Biological approach

• What is the nervous system?

  It consists of the CNS and the peripheral nervous system and communicates using electrical signals.
• What is the CNS?

  It consists of the spinal cord and the brain and is the origin of all complex commands and decisions.
• What is the PNS?

  Sends information to the CNS from the outside world and transmits messages from the CNS to effectors.
• What is the somatic nervous system?

  It transmits information to and from receptor cells in sense organs to the CNS.
• What is the autonomic nervous system?

  It transmits information to and from internal organs, the system operates involuntarily and has 2 divisions which are the sympathetic and the parasympathetic nervous system.
• What is the role of the spinal cord in the CNS?

  It transfers messages from the brain to the rest of the body which allows the brain to monitor bodily processes. It also is responsible for simple reflex action and is connected to different parts of the body by pairs of spinal nerves.
• What is the cerebrum?

  It is the largest part of the brain and is further divided into 4 lobes which all have specific functions they are split into two halves known as cerebral hemispheres and they communicate to each other through the corpus callosum.
• What is the cerebellum?

  It controls motor skills and balance in the body and abnormalities can cause speech and motor problems and epilepsy.
• What is the diencephalon?

  It is located beneath the cerebrum and above the brain stem. It contains the thalamus which acts as a relay station for nerve impulses and routes them to the appropriate parts in the brain. It also contains the hypothalamus which regulates hunger, thirst and body temperature, it also links the endocrine and nervous system by controlling the release of hormones from the pituitary glands.
• What is the brain stem?

  It regulates automatic functions that are essential for life, motor and sensory neurons travel through the brain stem allowing impulses to pass between the brain and the spinal cord.
• What is the role of the peripheral nervous system?

  It relays messages from the CNS to the rest of the body and has 2 divisions (somatic and autonomic nervous system).
• What is the role of the somatic nervous system?

  It is made of 12 pairs of cranial nerves and 31 pairs of spinal nerves, both these nerves have sensory and motor neurones. The sensory neurones carry sensory information to the CNS and the motor neurones relay information from the CNS to other areas of the body.
• What is the role of the autonomic nervous system?

  It carries out actions without conscious awareness and plays an important role in homestasis. The ANS is made up of the sympathetic (noradrenaline) and parasympathetic (acetylcholine) nervous system which regulate the same organs but have opposite effects.
• What is the role of the sympathetic nervous system?

  Noradrenaline has stimulating effects and its role is to deal with emergencies and trigger fight or flight whereby impulses travel from neurons in sypathetic NS to every organ and gland to prepare rapidly.
• What is the role of the parasympathetic nervous system?

  The acetylcholine relaxes the individual once the emrgency has passed and sends body into rest and digest to return it to its normal resting state. Any functions that are slowed down are started again for example digestion.
• What is action potential?

  The movement of the electrical impulse in a neuron from the dendron to the axon through the cell body.
• What is a biological structure?

  An arrangement or organisation of parts to form an organ, system or living thing.
• What are neurons?

  They are cells that carry neutral information throughout the body.
• What is the role of sensory neurons?

  Carry impulses from the sensory receptors in eyes/mouth/ears to the brain and spinal cord. They convert information from sensory receptors into neutral impulses and when they reach the brain are translated into sensations e.g pain.
• What is the role of relay neurons?

  They lie between sensory and motor neurons and allow them to communicate. They are only found in the brain and spinal cord.
• What is the role of motor neurons?

  They lie in the peripheral nervous system and project their axons outside of the PNS and directly or indirectly control muscles. They also form synapses with muscles and control their contractions and the strength of the contraction depends on the rate of firing of the axons of the motor neurons that control it.
• What is an excitatory synaptic connection?

  It will make the postsynaptic neuron more likely to fire e.g acetylcholine.
• What is an inhibitory synaptic connection?

  It makes it less likely for the postsynaptic neuron to fire e.g GABA.
• What are neurotransmitters?

  They are chemicals that are released from a synaptic vesicle into the synapse by neurons - some are taken back up by the terminal buttons which is known as reuptake.
• What is summation?

  When excitatory and inhibitory influences are summed, if the net effect on the postsynaptic neuron is inhibitory it is less likely to fire, if the net effect in excitatory it makes it more likey to fire. Action potential is only triggered if the sum of exitatory and inhibitory signals at any one time reaches a threshold.
• What are the steps of synaptic transmission?

  1 Nerve impulses travel down an axon of the presynaptic neuron.

  2 Nerve impulses reach the synaptic terminal.

  3 Action potential in presynaptic neuron triggers the release of neurotransmitters from the vesicles.

  4 Neurotransitters travel through synaptic cleft.

  5 They bind with the receptors on the dendrites of the adjacent neuron.

  6 Neurotransmitter is taken up by postsynaptic neuron.

  7 The message continues to be passed via electrical impulses.