Lecture 21 + 22 - Nervous System Flashcards
how is the nervous system organised ?
sensory input feeds into afferent neurons, which in turn feeds into the CNS (brain and spinal chord)
the CNS then signals the Efferent neruons
this is either the somatic motor (controlled) system or the Autonomic nervous system (involuntary responses)
the autonomic nervous system divided into the Sympathetic - fight or flight and Para Sympathetic - rest and digest Nervous systems
there is also the contentious enteric nervous system
these affect the target tissues
what are the differing structures of neurons ?
how is transport achieved ?
Multipolar - Cell body with many dendrites, then a long axon and a termianl
pseudounipolar - one dendrite/axon with a ganglion connected to the center via a axon
bipolar - long dendrite and a short axon with a cell body in the center
unipolar - cell body to terminal sdirect - dendrites come from the sides of the cell
Anterograde and retrograde vesicles use microtubule
‘shuttle’ system to move from soma to synapse and back
what are the effects of mylenation ?
- In PNS–Schwann cells myelinate segments of axon, leaving nodes of ranvier
- Saltatory conduction –Action potential ‘jumps’ from node to node
- In CNS–Oligodendrocytes myelinate multiple neurones
- Effects of myelination:
- Increased resistance
- Reduced capacitance
what is the peripheral nerve structure ?
Divisions
Epineurium - Around entire nerve
Perineurium - Around nerve fasicles
Endoneurium - around individual axons
overview of the CNS ?
5 sections ….
Cerebrum - Interprets information and involved in making conscious decisions
Cerebellum - Involved in co-ordination, balance and motor learning
Hypothalamus - and the pituitary - Interface between nervous and endocrine systems, important role in homeostasis
Brain Stem - important autonomic functions
Spinal Chord - Gives of spinal nerves
What is the structure of a spinal chord ?
be able to label, reconginse sections from pictures ect
Forms a butterfly shape of gray matter - with dorsal, lateral and ventral horns
and a surrounding ring of white matter
it has a central canal and a grey commisure link the two peripheral regions
afferent sensory information enters through the dorsal root ganglion and efferent signals to muscles and glands via the ventral root
Somatic Sensory Nuclei - Top of Dorsal Horn
Visceral Sensory Nuclei - beneath somatic, still in dorsal horn
Efferent Autonomic Nuclei - lateral horn
Somatic Motor Nuclei - ventral horn
Dorsal root receives only sensory neurons
Ventral root only sends motor neurons
the spinal nerve is mixed !
What is a schwann cell
mylenating cell of the PNS - schwann cell wraps round one neurone by swirling round it slowly , until it is completely wrapped
myelin sheeth is formed
what is an oligodendrocyte ?
mylenating cell of the CNS many processes from the cell body will wrap around many neurons
what is an astrocyte ?
what is a microglia ?
astrocyte - Formation of the blood brain barrier , metabolic and physical support for neurons, neurotransmitter regulation
microglia - Phagocytes of the CNS
what is the anatomny of the ANS ( from ICPP as well)
Para sympathetic -MYLENATED long Pre ganglionic Neurons - Ganglion in innervated tissue - Short UNMYLENATED neuron to taget tissue
Medullary and Sacral Regions?, Cranial sort of but not really
stimulates galnds ect to slow heart , affect GI tract and Erection, bronchoconstriciton
uses ach and NachR in the pre ganglion and ach and m(1-5)AchR in the post ganglion
Sympathetic - Short MYLENATED pre ganglionic Neuron in the paravertabral chain followed by a LONG UNMYLENATED to the Target
from throacic and lumbar regions - T1-L2
Speed up heart rate, vasodilation, adrenaline release ect
uses ach - NachR in pre and mainly Noradrenaline to Alpha, 1,2 and Beta 1,2,3 adrenoceptors (GPCR) in post ganglion
What is the anatomy of the SNS ?
• Thoraco-lumbaroutflow (T1-L2)
- Sympathetic(paravertebral) chain–Chain of sympathetic ganglia running either side of spinal column
- Sympathetic pre-ganglionics generally do one of four things:
- Synapse at level of entry–E.g. To innervate skin at that level
- Ascend the chain–Typically to innervate the head and neck
- Descend the chain–To innervate targets at L3 and below
- Traverse the chain and synapse in pre-aortic ganglion – E.g. To innervate gut
what is multiple sclerosis ?
Remitting and relapsing disease
• Caused by autoimmune degradation of myelin
Symptoms:
Fatigue
Vision problems (diplopia)
Slurred speech (dysarthria)
Numbness and tingling sensations (paraesthesia)
Mobility issues (muscle spasms)
Symptoms caused by loss of conduction velocity
how do autonomics communicate with the spinal nerve ?
draw it and check from lec 22
what is the purpuse of the chain in the sympathetic system?
a singal can enter/ be sent , and it can synapse at entry level , decend or ascend the chain to singal where it needs to
