Mod 2 Neuro and Electrophysiology

Primary Sensory is TOP, Frontal is motor

• MPM!
• Midbrain
• Pons
• Medulla

Important function: cranial nerve 3-8; resp and cardio function; both visceral and somatic sensory and motor

• planning movements
• accurate movements (simple/skilled)
• learning new skilled movements
• postural adjustment

• T1-L2 and S2-S4: visceral 
• All segments: somatic

• Dura mater (two layers - outer (periosteal) layer and inner (meningeal) layer)
• Arachnoid mater
• pia mater

• 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

• 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

• 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

• 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

The NTS, the nucleus tractus solitarius.

• 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

• Lateral: cerebral cortex - lateral corticospinal (appendicular musculature controlled)
• Medial: brainstem and cerebral cortex (appendicular musculature controlled)

• Vestibulocerebellum (medial MS): balance, vestibulo-ocular reflex
• Spinocerebellum (lateral MS): coordination of muscles, ongoing movement
• Pontocerebellum (lateral MS): motor planning

• 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)

• 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.

• 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

• 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.

• 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
• Meninges

• Ventricular
• Mantle (grey matter)
• marginal (white matter)

• - 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

• - 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)

The solute acts as a ligand, causing a conformational change in the channel and allowing the solute to pass through

• 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)

• 3 sodium out
• 2 potassium in
• at the expense of 1 ATP

Uses energy in a concentration gradient to move a second solute.

ligand gated; voltage gated, phosporylaation-gated, stretch (or pressure) gated

• 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

• 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

The AP "skips" from node of ranvier to node of ranvier

• Nociceptive information in spinal cord is modulated by concomitant activation of large myelinated fibers associated
• with low-threshold mechanoreceptors. 

• 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

• 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.