What type of reflex involves skeletal muscle contraction?
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Somatic reflex.
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What type of reflex involves skeletal muscle contraction?
Somatic reflex.
What do alpha motor neurons innervate?
Extrafusal fibers.
What is the definition of the quasi-autonomous nervous system?
Almost autonomous; acts independently from sympathetic and parasympathetic nervous systems but can still be influenced by both.
What are the components of a reflex arc?
Stimulus, receptor, sensory neuron, interneuron, motor neuron, and effector.
What is the definition of a reflex?
A reflex is an automatic response to a stimulus.
What are varicosities in the context of the Parasympathetic Nervous System?
Round structures at the end of axons that release neurotransmitters.
What are the larger skeletal muscle fibers that provide most of the force during a contraction called?
Extrafusal fibers.
Where is the Golgi tendon organ located?
At the junction of the tendon and muscle fibers.
What happens when a baby is suspended in a prone position?
The head lifts up and the spine straightens, demonstrating the Landau reflex.
What is the 'Thoracolumbar outflow'?
It refers to the preganglionic fibers that leave the spinal cord between T1 to L2.
What is a reflex?
A relatively predictable, involuntary, and nearly instantaneous response to an eliciting stimulus.
How does fatigue affect the muscle spindle in the myotatic reflex?
Fatigue causes a slight bending of the knee, stretching the knee extensor muscle and increasing the length of the muscle fiber.
What is a monosynaptic reflex?
A reflex that involves a single synapse.
What enzyme combines choline with acetyl-CoA to synthesize Acetylcholine?
Choline acetyltransferase (ChAT).
What type of information do muscle sensory receptors send to the CNS?
Length of the muscle, tension of the muscle, and the rate of change in length/tension.
What is the role of the myenteric plexus?
Controls GI motility and movement of food from proximal to distal.
What is the effect of M2 and M4 muscarinic receptors?
They are inhibitory and decrease cAMP levels.
What type of synapses are involved in the inverse myotatic reflex?
Disynaptic synapses, first synapsing with an inhibitory neuron.
What is the effect of α1 receptors?
They cause constriction/contraction of smooth muscle by increasing IP3 and intracellular Ca+2.
What characterizes primitive reflexes?
They are present at birth, involuntary, and directed from the brainstem without cortical involvement.
What is the difference between innate and acquired reflexes?
Innate reflexes are present since birth and involuntary, while acquired reflexes are learned after birth and can be voluntary.
What do static responses in muscle spindles respond to?
The degree of stretching of the muscle spindle.
What is the role of the muscle spindle and GTO in maintaining posture during fatigue?
They work together to oppose the decrease in contraction of the rectus femoris due to fatigue.
What is an example of an innate reflex?
Myotatic/stretch reflex.
What is the role of the Golgi tendon organ in the inverse myotatic reflex?
It causes relaxation of the muscle in response to increased tension.
What occurs when a baby's head is lowered towards the surface while in a prone position?
The hands and legs extend in a protective fashion, demonstrating the Positive Support Reflex.
What neurotransmitter is associated with the parasympathetic nervous system?
Acetylcholine (Ach).
What is the role of the sympathetic nervous system?
Responsible for the fight or flight response.
What is afterdischarge in the context of reflexes?
A repetitive firing of excited neurons after the cessation of the stimulus.
What are postural reflexes?
Reflexes that keep our body upright and aligned, such as righting, parachute, and tonic neck reflexes.
What are the functional components of a typical reflex arc?
Receptor, sensory neuron, interneuron, motor neuron, and effector.
Where does the enteric nervous system begin and end?
From the esophagus until the anus.
What is the role of muscle spindles?
They sense muscle length and the rate of change of length.
What are the two parts of the intramural plexus?
Myenteric Plexus and Submucosal Plexus.
What is the response of the flexor withdrawal reflex?
Contraction of flexion muscles to remove the foot from the stimulus.
What triggers the dynamic stretch reflex?
Sudden rapid stretch of muscle fibers.
What type of intrafusal fiber senses sustained stretch?
Nuclear chain fiber.
What is the role of the sympathetic chain of ganglia?
It allows preganglionic fibers to synapse with postganglionic neurons at the same level or travel to other ganglia.
What is the function of acetylcholinesterase (AchE)?
It breaks down acetylcholine in the synaptic cleft.
What does the parasympathetic nervous system regulate?
Energy conservation and maintenance of vital body functions.
What is the thoracolumbar outflow associated with?
The sympathetic nervous system.
What neurotransmitters are secreted by the Sympathetic Nervous System?
Norepinephrine and epinephrine (80% of norepinephrine is converted to epinephrine in the adrenal medulla).
What happens during the contraction followed by relaxation of a muscle?
The muscle shortens due to leg extension, causing the muscle spindle to become lax, stopping excitatory discharge and leading to muscle relaxation.
What is activated during fatigue to maintain muscle contraction?
The myotatic reflex is activated, exciting the α motor neuron of the homonymous muscle (rectus femoris).
What are the four layers of the bowel wall?
Mucosa, Submucosa, Muscularis Propria, and Serosa.
What happens when Gq receptors stimulate Phospholipase C?
It converts PIP2 to IP3 and DAG, increasing intracellular Ca+2 levels and causing contraction of smooth muscle.
What is the function of the myotatic/stretch reflex?
Maintenance of posture and overcoming unexpected impediments during voluntary movement.
What distinguishes the length of preganglionic and postganglionic fibers in the Parasympathetic Nervous System?
Preganglionic fibers are long, while postganglionic fibers are short.
How does norepinephrine affect alpha and beta receptors?
Norepinephrine has a greater effect on alpha receptors compared to beta receptors (α > β).
What neurotransmitter is secreted by sympathetic postganglionic fibers?
Norepinephrine.
What does a visceral reflex involve?
Glandular or non-skeletal muscular responses, including smooth muscles like the heart and blood vessels.
Where are Alpha-1 adrenergic receptors primarily found?
On postsynaptic effector cells, mainly in smooth muscle.
What is the function of Beta-1 adrenergic receptors?
They are primarily found in the heart and are responsible for increasing heart rate and contractility.
Give an example of a somatic reflex.
Knee jerk reflex.
What distinguishes the Somatic Nervous System from the Autonomic Nervous System?
The Somatic Nervous System is voluntary with a single neuron from the CNS to effector organs, while the Autonomic Nervous System is involuntary with a two-neuron chain.
What happens during the Moro or startle reflex?
When the baby is abruptly lowered, the arms stretch out, hands open, and legs flex.
What is the function of the reflex arc?
It serves as the basic circuitry that underlies a reflex.
What does the enteric nervous system control?
The gastrointestinal tract.
What is the rate-limiting step in the synthesis of Acetylcholine?
The entrance of choline through the sodium-coupled choline transporter.
What is the characteristic of postganglionic fibers in the sympathetic nervous system?
They are long.
How is Acetylcholine stored in the nerve terminal?
Inside vesicles via the vesicle-associated transporter (VAT).
What is the enteric nervous system?
A part of the peripheral nervous system that governs the function of the gastrointestinal system.
What happens when a stimulus is sensed by the pain receptors in the right foot?
The signal travels to sensory neurons, enters the spinal cord, and causes flexion of that foot while also sending a signal to the opposite leg to extend it.
What is the purpose of the crossed extensor reflex?
To extend the opposite limb to support the body once the affected limb is withdrawn.
What happens when a baby is lowered until its feet touch a flat surface?
The pressure on the foot pads causes the limbs to extend.
What is the effect of α2 receptors?
They inhibit norepinephrine release from presynaptic receptors and cause dilation/relaxation by decreasing cAMP.
What are adrenergic medications?
Drugs that stimulate the sympathetic nervous system.
What is the distribution of the sympathetic nervous system?
It is diversely distributed to the eyes, heart, lungs, GI tract, and reproductive organs.
What type of neurons are both preganglionic neurons in the autonomic nervous system?
Cholinergic.
What are the two divisions of the Autonomic Nervous System?
Sympathetic and Parasympathetic.
What is the exception regarding postganglionic neurons in the sympathetic nervous system?
Eccrine sweat glands and some blood vessels have muscarinic receptors.
What type of response do dynamic gamma fibers primarily excite?
Nuclear bag muscle fibers.
What effect does SERCA inhibition have on cardiac myocytes?
It increases Ca+2 levels in the cytoplasm, leading to action potential and increased heart rate, inotropy, and AV conduction.
What is the role of somatic motor neurons?
They transmit signals from the central nervous system to skeletal muscles.
What distinguishes the sympathetic nervous system from the parasympathetic nervous system?
Sympathetic prepares the body for 'fight or flight', while parasympathetic promotes 'rest and digest'.
What is the primary effect of M1 and M3 muscarinic receptors?
They are excitatory and increase IP3 and intracellular Ca+2 levels.
What is the number of synapses involved in the flexor withdrawal reflex?
Polysynaptic, due to the complexity of their circuitry.
What reflexes are part of the reflexes of posture?
Positive support reflex and Stepping reflex.
Which cranial nerves synapse with cranial ganglia before reaching their target organs?
Cranial nerves III, VII, and IX.
What is the rate-limiting step in the synthesis of Norepinephrine?
The conversion of Tyrosine to Dopa by the enzyme tyrosine hydroxylase.
What types of stimuli do visceral reflexes detect?
Stretch, blood chemicals, temperature changes, and other internal stimuli.
What are some examples of visceral reflexes?
Sneezing, coughing, micturition, pupillary reflex, vomiting, swallowing, and some sexual reflexes.
What is the sympathetic response of the eyes mediated by α1 receptors?
Contracts meridional fibers, leading to pupil dilation (mydriasis).
What is the palmar grasp reflex?
When a finger is placed in a baby's hand, it causes the flexing of the fingers.
What type of receptors do norepinephrine and epinephrine bind to?
Adrenergic receptors (alpha or beta).
What happens when a ligand binds to a G protein coupled receptor?
It causes a conformational change and activates the G protein, converting GDP to GTP.
What happens to the negative feedback mechanism during muscle fatigue?
There will be no negative feedback mechanism, helping to reverse the decrease in force caused by fatigue.
What surrounds and is attached to intrafusal muscle fibers?
Sensory receptors.
What is a jerk movement in the context of muscle reflexes?
A sudden contraction followed by relaxation.
What stimulates the nuclear chain fiber in a maintained stretch of the muscle?
A maintained stretch, such as standing up.
What is the primary location of Beta-3 receptors?
Mainly found in brown fats, but also present in the heart and urinary bladder wall.
What effect does epinephrine have on alpha and beta receptors?
Epinephrine has an equal effect on both alpha and beta receptors (α = β).
What is the difference between spinal and cranial reflexes?
Spinal reflexes are processed in the spinal cord, while cranial reflexes are processed in the brain.
What sensory fibers are involved in the dynamic stretch reflex?
Type 1a sensory nerve fibers.
What is the Stepping Reflex?
When a baby is held upright with one foot touching the surface, the hip and knee of that foot flex while the other foot steps forward.
What neurotransmitter do all preganglionic fibers secrete in the autonomic nervous system?
Acetylcholine.
What is the effect of β2 receptors on smooth muscle?
They cause relaxation by increasing cAMP.
What type of muscles are involved in visceral reflexes?
Glandular and non-skeletal muscles.
What occurs during the rooting reflex?
If the perioral skin is stroked, the mouth opens, and the baby's head turns towards the stimulated side.
What are the two types of cholinergic receptors?
Nicotinic and Muscarinic.
What neurotransmitter does the Parasympathetic Nervous System secrete?
Acetylcholine.
What are the two main types of reflexes?
Somatic and visceral reflexes.
How does PKA affect smooth muscle in the GIT and bronchus?
PKA inhibits Phospholipase C, resulting in inhibitory effects on smooth muscle.
What type of reflex is the flexor withdrawal reflex?
It is a nociceptive or pain reflex.
What is the mnemonic to remember the cranial nerves associated with the Parasympathetic Nervous System?
How does the inverse myotatic reflex help in muscle tension control?
It acts as a negative feedback mechanism to oppose changes in muscle tension.
What happens to preganglionic fibers after they exit the spinal cord?
They enter the white ramus and reach the paravertebral sympathetic chain of ganglia.
What is the purpose of the reflex that causes the opposite leg to extend when one foot is flexed?
It is important for balance, allowing the other foot to support the body.
What are the two types of adrenergic receptors?
Alpha-receptors and Beta-receptors.
What happens when the patellar tendon is tapped?
It causes rapid stretch of the rectus femoris muscle, leading to a knee-jerk reflex.
What is the function of Renshaw cells?
Lateral inhibition to sharpen motor signals.
What is the righting reflex?
A reflex that helps correct the position of the body when it goes off balance.
What is the parasympathetic response of the eyes mediated by M3 receptors?
Contracts circular fibers, leading to pupil constriction (miosis).
What is the Enteric Nervous System?
The own nervous system of the gastrointestinal tract that can operate independently from the brain and spinal cord.
What type of channels do nicotinic receptors represent?
Ligand-gated ion channels.
What type of reflex is characterized by direct synapsing to the α motor neuron without interneurons?
Monosynaptic reflex.
What is the role of proprioceptors in somatic reflexes?
They monitor the position of limbs, body movement, and tension in the musculoskeletal system.
What is the origin of the preganglionic neurons in the Parasympathetic Nervous System?
They originate from the intermediolateral horns of the sacral nerves S2 to S4 and the brainstem.
What does the Golgi tendon organ sense?
Tendon tension and rate of change of tension.
What type of intrafusal fiber senses the onset of stretch?
Nuclear bag muscle fiber.
What happens to Acetylcholine after it binds to cholinergic receptors?
It dissociates and is broken down by Acetylcholinesterase.
How many neuron chains are in the efferent limb of the ANS?
Two neuron chains from the CNS to effector organs.
How does the crossed extensor reflex relate to the flexor reflex?
They work hand-in-hand to maintain balance and support during withdrawal.
What is the importance of the inverse myotatic reflex?
It helps control muscle tension, regulates muscle force, and prevents excessive tension on muscles and tendons.
What physiological response do β1 receptors mediate?
They increase cAMP, leading to excitatory effects in the heart, lipocytes, and brain.
What do anterior motor neurons directly innervate?
Skeletal muscle fibers.
What is unique about the adrenal medulla in relation to postganglionic fibers?
It does not have postganglionic fibers.
Give an example of a visceral reflex.
Pupillary light reflex.
What is the inner part of the spinal cord referred to as?
Gray matter (butterfly-shaped).
What are the origins of the preganglionic fibers in the sympathetic nervous system?
They originate from the thoracic and lumbar regions.
Where are Beta-2 receptors primarily found?
In postsynaptic effector cells, specifically in bronchial, GI, uterus, urinary bladder wall, and cardiac muscle.
Where do the long preganglionic fibers of the parasympathetic nervous system originate?
From the brainstem and sacral part of the spinal cord.
What triggers the release of Acetylcholine from vesicles?
The entry of calcium ions when an action potential reaches the nerve terminal.
What is the function of the submucosal plexus?
Regulates fluid homeostasis, including absorption or secretion of water and electrolytes.
What is the physiological response of the knee-jerk reflex?
Extension of the leg (jerky movement).
What is the primary afferent ending in intrafusal fibers?
Annulospiral ending.
What is the primary nerve responsible for the majority of parasympathetic nerve fibers?
The vagus nerve (CN X).
What happens to Norepinephrine after it is released?
It can be reuptaken, diffuse away, or be broken down by enzymes.
What are cholinergic medications?
Drugs that stimulate the parasympathetic nervous system.
What cues are involved in the righting reflex?
Optic cues (eyes), labyrinth cues (ears for equilibrium), and head orientation relative to the neck, thorax, and pelvis.
What do gamma motor neurons innervate?
Intrafusal fibers.
What are the types of nerve roots in the spinal cord?
8 Cervical, 12 Thoracic, 5 Lumbar, 5 Sacral, 1 Coccygeal.
What effect does the Gs receptor have on cardiac myocytes?
It activates the L-type Ca²⁺ channel, allowing Ca²⁺ to enter the cells.
What neurotransmitter is associated with the sympathetic nervous system?
Norepinephrine (NE).
What is the role of nicotinic receptors in autonomic ganglia?
They open Na+ and K+ channels, leading to excitatory effects and cell depolarization.
What happens to the α motor neuron during muscle fatigue in the context of the Golgi tendon organ?
The Golgi tendon organ enhances the excitability of the α motor neuron going to the rectus femoris.
What type of fiber is the primary afferent ending?
Type 1a fiber.
What is the function of the adrenal medulla in the autonomic nervous system?
It serves as a special postganglionic neuron that secretes hormones into the bloodstream.
What type of receptors are found at the ganglia of the autonomic nervous system?
Cholinergic receptors, specifically nicotinic.
Why are primitive reflexes important?
They are necessary for newborn survival and development.
What type of receptor does acetylcholine bind to in the parasympathetic nervous system?
Muscarinic receptor.
What is the outer part of the spinal cord called?
White matter.
What is an exemption in the sympathetic nervous system regarding the adrenal medulla?
The adrenal medulla does not have a postganglionic nerve fiber and secretes epinephrine and norepinephrine directly into the bloodstream.
What type of muscles are involved in somatic reflexes?
Skeletal muscles.
What is the efferent pathway for somatic reflexes?
1 nerve fiber.
What are the two types of anterior motor neurons?
Alpha motor neurons and gamma motor neurons.
What is the efferent pathway for visceral reflexes?
2 nerve fibers (preganglionic and postganglionic).
What is the asymmetric tonic neck reflex?
When the baby's head is turned to one side, the arm and leg on that side extend while the opposite side flexes.
What is the role of cAMP in the signaling pathway?
It activates protein kinase A, leading to various cellular effects.
What neurotransmitter is secreted by postganglionic fibers in the parasympathetic nervous system?
Acetylcholine.
Where does the spinal cord lie?
Inside the spinal column of the vertebrae.
What is the flow of sensory information in the spinal cord?
Ascending Pathway from peripheral receptors to the dorsal nerve root.
What neurotransmitters are secreted by postganglionic fibers in the sympathetic nervous system?
Norepinephrine and epinephrine.
What resides in the ventral horn of the spinal cord?
Motor neurons.
What are G-Protein Coupled Receptors (GPCRs) associated with?
Muscarinic receptors.
