Autonomic Nervous System Flashcards
Two division of the Motor Nervous System:
- Somatic Nervous system
- Autonomic Nervous system
How is ANS linked to target tissue?
Two neural pathway:
- pre-ganglionic neuron in: CNS
- Post-ganglionic neuron in: Autonomic Ganglion
- Neuroeffector Junction in: Peripheral Tissue
Division of the Autonomic Nervous System:
Sympathetic: fight or flight
Parasympathetic: rest & digest
Sympathetic Nervous system Functions:
- preps body to fight or escape
- preps body for esoteric activities i.e. exercise
- involved in behavioral responses e.g. stress & fear
Consequences of Increased Activity of Sympathetic Division:
- ^ heart rate
- ^ blood pressure/stroke volume
- dilation of pupils, airways, & blood vessels to muscles
- contraction of urogenital sphincters
- decreased motility of digestive tract
- reproductive system attenuated
collectively: ^ BSL, enhance delivery of oxygenated blood to muscle, & potentiate visual awareness
Parasympathetic Nervous System Functions:
- preps other systems of body for rest
facilitates relaxation & recuperation - restores metabolic energy stores & enables rest & recovery
Consequences of Increased Activity of Sympathetic Division:
- decreased heart rate
- constriction of pupils
- increased motility & secretion of digestive enzymes in digestive tract
- decrease in metabolic rate
- relaxation of urogenital sphincters/ stimulation of defecation & urination
Sympathetic Pre-ganglionic Neurons:
- cell body: lateral horns of upper spinal cord
- small diameter myelinated axon leaves spinal cord via ventral roots
- synapses with post ganglionic neurons in sympathetic chain ganglia or collateral ganglia
- short neurons
Sympathetic Post-ganglionic Neurons:
- cell bodes in either sympathetic chain ganglia or collateral ganglia
- small diameter eliminated axons & axon terminal in peripheral nerves
- comparative long(compared to pre-ganglionic neurons of sympathetic division)
Parasympathetic Pre-Ganglionic Neurons:
- cell bodies in brain stem or lateral horns
- unmeylinated axons leave brain stem via cranial nerves or spinal cord via ventral roots
- synapse with post-ganglionic neurons in terminal ganglia in/ close to peripheral tissue they innervate
- long neurons
Parasympathetic Post-ganglionic Neurons:
- cell bodies in termianl ganglia or peripheral tissue
- short, small diameter myelinated or unmyelinated axons in peripheral nerves
- short neurons
Sympathetic: Neurotransmitter & receptor of Pre-Ganglionic Neurons:
- releases neurotransitter (ACh)
- ACh binds to nicotinic acetylcholine receptor (ionotropic receptor)
- causes excitation of post-ganglionic
- depolarizes post-synaptic membrane by opening a cation non-selective channel
- ESPS large enough to cause AP in Post-G
- excites Post-G neurons
Sympathetic: Neurotransmitter & receptor of Post-Ganglionic Neurons:
- releases nor-adrenaline as neurotransmitter
- receptors (adrenergic receptors) located in plasma membrane innervated by post-G neurons
Parasympathetic: Neurotransmitter & receptor of Pre-Ganglionic Neurons:
- releases ACh as neurotransmitter
- ACh binds to nicotinic acetylcholine receptors (ioniotropic receptor)
- depolarizes post-synaptic membrane by opening cation non-selective ion channel
- ESPS large enough to cause AP in Post-G
- excites Post-G neurons
Sympathetic: Neurotransmitter & receptor of Post-Ganglionic Neurons:
- releases acetylcholine as neurotransmitter
- binds to muscarinic acetylcholine receptors
- metabolic receptors
- mediate their effect by an intra-cellular second messenger
Dual Innervation:
- most visceral organs are innervated by sympathetic & parasympathetic divisions
- two division usually exert opposite effects
Example of Dual Innervation - Eyes:
Sympathetic: pupil dilate
Parasympathetic: pupil constrict
Example of Dual Innervation - Liver:
Sympathetic: glycogen breakdown
Parasympathetic: glycogen synthesis
Example of Dual Innervation - Heart:
Sympathetic: increased rate of contraction, increased force of contraction
Parasympathetic: decreased rate of contraction, decreased force of contraction of atria.
Example of Dual Innervation - Lungs:
Sympathetic: dilation of bronchioles
Parasympathetic: constriction of bronchioles
Example of Dual Innervation - Digestive System:
Sympathetic: decreases motility, contraction of sphincters, decreased secretions.
Parasympathetic: increased motility, relaxation of sphincters, increases secretions
Antagonistic Effect in Autonomic System:
organ is controlled by two different kinds of nerves (double innervation), and the effects of nerves on the organ are opposite
Cooperative Effects in Autonomic System:
Some tissues that receive dual innervation act cooperatively to produce the same effect.
e.g. both division work together to produce an erection
What structures are innervated by only ONE division of ANS?
Skin, Blood Vessel, Tear Glands
Which division is skin innervated by & what is its effect?
Sympathetic:
- sweat gland secretion, contraction of arrector pili muscles
Which division are blood vessels innervated by & what is its effect?
Sympathetic:
- vasoconstriction of skin & digestive tract blood vessels
- dilation of skeletal & cardiac muscle blood vessels
Which division are tear glands innervated by & what is its effect?
Parasympathetic:
- secretion of tears
Three Structural components of Adrenal Medulla:
- Adrenal Gland
- Outer Shell (Cortex)
- Inner Core (medulla)
Structural components of Adrenal Medulla - Adrenal Gland:
- small endocrine gland (top of kidneys) innervated by ANS
Structural components of Adrenal Medulla - Outer Shell (Cortex)
- steroid hormones
Structural components of Adrenal Medulla - Inner Core (Medulla)
- chromaffin cells -> innervated by sympathetic pre-G neurons
- secretes adrenaline & nor-adrenaline into blood stream
- reinforces actions of sympathetic division
Major difference between the adrenal medulla and sympathetic post-ganglionic neurons
- chemicals secreted by adrenal medulla are hormones that enter the blood stream
exert influence over cells throughout the body
ANS Control Systems:
neural circuits in brain-stem & spinal cord that regulate activity in pre-G neurons
ANS Autonomic Reflexes:
Afferent Limb: sensory neuron monitor tissues
Efferent Limb: mediated by sympathetic & parasympathetic division
ANS Autonomic Control Centers:
complex neural circuits, brain-stem and spinal cord
- selectively modify activity is specific pop of pre-G neurons
- coordinate more complex interactions in peripheral tissues
Pupillary Reflex:
stimulus: bright light -> reflex constriction of pupil in both eyes
Voiding Reflex:
stimulus: bladder filling -> reflex contraction of wall -> relaxation of internal sphincter -> bladder empties
Adrenergic Receptors:
receptors on the surface of cells that get activated when they bind a type of neurotransmitter called a catecholamine
Muscarinic Receptors:
recognize the neurotransmitter acetylcholine, translating this recognition into electrical transients and altered cell behavior by activating and suppressing an assortment of signaling pathways
