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The mammalian nervous system (Peripheral nervous system (PNS) (Sensory…
The mammalian nervous system
Responding to the environment
stimulus
any change in the internal or external environment is a stimulus
responding to a stimulus can involve coordination between nervous, hormonal and muscle systems.
communication system
detects changes in the environment
cell signalling occurs between all parts of the body
coordination of a range of effectors to carry out responses to the sensory input
suitable responses
Divisions of the nervous system
central nervous system
brain
spinal cord
peripheral nervous system
sensory system
motor system
somatic nervous system
autonomic nervous system
sympathetic system
parasympathetic system
Central nervous system (CNS)
Spinal cord
many non-myelinated
grey matter
myelinated neurones
makes up outer region of white matter
these are for rapid communication
Protected by vertebral column
Brain
86 billion neurones
relay neurones
multiple connections for complex neural pathways
mostly non-myelinated
grey colour
known as grey matter
Peripheral nervous system (PNS)
Sensory nervous system
They conduct action potentials from sensory receptors into the CNS
Motor nervous system
somatic
made of motor neurones
conducts action potentials under voluntary control
mostly myelinated
e.g. skeletal muscles
only one single motor neurone connecting the CNS to effector
autonomic
motor neurones
conduct action potentials from CNS to effectors
not under voluntary control
e.g. glands, cardiac muscle, smooth muscle
mostly non-myelinated
at least two neurones involved in connection between CNS and each effector.
these neurones are connected at ganglia (small swellings)
Sympathetic system
prepares body for activity
antagonistic to parasympathetic
Parasympathetic system
conserves energy
antagonistic to sympathetic
Usually bundled together in a connective tissue sheath to form nerves
Parasympathetic and sympathetic systems
Sympathetic
many nerves out of CNS
each nerve to new effector
ganglia just outside CNS
short preganglionic neurones
long post-ganglionic neurones
uses noradrenaline as neurotransmitter
increases activity
effects
increase heart rate
dilate pupils
increase ventilation rate
reduce digestive activity
Parasympathetic
a few nerves leading out of CNS
these divide up and each lead to different effectors
ganglia in effector tissue
long pre ganglionic neurones
short post ganglionic neurones
acetylcholine is neurotransmitter
decreases activity
most active during sleep or relaxation
effects
decrerases heart rate
constricts pupils
reduces ventilation rate
increases digestive activity
sexual arousal
