THE NERVOUS SYSTEM

A. TWO PARTS Central Nervous System(CNS)-

brain/spinal cord Peripheral Nervous System(PNS)-nerves

through the body 31 pairs of spinal nerves 12 pairs of cranial nerves

B. 3 BASIC FUNCTIONS1. Sensory- gathers info

- receptors of PNS send signals to CNS2. Integrative- info is brought together

- interpreted, create sensations, create thoughts, add to memory, make decisions

3. Motor – response to signals (impulses) Signals sent from CNS to muscles/glands Homeostasis- maintain stable conditions

MOTOR: Somatic Nervous System- skeletal

muscles Autonomic Nervous System- smooth

muscles, glands

C. NEURONS-NERVE CELLS Body with many extensions(nerve

fibers) that conduct impulses 2 types of processes

Dendrites- shorter more numerous Receive input

Axons- single long fiber Conducts impulse away

D. NEUROGLIAL CELLS Support tissue of the nervous system 5 Types1. Microglial : scattered throughout,

digest debris or bacteria

2.  Oligodendrocytes:  provide insulation around the axons

Creates myelin sheath that insulates axons

3. Astrocytes:  connect blood vessels to neurons

4.  Ependymal Cells:  form a membrane that covers brain-like parts

5.  Schwann cells:  form the insulating sheath around the neurons within the PNS

*Myelin Sheaths - necessary for insulation of neurons

NEURON STRUCTURE Cell body- contains cellular organelles Neurofibril -  fibers- support organelles Chromatophilic substance (rough ER) -

transport system Myelin -insulation surrounding axons Nodes of Ranvier - gaps in the

insulation Synaptic cleft- space between neurons

WHITE VS GREY MATTER Myelinated (white matter) – myelinated

axons Unmyelinated (grey matter) -

unmyelinated

ALL NEURONS DO THREE THINGS:1. Receive a signal.

Can be any type of stimulus (change in environment, signal from another neuron, etc).

2. Transmit a signal to another location. Ex: finger touching something • signal to spinal

cord or brain.3. Stimulate another cell

Another neuron • transmit signal Muscle • contraction Gland • secretion

CLASSIFICATION OF NEURONSStructural

- Multipolar- Bipolar- unipolar

Functional- sensory neurons- motor neurons- interneurons

Nerve- bundle of nerve fibersNerve Impulse- weak electric current

- series action potential along a nerve

SYNAPSE Presynaptic neuron- brings impulse to

synapse Postsynaptic neuron- neuron

stimulated/inhibited by impulse Synaptic Transmission- signal

Axon end- hold neurotransmitter

NEUROTRANSMITTERS Excitatory - increase membrane

permeability, increases chance for threshold to be achieved

Inhibitory - decrease membrane permeability, decrease chance for threshold to be achieved

Synaptic Transmission Dendrite cell body axon synapse

STEPS1. Neuron membrane maintains resting potential2. Threshold stimulus is received3. Sodium channels open4. Sodium ions diffuse inward, depolarizing the

membrane5. Potassium channels open6. Potassium ions diffuse outward, repolarizing

membrane7. Resulting action potential causes a local bioelectric

current that stimulates adjacent portions of membrane

8. Wave of action potentials travel the length of the axon as a nerve impulse

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

http://outreach.mcb.harvard.edu/animations/actionpotential.swf

TYPES OF NEUROTRANSMITTERS Acetylcholine - stimulates muscle

contraction Monoamines - Norepinephrine &

Dopamine (sense of feeling good, low levels = depression)

Serotonin (sleepiness) Endorphins (reduce pain, inhibit

receptors)

DRUGS THAT AFFECT NEUROTRANSMITTERS

Curare Strychnine Cocaine, morphine, alcohol, ether and

chloroform Mescaline and LSD Ecstasy

ANTIDEPRESSANTS Zoloft is part of a class of drugs called

selective serotonin reuptake inhibitors, or SSRIs for short. SSRIs act on a specific chemical within the brain known as serotonin. This is one of several chemicals used to send messages from one nerve cell to another.

IMPULSE PROCESSING Neuronal pool- Groups of neurons

making synaptic connections to perform a common function

TYPES OF NERVES Sensory Nerves - conduct impulses into

the brain or spinal cord Motor Nerves - carry impulses to

muscles of glands Mixed Nerves - contain both sensory

and motor nerves

NERVE PATHWAYS

Receptor-Detects stimulus

Sensory/Afferent Neuron

Central Nervous System-

processes informationMotor/Efferent

NeuronMuscle or Gland- reacts

NERVE PATHWAYS Reflex Arc- simple pathway, includes

few neurons Reflex- simplest response Reflex Behavior- automatic,

subconscious response to stimuli Sneezing, heart beat, vomiting, digestion

Knee-jerk reflex- stimulus knee- sensory nerve-spinal cord-motor nerve

Withdrawal reflex- occurs when you touch something painful

http://www.intelligencetest.com/reflex/index.htm

CENTRAL NERVOUS SYSTEM Brain = cranial cavity spinal cord= vertebral canal Protection= Mengines- membranes locatedbetween bone and soft tissue

of nervous system

MENINGES- 3 LAYERS Dura mater- outermost layer, blood

vessels, nerves Arachnoid mater- no blood vessels,

inbetween layer Pia mater- inner layer, contains many

nerves and blood vessels to nourish cells

LAYER OF DURA MATER

Cerebrospinal fluid= between arachnoid and pia maters

SPINAL CORD Nerve column, passes from brain down

through vertebral canal 31 segments – each with a pair of

spinal nerves Spinal nerves- branch to various body

parts

Cervical enlargement- supplies nerves to upper limbs (neck)

Lumbar enlargement- lower back, supplies nerves to lower limbs

FUNCTION OF SPINAL CORD Conduct impulses, serves as center for

reflexes

Ascending tracts= carry sensory info to brain

Descending tracts= carry motor impulses from the brain to muscles/glands

Spinal reflexes- reflex arcs pass through the spinal cord

BRAIN Cerebrum – largest, sensory and motor

functions, higher mental function (memory, reasoning)

Cerebellum – coordinate voluntary muscles

Brain stem – regulate visceral functions

Balance and Coordination

STRUCTURES OF THE CEREBRUM1. Cerebral hemispheres- mirror images2. Corpus callosum- nerve fibers that

connect hemispheres

3.CONVOLUTIONS OF THE BRAIN Wrinkles and Grooves of the brain

gyri- ridges on brain Sulcus- deep grooves Fissure- very deep groove

4. FISSURES Longitudinal fissure - separate right and

left sides Transverse fissure- Separates cerebrum

from cerebellum

Lateral fissure- separates the temporal lobe from the Frontal and Parietal lobes

LOBES OF THE BRAIN5. Frontal – reasoning, thinking, language6. Parietal – touch, pain, relation of body

parts (somatosensory)7.  Temporal Lobe – hearing 8.  Occipital – vision9. Cerebral Cortex - thin layer of gray

matter that is the outermost portion of cerebrum (the part with all the wrinkles)

FUNCTIONAL AREAS OF BRAIN1. Motor- controls voluntary movements

- the right side of the brain generally controls the left side of the body

-also has Broca's Area (speech)

2. Sensory Area-involved in feelings and sensations

(visual, auditory, smell, touch, taste)

Sensory HomunculusThis model shows what a man's body would look like if each part grew in proportion to the area of the cortex of the brain concerned with its sensory perception.

3. Association Areas- higher levels of thinking, interpreting and analyzing information

BRAIN STEM- 3 PARTS Midbrain – visual reflexes, eye

movements Pons - relay sensory information Medulla Oblongata– heart, respiration,

blood pressure

Diencephalon1. Hypothalamus – regulates hormones,

heart rate, blood pressure, body temp, hunger, sleep

2. Thalamus - relay station

Optic Tract / Chiasma - optic nerves cross over each other

MEMORY: HIPPOCAMPUS Memory is controlled by the

HIPPOCAMPUS The hippocampus plays a major role in

forging memories.

EMOTIONS: LIMBIC SYSTEM The prefrontal lobe and the hippocampus are part of

a system of structures in the brain. The LIMBIC SYSTEM also includes olfactory lobes.

Therefore, memory, emotion, and smell are linked. Crayolas are created today with the same scent

because it reminds people of their happy times in childhood.

Why is the brain formed so that smell and emotions are tied together? Because pheromones are tied to emotions and behavior, so they need the link.

MEMORY We used to classify memory as being

long-term or short-term. The new classification is four memory systems that process information for storage and retrieval:

Episodic, Semantic, Procedural, and Working.

EPISODIC Involved in remembering personal

experiences, such as a phone conversation you had yesterday or the movie you watched last week.

SEMANTIC Manages the storage and retrieval of general

knowledge of facts, such as the number of days in a year or the colors in a rainbow.

People with problems in this system may have difficulty in naming an object or describing a named object.

Semantic Memory Tasks 1. What month comes after October? 2. Where do Kangaroos live? 3. What actor played the Joker in the last Batman

movie?

PROCEDURAL Allows us to learn activities and skills

that will then be performed automatically with little or no conscious thought. Examples are riding a bicycle or driving a

car. Problems with this system leads to loss of

skills or significant difficulties in learning new skills.

WORKING Governs attention, concentration, and short-

term retention. Problems here can impair her a person's

ability to pay attention or to accomplish multi-step tasks.

Working Memory Tasks 1. Labeling a skeleton (remember that chapter?) 2. Describing the parts of the brain. 3. List all the things you ate yesterday. Test Working Memory

PHINEAS GAGE