Exam 3 Flashcards
Acetylcholine
-released from cholinergic neurons
-major NT in peripheral nervous system and neuromuscular junction
-acts on 2 receptor subtypes to exert dif. effects (nicotinic and muscarinic)
nicotinic receptors
-stimulatory
-ionotropic
muscarinic receptors
-stimulatory or inhibitory
-metabotropic *Giq protein linked
acetylcholinerase
-in the post-synaptic membrane
-converts ACh to choline and acetic acid
-choline taken up and combined with acetyl-CoA and repackaged
biogenic amines- catecholamines specifically
-dopamine
-serotonin
-noradrenergic and adrenergic neurons
dopamine
involved in reward and movement pathways
noradrenergic and adrenergic neurons
-act on 5 types of metabotropic receptors (adrenergic receptors)
-alpha 1, 2, and beta 1,2,3
-major NT of sympathetic nervous system
serotonin
-serotonergic neurons
-function in motor activity, sleep, food intake, reproductive behaviors, bone remodeling, and emotional states
percentages of serotonin found across the body
-90% digestive tract
-8% found in platelets
glutamate
-glutamatergic neurons
- predominant excitatory NT in CNS
ionotropic
-excitatory post synaptic potential (epsp)
-AMPA and NMDA
-channel-linked
AMPA
-non-selective cation channel
NMDA
-Ca++ channel
metabotropic
-8 subtypes
-use g-proteins and second messengers
-Gq, Gi
GABA
-GABAnergic receptors
-predominant inhibitory NT in brain
glycine
-glycinergic neurons
-one ionotropic receptor
(Cl- channel) IPSP of stabilizing current
-inhibitory
what do neuropeptides mostly act as?
neuromodulators
endogenous opioids
-(beta-endorphin, dynorphin, enkephalins)
-acts presynaptically to reduce painful stimuli reaching consciousness
-plays a role in eating, drinking, regulation of cardiovascular system, and in emotion
substance p
-released from pain sensory neurons into the CNS
-appear to enhance painful stimuli perception
peripheral nervous system divisions
-afferent
-efferent
afferent division
somatic, visceral, special sensory
efferent division
somatic motor, autonomic motor, sympathetic, parasympathetic, enteric
autonomic nervous system
-involuntary/visceral
-maintain optimal internal environment
-sensory + motor
-3 divisions- sympathetic, parasympathetic, enteric
enteric
-“the brain of the gut”
-can autonomously regulate primary and accessory digestive organs
-influenced by sympathetic and parasympathetic systems, but outside aren’t necessary
somatic nervous system effector organs
CNS -> skeletal muscle
autonomic nervous system effector organs
CNS -> smooth cardiac muscles, glands, or other cells
-uses preganglionic fiber, ganglion, then postganglionic fiber
what innervates most internal organs?
parasympathetic
where do parasympathetic fibers arise from?
-brain stem
-cranial nerves: III oculomotor, VII facial, IX glossopharyngeal, X vagus
-sacral spinal cord S2, S3, S4
what does the sympathetic directly regulate?
-cardiovascular system
-can indirectly affect other organs thru actions on blood vessels and release of epinephrine + norepinephrine from adrenal medulla
sympathetic division
thoracolumbar division- ganglia near spinal cord
parasympathetic division
craniosacral division- ganglia near or within wall of target organ
3 types of routes that can be taken by sympathetic axons
- spinal nerves
- sympathetic nerves
- splanchnic nerves
spinal nerve route
- preganglionic cell bodies in the lateral horn
- myelinated axons exit the ventral motor root
- they enter the sympathetic chain through the white ramus communicans
- the preganglionic axon synapses with postganglionic neurons in the simple chain ganglia
5.unmyelinated axons exit ganglia thru grey ramus communicans and re enter the spinal nerves
sympathetic nerve route
1.preganglionic axons exit the ventral motor root
2.they enter the sympathetic chain thru the white ramus communicans
3.the preganglionic axon synapses with the postganglionic neurons and exit the ganglia thru a sympathetic nerve
splanchnic nerves route
- preganglionic axons pass through sympathetic chain ganglia without synapsing to form splanchnic nerves
- preganglionic axons then synapse with postganglionic neurons in prevertebral (collateral) ganglia. Post ganglionic neurons then send fibers to target organs (viscera)
innervation to adrenal gland route
- preganglionic axons synapse directly with the cells of the adrenal medulla
- embryologically, adrenal medulla is derived from same cells as post ganglionic ANS cells
- medullary cells secrete epinephrine and norepinephrine; act as hormones supporting physical activity
sympathetic and parasympathetic organization
hypothalamus->brain stem->effector organs->spinal cord->effector organs
what do some sympathetic postganglionic neurons release?
acetylcholine
both branches use ACh to act on…?
muscarinic receptors in the ganglia
parasympathetic postganglionic neurons release ACh to act on…?
muscarinic receptors in the target organ
what do sympathetic postganglionic neurons usually release? and what does it act on?
-norepinephrine
-acts on either alpha or beta-adrenergic receptors
what is often also released from the postganglionic neuron?
-cotransmitters
-play a small role in effector response
what are cells of the adrenal medulla more like?
-sympathetic postganglionic neurons
sympathetic
-“fight or flight”
-stimulated by stress
-readies body for physical activity
-diffuse stimulation of organs
parasympathetic
-“rest and digest”
-coordinates processes needed for basic survival
-fine control over individual organ systems
do parasympathetic and sympathetic systems both work at the same time?
-both will always have some sort of activity at any given time
adrenergic receptors
alpha 1, 2, beta 1, 2, 3
alpha 1
-contractile effects
-norepinephrine/epinephrine on smooth muscle (blood vessels, urogenital, sphincters)
alpha 2
-inhibit norepinephrine release
beta 1
stimulatory effects of norepinephrine/epinephrine in the heart to increase heart rate and force of heart contractions
beta 2
-relaxing effects of predominately epinephrine on smooth muscle (gastrointestinal tract, urogenital, airway)
beta 3
-involved in lipolysis, glycogenolysis, and thermogenesis
blood-brain barrier contains
tight junction, astrocytes, and carrier mediated transport
sensory system
-parts of CNS that process
-neural pathway
-receptor
stimulus in a sensory system
-graded potential (receptor potential)
-action potential in afferent
sensory unit
single afferent neuron w/ all its receptor endings
receptive field
-area of body that when stimulated leads to activity in a particular afferent neuron
can receptive fields overlap?
receptive fields for nearby neurons overlap
signal transduction
-when a stimulus is transformed into an electrical response- sensory transduction
signal transduction receptors
-many receptors that each respond to a different stimulus
-some receptors more picky than others
-adequate stimulus is what activates a receptor
can receptors respond to stimuli other than their adequate stimulus?
-yes. but only if the signal is intense enough
-receptors can only code one sensation though
how does all sensory transduction begin?
-with opening or closing of an ion channel (direct or indirect)
where are ion channels located?
on distal tip of axon or on a receptor cell
receptor potential
graded potential produced by ion channels
the greater the graded potential is above threshold…
the greater the frequency of action potentials
the magnitude of graded potential depends on…
1.stimulus strength
2.rate of change of stimulus strength
3.adaptation
4.temporal summation of successive receptor potentials
coding
converting stimulus energy to a signal the CNS can interpret
coding signals
- modality
- intensity
- location
- acuity
location in coding
afferents follow unique pathways to specific areas of CNS
lateral inhibition
-enhances contrast
-utilized to greatest degree in pathways providing the most acuity
-not used as much in pain and temperature
-VERY IMPORTANT in visual activity
lateral inhibition- rapidly adapting receptors
-on-receptor
-off-receptor
sensory pathway
-bundle of parallel, three-neuron chains together
-1st order, 2nd order, 3rd order
specific ascending sensory pathways
carry one type of information
where does sensory information usually cross over to?
the opposite side of brain from where it originated
nonspecific ascending pathways
-utilize polymodal neurons
-control alertness and arousal
somatic sensation
sensations arising from skin
somatic sensation receptor thingies
- meissners corpuscle
- merkles corpuscle
- free nerve ending
- pacinian corpuscle
- ruffini corpuscle
meissners corpuscle
-rapidly adapting mechanoreceptor
*touch and pressure
merkles corpuscle
-slowly adapting mechanoreceptor
*touch and pressure
free nerve ending
-slowly adapting, some nocireceptors, some thermoreceptors, some mechanoreceptors
pacinian corpuscles
-rapidly adapting mechanoreceptor vibration and deep pressure
ruffini corpuscle
slowly adapting mechanoreceptor- skin stretch
variety of mechanoreceptors
-hair bending
-deep pressure
-vibrations
-superficial touch
how mechanoreceptor works
- mechanical tension in capsule
- opening of ion channel
- activation of neuron
rapidly adapting mechanoreceptors
touch, movement, vibration
slowly adapting mechanoreceptors
pressure
mechanoreceptors (proprioceptors)
-found in muscles, joints, tendons, ligaments, skin, vestibular system, vision
temperature + nociceptors
extremes in temperature activate pain receptors
0-35 degrees C (cold)
-nonselective cation channel
-menthol
30-50 degrees C (hot)
-nonselective cation channel
-capsaicin and ethanol
nociceptors
-intense mechanical deformation
-excessive heat or cold
chemical involved with nociceptors
-bradykinin
-prostaglandin
-histamine
-cytokines
-neuropeptides
what are glutamate and substance P related to?
transmission of pain info into CNS
why is pain in visceral organs perceived as pain in skin or skeletal muscles?
because visceral organ nociceptor afferents often synapse on same interneurons in spinal cord as skin nociceptor afferents
what do painful stimuli cause?
upregulation of receptors and hyperalgesia
anterolateral system
-carries pain and temp. info from skin to brain
dorsal column system
-receptors for body movement, limb positions, fine touch discrimination, and pressure
is there overlap in somatosensory cortex?
-yes
-sizes of areas can change with sensory experience
tarsal gland/meibomian glands
-specialized sebaceous glands produce sebum
Function: -forms junction between conjunctiva and skin
-prevents tears from flowing over eyelid margin
-a component of tear film on anterior surface of eye
-retards tear evaporation
lacrimal apparatus
-parasympathetic fibers of facial nerve VII
lacrimal gland
-innervated by parasympathetic fibers of facial nerve VII
Function:-moisten and lubricate the eye surface and eyelids
-produces tears
-kill bacteria
puncta + lacrimal canaliculi
-collect excess tears through puncta
lacrimal sac
-leads to nasolacrimal duct which opens into nasal cavity
conjunctiva
-very vascular
-thin mucous membrane
-lines posterior surface of eyelids+anterior surface of eyeball (non keratinized stratified squamous epithelium)
-2 PARTS
*palpebral conjunctiva
*ocular or bulbar conjunctiva
palpebral conjunctiva
-closely attached
-“inside” layer of eyelid (palebrae)
ocular or bulbar conjunctiva
-thin, translucent
-loosely attached to sclera by connective tissue
3 layers of the eye!
- fibrous
- vascular
- nervous
fibrous layer
sclera and cornea
vascular layer
-choroid, ciliary body, iris
-contains most blood vessels of the eye
nervous layer
retina
sclera
-outside layer (muscle attachment)
-maintains eye shape
-protects internal structures of eye
-opaque (white color)
-dense collagenous connective tissue w/ elastic fibers
cornea
-transparent
-responsible for refraction of light
choroid
-thin layer
-darkly pigmented
-just deep to sclera
-very vascular
-function to nourish retina and absorb excess light
ciliary body
-produces aqueous humor that fills anterior chamber
-ciliary muscle
-smooth muscle
-controls lens shape
-ciliary processes attach to lens
iris
-colored portion of eye- suspended in aqueous humor between cornea and lens
-thin smooth muscle
-controls amt. of light entering eye
-pupil- opening
sphincter pupillae muscle
-parasympathetic
-controls pupil
contraction of sphincter pupillae muscle decreasing diameter uses
epinephrine
nervous layer of eye
- neural layer
- pigmented retina
neural layer
-contains sensory cells =, interneurons, support cells, and axons of optic nerve
pigmented retina
-outer layer
-pigmented simple cuboidal epi.
-separates retina from choroid
-reduces light scattering
compartments of eye
1.anterior compartment
2.posterior compartment
anterior compartment
-anterior to lens
-filled with aqueous humor
-produced by ciliary body
-returned to venous circulation thru Canal of Schlemm
-helps maintain intraocular pressure
-supplies nutrients to associated structures
-helps refract light
*Two Chambers:
1.anterior chamber
2.posterior chamber
anterior chamber location
between cornea and iris
posterior chamber location
between iris and lens
posterior compartment
-posterior to lens
-filled with vitreous humor
-majority of mass of eyeball
-98% water, amino acids, and hyaluronic acid
-helps maintain intraocular pressure
-helps hold lens and retina in place
-slightly refracts light
