3 - Homeostasis - chapter 14 only Flashcards
what are the two subdivisions of the autonomic nervous system
sympathetic and parasympathetic
homeostasis
ability to regulate stable internal conditions despite external changes
negative feedback loop consists of?
stimulus, sensor, control and effector & then it loops
autonomic nervous system consists of motor neurons that:
- innervate smooth muscle, cardiac muscle and glands
- make adjustments for optimal support of body activities (e.g. increased respiration for running)
- operate via subconscious control
What are other names for autonomic nervous system?
Involuntary nervous system or general visceral motor system
ANS is the involuntary branch of what PNS branch?
motor (efferent)
what are the two divisions of the motor efferent PNS
Somatic NS and Autonomic NS
what are the 3 essential characteristics of homeostatic control
receptor, control centre and effector
receptor function
senses change (stimulus & receptor) and sends into (afferent pathway)
control centre function
determine set point for variable maintenance by analyzing info and determining correct response
effector function
provides means for response feedback (output along efferent pathway) and allows for regulation within a range/enhanced response
Examples of functions ANS can do
- delivers blood to more in need areas
- controls heart and respiratory rate
- adjusts blood pressure and body temperatures
- increase/decease gastric secretions
what is the somatic nervous system cell body in the CNS?
a single, thick myelinated group A axon that extends from spinal or cranial nerves directly to skeletal muscle - rapid conduction with no ganglia
Autonomic NS efferent pathway consists of two-neutron chain, what is each neuron called?
preganglionic neuron and postganglionic neuron
preganglionic neuron description
thin and lightly myelinated preganglionic axon that extends to autonomic ganglion
postganglionic neuron (outside CNS) description
unmyelinated postganglionic axon that extends to effector organ
how does the the preganglionic neuron communicate to the postganglionic neuron?
at the autonomic ganglion, postganglionic neuron synapses with preganglionic axon
afferent pathway
effector organ towards brain
efferent pathway
brain towards effector organ
autonomic ganglion defintion
sites where information (action potentials) coming from the central nervous system is transmitted to the periphery via synaptic neurotransmission.
what are the two neurotransmitters at the effector for the ANS? what fiber secretes which?
norepinephrine sympathetic fibers and acetylcholine parasympathetic fibers
what is the transmitter effect on the effector organ in ANS?
can be either stimulatory or inhibiting depending on the organ
conduction in the ANS is more —– compared to somatic NS. Why?
slow because the neurons are lightly or not myelinated at all
parasympathetic division function
‘rest & digest’ - promotes maintenance functions and converses body energy
“D” system
parasympathetic system - digestion, defecation and diuresis
sympathetic division function
fight or flight system - important during exercise - mobilizing the body during activity
“E” system
Exercise, excitement, emergency, embarrassment
Sympathetic (vasomotor) tone
state of partial vasoconstriction of the blood vessels maintained by sympathetic fibers
parasympathetic tone
normal (background) level of parasympathetic output; stains normal GI and urinary tract activity and lowers heart rate
what is the name of post ganglionic neurons swellings? What is its function?
varicosities; release neurotransmitter along the length of the axon
(general) three main anatomical differences between sympathetic and parasympathetic NS divisions
- sites or origin
- relative lengths of fibers
- location of ganglia
anatomical differences of parasympathetic NS compared to sympathetic NS
- fibers originate in brain stem or sacral spinal cord in PNS - fibers are in thoracic and lumbar spinal region SNS
- preganglionic fibers are long, postganglionic fibers are short PNS - reversed for SNS
- ganglia is near or within visceral effector organs PNS - ganglia are close to spinal cord SNS
vagus nerves account for what % of all preganglionic parasympathetic fibers in body
90%
Sacral part of parasympathetic division neurons are located and originated from which vertebrates? Which organs does it serve?
originates from neurons in S2-S4 and serves pelvic organs and distal half of large intestine
axons travel in ventral root of spinal nerves branch off to form?
pelvic splanchnic nerves
sacral part of PNS synapse with
- ganglia in pelvic floor
- intramural ganglia in walls of distal half of colon, urinary bladder, ureters and reproductive organs
- mostly controls sphincter function
inferior hypogastric [pelvic] plexus
ganglia located in pelvic floor
which Autonomic NS division has many cranial nerves?
parasympathetic
adrenergic fibers
fibers that release norepinephrine
cholinergic fibers
fibers that release acetylcholine
what brain regions communicate subconsciously with the hypothalamus (aka the integrated of the ANS)
cerebral cortex (frontal lobe) and limbic system (emotional input)
Describe the levels of control of the autonomic nervous system that are conscious in communication
1) hypothalamus
2) brain stem (reticular formation etc.)
3) spinal cord
Baroreflex function
to sense pressure changes by responding to change in the tension of the arterial wall.
what are Baroreceptors
mechanoreceptors located in the carotid sinus and in the aortic arch
3 levels of regulation of autonomic function
- brain stem & spinal cord controls
- hypothalamic controls
- cortical controls
importance of brain stem and spinal cord controls in ANS
- has direct effects on ANS-regulated activities
- motor centres are in ventro-lateral medulla
what regions of hypothalamus are the divisions of ANS associated with?
anterior regions = parasympathetic
posterior areas = sympathetic
the hypothalamus is considered what of the ANS?
integration centre since it contains centres of activities the ANS is responsible for
cortical controls
the normal regulation of an activity, such as movement of a limb, by the cerebral cortex.
3 diseases of homeostatic imbalances of ANS
hypertension, Raynaud’s disease, and autonomic dysreflexia
muscarinic receptors are found in
all effector cells stimulated by postganglionic cholinergic fibers
what is the effect of ACh at muscarinic receptors?
- can be inhibitory or excitatory
- effect depends on receptor type of target organ
one division usually predominates with P&S but in a few cases, the divisions have a ?
cooperative effect
both ANS divisions are partially active, resulting in a basal —– and —— ——–?
sympathetic and parasympathetic tone
action potentials continually firing down axons of both divisions produces a dynamic —— interaction which works to precisely control visceral activity
antagonistic
ANS is under control of CNS centres in what regions?
brain stem and spinal cord, hypothalamus and cerebral cortex
dorsal root ganglia is part of the —— division of the PNS
sensory
autonomic ganglis is a —– ganglia, containing the cell bodies of —– neurons
motor; motor
all somatic motor neurons release what neurotransmitter? what is always the effect of it?
acetylcholine; excitatory
dual innervation of the ANS
the two divisions counterbalance each other to keep the body systems running smoothly
degree of branching in preganglionic fibers in parasympathetic NS
minimal
degree of branching in preganglionic fibers in sympathetic NS
extensive
what neurotransmitters are used in parasympathetic pre-and post- ganglionic fibers
all pre and post fibers release ACh (cholinergic fibers)
what neurotransmitters are used in the pre- and postganglionic fibers of sympathetic NS?
all preganglionic fibers & the postganglionic fibers serving sweat glands release ACh —– the rest of postganglionic fibers release norepinephrine
craniosacral division is an alternate name for? and why?
parasympathetic division of ANS; because preganglionic fibers spring from opposite ends of CNS (brain & sacral)
parasympathetic preganglionic axons extend from CNS all the way up close to the ——- ——–
target organ
where is the terminal ganglia located in the parasympathetic NS
close or within target organ
what cranial nerve does preganglionic fibers of parasympathetic NS run in? And where are they located?
oculomotor, facial, glossopharyngeal and vagus (3,7,9,10); cell bodies lie in the brain stem in motor nuclei of the cranial nerve
How is the vagus nerve different in distribution of nerves compared to CN3, 7, 9?
its nerves are more widespread in the body, not just limited to the head
where are postganglionic fibre of parasympathetic NS?
not in CN, they latch onto branches of the trigeminal nerve for its wide spread distribution
nerve plexuses contain fibers from which ANS divisions
both sympathetic and parasympathetic
axons running from S2-S4 run in the ventral roots to the ventral rami to then branch off into —– —– nerves. These pass though the — —- plexus.
pelvic splanchnic; inferior hypogastric
why is sympathetic NS more anatomically complex than parasympathetic?
it innervates more organs
what superficial structures are only innervated by sympathetic nervous system
sweat glands (eccrine and apocrine), hair-raising arrector pili muscles of the skin and smooth muscle in the walls of all arteries and veins, superficial and deep
lateral horns are not located where? in what ANS division?
sacral region of spinal cord for parasympathetic NS
ganglia vary in size, position, and number but how many are there typically in each sympathetic trunk?
23
once a preganglionic axon reaches a trunk ganglion, where are the 3 locations synapses can occur? Pre and post ganglionic neurons can…
- synapse in trunk ganglion at the same level
- synapse in trunk ganglion at a higher or lower level
- pass through symplastic trunk to synapse in a collateral ganglion anterior to the vertebral column
sympathetic drink ganglia is in located where?
paired and beside spinal cord
collateral ganglia is what ANS division and location?
sympathetic NS and unpaired & anterior to the spinal cord
rami communicates are associated only with?
sympathetic NS
white rami communicantes carry what fibers to where and location found
preganglionic axons to sympathetic trunk; found only in T1-L2 cord segments
grey rami communicates carry what fibers and fibres from and to
postganglionic fibers headed for the periphery issue from every trunk ganglion from cervical to sacral region
what’s the purpose of grey rami communicates to grab information from the whole spinal cord?
to allow for sympathetic output to reach all body parts
function of visceral sensory neurons
send information about chemical changes, stretch, temperature and irritation of the viscera
where are visceral sensory neurons located?
dorsal root ganglia and sensory ganglia of cranial nerves
visceral reflex arcs have essentially the same components as somatic reflex arcs - receptor, sensory neuron, integration centre, motor neuron, and effector - what are the 3 key differences?
- visceral reflex has 2 consecutive neurons (pre/postganglionic) in its motor component
- afferent fibers are visceral. sensory neurons instead of somatic sensory neurons
- the effectors are smooth muscle, cardiac muscle and glands instead of skeletal muscles
what are the 3-neuron reflex arcs? What system do they make up?
sensory neurons, interneurons and motor neurons; enteric nervous system
what are the two types of ACh-binding receptors?
nicotinic receptors and muscarinic receptors
nicotinic receptors respond to
nicotine
muscarinic receptors are activated by
mushroom poison muscarine
when ACh binds to nicotinic receptors, the effect is always —– & how?
stimulatory by directly opening ion channels and depolarizing postsynaptic cell
nicotinic receptors are found where?
- all postganglionic neurons in both ANS divisions
- hormone-producing cells of adrenal medulla
- the sarcolemma of skeletal muscle cells at neuromuscular junctions (somatic targets)
muscarinic receptors are found
on all effector cells stimulated by postganglionic cholinergic fibers
what happens when ACh binds to a muscarinic receptor
effect is inhibitory or stimulatory - depending on the subclass of muscarinic receptor on the target organ
what are the two major lasses of adrenergic receptors?
alpha and beta
how is alpha and beta adrenergic receptors further classified?
alpha 1, alpha 2 - beta 1, beta 2, beta 3
organs that respond to norepinephrine or epinephrine have how many receptor subtypes?
more than one
NE or epinephrine can be either excitatory or inhibitory depending on?
the subclass of receptor predominating in the target organ
vasomotor fibers
sympathetic fibers that cause contraction of smooth muscle in walls of blood vessels; regulating blood vessel diameter
what glands does parasympathetic fibers not activate?
adrenal glands and sweat glands of the skin
what can override parasympathetic tone?
sympathetic nervous system and drugs
roles that sympathetic division is responsible for
- thermoregulatory responses to heat
- release of renin from the kidneys
- metabolic effects
what are some metabolic effects the sympathetic division can do that’s not reversible for the parasympathetic division ?
- increase metabolic rate of body cells
- raise blood glucose levels
- mobilize fats for use as fuels
sympathetic nerve impulses act briefly but the hormonal effects they provoke ——-; explains the widespread and prolonged effects of sympathetic activation
lingers longer
