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1. Peripheral Nervous System (PNS) - the section of the nervous system lying outside the brain & spinal cord.
2. Central Nervous System (CNS)
Subdivisions of PNS
- Somatic nervous system, consciously controlled.
- Afferent (sensory) fibers
- Efferent (motor) fibers
- Autonomic nervous system (ANS), Also categorized as part of the "emotional" nervous system.
- Sympathetic division (arousal)
- Parasympathetic division (calm)
CNS - Control Centers
Cortex - One of the major components of the brain. The cortex is divided into four lobes (frontal, parietal, temporal, occipital). It also contains the sensory and motor areas. It is the outer layer of gray matter that covers the surface of the cerebral hemisphere. It is involved in higher brain functions (also referred to as cortical processes) including visual processing.
Ψ The Four lobes of the Brain
• Frontal lobe - The largest area of the brain that lies in the front of the cranial cavity.
It is important for control of voluntary movement or activity, cognition & feelings.
• The frontal lobe contains the primary motor cortex (somatomotor cortex), i.e., the portion of the human brain directly responsible for the movement & exchange of sense & motor information (namely touch: sensitivity, cold, heat, pain etc.) of the rest of the body.
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• A cortical homunculus (ho-MONK-you-luss) is a physical representation of the primary motor cortex. The resulting image is a grotesquely disfigured human with disproportionately huge hands, lips, & face in comparison to the rest of the body. Because of the fine motor skills & sense nerves found in these particular parts of the body they are represented as being larger on the homunculus. A part of the body with fewer sensory and/or motor connections to the brain is represented to appear smaller. The homunculus is a visual representation of the concept of "the body within the brain" that one's hand or face exists as much as a series of nerve structures or a "neuron concept" as it does a physical form. This concept relates to many neuro-biological phenomena including "phantom limb" & "body integrity identity disorder".
• Because the frontal lobes are involved in paying attention, organizing, deciding, & carrying out thoughts & social-emotional behaviors, they are said to have an executive function.
• Parietal lobe - Area of the brain that lies in front of the occipital lobe that is important in processing information from the sense of touch & bringing together sensory information.
• The somatosensory cortex is a narrow strip of cortex located on the front edge of the parietal lobe & extends down its side. Like other sensory areas, there is a map of sensory space called a homunculus in this location. For the primary somatosensory cortex, this is called the sensory homunculus. Areas of this part of the human brain map to certain areas of the body, dependent on the amount or importance of somatosensory input from that area. For example, there is a large area of cortex devoted to sensation in the hands, while the back has a much smaller area.
• The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense & navigation. It is involved in language abilities such as writing & speaking a second language.
• Temporal lobe - Primary auditory cortex and auditory association area
Aphasia is the inability to use or understand language (spoken or written) because of
a brain lesion.
- Broca's area & Broca's aphasia - affects speech but not understanding.
- Wernicke's area & Wernicke's aphasia - affects all understanding.
• Occipital lobe - primary visual cortex and visual association area.
- Visual agnosia is the loss of the ability to recognize objects and people.
- Neglect syndrome is the failure to see parts of objects on the side opposite the brain
damage.
Major parts of the brain (other than the cortex):
Forebrain - The paired cerebral hemispheres: the cerebrum.
Midbrain - The brain stem, from which the cranial nerves emerge, consisting of the thalamus & hypothalamus, the midbrain, the pons, & the medulla oblongata.
Hindbrain - The cerebellum a.k.a. "little brain”, plays an important role in the integration of sensory perception & motor output.
Pons - a band of nerve fibers linking the medulla oblongata & the cerebellum with the midbrain. Makes chemicals involved in sleep.
Medulla - located at the top of the spinal cord, includes a group of cells that control respiration, heart rate, and blood pressure.
Cerebellum - a large structure consisting of two halves (hemispheres) located in the lower part of the brain; responsible for the coordination of movement & balance.
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