Untitled Flashcards Set

Unit 3 Learning Objectives For Exam 1

-              Before you begin  items bolded AND underlined are the absolute key/core concepts I expect to be memorized

-              underlined  2^nd level priority, key for conceptual understanding

-              Regular text  3^rd level priority, not as crucial for understanding do not spend as much time on this.

-              Nociceptor specifics will not be on this exam

Lecture 1

1.        Action potentials

a.        Resting membrane potential, threshold potential,

                                                                                             i.         RMP = -70mv

                                                                                          ii.         Threshold potential = -55mv

                                                                                       iii.         Negative to less negative = depolarization till about +10mv

1.        Na+ rushing into the cell

                                                                                       iv.         Peak = K+ channels opening and slowly leaving the cell

1.        Becoming more negative = repolarization

                                                                                          v.         Overshoot = more negative than the RMP due to the slow closing of those K+ channels

b.        Role of NA/K Pump

                                                                                             i.         Actively transporting 3 Na+ out of the cell and 2 K+ into the cell using energy from ATP

                                                                                          ii.         Creates an electrochemical gradient

c.        Glutamate and GABA

                                                                                             i.         Glutamate = primary excitatory NS

                                                                                          ii.         GABA = primary inhibitory NS

2.        Sensory Receptors

a.        List all the receptor types and what stimuli they respond to

                                                                                             i.         Chemoreceptors: transduces chemical substances into biological signals, detect changes in normal environment

1.        Internal peripheral: detect chemical changes in blood

a.        Carotid bodies detect an increase in CO2 in blood

b.        Chemical  action potential

2.        Distance: sense of smell where you aren’t directly interacting with the substance

a.        Detect chemicals in gaseous states (odors and pheromones)

3.        Direct: requires direct interaction with the chemical’s source – tastebuds

a.        Taste doesn’t adapt as quickly whereas smell does

b.        Dorsal respiratory group = inspiration

c.        Ventral respiratory group = stimulates DRG for non-normal respiration

d.        Pneumotaxic = turns off DRG

4.        Peripheral chemoreceptors = internal

a.        Carotid and aortic bodies

                                                                                                                                                                                                         i.         Sense partial CO2 and O2 pressure

                                                                                                                                                                                                      ii.         Sense pH in blood

5.        Central chemoreceptors

a.        Within ventral medulla

b.        Sense pH in CSF

                                                                                          ii.         Photoreceptors: transduce light into biological signals (best transduction = vision)

1.        Rods: sensitive to light, scotopic (dim) vision

2.        Cones: rapid responses to variations in light intensity, photopic (bright) vision, color vision and visual acuity

a.        Less cones than there are rods, which shows how good they are at producing imaging

b.        Concentrated in the macula and fovea

3.        Intrinsically photosensitive retinal ganglion cells

a.        Play a role in circadian rhythm and the pupillary reflex

4.        Destroyed distally via phagocytosis

5.        Produced proximally via morphogenesis

                                                                                       iii.         Thermoreceptors

                                                                                       iv.         Mechanoreceptors

                                                                                          v.         Proprioceptors

                                                                                       vi.         Nociceptors

b.         Common receptors responsible for regulation of homeostatic variables such as BP, blood plasma chemical concentrations

                                                                                             i.         Chemoreceptor’s cardiac function

1.        Cardiac center medulla  controls HR

2.        Baroreceptors  detects pressure from decrease O2, increase CO2, and decrease pH

3.        Heart rate

4.        Vasodilation/vasoconstriction

Lecture 2

1.        Vision

a.        name of receptors, specific proteins involved

                                                                                             i.         Rods

1.        Has both retinal and opsin primary proteins

2.        Retinal + opsin = Rhodopsin proteins

                                                                                          ii.         Cones

1.        Different type of opsin proteins = Photopsin proteins

                                                                                       iii.         which are involved in low light situations and which are involved with color vision?

1.        Rods = low light conditions

2.        Cones = color vision

b.        what makes the vision sensory transduction process unique from other sensory transduction processes?

                                                                                             i.         Phototransduction cascade

1.        Opsin in disk membrane absorbs photon  causes change of configuration of the 3D structure  unstable intermediates activate transducin protein

                                                                                          ii.         Stimulus = light photons

c.        What colors of cones do humans possess?

                                                                                             i.         S = Blue, M = green, L = red, and black

d.        What determines what color we see when we only have 3 “color” cones?

                                                                                             i.         Receptor output signal is proportional to the number of photons absorbed

1.        Estimation of wavelength  color vision

2.        Specific to a wavelength

2.        Temperature

a.        Temperature change vs absolute temperature

                                                                                             i.         “non-specialized” receptor that codes relative changes in temp

1.        We’re used to relative changes whereas not good at absolute temperature

b.        Receptors involved

                                                                                             i.         Warm receptors

                                                                                          ii.         Cold receptors

c.        Receptors involved in nociception of temperature

d.        Temperature change transduction pathway

                                                                                             i.         Warm receptors

1.        Increase in warming  increase in AP firing rate, decrease in warming  decrease in AP firing rate

                                                                                          ii.         Cold receptors

1.        Increase in cooling  increase in AP firing rate, decrease in cooling  decrease in AP firing rate

Lecture 3

1.        Major categories of mechanoreceptors

a.        Merkel’s disk

b.        Meissner’s corpuscle

c.        Ruffini endings

d.        Pacinian corpuscles

                                                                                             i.         Stimuli for each type

1.        Merkel’s disk = pressure and texture

2.        Meissner’s corpuscle = light touch and vibration

3.        Ruffini endings = stretch and pressure

4.        Pacinian corpuscles = deep pressure and vibration

                                                                                          ii.         Slow vs Fast adapting

1.        Slow adapting

a.        “tonic”, fire continuously when a stimulus is present, crucial for providing info about constantly present stimuli, skin stretch, muscle tension, Ruffini endings and GTOs

2.        Fast adapting

a.        “phasic”, rapid initial response to stimulus, firing rate quickly decreases and eventually stops even if stimulus persists, sensitive to changes in stimulus, fine touch, movement, vibration, Meissner’s corpuscles, and Pacinian corpuscles

2.        Minor categories

a.        Hair nerve fibers

b.        Free nerve endings

3.        Types of skin and unique characteristics important for sensation

a.        Glabrous

                                                                                             i.         Mostly meissner’s corpuscles, but also has Pacinian corpuscles, Merkel’s disks, and Ruffini endings

                                                                                          ii.         Concentrated in fine touch areas  fingers, palms, soles

                                                                                       iii.         More sensitive than hairy and is involved in detailed, tactile sensation

b.        Hairy

                                                                                             i.         Less specialized for detailed tactile perception

                                                                                          ii.         Fewer touch receptors

                                                                                       iii.         Hair nerve, free nerve endings, and ruffini endings

4.        Transduction pathway for Meissner Corpuscles

a.        Involves light touch or vibrations converting into electrical signals

                                                                                            i.         External force  physical deformation of lamellae  bending of nerve axon terminals  action potential  nerve  dorsal root ganglion  dorsal column of spinal cord  medulla (decussation)  thalamus  S1  FEEL

1.        What nuclei in the thalamus?

a.        VPL – receives sensory input related to the body

2.        What white matter tract from the Thalamus to S1?

Lecture 4

1.        Definitions of Proprioception and kinesthesia

a.        Proprioception is the sense of position and movement of the body including forces and loads applied to the body

                                                                                             i.         Not in isolation but they integrate other senses at the same time including touch, vision, and vestibular

1.        Active joint position: you are moving your own arm

2.        Passive joint position: someone else moving it

                                                                                          ii.         Two basic categories (all get info from joint capsule, ligaments, muscles, tendons, skin and get sent to the brain) = redundancy

1.        Sense of force  effort, heaviness, tension

a.        Reproduce and match desired level of force

2.        Sense of change in velocity

a.        Detects vibration of oscillating objects

b.        Kinesthesia is active but during movement

                                                                                             i.         Awareness of motion

1.        Duration, direction, amplitude or size, speed, acceleration

2.        Muscle Spindles vs. Golgi Tendon Organs (GTO)

a.        Similarities and differences

                                                                                             i.         Muscle spindles = spindle like

1.        Intrafusal fibers = not contractile, no tension

a.        Nuclear bag = absolute center of muscle spindle

                                                                                                                                                                                                         i.         type of intrafusal fiber

                                                                                                                                                                                                      ii.         many nuclei in bags

                                                                                                                                                                                                   iii.         cause excitation of sensory fibers

1.        dynamic nuclear bag = fast contraction speed

2.        static nuclear bag = slow contraction speed

                                                                                                                                                                                                   iv.         sensitive to length changes

b.        Nuclear chain = nuclei aligned in chain, wrapped around intrafusal fiber

                                                                                                                                                                                                         i.         Type of intrafusal fiber

                                                                                                                                                                                                      ii.         Excites secondary nerve

                                                                                                                                                                                                   iii.         Half the size of bag fibers

1.        Measures stress and strain on muscle

2.        Spring “stretch of spring”

2.        Extrafusal fibers = contractive, tension

                                                                                          ii.         Golgi Tendon Organs

b.        Functions

c.        Roles in proprioception and kinesthesia

                                                                                             i.         Muscle spindles = muscle length

                                                                                          ii.         Golgi tendon organ = tension

3.        Muscle Spindle Specifics

a.        Intrafusal vs extrafusal fibers

1.        Intrafusal fibers = not contractile, no tension

a.        Nuclear bag = absolute center of muscle spindle

                                                                                                                                                                                                         i.         type of intrafusal fiber

                                                                                                                                                                                                      ii.         many nuclei in bags

                                                                                                                                                                                                   iii.         cause excitation of sensory fibers

1.        dynamic nuclear bag = fast contraction speed

2.        static nuclear bag = slow contraction speed

                                                                                                                                                                                                   iv.         sensitive to length changes

b.        Nuclear chain = nuclei aligned in chain, wrapped around intrafusal fiber

                                                                                                                                                                                                         i.         Type of intrafusal fiber

                                                                                                                                                                                                      ii.         Excites secondary nerve

                                                                                                                                                                                                   iii.         Half the size of bag fibers

1.        Measures stress and strain on muscle

2.        Spring “stretch of spring”

2.        Extrafusal fibers = contractive, tension

b.        α and γ motor neurons

                                                                                             i.         y gamma motor neurons

1.        don’t “contract” the muscle

2.        adjusting stretch sensitivity by contracting intrafusal fibers

3.        keeps the spindle tight

4.        allows a motor neuron to continually fire and contract muscle

5.        release acetylcholine  intrafusal fibers open  Na2+ influx  depolarization  increased stretch sensitivity of spindle afferents

6.        do not contribute to force of muscle/extrafusal contraction

                                                                                          ii.         a alpha motor neurons

1.        cause muscle contraction

c.        sensory components (group 1 vs 2 afferents)

                                                                                             i.         1a afferent = large diameter, spiral around intrafusal fibers, middle of spindle

                                                                                          ii.         II afferent = medium diameter, lateral on chain fibers

1.        Afferent stretch info via mechanically gated on channels

2.        Bag2 and chain fibers increase firing rate on these two at a given muscle length

3.        Bag1 increase stretch sensitivity of 1a afferents

d.        α - γ coactivation hypothesis

                                                                                             i.         during voluntary muscle contractions, both a and y motor neurons are activated simultaneously to maintain the sensitivity of the muscle spindle

                                                                                          ii.         ensures that the muscle spindle remains sensitive to changes in muscle length, even during contraction

4.        GTO specifics

a.        Spindles have y motor neurons, no motor innervation

b.        Mechanically activated by muscle-tendon unit

                                                                                             i.         Group 1b afferents

1.        Thinner than 1a, myelinated, still high conduction velocity

2.        Reflexive control with spinal

3.        Reciprocal innervation when too much force

4.        Relaxation of contracting muscle and contraction of antagonist

5.        Protects against overstraining the muscle / tendon

                                                                                          ii.         how does it get activated?

1.        High tension from voluntary contractions or external forces acting on the muscle

                                                                                       iii.         GT reflex afferent and efferent pathways

1.        Muscle generates force  sensory terminals compress  stretch sensitive channels open  action potential  spinal cord  reflex and brain

2.        Golgi tendon senses excessive tension  sensory neuron conducts action potential  sensory neurons synapse with interneurons  a motor neurons to quads is inhibited while the hamstring is stimulated  hamstring contracts and the quads relax

3.        Muscle contraction (afferent pathway)  activation of GTO  sensory signal sent to SC  spinal cord integration  inhibition of agonist muscle (efferent pathway)  activation of antagonist muscle  reflex

a.        What is the purpose?

                                                                                                                                                                                                         i.         Protection