co-ordination and control

• The central nervous system (CNS) consists of the brain and spinal cord.
• communication and co-ordination in animals = The nervous system sends electrical impulses along nerves to and from different parts of the body. Nerves are made from bundles of specialised cells called neurones and they link the central nervous system (CNS) which is the brain and spinal chord to the receptors and effectors. It all starts with a change in the environment.
• stimulus= change in the environment of an organism.
• receptor= organ that detects the stimulus
• response= reaction of the organism to the stimulus
• effector= organ that carries out a response
• CNS = brain and spinal chord - involved in making decisions about the situation
• correct sequence of events =1. stimulus 2. receptor (information gathered) 3. CNS(brain deciding what to do) 4. effector(CNS sends information to effector) 5. response
• receptor cells convert the energy in the stimulus to electrical energy which can be transmitted in the nervous system as electrical impulses
• nerves are made of specialised cells called neurones
• The nervous system sends electrical impulses along nerves to and from different parts of the body.
• neurones link the central nervous system to the receptors and effectors
• in the CNS information is gathered from the receptors and processed as the brain decides what to do and sends an appropriate responses to the effectors.
• Neurones are the components of the nervous system and they are interconnected and the connect the nervous system together.
• neurones are special elongated cells which are adapted for carrying electrical impulses.
• Different neurones carry out different jobs and they carry electrical impulses in certain directions.
• sensory neurone - carries electrical impulses from a receptor to the association neurone (in CNS)

  
• association neurone - carries electrical impulses from a sensory neurone to a motor neurone (in CNS)

  
• motor neurone- carries electrical impulses from association neurone ( in CNS ) to an effector

  
• diagram of neurones connected. impulses need to pass from one neurone to another.

  
• The junction between two neurones is called a synapse and messages are passed across by chemical transmitter molecules.
• when a spinal chord is drawn in a transverse direction.

  A) dorsal root

  
• spinal nerves divide into 2 roots at the point where they join the spinal chord. Sensory neurones enter through the dorsal root and motor neurones leave through the ventral root. Both neurones are contained in the same spinal nerve. The cell bodies of the sensory neurone are in the dorsal root and they make a bulge called a ganglion.
• The electrical impulse travels from the sensory neurone , through the association neurone and to the motor neurone.
• diagram of the reflex arc.

  
• How the reflex arc works - 1. stimulus(hot candle- pain) detected by receptor(nerve endings in skin) 2. electrical impulse travels along the sensory neurone 3. association neurone carries impulse to motor neurone 4. motor neurone passes impulse to effector ( arm muscle) 5. muscle contracts (response)
• sensory neurones are in the dorsal root and they bulge to make a ganglion.
• The arrangement of the sensory neurone, association neurone and motor neurone is called a reflex arc.
• reflex actions are important protective devices because they produce an immediate response to danger.
• the response of a reflex action is rapid because the distances involved are short and few neurones are involved
• a reflex action does not require conscious thought
• although the brain is not involved in making the decision in a reflex action, it is aware of the response which has been made
• a voluntary action is a response which is achieved as a result of conscious thought(voluntary response )
• voluntary responses use the same neurone pathways as reflex responses but the response is controlled by the brain via neurones which connect the spinal chord to the brain.
• The movement of skeletal muscles during locomotion is under the control of the brain (voluntary response)
• reflex action is rapid and involuntary action is slower and controlled by the brain.
• nerves can carry electrical messages very quickly from one part of the body to another part of the body in animals
• animals and humans also use chemicals to transfer information in their bodies. These chemicals are called hormones and are made in endocrine glands.
• hormones are made in endocrine glands and these glands have a good blood supply so when the gland produces a hormone it releases it directly into the blood. The hormone is carried through the blood to a specific target organ where it acts.
• the pancreas is an endocrine gland that produces the hormone insulin which travels in the blood to the liver and muscles and the insulin reduces blood glucose levels.