Nervous System

Nervous System Functions

1. Sensory – incoming signals2. Motor - movement3. Integrative – in brain and

spinal cord only (processors/relay terminals)

Parts of a Neuron• Soma – cell body• Dendrite – receives messages• Axon – send messages out• Myelin – help speed up messages, made up of

Schwann cells

Divisions of the Nervous System

• Central Nervous System• Peripheral Nervous System

–Somatic–Autonomic–Enteric

Central Nervous System

• Brain• Spinal Cord

Control center, coordinates body functions

Peripheral Nervous System

Carry messages to and from CNS

Motor and sensory neurons found here.

Made of 3 Basic Divisions - Somatic, Autonomic, Enteric

Somatic Nervous Division

• Cranial and spinal nerves• Reflexes – automatic

responses to stimuli• Body Functions – sensory and

motor

Autonomic Nervous Division

• Involuntary• Two divisions

–Sympathetic – fight-or-flight responses, speeds up reactions

–Parasympathetic – counteracts sympathetic, returns body to normal, slows down heart rate

Enteric Nervous Division

- Intestines- directly controls the

gastrointestinal system

Brain

• Weighs approx. 3 lbs• 4 parts

–Brain stem–Diencephalon–Cerebrum–cerebellum

Brain

Cerebrum

Corpus Callosum

Pituitary Gland

HypothalamusBrain Stem: Pons, Midbrain, Medulla Oblongata

Cerebellum

Thalamus

Brain Stem – 3 parts

• Continuous with spinal cord• Medulla oblongata • Midbrain • Pons – (bridge)

Diencephalon – 2 parts•Thalamus

– Principle relay station for sensory impulses and cognition

•Hypothalamus – homeostasis– Control of Autonomic Nervous System– Control of pituitary gland– Regulation of emotional and behavioral patterns– Regulation of eating and drinking– Control of body temperature– Regulation of circadian rhythms and states of

consciousness

CerebrumFunctions of the 4 lobes

• Frontal – reasoning, movement, higher level cognition, language

• Parietal – Pressure, Touch, Pain, Somatosensory Cortex (sensation processing)

• Temporal – Primary Auditory Cortex, Hippocampus (memories)

• Occipital – Interpreting visual information

Cerebral Cortex - Sensory

• Located in the Temporal lobe• Primary somatosensory area – receives

nerve impulses for touch, proprioception, pain and temperature

• P. visual area - vision• P. auditory area - hearing• P. gustatory area - taste• P. olfactory area - smell

Cerebral Cortex - Motor• Location - Cerebullum• P. motor area – movement• Broca’s speech area – frontal – speech

– Aphasia – inability to speak– Agraphia – inability to write– Word deafness – inability to understand

spoken words– Word blindness – inability to understand

written words

Cerebral Cortex - Association• Somatosensory Association Area

– interpret and integrate somatic senses

• Visual Association Area– takes past visual experiences and relates

them to current visual experiences

Auditory Association Area– speech, music, or noise

• Wernicke’s Area – interprets the meaning of speech by translating

words into thoughts

Cerebral Cortex – Association cont.d

• Common Integrative Area– receives, integrates, and relays sensation

impulses

• Premotor Area– motor sequences- ability to write words

• Frontal Eye Field Area– controls voluntary scanning movements of the

eye

Cerebrum – Memory

• Ability to recall thoughts• Controlled by the Limbic System• Stored in the temporal lobe

i.Short-term memory – seconds or hours

ii.Long-term memory – days to years

Cerebrum – 2 hemispheres

• Left Hemisphere– Controls right side of body, spoken and

written language, numerical/scientific skills, reasoning

• Right Hemisphere– Controls the left side of the body, Musical,

artistic, spatial and pattern perception, mental images of sight, sound, touch, smell and taste

Cerebullum

• 2nd largest part of the brain• Compares intended movements

by the motor areas with what is actually happening

• Balance and Coordination•Ataxia – disruption of muscle

coordination

Spinal Cord Protection• 4 layers – outside in

– Wall of Vertebral Canal (bone)– Meninges – 3 layers of connective

tissues that protect the brain and spinal cord•Dura mater, Arachnoid, Pia mater

– Cerebrospinal Fluid– Vertebral ligaments

Spinal Cord Protection• Meninges

– Dura – outermost, durable•Epidural Space – between dura mater and

vertebral column•Arachnoid - (middle layer, named because of

its delicate spider’s web arrangement of collagen and elastic fibers) – continuous with cranial arachnoid

•Pia Mater – innermost layer, made of collagen and elastic fibers

–Sub arachnoid space – between Pia mater and Arachnoid – location of spinal taps to remove Cerebrospinal Fluid

–Spinal Tap – can also be used to administer antibiotics, anesthetics and chemotherapy.

Meninges

12 Cranial NervesName Motor, Sensory,

BothFunction

Olfactory Sensory Smell

Optic Sensory Vision

Occulomotor Motor Eye movement

Trochlear Motor Eye movement

Trigeminal Mixed Facial movements

Vestibulococchlear Sensory Equilibrium, Hearing

Glossopharyngeal Motor Swallowing

Abducens Motor Eye Movement

Facial Mixed Facial Expressions

Vagus Mixed Swallowing and Talking

Accessory Motor Movement of head, neck, back and throat

Hypoglossal Motor Tongue Movement

Special Senses

• Smell• Taste• Sight• Hearing• Equilibrium

Eye Anatomy to KNOW

–Cornea, Lens, Retina, Iris, Pupil, Rods and Cones, Sclera, Choroid Coat, Vitreous Humor, Aqueous Humor

• Lacrimal glands – secrete tears that destroy bacteria

• Sclera – white of eye

• Cornea - transparent

• Retina

Visual Pathway

• Cornea – Lens – Retina – Rods and Cones – Optic Nerve – Optic Tract - Optic Chiasm – Optic Radiations - Primary Visual Cortex in the Occipital Lobe

Vision Facts

• Emmetropic Eye – normal vision, normal shape

• Myopic Eye – Nearsightedness, Distant objects are blurry

• Hypermetropic Eye – Farsightedness, Near objects are blurry.

• Rods and Cones – process color

Speed of Processing Theory: interference because words are read faster than colors are named.

Selective Attention Theory: the interference because naming colors requires more attention than reading words.

Ear Anatomy to KNOW

–Auricle, External Auditory Canal, Tympanic Membrane, Malleus, Incus, Stapes, Oval Window, Cochlea, Round Window

The EAR

External Ear

• Hearing only• Lined with skin• Ceruminous (wax) glands are present• Ends at the tympanic membrane

Pinna (auricle)

External auditory canal

Middle Ear• Tympanic Cavity/Tympanic Membrane• Contains the Eustacian tube - connects the

middle ear with the throat– Equalizes pressure during yawning or

swallowing– Three bones span the cavity

• Malleus (hammer)• Incus (anvil)• Stapes (stirrup)

Middle Ear

Vibrations from eardrum move the malleus

The bones transfer sound to the inner ear

Inner Ear

Maze of Chambers

Cochlea

Vestibule

Semicircular canals

Auditory Pathway• Auricle – External Auditory Canal – Tympanic

Membrane – Malleus – Incus – Stapes – Oval Window – Cochlea – Choclear Nerve – Medula Oblongata – Pons – Midbrain – Thalmus – Temporal Lobe of the Cerebral Cortex

• Howhearingworks