Exam 2 Flashcards
The autonomic nervous system is part of the nervous system and is
composed of the Sympathetic and the Parasympathetic systems.
The autonomic nervous system is part of the nervous system and is
composed of the Sympathetic and the Parasympathetic systems.
The autonomic nervous system, along with the endocrine system, exerts
control over the functions of many organs and tissue in the body.
The autonomic nervous system, along with the endocrine system, exerts
control over the functions of many organs and tissue in the body.
Autonomic Nervous System (ANS)
Innervates visceral organs (smooth muscles), glands and blood vessels
Innervates visceral organs (smooth muscles), glands and blood vessels
Autonomic Nervous System (ANS)
Controls the function of different visceral organs and regulates them.
Controls the function of different visceral organs and regulates them.
Autonomic Nervous System (ANS)
It has afferent and efferent pathways.
It has afferent and efferent pathways.
Autonomic Nervous System (ANS)
The efferent fibers have their cell bodies in the spinal cord, and they
reach the sympathetic ganglia on both sides of the vertebral column.
The efferent fibers have their cell bodies in the spinal cord, and they
reach the sympathetic ganglia on both sides of the vertebral column.
Autonomic Nervous System (ANS)
The parasympathetic efferents reach their ganglia at or near the organs.
The parasympathetic efferents reach their ganglia at or near the organs.
Function of the ANS
Sympathetic and Parasympathetic
Functions at most part at the subconscious level
*Sympathetic system:
prepares and mobilizes the body in emergency cases
e.g.: during exercise, fear…
Sympathetic stimulation leads to:
increased heart rate, constriction of the arterioles of the skin and intestine,
(but, dilatation of those of the skeletal muscle), which raises the blood pressure, sympathetic stimulation leads to dilation of the pupils, sphincters close, hair stands and sweating occurs.
*Parasympathetic system:
conserves and stores the energy
e.g.: during sleep
Parasympathetic stimulation leads to :
Decrease in heart rate, pupil constriction, increased peristalsis, increased
glandular activity, sphincters open, bladder wall is contracted.
Function of the ANS
Sympathetic
Functions at most part at the subconscious level
*Sympathetic system:
prepares and mobilizes the body in emergency cases
e.g.: during exercise, fear…
Sympathetic stimulation leads to:
increased heart rate, constriction of the arterioles of the skin and intestine,
(but, dilatation of those of the skeletal muscle), which raises the blood pressure, sympathetic stimulation leads to dilation of the pupils, sphincters close, hair stands and sweating occurs.
Function of the ANS
Parasympathetic
Functions at most part at the subconscious level
*Parasympathetic system:
conserves and stores the energy
e.g.: during sleep
Parasympathetic stimulation leads to :
Decrease in heart rate, pupil constriction, increased peristalsis, increased
glandular activity, sphincters open, bladder wall is contracted.
Organization of the ANS
- Synapses between neurons are made in the autonomic ganglia.
- -Parasympathetic ganglia are located in or near the effector organs.
- -Sympathetic ganglia are located in the paravertebral chain. - Preganglionic neurons have their cell bodies in the CNS and synapse in autonomic ganglia.
- preganglionic neurons of the sympathetic nervous system originate in spinal cord segments T1-L3, or the thoracolumbar region.
- Preganglionic neurons of the parasympathetic nervous system originate in the nuclei of cranial nerves and in spinal cord segments S2-S4, or the craniosacral region.
- Postganglionic neurons of both divisions have their cell bodies in the autonomic ganglia and synapse on effector organs (heart, blood vessels, sweat glands
- Adrenal medulla is a specialized ganglion of the sympathetic nervous system.
- Preganglionic fibers synapse directly on chromaffin cells in the adrenal medulla.
- The chromaffin cells secrete epinephrine (80%) and norepinephrine (20%) into the circulation.
* Pheochromocytoma is a tumor of the adrenal medulla that secretes excessive amounts of catecholamines and with increased excretion of 3-methoxy-4-hydroxymandelic acid (VMA).
Anatomical organization
of the ANS:
Efferent sympathetic outflow:
Sympathetic: (thoraco-lumbar)
Origin: cell bodies lie the lateral horn
of the T1- L2/3 spinal cord.
Parasympathetic: (cranio-sacral)
Origin: CN III, CN VII, CNIX and CN X
and S1, S2, S3 (pelvic splanchnic nerve).
Anatomical organization
Sympathetic system:
Efferent sympathetic outflow:
Origin: cell bodies lie the lateral horn
of the T1- L2/3 spinal cord.
Receptors
Sympathetic and Parasympathetic Systems
Sympathetic system: Adrenergic receptors : Alpha receptors: α-1 and α-2 Beta receptors: β-1 and β-2 Dopamine receptors: D1 and D2
Parasympathetic system:
Cholinergic receptors:
Nicotinic receptors
Muscarinic receptors
Receptors
Parasympathetic System
Parasympathetic system:
Cholinergic receptors:
Nicotinic receptors
Muscarinic receptors
Receptors
Sympathetic System
Sympathetic system: Adrenergic receptors : Alpha receptors: α-1 and α-2 Beta receptors: β-1 and β-2 Dopamine receptors: D1 and D2
Neurotransmitters of the
Autonomic Nervous System
Neurotransmitters :
- Adrenergic neurons release norepinephrine as the neurotransmitter.
- Cholinergic neurons, whether in the sympathetic or parasympathetic nervous system, release acetylcholine (Ach) as the neurotransmitter.
- Peptidergic neurons in the parasympathetic nervous system release peptides such as vasoactive inhibitory peptide and substance P.
Receptor types in the Autonomic Nervous System
Adrenergic receptors (adrenoreceptors)
Alpha 1 receptors
- are located on vascular smooth muscle of the skin and splanchnic regions, the gastrointestinal (GI) and bladder sphincters, and the radial muscle of the iris.
- produce excitation (contraction ,constriction).
Are equally sensitive to norepinephrine and epinephrine. However, only norepinephrine released from adrenergic neurons is present in high enough concentration to activate alpha 1 receptors.
Mechanism of action : G protein alpha stimulator, Phospholipase C, formation of inositol 1,4,5-triphospate (IP3) and increase in intracellular (Ca+).
The effect of a neurotransmitter or endocrine hormone depends on the type AND location of the receptor
(clinical point)
over secretion of alpha 1 or over secretion of NE leads to hypertension
Receptor types in the Autonomic Nervous System
Adrenergic receptors (adrenoreceptors)
Alpha 2 receptors
- are located in presynaptic nerve terminals, platelets. Fat cells, and the walls of the GI tract.
- often produce inhibition (relaxation or dilation).
- Mechanism of action: G protein alpha inhibitor, inhibition of adenylate cyclase and decrease in cyclic adenosine monophosphate (CAMP).
Presynaptic nerve terminal = neuron
Receptor types in the Autonomic Nervous System
Adrenergic receptors (adrenoreceptors)
Beta 1 receptors
- are located in the sinoatrial (SA) node, atrioventricular (AV) node, and ventricular muscle of the heart.
- produce excitation (increased heart rate, increased conduction velocity, increased contractility).
- are sensitive to both norepinephrine and epinephrine, and are more sensitive than alpha1 receptors.
- Mechanism of action: activation G protein alpha stimulator, activation of adenylate cyclase and increase in cAMP.
Location: heart
(clinical point)
over stimulation of B1 or over secretion of NE leads to palpitation, tachycardia, arrythmia
Treatment: B1 blocker
medicine: propranolol
blocks step 1 of NE/B1 drawing
If patient has palpitation or heart problem and at the same time is asthmatic you CAN NOT give them propranolol recognizes the B2 and blocks the B2 which has side effect on bronchi
instead give patient medicine: Atenolol
Atenolol is only B1 blocker so asthma and heart problem patient can utilize it
Receptor types in the Autonomic Nervous System
Adrenergic receptors (adrenoreceptors)
Beta 2 receptors
- are located on vascular smooth muscle of skeletal muscle, bronchial smooth muscle, and in the walls of the GI tract and bladder.
- produce relaxation (dilation of vascular smooth muscle, dilation of bronchioles, relaxation of the bladder wall.)
- are more sensitive to epinephrine than to norepinephrine.
- are more sensitive to epinephrine than the alpha 1 receptors.
- Mechanism of action: same as for beta 1 receptors.
B2 agonist
Medicine: Albuterol
acts as B2 and can be used in place of B2 to relax bronchi
Receptor types in the Autonomic Nervous System
Cholinergic receptors (cholinoreceptors)
Nicotinic receptors
- are located in the autonomic ganglia of the sympathetic and parasympathetic nervous systems, at the neuromuscular junction, and in the adrenal medulla. The receptors at these are similar, but not identical.
- are activated by Ach or nicotine.
- produce excitation.
- are blocked by ganglionic blockers in the autonomic ganglia, but not at the neuromuscular junction.
- Mechanism of action: Ach binds to alpha subunits of the nicotinic Ach receptor, The nicotinic Ach receptors are also ion channels for Na+ and K+.
Receptor types in the Autonomic Nervous System
Cholinergic receptors (cholinoreceptors)
Muscarinic receptors
- are located in the heart, smooth muscle, and glands.
- are inhibitory in the heart (decreased heart rate, decreased conduction velocity in AV node).
- are excitatory in smooth muscle and glands (increased GI motility, increased secretion).
- are activated by Ach and muscarine.
- are blocked by atropine.
-Mechanism of action:
Heart SA node: inhibition of adenylate cyclase, which leads to opening of K+ channels, slowing of the rate of spontaneous Phase 4 depolarization, and decreased heart rate
- Smooth muscle and glands: formation of IP3 and increase in intracellular (Ca2+).
Autonomic centers-brain stem and hypothalamus
- Medulla
- Vasomotor center
- Respiratory center
- Swallowing, coughing, and vomiting centers - Pons
- Pneumotaxic center - Midbrain
- Micturition center - Hypothalamus
- Temperature regulation center
- Thirst and food intake regulatory centers
Pneumotaxiv = respiratory system
Micturition = renal system
Hypothalamus memory, learning, sexual behavior connected to limbic system(emotional behavior) body temperature endocrine system
Neurotransmitters of the
Autonomic Nervous System
Neurotransmitters act on their receptors in various tissues
Preganglionic:
Acetylcholine (Ach)
Postganglionic:
Parasympathetic: Ach
Sympathatic:
Norepinephrine (NA)
Adrenergic Receptors
Beta receptors: β-1
Located in the heart
Stimulates rate and force
Adrenergic Receptors
Beta receptors: β-2
In vascular ,bronchial ( smooth m.) ,GI tract, Relaxes
Liver Stimulates glycogenolysis
Pancreatic B cells Stimulates insulin release
B2 = bronchi, liver, beta cells in Pancreas
Adrenergic Receptors
α-1: (postsynaptic)
Located on Vascular smooth muscle contraction
Pupillary smooth M contraction (mydriasis)
pilomotor smooth M contraction (erects hair)
Adrenergic Receptors
α-2: (mostly presynaptic)
On Adrenergic and cholinergic nerve terminals
-inhibits transmitter release
fat cells -inhibits lipolysis
platelets -stimulates aggregation
Some smooth muscle(presynaptic inhibition of parasympathetic) -contraction
Cholinergic receptors
Muscarinic
in Glands +ve effect, heart –ve effect, smooth muscle (except vascular smooth muscle) +ve effect like peristalsis
Mechanism of action: increased intracellular calcium
Cholinergic receptors
Nicotinic
At the neuromuscular junction
Produce excitation (opening of Na-K channels, depolarization)
Effect of ANS on Eye
Pupil
Sympathetic = α-receptor: Dilatation
Parasympathetic = Constriction
Ciliary muscle
Sympathetic = β-rec: Accommodation Parasympathetic = Contraction
Lacrimal gland
S = decreased secretion P = increase secretion
Sympathetic
controls dilation of pupil by Alpha 2
Accommodation = Beta 2
blocks tear secretion of lacrimal glands to eyes
Salivary glands
Submandibular
S = α-receptor: Activates viscous secretion
P = activates secretion of watery saliva
Parotid
S = Vasoconstrictor
P = activates secretion of watery saliva
Sublingual
S = decreased secretion
P = increase secretion
Salivary glans secrete saliva. Sympathetic AND parasympathetic(both) increase saliva secretion by different mechanisms.
Heart(know these)
Coronary Arteries
S = β1-rec: +ve Chronotropic, β1-rec: +ve Dromotropic, vasodilation
P = -ve Chronotropic, -ve Dromotropic , vasoconstriction
Sympathetic increase heartrate \+ve Chronotropic = heart rate positive effect on Chronotropic increases contractility of conduction velocity(dromotropic) Vasodilation
Parasympathetic Vagus nerve and Acetylcholine decreases heartrate negative effect of chronotropic decreases conduction velocity(dromotropic)
Lung
Bronchi(muscle)
S = β2-receptor: Dilatation
P = Constrictor
Vessels
S = Constriction
P = Dilation
Glands
S = decreases secretion
P = increases secretion
GI tract
Peristalsis (tonus)
S = β2-receptor: Relaxation
P = Activation
Sphincters
S = α-receptor: Constriction
P = Relaxation
Glands S = decreases secretion P = increases secretion ---- Parasympathetic is more active usually Vagus nerve and Acetylcholine increases peristalsis and gastric hormones
Liver
S = β-rec: Gluconeogenesis P = Glycogenesis
Gall Bladder
Sphincters
S = β2-receptor : Relaxation
P = constriction
Parasympathetic
main neurotransmitter is Acetylcholine
CCK is a second neurotransmitter
Pancreas
Insulin
S = α-receptor: inhibits it’s secretion
S = β-receptor: activates it’s secretion
P = nothing
Exocrine
S = α-receptor: inhibits it’s secretion
P = Activates secretion
Everything is controlled by sympathetic but activation of exocrine enzymes is by parasympathetic
Adrenal medulla
S = Activates secretion
P = nothing
Adrenal medulla is an exception
Only by preganglionic fiber of sympathetic nervous system
Acetylcholine
stimulates norepinephrine/epinephrine AKA noradrenaline/adrenaline hormones
Innervation is by preganglionic fiber of sympathetic
Urinary bladder
Sphincter M.
S = α-receptor: contraction
P = relaxation
Detrusor M.
S = β-receptor: relaxation
P = contraction
—-
Sympathetic
filling of urinary bladder
Parasympathetic
emptying of bladder
Uterus
Pregnant
S = α-receptor: contraction
P = nothing
Non-pregnant
S = β-receptor: relaxation
P = nothing
Just under control of sympathetic
A1 – pregnant female
B2 – nonpregnant female
Male/Female Genitals
S = ejaculation(emission) P = Erection(vasodilatation)
Emission = internal circulation in male
Sympathetic
Erection
parasympathetic
Ejaculation
both sympathetic and parasympathetic
Sensory Systems
-are specialized epithelial cells or neurons that transduce environmental signals into
neural signals.
-The enviromental signals that can be detected
The second part of nervous system is sensory
Specific ion channels and receptors are needed.
Types of sensory transducers
1- Mechanoreceptors: respond to mechanical stimulus
- Pacinian corpuscles
- joint receptors
- Stretch receptors in muscle
- Hair cells in auditory and vestibular systems
- Baroreceptors in carotid sinus
2-Photoreceptors
-Rods and cones of the retina
- Chemoreceptors
- Olfactory receptors
- Taste receptors
- Osmoreceptors
- Carotid body O2 receptors - Extremes of temperature and pain
- Nociceptors
Types of sensory transducers
1- Mechanoreceptors
respond to mechanical stimulus
- Pacinian corpuscles
- joint receptors
- Stretch receptors in muscle
- Hair cells in auditory and vestibular systems
- Baroreceptors in carotid sinus
Types of sensory transducers
2-Photoreceptors
-Rods and cones of the retina
Types of sensory transducers
- Chemoreceptors
- Olfactory receptors
- Taste receptors
- Osmoreceptors
- Carotid body O2 receptors
Types of sensory transducers
- Extremes of temperature and pain
-Nociceptors
Fiber types and conduction velocity
-A-alpha
-large alpha-motoneurons
Conduction velocity: fastest
-A-beta
Touch, pressure
Conduction velocity: Medium
-A-gamma
gamma-motoneurons to muscle spindles (intrafusal fibers)
Conduction velocity: Medium
-A-delta
Touch, pressure, temperature, and pain
Conduction velocity: Medium
-B
preganglionic autonomic fibers
Conduction velocity: Medium
-C
Slow pain, postganglionic autonomic fibers
Conduction velocity: Slowest
Type A – alpha is fastest receptor
Type C – slowest receptor
All others are medium conduction
Fiber types and conduction velocity
-A-alpha
-A-alpha
-large alpha-motoneurons
Conduction velocity: fastest
Fiber types and conduction velocity
-A-beta
-A-beta
Touch, pressure
Conduction velocity: Medium
Fiber types and conduction velocity
-A-gamma
-A-gamma
gamma-motoneurons to muscle spindles (intrafusal fibers)
Conduction velocity: Medium
Fiber types and conduction velocity
-A-delta
-A-delta
Touch, pressure, temperature, and pain
Conduction velocity: Medium
Fiber types and conduction velocity
-B
-B
preganglionic autonomic fibers
Conduction velocity: Medium
Fiber types and conduction velocity
-C
Slow pain, postganglionic autonomic fibers
Conduction velocity: Slowest
Receptive field
-is an area of the body that, when stimulated, changes the firing rate of a sensory neuron. If the firing rate of the sensory neuron is increased, the receptive field is excitatory. If the firing rate of the sensory neuron is *decreased, the receptive field is inhibitory.
Steps in sensory transduction
a. Stimulus arrives at the sensory receptor.( photon of light on the retina, a molecule of NaCl on the tongue).
B. Ion channels are opened in the sensory receptor, allowing current to flow.
Usually the current is inward, which is depolarization of the receptor.
C. The change in membrane potential produced by the stimulus is the receptor potential, or generator potential.
Adaptation of sensory receptors
a. Slowly adapting, or tonic, receptors (muscle spindle, pressure, slow pain)
- respond repetitively to a prolonged stimulus.
B. Rapidly adapting, or phasic, receptors (pacinian corpucle, light touch)
-show a decline in action potential frequency with time in response to a constant stimulus.
Sensory pathways from the sensory receptor to the cerebral cortex
A. Sensory receptors
A. Sensory receptors
- are activated by environmental stilmuli.
- may be specialized epithelial cells (taste receptors, auditory hair cell).
- may be primary afferent neurons (olfactory chemoreceptors).
- transduce the stimulus into electrical energy ( receptor potential).
Sensory pathways from the sensory receptor to the cerebral cortex
B. First-order neurons
B. First-order neurons
-are the primary afferent neurons that receive the transduced signal and send the information to the CNS. Cell bodies of the primary afferent neurons are in dorsal root or spinal cord ganglia.
Sensory pathways from the sensory receptor to the cerebral cortex
C. Second-order neurons
C. Second-order neurons
- are located in the spinal cord or brain stem.
- receive information from one or more primary afferent neurons in relay nuclei and transmit it to the thalamus.
- Axons of second-order neurons usually cross the midline in a relay nucleus in the spinal cord before they ascend to the thalamus. Therefore, sensory information originating on one side of the body ascends to the contralateral thalamus.
Sensory pathways from the sensory receptor to the cerebral cortex
D. Third-order neurons
D. Third-order neurons
-are located in the relay nuclei of the thalamus. From there, encoded sensory information ascends to the cerebral cortex.
Sensory pathways from the sensory receptor to the cerebral cortex
E. Fourth-order neurons
E. Fourth-order neurons
-are located in the appropriate sensory area of the cerebral cortex.
The information received results in a conscious perception of the stimulus.
Somatosensory system
The somatosensory system processes information about touch, pain and temperature.
Somatosensory pathways
- Dorsal column system
- Anterolateral system
Type of somatosensory receptors
- Mechanoreceptors (for touch)
- Thermoreceptors (temperature)
- nociceptors (pain)
Somatosensory pathways
Dorsal Column system
Anterolateral system
Pathways in the somatosensory system
Dorsal column system
-processes sensations of fine touch, pressure, two-point discrimination, vibration.
Course: primary afferent neurons have cell bodies in the dorsal root. Their axons ascend ipsilaterally to the nucleus gracilis and nucleus cuneatus of the medulla.
From the medulla the second-order neurons cross the midline and ascend to the contralateral thalamus, where they synapse on third-order neurons.
Third-order neurons ascend to the somatosensory cortex, where they synapse on fourth-order neurons.
Detects fine touch, pressure, two point discrimination and vibration
Pathways in the somatosensory system
Anterolateral system
- processes sensations of temperature, pain, and light touch.
- consists primarily of group of fibers, which enter the spinal cord and terminate in the dorsal horn.
- second-order neurons cross the midline to the anterolateral quadrant of the spinal cord and second to the contralateral thalamus, where they synapse on third-order neurons.
- Third-order neurons ascend to the somatosensory cortex, where they synapse on fourth-order neurons.
Detects temperature, pain, and light touch
Thalamus
- Information from different parts of the body is arranged somatotopically.
- Destruction of the thalamic nuclei results in loss of sensation on the contralateral side of the body.
Thalamus
Pain
- is associated with the detection and perception of noxious stimuli (nociception).
- The receptors for pain are free nerve endings in the skin, muscle, and viscera.
- Neurotransmitters for nociceptors include substance P. Inhibition of the release of substance P is the basis of pain relief by opioids.
A. Fibers for fast pain and slow pain
- Fast pain is carried by group A-delta fibers. It has a rapid onset and offset, and is localized.
- Slow pain is carried by C fibers. It is characterized as aching, burning, or throbbing that is poorly localized.
B. Referred pain
-Pain of visceral origin is referred to sites on the skin and follow the dermatome rule. These sites are innervated by nerves that arise from the same segment of the spinal cord.
For example: ischemic heart pain is referred to the chest and shoulder.
Clinical point
If there is any damage to a side of the thalamus(right thalamus) then patient has a sensory disorder on LEFT side of the body
Referred pain
retrosternum pain, left shoulder, left arm, last 2 fingers pain, submandibular pain
myocardial infarction
Two-point touch threshold
If each point touches the receptive fields of different sensory neurons, two separate points of touch will be felt. If both caliper points touch the receptive field of one sensory neuron, only one point of touch will be felt.
Taste and Smell
The senses of Gustation (taste) and Olfaction (smell) fall under the category of Chemoreception.
Specialized cells act as receptors for certain chemical compounds.
Gustation and Olfaction are chemical senses because the receptors they contain are sensitive to the molecules in the food we eat, along with the air Gustatory System
In humans, the sense of taste is transduced by taste buds and is conveyed via three of the twelve cranial nerves.
- Cranial nerve VII, the facial nerve, carries taste sensations from the anterior two thirds of the tongue and soft palate.
- Cranial nerve IX the glossopharyngeal nerve carries taste sensations from the posterior one third of the tongue.
- Also a branch of the vagus nerve carries some taste sensations from the back of the oral cavity (i.e. pharynx and epiglottis).
Dendritic endings of these nerves are located around the taste buds and relay sensations of touch and temperature. Taste sensations are passed to the medulla oblongata, where the neurons synapse with second-order neurons that project to the thalamus, from here, third-order neurons project to the area of the postcentral gyrus of the cerebral cortex that is devoted to sensations from the tongue.
Types of Taste
Salt
Sour
Bitter
Sweet
Types of Taste
Salt
Arguably the simplest receptor found in the mouth is the salt (NaCl) receptor. An ion channel in the taste cell wall allows Na+ ions to enter the cell. This on its own depolarizes the cell, and opens voltage-regulated Ca2+ gates, flooding the cell with ions and leading to neurotransmitter release.
Types of Taste
Sour
Sour taste signals the presence of acidic compounds (H+ ions in solution). There are three different receptor proteins at work in sour taste. The first is a simple ion channel which allows hydrogen ions to flow directly into the cell.
Types of Taste
Bitter
Bitter compounds act through structures in the taste cell walls called G-protein coupled receptors (GPCR’s). When the bitter compound activates the GPCR, it in turn releases gustducin, the G-protein it was coupled to.
Types of Taste
Sweet
Like bitter tastes, sweet taste transduction involves GPCR’s.
Disorders of the Tongue
Ageusia
Hypogeusia
Hypergeusia
Ageusia (Loss of taste):You may lose your sense of taste if the facial nerve is damaged.
Hypogeusia (decreased taste sensitivity)
Hypergeusia (increased taste sensitivity)
Disorders of the Tongue
Sore tongue
It is usually caused by some form of trauma, such as biting your tongue, or eating piping-hot or highly acidic food or drink.
If your top and bottom teeth don’t fit neatly together, tongue trauma is more likely.
Some people may experience a sore tongue from grinding their teeth (bruxism).
Disorders such as diabetes, anemia, some types of vitamin deficiency and certain skin diseases can include a sore tongue among the range of symptoms.
Sore tongue is often found in alcoholic patients
destruction of taste buds by alcohol
Disorders of the Tongue
Glossodynia
A condition characterized by a burning sensation on the tongue.
Disorders of the Tongue
Benign migratory glossitis
This condition is characterized by irregular and inflamed patches on the tongue surface that often have white borders. The tongue may be generally swollen, red and sore. Another name for this condition is geographic tongue. The cause of benign migratory glossitis is unknown.
Olfactory System
A. Receptor cells
- are located in the olfactory epithelium.
- are true neurons that conduct action potentials into the CNS.
Olfactory System
B. CN I (olfactory)
- carries information from the olfactory receptor cells to the olfactory bulb.
- The axons of the olfactory nerves are unmyelinated C fibers and are among the smallest and slowest in the nervous system.
- Olfactory epithelium is also innervated by CN V (trigeminal), which detects noxious or painful stimuli, such as ammonia.
The olfactory nerves pass through the cribriform plate on their way to the olfactory bulb. Fractures of the cribriform plate sever input to the olfactory bulb and reduce (hyposmia) or eliminate (anosmia) the sense of smell. The response to ammonia, however, will be intact after fracture of the cribriform plate because this response is carried on CN V.
Between nasal cavity and brain
the membrane called the cribriform plate
ontop of the plate is the olfactory bulb(yellow color) which continues to olfactory tract
the bulb is penetrated by receptors to nasal cavity
Olfactory System
C. Mitral cells in the olfactory bulb
- are second-order neurons.
- output of the mitral cells forms the olfactory tract, which projects to the cortex.
Steps in transduction in the olfactory receptor neurons
A. Odorant molecules bind to receptors located on cilia of the olfactory receptor neurons.
B. When the receptors are activated, they activate G proteins (G olf), which in turn activate adenylate cyclase.
C. There is an increase in intracellular (cAMP) that opens Na+ channels in the olfactory receptor membrane and produces a depolarizing receptor potential.
D. The receptor potential depolarizes the initial segment of the axon to threshold, and action potentials are generated and propagated.
When odor binds to olfactory receptors it leads to depolarization of receptors and release stimulatory neurotransmitter.
The stimulatory neurotransmitter stimulates the first group of neurons which pass through the cribriform plate and enters the olfactory bulb
the first group of cells is called Mitral cells
Mitral cells have synapse with second group of cells in olfactory tract and the second group of neurons travel to the olfactory center which is located at the base of the olfactory tract.
mitral cells reach olfactory bulb by passing through the cribriform plate
Mitral cells interact with second group of neurons which travels to the olfactory tract
then after olfactory tact group 2 reaches olfactory center located at the base of the olfactory tract
depolarization of cells is by opening of Na+ channels and Na+ inflow to cells
Disorders of Olfaction
Anosmia
Anosmia is the lack of olfaction, or a loss of the sense of smell.
Detection of pain in olfactory is by CN 5(trigeminal nerve)
Disorders of Olfaction
Phantosmia
Phantosmia is the phenomenon of smelling odors that aren’t really present.
Disorders of Olfaction
Dysosmia
When things smell differently than they should.
