Nervous System

• Receptors detect stimuli and effectors bring about a response to a stimulus.
• Receptors usually communicate with effectors via the nervous system or the hormonal system, sometimes using both.
• The central nervous system is made up of the brain and spinal cord.
• The peripheral nervous system is made up of the neurones that connect to the CNS to the rest of the body. It also contains the somatic NS and autonomic NS.
• The somatic nervous system controls concious activities such as running.
• The autonomic nervous system controls unconcious activities. It has two divisions that have opposite effects on the body.
• The sympathetic nervous systems gets the body ready for action. It's the 'fight or flight' system. Sympathetic neurones release the neurotransmitter noradrenaline.
• The parasympathetic nervous system calms the body down. It's the 'rest and digest' system. Parasympathetic neurones release the neurotransmitter acetylcholine.
• Hypothalamus

  • Found beneath the middle part of the brain.
  • Maintains body temperature.
  • Produces hormones that control the pituitary gland.
• Cerebrum

  • Largest part of the brain.
  • Divided into two halves called cerebral hemispheres.
  • Has a thin outer layer called the cerebral cortex which is highly folded.
  • Involved in vision, hearing, learning and thinking.
• Pituitary Gland

  • Found beneath the hypothalamus
  • Controlled by the hypothalamus and stimulates other glands
• Medulla Oblongata

  • At the base of the brain, at the top of the spinal cord.
  • Automatically controls breathing rate and heart rate.
• Cerebellum

  • Underneath the cerebrum and it also has a folded cortx.
  • Important for muscle coordinatio, posture and coordination of balance.
• A reflex is where the body responds to a stimulus without making a concious decision to respond. This is because the pathway of communication doesn't involve conscious parts of the brain.
• Simple reflexes help organisms to aviod damage to the body because they're rapid.
• Blinking Reflex - When your body detects something that coould damage your etem you automatically blink - you quickly close your eyelid to protect your eye, then open your eyelid again.
• Blinking relfex - Sensory nerve endings in the cornea are stimuated by touch which sends a nerve impulse along the sensory neurone to a relay neurone in the CNS. The impulse is then passed from the relay neurone to motor neurones which send impulses to effectors which use orbicularis oculi muscles to close your eye.
• The knee-jerk reflex works to quickly straighted your leg if the body detects your quadriceps is suddenly stretched. It helps to maintain posture and balance. For example, if your knees buckle after landing from a jump, the relfex causes your quadriceps to contract and keep you upright.
• Knee-jerk reflex - Stretch receptors in the quadricep muscle detect that the muscle is being stretched. A nerve impulse is passed along a sensory neurons, which communicates directly with a motor neurone in the spinal cord. The motor neurone carries the impulse to the effector causing it to contrct so the lower leg moves forward quickly.