Constituent Parts of the Nervous System

• An animal's response to a stimulus is coordinated by its CNS
• The CNS is made up of the brain and the spinal cord
• The CNS gathers information about the environment and also resposnds to the changes
• Receptors detect a stimulus and sends impulses along sensory neurones to the CNS
• The CNS gathers the information and sends impulses along motor neurones to the effectors
• The effectors bring out a response

The sequence of the CNS repsonding to a change is stimulus is as follows;

1) Stimulus

2) Receptor

3) Sensory Neuron

4) Central Nervous System

5) Motor Neuron

6) Effector

7) Response

• The Peripheral Nervous System (PNS) is made up of motor and sensory neurons
• The Motor and Sensory Neurons that carry impulses from the receptors to the CNS, as well as impulses from the CNS to the effectors
• The PNS can be broken down into two systems; the autonomic nervous system and the somatic nervous system

• The Autonomic Nervous System regulates involuntary actions such as breathing and digestion.
• The Autonomic Nervous System is split into two parts; the sympathetic and parasympathetic systems. 
• The Sympathetic nervous system activates the "flight or fight" response when exposed to stressful situations such as seeing a predator. 
• The Parasympathetic nervous system activates a "rest and digest" or "feed and breed" response after the stressful events have happened, this helps to replenish the system and conserve energy. 

• The somatic nervous system keeps the body coordinated and the body proficient at keeping the body functioning, through both voluntary actions and reflexes.
• The somatic nervous system controls sytems in areas such as the skin, bones, joints and skeletal muscles. 
• Afferent fibers, or nerves that receive information from external stimuli, carry sensory information through pathways that connect the skin and skeletal muscles to the CNS for processing. (Boundless, undated)
• The information is then sent back via efferent nerves, or nerves that carry instructions from the CNS, back through the somatic system. (Boundless, undated)
• Afferent - Leaning toward the CNS
  Efferent - Leaning away from the CNS
• The somatic system also provides us with reflexes, which are automatic and do not require input or integration from the brain to perform. (Boundless, undated)

• Both the central and peripheral nervous systems contain billions of neurons. 
• Neurons connect with each other and form neurological circuits. Information travels along these circuits by electrical signals
• There are two types of neurons - sensory and motor
• Sensory neurons - they carry information from the body to the spinal cord or brain stem, they are then passed to the cerebellum and the cerebrum for them to be read and interpreted. Sensory information includes pain, touch, taste, temperature, position, balance, hearing, vision and smell.
• Motor neurons - they carry responses to the sensory information from the spinal cord and brain to the rest of the body. Inside the spinal cord, the axons of motor neurons form bundles called tracts, the tracts transmit this information to motor peripheral nerves in the limb muscles. Motor neurons are important for voluntary movements and muscle control.

• Efferent pathways carry signals away from the CNS. They are signals that your brain sends to tell your body to carry out an action such as blinking. 
• Afferent signals come from stimuli outside the body and tell your brain what they are sensing, for example temperature. Afferent neurons take stimuli to the brain where the signal is processed. The brain coordinates a response by efferent signals back to the rest of the body.
• A way to remember afferent vs. efferent neurons is: Afferent Arrives, Efferent Exits.

• Unconscious - When a stimulus influences behaviours and/or neural activity while the animal is unaware of it
• Unconscious perception involves processing sensory inputs that have not been selected for conscious perception.
• Unconsciously, the brain processes all of the stimuli that animals come into contact with, not just those that we consciously deal with. The brain recieves the signals and interprets them in ways that control how we respond to our surrounding environment
• Conscious - When a stimulus influences behaviours and/or neural activity and the animal is aware of it happening
• An example of conscious perception is when a fly lands on a horses leg and starts tickling their leg they may consciously move their leg to try remove the fly. It can also include moving ears and in humns, moving toes or fingers up or down.