Central and peripheral nervous system

what is the central nervous system and peripheral nervous system consist of>

• Central nervous system (CNS) – the brain and spinal cord

• Peripheral nervous system (PNS) – the parts of the nervous system that are not within the central nervous system and that extend to the rest of the body

what are sense organs

The nervous system allows detection of stimuli in the surroundings and the coordination of the body's responses to the stimuli.

Stimuli detected by receptor cells together in sense organs.

what are effectors

parts of the body that respond to stimuli. Effectors can be muscles or glands.

pathway followed by nerve impulses

stimulus  receptor  sensory neurone  CNS motor neurone effector

how nervosu system detects changes in environemnt and responds

• Receptor cells detect changes in the environment, or stimuli

• Nerve impulses travel from the receptor cells along sensory neurones to the central nervous system, or CNS

• The CNS acts as a coordinating centre for the impulses that arrive from the receptors, determining which part of the body needs to respond and sending out a new set of impulses along motor neurones

• Motor neurones send impulses to the effectors to bring about a response

what does PNS do?

• The PNS connects the receptor cells in the sense organs with the CNS, and connects the CNS with effectors

  • The CNS acts as a central coordinating centre for the impulses that come in from, and are sent out to, any part of the body

what are the two types of motor nerves in peripheral nervous system

• The voluntary nervous system: involves motor neurones that are under voluntary or conscious control involving the cerebrum. Voluntary motor neurones function as result of conscious thought.

• The autonomic nervous system: involves motor neurones that the conscious areas of brain don’t control- controls involuntary body functions.

what two sections is autonomic nervous system divided into?

• Sympathetic nervous system

• Parasympathetic nervous system

Structural similarities between the parasympathetic and sympathetic system

• Both have myelinated preganglionic fibres that leave the CNS and synapse in a ganglion (a collection of cell bodies outside the central nervous system) with unmyelinated postganglionic fibres

Structural differences between the parasympathetic and sympathetic systems

• In the sympathetic system, the ganglia are very close to the CNS, so the preganglionic fibres are short and postganglionic fibres are long

• In the parasympathetic system the ganglia are near to or in the effector organ, so the preganglionic fibres are very long and the postganglionic fibres are very short

Functional differences between the parasympathetic and sympathetic autonomic nervous systems

• the sympathetic nervous system produces noradrenaline at the snapses and usually produces a rapid response in target organ system. Sometimes referred to as ‘fight or flight’ system. When you are active. or under physical or pychological stress, the sympathetic nervous system will dominate, stimulating the organs of the body to cope with stress

• the parasympathetic nervous system often has a slower, calming or inhibitory effect on organ systems and produces the neurotransmitter acetylcholine at the synapses. The parasympathetic system maintains normal functioning of the body and restores calm after stressful situation. Referred to as ‘rest and digest’ or ‘feed and breed’ system

• They work antagonistically

what is chemical control?

• often slow by long lasting. Hormones travel around body in plasma of blood

• They move into target cells by diffusion and attack to receptors on cell membranes

• Chemical control often linked to changes which involve growth of an organism and allows for long term responses to environmental changes

• Can also be used for rapid day-to-day responses such as control of blood sugar levels