NEUROPHYSIOLOGY Flashcards
set of tpatways to and from the CNS that innervates and regulates smooth muscle, cardiac muscle, and glands
Autonomic Nervous system
3 divisions of ANS
Sympathetic
Parasympathetic
Enteric
[ANS] synapses between neurons are made in the__________
autonomic ganglia
located in in or near the effector organs
Parasympathetic ganglia
Located in the paravertebral chain
Sympathetic ganglia
Have their cell bodies in the CNS adn synapse in the autonomic ganlia
Preganglionic neurons
Preganglionic neurons of the sympathetic nervous system originate in the spinal cord segments ________
T1-L3 or thoracolumbar region
Preganglionic neurons of the parasympathetic nervous system originate int he nuclei of cranial nerves and in the spinal cord segments ________
S2 to S4 or craniosacral region
_________ of both devisions of ANS have their cell bodies in the autonomic ganglia ans synapse on effector organs
Postganglionic neurons
specialized ganglion of the sympathetic nervous system
Adrenal medulla
- preganglionic fibers synapse directlt in chromaffin cells
- secretes epinephrine (80%) and norepinephrine (20%)
tumor of the adrenal medula that secretes excessive amount sof catecholamnes and is associated with increased excretion of 3 methoxy-4-hydroxy mandelic acid (VMA)
Pheochromocytoma
______release norepinephine as the neurotransmitter
Adrenergic neurons
________ release ACh weheter in the SNS or PNS as the neurotranmistter
Cholinergic neurons
includes some postganglionic parasympathetic neurons of the GIT, which releasse substance P, vasoactive intestinal peptide
Nonadrenergic, noncholinergic neurons
Organization of the autonomic Nervous system
Sympathetic or Parasympathetic
Short preganglionic nerve axon
Sympathetic
Sympathetic or Parasympathetic
long oreganglionic nerve axon
Parasympathetic
Sympathetic or Parasympathetic
Nicotinic receptors in ganglion
BOTH
Sympathetic or Parasympathetic
Muscarinic receptor in effector organs
Parasymapthetic
- alpha 1, alpha 2, B1 and B2 = Sympathetic
- nicotinic = somatic *
Signalling pathways and mechanisms forAutonomic receptors
Adrenergic receptors
alpha 1
alpha 2
Beta 1
Beta 2
Cholinergic receptors
NM (N1)
NN (N2)
M1
M2
M3
located on vascular smooth muscles of the skin and splanchic regions, the GI, and bladder sphincters, and the radial muscle of the iris
Alpha 1
- Produce excitation (contraction or constriction)
Mechanism of action of alpha 1 receptors
Gq protein, stimulation of phospholipase C and increase IP3 and intracellular calcium
Located on the sympathetic postganglionic nerve termnals (autoreceptors), platelets, fat cells, and the walls of the GI tract (heteroreceptors)
alpha 2
- often produce INHIBITION (relaxation or dilation)
Mechanism of action of alpha 2 receptors
Gi protein, inhibition of adenylate cyclase and decrease in cAMP
located in the SA node, AV node, and ventricular muscle of the heart
B1 receptors
- Produce EXCITATION (increased heart rate, increased conduction velocity, increased contractility)
- sensitive to both NE and E.
- more sensitive than alpha 1
Mechanism of action of B1 receptors
Gs protein, stimulation of adenyate cyclase and increase in cAMP
located on vascular smooth muscle of Skeletal muscle, bronchial smooth muscle, and the walls of GIT and bladder
B2 receptors
- Porduce RELAXATION (dilation of vascular smooth muscle, dilation of brochioles, relaxation of the bladder wall)
- More sensitive to EPINEPHRINE than NE
- more sensitive to EPINEPHRINE than alpha 1
Mechanism of Action of B2 receptors
Gs protein, stimulation of adenylate cyclase and increase in cAMP (similar to B1)
EXCITATION OR RELAXATION?
alpha 1
excitation
EXCITATION OR RELAXATION OR INHIBITION?
alpha 2
inhibition
EXCITATION OR RELAXATION OR INHIBITION
B1
Excitation
EXCITATION OR RELAXATION OR INHIBITION
B2
Relaxation
located in the automic ganglia of the sympathetic and parasympathetic nervous system, at the NM junction and in the Adrenal medulla
Nicotinic reeptors
- Activated by ACh or nicotine
- produce EXCITATION
Nicotinic receptors are blocked by _________ in the autonomic ganglia, but not in the NMJ
ganglionic blockers (hexxamethonium)
Mechanism of action of Nicotinic receptors
ACh binds to alpha subunits of the nicotinic ACh receptor.
The nicotinic receptors are also ion channels for ________
Na and K
Located in the heart, smooth muscle, and glands
Muscarinic
- M2 (heart)
- M3 (smooth muscle , glands)
- activated by ACh and muscarine
muscarinic receptors are _______ in the heart
inhibitor
muscarinic receptors are ______ in smooth muscles and glands
Excitatory
Muscarinic receptors are blocked by ________
atropine
Mechanism of action of muscarinic receptors
- Heart SA node: Gi protein, inhibition of adenylate cyclse, which leads to opening of K channels, slowing of the rate of spontaneous phase 4 depolarization and decreased heart rate
- Smooth muscle and glands: Gq, stimualtion of phospholipasee C, and in increase in IP3 and intracellular Calcium
Prototype of drugs that affect autnomic activity
alpha 1 agonists
Norepineehrine
Phenylephrine
Alpha 1 antagonists
Phenoxybenzamine
Phentolamine
Prazosin
Alpha 2 agonist
clonidine
Alpa 2 antagonists
Yohimbine
Beta 1 agonists
Norepinephrine
Isoproterenol
Dobutamine
Beta 1 antagonists
Propanolol
Metoprolol
Beta 2 agonist
Isoproterenol
Albuterol
B2 antagonist
Propanolol
Butoxamine
Nicotinic agonists
ACh
Nicotine
Carbachol
Nicotinic anatagnist
Curare (NMJ)
Hexamethonium (ganglionic N2 rceptors)
Muscarinic agonist
ACh
Muscarine
Carbachol
Muscarinic antagonist
Atropine
Effects of the autonomic nervous system on organ system
vasomotor center
respiatory center
swallowing, coughing, and vomiting center
Medulla
Pneumotaxic center
Pons
Micturition center
Midbrain
temperature regulaion center
thirst and food intake regulatory center
hypothalamus
Specialized epithelial cells or neurons that transduce environmental signals into neural signals
Sensory receptors
Types of sensory transducers
- Mechanoreceptors
- Photoreceptors
- Chemoreceptors
- Extreme of temperature and pain (nociceptors)
area of the body that, when stimualtd, changes, the firing rate of a sensory neuron.
Receptive field
Nerve fiber types
Steps in sensosry transduction
- Stimulus arrives at the sensory receptor
- Ion channels are opened in the sensory receptors
- usually inward. causing DEPOLARIZATION
- exception: Photoreceptors (HYPERPOLARIZTAION)
- The change in membrane potential produced by the stimulus is the receptor potential or genrator potential
Slowly adpating or tonic receptors
muscle spindle; pressure; slow pain
Rapidly adapting of phasic receptors
pacinian corpuscle; light touch
Sensory pathways from the receptor to the cerebral cortex
- Sensory receptors
- transduce the stimulus to electrial energy
- First order neurons
- Second order neurons
- third order neuron
- fourth order neurons
First order neuron of sensory pathway
primary afferent neurons.
dorsal root or spnal cord ganglia
Second order neuron of sensory pathway
relay nuclei and transmit to the thalamus
located in the SC or brain stem
May cross the midlone
Third order neuron of sensory pathway
located in the relay nuclei of the thalamus
from there, encoded sensory information ascends to the cerebral cortex.
fourth order neurons
located in the appropriate sensory area of the cerebral cortex. the information received results in a conscious perception of the stimulus
Includes the seantion of touch, movement, temperature,and pain
Somatosensory system
Pathways in the somatosensory system
Dorsal Column system
Anterolateral system
processes sensations of fine touch, pressure, two pint discrimination, vibration and proprioception
Dorsal column system
somatosensory system that is primary consists of group II fibers
Dorsal column system
Course of Dorsal column system
- Primary afferent neurons n the dorsal root
- ascends ipsilateral to the nucleus gracilis and nucleus cuneatus of the medulla
- cross the midline of medulla
- ascends to the thalamus
- ascends to the somatosensory cortex
processes sensations of temperature, pain, and light touch
anterolateral system
consists primarily of group III and IV fibers, which enter th SC and terminate in the dorsal horn
Anterolateral system
Course of anterlateral system
- Second order neurons cross the midle to the anterolateral quadrant of the SC
- ascends to th contralateral thalamus
- ascends to the somatosensory cortex
Onion like structures in the SC skin (surronding unmyelinated nerve endings)
pacinian corpuscles
- Detects vibration, tapping
- rapidly adapting
Present in nonhairy skin
Meissner corpuscle
- Detects velocity
- Rapidly adapting
Encapsulated, detects pressure, slowly adapting
Ruffini corpuscle
transducer is on the epithelial cells, detectslocation, slowly adapting
Merkel disc
information from different parts of the body is arranged somatotropically
thalamus
Destruction of the thalamic nuclei results in the loss of sensation on the___________side of the body
contralateral
The major soatosensory areas of the cerebral cortex are _______
SI and SII
has somatotropic representation similar that in the thalamus
SI
the largest areas in the homuculus represent the ___ , _____, ____ where precise localization is most important
Face, hands, and fingers
associated with the detection anf perception of noxious stimuli
Pain
The receptors for pain are ________
free nerv endings
Neurotransmitters for nociceptors _______
substance P
carried by group III fibers.
fast pain
carried by C fibers. Achinh, burning, or throbbing that is poor;y localized
slow pain
Pain of visceral origin is referred to sites on the skin and follows the dermatome rule.
Referred pain
Refractive power of a lens is measuredin _____
diopters
equals to the reciprocal of the focal distance in meters
diopters
Farsighted. Light focuses behind the retina
Hypertropia
- corrected by convex lens
Nearsighted. Light focuses in front of the retina
Myopia
- corrected with biconcave lens
curvature of the lens is not uniform
Astigmatism
- corrected with a cylindric lens