Central Nervous System

Divisions of the Brain

 Brainstem  Medulla oblongata  extension of spinal cord   Contains the cardiac, respiratory and vasomotor centers (control heartbeat, blood vessel diameter) Consists of white and gray matter intermingled   Pons Midbrain

Diencephalon

   Small, located above midbrain, below cerebrum Consists of 2 major structures: hypothalmus and thalmus Hypothamus:  Pituitary gland is an extension of hypothalmus  Major control over most major organs    Make hormones secreted by pituitary gland Secrete releasing hormones into blood to the anterior pituitary gland Helps regulate water balance, body temperature, sleep cycles and appetite and many emotions

Diencephalon

 Thalmus    Dumb bell shaped gray matter, above hypothalmus Axons go into cerebellum Helps produce sensations, associates sensations with emotions and plays a role in the arousal or alerting mechanism

Cerebellum

   Second largest part of human brain Arbor vitae – tree of life, gray matter on outside, white matter inside Produce smooth, coordinated movements, maintain equilibrium and sustain normal postures.

cerebrum

    Largest and upper most part of brain Ridges – convolutions or gyri Grooves – sulci, deep grooves – fissures   Longitudinal fissure – divides into left and right Find also the central sulcus, lateral fissure Corpus callosum – connects left and right hemisphere of the brain

cerebrum

  4 major lobes of the brain named for bones  Frontal, Occipital, Temporal, parietal Cerebral cortex – gray matter, surface of cerebrum  White matter (tracts) makes up most of cerebrum  exception is basal ganglia (produce automatic movements and posture, ex. Parkinson disease

Brain disorders

  Cerebrovascular accident (CVA) – stroke – hemorrhage or cessation of blood flow through vessels in brain, neurons die  If damage occurs in a motor control section of brain, movement ceases Cerebral palsy – damage to brain tissue  Prenatal infections, trauma to the head before, during, after birth, reduced oxygen to brain  Spastic paralysis – involuntary contractions of affected muscles     Hemiplegia – 1 side of body Paraplegia – both legs Triplegia – both legs, 1 arm Quadriplegia – all 4 appendages

Degenerative brain disorders

    Destruction of neurons in the brain Affects memory, attention span, intellectual capacity, personality and motor control = dementia Alzheimer Disease (AD) – lesions on cerebral cortex Huntington disease (HD) – chorea – involutary purposeless movements

Seizure

   Seizure – sudden bursts of abnormal neuron activity  Range from mild to severe Epilepsy – recurring or chronic seizures  Can be caused by tumors, trauma, or chemical imbalances, most idiopathic Medications block neurotransmitters in affected areas of the brain.

Spinal cord

    Average of 17 – 18 inches From occipital bone to L1 vertebrae core is made up of gray matter Outer part is white matter – spinal tracts

Spinal cord

   2 way conduction   Ascending tracts – to brain Descending tracts – from the brain Primary reflex center Cut in the spinal cord results in no communication   Anesthesia – loss of sensation Paralysis – loss of the ability to make voluntary movements

Coverings

   Meninges – touch, fluid-containing membrane 3 layers    Dura mater – tough outer layer Pia mater – innermost membrane, covers spinal cord Arachnoid mater – between dura and pia mater, cob web like Meningitis – infection or inflammation of meninges

Fluids

   Cerebrospinal fluid (CSF) – fills subarachnoid spaces in brain and spinal cord and ventricles in brain  2 lateral ventricles and third ventricle CSF is continuously begin made from fluid filtering out of choroid plexus and into ventricles and continues to circulate around the brain and spinal cord Hydrocephalus – water on the brain – accumulation of CSF in ventricles