Download Nervous System

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
• Neuron
• 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
1. Astrocytes
•
•
Star-like apperance (astr/o = star)
Transports water & salts between capillaries & neurons
2. Microglial cells
•
Protect neurons in response to inflammation
3. Oligodendrocytes
•
•
Few dendrites (olig/o = few or scanty)
Form the myelin sheath in the CNS
4. 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
• 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
• Auto
• Visual Image
• See the AUTOmatic
car driving ITSELF
• Meaning
• self
Blephar• Audionym
• Blue fur
• Visual image
• See the lady wearing
BLUE FUR with
EYELIDS
• Meaning
• eyelid
Cau-, caus
• Audionym
• Cough
• Visual Image
• See the COUGH the
BURNS
• Meaning
• burn
Dacry-, lacrim• Audionym
• Daiquiri
• Visual Image
• See the DAIQUIRI
drink crying a tear
• Meaning
• tear
Dur• Audionym
• Door
• Visual Image
• See the DOOR with
the HARD hat on it.
• Meaning
• Hard, dura mater
Hemi• Audionym
• Hemisphere
• Visual Image
• See the HEMIsphere
in HALF
• Meaning
• Half
Kerat• Audionym
• Carrot
• Visual Image
• See the CARROT
being used as HORNS
• Meaning
• Horny, horny tissue,
cornea
Mening• Audionym
• Manage
• Visual Image
• See the MANAGER
managing MEN’S
BRAINS
• Meaning
• membrane
Ment• Audionym
• Mint
• Visual Image
• See the person picking
up the MINT saying
“MINE, MINE”
• Meaning
• mind
Neuro• Audionym
• Nero
• Visual Image
• See NERO being very
NERVOUS as Rome
burns
• Meaning
• Nerve (nervous
system)
Ophthalm-, ocul• Audionym
• Up thumb
• Visual Image
• See the UP THUMB
(thumbs up) with an
EYE on top
• Meaning
• eye
Phren• Audionym
• Friend
• Visual Image
• See the people pulling on
the FRIEND saying, “MINE!
MINE! MINE!”
• Meaning
• mind
Radic-, radicul• Audionym
• Radish
• Visual Image
• See the RADISH it’s a
ROOT
• Meaning
• Root, nerve root
Semi• Audionym
• Semi colon
• Visual Image
• See the SEMI-colon
cut in HALF
• Meaning
• Half