The Nervous System Functions of the Nervous System

The Nervous System

Functions of the Nervous System • Sensory - gathers info • Integrative - information in brought together to be processed and interpreted • Motor - responds to signals, homeostasis • Short term coordination of all other organ systems’ activities • Reflex responses (You don’t have to think about it. )

Organization of the Nervous System • Central Nervous System (CNS): includes the brain and spinal cord. • Acts as the integrating and command centers • Interpret incoming sensory information and issue instructions • 98% of all neurons located here • Peripheral Nervous System (PNS): includes the nerves of the body • Act as communication lines that link all parts of the body

Organization of the Nervous System Figure 12. 2

The PNS is split into two subdivisions: Somatic Nervous System - allows us to consciously control our skeletal muscles (voluntary nervous system) Autonomic Nervous System - Regulates events that are automatic like smooth muscles, cardiac muscles and glands (involuntary nervous

NOTES – THE PERIPHERAL NERVOUS SYSTEM (PNS) Autonomic Nervous System 1. Sympathetic - homeostasis and the body at rest and is responsible for the body's "rest and digest" function. 2. Parasympathic - controls the body's responses to a perceived threat and is responsible for the "fight or flight" response.

Types of Cells in the Nervous System

Neurons The type of nerve cell that transmits information Major parts of a neuron: 1. Cell Body – main part of cell that contains the nucleus 2. Dendrites – short extensions from the cell body, numerous, receive information 3. Axons – single, long “fiber” which conducts impulse away from the cell body, sends information

4. Myelin -insulation surrounding axons 5. Nodes of Ranvier - gaps in the insulation 6. Schwann cell- is the small cells made up of myelin sheaths that support nerve cells in the PNS.

The Nerve Cell • Also called Neurons • Highly specialized cell • They cannot do mitosis (Can’t reproduce) • Born with all you are going to get

Neuroglial Cells - provide support for neurons 1. Microglial Cells: scattered throughout, digest debris or bacteria Microglial cells respond to immunological alarms

2. Oligodendrocytes: provide insulation around the axons

3. Astrocytes: connect blood vessels to neurons I connect to blood vessels

Neuroglial Cells (p 208) 4. Ependymal Cells: form a membrane that covers brain-like parts

5. Schwann cells: form the insulating myelin sheath around the neurons Practice with neuroglia coloring!

• Cerebral White Matter • functions to provide communication between cerebral areas • Myelinated axons • also provides communication between cerebrum and the rest of the brain

• Cerebral Grey Matter • contains the cell bodies, dendrites and axon terminals of neurons, so it is where all synapses are (unmyelinated) • Called soma

Interesting Facts about the Neuron • Longevity – can live and function for a lifetime • Do not divide – fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception • High metabolic rate – require abundant oxygen and glucose The nerve fibers of newborns are unmyelinated - this causes their responses to stimuli to be course and sometimes involve the whole body. Try surprising a baby!

Label the Diagram

Types of Neurons • Motor – carry information from the brain to the body • Sensory – carry the information from the body to the brain • Association – found only in the brain; transfers information from the sensory to the motor

Neurons Classified by Function: Sensory vs. Motor Neurons Figure 12. 11

Transmission of a Nerve Impulse 1. The dendrites are stimulated. Stimulation can come from light, sound, pressure receptors or your other senses, but most of the time they are stimulated from other neurons.

Transmission of a Nerve Impulse 2. Sodium channels open. – Normally (when a nerve is at rest) it is positive on the outside and negative on the inside because Sodium (NA) is on the outside and Potassium (K) is on the inside. – When stimulated sodium channels open allowing the positive sodium to flow in. This changes the charge or polarity in the cell.

Nerve Impulses At rest, the inside of a neuron's membrane has a negative charge. As the figure shows, a Na+ / K+ pump in the cell membrane pumps sodium out of the cell and potassium into it. However, more potassium ions leak out of the cell. As a result, the inside of the membrane builds up a net negative charge relative to the outside. Animations of Nerve Impulses http: //highered. mcgrawhill. com/sites/0072495855/student_ view 0/chapter 14/animation __the_nerve_impulse. html http: //outreach. mcb. harvard. edu/ animations/actionpotential. swf

Transmission of a Nerve Impulse 3. The membrane is depolarized • Depolarization is when the membrane of the neuron changes so that now the inside is more positive than the outside. • If the stimulus is strong enough, this causes the polarity to completely change and starts an action potential.

Transmission of a Nerve Impulse 4. An ACTION POTENTIAL is generated. • An action potential is also called a nerve impulse • Nerve Impulses are an ALL or NONE response. If enough stimulus occurs then the nerve impulse will fire down the whole axon. It will not go half way or die out. When started it happens down the whole

Transmission of a Nerve Impulse 5. The Action Potential reaches the axon terminal.

Transmission of a Nerve Impulse 6. Neurotransmitters are released – Excitatory transmitters - increase membrane permeability, increases chance for threshold to be achieved – Inhibitory transmitters- decrease membrane permeability, decrease chance for threshold to be achieved

Types of Neurotransmitters: • Acetylcholine - stimulates muscle contraction • Norepinephrine & Dopamine (sense of feeling good, low levels = depression) • Serotonin (sleepiness) • Endorphins (reduce pain, inhibit receptors)

Transmission of a Nerve Impulse 7. The membrane of the post synaptic neuron is activated. The whole process then starts over with the next neuron.

THE BRAIN

Major Divisions of the Brain • 1. Cerebrum • 2. Diencephalon • 3. Brain Stem • 4. Cerebellum

The Cerebrum • Location: The most superior part of the brain (the top part). Takes up the most room. Has all the wrinkles in it.

The Cerebrum What are all the bumps in it? Gyrus = bump Sulcus = shallow groove Fissures = deep grooves that separate the lobes of the brain

1. Longitudinal fissure - separates right and left sides

2. Transverse Fissure – separates cerebrum from cerebellum

3. Lateral Fissure separates the temporal lobe from the Frontal and Parietal lobes

The Cerebrum • Functions of the Cerebral Cortex: – Controls speech, memory, logical and emotional response, consciousness, interpretation of sensation, and voluntary movement • It is split into 4 major lobes

The Cerebrum • Lobes of the cerebrum: – Frontal – reasoning, thinking, language – Parietal – touch, pain, relation of body parts (somatosensory) – Temporal Lobe – hearing – Occipital – vision

The Cerebrum • Specialized areas of the cerebrum – Broca’s area- responsible for speech usually located only in the left side. Damage to this area causes the inability to say words properly (you know what you want to say but you can’t vocalize the words).

The Cerebrum • Specialized areas of the cerebrum – Basal Ganglia- help regulate volunteer motor activities by stopping or starting movement. It modifies instructions sent to the skeletal muscles. – Parkinson’s disease and Huntington’s disease are disorders of the basal ganglia. (page 253254)

The Cerebrum • Specialized areas of the cerebrum – Corpus Collosum-connects the left and right hemispheres

Take the Left Brain – Right Brain Test

The Diencephalon • Location: Under the cerebrum, in the middle of the brain. It sits on top of the brain stem.

Parts of the Diencephalon 1. Thalamus - relay station for sensory impulses passing to the sensory cortex for interpretation

Parts of the Diencephalon 2. Hypothalamus – most important regulatory center of the autonomic nervous system -controls temperature, water balance, & metabolism - also controls many drives and emotions (thirst, appetite, sex, pain, and pleasure centers)

Parts of the Diencephalon -Pituitary Gland: The "master gland" of the endocrine system. It controls hormones. Ex: growth hormone -Pineal Gland: secretes melatonin (for sleep)

Thalamus Pineal gland Hypothalamus Corpus callosum

THE BRAINSTEM Location: Bottom of the brain leading to the spinal cord. Is about 3 inches long and the width of your thumb.

THE BRAINSTEM Parts of the Brainstem: Midbrain- visual reflexes, eye movements Pons- relay sensory information Medulla Oblongata- regulates breathing, heart rate, blood pressure

Medulla Oblongata Pons Midbrain

CEREBELLUM Location: lower, back of brain. It is under the occipital lobe.

CEREBELLUM • Function: Balance and coordination

Protection of the Brain The Meninges & Cerebral Spinal Fluid

• The Meninges • 3 membranes that cover and protect the brain & spinal cord 1. Dura Matter • tough connective tissue

2. Arachnoid • thin, transparent, no blood vessels

3. Pia Matter • Cerebrospinal Fluid (CSF) • inner membrane, delicate, contains many blood vessels – nourishment for cells of the cord • watery broth similar to blood plasma, important in protection of nervous tissue

The Meninges Figure 13. 25 a

Cerebrospinal Fluid (CSF)

Problems • Meningitis- inflammation to the meninges. It is a serious threat because the bacteria or virus can spread to the CNS. • Encephalitis- is inflammation of the brain • Hydrocephalus- is water on the brain because a tumor (or something) is blocking drainage of the CSF. Treated with a shunt. • A spinal tap is done to test CSF

Nerve Pathways • • Reflex arc - only includes a few neurons Reflex Behavior - automatic, subconscious responses Knee-jerk reflex - maintains uprightedness Withdrawal reflex - avoidance of painful stimuli

• Functions of the Spinal Cord • carry sensory impulses to brain • carry motor impulses from brain to muscles & glands • Center for reflex activity • Reflex Arc (“no brainer”) STIMULUS SENSORY NEURON INTERNEURON (in spinal cord) MOTOR NEURON MOVEMENT

• all of this happens BEFORE signal is sent to the brain (“no brainer”)

Drugs and the Nervous System

Drugs that Affect Synapses and Neurotransmitters • • • Curare Strychnine Cocaine, morphine, alcohol, ether and chloroform Mescaline and LSD Ecstasy

Dangers of Ecstasy (MDMA) The neurotransmitter serotonin is vital in regulating many of our basic functions. Serotonin is, among other things, the feel good neurotransmitter and helps to regulate body temp. Our brain cells are constantly trying to bring some amount of serotonin back into the cells and out of the synapse using serotonin reuptake transporters. Ecstasy essentially takes these upkeep transporters and reverses their roles. This causes a massive flood of serotonin from the brain cells into the synapse. The most common cause of Ecstasy-related death is overheating (hyperthermia). MDMA interferes with the body's ability to regulate its own body temperature and to see other warning signs allowing the body to overheat without discomfort especially when dancing for hours in hot clubs.

LSD; lysergic acid diethylamide Actions/Effects: LSD alters the action of the neurotransmitters serotonin, norepinephrine, and dopamine, triggering extreme changes in brain function. Physical effects include increased body temperature, heart rate, and blood pressure. Psychological effects include perceptual and thought distortions, hallucinations, delusions, and rapid mood swings. Cocaine blocks reuptake of dopamine

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.

• Brain Disorders (some examples) • Parkinson’s Disease • deficiency of the neurotransmitter dopamine • Epilepsy • sudden burst of irregular electrical activity in brain – can lead to seizures, convulsions • Stroke • blood clot in brain – paralysis appears on side of body opposite to side of brain affected • Alzheimer’s Disease • part of cortex shrinks, neurons lost • results in dementia, memory loss, disorientation, loss of body function

Brain Injuries • Concussion- brain is slammed into the skull from an impact – Disoriented, nausea, see “stars” – May lose consciousness temporary – No permanent brain damage • Many concussions may lead to some damage of the brain • Contusion- Impact causes tissue damage – May cause a coma (temporary or long term) • Cerebrovascular Accident- Known as a stroke – Blood circulation to an area of the brain is blocked. – Some paralysis may occur – Sometimes functions are recovered

Brain Diseases • Schizophrenia – may result in some combination of hallucinations, delusions, and extremely disordered thinking and behavior – Risk factors – family history; exposure to viruses toxins, or malnutrition in the womb; increased immune system activation; older age of the father; taking mind altering drugs during teen years or young adulthood. – Treatment – medication and/or psychosocial therapy for life. Hospitalization may necessary.

• Depression Brain Diseases – Characterized by a persistent feeling of sadness and loss of interest – Causes – biological differences (makeup of the brain), brain chemistry, hormones, inherited traits – Treatments – medications and/or psychological therapy. Some people may need a hospital stay.