Nervous System
General Structure Central Nervous System (CNS) Brain & spinal cord Peripheral Nervous System (PNS) Cranial nerves Carry impulses between the brain & the head & neck Exception: Vagus Nerve Spinal nerves Plexuses Plexus = large network of nerves Peripheral nerves
Peripheral Nervous System Spinal & Cranial nerves are composed of: Sense receptors For sight, hearing, balance, smell, touch & Sensory (afferent) nerves Carry messages toward the spinal cord & brain Motor (efferent) nerves Travel from the spinal cord & brain to muscles, telling them how to respond
Peripheral Nervous System Autonomic nervous system Function involuntarily or automatically Carries impulses away from the CNS to the glands, heart, blood vessels, & involuntary muscles (intestines, stomach, bladder) Autonomic nerves Sympathetic nerves Stimulate the body in times of stress & crisis Increase heart rate, dilate airways, increase BP, stimulate the adrenal glands, inhibit intestinal contractions Parasympathetic nerves Slow down heart rate, lower BP & stimulate intestinal contractions
Neurons, Nerves, & Glial Cells Individual nerve cell Ganglia Small collections of nerve cell bodies outside the brain & spinal cord
Synapse Space where the nervous impulse jumps from one neuron to the other. Neurotransmitter Chemical substance that transfers the impulse Acetylcholine, norepinephrine, epinephrine, dopamine, serotonin, endorphins
Nerve Nerve Consists of a bundle of dendrites and axons that travel together like strands of rope Peripheral nerves Carry impulses to the brain (afferent or sensory nerves) Carry impulses from the CNS to organs (efferent or motor nerves)
Glial Cells (Neuroglial Cells) Supportive, protective, and connective tissue of the CNS Glial cells are stromal (framework) tissue, whereas neurons carry nervous impulses Astrocytes Star-like apperance (astr/o = star) Transports water & salts between capillaries & neurons Microglial cells Protect neurons in response to inflammation Oligodendrocytes Few dendrites (olig/o = few or scanty) Form the myelin sheath in the CNS Ependymal cells Line membranes where cerbrospinal fluid (CSF) circulates
The Brain Cerebrum Largest part of the brain. Cerebral cortex Nerve cells lie in sheets on the surface of the cerebrum Gyri – folds in the sheets Sulci – grooves that separate the gyri Cerebral Hemispheres Divides the brain in right & left sides. Each divided into lobes Frontal Thought processes, behavior, personality, emotion Parietal Body sensations, visual & spatial perception Occipital vision Temporal Hearing, understanding, speech, language
The Brain Thalamus Acts like a triage center. Decides what is important & what is not. Hypothalamus Contain neurons that control temperature, sleep, appetite, emotions (fear & pleasure). Regulates hormones from the pituitary gland
The Brainstem Lie in the back & below the cerebrum & connect the brain to the spinal cord Cerebellum Functions to coordinate voluntary movements & maintain balance & posture Pons Literally means bridge. Connects the cerebellum & cerebrum with the rest of the brain Medulla oblongata Connects the spinal cord with the rest of the brain Regulates: Respiratory center: controls muscles of respiration Cardiac center: slows the heart rate if beats are too rapid Vasomotor center: constricts or dilates the blood vessels, influencing blood pressure
The Spinal Cord & Meninges Column of nervous tissue from the medulla oblongata to L-2. Cauda Equina (Latin for “horse’s tail) is a fan of nerve fibers below the end of the spinal cord.
Spinal Cord Cross-Sectional View Gray matter Containing cell bodies & dendrites White matter Containing the nerve fiber tracts with myelin sheaths
Meninges Three layers of connective tissue that surround the brain & spinal cord dura mater epidural subdural arachnoid subarachnoid space contains CSF pia mater blood vessels and lymph
Pathology Maybe classified in the following categories Congenital Neoplastic (tumors) Degenerative, movement, & seizure Traumatic Infectious (meningitis & encephalitis) Vascular (stroke)
Congenital Disorders Hydrocephalus Spina bifida Spina bifida occulta Abnormal accumulation of fluid (CSF) in the brain Spina bifida Congenital defects in the lumbar spinal column caused by imperfect union of vertebral parts (neural tube defect) Spina bifida occulta Vertebral defect is covered over & only evident on x-ray Meningocele Meniges protrudes to the outside Myelomeningocele Both spinal cord & meninges protrude
Degenerative, Movement, & Seizure Disorders Alzheimer disease (AD) Brain disorder marked by gradual & progressive mental deterioration, personality changes, & impairment of daily living Epilepsy Chronic brain disorder characterized by recurrent seizure activity Huntington disease Hereditary disorder marked by degenerative changes in the cerebrum leading to abrupt involuntary movements & mental deterioration. Multiple Sclerosis (MS) Destruction of the myelin sheath on neurons in the CNS & its replacement by plaques of sclerotic (hard) tissue
Infectious Disorders Herpes Zoster (shingles) Viral infection affecting peripheral nerves Meningitis Inflammation of the meninges; leptomeningitis Human Immunodeficiency Virus Encephalopathy Brain disease & dementia occurring with AIDS
Neoplastic Disorders Brain Tumor Abnormal growth of brain tissue & meninges Most arise from glial cells or the meninges
Traumatic Disorders Cerebral concussion Temporary brain dysfunction (brief loss of consciousness) after injury, usually clearing within 24 hours Cerebral contusion Bruising of brain tissue as a result of direct trauma to the head; neurologic deficits persist longer than 24 hours
Vascular Disorders Cerebrovascular accident (CVA) Disruption in the normal blood supply to the brain; stroke Thrombotic – blood clot (thrombus) in the arteries leading to the brain Embolic – an embolus (dislodged thrombus) travels to cerebral arteries & occludes a small vessel Hemorrhagic - blood vessel breaks
Audionyms
Auto- Audionym Visual Image Meaning Auto See the AUTOmatic car driving ITSELF Meaning self
Blephar- Audionym Visual image Meaning Blue fur See the lady wearing BLUE FUR with EYELIDS Meaning eyelid
Cau-, caus Audionym Visual Image Meaning Cough See the COUGH the BURNS
Dacry-, lacrim- Audionym Visual Image Meaning Daiquiri See the DAIQUIRI drink crying a tear Meaning tear
Dur- Audionym Visual Image Meaning Door See the DOOR with the HARD hat on it. Meaning Hard, dura mater
Hemi- Audionym Visual Image Meaning Hemisphere See the HEMIsphere in HALF Meaning Half
Kerat- Audionym Visual Image Meaning Carrot See the CARROT being used as HORNS Meaning Horny, horny tissue, cornea
Mening- Audionym Visual Image Meaning Manage See the MANAGER managing MEN’S BRAINS Meaning membrane
Ment- Audionym Visual Image Meaning Mint See the person picking up the MINT saying “MINE, MINE” Meaning mind
Neuro- Audionym Visual Image Meaning Nero See NERO being very NERVOUS as Rome burns Meaning Nerve (nervous system)
Ophthalm-, ocul- Audionym Visual Image Meaning Up thumb See the UP THUMB (thumbs up) with an EYE on top Meaning eye
Phren- Audionym Visual Image Meaning Friend See the people pulling on the FRIEND saying, “MINE! MINE! MINE!” Meaning mind
Radic-, radicul- Audionym Visual Image Meaning Radish See the RADISH it’s a ROOT Meaning Root, nerve root
Semi- Audionym Visual Image Meaning Semi colon See the SEMI-colon cut in HALF Meaning Half