Nervous system overview I Flashcards
list two types of nervous systems:
- central nervous system (CNS)
- peripheral nervous system (PNS)
CNS: features
- brain
- spinal cord
PNS: features
- all nervous tissue outside CNS
- somatic nervous system (SNS)
- autonomic nervous system (ANS)
- enteric nervous system (ENS)
somatic nervous system: general features
- voluntary somatic motor neurons -> skeletal mm
autonomic nervous system: general features
- involuntary autonomic motor neurons
- parasympathetic/ sympathetic
- smooth mm, cardiac mm, glands
enteric nervous system: general features
- involuntary enteric motor neurons (in enteric plexuses)
- smooth mm, glands, endocrine cells of GI tract
CNS: nerves involved
- brain
- cranial nerve (CN II): optic nn
- spinal cord
PNS: nerves involved
- CN I, III-XII
- spinal nerves (31)
- peripheral nerves
- neuromuscular junctions
where does neural tissue arise from during development:
ectoderm (neuroectoderm)
neural tissue comprises of: eg
- neurons
- neuroglia (glia) which are non-neuronal cells which support neuronal function
neurons: definition
- excitable cells
- electrically active: which can rapidly alter voltage across cell membrane
neurons: function
- transduce/ transfer info
- communicate w other cells
- bring physiological changes in the body
neurons: 3 categories
- sensory neurons/ receptors
- interneurons
- motor neurons
sensory neurons/ receptors: features
- detect/ transduce stimuli arising from outside (light, sound) or inside (blood pressure, muscle stretch) body
- transmit resulting (afferent) neural signals to CNS for processing
interneurons: features
- connect neurons to one another in CNS
- allow CNS to communicate w sensory/ motor neurons
- forms circuits for processing neural info
motor neurons: features
- carry efferent signals from CNS to effector organs to bring about change
- eg. contraction of muscle tissue, release of substances from a gland
name types of neurons:
- unipolar
- bipolar
- multipolar
neuroglia: definition
- non-neuronal cells that are critical to function of neurons
neuroglia: functions (5)
- physical support for neurons
- supply nutrients/ oxygen to neurons
- electrical insulation of neurons
- destroy pathogens and remove dead neurons
- ? info processing etc.
neuroglia: main types
- astrocytes
- oligodendrocytes and Schwann cells
- microglia
- ependymal cells
astrocytes: function
- CNS
- transport nutrients (glucose) from blood vessels to neurons
- remove neurotransmitters (glutamate and GABA) released by neurons during synaptic transmission (stop excessive transmitting)
- regulate extracellular potassium conc.
- excitable cells can communicate w other astrocytes/ neurons to influence synaptic connectivity
- most common CNS neuroglia
oligodendrocytes and schwann cells: function
- oligodendrocytes (CNS)
- schwann cells (PNS)
- generate myelin sheaths surrounding axons of neurons
myelin: features
- part of cell membrane which wraps around axon in spiral fashion
- white fatty substance ‘white matter’
- rich in lipid (effective electrical insulation)
- critical for rapid (saltatory) conduction mode of action potential
microglia: function
- CNS
- immune effector cells
- phagocytose cell debris following injury/ pathogens in case of infection
- brain development/ homeostasis
- promote regrowth/ remapping of damaged neural circuitry
- involved in neuronal/ synaptic plasticity
ependymal cells: features/ function
- line ventricles (fluid filled cavities) in brain/ central canal of spinal cord
- assist in producing CSF
- microvilli beat to circulate CSF
CSF function:
cushion and supply nutrients to brain
grey matter of CNS:
- cell bodies and dendrites of CNS neurons/ some glia
- greyish-pink due to Nissl bodies (rough ER) in cells/ blood
- location of synaptic connections btw neurons
white matter of CNS:
- axons of CNS neurons
- myelin sheath (oligodendrocytes) give white appearance: high lipid content
how are neurons organised:
- layers (laminae)
compact clusters of neuronal cell bodies:
- nuclei in CNS
- ganglia in PNS
neural circuits: general features and eg.
- neurons don’t function in isolation: in circuits
- vary in complexity, connectivity, function
- eg. myotactic (knee jerk) spinal reflex loop: lil neuronal processing
neural circuits: complex eg.
pain matrix:
- governs perception and interpretation of painful stimuli
neural circuits: pain matrix areas involved
- multiple brain areas which have non pain functions also
- incl areas responsible for immediate physical response (pain detection, discrimination, avoidance)
- also pain-related mood/ emotion (anger, depression, anxiety, stress)
development of CNS: most basic embryonic brain regions (4 wks)
- forebrain
- midbrain
- hindbrain
development of CNS: name further developed embryonic brain regions (5 wks)
- telencephalon
- diencephalon
- mesencephalon
- metencephalon
- myelencephalon
development of CNS: forebrain forms into in embryo
- telencephalon
- diencephalon
development of CNS: midbrain forms into in embryo
mesencephalon
development of CNS: hindbrain forms into in embryo
- metencephalon
- myelencephalon
development of CNS: name brain structures in children/adults
- cerebrum
- diencephalon
- midbrain
- pons
- medulla oblongata
development of CNS: telencephalon forms into in children/adults and features
cerebrum:
- cerebral cortex
- white matter
- basal nuclei
development of CNS: diencephalon forms into in children/adults and features
diencephalon:
- thalamus
- hypothalamus
- epithalamus
development of CNS: mesencephalon forms into in children/adults and features
midbrain:
- part of brainstem
development of CNS: metencephalon forms into in children/adults and features
pons:
- part of brainstem
- cerebrum
development of CNS: myelencephalon forms into in children/adults and features
medulla oblongata:
- part of brainstem
sagittal plane:
separates into L and R
coronal plane:
separates into front and back
transverse plane:
separates into top and bottom
rostral:
towards beak
caudal:
towards tail
ventral:
belly
dorsal:
back
cerebrum: aka and function
- aka telencephalon
- conscious thought processes, intellectual functions
- memory storage and processing
- conscious/ subconscious regulation of skeletal muscle contractions
diencephalon: aka and function- thalamus
- relay and processing centres for sensory info
diencephalon: aka and function- hypothalamus
- centres controlling emotions, autonomic functions, hormone production
mesencephalon: aka and function
- aka midbrain
- processing of visual and auditory data
- generation of reflexive somatic motor responses
- maintenance of consciousness
metencephalon: aka and function
- aka cerebellum
- coordinates complex somatic motor patterns
- adjusts output of other somatic motor centres in brain and spinal cord
metencephalon: aka and function
- aka pons
- relays sensory info to cerebellum
- subconscious somatic and visceral motor centers
myelencephalon: aka and function
- aka medulla oblongata
- relays sensory info to thalamus
- autonomic centres for regulation of visceral functions such as cardiovascular, respiratory and digestive activities
CNS protected by:
- cranium
- vertebral column
additionally:
- CSF
- meninges
list cranial meninges:
superficial - deep:
- dura mater
- arachnoid mater
- pia mater
list spinal meninges:
superficial - deep:
- dura mater
- arachnoid mater
- pia mater
spinal cord: features
- connects CNS to PNS which isn’t innervated by cranial nerves
- adult spinal cord (40-50cm long)
- from medulla oblongata to 2/3 down vertebral column (L1/2 intervertebral disc) -> ending as tapering conus medullaris
- remaining nerves continue down vertebral column in cauda equina
spinal nerves: pairs
31 pairs:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
spinal nerves: emerges from
- vertebral column though intervertebral/ neural foramen btw adjacent vertebrae
spinal nerves: Bell-Magendie Law
- each spinal n formed by combo of nerve fibres (axons) from dorsal and ventral roots
spinal nerves: dorsal root
- posterior root
- only afferent (sensory) fibres
receptor- PNS- CNS
spinal nerves: ventral root
- anterior root
- only efferent (motor) fibres
CNS- PNS- effector
lamina of: dorsal/ posterior column
lamina I - VII
lamina of: lateral column
lamina VII
lamina of: ventral/ anterior column
lamina VIII, IX
function of: dorsal column
- pain
- temp
- touch
- proprioception
- kinesthesia
function of: lateral column
- sympathetic (thoracolumbar levels)
- parasympathetic (sacral levels)
function of: ventral column
- motor interneurons
- motor neurons
match division to dorsal, ventral and lateral column/ horns:
- dorsal: sensory
- lateral: autonomic
- ventral: motor
white matter of spinal cord are:
- longitudinal tracts btw brain and spinal cord
- or btw spinal cord segments
ascending tracts: from
aka sensory
- spinal cord -> brain
descending tracts: from
aka motor
- brain -> spinal cord
spinal cord: tracts features
- tracts originating on one side of the body generally cross over (decussate) and innervate the contralateral side of body
- some remain on ipsilateral side of body
