nervous system

• Nervous System

  • Bears a major responsibility for maintaining body homeostasis
• Nervous System

  • Monitors, integrates, & responds to information in the environment
• Anatomical Divisions of the Nervous System

  • Central nervous system (brain & spinal cord)
  • Peripheral nervous system (cranial & spinal nerves)

  
• Functional Divisions of the Nervous System

  • Sensory (afferent) division - conveys impulses to the CNS
  • Motor (efferent) division - conveys impulses from the CNS

  
• Motor Division

  • Somatic (voluntary) system - serves skeletal muscles
  • Autonomic (involuntary) system - innervates smooth & cardiac muscle & glands
• Components of the CNS

  • The brain
  • Spinal cord
• The Brain

  • Provides for voluntary movements
  • Interpretation
  • Integration of sensation
  • Consciousness
  • Cognitive function
• Regions of the Adult Brain

  • Cerebral hemispheres (left & right)
  • Diencephalon
  • Brain stem
  • Cerebellum

  
• Ventricles

  Brain contains 4 ventricles filled with cerebrospinal fluid
• Cerebral Lobes

  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe
• Lateralization of Cortical Function

  • Left hemisphere is dominant and specialized for language & mathematical skills
  • Right hemisphere is more concerned with visual-spatial skills & creative endeavors
• Diencephalon


  Encloses the third ventricle, includes: the thalamus, hypothalamus, & epithalamus
• Thalamus


  Major relay station for sensory impulses, motor inputs, and impulses travelling to association cortices
• Hypothalamus

  • Important autonomic nervous system control center
  • Pivotal part of the limbic system
  • Maintains water balance & regulates thirst, eating behavior, gastro-intestinal activity, body temperature, & the activity of the anterior pituitary gland
• Epithalamus


  Includes the pineal gland which secretes the hormone melatonin
• Brainstem Structures

  • Midbrain
  • Pons
  • Medulla oblongata
• Midbrain

  • Contains the corpora quadrigemina (visual & auditory reflex centers)
  • Contains the red nucleus (subcortical motor centers)
  • Contains the substantia nigra
• Pons


  • Mainly a conduction area
  • Its nuclei contribute to the regulation of respiration & cranial nerves V–VII
• Medulla Oblongata


  • The pyramids form the ventral face and the fibers cross over before entering the spinal cord
  • Important nuclei regulate respiratory rhythm, heart rate, & blood pressure & serve cranial nerves VIII–XII
  • Contains the olivary nuclei & cough, sneezing, swallowing, & vomiting centers
• Cerebellum


  • Coordinates motor activity so that smooth, well-timed movements occur
• Brain Protection

  The brain (and the spinal cord) is protected by bone, meninges, cerebrospinal fluid, & the blood-brain barrier
• Meninges

  • Dura mater
  • Arachnoid mater
  • Pia mater
• Cerebrospinal Fluid (CSF)


  Formed by the choroid plexuses from blood plasma, circulates through the ventricles & into the subarachnoid space, returns to the dural venous sinuses via the arachnoid villi, supports & cushions the brain & cord & helps to nourish them
• Blood-Brain Barrier (BBB)


  Reflects the relative impermeability of the epithelium of capillaries of the brain, allows water, respiratory gases, essential nutrients, & fat-soluble molecules to enter the neural tissue but prevents entry of other, water-soluble, potentially harmful substances
• Spinal Cord

  • A 2-way impulse conduction pathway
  • A reflex center
  • Resides within the vertebral column & protected by meninges & cerebrospinal fluid
  • Extends from the foramen magnum to the end of the first lumbar (L₁) vertebra
  • 31 pairs of spinal nerve roots issue from the cord
• Spinal Cord Cross-Section

  Central gray matter is H-shaped, ventral horns contain somatic motor neurons, lateral horns contain visceral (autonomic) motor neurons, dorsal horns contain interneurons
• Components of the PNS

  • Sensory receptors
  • Nerves conducting impulses to & from the CNS
  • Their associated ganglia & motor endings

  
• Cranial Nerves


  12 pairs originate from the brain, emerge through the skull to innervate the head & neck, only the vagus nerves extend into the thoracic & abdominal cavities
• Spinal Nerves

  31 pairs, all mixed nerves, numbered successively according to the region of the spinal cord from which they emerge, formed by the union of dorsal & ventral roots, short, confined to the intervertebral foramina
• Cervical Plexus


  Innervates the muscles & skin of the neck & shoulder, phrenic nerve serves the diaphragm
• Brachial Plexus


  Serves the shoulder, some thorax muscles, & the upper limbs, arises primarily from C5–T1, has roots, trunks, divisions, & cords, main nerves are the axillary, musculocutaneous, median, radial, & ulnar nerves
• Lumbar Plexus


  Provides the motor supply to the anterior & medial thigh muscles & the cutaneous (sensory) supply to the anterior thigh & part of the leg, chief nerves are the femoral & obturator
• Sacral Plexus

  Supplies the posterior muscles & skin of the lower limb, principal nerve is the large sciatic nerve composed of the tibial & common fibular nerves
• Olfactory Nerve (CN I)


  Concerned with the sense of smell
• Optic Nerve (CN II)


  Transmits visual impulses from the retina to the thalamus
• Oculomotor Nerve (CN III)

  Emerges from the midbrain & serves 4 extrinsic eyeball muscles, the levator palpebrae superioris of the eyelid, & the intrinsic ciliary muscle of the eye & constrictor fibers of the iris
• Trochlear Nerve (CN IV)


  Emerges from the dorsal midbrain & carries motor & proprioceptor impulses to & from superior oblique muscles of the eyeballs
• Trigeminal Nerve (CN V)


  Emerges from the lateral pons as the major general sensory nerves of the face and has three sensory divisions: ophthalmic, maxillary, & mandibular; the mandibular branch also contains motor fibers that innervate the chewing muscles
• Olfactory nerves (I)


  Concerned with the sense of smell
• Optic nerves (II)


  Transmit visual impulses from the retina to the thalamus