EXSC 224 Lecture 7: Lecture 7 - 9/8

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University of South Carolina
Exercise Science
EXSC 224

● Cerebral white matter ○ Myelinated fibers and their tracts - come to or leave the cerebral hemispheres ○ Responsible for communication ■ Commissures ● Connects gray matter of the two hemispheres ● Different sets connecting the 2 hemispheres ● Most important is corpus callosum ● Know what happens when you sever the corpus callosum (epilepsy) etc. ■ Association fibers ● Connect different parts of the same hemisphere ● Connect gyri within the same hemisphere, and can be in different lobes ● Can connect the sensory to the prefrontal cortex ■ Projection fibers ● Corona radiata ● Connect the hemispheres with lower brain or spinal cord ● Ascending and descending neurons ● Going to and from the cortex of the cerebral hemisphere ● Associated with either primary motor or primary sensory area ○ Motor are super long ○ Sensory are pretty short - project from thalamus to primary sensory cortex ○ Basal Nuclei (Ganglia) ■ Associated with the cerebrum ■ Subcortical nuclei ■ Functionally associated with the subthalamic nuclei (diencephalon) and the substantia nigra (midbrain) ■ Regions work together and play a role in motor function ● Cyclic motor pattern - walking ● It is in step with receiving information that then is relayed from cerebellum to premotor cortex ○ Proprioception - body awareness, where you are, how fast you’re moving, balance ■ Ganglia are clusters of neurons in the PNS ■ Nuclei are clusters of neurons in the CNS ■ Stratum - ● Caudate nucleus (and tail) ● Putamen (body) ● Functions of Basal Nuclei ○ Though somewhat elusive, the following are thought to be functions of basal nuclei - ■ Influence muscular control ■ Help regulate attention and cognition ■ Regulate intensity of slow or stereotyped movements ■ Inhibit antagonistic and unnecessary movements ^^ end of ppt lecture 5 ● Diencephalon - sits between old brain and new brain ○ Three paired structures ■ 1. Thalamus ● Largest ● Relay station ■ 2. Hypothalamus ● Key regulatory site ■ 3. Epithalamus ● Pineal Gland ○ Encloses the third ventricle ● 1. Thalamus - relay station ○ Made up of a cluster of different small nuclei ■ Each nuclei has a different function ○ Relay sensory info and send it to appropriate region ○ Act as a filter - if info coming in is not very strong, it might not get passed along ■ editing/filtering ○ ALL SENSORY INFORMATION PASSES THROUGH THE THALAMUS BEFORE IT GOES TO THE CORTEX ■ *except proprioception always goes to the cerebellum first before going to thalamus and then basal nuclei* ● Hypothalamus - important ○ Also made up of different nuclei with specific function ○ The master regulator of body functions ○ “Key regulator of the autonomic nervous system’ ○ Startled reflex passes through hypothalamus, it makes your heart rate go up ○ Increase sympathetic activity (fight or flight) ○ Decreased parasympathetic activity (rest and digest) ○ Associated with limbic association area ● Hypothalamic function ○ Autonomic control center for many visceral functions ■ Blood pressure ■ Heartbeat rate ■ Heartbeat force ■ Digestive tract mobility ○ Center for emotional response (limbic) ■ Involved in perception of pleasure, fear, and rage ■ In biological rhythms and drives ○ Regulates body temperature, food intake, water balance, and thirst ■ Sweat glands, enlarged veins when hot ○ Regulates sleep and the sleep cycle (so does epithalamus) ■ Hypothalamus causes you to wake up due to secretion of hormone cortisol ○ Controls release of hormones by the anterior pituitary ○ Produces posterior pituitary hormones (huge number of hormones) ○ Hypothalamus endocrine gland as well as neuronal tissue ● Epithalamus ○ Pineal gland - endocrine gland that secretes melatonin ■ Extends from the posterior border and secretes melatonin ■ Sleep wake cycles are controlled by epi and hypo thalamus ■ Epithalamus hormone (melatonin) makes you tired ○ Most dorsal portion of the diencephalon; forms roof of the third ventricle Brain stem ● Three regions: ○ 1. Midbrain ○ 2. Pons ○ 3. Medulla oblongata ● Midbain - study structures here ○ Cerebral peduncles ■ Contain pyramidal motor tracts ■ Carries MOTOR projection fibers ■ Superior - travelling from cerebellum and sends info up to the thalamus ○ Cerebral aqueduct ■ Channel between third and fourth ventricles ○ Corpora quadrigemina - study this ■ Reflex centers ■ Superior portion is a reflex center for eyes ■ Inferior is auditory ● Pons ○ Forms part of the anterior wall of the fourth ventricle ○ Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial) ○ Some nuclei of the reticular formation ○ Nuclei that help maintain normal rhythm of breathing ■ Adjusts breathing, but does not initiate ■ Smoothes out breathing ○ Know reticular formation ■ Nuclei close to the fourth ventricle ■ Basic function - alertness, general cerebral arousal ○ Descending motor info from cerebral peduncles enters into pons where we refer to them as pyramidal tracts ■ The SAME axon, but a different physical region of it ○ Know medial lemniscus - nuclei within the pons ■ Associated with ascending/ afferent sensory information ○ Know fibers of pyramidal tract ● Medulla Oblongata - autonomic reflex centers ○ Cardiovascular center ■ Heart rate/ force ■ Blood vessel diameter ■ Neurons in brainstem that give rise to sympathetic nervous system ■ Regulates blood pressure ○ Respiratory centers ■ Generate respiratory rhythm ■ Control rate and depth of breathing, with pontine centers ■ Breathing originates in medulla ○ Additional (reflex) centers regulate: ■ Vomiting ■ Hiccuping ■ Swallowing ■ Coughing ■ Sneezing ○ Know pyramids - two central longitudinal ridges formed by py
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