MEMORY CHECK 1: Consciousness, Anatomy & Function

Now, you may have to dig deep into the recesses of your brain, but remember the good ole RAS
(reticular activating system) – it’s the big boss of consciousness – keeps us awake! It ascends from the lower brain stem and projects throughout the cerebral cortex. The ability to respond to stimuli or arousal depends on an intact RAS in the brain stem and the ability to respond to the environment. Cognition relies on an intact cerebral cortex. Therefore, consciousness or responsiveness requires the reticular formation in the brain stem to the cerebral cortex. 

*  The central nervous system (CNS) consists of the brain and spinal cord encased within the meninges and bathed in cerebrospinal fluid (CSF). The brain is divided into several areas, including the cerebrum, midbrain, cerebellum, pons, and medulla oblongata. The midbrain, the medulla, and the pons comprise the brain stem.

*  The outer covering of the cerebrum is the cortex. The entire cerebrum is divided into two halves, or hemispheres, connected by a neural bridge, the corpus callosum, that coordinates activities between hemispheres. The cortex is concerned with thinking and sensory perception. Emotional responses and control of body temperature, water and food intake, and sex drive have their origin in the mid- brain area. The cerebellum primarily integrates muscular movements to produce coordination in walking, talking, and other complex muscular activities. The medulla oblongata controls vital functions such as respiration, heart rate, and blood pressure, although these are modified by higher brain centers.

*  Within the cerebral hemispheres are subdivisions, or lobes. The frontal lobe is located in the anterior portion of each hemisphere. The temporal lobe is located in the lower middle region of each hemi- sphere. The parietal lobe is the upper, rear portion. The occipital lobe is the lower, rear portion of each hemisphere. 

*  The basal ganglia are a collection of cell bodies in several areas of the brain's gray matter including the caudate nucleus, globus pallidus, putamen, and substantia nigra. The function of the basal ganglia is thought to involve the planning and programming of movement.

*  The cerebral cortex plays a major role in controlling precise, voluntary muscular movements. Motor output (stimulus) to skeletal muscles travels down the spinal cord in two types of descending tracts: the pyramidal tracts and the extrapyramidal tracts. The pyramidal tracts originate in the motor cortex and terminate in the brain stem. They cross to the opposite side at the medulla-spinal junction. The pyramidal tracts carry impulses causing precise, voluntary movements of skeletal muscles. The extrapyramidal tracts arise from the cortex and project to innervate the motor neurons. They do not cross to the opposite side. Extrapyramidal tracts carry nerve impulses that responsible for fine repetitive motor movements.

 
MemChk.Neuro.1.MdP