Cogs 107B A01: Monday 2pm Ricardo Trujillo ratrujil@ucsd.edu
The Basics Email: ratrujil@ucsd.edu Office Hours: Thursdays 11am-12pm, Mandeville Coffee Cart Sections are not mandatory, but strongly recommended No section Monday, January 15 You can attend other sections or come to my office hours In each of my sections, I will be covering the previous week s material
Class Schedule MLK Jr. Holiday: No section January 15th Midterm 1: February 1st Presidents Day Holiday: No section February 19 As this is the section before the midterm, I STRONGLY suggest you attend a different section Midterm 2: February 22nd Final: March 15th
Week 1 material Tuesday (1/9) Key topics: the neuron doctrine, the law of dynamic polarization, brain potentials, levels of analysis, the knee jerk reflex Vocab: membrane potential, synaptic potential, Action Potentials, ion selectivity, gating, kinetics, state, distribution
What is systems neuroscience? Levels of analysis
The neuron doctrine The neuron is the structural and functional unit of the nervous system Santiago Ramon y Cajal s doctrine recognizes neurons as discrete, individual cells. Clearly saw that each neuron had a soma, an axon, and dendrites Instead of being one large cell mass, singular neurons interact with each other The law of dynamic polarization: Neurons pass information unidirectionally (from dendrites to axon terminal). Not necessarily true, but true on most occasions
properties of ion channels: *ion selectivity e.g., Na+, Ca++, K+, Cl- *gating e.g., by voltage, ligand *kinetics e.g., open-time *state e.g., activated, inactivated, deinactivated, persistent *distribution e.g., in dendrites, at axon hillock
Week 1 material Thursday (1/11) Key topics: Topographic representation Vocab: Penfield homunculus (sensory and motor), mechanoreception, all-axon ganglion cell, merkel disk receptor, hair receptor, pacinian corpuscle, meissner corpuscle, barrel, transient, sustained
Topographic maps and the Penfield homunculus How much of the motor/sensory cortices represent which parts of your body. In rats, the whiskers are widely represented in the somatosensory cortex (as shown by the barrels in its topographic map)
two-point discrimination = Merkl disk density
proprioception and touch sense: the all-axon ganglion cell Unmyelinated tip The physical bending of this tip allows for the neurotransmitters to open the sodium ion channels, thus allowing for the entrance of sodium ion. This creates the generator potential, the action potential, and so forth. Note: This isn t an electrical occurrence, but a physical one All axon Generator potentials create the action potentials that travel along the axon They do not follow the all or none rule Action potentials are discrete, generator potentials are continuous
excitatory response = more AP s inhibitory response = fewer AP s excitatory response = no change in AP rate response fields small versus large response fields inhibitory surround complete vs. incomplete
mechanoreceptors type RA / SA depth response field sensitivity info. processed/best stimulus Pacinian RA deep very large (hand) very high (10 nm) high-freq. vibration Meissner RA shallow 3-5 mm slip / low-freq. vibration Merkl SA shallow spotty 2-3 mm broad depth range form, texture / points, edges (0.5 mm) hair RA deep 10 mm 1 micron hair displacement RA: rapid adapting SA: slow adapting
Crossover dorsal root ganglion pathways to the brain
S1: direction-selective surround inhibition
S2 response fields expand across digits, but maintain directional selectivity
Week 2 material Tuesday (1/16) Key topics: the neuron doctrine, the law of dynamic polarization, the knee jerk reflex Vocab: proprioception, vestibular, extrafusal muscle fiber, intrafusal fiber, muscle spindle afferent, gamma neuron, (contract vs. stretch), transient (RA), persistent (SA), afferent, efferent
Proprioception -joint-protecting reflexes (e.g., knee-jerk) -adjustment of muscle contraction / recruitment - Recruitment: to get more muscles to work together in a more strenuous task -kinesthesia: detection of body position and movement -coordination of motor commands -sense of self
The all-axon ganglion cell Many neural systems involve the DRG cells (somatosensory,vestibular, proprioceptive, etc.) Physical disturbance of unmyelinated tip causes generator potential Causes action potential to run along axon 4 different ways so far: Pacinian, meissner, merkl, and hair Now muscle spindle afferent and Golgi tendon organ
a simple proprioceptive circuit / system the knee-jerk reflex 1. Hammer hits patellar tendon 2. Stretching of quadricep muscle a. Stretching of intrafusal fibers b. Excitation of muscle spindle afferent 3. Afferent DRG cells send information to spinal cord a. Excitation of motor neuron causes quadriceps to flex b. Excitation of spinal interneuron causes an inhibition of motor neuron causes hamstring muscle to relax
Muscle Spindle Afferent Extrafusal muscle is what we usually think muscle is Intrafusal muscle is where the DRG cell innervation occurs - muscle spindle afferent Alpha motor neuron excites extrafusal muscles Intrafusal muscle Contractile, non-contractile, contractile DRG dendritic portion wrap around non-contractile portion Gamma motor fiber excites contractile portion
Muscle Spindle Afferent Activated by muscle elongation Ends contract and allow for the sensory fiber to send info out Stretch is modulated by contraction state of the muscle
Golgi Tendon Organ Dendritic portion of DRG cell branches out throughout tendon The Golgi Tendon Organ is connected to the muscle fibers, linking joints When extrafusal muscle is contracted, the organ is pulled and stretched, thus getting a flex of the joint
dorsal root ganglion pathways to the brain Segregation: Happens (even In Medulla) until S1 Crossover: Medulla Crossover: (medulla) Integration: S1 in cortex
somatosensory cortex: integration of proprioceptive and tactile information
using proprioceptive information: encoding of grasp postures in sub-region AIP of the posterior parietal cortex - PPC breaks up into multiple different subregions - Monkey reaches into container without seeing (to see how hand posture is going to allow for a successful grab). - Sensors all over arm to encode movements. Transpose movement into PCs to break movements into most important positions. - Lots of firing in certain phases depending on object (i.e. cue and move phases). - Thinking about concepts and doing it are both in PPC.
the Pinocchio effect the Pinocchio effect
Week 2 material Thursday (1/18) Key topics: The vestibular system Vocab: inner ear, hair cell receptor, vestibular organ, cupula, endolymph, otolith organ, semicircular canals, utricle, saccule, head direction cell, dorsal tegmental nucleus
Functions of the Vestibular System Postural reflexes Gaze adjustment Assessment of self motion A reason not to drink too heavily nor drink and drive
The Hair Cell Receptor Transduces both head motion (vestibular) and sound waves (auditory) Transfers mechanical movement into electrical signals Anatomy: Body of cell embedded in supporting cell From short to long, the stereocilia lead into the kinocilium like dominos Hair is connected by tendrils When moved, the ion channels are physically pulled open to let in glutamate Short to long: depolarization Long to short: hyperpolarization
The Vestibular Organ Semicircular canal Hair cells are encased in the cupula, which floats in the endolymph Registers rotational velocity Semicircular canal Otolith organ Utricle: Responds horizontal movement Utricle Saccule: Responds to vertical movement Saccule
The Vestibular Organ Semicircular canal Transient Otolith organ Imagine a glass of water: A change only happens when you re moving in a different direction Persistent Imagine it as if you re in a speeding car: the car moves forward while you persistently get pressed back
1. Detection of rotational movement 2. Inhibition (or excitation) of extraocular muscles on left (or right) side 3. Eye movement: In this case, the excitation of the M. rectus medialis and the inhibition of the M. rectus lateralis causes the eyes to look left the vestibulo-ocular reflex Note: Right output goes to left input and vice versa 2 1 3
integrating vestibular signals the head-direction neuron The most robust, uniquely tuned neuron found throughout the brain Relative not to body, but your positioning in the world For each head direction ( ), there are cells that specifically prefer that direction Dorsal Tegmental Nucleus: integrates signaling from otolith organ and semicircular canal
Resource Questions! (Find them on the website)
The action potential and synaptic potential are actually very special cases of the membrane potential True False
The action potential and synaptic potential are actually very special cases of the membrane potential True False
Name 3 properties of ion channels
Name 3 properties of ion channels 1. Gating 2. Distribution 3. Ion Selectivity 4. Kinetics 5. State
The neurotransmitter GABA: A. Is inhibitory B. Opens CI- channels C. Is excitatory D. Is a neuromodulator E. Depolarizes post-synaptic targets F. A and B G. C and E
The neurotransmitter GABA: A. Is inhibitory B. Opens CI- channels C. Is excitatory D. Is a neuromodulator E. Depolarizes post-synaptic targets F. A and B G. C and E
The Pinocchio effect involves a resolution of contradictory information supplied by which two sensory systems of the brain?
The Pinocchio effect involves a resolution of contradictory information supplied by which two sensory systems of the brain? Somatosensory and proprioceptive
Generator potentials are analogous to [synaptic/action] potentials
Generator potentials are analogous to [synaptic/action] potentials
Miscroslip events are best detected by the of touch receptor
Miscroslip events are best detected by the Meissner Corpuscle of touch receptor