The divisions of the nervous system: central and
peripheral (somatic and autonomic)
The human nervous system is a collection of neurons
across the body that detects information from the
environment and processes this, then directs the body to
take action via the muscles and/or glands. It is split into
the Central nervous system (CNS) and the Peripheral
nervous system (PNS).
● The CNS is responsible for our complex
processing. It consists of the brain (the centre of all
conscious and most unconscious processing) and the
spinal cord (this receives and transmits information).
● The PNS is the portion of the nervous system that
is outside the brain and spinal cord. The primary function
of the peripheral nervous system is to connect the brain
and spinal cord to the rest of the body and the external
environment.
★ The peripheral nervous system is split into the somatic and autonomic nervous
systems
★ Somatic Nervous System (SNS) connects the central nervous system with the senses
and is composed of sensory nerve pathways bring information to the CNS from
sensory receptors, dealing with touch, pain, pressure, temperature etc, and motor
nerve pathways which control bodily movement by carrying instructions towards
muscles
● Autonomic Nervous System (ANS) controls bodily arousal (how ‘excited’ or relaxed
we are), body temperature, homeostasis, heart rate and blood pressure. It is
composed of the sympathetic and parasympathetic nervous systems. the
sympathetic ANS is involved in preparing the body for fight or flight, so causes
increased arousal (e.g. increase in heart rate and blood pressure, pupil dilation,
reduction in digestion and salivation)and the parasympathetic ANS is used to return
our body back to its normal state after the fight or flight response, so leads to
decreased arousal.
Under normal conditions there is a balance between the sympathetic and parasympathetic
systems in order to maintain homeostasis.
, CENTRAL NERVOUS SYSTEM (brain & spinal cord)
Similarities:
● The brainstem and spinal cord both control involuntary processes (e.g. the brain
stem controls breathing and the spinal cord controls involuntary reflexes).
Differences:
● The brain provides conscious awareness and allows for higher-order thinking, while
the spinal cord allows for simple reflex responses.
● The brain consists of multiple regions responsible for different functions, whereas
the spinal cord has one main function.
PERIPHERAL NERVOUS SYSTEM (somatic/autonomic &
sympathetic/parasympathetic)
Similarities:
● The sympathetic nervous system (part of the autonomic nervous system) and the
somatic nervous system respond to external stimuli. The sympathetic nervous
system responds to external stimuli by preparing the body for fight or flight and the
somatic nervous system responds to external stimuli by carrying information from
sensory receptors to the spinal cord and brain.
Differences:
● The autonomic nervous system consists of two sub-components, whereas the
somatic nervous system only has one.
● The somatic nervous system has sensory and motor pathways, whereas the
autonomic nervous system only has motor pathways.
● The autonomic nervous system controls internal organs
and glands, while the somatic nervous system controls muscles
and movement.
The function of the endocrine system: glands and
hormones
The Endocrine system is a series of glands located across the
body which release hormones. These enter the bloodstream and
send messages to other parts of the body. This is slower than
the nervous system but can have stronger and longer lasting
effects.
● The Hypothalamus is connected to the pituitary gland
and is responsible for stimulating or controlling the release of
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