This document provides information on the nervous system. It begins by outlining learning outcomes related to describing the central, peripheral, and autonomic nervous systems, understanding their functions, and explaining how a nervous impulse is transmitted and the physiology behind lesions. It then provides details on the structure and function of the spinal cord and brain, including the components and roles of the central and peripheral nervous systems. It describes how damage to different parts of the nervous system can result in paralysis and other effects, depending on the severity, location, and type of neurons involved.

1. Learning Outcomes
• To describe the major components of the Central,
Peripheral and Autonomic Nervous systems.
• To understand the functions of these components.
• To explain how a nervous impulse is transmitted.
• To explain the underlying physiology behind the
lesions/damage that occurs in the nervous system.

2. Spinal cord structure

3. Spinal cord has two main functions:
1). SC connects a large part of the peripheral nervous
system to the brain.
2) SC acts as a minor coordinating centre responsible for
some simple reflexes (e.g withdrawal reflex).
31 pairs of spinal nerves arise along the spinal cord

4. • Extension of brain stem
• Long slender cylinder of nerve tissue (~45 cm long, 2cm
diameter).
• Enclosed by a protective vertebral column (vertebrae).
• Paired spinal nerves emerge from spinal cord.
• Spinal nerves named according to region of vertebral
column from which they emerge.

6. Peripheral Nervous System
• 31 pairs of Spinal nerves
• 12 pairs of Cranial nerves
• Autonomic Nervous System

9. 8 pairs: Cranial Nerves
12 pairs: Thoracic Nerves
5 pairs: Lumbar Nerves
5 pairs: Sacral Nerves
1 Pair: Coccygeal Nerves

10. • During development, vertebral column grows ~25cm
longer than SC.
• Nerves pass down SC and exit at particular points from
the vertebral column.
• At the lower end of vertebral column is a thick bundle of
elongated nerve roots called Cauda Equina (‘horses tail’).
At this region Spinal Taps
can be taken (collection of CSF).
No SC, so no damage caused.

11. • A cross section of the SC shows it is composed of grey
matter in the centre surrounded by white matter.
Ventral horn
White matter
Grey matter
Dorsal horn

12. Grey Matter.
– resembles the letter H (butterfly)
– consists of mixture of multipolar neurone cell bodies
(colour)
– consists of 2 prominent projections:
• Posterior Dorsal Horn
• Anterior Ventral Horn

13. Dorsal Horn:
• Groups of afferent fibres carrying impulses from peripheral
sensory receptors enter through the dorsal root into here.
Ventral Horn:
• Nerve fibres exit from here through ventral roots to
skeletal muscles.
Dorsal and ventral roots are very short and
fuse to form the spinal nerves.

16. Poliomyelitis:
polio = grey matter
myelitis = inflammation of SC
• Polio virus enters through faeces contaminated water.
• Polio virus causes destruction of anterior ventral horn
motor neurones.
• Muscles atrophy due to wasting (astronauts)
• Death by paralysis of respiratory or cardiac muscle
• Salk and Sabin polio vaccines eliminated disease.

17. White Matter
- Composed of myelinated and unmyelinated nerve fibres.
- Divided into:
Posterior funiculi
Lateral funiculi
Anterior funiculi

18. Spinal Cord Segments

19. • Spinal tracts are bundles of axons grouped together into
columns that extend length of the spinal cord
• A spinal tract consist of neuronal axons that have a similar
destination and function
• Part of a multineurone pathway that connect the brain to the
rest of the body
• Each tract either:
- begins with a particular part of the brain
(Motor / descending tract)
- ends with a particular part of the brain
(Sensory /ascending tract)
• Tracts are named according to their origin and point of
termination.

21. The Brain

22. • The brain is organised into several different regions
dependent upon function, anatomy and development.
1). Brain stem:
- Midbrain
- Pons
- Medulla
2). Cerebellum:
3). Forebrain:
• Although specific activity is attributed to particular regions,
complex interplay between regions exists.

23. • A majority of the brain which we recognise is the
Cerebrum (outer wrinkly part).
• Deep folds divide each half of the Cerebrum into 4 major
lobes.
- Occipital lobes: process visual input
- Temporal lobes: process sound
- Parietal lobes: receive and process somesthetic
sensations (touch, pressure, heat,
cold, pain) and proprioception
(awareness of body position)
- Frontal lobes: 3 functions:
voluntary motor activity,
speaking ability, thought

24. Cerebral Hemispheres (Cerebrum).
• Largest part of the brain
• Account for about 80% of brain weight.
• Divided into 2 halves:
- Right cerebral hemisphere
- Left cerebral hemispheres.
• They are connected together by the Corpus Callosum.
• This is a thick band of neuronal axons transversing
between the 2 hemispheres.

25. • The entire surface of the cerebral hemispheres are
marked by elevated ridges of tissue called Gyri.
• These are separated by shallow grooves called sulci.
• The deepest of these grooves are called fissures.
• The median longitudinal fissure separates the cerebral
hemispheres from one another.
• The transverse fissure separates the cerebral
hemispheres from the cerebellum below it.

26. Parts of the Brain
• Cerebrum
• Thalamus
• Hypothalamus
• Cerebellum
• Midbrain
• Pons
• Medulla Oblongata

27. Cerebral lobes and their function
• Frontal: - voluntary motor activity
- speech
- thought
• Temporal: - process sound
• Occipital: - process visual input
• Parietal: - process somesthetic sensations (touch,
pressure, heat, cold
- proprioception; awareness of body position

28. www.smc.edu

29. The Brain
– Cerebral cortex: cognition, senses, movement
– Cerebellum: coordination of muscle contraction
– Thalamus: relay center
– Hypothalamus: homeostasis
– Limbic System: instincts, emotions
– Brain Stem: medulla controls breathing, blood
pressure, heart rate

31. Parts of the Brain
Cerebrum
Thalamus
Hypothalamus
Cerebellum
Midbrain
Pons
Medulla Oblongata
Tortora, G. J. and Grabowski, S.
(2000) Principles of Anatomy and Physiology

33. The Cerebrum
www.smc.edu

34. www.smc.edu

37. Spinal cord has two main functions:
1). SC connects a large part of the peripheral nervous
system to the brain.
2) SC acts as a minor coordinating centre responsible for
some simple reflexes (e.g withdrawal reflex).
• 31 pairs of spinal nerves arise along the spinal cord
The Spinal Cord

38. Peripheral Nervous System
• 31 pairs of Spinal nerves
– Join together to form Plexuses
• 12 pairs of Cranial nerves
• Autonomic Nervous System

39. Any localised damage to spinal cord or spinal roots will
attribute to some form of functional loss.
- Paralysis: (loss of motor function)
- Parasthesias: (loss of senses)
The effects of disease or injury upon the CNS and
periphery depend on the:
- severity of the damage
- type of neurones involved
- position of neurones involved
Lesions/Damage to the Nervous System

40. • Normal muscle function requires intact connections along
motor pathway.
• Chain of nerve cells that runs from the brain through the
spinal cord out to the muscle is called the motor pathway.
• Damage at any point reduces brain's ability to control
muscle's movements.
• Reduced efficiency causes weakness (paresis).

41. • Complete loss of communication prevents any willed
movement.
• Lack of control is called paralysis.
• Paralysis may affect an individual muscle, but usually
affects an entire body region.
• Distribution of weakness an important clue to location of
the nerve damage that is causing the paralysis.
• Words describing the distribution of paralysis use the
suffix "-plegia," from the Greek word for "stroke.“

42. The types of paralysis are classified by region:
Monoplegia: affecting only one limb
Diplegia: affecting the same body region on
both sides of the body (both arms, for
example, or both sides of the face)
Hemiplegia: affecting one side of the body
Paraplegia: affecting both legs and the trunk
Quadriplegia: affecting all four limbs and the trunk.

43. • The nerve damage that causes paralysis may be in the:
- brain or spinal cord (CNS)
- nerves outside the spinal cord (PNS).
• The most common causes of damage to the brain are:
- Stroke
- Tumour
- Trauma (caused by a fall or a blow)
- Multiple sclerosis (destruction of Myelin
sheath))
- Cerebral palsy (defect or injury to the brain that
occurs at or shortly after birth)
- Metabolic disorder (interferes with body's ability
to maintain itself).

44. • Damage to spinal cord is most often caused by trauma,
(fall/car crash). Other conditions that may damage
nerves within or immediately adjacent to spine include:
- Tumour
- Herniated disk (also called a ruptured or slipped
disk)
- Spondylosis (a disease that causes stiffness in
the joints of the spine)
- Rheumatoid arthritis of the spine
- Neurodegenerative disease (a disease that
damages nerve cells)
- Multiple sclerosis.

45. • Paralysis originating in the brain may sometimes be
flaccid, that is, the affected muscles may be loose,
weak, flabby, and without normal reflexes.
• More frequently it is spastic, that is, the affected
muscles are rigid and the reflexes accentuated.
• Paralysis originating in a motor nerve (UMN) of the
spinal cord is always spastic
• Paralysis originating in peripheral nerves (LMN) is
always flaccid.

46. Cerebrovascular Accident (Stroke)
• CVAs are: bleeds into the brain
obstruction of blood supply to brain
• CVAs often affect Motor cortex and its major pathways.
• These tracts cross in medulla therefore:
- left hemiplegia (stroke on right side of brain)
- right hemiplegia (stroke on left side of brain)
• Small bleeds close to brain surface may result in weakness on one
side (hemiparesis)
- good chance of recovery
• Larger/deeper bleeds may cause profound paralysis
- may result in permanent damage

47. Pupillary Reflex
• Clinical test for brain stem function
• Shine bright light into patient’s eye
• Normal response: pupils constrict in response to light
stimulus
• Reflex via autonomic nervous system
• Sensory input of bright light- to brain via optic nerve (II)
– parasympathetic impulses out via oculomotor nerve
(III) – circular muscles of eye constrict
• Pupil observation important when considering head
injury care

48. Plantar (sole) reflex
• Tests integrity of spinal cord from L4-S2
• Determines functionality of corticospinal tracts
• Normal response is a downward flexion (curling) of
toes
• If corticospinal tract damaged, normal plantar’s reflex
replaced by Babinski’s sign
• Toes fan backwards
Normal Abnormal