300113 Intro to Nervous System

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


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


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


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


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


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


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


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


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


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

68



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


Viscero-Motor (EFFERENT)

PARASYMPATHETIC Preganglionic:

Vagus nerve Pelvic splanchnic nerve

Postganglionic: Celiac ganglion Aortico-renal ganglion Adrenal medulla Superior mesenteric ganglion

71



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



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.

300113 Intro to Nervous System

Documents

Transcript of 300113 Intro to Nervous System