Wk.6 L1 - Nervous system (1) Flashcards
LO
- Explain how a neural circuit structure works to sense stimuli from external world (sight, sound, smell, taste, touch, temperature), or from inside the body (visceral pain, blood pressure, body position in space and time…), and then interprets these stimuli resulting in movement, emotion and behaviour.
- Describe how compartmentalisation and organisation of cells in the nervous system, making up distinct anatomical components of the brain, spinal cord and peripheral nervous system, works together to enable sense, movement and behaviour.
Sensory Systems (afferent)
Signal direction comes from periphery and is triggered from outside or inside body, goes towards CNS for interpretation
Transduced by:
* Pressure/ thermoreceptors on skin
* Baroreceptors in blood vessels
* Photoreceptor in retina
* Chemoreceptors, olfactory & taste molecule receptors
Motor systems (efferent)
Direction of signal is from CNS towards periphery
- Voluntary
- Involuntary
Integration (decision making)
In CNS
Neuronal connections integrate sensory input with past experience encoded in memory.
This combines to enable us to experience and perceive the world in a certain way as well as decide how to move and behave.
CNS
Cerebral hemispheres
Cerebellar Hemispheres
Brain stem
Spinal cord
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Brain stem
Midbrain
Pons
Medulla Oblongata (continuous w/ spinal cord)
Spinal cord
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PNS
Nerves:
31 pairs of spinal nerves
12 pairs of cranial nerves (merge & branch together to form nerve plexus’ - carry sensory and motor axons into and out of the CNS)
Ganglia
Groups of neuronal cell bodies
Sensory ganglia:
* Connented to spinal cord or brainstem
* Contain primary sensory neurons for visceral or somatosensation
Autonomic Ganglia:
* Seperate sympathetic & parasympathetic (for autonomic motor effect)
CNS tissue - White matter:
White matter:
- Contains glia and myelinated axons (making it white)
- Information travels in white matter tracts
- If damaged, communication between CNS regions are lost
- Has a blood supply
Brain = Grey outside (GOB)
Spinal cord = White out
CNS tissue - Grey matter:
Grey matter:
- Contains glia, neuronal soma, dendrites, axon terminals and synapses
- Integration of information occurs here
- Have a blood supply
Brain = Grey outside (GOB)
Spinal cord = White out
PNS tissue structure
Nerves:
Groups of myelinated and unmyelinated axons travelling towards and away from CNS
Ganglia:
Groups of neuronal cell bodies outside of the brain or spinal cord
- Autonomic ganglion contain synapses
- Sensory ganglion contain NO synapses (synapses in CNS)
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Inside tissues - cytoarchitecture
Spinal cord:
- Dorsal rootlets (afferent)
- Ventral rootlets (efferent)
- 2 semetrical halves seperated by anterior & posterior medial fissures
- Grey matter has 2 ventral and 2 dorsal horns
- White matter is peripheral and has no synapses (only axon tracts)
- Dorsal and Ventral roots join to form spinal nerves
Spinal Cord section
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Neuronal soma found in ventral horn of grey matter
Lateral horn of spinal cord grey matter
Only in thoracic and lumbar spinal cord segments
Soma of pre-ganglionic autonomic motor neurons
Spinal cord grey matter
Soma of neurons and their dendritic processes
Lots of synaptic connections
Lower motor neuron (multipolar projection neuron)
- sends its axon out of the grey matter into the ventral rootlets to skeletal muscle
- Forming synapses at the neuromuscular junction
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lower motor neuron
Axon is in CNS and PNS
- Soma and dendrites are in the CNS
Spinal cord white matter
Axons travelling in tracts
glial cells
blood vessels
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Inside a sensory ganglion (PNS)
Eg.
Dorsal root ganglion:
- Contain primary sensory neurons
- No synapses, only form in dorsal horn of grey matter
- Contain the Sensory neuron soma (surrounded by satellite cells)
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Inside brain
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White matter tracts scattered throughout Pons
Cerebrum
2 Hemispheres, upper part of brain
~80% volume of brain
Outer folded cortex of grey matter and inner white matter
Plus collections of grey matter surrounded by white matter called basal nuclei
Cerebral cortex folds
gyri and sulci
Gyrus = inwards ‘u’
Sulcus = outwards ‘n’
Cerebral cortex 6 layers of neurons (laminae)
Layer I is the most superficial (outside) and layer VI is the deepest layer (inside)
Layers III and V contain “pyramidal” neurons
pyramidal” neurons
send long axons out of to form synapses in other parts of the cerebral cortex/ brain/spinal cord/ areas of grey matter
Cerebellum
- 2 hemispheres
- Posterior of brain
- Deeply folded lobes with ‘folia’
- Contains highest density of neurons within the CNS
Outter grey matter regions and Inner white matter region
Outter grey matter regions of cerebellum
Molecular
- Superficial
- Synaptic
Purkinje
- Intermediate
- Singular layer of purkinje neurons
Granular
- Deep
- Synaptic
inner white matter of cerebellum
Deep to granular layer
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Glia - Other cells of the nervous system
CNS:
Oligodendrocytes:
- Myelinating cells/ glia of CNS
Ependymal cells:
- Epithelia cells that line the ventricles of the brain
Microglia
Atrocytes
PNS:
Schwann cells:
- Myelinated cells of PNS
Satellite Cells:
- Supporting glial type cells
