Post on 28-Nov-2015
description
The Nervous SystemTan Zhao Xun; Edwin Liang 10S78
2
Overview
Basic Neuroanatomy
Somatic Nervous System
Autonomic Nervous System
BASIC NEUROANATOMY
3
4
The Nervous System
Central Nervous System
Peripheral Nervous System
Brain: 12 pairs of cranial nerves*
Spinal cord: 31 pairs of spinal nerves
Peripheral nerves
*CN XI
5
Spinal Cord: General Features Location:
Upper 2/3 of vertebral canal until L1/L2
Enlargements: Cervical (C5-T1) Lumbar (L2-S2)
Spinal segments spinal nerves
Caudal end – conus medularis Cauda equina
(caudal continuation of spinal nerves) Filum terminale (extension of pia mater)
6
Spinal Cord: General Functions
SYSTEMIC level function
Highways to transmit information between brain and other parts of the body Sensory Motor Autonomic
LOCAL level function
Reflex arc
Modulation of information (e.g. pain)
7
Spinal vs. Vertebral Segments
Spinal segment ≠ Vertebral segment
Spinal segment
Region of the spinal cord to which is attached the anterior and posterior roots of the spinal nerve
Vertebral segment
Vertebra of vertebral column
8
Vertebral Segments
Click icon to add picture
7 Cervical 12 Thoracic 5 Lumbar 5 Sacral (fused) 4 Coccygeal (fused)
33 Vertebral segments
9
31 Spinal Segments
Click icon to add picture
8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal
3131 pairs of spinal nerves
10
PIA
ARACHNOID
DURA
* SUBARACHNOID SPACE
*
11
Spinal Cord: Basic Anatomy Meninges
1. Pia mater
2. Arachnoid
3. Dura mater
Cerebrospinal fluid (CSF)
1. Protection
2. Cushion spinal cord
3. Remove some metabolites from spinal cord * SUBARACHNOID SPACE
12
WHITE MATTER
GREY MATTER
13
Spinal Cord: Grey & White Matter
GREY matter:
Unmyelinated axons
Dorsal horn: sensory
Ventral horn: motor
Lateral horn: autonomic
WHITE matter:
Myelinated axons
Structurally columns
Functionally tracts
GREY MATTER
WHITE MATTER
14
Spinal Cord: Grey Matter
Based on cytoarchitectonics of the neurons (cell size, location, dendrites)
Dorsal horn, intermediate zone, ventral horn
10 laminae 6 in dorsal horn 3 in ventral horn 1 around central canal
15
Histology of the Nervous Systems
CNS PNS
NEURONS NEURONS
Oligodendrocytes Schwann cells
Astrocytes Satellite cells
Ependymal cells
Microglia
16
Synapses
1. Sensory2. Motor3. Autonomic
17
Sensory Neurons
Cell body in dorsal root ganglion (DRG) Central axonal process in dorsal roots spinal cord (dorsal horn) General sensory (skin, joints, muscles) Visceral sensory (viscera)
Dorsal root ganglion
Dorsal root
Primary afferent fibres (1o sensory neuron)
18
Motor Neurons
Ventral root
Upper / Lower motor neuron Synapse with skeletal muscle Neuromuscular junction
19
Autonomic Neurons
Pre-ganglionic neuron Begins at lateral horn; ends at white communicantes
Post-ganglionic neuron Begins at gray communicantes
Ventral root
20
Spinal Nerves: Functional Components
Motor Efferent
General Somatic Efferent: Skeletal muscles
General Visceral Efferent: Viscera, glands, smooth muscles
Sensory Afferent
General Somatic Afferent: Skin, tendons, muscles, joints etc.
General Visceral Afferent: Viscera
21
Question 1Nerve fibres that carry sensory impulses from skeletal muscles to the brain and spinal cord are called:
A. Somatic efferent fibresB. Visceral efferent fibresC. Visceral afferent fibresD. Somatic afferent fibresE. None of the above
22
Question 1Nerve fibres that carry sensory impulses from skeletal muscles to the brain and spinal cord are called:
A. Somatic efferent fibresB. Visceral efferent fibresC. Visceral afferent fibresD. Somatic afferent fibresE. None of the above
23
Question 2__________ is an inflammation of the brain coverings.
A. EncephalitisB. MeningitisC. PoliomyelitisD. Cerebral Palsy
24
Question 2__________ is an inflammation of the brain coverings.
A. EncephalitisB. MeningitisC. PoliomyelitisD. Cerebral Palsy
25
Question 3A spinal cord CSF sample is usually taken from the:
A. BrainB. Peripheral nervesC. Lumbar subarachnoid spaceD. Cervical subarachnoid space
26
Question 3A spinal cord CSF sample is usually taken from the:
A. BrainB. Peripheral nervesC. Lumbar subarachnoid spaceD. Cervical subarachnoid space
27
“Treasure the little things in life.”
SOMATIC NERVOUS SYSTEM
28
29
Reflex Arc: Features
Automatic, rapid response to a stimulus
Action is involuntary
Occurs without any involvement of thought or the brain
In humans, this action occurs through a neural pathway called the reflex arc
30
Reflex Arc: Types
1. Spinal
• Connections and processing occur in spinal cord
2. Cranial
• Occurs in the brain
3. Somatic
• Involuntary control of skeletal muscular system
4. Visceral
• Involuntary control of glands, smooth muscle and cardiac muscle
31
Reflex Arc: Components
COMPONENT FUNCTION1. Receptor Responds to a stimulus2. Afferent sensory neuron Carries impulse to CNS3. Integrating centre Integrates information in CNS (involves
synapse(s)) Monosynaptic: 1 synapse; rapid Polysynaptic: ≥2 synapses; slower and
complex
4. Efferent motor neuron Carries impulse to effector5. Effector Carries out action
32
Reflex Arc: Stretch Reflex
The Stretch reflex
Reciprocal innervation of agonist/antagonist muscle groups
33
Dermatomes and Myotomes
Click icon to add picture
Dermatomes
Areas of sensory innervation on the skin for 1 particular spinal root/spinal nerve
Myotomes
Muscles (motor innervation) that 1 particular spinal root supplies
34
Neuromuscular Junction (NMJ)
Synapse between a motor neuron and skeletal muscles
Motor unit: 1 motor neuron and all the muscle fibres it innervates
35
NMJ: Clinical Conditions
•Myasthenia gravisWEAK
•Hyperkalemia [K+]
•Hypokalemia [K+]
36
NMJ: Clinical Conditions
CAUSE Decrease in number of available receptors at muscle end plate Release of transmitter is normal
SYMPTOMS Weakness of muscles and myasthenic fatigue with repeated activity Muscles of the eyes are affected early Diplobia and ptosis Weakness may generalise subsequently
1. Myasthenia gravis
37
NMJ: Clinical Conditions
HYPOKALEMIA Hypokalemic Periodic Paralysis (HypoKPP) Muscle weakness felt with periods of normal muscle function Observed in patients with impaired calcium channels Accompanied with low serum potassium
HYPERKALEMIA High potassium levels block muscle repolarisation
2. Abnormal K+ Levels
38
Example: Brachial Plexus
MARMU
39
Example: Brachial Plexus
Major nerve network supplying upper limb
C5-T1 nerves are roots of brachial plexus Union of anterior rami of C5-C8, T1
Some important branches: Musculocutaneous nerve Axillary nerve Radial nerve Median nerve Ulnar nerve
40
Example: Brachial plexusClinical conditions
Injuries result in paralysis and anesthesia
Complete paralysis No movement detectable
Incomplete paralysis Not all muscles paralysed but movements are weak
Injuries to different parts have different consequences* Superior injury (C5, C6) Inferior injury (C8, T1)
41
Example: Brachial plexusClinical conditions
Injuries to superior parts (C5, C6) – Erb-Duchenne palsy
Due to excessive increase in angle between neck and shoulder
Can also occur in newborn from excessive stretching of neck during delivery
“Waiter’s tip position”: Limb hangs by side in medial rotation
42
Example: Brachial plexusClinical conditions
Injuries to inferior parts (C8, T1) – Klumpke paralysis
Upper limb is suddenly pulled superiorly
Newborn’s upper limb pulled excessively during delivery
Claw hand: short muscles of hand affected
43
Question 1A patient with severe kyphoscoliosis presents with increasing dyspnea consistent with a decrease in chest wall compliance. With contraction of the external intercostal muscles during inspiration, the Golgi tendon organ (GTO) provides the central nervous system information about which of the following?
A. The length of the muscle being movedB. The velocity of the muscle movementC. The blood flow to the muscle being movedD. The tension developed by the muscle being movedE. The change in joint angle produced by the movement
44
Question 1A patient with severe kyphoscoliosis presents with increasing dyspnea consistent with a decrease in chest wall compliance. With contraction of the external intercostal muscles during inspiration, the Golgi tendon organ (GTO) provides the central nervous system information about which of the following?
A. The length of the muscle being movedB. The velocity of the muscle movementC. The blood flow to the muscle being movedD. The tension developed by the muscle being movedE. The change in joint angle produced by the movement
45
Question 2A 32 y/o man sees his physician after collapsing suddenly without any other physical distress. Lab results demonstrate an elevated serum concentration of K+ and he is diagnosed with periodic hyperkalemic paralysis, a clinical condition in which a sudden increase in extracellular K+ concentration results in muscle weakness. Which of the following is most likely to cause muscle weakness as a result of increased extracellular K+ concentration?
A. Hyperpolarization of muscle cellsB. Inactivation of sodium channels in muscle cellsC. Increased release of neurotransmitters from α motorneurons
46
Question 2A 32 y/o man sees his physician after collapsing suddenly without any other physical distress. Lab results demonstrate an elevated serum concentration of K+ and he is diagnosed with periodic hyperkalemic paralysis, a clinical condition in which a sudden increase in extracellular K+ concentration results in muscle weakness. Which of the following is most likely to cause muscle weakness as a result of increased extracellular K+ concentration?
A. Hyperpolarization of muscle cellsB. Inactivation of sodium channels in muscle cellsC. Increased release of neurotransmitters from α motorneurons
47
“The harder the struggle, the more glorious the triumph.”
AUTONOMIC NERVOUS SYSTEM
48
49
ANS: Features
PRE-ganglionic neuron Begins at lateral horn; ends at white communicantes
POST-ganglionic neuron Begins at gray communicantes
Ventral root
50
ANS: Features
Nervous system supplying viscera / organs
ANS Supply:
1. Smooth muscles
2. Cardiac muscles
3. Glands
Autonomic neurons located in lateral horn
2 neurons to go from spinal cord to target tissue PRE- & POST-ganglionic neurons
51
ANS: Pre- & Post-ganglionic Neurons
PRE-ganglionic neuron
Cell body in CNS (brainstem/spinal cord – autonomic nuclei)
Nerve fibre or axon is myelinated (white)
POST-ganglionic neuron
Cell body in PNS (autonomic ganglia aka preganglionic synpase)
Nerve fibre or axon is NON-myelinated (grey)
Target organ/tissue (a.k.a. postganglionic synpase)
52
ANS: Features
PRE-ganglionic neuron Begins at lateral horn; ends at white communicantes
POST-ganglionic neuron Begins at gray communicantes
Ventral root
53
SYMPATHETIC PARASYMPATHETIC
T1
L2
54
Sympathetic NS
Fight or flight
More widespread
Parasympathetic NS
Rest or repose
More localised
55
Neurotransmitters of the ANS
Preganglionic synapse
Sympathetic: acetylcholine (ACh)
Parasympathetic: acetylcholine (ACh)
Postganglionic synapse
Sympathetic: noradrenaline (NA) – adrenergic nervers (EXCEPTION: sweat gland- ACh)
Parasympathetic: acetylcholine (ACh) – cholinergic nerves
56
Receptors for ANS Neurotransmitters
Acetylcholine receptors (AChR)
Nicotinic (nAChR)
Muscarinic (mAChR)
Adrenergic receptors (NA)
α1: most widespread (except heart) ; Excitation
α2: GIT ; Inhibition
β1: heart ; Excitation
β2: bronchi ; Inhibition
57
SYMPATHETIC Nervous System
THORACO-LUMBAR Outflow
PRE-ganglionic neurons In lateral horn of spinal cord
(T1-L2 level)
POST-ganglionic neurons Mainly in sympathetic
chain/trunk ganglia/paravertebral ganglia
Some in prevertebral ganglia (e.g. celiac plexus, superior mesenteric ganglia)
Adrenal medulla
58
SYMPATHETIC Nervous System
Splanchnic nerves
Preganglionic axons that do not synapse in the sympathetic trunk ganglia Thoracic: Greater, Lesser,
Least Lumbar Sacral Pelvic (only splanchnic
nerve that carries parasympathetic fibres; S2-S4)
59
PARASYMPATHETIC Nervous System
CRANIO-SACRAL Outflow
PRE-ganglionic neurons Brainstem nuclei (CNIII, VII, IX, X) Sacral parasympathetic nucleus
(lateral horn of spinal cord from S2-S4)
POST-ganglionic neurons Parasympathetic ganglia located
near/within organs it supplies
60
Nerve Plexuses
Click icon to add picture
Somatic Brachial plexus Lumbo-Sacral plexus
Visceral/Autonomic Cardiac plexus Pulmonary plexus Esophageal plexus
61
Autonomic Nerve Plexuses
Network of sympathetic and parasympathetic nerve fibres
Occasional ganglia interspersed
Transmit motor and sensory fibres to and from viscera
62
Autonomic Nerve Plexuses
Thoracic
Cardiac plexus
Pulmonary plexus
Esophageal plexus
Abdomino-pelvic
Celiac plexus
Superior mesenteric plexus
Inferior mesenteric plexus
Hypogastric plexus
63
Thoracic Autonomic Nerve Plexuses
Viscero-Motor (EFFERENT)E.g. Cardiac plexus
Sympathetic Preganglionic: Lateral horn of spinal cord Postganglionic: Cardiac ganglia
Parasympathetic Preganglionic: Vagus nerve (dorsal motor nuclei) Postganglionic: Cardiac ganglia
64
PREganglionic Sympathetic POSTganglionic Sympathetic PREganglionic Parasympathetic POSTganglionic Parasympathetic
Cardiac Plexus
65
Thoracic Autonomic Nerve Plexuses
Viscero-Sensory (AFFERENT)
1. VISCERAL PAIN
Pain originates from body’s viscera/organs
Manifestation: Widespread (difficult to localise) Referred pain (convergent inputs)*
Fibres travel mainly through sympathetic fibres Sensory (afferent) nerve fibres: follow sympathetic nerve fibres Sensory ganglion: dorsal root ganglia
66
Referred Pain
Click icon to add picture
Pain perceived at a site adjacent to or at a distance from the site of an injury’s origin
Pain arising in viscera may also be felt in the skin or other somatic tissues, supplied by somatic nerves arising from the same spinal segment
67
68
Thoracic Autonomic Nerve Plexuses
Viscero-Sensory (AFFERENT)
2. VISCERAL REFLEX
For local or higher visceral reflexes
Does not reach consciousness
Fibres travel mainly through parasympathetic nerve fibres
Sensory (afferent) nerve fibres: follow parasympathetic nerve fibres (CNIX, CNX)
Sensory ganglion: inferior ganglion of glossopharyngeal nerve and vagus nerve
69
Abdomino-Pelvic Autonomic Nerve Plexuses
Viscero-Motor (EFFERENT)
SYMPATHETIC Preganglionic:
Thoracic splanchnic nerves (Great, Lesser, Least) Lumbar splanchnic nerves
Postganglionic: Celiac ganglion Aortico-renal ganglion Adrenal medulla Superior mesenteric ganglion
70
Abdomino-Pelvic Autonomic Nerve Plexuses
Viscero-Motor (EFFERENT)
PARASYMPATHETIC Preganglionic:
Vagus nerve Pelvic splanchnic nerve
Postganglionic: Celiac ganglion Aortico-renal ganglion Adrenal medulla Superior mesenteric ganglion
71
Abdomino-Pelvic Autonomic Nerve Plexuses
Viscero-Sensory (AFFERENT)
Visceral Pain E.g. Appendicitis: referred pain to umbilical region
Visceral-reflex Receptors along digestive tract sensitive to stretch Control sphincters for movement of food
72
Abdomino-Pelvic Autonomic Nerve Plexuses
Viscero-Sensory (AFFERENT)
73
Question 1The cell bodies of preganglionic parasympathetic neurons are located in the:
A. Cervical and thoracic spinal cordB. Brain and lumbar spinal cordC. Thoracic and lumbar spinal cordD. Brain and sacral spinal cord
74
Question 1The cell bodies of preganglionic parasympathetic neurons are located in the:
A. Cervical and thoracic spinal cordB. Brain and lumbar spinal cordC. Thoracic and lumbar spinal cordD. Brain and sacral spinal cord
75
Question 2Norepinephrine is released from _______ nerves.
A. All autonomicB. ParasympatheticC. The vagusD. Sympathetic
76
Question 2Norepinephrine is released from _______ nerves.
A. All autonomicB. ParasympatheticC. The vagusD. Sympathetic
77
Question 3Sympathetic nerves arise from the __________ and __________ regions.
A. Cervical; LumbarB. Cranial; SacralC. Cranial; ThoracicD. Thoracic; Lumbar
78
Question 3Sympathetic nerves arise from the __________ and __________ regions.
A. Cervical; LumbarB. Cranial; SacralC. Cranial; ThoracicD. Thoracic; Lumbar
79
Question 4What kind of peripheral nerve fibre carries motor impulses outward to smooth muscles and glands of internal organs?
A. General somatic efferent fibresB. General visceral efferent fibresC. General somatic afferent fibresD. General visceral afferent fibres
80
Question 4What kind of peripheral nerve fibre carries motor impulses outward to smooth muscles and glands of internal organs?
A. General somatic efferent fibresB. General visceral efferent fibresC. General somatic afferent fibresD. General visceral afferent fibres
81
“Everything is good at the end;If things are not good yet, it’s not the end.”
82
SUMMARY
Basic Neuroanatomy
Somatic Nervous System
Autonomic Nervous System
CASE STUDIES
84
References
1. NUS YLLSoM Nervous System notes by Ng Yee Kong2. Physiology Fourth Edition Textbook by Linda S. Costanzo3. Physiology Fourth Edition Cases and Problems by Linda S. Costanzo4. http://ohsu2015.wikispaces.com/8.24.11+-+Peripheral+Nervous+System5. http://anatomyandart.com/blog/wp-content/uploads/2009/08/
brachial_plexus11.jpg6. http://fc02.deviantart.net/fs71/f/2011/150/8/9/the_brachial_plexus_by_ilex-
d3hlg39.png7. http://www.valiant.com/wp-content/uploads/2012/02/Megu1.jpg8. http://o.quizlet.com/i/XBgTcTr9YMcoleCQMT87ig_m.jpg9. http://www.scripps.org/encyclopedia/graphics/images/en/9196.jpg10. http://cdn.funcheap.com/wp-content/uploads/2011/07/candcads23.jpg11. http://cdn.funcheap.com/wp-content/uploads/2011/07/candcads24.jpg
FAITH; NOT FEAR.