifts and valleys
What do the 4 lobes correlate to?
Frontal = Motor/Cognition Parietal = Sensory Occipital = Vision Temporal = Auditory
What parts of the brain can be seen from a ventral perspective?
spinal cord, the brainstem and the midbrain of the medulla and the pons
What is the cerebral hemisphere split by?
lateral fissure
lateral fissure is a major landmark in normal brains
What are fissures?
Enlarged Sulci
What are the other 2 lobes in the brain?
Insula and Limbic Lobe
What does the nervous system develop from?
neural tube (in which contains a space in the middle)
What does the space in the neural tube become?
the ventricles of the brain, where csf flows for homeostasis and support
What shape do the lateral ventricles adopt around the brain?
a C shape
What are the ventricles to neuroanatomists?
They are landmarks for particular regions of the brain
What does the forebrain consist of?
Cerebral hemispheres Limbic System Hypothalamus Thalamus Basal Ganglia
What does the embryo regionalise itself into?
Three germ layers
endoderm - Gives rise to gut, liver, lungs
mesoderm - gives rise to muscle and connective tissue
ectoderm - gives rise to skin (epidermis) and the nervous system
What is induced very early after gastrulation?
notochord andthe neural plate
what do signals from the notochord cause?
uneven proliferation and closing of the neural plate
What happens during the fusion event?
the neural plate forms a continuous and separated neural tube which is the precursor to the nervous system
In early stages of neural development, what provides important signalling cues?
the neural tube is still in close proximity to the mesoderm somites and notochord and also the epidermal cells of the ectoderm
and these provide important signalling cues
What does neural tube developing in different ways along the rostrocaudal axis cause?
cells in different regions of the neural tube will start to acquire regional identities
So we have formation of the different early brain regions and also the spinal cord. Driven by signals from the surrounding ectoderm and mesoderm.
What structures develop at the caudal end?
there is the spinal cord which is continuos with the hind, then mid then forebrain made up of the diencephalion and most rostrally the telencephalon
What specialist structures can we see at this early stage?
we can see that the thalamus and hypothalamus of the forebrain (diencephalon) are adjacent to the midbrain
The telencephalon including basal nuceli are next to this already suggesting a proximity which is also found in the adult brain.
What does grey matter structure mostly contain?
neuronal bodies
What does the hypothalamus control?
various autonomic body actions
hypothalamus receives afferent information and also send efferent information into various brain structures including the cortex, the brainstem and down the spinal cord.
Where is the hypothalamus located?
It is located inferiorly to the thalamus and lies adjacent to the third ventricle
What part of the hypothalamus controls feeding?
lateral hypothalamus
What can lesions in the ventromedial section cause?
over-eating
Which hormones are released by cells associated with eating?
Ghrelin
Leptin
How does the stomach release these hormones?
The stomach releases ghrelin at increasing amounts after finishing a previous meal
Adipocytes will release leptin if too much fat is being consumed
What does the arcuate nucleus have control over?
it controls feeding and satiety (inhibit feeding)
By leptin activating cells in arcuate nucleus, which neurotransmitters does it express?
MSH and CART
Where do the MSH and CART project to?
sympathetic neurons in the spinal cord,
neurons in the paraventricular nucleus
and neurons in the lateral hypothalmus
what happens in the process of satiety?
activate the visera for processing food.
They also suppress activity of lateral hypo neurons or suppress feeding through activation of lateral neurons. Finally, neurons in the paraventricular nucleus stimulate release of ACTH from the anteriro pitauitary.
What happens in the process of feeding?
A drop in leptin levels activtaes different neurons within the arcuate nucleus – NPY and AgRP releasing neurons which have an oppsoite effect – inhibiting paraventricular neurons and stimulaitng lateral neurons.
What can the dicephalon be split into?
can be split into different regios called the hypothalamus, the epithalamus the subthalamus and the dorsalthalamus
Why is the thalamus important?
The thalamus provides a kind of gateway to the cortex and is a major stop for sensory information beofre it is projected into the cortex
Which neurones is the thalamus made up of?
projection and inter - neurones
The thalamus has some white matter tracts which allows -____?
axons to project out into the brain
These white matter tracts are known as the internal medullary lamina (Landmark)
The nuclei of thalamus are receiving inputs from various inputs project the information to where____?
cortex where it may become consious information
What is the thalamus sometimes seen as?
a relay centre
What is the thalamus split into?
Specialist nuclei
They are named according to their anatomical location which is general a reflection of where they are compared to the white matter tracts which run through the thalamus
What is the function of the thalamus?
it appears to mediate and regulate sensory information for projection to other systems
What are the 2 examples of projections from the spinal cord?
The medial lemniscus carries information relating with touch
The spinothalamic tract carries info relating with pain
