Physiology Test 2
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- Structure of Spinal Nerves
- -emerge at different levels of the spinal cord -except 1st pair and last 10 pairs, emerge from vertebral canal through intervertebral foramina to different body regions (plexes) -last 5 exit sacral canal -31 pairs
- dorsal (posterior) root
- -extends off posterior side of spinal cord -contains dorsal root ganglion made of sensory neuron cell bodies -carries sensory impulse from spinal nerve to spinal cord
- ventral (anterior) root
- -extends off anterior side of spinal cord -carries motor impulses from spinal cord to spinal nerves to nerve plexes (networks in cervical, brachial, lumbar, sacral regions)
- Dorsal root vs. Ventral root
- anterior vs. posterior side of spinal cord sensory impulses vs. motor impulses from spinal cord to spinal nerve vs. from spinal nerve to spinal cord
- plexes
- -networks are created by components of separate spinal nerves in specific regions of the body -specific nerves emerge from plexus and extend to specific body structures
- plexes body regions
- cervical, brachial, lumbar, sacral body regions
- Spinal nerves function
- participate in spinal (somatic) and visceral (autonomic) reflexes
- spinal vs. visceral reflexes
- somatic vs. autonomic skeletal muscle vs. internal organs
- spinal reflex arc
- physiological unit of function of the nervous system -pathway a nerve impulse takes to produce a reflex -purposeful, involuntary reflex made in response to a stimulus
- elements of a spinal reflex arc
- -receptor -somatic afferent (sensory) neuron -interneuron -somatic efferent (motor) neuron -effector
- receptor of spinal nerves
- converts a specific stimulus into an action potential in a sensory (afferent) neuron
- somatic afferent (sensory) neuron
- transmits action potentials from a receptor to the spinal cord
- interneuron in spinal nerves
- -not always present; found in spinal cord -transmit AP from afferent neuron to motor neuron on the same side or opposite side of spinal cord -located in gray matter
- somatic efferent (motor) neuron
- transmits action potentials from a sensory neuron or an interneuron to an effector
- effector for spinal nerves
- (skeletal muscle) carries out an action like a contraction or inhibition
- types of spinal (somatic) reflexes
- -stretch or myotactic reflex -tendon reflex -flexor/withdrawl reflex
- stretch or myotactic reflex
- involves only 2 neurons (also referred to as a monosynaptic reflex) ex: knee jerk reflex
- types of stretch or myotactic reflex
- -muscle spindle (receptor)
- tendon reflex
- involves at least three neurons also referred to as a polysynaptic reflex
- golgi organs (receptors)
- (gogli end organs) located in skeletal muscle tendons -respond to increased tension in a tendon because its muscle is contracting
- flexor or withdrawal reflex
- stimulated by pain stimuli -causes an arm or leg (usually) to be withdrawn from a painful stimulus and at the same time informs the brain for interpretation of pain in a specific location
- spinal stimuli
- muscles, tendons, skin stimulate
- autonomic stimuli
- external stimuli: light, sound and chemicals internal stimuli: changes in body temp, fluid chemistry, temp or pressure in organs
- spinal neurons
- somatic afferent, interneuron (sometimes), somatic efferent
- autonomic neurons
- visceral afferent, visceral efferent 2 motor neurons in sequence
- spinal effectors
- skeletal muscle and some glands effect and papillae
- autonomic effectors
- internal organs (heart, blood vessels, stomach, intestines, glands, intrinsic eye muscles)
- sympathetic nervous system
- (autonomic nervous system, motor only) associated anatomically with the thoracic/lumbar region of the spinal cord
- parasympathetic nervous system
- (autonomic nervous system, motor only) associated anatomically with the cranial and sacral regions
- autonomic nervous system
- -part of the pNS that is not under voluntary control -motor components: sympathetic ns and parasympathetic ns
- dual autonomic innervations
- when a visceral effector is innervated by both sympathetic and parasympathetic systems
- general autonomic principles
- -autonomic reflexes tend to restore homeostasis very quickly -dual autonomic innervations -single autonomic innervations -autonomic neurotransmitters
- single autonomic innervations
- when a visceral effector is innervated by only one division of the ans (sympathetic ns or parasympathetic ns)
- autonomic neurotransmitters
- 1. acetycholine (cholinergic) : all preganglionic neurons (Sympathetic & Parasympathetic), all parasympathetic postganglionic neurons, some sympathetic postganglionic neurons
- sensory unit
- receptor, neural pathway, interpretation center in cerebral cortex
- sensory unit receptor
- special cell or specialized end of a sensory neuron (axon)
- sensory unit neural pathway
- sensory and interneurons (only in gray matter of spinal cord and brain) that ascend up the spinal cord to the brain
- Senses receptor
- -direct stimuli from the external or internal environment -respond to one specific type of stimulus (specificity) -produce generator potentials (local depolarizations) that summate into action potentials in sensory neurons
- exteroreceptors of the senses
- receive stimuli from exterior of the body (located in skin, tongue, eye, ear or nasal cavity)
- cutaneous or skin receptor
- located in dermis or tongue -light touch (Meissner's, Krause's or Ruffini's corpuscles, Merkel's discs and free nerve endings wrapped around hair follicles)
- cutaneous receptor sensitivity
- depends on the number of receptors per square inch of skin surface; fingers have a higher density of receptors than the back of the hand
- cutaneous receptor deep pressure
- Pacinian corpuscles located in subcutaneous tissue and connective tissues around organs
- cutaneous receptor temperature
- free nerve endings located in the dermis of skin -heat: when skin temperature increase between 30-45 C, receptors generate action potentials -cold: when skin temperature decreases between 40-10 C, receptors generate action potentials
- cutaneous receptors for pain
- (nociceptors) free nerve endings found in skin, mucous and serous membranes, internal organs (aka interoreceptors)
- types of pain
- somatic, visceral, referred
- somatic pain
- superficial - sensations from skin deep - sensations from skeletal muscles, tendons, joints and fascia
- visceral pain
- sensations from internal organs
- referred pain
- can be deep somatic or visceral but NEVER superficial somatic -source of pain is deep and it occurs due to ischemia or distension -pain feels as if it is coming from skin surface area but really being generated deeper in the body
- ischemia
- lack of blood supply
- distension
- excessive stretching of a hallow body organ -ex: gas
- theory of referred pain
- -sensory pathways for deep organs follow similar pathways as overlying skin sensory paths -both pathways converge of the same interneurons in the spinal cord -brain cannot interpret referred pain because those pathways are NOT frequently used so brain instead interprets pain as coming from the skin area over the source of pain Ex: pain of appendicitis, angina, and heart attack
- propiroceptors
- located in skeletal muscles around tendons and joints that respond to stretch Ex: muscle spindles and golgi tendon organs -give you spatial awareness
- interoreceptors
- located in body organs and major blood vessels -sensitive to pain, stretch, change in pressure, alteration of chemical composition of ECF or blood plasma, alteration in temperature of blood
- interoreceptors sensitivity to stretch
- in the lungs
- interoreceptors sensitivity to change in pressure
- (pressoreceptors or baroreceptors) -found in the right atrium, aorta, vena cave, and carotid sinus )all involved in regulating blood pressure
- interoreceptors sensitivity to alteration of chemical composition of ECF or blood plasma
- (chemoreceptors) -found in medulla oblongata, internal carotid artery, and aorta (prominently associated with alterations of oxygen and carbon dioxide levels of the blood)
- interoreceptors sensitivity to alteration in temperature of blood
- (thermoreceptors) -found in hypothalamus of brain
- interoreceptors sensitivity to pain
- (in all body organs except the brain) -internal nociceptors -no receptors in the brain so no pain; pain in brain is caused my meninges
- special senses
- gustatory (taste) and olfactory (smell)
- gustatory sense (taste)
- -taste cells (receptors): sensitive to chemicals dissolved in saliva -taste cells are located in taste buds that are components of taste papillae mainly located on the tongue surface -five types of taste cells detect: sweet, sour, salty, bitter, savory (umami)
- location of taste buds on the tongue
- different taste buds are located equally over the surface of the tongue -some areas respond somewhat more strongly to certain taste stimuli
- taste innerventon
- -Facial nerve (VII): innervates the taste buds found on the anterior 2/3 of the tongue -Glossopharyngeal nerve (IX): innervates taste buds in the posterior 1/3 of tongue -Interpretation center:interpretation of taste occurs in the parietal lobes
- Olfactory (smell) sense
- -receptors and pathways: olfactory cells (receptors) are sensitive to volatile chemicals that are water and lipid soluble --olfactory cells in olfactory epithelium located high in nasal cavity --axons of olfactory cells pass through olfactory foramina of the cribiform plate into olfactory bulb and synapse with mitral cells and their axons pass over olfactory nerve (I) to the interpretation center located in frontal lobe
- autonomic antagonism and dominance
- effector has dual innervation, the neurotransmitter has opposite effects -> higher concern, displays effect
- Sclera
- outer layer made of white fibrous connective tissue -white part of eye -cornea: anterior clear portion attached to sclera
- choroid
- middle layer, well supplied with blood vessels and is dark pigmented anterior region and posterior region
- Layers of the eye
- Sclera, cornea, choroid, ciliary body, ciliary muscle, iris, papillae (dilatory & sphincter), retina, neurons (photoreceptor & ganglion), macula lutea, fovea centralis, optic disc
- posterior region of the choroid
- aids in maintaing nutrition for the retina
- anterior region of the choroid
- modified into ciliary body and iris
- ciliary body
- -processes: extend off of ciliary body; connect to Zonular fibers (collectively called the suspensory ligament of the eye); suspensory ligament in turn connects to lens -ciliary muscle: (smooth, involuntary) connect posterior choroid to sclera; when contracted, pull the choroid and ciliary body forward toward cornea
- iris
- colored portion; regulates amount of light that enters eye through the pupil -dilatory papillae: radial -sphincter papillae: circular
- retina
- inner layer; made of six layers of neurons and other cell types 1. photoreceptor neurons 2. bipolar layer 3. ganglion neurons 4. macula lutea 5. fovea centralis 6. optic disc or blind spot
- photoreceptors neurons
- rods (100 million) and cones (3 million) -last layer of retina that light passes through as it enters -located adjacent to choroid
- bipolar layer
- connects photoreceptors to ganglion layer -sensory interneurons
- ganglion neurons
- innermost layer of neurons (adjacent to vireos body) -axon converge to form the optic nerve at optic disc
- macula lutea
- yellow pigmented disc located in center of posterior wall of retina
- fovea centralis
- depression in center of macula lutea, contains only cones -images focused on the fovea in bright light -cones provide us with color vision -great visual acuity (detects sharp images)
- optic disc or blind spot
- -point where ganglion neuron axon converge and form optic nerve -off center, medial side of eye -no rods or cones, so light rays are not detected here
- posterior cavity of eye (vitreous chamber)
- lies behind the lens and extends all the way to the retina; filled with gel-like substance (vitreous humor) -helps maintain intraocular pressure to prevent eyeball from collapsing
- anterior cavity of eye
- lies in front of the lens -made of two chambers filled with aqueous humor (watery) -maintain intraocular pressure and is a medium of exchange for the lens and cornea
- anterior chamber of eye connects
- cornea connects to iris
- posterior chamber of eye connects
- iris connects to lens
- glaucoma
- -normal pressure is 20-25mgHg; if > 25mgHg -due to blockage of canal of Schlemm (lack of drainage of anterior cavity) or excessive production of aqueous humor -either case increases pressure on the retina -> damage to the optic nerve -> untreated, then blindness
- eyelids (palpebrae)
- upper and lower folds of skin (cover eye surface); moved by contraction of skeletal muscle [orbicularis oculi (circular muscle that closes eyelid and levitator palpebrae (raises upper eyelid)]
- palpebrael fissure
- space between eyelids
- conjuctiva
- mucous membrane lines inner surface of both eyelids and continues over the anterior surface of the sclera but NOT over the cornea -palpebrael (eyelids) & ocular (ant surface of eye)
- conjuctiva function
- -decrease friction as eyelids pass over anterior surface of eye -mucus entraps particles that may land on surface of eye to keep surface clean
- canthus
- point where upper and lower eyelid fuse together -lateral & medial : sides of eye
- caruncle
- pink dot of tissue located at medial canthus -landmark for the ophthalmologist
- lacrimal apparatus
- lacrimal glands, lacrimal canals, nasolacrimal duct, tear solution
- lacrimal glands
- located in superior-lateral corner of orbit -secrete tear solution onto surface of conjunctiva (ocular) --tear solution flows toward medial canthus
- lacrimal canals
- (2) -open above and below the caruncle -drain tear solution into lacrimal sac
- nasolacrimal duct
- receives tear solution from lacrimal sac and drains solution into nasal cavity
- tear solution
- -derived from blood plasma -chemical composition nearly the same as blood plasma except very little protein present
- tear solution function
- contains lysozyme (enzyme) - antibacterial destroys bacteria that may get onto surface of eye; also lubricates and keeps conjunctiva moist
- physiology of vision requirements
- -image focused on retina -rods & cones react photochemically to light rays -optic nerve transmits APs to cerebral cortex (occipital lobe) -visual interpretation center - interprets impulses
- far vision - lens focus
- object > 20 ft away from eye surface and light rays are parallel -ciliary muscles : relaxed -choroid coat : normal position -tension exerted on suspensory ligament, lens has a low curvature (flattened)
- near vision - lens focus
- object < 20 ft away from eye surface; light rays are divergent -ciliary muscles contract -choroid (ciliary body) pulled forward -decreased tension on suspensory ligament: lens becomes rounded or more convex (increased curve) because of elasticity; image focused = accommodation
- aberrations
- emmetropia: normal eye; no defects; far vision ametropia: eye with optical defects
- ametropia
- myopia (nearsightedness) hyperopia or hypermetropia (farsightedness) astigmatism cataract presbyopia
- myopia (nearsightedness)
- image is focused in vitreous humor of retina -causes: eyeball too long in ant-post plane -refractie power of lens or cornea is too great (image focused before retina, blurry)
- hyperopia or hypermetropia (farsightedness)
- image is focused in an imaginary plane behind the retina when an object is > 20 ft away from the surface of the eye -causes: eyeball is too short in the ant-post plane or refractive power of the lens or cornea is too weak
- astigmatism
- curvature of lens or cornea is imperfect -result is an image having more than one focal point (part of image is focused and part of it is blurred at the same time)
- cataract
- protein (crystalline) in lens have become denatured, and lens is cloudy (opaque) and not clear -light rays are diffracted and image appears too light during daylight and halos appear around lights during darkness (when driving for instance)
- presbyopia
- older vision -near point of eye is the closest point to the eye at which an object can be focused, as object moves it is blurred -near point moves farther from eye surface with age (becomes inelastic) -greatest change age 45-50 reason: lens become less elastic with age and can no longer accommodate to near objects as it did previously
- stimulation of retina (rhodopsin cycle)
- -rods contain rhodopsin or 11-cis-rhodopsin -composed of opsin (protein) and 11-cis-retinal (vitamin A) -referred to as visual purple or A photopigment -rhodopsin cycle: creates APs that are sent to the brain for interpretation under very dim light circumstances such as during night time or entering a movie theater after the show has begun
- core stimulation of the retina
- 3 types of cones & primary colors: -cholorolabe: green -cyanolabe: blue -erythrolabe: red ~different types of cones respond to different colors of light in retina
- separation and recombination of colors
- 1) red -> erythrolabe (create APs and send to) -> brain 2) blue -> cyanolabe (create APs and send to ) -> brain #1 and #2 = purple to occipital lobe in brain
- auditory and equilibrium senses
- derived from the auditory-vestibular apparatus (in temporal bone)
- external ear
- pinna, ear lobe, external auditory meatus
- pinna (auricle)
- an external appendage made of elastic cartilage and is covered by skin -Function: directs sound waves to external auditory meatus/canal
- ear lobe
- composed of adipose, vascular connective tissues (no real function)
- external auditory meatus (ear canal)
- -tube that extends from the pinna to the opening into middle ear -opening is covered by tympanum (eardrum or tympanic membrane) the boundary between outer and middle ears
- middle ear
- ear ossicles, incus, openings
- ear ossicles
- located in the middle ear cavity, smallest bones in the head; non structural, involved in picking up sensory stimuli -malleus, incus, stapes
- malleus
- (hammer) -attached to tympanum -articulates with incus (anvil)
- incus
- (anvil) -articulates with the stapes (stirrup)
- stapes
- (stirrup) attaches to oval window membrane
- openings
- external auditory meatus, oval and round windows, mastoid sinuses, eustachian tube
- external auditory meatus
- terminates with tympanum
- oval and round windows
- covered by membranes
- mastoid sinuses
- (cells) infected -> middle ear infected in mastoid process
- eustachian tube (auditory tube)
- connects middle ear to nasopharynx (upper throat) -function: equilibrates air pressure on both sides of the tympanum -gateway for middle ear infection from throat - more common infection than mastoid
- inner ear
- bony and membranous labryinths -location: in petrous portion of temporal lobe -bony (osseus) labyrinth: hallowed out portion of temporal bone -membranous labyrinth: membrane structures very similar to and located inside bony labyrinth
- bony labyrinth
- -semicircular canals -vestibule -cochlea: scala vestibule, scala timpani (separated by scala media)
- membranous labyrinth
- -semicircular ducts -utricle and saccule -cochlear duct or scala media