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