a&p ch 14
Terms
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- 4 major parts of the brain
- brianstem, dicephalon, cerebrum, cerebellum
- brainstem
- continuous with spinalcord and consists of the medulla oblongata, pons and midbrain
- cerebellum
- little brain posterior to the brain stem
- dicephalon
- superior to the brain stem, consists mainly of the thalamus hypothalamus epithalamus and subthalamus
- cerebrum
- superior and enveloping the dicephalons the largest part of the brain
- blood brain barrier
- protects brain cells from harmful substances and pathogens
- crainial meninges
- surround and protect the brain crainial meninges are continous with spinal meninges
- dura mater
- outer
- arachnoid mater
- middle
- pia mater
- inner
- falx cerebri
- seperates two hemispheres of cerebrum
- falx cerebelli
- seperates two hemispheres of cerebellum
- tentorium cerebelli
- seperates the cerebrum from the cerebellum
- cerebrospinal fluid (csf)
- a clear colorless liquid protects the brain and spinal cord against chemical and physical injuries and carries oxygen, glucose and other needed chemicals from blood to neurons and neuroglia
- ventricles
- four csf filled cavities within brain
- lateral ventricles
- located in each hemisphere of the cerebrum
- septum pellucidum
- a thin membrane seperating the lateral ventricles
- third ventricle
- narrow cavity along midline superior to hypothalamus, between right and left halves of the thalamus
- fourth ventricle
- lies between the brain stem and cerebellum
- mechanical protection (csF)
- shock absorbing medium, also buoys the brain so it "floats" in cavity
- chemical protection (CSF)
- provides optimal chemical enviroment for accurate neuron signaling. slight changes in ionic composition disrupt production of aps and postsynaptic potentials
- circulation
- medium for exchange of nutrients and waste between blood and nervous tissue
- choroid plexuses
- site of csf production networks of capillaries in the walls of ventricles covered by ependymal cells that form csf from blood plasma by filtration and secretion
- blood cerebrospinal fluid barrier
- ependymal cells are joined by tight junctions forming semi permeable sheet which regulates the passage of materials from the choroid plexuses to the csf protecting the brain and spinal cord from potentially harmful blood-borne substances
- circulation csf
- formed in laters ventricles-thru interventricular foramina to-third ventricle-thru the cerebral aqueduct to-fourth ventricle-thru three openings-to the subarachnoid space and central canal-csf is reabsorbed into blood through arachnoid villi
- brain stem
- consist of the medulla oblongata, pons ans midbrain
- reticular formation
- a netlike region of interspresed gray and white matter that extends thru the brain stem
- medulla oblongata
- a contionuation of the spinal cord, contains all sensory and motor tracts extending between the spinal cord and other parts of the brain
- pyramids
- white matter bulges on the anterior aspect of medulla, formed by the largest motor tracts that pass from the cerebrum to spinal cord
- decussation of pryamids
- 90% of axons cross over to the opposite side just before entering the spinal cord. explains why one side of the brain controls the otherside of the body
- medulla oblingata controls vital body functions:
-
cardiovascular center- regulates heart rate force of heartbeat and diameter of blood vessels
medullary rhymicity- of respiratory center adjusts basic rhythem of breathing.
medulla also contains other nuclei which contro reflexes for vomiting coughing sneezing - olive
- an oval shaped swelling lateral to each pyramid which houses the inferior olivary nuclues
- inferior olivary nucleus
- impulses from propriceptors are re;ayed to cerebellum
- gracile and cuneate nucei
- associated with sensation of touch, conscious proprioception, pressure, and vibration, located in the posterior section of the medulla
- medial lemniscus
- band of white matter where medullary axons ascend to the thalamus carring sensory information
- pons
- lies directly superior to medulla and anterior to cerebellum and consists of both nuclei and tracts
- pontine nucluei
- site where voluntary movements from cerebral cortea are relayed into crebellum
- pneumotaxic and apneustic areas
- together with medullary rythmicity are help to control breathing
- midbrain
- midbrain or mesencephalon extends from pons to dicephalon and contains both tracts and nuclei
- cerebral peduncle
- anterior pair of tracts that contain axons of motor neurons conducting nerve impulses from cerebrum to medulla pons and spinalcord
- tectum
- posterior part of midbrain contains 4 rounded elevations
- superior colliculli
- 2 superior elevations serve as reflex center for certain visual activities such as eye movement and tracking and the pupillary reflex
- inferior colliculi
- two inferior elevations part of auditory pathway relaying impulses from hearing receptors to thalamus
- substantia
- large darkly pigmented nuclei together with basal ganglia control subconscious muscle activities loss of these neurons is associated with parkinsons disease
- red nuclei
- on l and r side function with cerebellum to coordinate muscular movements