Autonomic, Smooth, Skeletal Muscle Flashcards
What are the two anatomical divisions of the nervous system? What are the divisions composed of?
Central Nervous system (CNS) and Peripheral Nervous System (PNS)
CNS- composed of brain and spinal cord
PNS- includes neurons outside CNS.
What are the divisions that stem from Peripheral Nervous System? How do these divisions compare?
PNS can be divided into Afferent and Efferent divisions.
Afferent- signal towards brain in CNS. receive info from sensory organ to transmit towards CNS (ex: sight from eyes, tell brain you saw a dog in movie)
Efferent- signals away from CNS. go from CNS to PNS (ex: brain tells you to lift water bottle )
What divisions can Efferent portion of PNS be divided into?
What can autonomic part of PNS divide into? provide an example of this.
Efferent part of PNS:
1. Somatic efferent- VOLUNTARY activity
ex: contraction of muscles
2. Autonomic nervous system- INVOLUNTARY activity (we cannot control this), to control/regulate everyday needs and requirement of body; without CONSCIOUS participation from brain
Autonomic part of efferent PNS divide into sympathetic (fight/flight response) like skeletal muscle or Parasympathetic- rest/digest; seen in smooth muscle
Describe the synaptic mechanism in somatic nervous system, including the neurotransmitter and receptor used.
neurons at preganglionic fiber will release neurotransmitter Acetylcholine to activate NICOTINIC receptors for skeletal muscle. (Ach connects CNS to effector organ)
Describe the synaptic mechanism in an autonomic nervous system, including the neurotransmitter and receptor used.
Autonomic nervous system has divisions:
Sympathetic Nervous System: start with cell nuclei at preganglionic fiber than reach synapse and post ganglion fiber to meet target organ
in sympathetic: preganglionic fiber will use Ach (using nicotinic receptors) to connect CNS to ganglia, and in postganglionic fiber, NOREPINEPHRINE is used to connect ganglia to effector organ for SKELETAL muscle, using ALPHA or BETA receptors.
Sympathetic: ACH in preganglionic (nicotinic receptors) connect CNS to ganglia and EPINEPHRINE connect ganglia to effector organ for SMOOTH and CARDIAC muscle and ADRENAL gland.
Parasympathetic Nervous System: start with cell nuclei axon goes through .
In parasympathetic: preganglionic fibers: ACH used connect CNS to ganglia using nicotinic receptors and post ganglionic fibers use ACH to connect ganglia to effector organ in SKELETAL muscle using muscarinic receptors.
differentiate between the preganglionic and postganglionic fibers.
How do these fibers differ in length for parasympathetic vs sympathetic nervous system?
Preganglionic- neuron fibers connect CNS to ganglia
Postganglionic- neuron fibers connect ganglia to effector organ.
In sympathetic- Short preganglionic fibers, long post-ganglionic fibers
In parasympathetic- long preganglionic fibers and short post-ganglionic fibers.
What makes sympathetic nervous system different in adrenal glands?
The sympathetic nervous system has NO postganglionic fiber for adrenal glands, and uses epinephrine.
What is the parasympathetic nervous system also known as?
What kinds of nerves are part of the parasympathetic nervous system and distinguish where these nerves synapse at?
Parasympathetic nervous system aka CRANIAL SACRAL Nervous system.
cell nuclei of parasympathetic come from brain stem (cranial) and in sacrum
Cranial nerves 3, 7, 9 and 10
and Sacral nerves, S2, S3, and S4.
Cranial nerve 3- OCULOMOTOR synapse to EYE and carries parasympathetic fibers for synapses at CILIARY ganglia
Cranial nerve 7- FACIAL nerve synapses with parasymp to synapse at PTERYGOPALATINE and SUBMANDIBULAR
Cranial nerve 9- GLOSSOPHARYNGEAL synapse at OTIC ganglia
Cranial nerve 10- LARGEST cranial nerve in body, many outputs to many organs like the lungs, heart, liver, pancreas, stomach, intestine.
Sacral nerves: S2 S3 and S4 will stimulate Genital nervous system like bladder.
List the general functions or characteristics of Autonomic Nervous System.
1) to preserve homeostasis (parasymapthetic) and provoke reactions to protect the individual (Sympathetic)
2) afferent impulses from the viscera elicit reflex responses which generally cannot be controlled voluntarily.
3) Many fibers of the ANS are always active maintaining a basal tone in most organs (ex: a certain level of constriction of blood vessel by the sympathetic NS. A certain level of parasympathetic tone in the G.I. Tract.
4) Sympathetic and Parasympathetic nervous systems are generally antagonistic (ex: G.I. Tract, glucose control), but there are exceptions (ex: salivary glands, where both para and sympathetic stimulate secretion).
5) Activation of sympathetic nervous system is generally associated with defense mechanisms involving expenditure of energy, glycogenolysis, increased muscle tone, etc.
6) Activation of parasympathetic system- associated with conservative and restorative processes; decrease in blood pressure and body temperature.
Describe the motor efferents of parasympathetic Nervous system, including where these nerves are located.
The cranio-sacral motor division: the cells of origin for preganglionic fibers are located at 3 levels in CNS midbrain, medulla and sacral spinal cord.
Midbrain: Cranial nerve 3; from the Edinger-Westphal nucleus, preganglionic fibers go to the ciliary ganglion from where short postganglionic fibers go to terminate in the pupil and ciliary muscle.
Medulla or Bulbar outflow: Through facial, glossopharyngeal and vagus (7, 9, 10 cranial nerves)
-facial nerve: from superior salivary nucleus, preganglionic fibers going wit facial nerve go either to submandibular ganglion and via postganglionic fibers to innervate submaxillary and submandibular glands., or Pterygopalatine ganglions (post) which sends postganglionic fibers to lacrimal glands.
Glossopharyngeal nerve (9): from inferior salivary nucleus, preganglionic fibers go to otic ganglion and form here postganglionic fibers go to parotid gland
Vagus nerve- from the dorsal motor nucleus of vagus, preganglionic fibers go directly to thoracic and abdominal viscera. Postganglionic cells are located within the innervated organ.
The intermediolateral nuclei of S2-S4 sacral segments of spinal cord project to genitourinary organs and distal colon
Describe the different ways preganglionic fibers of Sympathetic system can pursue?
Cells of origin of preganglionic fibers are located in the lateral horns of the spinal cord (intermediolateral column) from 1st thoracic to the 2nd or 3rd lumbar segments.
A preganglionic fiber may pursue one of 3 courses after entering the ganglion through the ventral motor roots and white ramus:
A) can go to ganglion in the PARAVERTEBRAL sympathetic ganglionic chain at the SAME level of the chain, or go caudally or rostrally (can go down a level or up at higher position in chain) in the sympathetic chain before synapsing with a ganglionic cell.
B) Can BYPASS a paravertebral ganglion and synapse with a ganglionic neuron cell at an outlying sympathetic ganglion (PREVERTEBRAL or terminal ganglion).
C) Can directly innervate SECRETORY cells of the ADRENAL MEDULLA. The secretory cells (chromaffin cells) can secrete norepinephrine and epinephrine on sympathetic stimulation.
after synapse, post ganglion fiber go to target fiber (for prevertebral)
what are the 3 prevertebral ganglia for sympathetic nervous system?
Celiac, superior mesentery and and inferior mesentary
Describe the chemical transmission of nerve impulses and how a neuron is useful
Each neuron is a separate anatomic unit with no structural continuity between the units. Thus communication between the neurons is through release of chemical molecules called Neurotransmitters.
What are the two major Neurotransmitters in the Autonomic Nervous System and how do they aid in nerve transmission?
2 major neurotransmitters in ANS:
- Acetylcholine (ACh): ACh mediates all transmission of nerve impulses across autonomic ganglia in both sympathetic and parasympathetic nervous systems. Transmission from the autonomic postganglionic nerves to effector organs in parasympathetic system also involves release of ACh.
2) Norepinephrine and Epinephrine: in the sympathetic mediates transmission nerve impulses from autonomic postganglionic nerves to effector organs.
Explain the whole process of cholinergic transmission.
Cholinergic transmission:
1. Synthesis of ACh: choline is transported from extracellular fluid into the cytoplasm of the cholinergic neuron by a carrier system that cotransports sodium and is inhibited by the drug, hemicholinum.
Choline reacts enzymatically with acetyl CoA to form acetylcholine
2. Storage of ACh: once synthesized, ACh is transported into synaptic vesicles where it is stored in granules
3. Release of ACh: when an action potential arrives at nerve ending, voltage-sensitive calcium channels in the presynaptic membrane open, causing an increase in concentration of intracellular calcium.
Elevated Ca+ promotes the fusion of synaptic vesicles within the cell membrane and release ACh into synapse.
4. Binding to receptor: ACh released from the synaptic vesicles bind to two different types of receptors: Nicotinic receptors or Muscarinic receptors.
Nicotinic receptors are found in all autonomic ganglia. Muscarinic receptors are found in cells of EFFECTOR organs.
5. Degradation of ACh: ACh is rapidly cleaved by acetylcholinesterase into choline and acetate.
6. Recycling of Choline: Choline may be recaptured by a high affinity transport system that pulls the molecule back into the neuron.
Discuss what occurs during the synthesis and release of Acetylcholine from parasympathetic nerve ending.
Discuss what occurs during the synthesis and release of norepinephrine from storage vesicles in SYMPATHETIC nerve endings
Synthesis and release of NE from vesicles in Sympathetic:
- Tyrosine is transported into the cytoplasm of the adrenergic neuron (Beta?), where the amino acid is hydroxylated to Dopa, by tyrosine-hydroxylase.
- Dopa is decarboxylated to form Dopamine
- once formed, Dopamine is transported into synaptic vesicles using an amine transporter.
- Dopamine is then hydroxylated to form Norepinephrine
- In adrenal medulla NE is methylated to form Epinephrine
- When an action potential arrives at the nerve terminal, this triggers an influx of Calcium ions from the extracellular fluid into the cytoplasm of the neuron. This causes the synaptic vesicles to release their contents into the synapse
- NE in the synapse is active for only a few msec. Ne binds to different adrenergic membrane receptors. its action is terminated by rapid reuptake, oxidation and by an enzyme: catechol-o-methyl transferase (COMT) present in the presynaptic membrane.
Explain how secondary messenger systems work
Secondary messenger molecules are produced in response to neurotransmitter binding to receptor, and translate the extracellular signal into response within the cell.
What is a neurotransmitter?
A neurotransmitter can be thought of a signal, and a receptor as a signal detector and transducer.
What are the two types of Cholinoreceptors in ANS? What are the two types of adrenergic receptors, and how do these receptors dffer when bound to neurotransmitters?
2 types of Cholinoreceptors in ANS:
NICOTINIC and MUSCARINIC
2 major adrenergic receptors:
1. Alpha (alpha 1 and alpha 2)
2. Beta (beta 1 and beta 2)
The receptors when bound to neurotransmitter activate different intracellular cell signals:
1. Direct regulation of ionic permeability: Nicotinic receptors are linked to membrane ion channels and directly alters ion permeability.
2. Regulation involving 2nd messenger molecules: the coupling of the muscarinic or adrenergic receptors to specific G-protein produces specific intracellular signals which in turn produces their specific effects on different organs.
What class of compounds does Epinephrine belong to?
Epinephrine belongs to a class of compounds known as catecholamines.
Describe the structural differences between smooth and skeletal muscle fibers and indicate the
structural similarities with respect to contractile units.
a
Describe the distinguishing characteristics of multi-unit and single-unit smooth muscles.
a
What are the functional uses of hypothalamic and brain stem centers?
Centers in various parts of the brain coordinate autonomic regulation of organ systems functions.
These systems include: Temperature regulation, thirst food intake, micturition (urination) , breathing and cardiovascular function.
What is the purpose of sensory neurons? Are they considered to be part of the Autonomic Nervous System?
Sensory neurons that are innervating involuntary organs are NOT considered part of ANS, but sensory input is important for autonomic function.
Ex:
1. sensory information concerning blood oxygen or CO2 levels is sensed by carotid bodies and is transmitted via cranial nerve 9
2. Baroreceptors in carotid sinus can send information to tractus solitaries in vasomotor center in medulla, which can then coordinate autonomic blood pressure regulation
3. Sensory innervation to visceral organs, blood vessels and skin forms afferent limb of autonomic reflexes.
*Diagram the intracellular pathways that control contraction and relaxation in smooth muscle
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*Explain how smooth muscle can develop and maintain force with a much lower rate of ATP
hydrolysis than skeletal muscle
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*Describe the mechanisms by which the smooth muscle cell can increase and decrease
intracellular calcium concentration
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*Describe the distinguishing characteristics of multi-unit and single-unit smooth muscles.
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*Describe the structural differences between smooth and skeletal muscle fibers and indicate the
structural similarities with respect to contractile units.
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*Draw and label a skeletal muscle at all anatomical levels, from the whole muscle to the
molecular components of the sarcomere. At the sarcomere level, include two different stages
of myofilament overlap
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*List the steps in excitation-contraction coupling in skeletal muscle, and describe the roles
of the sarcolemma, transverse tubules, sarcoplasmic reticulum, dihydropyridine receptors,
ryanodine receptors, and Ca2
Excitation-contraction coupling:
- ACH released from axon terminal binds to ACh receptor on the sarcolemma
- An action potential is then generated and travels down the T-tubule
- The spread of AP down T-tubules activates DHPR (dihydropyridine) receptors.
- DHPR (voltage SENSOR) sense change in membrane potential and changes its position (twists sideways) to become closer to RyR receptor.
- RYR receptor (ryanodine receptor) is now in close contact with DHPR and allows for Sarcoplasmic reticulum to release calcium (previously stored) in to cell due to change in voltage
*Describe the roles of ATP in skeletal muscle contraction and relaxation
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*Distinguish between an endplate potential and an action potential in skeletal muscle.
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*Compare a neuromuscular junction and chemical synapse between two neurons.
Similarities between Synapse and NMJ:
- 2 excitable cells separated by narrow cleft that prevents direct transmission of electrical activity
-Axon terminals store NT that are released by Calcium induced Exocytosis of storage vesicles
-binding of NT with receptor that opens membrane channels, permitting ionic movements that cause Change in Membrane potential.
Resultant change in MP is GRADED Potential (short distance signals)
Differences:
Synapse is a junction between TWO NEURONS
NMJ exists between a MOTOR neuron and a skeletal MUSCLE fiber.
- Synapse are always Excitatory (EPP) end plate potential
-NMJ are EXCITATORY (EPSP) post synaptic potential, or INHBITORY (IPSP)
*List some possible agents that affect neuromuscular transmission in skeletal muscle and the
mechanisms of action.
- Alters release of ACh:
- Black widow spider venom- Explosive release of Ach; toxin can form pores in presynaptic membrane (excessive muscle contraction will occur, but NOT relaxation)
- Clostridium botulinum toxin- blocks release of ACh: prevents contraction. This is used as a medicine (BOTOX) to treat chronic back pain due to muscle spasms. - Blocks ACh Receptor:
-Curare - reversibly binds to ACh receptor (NO contraction occurs). Derivatives of curare used to relax skeletal muscles during surgery.
-Myasthemia Gravis-
autoimmune condition in which antibodies inactivate ACh receptor (antibodies destroy communication between nerve and muscle).
-Drug called NEOSTIGmine - short term Anti ACHase (prevents the enzyme from breaking down ACh into choline and acetic acid), increase likelihood of contraction (more ACh available) - Prevents Inactivation of ACh:
- Organophosphates (certain pesticides and nerve gases) - irreversibly inhibits AChase (causes contraction ) as Diaphragm unable to repolarize.
*Distinguish between an isometric and isotonic contraction
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*Distinguish between a twitch and tetanus in skeletal muscle and explain why a twitch is
smaller in amplitude than tetanus
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*List the energy sources of muscle contraction and rank the sources with respect to their
relative speed and capacity to supply ATP for contraction.
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*Compare the structural, enzymatic, and functional features of the 3 major fiber types of
skeletal muscle
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*Define a motor unit and describe the order of recruitment of motor units during skeletal
muscle contraction of varying strengths
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*Discuss the two major ways to increase whole muscle force development. Provide examples
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*Describe potential mechanisms that may contribute to sarcopenia.
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*What is the neurotransmitter and receptor for postganglionic fibers vs preganglionic fibers in sympathetic and parasympathetic? Which receptor is used for all ganglia in parasympathetic and sympathetic in ANS?
Postganglionic fibers:
neurotransmitter- Norepinephrine for sympathetic
receptor: alpha, beta receptors (adrenergic)
Preganglionic fibers of autonomic NS:
release neurotransmitter ACh for both sympathetic and parasympathetic.
Receptor for postganglionic parasympathetic- muscuranic
ALL ganglia on autonomic NS (both sympathetic and parasympathetic) use Nicotinic receptors
Epinephrine is not used for sympathetic (it is for smooth, cardiac muscle, gland, w/o postganglionic fiber)
*What happens to pupils if you overdose on Heroin? Overdose on Cocaine?
if you overdose on Heroin- pupils will constrict
overdose on Cocaine: pupils will DILATE, as cocaine will stimulate alpha receptor and affect peripheral nervous system . There will be less uptake of norepinephrine.
*What happens when there is too much ACh being released? What enzyme can help with this issue?
When there is too much ACh, causing constant release of it into synapse; there will be medical issues.
enzyme Acetylcholinesterase will break ACh down into Choline and Acetate.
*What is the one exception for what receptor is used and neurotransmitter released in sweat glands?
Exception:
Sweat glands have sympathetic control; receptor: muscarinic and neurotransmitter released is Acetylcholine (NOT norepinephrine)
Compare and contrast what happens in sympathetic vs parasympathetic for Pupils. Male genitalia? Bladder?
EYE: Sympathetic: pupils DILATE Parasympathetic: pupils constrict Male genitalia: sympathetic- controls EJACULATION parasympathetic- controls erection Bladder: sympathetic: relax wall of bladder, prevent you from urinating parasympathetic- relaxation of sphincter, CONTRACT bladder (allow you to pee)
Compare and contrast what happens in sympathetic vs parasympathetic for Heart, Vascular smooth muscle, bronicholes/lungs, and Liver.
- Heart:
sympathetic- stimulate heart, increase heart rate (B1 receptor)
parasympathetic- Decrease heart rate (M receptor) - Vascular smooth muscle (blood vessels) are SYMPATHETIC for skin and skeletal muscle
Skin (splanchnic)- Constricts (alpha 1 receptor)
Skeletal muscle- DILATES (B2 receptor)
Skeletal muscle- constrict (Alpha 1 receptor)
Endothelium controlled by PARASYMPTHETIC:
releases EDRF (endocyte releasing factor) using M receptor. - Bronchioles:
sympathetic - DILATES (B2 receptor)
parasympathetic- constrict (M receptor) - Liver: controlled by SYMPATHETIC; stimulate gluconeogenesis, glycogenolysis (alpha, B2 receptor)
