the nervous system

• The human nervous system is composed of neurones or nerve cells
• the two parts of the human nervous system are :

  Central Nervous System

  Peripheral Nervous System
• The peripheral nervous system is divided into cranial nerves and spinal nerves that connect the central nervous system to all parts of the body
• The Central Nervous System is made up of two parts, the brain and the spinal cord.
• The spinal cord is responsible for carrying impulses to and from the brain, it also controls spinal reflexes.
• The brain is further divided into three parts, the cerebrum, the cerebellum and the medulla oblongata.
• Cerebrum - Controls conscious thought, problem solving; memory,interpret senses, intelligence, learning, speech; coordinatesvoluntary actions
• Cerebellum Controls balance and posture; coordinates muscle movement
• Medulla oblongata - Controls involuntary actions eg, heart rate, breathing rate, blood pressure; peristalsis
• Voluntary Actions are activities controlled by your conscious thought.
• Involuntary Actions are actions that are not controlled by your conscious thoughts
• A reflex is a sudden response to a stimulus. A reflex action is fast and automatic.
• Receptor- These are specialized cells that can detect any change in the environment (stimuli)
• Sensory neurone- This is a neurone that transmits impulses from the receptor to the central nervous system (CNS).
• Motor neurone- This neurone is responsible for carrying impulses away from the central nervous system to effectors
• Relay neurone- This neurone is found in the central nervous system. It is responsible for carrying impulses between the sensory and motor neurone
• Effector- This is a muscle or a gland that brings about a response.
• A reflex arc is the pathway between a receptor and an effector.
• Simple reflex action -

  Stimulus --> receptors ---> sensory neurone ---> relay neurone (cns) --> motor neurone --> effector --> response