January 19, 2010

Exam on Tue. of next week (8:30a), bring questions on exam this Thu.

notes in this color are additional info not covered in class.

Review on AP.

AP is all voltage versus chemical, post-synapse is both. Some leaks occur within the postsynaptic membrane due to chemical issues. Immediately after an action potential the cell is in the refactory period during which it registers the production of further action potentials. In the first part of this period, the absolute refactory period, the membrane cannot produce an action potential, regardless of the stimulation. Then the relative refactory period, a stronger than usual stimulus is necessary to initiate an action potential. Axon hillock is the swelling where the axon exits the soma.

When you think of the Reflexive Arc (see seperate post for this) think of the movie "Benchwarmers"

Glia provides:

• physical support
• protection for neurons
• control of nutrient flow
• facilitate neural communication
• synchronized neurl activity
• guide neural migration
• phagocytosis- the cleanup of damaged or dead areas

see image here for a break-down of AP. There is a 'war' between the EPSP and the IPSP for dominance in the resting potential. When the potential reaches the threshold (-35 mV) there will be an instantaneous rise in EPSP and an AP is fired.


Developmental categorization of the CNS

(from bottom of nervous system to top)

Myelencephalon- medulla oblengata - vital functions such as regulation of the cardiovascular system, breathing, and skeletal muscle tone ~maintaining blood pressure

Rhombencephalon "hindbrain" (shared between medulla and pons) cranial nerves

Metencephalon- pons -control of sleep and arousal
(inferior olivenucleus)
- cerebellum -involved in balance and motor control

Mesencephalon "midbrain" Tectum is the dorsal portion of midbrain. Superior & inferior colliculli are involved in the visual and auditory localization. Tegmentum in the portion of the midbrain located under the tectum and consists of the mezalimpic pathway:

• anterior end of the reticular formation
• periaqueductal gray- deals with pain
• Red Nucleus- motor movement
• Substantia nigra- movement
  

Diencephalon -thalamus -contains nuclei that recieve sensory information and transmits it to the cortex
-hypothalamus -contians nuclei involved in the four F's (fight, flight, feeding and..... mating), control fo the autonomic neruons system and pituitary.

Telencephalon - cerebral cortex -basal ganglia -limbic system Basal ganglia is responsible for repitition of behavior (like the song stuck in your head now, *see seperate post for brain functions)

(see 3-6 in coloring book for Formation of Spinal Cord)

Spinal Reflexes. When your knee jerks there is an AP afferant (input) message that goes to your spinal cord and tells your brain that you have just experienced a 'pain'. The AP (in blue) goes to your dorsal root ganglion inside the spinal cord and alerts the brain through the CNS. EPSP is sent to your motor neuron (red) to form an efferent (output) action to flex your muscle in response to the 'pain'. GABA (green) is introduced as the contract in muscle, or to make it stop moving. (see my personal notes if this doesn't make too much sense)

Vestubular System (terms not needed to know, also in txt book 7.3) within the saccule, one of the semi-circular canals, there exists the macula where our sense of bodily equilibrium (balance) lies. The hairs within the macula are submerged in a liquid that, when the liquid is sloshed around the movement of the hairs indicates that your head is either tilted or you are tilted due to too many ethenol beverages (alcohol). The hairs serve to aid your balance and detect movement.

Body sensory
-hairy skin and glabrous skin (hairless)
-layers of skin

• epidermis
• dermis
• subcutaneous tissue (a.k.a. hypodermis, fat)

-touch receptors-mechanoreceptors
-touch pathways

Four classes of sensory axons differ in size and speed. The larger the cable, the more electricity it sends. (do not need to know, see fig. 7.16)

Dermatomes related to dorsal roots (not routes, haha)
-Cervical
-Thoracic (which dinosaur belongs here? JK)
-Lumbar
-Sacral

Somatosensory Cortex (*fig. 7.18)
-medial lamniscous sensory pathway carries touch info to CNS.

In the medulla (myelencephalon), located above the cervical, two things occur within it. Synapse and decussation, a crossover like in the optic nerves (decussation occurs in the cuneate and gacilis nuclei).


After decussation(dee-kyu-zeh-shun), touch information is arranged spatially within the medial lemniscus. What does that mean? Who knows but the professor, so ask him.

medulla- touch info =>ipsilateral->contralateral ascending pathway.

The somatosensory cortex is located in the pariatal lobe, in which the somatosensory info is processed by the ventral prosterior and intralaminar nuclei of the thalamus.

Why the sulci you may ask? Well I did ask that question! haha! The reason why there are sulci or fissures, is so there will be more surface area for information to be processed, developed and sent. Remember the electric cables? Same thing, the larger the surface area the greater the conductivity.
______________________________________
words to know

sulcus/sulci
gyrus/gyri

interneurons= intralaminar of spinal cord
ipsilateral=same
contralateral=opposing