nervous system

• The nervous system is divided into 2 main parts

  1. The central nervous system
  2. The peripheral nervous system
• The CNS consists of brain & spinal cord.

  • The brain is enclosed within the cranium
  • The spinal cord lies within the vertebral column.
• Function of CNS to integrate and coordinate incoming and outgoing neural signals for the higher mental functions such as thinking and learning.
• Layers of Meninges:

  • Protection: Surround and protect the brain from outside to inside.
  • Three Layers:

  1. Dura Mater: Toughest layer.
  2. Arachnoid Mater
  3. Pia Mater
• Subarachnoid Space:

  • Definition: Space between the arachnoid and pia mater.
  • Content: Contains cerebrospinal fluid (CSF).
• Fill in the blank

  A) Aponeurosis

  B) Periosteum

  C) Bone

  D) dura mater

  E) Arachnoid

  F) Pia mater

  
• Fill in the blank

  A) dura mater

  B) arachnoid

  C) pia mater

  D) subarachnoid space

  
• The CNS is composed of

  1. Large numbers of excitable nerve cells (neurons) and their processes.
  2. Neuroglia – is specialized tissue which supports the neurons.
• The interior of the CNS is organized into gray & white matter

  • Gray matter: consists of bodies of neurons & the proximal portion of their processes embedded in neuroglia.
  • White matter: consists of nerve fibers embedded in neuroglia. It has a white colour due to the presence of lipid material in the myelin sheaths of many nerve fibers.
• PNS is composed of cranial nerves, spinal nerves and their associated ganglions.
• A peripheral nerve consists of bundles of nerve fibers
• The PNS conveys neural (sensory) impulses to the CNS from

  1. The sense organs (e.g. eye, nose & ears = special sense)
  2. The sensory receptors in various parts of the body (e.g. skin, muscles & joints).
• The PNS also conveys neural impulses from the CNS to the muscles & glands (motor impulses)
• a bundle of nerve fibers or axons in the PNS is called a nerve.
• Ganglion is a collection of nerve cells outside the CNS (dorsal root ganglion)
• a nucleus is a collection of nerve cells or neurons located within the central nervous system (CNS).
• Cranial Nerves:

  • 12 pairs
  • Exit: Through foramens in the skull.
  • Innervation: Muscles, joints, and skin of the head.
• Spinal Nerves:

  • 31 pairs
  • Exit: Through intervertebral foramina in the vertebral column.
  • Innervation: Muscles, joints, and skin of the trunk and limbs.
• Somatic component is concerned with innervation of striated muscles, tendons, joints and skin.
• Autonomic component is concerned with the innervation of involuntary structures such as heart, smooth muscle and glands
• Spinal Nerves - 31 pairs

  1. 8 pairs of cervical nerves (C1 to C8)
  2. 12 pairs of thoracic nerves (T1 to T12)
  3. 5 pairs of lumbar nerves (L1 to L5)
  4. 5 pairs of sacral nerves (S1 to S5)
  5. 1 pair of coccygeal nerves (C1)
• CN I - Olfactory

  • Sense of smell (olfaction).
• CN II - Optic:

  • Sense of sight (vision).
• CN III - Oculomotor:

  • Supplies most of the extraocular muscles.
• CN IV - Trochlear:

  • Function: Supplies one extraocular muscle.
• CN V - Trigeminal:

  • Provides sensory innervation to the head and face.
• CN VI - Abducent:

  • Supplies an extraocular muscle.
• CN VII - Facial:

  • Supplies muscles of facial expression and salivary glands.
• CN VIII - Vestibulocochlear:

  • Sense of hearing and balance.
• CN IX - Glossopharyngeal:

  • Innervates the tongue, pharynx, and a pharyngeal muscle.
• CN X - Vagus:

  • Provides motor supply to the gut, heart, respiratory tract, and abdominal viscera.
• CN XI - Accessory:

  • Provides motor innervation to muscles of the palate, pharynx, larynx, and neck.
• CN XII - Hypoglossal:

  • Provides motor supply to muscles of the tongue.
• In both the somatic and autonomic divisions of the nervous system, the functional unit is a "reflex arc." A reflex arc is a neural pathway that controls a reflex action. It typically involves three main components:

  1. Afferent or sensory component
  2. An intercalated or interneurone
  3. Efferent or motor component
• Fill in the blank

  A) receptor

  B) dorsal root ganglion

  C) motor

  D) sensory

  
• Typical Spinal Nerve (2 roots)

  1. Ventral Root:

  • Efferent from motor neurons in the ventral (anterior) horn of the spinal cord.

  1. Dorsal Root:

  • Sensory or afferent fibers from sensory neurons in the dorsal root ganglion.
• The dorsal & ventral roots unite to form a spinal nerve, which divides into two branches – a dorsal ramus & ventral ramus
• The autonomic nervous system (ANS) is a division of the peripheral nervous system that influences the function of internal organs.
• The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.
• Within the brain, the autonomic nervous system is regulated by the hypothalamus.