The Autonomic Nervous System Flashcards
What is the ANS ?
The autonomic nervous system (ANS) is largely involuntary and regulates physiologic processes
Where does the ANS originate?
Just above the spinal cord in a region of the brain stem called the Medulla
What are the two main divisions of the ANS ?
It has two main divisions:
Sympathetic and Parasympathetic. These divisions have opposite effects and work reciprocally
What do all homeostatic behaviours arise from ? and mediated by ?
All homeostatic behaviour arises from neural modulation of organ systems, which is mediated by hypothalamic control of the autonomic and the endocrine system
What do the physiological responses of the body need to be ?
Co-ordinated. The fight and flight response: - Heart pounding; increase in rate of the heartbeat and force of contraction - Breath becomes rapid and shallow - Dry mouth - Sweaty palms - Muscles tense
When does the activity in the Sympathetic Division increase?
- Rest&Digestion to Fight&Flight
This is when the body is under stress so sympathetic activation causes an increased heart rate, the force of contraction, and rate of conduction, allowing for increased cardiac output to supply the body with oxygenated blood
When does the activity in the Parasympathetic Division increase?
- Fight&Flight to Rest&Digestion
The parasympathetic nervous system is responsible for the body’s rest and digestion response when the body is relaxed, resting, or feeding. It basically undoes the work of sympathetic division after a stressful situation. The parasympathetic nervous system decreases respiration and heart rate and increases digestion
What are within the cell bodies and what do they do?
Within the medulla are nerve cell bodies that
spontaneously fire action potentials, e.g.
cell bodies of parasympathetic vagus nerves
and also cells that regulate sympathetic
activity
What is the activity within the ANS regulated by ?
- Sensory receptors in the body that monitor physiological function and respond to mechanical, chemical or thermal stimuli. e.g. baroreceptors, in blood vessels and heart respond to stretching with increased activity and send response to NTS (nucleus
tractus solitarius) in medulla to stimulate parasympathetic (vagal) activity and reduce sympathetic output. - In this way ANS responds to changes in pressure within the cardiovascular system
Explain the Baroreceptor Reflex ?
- Baroreceptors detect changes in arterial pressure
- Signals sent to the medulla of the brain stem
- Heart rate adjusted
What’s one thing that the autonomic regions of medulla receive ?
Inputs from hypothalamus. This is involved, for example, in how the body responds to exercise and thermal stress with changes to cardiac and vascular function
What’s another thing that the autonomic regions of medulla receive ?
Input from higher brain regions such as the cortex. This is involved in body’s response to fear and stress.
Where do the cell bodies of the two divisions of the ANS originate ?
- Thoracic and lumbar regions for sympathetic pre-ganglionic
fibres - Medulla and Sacral regions for the parasympathetic pre-ganglionic fibres
Where is the location of the autonomic ganglia in the Sympathetic chain located ?
- In close proximity to the spinal cord and the Celiac and
Mesenteric ganglion for
pathways innervating GI
tract and reproductive
organs - Pre-ganglionic fibres are generally short
Where is the location of the autonomic ganglia in the Parasympathetic division located ?
- The ganglia lie
close to the target
tissues so pre-ganglionic fibres are long and post-
ganglionic fibres are short.
