The Nervous System

Nervous System

• Complex, highly organized system which coordinates all the activities of the body.

Neuron

• Neuron= nerve cell• Basic structural unit of

the nervous system

• Myelin sheath –lipid (fat) covering of axon – increases rates of impulse transmission and insulates and maintains the axon

• Khan Academy: Neuron

Application: Nerve Cell Diagram

Synapses

• The axon of one neuron lies close to the dendrites of many other neurons

• Space in between them is called a synapses• Impulses coming from one axon jump the

synapse to get to the dendrite of another neuron

Neurotransmitters

• Chemicals located in axon • Allow nerve impulses to pass from one neuron

to another

2 Main Divisions of Nervous System

• Central Nervous System – brain and spinal cord

• Peripheral Nervous System – nerves:• 12 pairs of cranial nerves extending out from brain• 31 pairs of spinal nerves extending out from spinal cord

Central Nervous System

Application

• Using text, draw and label a diagram of the brain. Use colored pencils to identify each structure of the brain.

CNS – Central Nervous System

• Brain and spinal cord• Brain weights about 3lbs• Contains about 100 billion neurons• Main sections include:• Cerebrum- largest section of brain – thought,

reasoning, memory, speech, sensation, sight, smell, hearing, voluntary body movement.

Cerebrum

• 2 hemispheres: left and right• Cells in Lt hemisphere control movements on right

side of body and cells in Rt hemisphere control movements that occur on left side of body

• 4 lobes: frontal, parietal, temporal, occipital• Fissures – deep grooves• Longitudinal fissure – b/w left and right hemispheres• Sulci- shallow groves• Gyri – elevated ridges

Broca’s – speech Wernicke’s – speech comprehension

Application:

• Patient has a stroke on the left side of the body. Which side of the body would weakness or paralysis occur?

Application

• Using Body Structures and Functions text:– Identify the 5 major fissures and their location in

the brain

Fissures: Longitudinal, Transverse, Central, Lateral, Parieto-occipital

Cerebrum: Frontal Lobe

• Speech• Emotions• Personality• Morality• Intellect

Cerebrum: Parietal Lobe

• Pain• Touch• Heat• Cold• Balance(sensory and motor)

Cerebrum: Occipital Lobe

• vision

Cerebrum: Temporal Lobe

• Hearing • Smell• Left hemisphere –

Wernicke’s area (speech understanding and comprehension)

Cerebellum

• Muscle coordination• Balance• Posture• Walking • dancing

CNS – brain (cont’d)

• Diencephalon – area between cerebrum and midbrain- contains thalamus and hypothalamus– Thalamus – acts as a relay center and directs sensory

impulses to cerebrum. Damage may cause increased sensitivity to pain or loss of consciousness.

– Hypothalamus – regulates autonomic nervous system, temp, appetite, water balance, sleep , blood vessel constriction and dilation, emotions (anger, fear, pleasure, pain, affection)

CNS –brain (cont’d)

• Midbrain- section below the cerebrum at top of brain stem. Responsible for conducting impulses between brain parts and certain eye and auditory reflexes.

CNS – brain (cont’d)

• Pons – located in brain stem• Conducting messages to other parts of the

brain• Reflexes such chewing, tasting, saliva

production, assisting with respiration• Medulla Oblongata – lowest part of brain stem

which connects to spinal cord – Regulates heartbeat, respiration, swallowing,

coughing, blood pressure

Meninges

• 3 membranes which cover and protect the brain and spinal cord– Dura mater – thick, tough, outer layer– Arachnoid membrane – delicate and weblike

middle layer– Pia mater - closely attached to brain and spinal

cord. Contains blood vessels that nourish the nerve tissue

Ventricles

• Brain has 4 ventricles which are hollow spaces filled with cerebrospinal fluid.– CSF serves as a shock absorber to protect brain

and spinal cord.– Transports nutrients to CNS– Removes metabolic wastes

• Spinal cord continues down from medulla oblongata and ends at 1st or 2nd lumbar vertebrae.

• Surrounded and protected by vertebrae• Responsible for reflex actions– Afferent (sensory) nerves carry messages from all

parts of the body to the brain and spinal cord– Efferent (motor) nerves carry messages from brain

and spinal cord to muscles and glands

Peripheral Nervous System

• Consists of somatic and autonomic nervous system

• Somatic: 12 pairs of cranial nerves and 31 pairs of spinal nerves

• Autonomic : controls involuntary actions of body

Peripheral Nervous System: Somatic

• Responsible for sight, hearing, taste, smell• Touch, pressure, pain, temp• Send out impulses for voluntary and

involuntary muscle control

Peripheral Nervous System: autonomic

• Controls involuntary functions of nervous system

• 2 divisions: sympathetic and parasympathetic• Sympathetic nervous system: fight or flight-

prepares the body for action in time of emergency by increasing heart rate, blood pressure, respirations

• Parasympathetic nervous system: counteracts actions of sympathetic nervous system

Diseases of the Nervous System

Description, diagnostic tests, S&S, Tx, prevention if available•DHO: Cerebral palsy, CVA, encephalitis, epilepsy, hydrocephalus, meningitis, MS, neuralgia, paralysis, Parkinson’s Disease, Shingles•BS&F: Dementia, Alzheimer’s Disease, hematoma

Application: Diseases of the Nervous System

• Using Body Structures and Functions textbook, compare and contrast the following:

• 1. meningitis and encephalitis• 2. cerebral palsy and multiple sclerosis• 3. Parkinson’s Disease and essential tremors• 4. Dementia and Alzheimer’s Disease

Lou Gehrig’s Disease

• Amyotrophic Lateral Sclerosis (ALS)• Chronic, degenerative neuromuscular disease• S&S: initially, weakness and atrophy of

voluntary muscles followed by paralysis• Later stages: pt loses ability to communicate,

breathe, eat, move. However, mental acuity is unaffected

• no cure prognosis: 2-5 years

• Etiology of ALS

Carpal Tunnel Syndrome

• Painful hand and arm condition due to pinching of the median nerve in the wrist

• Caused by repetitive hand movements• S&S: pain, muscle weakness, impaired

movement, tingling of thumb, ring, and middle fingers

• Tx: anti-inflammatory meds, splinting, surgery to enlarge tunnel and relieve pressure on nerve

Cranial Nerves

• I olfactory• II optic• III oculomotor• IV trochlear• V trigeminal• VI abducens

• VII facial• VIII vestibulocochlear

(auditory)• IX glossopharyngeal• X vagus• XI spinal accessory• XII hypoglossal

Fxns of Cranial Nerves

• I olfactory smell• II optic vision• III oculomotor eyelid/eyeball

movement• IV trochlear turns eye downward and

lateral• V trigeminal face/mouth touch/chewing• VI abducens turns eye laterally

Fxns of Cranial Nerves (cont’d)

• VII facial facial expressions, tears, saliva, taste

• VIII vestibulocochlear (auditory) hearing• IX glossopharyngeal taste• X vagus stimulates dig. organs, taste• XI spinal accessory trapezius and

sternocleidomastoid• XII hypoglossal tongue

Application:

• Your group is to come up with a mnemonic to memorize cranial nerves AND a way to visually memorize functions of the cranial nerves.

Cranial Nerve Exam

• cranial nerve exam