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Hind/Mid and Forebrain Functions
Transcript of Hind/Mid and Forebrain Functions
Functions and Overview
of the Human Brain
The hindbrain extends from the spinal cord and contains the Medulla Oblongata and the Pons.
The cerebellum is the largest part of the hindbrain, and second-largest part of the brain as a whole.
The hindbrain is responsible for controlling a number of important body functions and process, including respiration and heart rate. The brain stem is an important part of the hindbrain, and it controls functions that are critical to life, such as breathing and swallowing.
is a short segment of brainstem that connects the hindbrain and forebrain.
The part of the midbrain posterior to the cerebral aquaduct is a rooflike tectum. It exhibits four bulges, the corpora quadrigemina. The upper pair, called the superior colliculi, functions in visual attention, visually tracking moving objects, and such reflexes as blinking, focusing, pupillary dilation and constriction. The lower pair, called the inferior colliculi, recieves signals from the inner ear and relays them to other parts of the brain, especially the thalamus. Among other functions, they mediate the reflexive turning of the head in response to a sound, and one's tendency to jump when startled by a sudden noise.
The forebrain consists of the diencephalon and telencephalon. The diencephalon encloses the third ventricle and is the most rostral part of the brainstem. The telencephalon develops chiefly into the cerebrum.
The diencephalon contains 3 structures which are: the thalamus, the hypothalamus and epithalamus. They are responsible for such functions as motor control, relaying sensory information, and controlling autonomic functions.
The telencephalon becomes the cerebrum, the largest and most conspicuous part of the brain. Structures in the cerebrum include: the cerebral cortex, the basal nuclei and the limbic system. The left and right regions of the cerebral cortex are separated by a thick band of tissue called the corpus callosum Each hemisphere is split into four lobes; the frontal, parietal, occipital and temporal lobes.
Functions and Overview
of the Human Brain
Gray and White Matter
The brain, like the spinal cord, is composed of gray and white matter.
Gray matter- the seat of neurosomas, dendrites, and synapse- form a surface layer called the cortex over the cerebrum and cerebellum, and deeper masses called nuclei are surrounded by white matter.
White matter lies deep to the cortical gray matter in most of the brain, opposite from the relationship of gray and white matter in the spinal cord.
The organs of the central nervous system (brain and spinal cord) are covered by 3 connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.
The medulla beings at the foramen magnum of the skull and extends about 3 cm rostrally, ending at the groove between the medulla and pons. It looks superficially like an extension of the spinal cord
Its external appearance is characterized by an anterior pair of ridges called pyramids, lateral to each pyramid is a prominent bulge called the olive, with gracile and cuneate fasciculi tubercles dorsally and the attached nerves.
The medulla relays sensory information to the thalamus and contains major regulatory centers in its reticular formation, as well as containing cardiac and respiratory control centers which determine heart and breathing rates.
The pons measures about 2.5 cm long. It sits directly above the medulla. The main function of this structure is to pass information between the cerebellum and cerebrum. In addition, it helps to send other messages to the brain, manage arousal feelings, and monitor respiration.
The anterior half of the pons is dominated by tracts of white matter, including transverse fascicles that cross between left and right and connect the two hemispheres of the cerebellum, and longitudinal fascicles that carry sensory and motor signals up and down the brainstem
The Reticular Formation
The reticular formation is a loosely organized web of gray matter that runs vertically through all levels of the brainstem. It occupies much of the space between the white fiber tracts and the more anatomically distinct brainstem nuclei, and has connections with many areas of the cerebrum. It consists of more than 100 small neural networks defined less by anatomical boundaries than by each network's use of a different neurotransmitter. The functions of these networks include:
Somatic motor control
Sleep and consciousness
The Medulla Oblongata
The cerebellum is the largest part of the hindbrain and the second-largest part of the brain as a whole. It controls motor movement coordination, balance, equilibrium and muscle tone. It is located at the back of the brain, underlying the occipital and temporal lobes of the cerebral cortex.
It consists of right and left cerebellar hemispheres connected by a narrow wormlike bridge called the vermis.
The cerebellum is connected to the brainstem by three pairs of stalks called cerebellar peduncles: a pair of inferior peduncles connected to the medulla oblongata, a pair of middle peduncles to the pons, and a pair of superior peduncles to the midbrain. These consist of thick bundles of nerve fibers that carry signals to and from the cerebellum.
Each side of the brain has a thalamus, an ovoid mass perched at the superior end of the brainstem beneath the cerebral hemisphere. The thalamus is the gateway to the cerebral cortex. Nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, including signals for taste, smell, hearing, equilibrium, vision, touch, pain, temperature. The thalamus also plays a key role in motor control by relating signals from the cerebellum to the cerebrum and providing feedback loops between the cerebral cortex and basal nuclei. The thalamus is involved in memory and emotional functions of the limbic system.
The hypothalamus forms the floor and part of the walls of the third ventricle. It extends anteriorly to the optic chaism, where the optic nerves meet, and posteriorly to a pair of humps called the mammillary bodies. The pituitary gland is attached to the hypothalamus by a stalk between the otic chiasm and mammillary bodies. The hypothalamas is the major control center of the endocrine and autonomic nervous system. It plays essential role in the homeostatic regulation of nearly all organs of the body. Its nuclei include centers concerned with a wide variety of visceral functions:
Food and water intake
Sleep and circadian rhythms
Emotion behaviour and sexual response
The epithalamus is a very small mass of tissue composed of mainly the pineal gland.