The nervous system

Allows for communication between cells through sensory input, integration of data and motor output

neurons and neuroglia

takes impulses from sensory receptor to CNS

receive information in the CNS and send it to a motor neuron

takes impulses from the CNS to an effector (i.e. gland or muscle fiber)

main cell where organelles and nuclei reside

many, short extensions that carry impulses to a cell body

single, long extension that carries impulses away from the cell body

A lipid covering on long axons that acts to increase the speed of nerve impulse conduction, insulation and regeneration in the PNS

neuroglia that make up the myelin sheath in the PNS

gaps between myelination on the axons

conduction of the nerve impulse from node to node

when the axon is not conducting a nerve impulse

rapid change in the axon membrane that allows a nerve impulse to occur

• •Sodium gates open letting Na+ in
• •Depolarization occurs
• •Interior of axon loses negative charge (+40mV)

• •Potassium
• gates open letting K+ out
• •Repolarization occurs
• •Interior of axon regains negative charge (-65mV)
• •Wave of depolarization/repolarization travels down the axon
• •Resting potential is restored by moving potassium inside and sodium outside

• A small gap between the sending neuron (presynaptic membrane) and the receiving neuron (postsynaptic membrane)
• •Transmission is accomplished across this gap by a neurotransmitter (e.g. ACh, dopamine and
• serotonin)
• •Neurotransmitters are stored in synaptic vesicles in the axon terminals

• •Nerve impulse reaches the axon terminal
• •Calcium ions enter the axon terminal that stimulate the synaptic vesicles to fuse with
• the presynaptic membrane
• •Neurotransmitters are released and diffuse across the synapse and bind with the postsynaptic membrane to inhibit or excite the neuron

• •Integration is the summation of the inhibitory and excitatory signals received by a postsynaptic neuron
• •This occurs because a neuron receives many signals

• –Central
• nervous system (CNS): Brain and spinal cord

• –Peripheral
• nervous system (PNS): Nerves and ganglia (cell bodies)

•Consists of the brain and spinal cord

• •Bones – skull and
• vertebral column

•Meninges – 3 protective membranes that wrap around CNS

• •Cerebral
• spinal fluid (CSF)
• – space between meninges is filled with this
• fluid that cushions and protects the CNS

• •Gray
• matter – contains cell
• bodies and nonmyelinated fibers

• •White
• matter – contains myelinated axons

• •Extends
• from the base of the brain and along the length of the vertebral canal formed
• by the vertebrae

• •Functions
• to provide communication between the brain and most of the body

• •Center
• for reflex arcs

• •Gray
• matter in the center is a butterfly shape

• •White
• matter surrounds the gray matter

1.Cerebrum

2.Diencephalon

3.Cerebellum

4.Brain stem

•Cerebral hemisphere

•Cerebral cortex

•Primary motor and sensory areas of the cortex

•Association areas

•Processing centers

•Central white matter

• •Cerebrum
• – largest portion of the brain

• •Frontal
• lobe: primary motor area
• and conscious thought

• •Temporal
• lobe: primary auditory,
• smell and speech area

• •Parietal
• lobe: primary somatosensory and taste area

• •Occipital
• lobe – primary visual area

thin, outer layer of gray matter

-Primary motor area – voluntary skeletal muscle

-Primary somatosensory area – sensory information from skeletal muscle and skin

-Association areas – integration occurs here

• -Processing centers – perform higher level analytical
• functions including Wernicke’s and Broca’s areas both involved in speech

•Includes the:

• •Hypothalamus –
• helps maintain homeostasis (hunger, sleep, thirst, body temperature and water balance) and controls pituitary gland

• •Thalamus –
• 2 masses of gray matter that receive all sensory input except smell; involved in memory and emotions

• •Pineal gland –
• secretes melatonin that controls our daily rhythms

•Receives and integrates sensory input from the eyes, ears, joints and muscles about the current position of the body

•Maintains posture

•Coordinates voluntary movement

• •Allows learning of new motor skills (i.e. playing the
• piano or hitting a baseball)

•Includes:

• •Midbrain –
• relay station between the cerebrum and spinal cord or cerebellum; reflex center

• •Pons – a bridge between
• cerebellum and the CNS; regulate breathing rate; reflex center for head
• movements

• •Medulla oblongata –
• reflex centers for regulating breathing, heartbeat and blood pressure

• •Reticular formation – major component of the reticular activating system
• (RAS) that regulates alertness

• •Joins primitive emotions (i.e. fear, pleasure) with higher functions such as
• reasoning

• •Can cause strong emotional reactions to situations but conscious thought can
• override and direct our behavior

•Includes:

•Amygdala – has emotional overtones

•Hippocampus – important to learning and memory

•Learning – what happens when we recall and use past memories

•Memory – ability to hold a thought or to recall past events

• •Short-term memory – retention of
• information for only a few minutes

• •Long-term memory – retention of
• information for more than a few minutes and include the following:

•Episodic memory – persons and events

•Semantic memory – number and words

•Skill memory – performing skilled motor activities (i.e. riding a bike)

•Language – depends on semantic memory

•Includes cranial (12 pr) and spinal nerves (31 pr) and ganglia outside the CNS

-Spinal nerves conduct impulses to and from the spinal cord

-Cranial nerves conduct impulses to and from the brain

• •Divided into 2
• systems:

-Somatic

-Autonomic

•Serves the skin, skeletal muscles and tendons

•Automatic responses are called reflexes

• •Regulates the
• activity of involuntary muscles (cardiac and smooth) and glands

•Divided into 2 divisions:

–Sympathetic: coordinates the body for the “fight or flight” response by speeding up metabolism, heart rate and breathing while slowing down and regulating other functions

–Parasympathetic: counters the sympathetic system by bringing up a relaxed state by slowing down metabolism, heart rate and breathing and returning other functions to normal

Both pharmaceuticals and illegal drugs have several basic modes of action:

•Promote the action of a neurotransmitter

•Interfere with or decrease the action of a neurotransmitter

•Replace or mimic a neurotransmitter or neuromodulator

•Most drug abusers take drugs that affect dopamine and thus artificially affect this reward circuit to the point they ignore basic physical needs in favor of the drug

•Drug abusers tend to show a physiological and psychological effect

•Once a person is physically dependent they usually need more of the drug for the same effect because their body has become tolerant

• •Alcohol – a depressant
• directly absorbed from the stomach and small intestine

•Most socially accepted form of drug use

•About 80% of college-aged people drink

•Alcohol denatures proteins, causes damage to tissues such as the brain and liver; chronic consumption can damage the frontal lobe

•High blood alcohol levels can lead poor judgment, loss of coordination or even coma and death

•Nicotine – stimulant derived from tobacco plant

• -Causes neurons to release dopamine that helps lead to
• dependence

–Adversely affects a developing embryo or fetus

–Increases heart rate and blood pressure

–Psychological and physiological dependency




•Cocaine – stimulant derived from a plant

• –Results
• in a rush sensation (5-30 minutes) and an increased sex drive

–Results in hyperactivity and little desire for food and sleep

–Extreme physical dependence with this drug

–“Crack” is a street name for cocaine that is processed to a free base for smoking

•Powder form is called speed and crystal form is called meth or ice

•A stimulant that reverses the effects of fatigue and is a mood elevator

•High agitation is common after the rush and can lead to violent behavior

•Causes psychological dependency and hallucinations

•“Ecstasy” is the street name for a drug that has the same effects as meth without the hallucinations

•Heroin: depressant from the sap of the opium poppy plant

•Leads to a feeling of euphoria and no pain because it is delivered to the brain and is converted into morphine

•Side effects are nausea, vomiting and depression of the respiratory and circulatory systems

•Can lead to HIV, hepatitis and other infections due to shared needles

•Extreme dependency

•Marijuana: psychoactive drug derived from a hemp plant called Cannabis

•Most often smoked as a “joint”

•Mild euphoria and brain damage

•Alterations to vision and judgment as well as impaired motor coordination with slurred speech

•Heavy users may experience depression, anxiety, hallucinations, paranoia and psychotic symptoms

•Banned in the US in1937 but recently has been legalized in a few states for medical use in seriously ill patients.

–Should marijuana be available to more patients? Why or why not?

–Should people in states where it is legal for medical purposes to be prosecuted?

–How should the use of medical marijuana be regulated?