Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, Neuroscience (NEU) module.
learning objectives:
LO1: Recall the gross organisation of the human central and peripheral nervous systems
LO2: Illustrate the structure and functions of the spinal and cranial nerves
...
Overview of the organisation of the nervous system
- the nervous system is the control centre of sensation, movement, emotion => maintain homeostasis
=> 2 types of movement: voluntary/ involuntary (circulation, respiration, digestion)
- structural division:
Central nervous system (CNS): integrates, processes &
=> brain coordinates sensory input
and motor commands
=> spinal cord
Peripheral nervous system (PNS):
=> cranial nerves
=> spinal nerves
=> sympathetic trunk
ascending descending
(from receptors to CNS) afferent => splanchnic nerves efferent (from CNS to peripheral effectors)
connects w/ connects w/
Sensory Motor
external world internal world
also has
Somatic Autonomic visceral
Somatic sensory Visceral sensory sensation
(voluntary) (involuntary)
receptors receptors (glands)
skeletal muscle
touch, temp, balance... blood O2, ph, pressure...
Parasympathetic Sympathetic
- Rq: autonomic system sometimes not considered
smooth muscle - cardiac muscle - glands
“motor” because has no motoneurons (like somatic) smooth
skeletal
muscle
muscles
of blood vessels
(o Skeletal
serving
- receptors = sensory structures detecting change in the internal (visceral) or external (somatic) env.
- effectors = target organs whose activities change in response to neural commands
- human brain is capable of higher cognitive functions (reasoning, language, self-consciousness...)
Peripheral nervous system (PNS) each emerging from
- 12 pairs of cranial nerves: I to XII corresponding segment
- 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
- ganglion = group of neuronal cell bodies in the PNS
- plexus = network of intersecting nerves or fibres (redistribute spinal nerves into peripheral nerves)
, - nerve = collection of neural fibres (neurons) organised in fascicles => motor, sensory, mixed
(all spinal nerves are mixed)
- cranial nerves are numbered cranial to caudal (= posterior part body)
=> I & II emerge from cerebrum (the rest from pons in brain stem)
↳
=> carry info to & from the head and neck (BUT vagus nerve (X) reaches lungs, heart, stomach)
=> cranial nerves III, VII, IX, X also carry parasympathetic outflow (autonomic)
Function: - sensation
smell
eye movement - movement
vision
-
face sensation, chewing eye movement - autonomic
facial expression, taste horizontal eye movement
optic chiasm: where
1) spinal nerves originate from spinal cord w/ 2 roots optic nerves cross
=> ventral (anterior): motor fibres from the spinal cord to muscle fibres
=> cell bodies motoneurons in ventral horn// cell bodies autonomic neurons in lateral horn
=> dorsal (posterior): sensory fibres from peripheral receptors to spinal cord
=> cell bodies in the dorsal root ganglion (pseudounipolar neurons)
2) the 2 roots join & form the spinal nerve
=> leave the vertebral column through intervertebral foramen
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