The Nervous System

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The Nervous System

• Medical Term Neuro

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Overview

• The entire nervous system relies on the
  transmission of electrical impulses
• These impulses are done by neurons, the operating
  cells of the brain and spinal cord
• Nervous impulses travel from neuron to neuron as
  they send information from one area of the body
  to another.
• The speed is almost instantaneous! (268
  miles/hour)

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Different parts of the Nervous System

• Central Nervous System (CNS)
• Network of nerve tissue (neurons) found in the
  brain and spinal cord
• Peripheral Nervous System (PNS)
• All nerve tissue (neurons) outside the brain and
  spinal cord. They include
• 12 Cranial (head) nerves that enervate the
  head/senses
• 31 pairs of spinal nerves that enervate the arms,
  trunk, and legs

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Motor vs Sensory

• Fundamental understanding of nervous system
• Sensory Nerves (you sense)
• These nerves receive sensory info from the body
• Also known as Afferent Nerves
• e.g. smell, taste, touch, sight
• Breeze against your face
• That impulse is sent from the nerves in your body
  to your brain via the spinal cord
• Motor Nerves (you move)
• The brain sends out impulses to muscles
• Also known as Efferent Nerves
• You move your arm
• You blink
• e.g. Burning your hand on the stove.
• Most nerves are both sensory and motor

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Neurons

• Neurons
• Cells responsible for electrical transmission
• The brain, spinal cord, and nerves are all
  comprised of neurons
• 100 billion neurons just in brain

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3 Major Parts of the Neuron

• 1. Cell Body
• Contains nucleus and organelles.
• 2. Dendrites
• Short, stubby branches that carry impulses to the
  cell body from another neuron
• They are the receiving part of neuron
• 3. Axons
• Long extension that carries impulses from the
  cell body
• They transmit impulses to dendrites of the next
  neuron.
• They are the giver part of a neuron.
• Axons are surrounding by fat which helps
  accelerate the electrical impulse.

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Neurons (cont)

• Synapse
• Open area where the axon of one neuron
  communicates with the dendrite of the next one.
• Neurotransmitter
• The Chemical released there to send the message
  across
• Famous neurotransmitters
• Epinephrine (Adrenaline)
• Dopamine
• Serotonin
• Acetylcholine

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Glial Cells

• Glial cells are the bodyguards of neurons
• They are not responsible for electrical impulse
• Their job is to
• Surround the neurons to anchor them in place
• Produce the fat (myelin) of the axon to speed
  transmission
• Destroys pathogens
• Supplies nutrients to neurons.

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Activity

• Get into your groups
• Write down 10 examples of sensory impulses
• Write down 10 examples of motor impulses

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The Brain
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The Brain

• Responsible for every physical and mental
  activity of the body
• Memory, emotion, thought, judgment, reasoning,
  consciousness, etc.
• It is made of white and grey matter
• Comprised of mostly fat
• Protected by the cranium
• Weighs 3 pounds
• The four major structures of the brain
• 1. Cerebrum
• 2. Cerebellum
• 3. Diencephalon
• 4. Brain Stem

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1. Cerebrum

• Largest and uppermost part of brain
• It has 2 hemispheres (left and right)
• Corpus Callosum- joins hemispheres together and
  quickens communication b/t the two sides.
• Left side of cerebrum focus on logic and reason
• Right side focus on creativity
• Gyri (sing. gyrus) are the folds or mountains on
  the cerebrum
• Sulci (sing. sulcus) are the dips or cracks on
  the cerebrum.

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Arrangement of Neurons

• Most neurons in the brain are arranged in either
  two layouts.
• 1) Long layers of neurons
• Cerebral Cortex is the outermost layer of the
  cerebrum made of Grey Matter
• Consists of layers of neurons about 4 mm thick
• Responsible for thought, awareness, consciousness
  and learning
• 2) Cluster of neurons (aka brain nuclei)
• Seen mostly in deeper parts of the brain
  (hypothalamus, thalamus)

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Grey vs White Matter

• The brain is comprised of Grey Matter and White
  Matte
• Grey Matter is made largely from layers of the
  bodies of neurons.
• White matter is mostly comprised of glia and the
  long axons of neurons connecting one part of the
  brain to another.

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1. The Cerebrum

• Each hemisphere of the cerebrum is divided into 5
  lobes
• Frontal
• Parietal
• Temporal
• Occipital
• These 4 named after the bone that is directly
  above them
• Insula (Limbic)
• The inner side of hemisphere that faces the other
  hemisphere.
• Includes Hippocampus

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Temporal Lobe of Cerebrum

• Responsible for hearing
• Features the hippocampus
• Main area for memory

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Frontal Lobe of Cerebrum

• Responsible for emotions

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Occipital Lobe of Cerebrum

• Responsible for vision processing

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Parietal Lobe of Cerebrum
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Limbic Lobe of Cerebrum

• Includes the Hippocampus
• Responsible for memory and spatial navigation
• Alzheimers and other forms of dementia affect
  the Limbic.

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2. Diencephalon (Interbrain)

• 2 main parts
• Thalamus The Relayer
• Receives all sensory info from the body and sends
  it to the appropriate part of the brain for
  processing
• Also, it receives impulses from the cerebrum and
  relays them to various parts of body via efferent
  motor nerves
• The Hypothalamus
• Regulates the Autonomic Nervous System (ANS)
• Heartbeat, body temperature, smooth muscle
  control, fluid balance.
• Things you cant control

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3. Cerebellum Baby Brain

• 2nd largest part of the brain
• Sits in the posterior portion of the skull, next
  to occipital bone.
• Maintains balance and equilibrium
• Coordinates muscular movement

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4. Brain Stem

• Comprised of
• 1. Midbrain
• 2. Pons
• 3. Medulla
• Brain stem is a pathway for impulse conduction
  between the brain and spinal cord

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Are you left or right brained?

• Based on this picture, extrapolate 5
  characteristics of people who are predominately
• Right-brain
• Left-brain

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Meninges (sing. Meninx)

• 3 layers of matter that surround the brain
• 1. Dura mater
• Hard, fibrous material
• 2. Arachnoid Space
• Web-like middle space bathed in cerebro-spinal
  fluid (CSF)
• 3. Pia mater
• Thin layer actually on the brain
• Meningitis-infection of the brain layers.

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Cerebro-spinal Fluid (CSF)

• Syrupy fluid that bathes and protects the brain
  and spinal cord.
• Ventricles
• Chambers full of CSF fluid that are inside the
  brain
• Lateral
• 3rd Ventricle
• 4th Ventricle

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Spinal Cord

• Transmits sensory impulses from the body to the
  brain, and
• Transmits motor impulses from the brain to the
  body
• Located in the spinal cavity of the vertebrae
  with spinal nerves exiting between each vertebrae
  to enervate the arms, trunks, and legs.
• Spinal cord runs from the brain and to Lumber 3.
• Cauda Equina- strands of nerves that run down the
  rest of the spinal cavity.

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Plexus

• Big branches of nerves that come off of spinal
  cord
• Brachial
• Comes of the spine near lower c-spine
• Enervates the upper extremity
• Lumbar
• Comes off L-spine
• Enervates hips, groin, abdominal area
• Sacral
• Comes off sacrum
• Enervates the lower extremity

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Cranial Nerves

• Most important nerves in the body. There are 12
• All originate off the brain stem
• Listed in Roman numerals
• I-(Olfactory)-Smell
• II-(Optic)-Eyesight
• III (Oculomotor), IV (Trochlear), and VI
  (Abducents)-Eye Movement
• V (Trigeminal)-Facial Sensation
• VII (Facial)-Facial motor
• VIII (Vestibulocochlear)-Ear
• IX (Glossopharyngeal) and XII (Hypoglossal)-
  Tongue and Swallowing
• X (Vagus) -Controls diaphragm, all organs in body
• XI- (Spinal)

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Pathology

• Meningitis-Inflammation of the meninges
• Concussion-Bruising of brain tissue
• Hydrocephalus- Swelling of the brain due to
  increase amount of CSF fluid
• Encephalitis-Infection of the brain, typically
  due to bacteria or virus

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Hydrocephalus Water in the brain

• Excess CSF fluid in the brain
• The choroid plexus of the ventricles, the cells
  responsible for producing CSF, either produce too
  much, or the venous system doesnt absorb it fast
  enough
• It compresses (squeezes) the brain tissue which
  increases intracranial pressure.
• Etiology
• Mal-development in utero
• May develop during adulthood by a tumor,
  infection, etc
• Signs
• Disease occurs in infants
• Head swells as brain pushes unsutured cranial
  bones apart
• Scalp veins dilate
• Decreased mental abilities

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Hydrocephalus

• Diagnosis
• Lumbar tap
• CT/MRI
• Treatment
• Shunt
• A shunt is a tube inserted in the ventricles to
  move the excess fluid to the right atrium or
  abdomen.

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Seizures

• Uncontrolled, excessive discharge of neurons
• Multiple causes and types
• May be caused by external stimuli, drugs,
  secondary disease.
• Generalized seizure- loss of consciousness due
  to multiple parts of the brain seizing
• Partial- no loss of consciousness, normally only
  one part of brain seizes.
• Petit mal seizure (Generalized)
• Occurs in children
• Lasts a few seconds, twitches and lip smacking
  ensue
• Child returns to normal c no memory of it
• Grand mal seizure (Generalized)
• Begins with twitching, nausea, depression
• Aura-visual or auditory hallucination
• Loss of consciousness follows
• The tonic-clonic stage ensues of strong muscle
  contraction/relaxation as the body contorts
  itself into strange position. Foaming of the
  mouth, screaming, and incontinence may ensue.
• Contractions dissipate, patients wakes up achy
  and then falls into a deep sleep.

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Seizures

• Treatment
• Anti-convulsive and sedative drugs are given to
  lessen chance of seizure or to minimize outbursts.

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Huntingtons Disease

• Genetic disorder, 13 from House has it.
• Progressive atrophy (or deterioration) of neurons
• Ventricles swell
• Symptoms Wild mood swings, wild jerky movements
  of extremities, gradual loss of cognitive and
  motor skills
• Prognosis Death!

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Schizophrenia

• Chronic mental condition which features the
  following symptoms
• Visual and auditory hallucinations
• Delusions of personal grandeur
• The belief that people are plotting against you.
  
• Detachment, increased drug use, and suicidal
  ideation.

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Dissociative Identity Disorder

• Formerly Multiple Personality Disorder.
• Person has at least 2 distinct personalities
  (alter egos)
• One personality controls the other
• Main personality has time of amnesia.
• Cause Trauma (physical/sexual)
• Controversy
• CIA
• Implanted personalities.

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Herniated Disc

• The intervertebral disc is comprised of two
  components
• Nucleus pulposus- inner gelatinous filling
• Annulus fibrosis- tough outer layer
• Poor body mechanics, trauma, or degenerative
  condition cause the nucleus to leak out.
• It impinges or touches either the spinal cord or
  the nerve roots that go down the arm or leg
• Causes loss of motor or sensory sensation and
  intermittent pain in leg or arm (depending on
  which plexus it is impinging).
• Minor day surgery may fix it easily

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Assignment

• Identify the following terms
• Neuron
• Dendrite
• Axon
• Synaptic Gap
• Cerebellum
• Corpus Callosum