Physiological Control Systems
1- Homeostasis: Maintenance of a relatively stable internal environment
(e.g. Temperature, [O2], pH, levels of nutrients, waste products & electrolytes)
homoeostasis is essential for cell survival
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2- the nervous sys
the afferent NS
towards the CNS
efferent NS
away from CNS
Somatic NS ⭐
Autonomic NS ⭐
neurologic system that allows the individual to respond
voluntarily to consciously perceived sensory signals
consists largely of responses giving
rise to voluntary skeletal muscle contraction
neurologic system that acts to maintain
homeostasis (a steady state) in the body.
not under conscious
control
innervates the heart, the smooth
muscle of blood vessels and the visceral organs
lungs, intestine, bladder, glands and genitalia.
how ANS maintains homoeostasis?
Physiological/environmental change
Sensory neurons
Sensory information
Central Nervous System
(Esp. brainstem and hypothalamus)
Activation of autonomic nerves
Muscle contraction or relaxation (smooth & cardiac)
OR activation/inhibition of secretion (glands)
Physiological response
Homeostasis
Anatomy of an autonomic neuron
preganglionic neuron
postganglionic neuron
synapse in ganglia
neurotransmitter released in 2 end plate regions
advantages of 2 neuron train
cell body in CNS
Cell body in Ganglia
end plate region in ganglia
end plate region next to effector cell
one preganglionic neuron can synapse onto many postganglionic neurons
either excitatory and inhibitory postganglionic neurons
information from sensory network can have direct rapid , reflex effects on output
3- divisions of the autonomic nervous system
1- sympathic
2- parasympathic
3- Enteric (gut)
seperation of ANS nto sym and para based on
anatomical differences
physiological differences
mist viceral organs are innervated by both the syp and para nerve fibrers
4- Sympathetic
nerve fibres leave from thoracic(T) and Lumbar (L) regions of spinal cord
sympathetic trunk ⭐
most Sympathetic ganglia lie close to the spinal cordand form a body known as ''
5- Parasympathetic
parasympathetic ganglia
lie within or near the organ
innervated
• They act independently
Nerve fibres leave from
brain and
Sacral regions of the spinal cord.
6-Autonomic control of viscera
innervated by both
sympathetic and parasympathetic nerve fibers
symp and para exert opposite effects on a
particular organ.
sympathetic stimulation
increases the heart rate.
parasympathetic stimulation
decreases heart rate
symp and para can be stimulatory or inhibitory
normal circumstances
both systems are partially active
normal ‘tonic’ level of nerve impulse activity sent
through both systems
The balance between the system
changes throughout the normal daily activities
depending on
which system is required for homeostasis.
activated when we get out
of bed in the morning
to
maintain blood pressure in the
head
Greater blood pressure is
required to counter the effects of
gravity and maintain blood flow
to the brain, when changing from
a reclining to a standing position