Anatomy and Physiology of the Brain Essay Sample
* Neurologic system consists of two main divisions, the central nervous system (CNS) and the peripheral nervous system (PNS). The autonomic nervous system (ANS) is composed of both central & peripheral elements.
CENTRAL NERVOUS SYSTEM
* Is composed of the brain and the spinal cord and associated nerves.
* Structurally the brain consists of the cerebrum, cerebellum, brain stem & limb. *
* Largest part of the brain
* Is the center for consciousness, thought, memory, sensory input, and motor activity;
* It consists of two hemispheres (left & right) and four lobes each with specific functions.
* 2 hemispheres
* The left hemisphere controls the right side of the body and is the center for logical and analytical functions such as reading, writing, and mathematical tasks. * The right hemisphere controls the left side of the body and is the center for creative intuition, and artistic ability. * Sulcus – separates the cerebrum into the right and left hemisphere. * Corpus callosum – is a thick collection of nerve fibers that connects two hemispheres of the brain and is responsible for the transmission of information from one side of the brain to the other. * 4 lobes
* Frontal lobe
* Largest lobe, located in front of the skull. * Major functions of this lobe are concentration, abstract thought, information storage or memory and motor functions. * Controls voluntary muscle movements and contains motor areas, including the area for speech. * It also contains the centers for personality, behavioral, autonomic & intellectual functions and those for emotional and cardiac responses.
* Temporal lobe
* Contains the auditory receptive areas located around the temples.. * Contains a vital area called the interpretative area that provides integration of somatization, visual and auditory areas and plays the most dominant role of any area of the cortex in thinking * Parietal lobe
* Coordinates and interprets sensory information from the opposite side of the body. * A predominantly sensory lobe located near the crown of the head. * This lobe analyzes information and relays the interpretation of this information to the thalamus and other cortical areas. * Essential to a person’s awareness of the body in space, as well as orientation in space and spatial relations. * Occipital lobe
* Posterior lobe of the cerebral hemisphere located at the lower back of the head. * Assist in coordinating language generation and visual interpretation and depth perception. * CEREBELLUM
* Sits between the cerebrum and the brainstem.
* Receives and integrates information from all areas of the body, such as muscle and other components of the CNS. * Controls smooth muscle movements, coordinates sensory impulses with muscle activity, and maintains muscle tone and equilibrium. * BRAIN STEM
* Sits at the bottom of the brain.
* Connects the brain to the spinal cord.
* Which includes the mesence phalon, pons, and medulla oblongata, relays nerve impulses between the brain and spinal cord. * Midbrain
* Connects the pons and cerebellum with the cerebral hemispheres. * It contains sensory and motor pathways and serves as the center for auditory and visual reflexes. * Cranial nerves III and IV originates in the midbrain * Pons
* Situated in front of the cerebellum between the midbrain and
the medulla. * Bridges the gap both structurally and functionally serving as a primary motor part. * Contains motor and sensory pathways.
* Portion of the pons also control the heart, respiration, and blood pressure. * Cranial nerves V and VIII connect to the pons. * Medulla Oblongata
* Contains the motor fibers from the brain to the spinal cord and sensory fibers from the spinal cord to the brain. * Cranial nerves IX through XII connect to the brain in the medulla
* LIMBIC SYSTEM
* An area of the brain located above the brain stem.
* Regulates activity, sensation, and emotions.
* Organizes cerebral functions by transmitting impulses to and from the cerebrum. * Responsible for primitive emotional responses, such as fear, and for distinguishing between pleasant and unpleasant stimuli. * Hypothalamus
* Located anterior and inferior to the thalamus. * Plays an important role in the endocrine system because it regulates the pituitary secretion of hormones that influence metabolism, reproduction, stress response and urine production. * Automatic center that regulates blood pressure, temperature, libido, appetite, breathing, sleeping patterns and peripheral nervous discharges associated with certain behavior and emotional expression. * It also helps control pituitary secretion and stress reaction. * Hippocampus and amygdale
* Involved in emotional arousal and memory.
PERIPHERAL NERVOUS SYSTEM
* Is composed of the 12 pairs of the 31 pairs of spinal nerves. * Connects CNS to remote body regions and conducts signal to and from these
areas and the spinal cord. * System of nerves that connects the outlying parts of the body with the CNS. * SPINAL CORD
* Extends from the medulla oblongata to the lower border of the first lumbar vertebrae. * Contains millions of nerve fibers, and it consist of 31 nerves – 8 cervical, 12 thoracic, 5 lumbar, 5 sacral. * Forms 2 way conductor pathway between the brain stem and the PNS. * It is also the reflex center for motor activities that do not involve brain control. AUTONOMIC NERVOUS SYSTEM
* Regulates body functions such as digestion, respiration, and cardiovascular function supervised chiefly by the hypothalamus. * Comprised of visceral efferent (motor) and the visceral afferent (sensory) nuclei in the brain and spinal cord. * Its peripheral division is made up of visceral efferent and afferent nerve fiber as well as autonomic and sensory ganglia. The ANS contains two divisions:
* Sympathetic nervous system
* Serves as an emergency preparedness system, the “flight-for-fight” response. * Sympathetic impulses increase greatly when the body is under physical or emotional stress causing bronchioles dilation, dilation of the heart and voluntary muscle blood vessels, stronger and faster heart contractions, peripheral blood vessels constriction. * Sympathetic stimuli are mediated by nor epinephrine. * Parasympathetic nervous system
* Dominant controller for most visceral effectors for most of the time. * Parasympathetic impulses are mediated by acetylcholine.
Protection of the brain
* MENINGES – the membranes that cover the brain and spinal cord. * CEREBROSPINAL FLUID (CSF) – the fluid produced by choroid plexi; fills the ventricles and surrounds the CNS. The brain is covered by three membranes:
1) The Dura mater is a fibrous, connective tissue structure containing several blood vessels. The outermost and toughest of the three membranes (meninges) covering the brain and spinal cord.
* Four extensions of the Dura:
* Falx cerebri – separates the two hemispheres in longitudinal plane. * Tentorium – infolding of the dura that forms a tough, membranous shelf. * Falx cerebella – between two lateral lobes of the cerebellum. * Diaphgram sellae – provides a roof for the sella turicica. 2) The Arachnoid membrane is a delicate serous membrane. Specifically, the weblike middle layer of the three meninges. It appears white because it has no blood supply. * Contains the choroid plexus – responsible for the production of cerebrospinal fluid. 3) The Pia mater is a vascular and the innermost membrane. A thin, transparent layer that hugs the brain closely and extends into every fold of the brain’s surface.
* Neuron – is the functional unit of the brain.
* Dendrite – branch-type structure with synapses for receiving electrochemical messages.
* Axon – is a long projection that carries impulses away from the cell body.
* Communicate messages from one neuron to another or from a neuron to a specific target tissue.
* Manufactured and stored in synaptic vesicles.
* Enable conduction of impulses across the synaptic cleft.