ANS typed - Autonomic Nervous System Slide 3 Autonomic...

Autonomic Nervous System
Slide 3 Autonomic Nervous System
 Viscera are your internal organs- so this is the nervous system that mediates functionality in most
internal organs
 Like pupil diameter, heart rate, blood pressure, digestion, secretion of hormones
 Function is to provide homeostasis
 ANS reflex example - Baroreceptors send information back and determine outflow of the
autonomic nervous system to control blood pressure throughout the body
 The ANS is not like a normal light switch that turns on and off. The ANS is always active. It acts
more like a dimmer switch.
 This continuous outflow from the ANS is called tonic activity. The neurons are always firing. You
can up or down regulate by increasing or decreasing inputs from the ANS
 Two divisions are the sympathetic and parasympathetic nervous system.
 Most organs tend to be innervated by both systems
 Sympathetic usually stimulates activity and parasympathetic inhibits the activity.
 The divisions use different chemical signals, different neurotransmitters, different distribution of
nerves that release the ANS neurotransmitters and a different distribution of receptors to receive
the signal
Slide 4 ANS homeostasis
 These are things the ANS controls at individual organs
 The ANS does not require a signal from the CNS however its activity can be modified and up or
down regulated by signals from the higher CNS
 Signals originate in the hypothalamus, pons, medulla, spinal cord and are affected by higher CNS
inputs (like for emotional responses- when youre embarrassed with toilet paper on your shoe.
Allows for flushing on your face and the butterfly feeling and if you start sweating. )
Slide 5 ANS + MNS
 Part of the PNS (sensory system) which is the afferent system
 The ANS and the MNS (motor) both make of the efferent (outflow) pathways to the periphery
 MNS is controlled by the CNS and ANS is modulated by the CNS
 MNS outflow is always excitatory. It excites the effector tissue (muscle). ANS is tonic so it can
increase or decrease activity
 ANS uses Ach and NE ( the sole neurotransmitters in AN neurons)
 The MNS uses only Ach (cholinergic)
 Norepinephrine is always called noradrenaline
 In addition to being released at axons, the ANS neurotransmitters can also be released at
varicosities which are swellings along the axons prior to the axon terminal
 There are some non-adrenergic and non-cholinergic neurons which can release instead substance
P or NO or ATP. It’s based on whether its sympathetic or para based on its origin not on which
neurotransmitter it secretes.

Slide 6 ANS is efferent periphery
• This is an efferent system and it sends signals to the periphery
• Pathway is composed of two neurons
• First neuron is preganglionic neuron. The cell body is in the spinal cord or in the brain stem.