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66 Cards in this Set

  • Front
  • Back
  • 3rd side (hint)

What are nerves?

  • Nerves are the master coordinating system of the body

  • All thoughts, actions and sensations are reflected in their activity

  • Conscious and unconscious life functions are regulated by nervous tissue

Basic Functions of the Nervous System

  1. Sensory (input) - sense changes both internal and external
  2. Integrative (what does it mean) - to interpret these changes
  3. Motor (do something) - react to changes

Parts of the Nervous System

  • Central Nervous System

- (Chara Never Sleeps)

- Brain and Spinal Cord

  • Peripheral Nervous System

- (Papyrus Never Stops)

- Cranial and spinal nerves

- Afferent system (incoming sensory)

- Efferent system (Outbound motor)


Central Nervous System

Two Types of Nervous Tissue Cells


Neuroglia (Glial Cells)


  • Functional Units of the Nervous System

  • Three distinct portions

  1. Cell body
  2. Axon
  3. Dendrites

Neuron - Cell Body

  • Contains the nucleus surrounded by cytoplasm with typical organelles

  • Many extensions from cell body called Dendrites (little trees)

  • Single long extension called Axon

Neuron - Dendrites

Typically short, tapering and highly branched

dendrites receive information from another neuron, or body structure such as muscle, gland or surface

  • Typically short, tapering and highly branched

  • dendrites receive information from another neuron, or body structure such as muscle, gland or surface

Neuron - Axon

  • Long, thin, cylindrical projections

  • conduct impulses towards another neuron, muscle or gland

  • end of axon made of terminals with end bulbs


  • A nerve is a bundle of axons and associated connective tissue & blood vessels with specific function and direction.


  • The site where 2 neurons or neuron and an effector (acting producing) cell communicate

  • End bulbs store chemicals called neurotransmitter


  • Chemical that transmits information from nerve cell to nerve cell

  • Odours, tastes, motions stimuli for some neurons

  • Acetylcholine is the neurotransmitter for muscle cells

Functions and Characteristics of Nervous Tissue


  • Respond to various electrical and chemical stimuli

  • Convert stimuli into nerve impulses (action potentials)

  • Conduct impulses to other neurons, muscle fibers or glands


  • "nerve glue"

  • Astrocytes - provides nutrients, maintain environment

  • Microglia - Protects CNS from disease, Phagocytes

  • Oligodendrocytes - forms myelin sheath for CNS neurons

  • Ependymal Cells - forms cerebrospinal fluid

  • Schwann Cells - forms myelin sheath of PNS neurons

Anatomy of an Axon

  • Axons are often covered in "insulation" to speed transmission and maintain integrity of pathway

  • Myelin Sheath is the phospholipid layer of insulating material surrounding axon

  • Myelin produced by Schwann Cells

Importance of Myelin

  • Insulation that keeps nerves separate from one another

  • Similar to covering of an electrical wire

  • Helps fine tine transmission

  • Myelin begins to form pre-natally, and continues to adolescence

  • Maturation of myelin sheaths responsible for enhanced coordination in maturing young

  • Diseases of neurons can destroy myelin and disrupt nerve transmission

Neuron Function

  • Nerves are said to "fire: when an impulse is conducted from one end of a neuron to the other.

  • When a nerve does fire several stages are involved:

  1. Resting state
  2. Depolarization
  3. Repolarization

Resting State

  • When a nerve is not being stimulated

  • Energy is required to maintain this state

  • Molecules on the neuron cell membrane are responsible for maintenance

  • Called the Sodium potassium pump

Sodium Potassium Pump

  • Pumps sodium ions (Na+) out of the neuron

  • Also pumps potassium ions (K+) in to the neuron

  • Na+ is not able to freely diffuse across cell membranes

Resting Membrane Potential

  • S-P pump maintain a difference in electrical charge across the cell membrane

  • This "difference" in charges is called Resting Membrane Potential


  • The "firing" of the neuron

  • Results in a loss of the difference in electrical charges

Action Potential

  • The big shift from negative to positive charge is called the: Action Potential


  • Period of recovery in which the ions are reorganized
  • Cell is re-polarized, but backwards
  • NaK pump has to get back to work


  • Threshold

  • The Wave

  • All or None principle

  • Refractory period


  • Not every stimulus is capable of making the neuron fire

  • Neuron has a minimum level of stimulation

  • Called the Threshold

Wave of Depolarization

  • Threshold stimulus causes a wave of sodium channels to open along the entire neuron

  • Called a Wave of Depolarization

  • A nerve impulse is actually the wave of depolarization traveling along the neuron

  • Also called conduction of the action potential

All or None Principle

  • When a neuron "fires"

  • It does so to the full extent of its ability

  • Therefore a neuron fires "to the max" or not at all

Refractory Period

  • A neuron will not fire if a stimulus arrives before it has returned to its resting state

  • This time of inability to respond is called The Refractory Period

  • Absolute Refractory Period
  • Absolutely no go

  • Relative Refractory Period
  • Strong stimulus at tail end

Speed of Transmission

  • Signals can travel along a myelinated neuron at speeds of up to 100m per second (350 kph)

  • Transmission along unmyelinated neurons is slower due to interference and leakage of electrical signal

Two Categories of Neurotransmitters

  • Excitatory

  • Causes depolarization of next neuron or target by helping approach threshold
  • Most body neurotransmitters are excitatory

  • Inhibitory

  • Causes next neuron or target to get even higher - hyperpolarize threshold, preventing firing
  • Tranquilizers work this way

The Brain

  • The principle parts of the brain are:

  • Cerebrum
  • Cerebellum
  • Diencephalon
  • Brain stem


  • Higher order thought, consciousness
  • Initiates voluntary movement, expresses conscious behaviours
  • Damage to Cerebrum

  • May cause abnormal movements, seizures, abnormal behaviours, hallucinations, loss of voluntary movement, inability to learn.


  • Smooths and coordinates muscle movements

  • Compares intended movements to what is actually happening

  • Damage to cerebellum from genetic, viral or bacterial causes results in hypermetria

  • Alcohol affects cerebellum


  • Consists of the thalamus, hypothalamus and pituitary

  • Hypothalamus region also
  • Regulates temperature, hunger &thirst, rage and anger responses

Brain "Stem"

  • Medulla Oblongata

  • Pons

  • Midbrain

  • Damage to brainstem can result in death from respiratory failur or CV collapse

The Brain - Protection

  • The brain is protected by cranial bones, cranial meninges, and cerebrospinal fluid

  • Meninges are 3 layers of connective tissue" dura mater, arachnoid and pia mater

  • Epidural anesthetics are injected around dura mater and bone in spinal area = decreased sensation without affecting brain functions

  • Inflammation of meninges = meningitis

Brain Blood Supply

  • Blood supply to brain is essential

  • If blood supply is interrupted for a short time, unconsciousness results

  • More than four minutes permanently damages neurons

  • Lysosomes break down, release their contents and self-destruct the brain cells. (stroke, brain injury)

Blood Brain Barrier

  • Separates nervous tissue itself from capillaries in the brain

  • Walls of brain capillaries have no fenestrations or openings like other capillaries

  • Glial cell membranes also assist in creating cellular barrier

  • The Blood Brain Barrier serves to let only glucose, oxygen, CO2 and some ions through.


Oh - Olfactory

Oh - Optic

Oh - Oculomotor

To - Trochlear

Touch - Trigeminal

And - Abducent

Feel - Facial

Very - Vestibulocochlear

Green - Glossopharyngeal

Vegetables - Vagus

A - Accessory

H - Hypoglossal

(Oh Oh Oh, To Touch And Feel Very Green Vegetables AH)

Comparison of Somatic and Autonomic Nervous Systems

  • Autonomic and Somatic nervous systems together comprise the Peripheral nervous system

  • Autonomic implies self-governing

  • Usually operates without conscious control of the brain

Autonomic Nervous System

  • Autonomic input is through sensory neurons which monitor internal conditions, such as blood CO2 level, degree of stretching of internal organs or blood vessels

  • The ANS regulates the activities of smooth muscle, cardiac muscle, and glands

Sympathetic vs. Parasympathetic Divisions

  • Parasympathetic division is principally concerned with activities that conserve energy.

  • Sympathetic division is concerned with activities that expend energy


  • Sympathetic division increases heart rate and inhibits digestive processes

  • Parasympathetic division enhances digestive processes and slows down heart rate

Spinal Cord

Gray Matter vs. White Matter

  • White matter refers to groupings of myelinated axons organized into sensory or motor tracts

  • Gray matter is a collection of unmyelinated nerve structures

Spinal Cord

  • Spinal cord conducts information via ascending and descending tracts.

  • Ascending tracts carry sensory information up the spinal cord toward the brain

  • Descending tracts conduct motor impulses from the brain down to the spinal cord and to the spinal nerves


  • Reflexes are the body's principal mechanisms for responding to certain changes in the internal and external environments

  • A reflex is a quick, involuntary response to a stimulus that passes through the reflex arc.

  • A reflex arc is the shortest route that can be taken by an impulse from a receptor to an effector.

  • Basic components are:
  • receptor
  • sensory neuron
  • integrating centre
  • motor neuron
  • effector

Withdrawal Reflex "Flexor" reflex

  • Protects us by causing immediate withdrawal of a limb from a source of injury, even before sensing pain.

Corneal Reflex

  • Basic and common indicator of depth of anesthesia

  • As anesthetic depth increases, pons of brain becomes less responsive and corneal reflex also becomes less responsive


  • Does not measure vision

  • Measures retinal response, CN2 integrity, diencephalon and CN3

The General Senses

  • Visceral Sensation
  • Touch
  • Temperature
  • Pain
  • Proprioception

Visceral Sensations

  • Hollow organs:

  • Stretch causes Pain (cramps)
  • Except the urinary bladder

Touch (Tactile sense)

  • Provides a "window" for CNS to be aware of contact

  • Constant pressure fades to subconscious
  • Aware of sever or abrupt contact
  • pressure receptors throughout integument

Temperature Sense

  • Monitoring system for body's temperature control
  • Prevents hypo and hyper thermia

  • Receptors are Superficial or Deep

  • Superficial (in the skin) - detects rise or fall of temperature

  • Deep - monitoring of blood temperature. receptors in hypothalamus

Corrective Actions

  • Alter blood flow
  • Sweating
  • Piloerection
  • Shivering
  • Thyroid hormone
  • Seek heat or cold


  1. Transduction - stim converted to impulse at sensory nerve ending
  2. Transmission - nerve fiber to spine
  3. Modulation - Change degree of pain in spine
  4. Perception - Spine to brain


  • Awareness of body position and movement

  • Receptors in muscles, tendons and joints

  • Important for posture and movement

5 Special Senses

  • Taste
  • Smell
  • Hearing
  • Equilibrium
  • Vision

Gustation (Taste)

  • Gustatory receptor cells are called taste buds

  • Interact with sense of smell

  • Substance to be tasted must be in a solution of saliva

  • If animal can't smell, they won't want to eat

Olfaction (Smell)

  • Receptors in mucous membranes of nasal cavity

  • Most highly evolved in dogs
  • cats - 19 M receptors
  • dogs - 147 M receptors
  • Human - 5 M receptors

  • Olfactory cells mixed with supporting cells


  • A dog can hear sounds 250 meters away

  • Dogs have twice as many muscles for moving their ears as people

  • The ear consists of three anatomical subdivisions: The external ear- comprised of the pinna, external auditory canal, and the eardrum
  • middle ear- Small air-filled cavity, connected to pharynx by Eustachian Tube
  • and the internal ear - Comprised of a series of canals. Outer bony labyrinth and an inner membranous labyrinth that fits into the bony labyrinth


  • When dizzy or head spins, your equilibrium was affected

  • Includes information from inner ear, eyes and somatic proprioceptors

  • Brain gets impulses about rotary motion


  • Eye Words"
  • Ocular
  • Opthalm

  • Vision is associated with a single layer of photoreceptors

Anatomy of the Eye

  • The eye is constructed of 3 layers

  • Outer fibrous layer,
  • Sclera and cornea

  • Middle vascular layer,
  • Choroid, iris, ciliary body

  • Inner nervous layer
  • Retina

Rods & Cones

  • Photoreceptors cells are either rods or cones

  • There are many more rods than cones present in most species including humans

  • Rods detects shades of gray and light

  • Cones stimulated in brighter light, detect colours

Image Formation

  • Refraction of Light
  • Bending rays upon entering eye and traveling through transparent substances such as cornea, aqueous humor, lens, vitreous humor

  • Accommodation
  • Change in shape of lens in relation to angle of light rays

  • Constriction of Pupil
  • Autonomic response causes contraction of circular muscle of iris

  • Convergence
  • Ability of eye to focus on one object

  • Inverted Image Formation
  • Refraction causes images to be inverted (upside down)

Extraocular Structures

  • Conjunctive

  • eyelids

  • tear production & drainage system

  • Extraocular muscles