W5 Nervous system structure through development Flashcards
Neural plate
17 days
Endoderm = viscera lining,
Mesoderm = bones and muscles.
Ectoderm = skin and nervous system (neural plate)
Neurulation (22days)
Neural plate curves and forms a neural tube. Neural tube becomes every cell in the CNS. And the neuronal crest becomes the PNS.
Somatic nervous system
voluntary control, moves all of our muscles. Innovation of things coming from the soma (the neural tube)
What neurons form from the nerual crest?
Sensory neurons whose cell bodies lie in the dorsal root ganglia (spinal cord).
Autonomic neurons ( post ganglionic parasympathetic neurons, enteric neurons)
Not neurons but other cells such as chromaffin cells and Schwann cells derive from the neural crest.
Why are women advice to take folic acid when trying to conceive and during pregancy
Failure to appropriately close the nural tube, specific sequence of gene expression adn influened by environement, folic acid = reduces 90%. Because it influences DNA synthesis.D
Differentiation
Different parts of the neural tube differentiated. At the rostral face more differentiation because the forebrain is very complex. Separate into 3 primary brain vesicles.
Differentiation- 3 primary brain vesicles
Separate into 3 primary brain vesicles:
Rostral = prosencephalon or forebrain.
The middle of the neural tube = midbrain or mesencephalon
Caudal part of the neural tube = hindbrain or rhombencephalon
Motor neuron
Efferent transmission
Sensory Neuron
Afferent Transmission
Forebrain differentiation
White matter = coming in and out of the brain. Corpus callsum = huge white matter tracked, connects both hemispheres, feeding information from one to another.
Midbrain differentiation
Midbrain = has the cerebral aqueduct. Tectum = dorsal aspect of midbrain. Tegmentum in the middle. Huge white matter tracks bring information from motor cortex to the spinal cord.
Superior colliculus = in vision
Hindbrain differentiation
Cerebellum formed by the rhombic lips. (rostral part of the hindbrain)
Medulla pyramids form at the front.
Cerbellum
Co-oridnatin of movement, balance, posture. 10% CNS volume, 50% CNS neurons.
Vestibulocerebellum = oldest, balance. Spinocerebellum = muscle stretch receptors. Cerebrocerebellum = projections from sensorimotor cortex = motor coordination.
The cerebral cortex = 3 types
Hippocampus, Olfactory, Neocortex.
Hippocampus
(first developed) = memory, if you sense chemical you want to remember not to go to it again (survival) found in each temporal love memory, only 3 layers.
Olfactory cortex
= receives sensor information. (Smells), when we sense chemicals around use, the information gets sent to this cortex. (even in primitive animals, for survival (food or poison?) (simple, bellow the hippocamps (orange and green)
Neocortex
= (new ish, all mammals have the neocortex, part of the brain that differentiates between animals’ mammals) = the neocortex is far bigger than other animals. (not just survival)
Neocortex is divided into
into different lobs. Looks for key gory and sulci
lateral sulcus + central sulcus + parieto-occipital sulcus
Frontal lobe, Temporal lobe, occipital love, parietal lobe.
The neocortex has 6 layers
Layers = the exact structure of these layer different between regions of the neocortex.
Thin layer, clinging to the whole brain = Pia
Molecular layer = just dendrite and axons, but no cell bodies (lots of synapses.)
Example of Layers in the Neocortex
Ext. Granular layer, Ext Pyramidal layer, Int. Granular Layer, Int. Pyramidal Layer (often larger than the other layer, larger cells), Fusiform Layer = cellular layers
Areas of the neocortex - Secondary Sensory Areas
Secondary sensory areas: usually located near the primary areas, will start to process the information and put it into context
Areas of the neocortex - Primary Motor Areas and Rest of cortex association areas
Primary motor areas (just within the frontal lobal) ,
Rest of cortex association areas (= space between, this part in humans that has expended in evolution).
Different Stains
To see different layers of the neocortex.
Golgi, toluidine blue(cell body), Wigert-PAL (myelin)
Brodmann’s cytoarchitectural map
= mapping the neocortex.
He told us which layers were where and looked like but couldn’t tell us their functions. Using lesions or direct stimulation to understand their function (lesions done on animals to see the deficit would be.)
Maping the cortex using non invasive funcitonal imaging
- Positron emission tomography (PET; as seen in the figure).
- Functional magnetic resonance imaging (fMRI).
- Electroencephalography (EEG).
Areas of the neocortex - Primary sensory area
Primary sensory areas (areas that directly receive information from the world around us.),
Neocortex = Madial vial = Limbic lobe
= different bits work together with a common goal. Cortex of cingulate gyrus. Cortex on medial aspect of temporal lobe. Hippocampus. (processing emotion)
Neocortex = hidden areas = insula
functionis range from snesorimotor processing to emotional regulation
The basal forebrain
basal ganglia and amygdala.
The Thamlamus (forebrain)
= gate way to the cortex. Diencephalon. (relay information). Over 50 nuclei. Relay station. Also more than a relay station. Connects to neocortex via projection fibres.
The hypothalamus
11 major nuclei
Latreal hypothalamus: motivated behavior, behavioral outcomes, things you might do to change your situation, more conscious.
Trying to achieve a steady state through homeostasis. Master regulator of homeostasis
Homeostasis
Contextual inputs => Integration by hypothalamus
Disruption to a vital parameter => Sensory inputs => Integration by hypothelamus => Autonomic NS, Neuroendocrine and Behavioural => Restoration of vital parameter within physiological range.
Supraoptic nucleus
= feeds information into the posterior pituitary (Neurohypopysis)
Paraventricular
= has neurons that feed information to anterior (Adenohypopysis) and posterior pituitary and send information outside of the hypothalamus.
Adenohypopysis
Parvocellular neuron => Capillary Bed => Release Hormones (neurohormones): travel in the blood stream => Adenohypopysis and stimulate other hormones to be released.
Troph cells stimulated by releasing hormones from Parvocellular neurons of the hypothalamus
Neurohypopysis
Magnocellular neurons (large cell bodies) => Neurohypophysis => release into blood stream, send hormones to body.
Releases hormones from the Magnocellular neurons directly into systemic circulation.
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The autonomic Nervous system (ANS)
Involuntary.
Two efferent pathways: Sympathetic (aware, flight/flight) + Parasympathetic (relaxed).
Innervate effectors: Smooth muscle + Cardiac muscle + Glands (cortisol, adrenalin)
ANS can fucntion wihtout th hypothalamus
Sensory (afferent division) + Degree of hypothalamic control depends on the parameter=> brainstem nuclei => Motor (efferent) division.
The hypothalamus has variating degrees of control, depending on what information is coming in, depend on how much the hypothalamus controls
Which of the following requires greater input from the hypothalamus?
Regulation of body temperature.
general organisation of ANS
2 types of neurons involve:
Preganglionic neurons, their bodies will always sit in the CNS (spinal cord, brain),
Postganglionic neurons in the PMS. Preganglionic neurons
Nicotinic AChR
Inotropic, will generate an expiratory potential.
What does the Corpus callosum project
Large amounts of commissural fibres - connect between hemispheres. The porkection fibres link to non-cortical areas.
Nuclei of the hypothalamus
Paraventricular nucleus
Posterior Pituitary/Neuohypophysis
Anterior Pituatery/Adonohypophysis
Supraoptic nucleus
Where are the sensory receptors located (ANS)
Internal organs and blood vessels
Afferent fibres - ANS
Sensory division. Visceral nerves (cranial nerves)
Efferent Fibres and Effectors - ANS
Motor division.
Efferent Fibers: Autonomic nerves (sympathetic, parasympathetic.)
Effectors: smooth muscle, cardiac muscle, glands
Vagus Nerve
Cranial Nerve X, carries ~80% of total parasympathetic ourflow. Vagus nerves also corries tonnes of viseral afferents (vagal nerve stimulation)
Sympathetic Organisation - ANS
Dorsal Horn
Intermediate Grey Zone
Intermediolateral Cell Column
Lateral Horn
Ventral Horn
Norepinephrine are release to effecors from postganglionic fiber (Smooth/Cardiac muscle, gland)
