Week 14 : Nervous System



  • A network of billions of nerve cells linked together in a highly organized fashion to form the rapid control center of the body.
  • Functions include: (Integrating center for homeostasis, movement, and almost all other body functions. / The mysterious source of those traits that we think of as setting humans apart from animals.)

Basic Functions of the Nervous System:

  • Sensation – Monitors changes/events occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are receptors.
  • Integration – The parallel processing and interpretation of sensory information to determine the appropriate response
  • Reaction – (Motor output. – The activation of muscles or glands (typically via the release of neurotransmitters (NTs))


NeuronsFunctional, signal conducting cells

Neuroglia – Supporting cells

Three Main types of Nerve cells:

  1. Sensory Neurons – Carries impulses from receptors e.g pain receptors in skin to the CNS( brain or spinal  cord).
  2. Relay Neurons – Carries impulses from sensory nerves to motor nerves.
  3. Motor Neuron – Carries impulses from CNS to effector e.g. muscle to bring about movement or gland to bring about secretion of hormone e.g ADH


Divisions of the Nervous System

  • Central Nervous System – (The brain + the spinal cordàThe center of integration and control)
  • Peripheral Nervous System – The nervous system outside of the brain and spinal cord. Consists of: 31 Spinal nerves – Carry info to and from the spinal cord; 12 Cranial nerves – Carry info to and from the brain.


The Central Nervous System

  • The Central Nervous System (CNS) is composed of the brain and spinal cord. The CNS is surrounded by bone-skull and vertebrae.
  • Thebrain is composed of three parts: the cerebrum (seat of consciousness), the cerebellum, and the medulla oblongata (these latter two are “part of the unconscious brain”).
  • The medulla oblongata is closest to the spinal cord, and is involved with the regulation of heartbeat, breathing, vasoconstriction (blood pressure), and reflex centers for vomiting, coughing, sneezing, swallowing, and hiccuping.
  • The cerebellum is the second largest part of the brain, after the cerebrum. It functions for muscle coordination and maintains normal muscle tone and posture. The cerebellum coordinates balance.
  • The cerebrum governs intelligence and reasoning, learning and memory. While the cause of memory is not yet definitely known, studies on slugs indicate learning is accompanied by a synapse decrease. Within the cell, learning involves change in gene regulation and increased ability to secrete transmitters.


Spinal Cord:

  • The spinal cord runs along the dorsal side of the body and links the brain to the rest of the body. The spinal cord is also involved inreflexes that do not immediately involve the brain.




Parts of the Brain and their Functions:

 Cerebral Cortex

*Occipital lobe – receives and processes visual information

*Parietal lobe – sensory projection and association areas, visual/ spatial abilities.

*Frontal lobe – goal-directed behavior, concentration, emotional control and temperament, motor projection and association areas, coordinates messages from other lobes, complex problem solving, involved in many aspects of personality.

*Temporal lobe – smell, hearing, balance and equilibrium, emotion and motivation, language comprehension, complex visual processing.


Central Core

*Medulla – regulates respiration, heart rate, blood pressure.

*Pons – regulates sleep-wake cycles.

*Cerebellum – regulates reflexes and balance, coordinates movement.

*Thalamus – major sensory relay center, regulates higher brain centers and peripheral nervous system.

*Hypothalamus – emotion and motivation, stress reactions.



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