CNS, neuron and synapses

• The nervous system has 2 main parts – the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
• The brain is the main data centre of the body and consists of the cerebrum which regulates higher level functioning

  such as thought, and the cerebellum which maintains coordination
• The brain stem includes the midbrain, pons, and medulla, and controls lower level functioning such as respiration

  and digestion. It connects the brain and the spinal cord.
• The spinal cord connects the brain and the body's main receptors, and serves as a conduit for sensory input

  and motor output.
• The cerebrum: In humans it is the largest part of the brain and is the seat of motor and sensory functions, and the higher mental functions such as consciousness, thought, reason,emotion, and memory
• The spinal cord:A thick, whitish cord of nerve tissue which is a major part of the central nervous system. It extends from the brain stem through the spine, with nerves branching off to various parts of the body.
• brain stem :The part of the brain that connects the spinal cord to the forebrain and cerebrum.
• The cerebellum: Part of the hindbrain in vertebrates. In humans it lies between the brainstem and

  the cerebrum, and plays an important role in sensory perception, motor output,

  balance and posture.
• Lateralisation: Two hemispheres have different

  functions
• Localisation: Certain areas are responsible for

  different functions
• What connects the two hemispheres of the

  brain? A dense collection of nerve cells called

  the corpus callosum.
• Pre-frontal cortex – higher cognitive functions e.g.

  problem solving
• Limbic System – emotion centre of the brain
• Amygdala – part of the limbic system. Assess and

  responds to environmental threats
• Pituitary – gland. Helps regulate endocrine system
• Hippocampus - memory
• Thalamus – relay station (receives from senses and

  passes on), filter, plays a role in sleep
• Hypothalamus – Motivation, stress, homeostasis.

  Regulates the endocrine system via pituitary. Gland
• Three types of neurons Relay neuron Sensory neuron Motor neuron
• Neurons receive, process and transmit messages through

  chemical and electrical signals within the body.
• Relay neuron – in the central nervous system, they connect sensory and motor neurons together

  (and some relay neurons too).
• Sensory neuron – in the peripheral nervous system they receive information from

  the senses and carry messages from the sensory receptors to the central nervous system.
• Motor neuron – in the peripheral nervous system they carry messages from the central

  nervous system and cause a response in an effector (muscle/gland) e.g. muscle movement.
• When a neuron is in a resting state the inside is negatively

  charged, compared to the outside.
• When a neuron is sufficiently activated by a stimulus the

  inside becomes positively charged for a split second.
• The rapid switch from negative to positive

  is called depolarisation.
• This creates an electrical impulse called an action

  potential that travels down the axon towards the terminal

  buttons. This is called firing an action potential.
• Messages in the brain are sent by using electrical impulses and

  chemicals called neurotransmitters
• The electrical impulse in the presynaptic neuron cannot "jump" across the synaptic gap, so signals have to be transmitted chemically.
• The neurotransmitters are then reabsorbed by the presynaptic neuron (reuptake) to be used again.
• When the action potential reaches the terminal buttons it triggers the release of neurotransmitters from the presynaptic neuron.
• Tiny sacs called synaptic vesicles release the neurotransmitters into the synapse.
• Chemicals diffuse across the synaptic gap until they are picked up by receptors on the dendrite on the postsynaptic neuron.
• Each neurotransmitter will fit into a matching receptor site with a corresponding shape on the postsynaptic neuron.
• The neurotransmitter changes the chemical balance at the receptor site causing an action potential to fire along the next neuron.
• 1. When the action potential reaches the terminal buttons it triggers the releaseof neurotransmitters from the presynaptic neuron.

  2. Tiny sacs called synaptic vesicles release the neurotransmitters into the synapse.

  3. These chemicals diffuse across the synaptic gap until they are picked up

  by receptors on the dendrite on the postsynaptic neuron.
• 4. Each neurotransmitter will fit into a matching receptor site with a

  corresponding shape on the postsynaptic neuron.

  5. The neurotransmitter changes the chemical balance at the receptor site

  causing an action potential to fire along the next neuron.

  6. The neurotransmitters are then reabsorbed by the presynaptic

  neuron (reuptake) to be used again
• excitatory neurotransmitters include glutamate, dopamine
• inhibitory neurotransmitters include GABA, serotonin
• post Synaptic neuron is the neuron that receives the signal from the presynaptic neuron