Mod 2 Neuro and Electrophysiology
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Location and funtion of the 4 lobes of the cerebral hemisphere.
Primary Sensory is TOP, Frontal is motor
What are the 3 components of the brainstem? What are some of the important functions?
Important function: cranial nerve 3-8; resp and cardio function; both visceral and somatic sensory and motor
What kind of sensory information does the cerebellum integrate?
- planning movements
- accurate movements (simple/skilled)
- learning new skilled movements
- postural adjustment
Which spinal nerves have somatic (motor and sensory) and which ones have visceral (motor and sensory) innervation?
- T1-L2 and S2-S4: visceral
- All segments: somatic
What are the three meninges from outer to inner?
- Dura mater (two layers - outer (periosteal) layer and inner (meningeal) layer)
- Arachnoid mater
- pia mater
Describe the major input pathways to the CNS
- Skeletal muscle and other sensation: both cranial and spinal nerves.
- Special senses:
- 1) Olfaction and vision to cerebral hemisphere via CN's
- 2) Taste and hearing and balance to brainstem via CN's
Describe the major output pathways from the CNS
- somatic motor: Brainstem (via CN's) and all spinal nerves
- visceral motor: Cranial nerves III, VII, IX, X; spinal nerves T1-L2 and S2-S4
What are the cranial nerves involved in the parasympathetic nervous system?
- Oculomotor Nerve (III): pupil and lens
- Facial Nerve (VII): salivation and lacrimation (crying)
- Glossopharyngeal Nerve (IX): salivation
- Vagus Nerve (X): Thoracic and abdominal viscera; heart and lungs
Where does visceral sensory information travel?
- Visceral pain: sympathetic fibres ONLY
- Cardio and resp sensory info: CN's IX and X
- Other types of sensory info (distension, emptiness, etc) via both symp and parasymp
Where does the visceral sensation from CN's IX and X ender the brainstem?
The NTS, the nucleus tractus solitarius.
What are the three divisions of the motor-specific cerebrum
- Supplementary motor area: Program complex series of movements
- Primary motor cortex: execution, force, and direction of movement
- Premotor cortex: integration of visual and sensory cues
What are the brain areas comprising the medial and lateral motor systems?
- Lateral: cerebral cortex - lateral corticospinal (appendicular musculature controlled)
- Medial: brainstem and cerebral cortex (appendicular musculature controlled)
What are the three subdivisions of the cerebellum and what motor system are they in?
- Vestibulocerebellum (medial MS): balance, vestibulo-ocular reflex
- Spinocerebellum (lateral MS): coordination of muscles, ongoing movement
- Pontocerebellum (lateral MS): motor planning
Compare and contrast enteroceptors, proprioceptors, and exteroceptors
- Enteroceptors: Sense the internal environment (e.g. nociceptors)
- Proprioceptors: sense length or tension in space, give positional information, (e.g. GTO)
- Exteroceptors: Sense the external environment (e.g. thermo receptors)
Describe the structures muscle spindle and GTO
- Muscle spindle: intrafusal muscle with nerve ending wrapped around it all wrapped up in a CT sheath.
- GTO: Specialized nerve endings which become intertwined with the collagen bundles of the tendon.
How does the myotatic reflex work? How is the monosynaptic reflex related to this?
- 1) muscle is stretched by hammer (strong spindle signal)
- 2) singals directly to motor neurons (big Ia afferent synapses directly with alpha motor neurons)
- 3) inhibitory interneurons are also stimulated for the opposing muscle groups
- 4) muscle contracts in the stretched muscles and opposing muscle groups remain relaxed.
monosynaptic reflex is the same bit without the inhibitory interneurons to the opposing muscle group
How does the withdrawl reflex work? Use the example of stepping on a nail with right foot.
- 1) nociceptors (A delta or C afferent fibres) travel into the spinal cord
- 2) On right thigh: flexors are activated and extensors are inhibited.
- On left thigh: extensors are activated and flexors are inhibited
- 3) move away from painful stimulus.
What do neural crest cells differentiate into (list 5)?
- Cranial nerve ganglia
- Dorsal root ganglia (MOST IMPORTANT)
- Sympathetic trunk and pre-aortic ganglia
- Parasymp. ganglia of the GI tract
- Adrenal Medulla
- Schwann Cells
- Glial cells
What are the three layers of the developing spinal cord and what do the last two form?
- Mantle (grey matter)
- marginal (white matter)
What is the cause and potential symptoms of Anencephaly?
- - cause is the failure of the Cranial neural tube to close
- - skull cap fails to form
- - abnormal forebrain development
- - failure of fusion in other areas
What is the cause and potential symptoms of Spina Bifida?
- - Failure of the caudal neuropore to close
- -2 types:
- 1) SB Occulta
- failure of vertebral arches to fuse, common, tuft of hair
- 2) SB cystica
- a) meningocele: meninges protrude into sac
- b) meningomyelocele: spinal cord and meninges protrude into sac
- c) Myeloschisis: undeveloped neural tissue is full exposed (most severe)
How does carrier mediated transport work?
The solute acts as a ligand, causing a conformational change in the channel and allowing the solute to pass through
What are the intracellular and extracellular concentration of K+, Na+, Cl-, Ca++
- K+: extracellular (5 mM), intracellular (150 mM)
- Na+: extracellular (150 mM); intracellular (15mM)
- Ca++: extracellular (2 mM); intracellular (0.0002 mM)
- Cl-: extracellular (150 mM); intracellular (13 mM)
How does the Na+ and K+ ATPase pump work
- 3 sodium out
- 2 potassium in
- at the expense of 1 ATP
How does secondary transport work?
Uses energy in a concentration gradient to move a second solute.
What are 4 types of gated channels?
ligand gated; voltage gated, phosporylaation-gated, stretch (or pressure) gated
Name three methods through which voltage gated channels become inactivated (refrectory state)
- a certain level of depolarization
- A solute binds to them (e.g. calcium) after a certain amount of it is allowed to enter the cell
- The channel dephosphorylizes sometime after depolarization
What are the three states of the sodium channels?
- resting (ready to be activated)
- activated (when the membrane depolarizes)
- inactivated (if membrane depolarization persists), will only stop if repolarization "resets" the gates. stops the positive feedback loop that causes the steep rise in the action potential
- critical in setting the max firing frequency of neurons
What is saltatory conduction propagation?
The AP "skips" from node of ranvier to node of ranvier
What is the gate theory of pain?
- Nociceptive information in spinal cord is modulated by concomitant activation of large myelinated fibers associated
- with low-threshold mechanoreceptors.
How does the baroreflex work?
- 1) Stretch-sensitive channels in baroreceptors are opened (respond to increased BP)
- 2) baroreceptors fire faster if these channels are opened
- 3) carotid bodies take glossopharyngeal nerve to medulla and aortic bodies take vagus nerve to medulla
- 4) enter medulla at the nucleus tractus solitarii
- 5) decrease in sypmathetic activity in blood vessels (vasodilation) and vagus nerve releases ACh to slow SA firing rate
How does the pulmonary stretch (Hering-Bruer) reflex works?
- 1) slowly adapting stretch receptor from the thorax travels in the vagus nerve to the dorsal resp. group in the NTS
- 2) NTS exerts an inhibitory effect on the on the nerves responsible for stimulation of the diaphragm
- 3) NTS also inhibits the nucleus ambiguosus (NA) which will travel back down the vagus and decrease parasympathetic activity to the smooth muscles in lung.
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