The Autonomic Nervous System Flashcards
The efferent division of the peripheral nervous system
Somatic/motor: Voluntary movement, innervation of skeletal muscle
Autonomic nervous system (ANS): Involuntary functions, innervation of organs, glands
Sympathetic nervous system
Parasympathetic nervous system
The autonomic nervous system
Involuntary maintenance of homeostasis
Automatic regulation of:
Body temperature
Cardiovascular activity
Respiratory functions
Digestive functions
Two branches of the autonomic nervous system
Sympathetic nervous system
-‘fight or flight’
-prepares body for action
Parasympathetic nervous system
-‘rest and digest’
-relaxes the body
Role of the sympathetic division
Referred to as “fight or flight” system
Activated during exercise, excitement, anxiety, fear, or embarrassment
Effects include:
Adrenaline release
Increased heart rate
Dry mouth
Cold, sweaty skin
Dilated pupils for far vision
During exercise:
Diverts blood to skeletal muscles and heart
Role of the parasympathetic division
Referred to as “rest-and-digest” system
Keeps body energy use low
Directs digestion, diuresis, defecation
Activated during relaxation and pleasure activities
Effects include:
Lower blood pressure, heart rate, and respiratory rates
Glucose uptake into cells
How many neurons does the autonomic nervous system have in its efferent pathway
2
Ganglion
collection of cell bodies outside of the central nervous system
similarities between ANS divisions
- Both divisions innervate most organs
- Both have 2 neurons between CNS and effector organ (usually)
Three main differences between sympathetic and parasympathetic divisions:
- Sites of Origin:
-Parasympathetic fibres originate in the brain and sacral spinal cord.
-Sympathetic fibres originate in the thoracic and lumbar regions of the spinal cord. - Relative Fiber Lengths:
-Parasympathetic NS has long preganglionic and short postganglionic fibres.
-Sympathetic NS has short preganglionic and long postganglionic fibres. - Location of Ganglia:
-Parasympathetic ganglia are located in or near their visceral effector organ.
-Sympathetic ganglia lie close to the spinal cord.
The sympathetic NS also innervates the adrenal medulla, what is the adrenal medulla
adrenal medulla = glands on top of the kidneys that release adrenaline and noradrenaline as hormones into the blood stream
Sympathetic innervation of the adrenal medulla
Adrenal medulla: Receives input from a long sympathetic preganglionic neuron.
Activation: Releases adrenaline and noradrenaline into the bloodstream.
Effects: Induce slower, long-lasting sympathetic responses throughout the body.
Neurotransmitters of the ANS
Acetylcholine (ACh)
Noradrenaline (NA; norepinephrine, NE)
Acetylcholine:
Released by all ANS preganglionic axons.
Released by all parasympathetic postganglionic axons.
Noradrenaline:
Released by almost all sympathetic postganglionic axons, except those at sweat glands.
Acts as a hormone for a slower response.
Acetylcholine receptors (acts on ligand gated ion channels)
-Nicotinic receptors
-Muscarinic receptors
1)Nicotinic receptors
Type pf Ligand-gated ion channels:
Permeable to sodium ions.
ACh via nicotinic receptors always stimulatory, opening ion channels and depolarizing postsynaptic cells.
Found on:
All postganglionic neurons (sympathetic and parasympathetic).
Cells in the adrenal medulla.
Skeletal muscle cells at the neuromuscular junction
2) Muscarinic receptors (g protein coupled receptors)
-ACh’s effect on muscarinic receptors can be inhibitory or excitatory, depending on the target organ’s receptor type.
Found on:
All cells activated by postganglionic parasympathetic neurons.
Sweat glands innervated by postganglionic sympathetic neurons.
