introduction to the autonomic nervous system Flashcards
what are the components of a neuron?
dendrite, cell body, nucleus, axon hillock, myelin sheath (pre-ganglionic), schwann cell, nodes of ranvier, axon terminal
what are the two main divisions of the nervous system?
central
peripheral
what are the components of the central nervous system?
brain
spinal cord
what are the divisions of the peripheral nervous system?
motor neurons - somatic and autonomic
sensory neurons
spinal nerves, cranial nerves, and ganglia
what are the divisions of the autonomic nervous system?
sympathetic
parasympathetic
what is the somatic nervous system?
under voluntary control
innervates skeletal muscle
motor neuron is one continuous structure
what is the autonomic nervous system?
sympathetic and parasympathetic
under involuntary control
innervates cardiac muscle, smooth muscle, and glands
two motor neurons - one pre-ganglionic and one post-ganglionic
what is the sympathetic nervous system?
‘fight or flight’
controls function in times of stress
short pre-ganglionic neuron
long post-ganglionic neuron
adrenergic neurotransmitters - e.g. adrenaline, long lasting effect
what is the parasympathetic nervous system?
‘rest and digest’
controls day to day function
long pre-ganglionic neuron
short post-ganglionic neuron
cholinergic neurotransmitters - e.g. acetylcholine, effects are brief as they are inactivated quickly in the synaptic cleft.
what are afferent sensory neurons
relay information from sensory receptors to initiate an effector response to restore homeostasis
what are efferent motor neurons
travel from the central nervous system to a target organ or tissue
what are the functions of the autonomic nervous system
sympathetic and parasympathetic divisions of the ANS often work simultaneously in a reciprocal and complementary manner maintaining homeostasis
what are the functions of the sympathetic nervous system
orchestrates the stress response and energy consumption
associated with ‘fight or flight’ reactions, but also has very important ongoing activity
what are the functions of the parasympathetic nervous system
regulates many functions, some of which are restorative and energy conserving ‘rest and digest’
which parts of the body have a role in maintaining homeostasis
skin
liver/pancreas
lungs
heart & vasculature
kidneys
what is the role of the skin in maintaining homeostasis
thermoregulation by controlling contraction and relaxation of smooth muscle vasculature
what is the role of the liver/pancreas in maintaining homeostasis
metabolism of glucose and lipids
what is the role of the lungs in maintaining homeostasis
ventilation to control partial pressures and pH
what is the role of the heart and vasculature in maintaining homeostasis
blood pressure by contraction and relaxation of smooth muscle in the vasculature
what is the role of the kidneys in maintaining homeostasis
osmoregulation (water and electrolyte balance)
acid-base balance
blood pressure regulation
what are the principles of control of homeostasis
homeostasis generally involves a negative feedback loop which has three parts:
1. a sensor
2. a comparator/integrator - in the CNS, initiate an effector response via efferent neurons
3. an effector
anatomy of the sympathetic nervous system
short myelinated pre-ganglionic neuron that synapse in paravertebral or prevertebral ganglia
ganglia in the pre- and para-vertebral
long unmyelinated post-ganglionic neuron
anatomy of the parasympathetic nervous system
long myelinated pre-ganglionic neurons that synapses in or on target tissues/organs
short unmyelinated post-ganglionic neurons
what are pre-ganglionic neurons
cell bodies arise in the central nervous system
project axons which leave the CNS ad synapse at pre- and post- vertebral ganglia
what are ganglia
collections of cell bodies
what are post-ganglionic neurons
cell bodies arise in ganglia
what is the neurotransmitter in the sympathetic nervous system
pre-ganglionic = acetylcholine to nicotinic Ach receptor
post-ganglionic = noradrenaline to adrenoceptor
what is sympathetic regulation of vascular smooth muscle tone
↑ vascular tone = vasoconstriction
1. ATP produces a fast contraction of the smooth muscle
2. noradrenaline produces a moderately fast response
3. neuropeptide Y produces a slow response
what is the neurotransmitter in the parasympathetic nervous system
pre-ganglionic = acetylcholine to nicotinic Ach receptor
post-ganglionic = acetylcholine to muscarinic Ach receptor
what is parasympathetic regulation of vascular smooth muscle tone
↓ vascular tone = vasodilation
1. acetylcholine and nitric oxide produce a rapid relaxation
2. vasoactive intestinal peptide can produce a slow, delayed response
what are non-adrenergic, non-cholinergic (NANC) transmission
neurotransmission caused by non-adrenergic, non-cholinergic transmission
sympathetic = ATP or neuropeptide Y
parasympathetic = nitric oxide or vasoactive intestinal peptide
what are cholinoceptors
acetylcholine is the endogenous agonist of cholinoceptors that are nicotinic, or muscarinic
what is the nicotinic acetylcholine receptor
present in the ganglia
ligand-gated ion channels
what is the muscarinic acetylcholine receptor
present in the effector cells
G-protein coupled receptors
what are adrenoceptors
noradrenaline and adrenaline are the endogenous agonists of a family of adrenoceptors
all are G-protein coupled receptors
effects of the sympathetic nervous system on targets
- pupil dilation - alpha1 - noradrenaline
- airway relaxation - beta2 - noradrenaline
- increased rate and force of heart contraction - beta1- noradrenaline
- sweat gland secretion - mAchR - acetylcholine
- penile ejaculation - alpha1 - noradrenaline
effects of parasympathetic nervous system on targets
- pupil constriction - mAchR - acetylcholine
- airway contraction - mAchR - acetylcholine
- decreased heart rate - mAchR - acetylcholine
- penile erection - mAchR - acetylcholine
