Samenvatting Lectures Introduction into Neurosciences
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Cours
Introduction In The Neurosciences
Établissement
Universiteit Leiden (UL)
Een samenvatting van alle hoorcolleges en onderwerpen van het blok Introduction into the Neurosciences.
T1 Neuroanatomy
T2 Sensory Neurophysiology
-->(Nerve and muscle excitation, vibration sense of skin, retinal light sensitivity, visual field)
T3 Systemic Neuroanatomy
--> (somatomoto...
Summary Intro into the Neurosciences
Biomedical sciences year 2
Inhoudsopgave
1. Neuroanatomy……………………………………………………………………………………………………………………………………….
i. LT3 Neuroanatomy I&II
ii. LT4/5 Neuroanatomy III&IV
2. Sensory Neurophysiology…………………………………………………………………………………………………………………..
i. LT6 Sensory physiology
b. Neurophysiology practical
i. A1 Nerve and muscle excitation
ii. B1 Vibration sense of the skin
iii. C1 Retinal light sensitivity
iv. C2 The visual field
3. Systemic neuroanatomy…………………………………………………………………………………………………………...
a. 3.1 Somatomotor system
i. LT11 2nd Motorneuron
ii. LT 12 1st Motorneuron
b. 3.2 Subcortical motor systems
i. LT13 Subcortical motor system (?)
c. 3.3 Somatosensory system
i. LT7 Somatosensory system (lang)
d. 3.4 The visual system
i. LT9 Visual system (kort)
e. 3.5 Auditory and vestibular system
i. WL8 Auditory and vestibular systems (kort)
f. 3.6 Brainstem and reticular formation + 3.7 The autonomic nervous system
i. LT14 Brainstem, RF&ANS (--> van beau overgenomen)
g. 3.8 The limbic system (homeostasis, olfaction, memory, emotion: HOME)
i. LT10 Olfaction and taste
ii. LT15 Limbic system
h. 3.9 Development, memory & learning
i. LT16 Memory
4. Advanced Neurophysiology??.....................................................................................................
a. LT 17 neurotoxins
b. LT18 nueromuscular junction
c. LT19 mysathenia gravis
,Theme 1.
Neuroanatomy…………………………………………………………………..
LT3 Neuroanatomy I & II
NEURONS
Excitable elements:
Neuron consists of:
● Dendritic tree, which is the receptive field of the
neuron connected to a soma
● Soma (cell body), will or will not generate a
signal or action potential depending on the
threshold.
● Axon: signal travels along the axon (-->
synapses; axon hillock, synaptic terminals)
eventually reaching Telodendria and synaptic
terminals where signal is conveyed to the next
neuron.
Axonal conduction
Action potential: at the level of the axon hillock an all-or-non signal is created called AP which can
travel along axons, does not diminish and their presence is signalled to the next neuron at the
synaps.
Saltatory conduction: the conduction velocity along normal axon is very low, the myelin sheath
surrounding the axon increases this by its nodes of Ranvier (Na+ inflow can generate action
potential) and this is called saltatory conduction.
Neurotransmitter: at the synapse there is a change in carry of information from electric signal to
chemical messenger; neurotransmitters convey the message at the synapse.
Synaptic transmission:
, I. Action potential arrives at the synapse,
II. calcium ions will enter synaptic bouton,
III. smaller vesicles containing neurotransmitter fuse
with membrane,
IV. neurotransmitter diffuse across asynaptic cleft and
influence post-synaptic membrane by binding Ion
channels (Na+) that open/closes.
V. Ions enter → change in membrane potential
(called postsynaptic potential, different from
action potential because it can change).
A. PSP is excitatory when it causes the next
neuron to be more liable to generate action
potential or can be inhibitory when post
synaptic memrbane is less liable to
generate action potential.
PSP are small, variable and susceptible to
attenuation (signal diminishes travelling along the membrane.
CELLS OF THE NERVOUS SYSTEM
Flow of information through the nervous system
Sensor → afferent neurons → black box → efferent neurons → effector
Afferent neurons: convey info from sensors in periphery to the brain. Afferent includes 5 senses:
smell, taste, touch (somatic outside body, visceral inside body), hearing and vision.
Efferent neurons: convey info from brain to effectors in periphery. Efferent includes the effector
systems: somatomotor system (brain activates striated muscle) and visceromotor system (brain
activates smooth muscles, glands).
Damage
Depending on the type and location of brain damage, it has different effects/deficits and thus
different symptoms:
- Damage in afferent nervous system → sensory deficits causing partial loss of sensory
function
- Damage in efferent nervous system → effector deficits causing either partial loss of
somatomotor functions (pareses, paralysis) or partial loss of visceromotor functions
(visceral dysfunction)
- Damage in brain itself → black box deficits causing complex changes in cognitive functions
The axons of afferent and efferent neurons are often colocalized (peripheral nerves) or located in
close proximity (spinal cord, brainstem) so when damage occurs often at the sametime in effector
and sensor systems.
The type and location of the lesion determines what combination of deficits will ensue. With
knowledge of neuroanatomy, the location of the lesion can be deduced from the scale of symptoms.
The perikaryon: when a nerve is severed, only those parts connected to the soma/perikaryon will
remain and regenerate and the rest/peripheral part degrades and will have to regrow.
Central nervous system (CNS)
Neuroglia: glue, support cells, and hold the brain together. There are glia cells in the peripheral
nervous system and in the central nervous system.
Neurons: excitable elements.
Astrocytes: are most important and have many functions. Astrocytic extensions cover the entire
outside surface of the brain.
, Control the entrance of substances to the brain (blood-brain barrier). CNS neuronal
protection. Astrocytic extensions cover all uncovered surfaces of the neuronal somata,
dendrites and (unmyelinated) axons. This is for structural support and control of ECF by
uptake of K+ and neurotransmitters.
At the level of the capillaries exchange occurs:
- Glia limitans perivascularis: surrounds all bloodvessels = (part of) Blood-Brain Barrier.
- Glia limitans superficialis: borders on subarachnoid space = (part of) Brain-Liquor Barrier
Oligodendrocytes: myelin forming cells in CNS. (Unmyelinated axons are covered by astrocytes,
myelinated axons are covered by myelin sheaths)
Microglial cells: mononuclear phagocyte. Waste disposal. Are not part of the neuro-ectoderm but are
immigrants from mesoderm, that are the scavengers of the central nervous
system that, when activated, remove debris.
Ependymal cells: form a squamous to columnar epithelium that lines the
ventricular cavities. May be ciliated; cilia enable the cerebrospinal fluid to
circulate.
- The epithelium forms a permeable barrier between CSF and ECF.
- Ependymal cells also cover the choroid plexus, which is a very
vascular part for the production of cerebrospinal fluid (CSF)
- They also absorb waste and unnecessary solutes from CSF
Peripheral nervous system (PNS)
Satellite cells: similar in function to the astrocytes, they cover all neuronal membrane surfaces
except that covered by schwann cells. ---> PNS neuronal protection.
Schwann cells: They cover all axons in PNS with myelin.
Myelinating SC: myelin sheats for myelinated axons.
Non myelating SC: envelop non-myelinated axons. Unmyelinated axons form Remak
bundles.
SUBDIVISIONS
Anatomical CNS PNS
subdivision:
(Connected to sensors and effectors in Cables:
periphery by PNS) - cranial nerves,
- Brain in skull, - spinal nerves,
- spinal cord in vertebral canale. - ganglia (neurons living in PNS outside CNS)
Voluntary nervous system controls Involuntary nervous system consisting of:
skeletal muscles (somatic muscles) - Sympathetic NS (FFF)
thus: - Parasympathetic NS
- Motor - Enteric NS (gut)
- Sensor
Note:→ Do not confuse the words nerve, tract/fascicle, neuron and axon.
A nerve consists of a bundle of (afferent and or efferent) axons surrounded by connective tissue
sheath, and is located in the peripheral nervous system.
Tracts and fascicles etc consist of bundles of either afferent or efferent axons, and are present in the
central nervous system.
A neuron usually consists of an (afferent) dendritic tree, a cell body (soma), and an (efferent) axon
that branches into axon terminals.
The word ‘neuron’’ however often refers to just the cell body.
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