1. The Nervous System

2.  The function of the nervous system is to allow the animal to quickly detect, communicate and co- ordinate information about its external and internal environment.  The two major parts of our nervous system are the central nervous system (CNS) and peripheral nervous system (PNS).  The CNS is made of the brain and spinal cord.  The cranial nerves, spinal nerves and ganglia make up the PNS.  The cranial nerves connect to the brain.  The cranial and spinal nerves contain the axons (fibres) of sensory and motor nerve cells.  Nerve cells are also known as neurons.

3. Sensory Neurons  Sensory neurons carry electrical signals (impulses) from receptors or sense organs to the CNS.  Sensory neurons are also called afferent neurons.  The cell body of sensory neurons is outside the CNS in ganglia. Motor Neurons  Motor neurons carry impulses from the CNS to effector organs.  Motor neurons are also called efferent neurons.  The cell bodies of motor neurons are inside the CNS.

5.  A synapse is a specialised junction between a neuron and its target cell.

7.  Cerebrum: centre for sensory and motor control, language, memory, intelligence, and consciousness.  Cerebellum: muscle co-ordination, movement and balance.  Medulla Oblongata: controls breathing and heart rate.  Hypothalamus: osmoregulation and temperature control.  Pituitary Gland: secretes a wide variety of hormones – a major endocrine gland.

8.  A reflex action is a very fast unconscious response to an unexpected and potentially dangerous stimulus.  Examples of reflex action: knee jerk, eye blink, pupil size alteration, closure of the glottis on swallowing.  A reflex arc is a specific nerve pathway involved in a fast, unconscious response to an unexpected stimulus.  E.g. Spinal Reflex Action - the withdrawal of hand when finger jabbed unexpectedly with a pin.

10.  Pain and pressure receptors in the skin are stimulated.  Sensory neurons carry the impulses to the spinal cord by way of the dorsal root.  An interneuron picks up the impulse from the sensory and transmits it to the motor neuron.  At the same time the impulse is also transmitted to the brain.  The motor neuron stimulates the specific effector organ to make the appropriate response, muscles in the arm are stimulated to contract pulling the hand away from the pin.  The response is very fact – occur before the brain is aware of the situation.  The brain, having received the information, may transmit impulses to other muscles to modify the response.