IFAWhat parts of the body is the

Central Nervous System comprised of?

Anatomy of the Central Nervous System

• New technology and advances in science have led to a better understanding of the relationship of the brain, biological basis of behavior, and mental disorders

Student Objective

• I can identify parts and functions of the Central Nervous System (CNS)

Cells of the Nervous System

• The cells are known as Neurons.– Neurons- the basic building block of the nervous

system that specialize in transmitting information throughout the body

• Unusual shape• Nerve fibers extend from body cell (soma)

– Dendrites- branched fibers that receive neural impulses– Axons- transmits neural messages from cell body towards

another neuron

Two principal divisions of the nervous system

• Central Nervous System (CNS)• Peripheral Nervous System (PNS)

Central Nervous System (CNS)

– Brain and spinal cord• Serve as control center for entire organism• Integrated incoming information and determines

appropriate responses

Peripheral Nervous System

– Made up of nerves outside of CNS• Acts a communication lines to and from CNS

– Made up of sense organs- eyes, ears, taste buds, olfactory receptors, and touch receptors

Mental Health Link•Understanding of

mental disorders most often involves

understanding the structure and function

of the CNS

IFA

The picture above is a representation of what system of the body?

Cerebral Cortex

• Thin outer surface of the forbrain• Largely made up of cell bodies which are gray• Most highly evolved portion of the brain

Cerebrum

• Forebrain– The largest most anterior part of the human brain– Control motor activities and interprets sensations

Lobes of the Cerebrum

• Frontal • Temporal • Parietal • Occipital

Frontal Lobe• Motor cortex-control skeletal muscles• Broca’s speech area-formation of words• Responsible for personality

– Damage can cause a change in personality

Temporal Lobe• Auditory area• Language memory and speech capacity• Damage can result in aphasia

– Aphasia: partial or total inability to produce and understand speech as a a result of brain damage cause by injury or disease

Parietal Lobe

• Sensory association area- impulses from skin such as pain and temperature are interpreted

• Area for estimation of distances, sizes, and shapes

Occipital Lobe

• Primary visual area• Trauma can result in blindness• Lesions can cause visual hallucinations

IFA

• The picture below is of the brain...what lobe of the brain is the area located and what is the

area called?

Pituitary Gland

• Master Gland• Its secretions control timing and amount of

hormone secretions by other endocrine glands– Thyroid– Adrenal Glands– Ovaries– Testes

Cerebellum• Responsible for coordination of movements

– Makes movements smooth– Helps maintain muscle tone– Helps maintain equilibrium

Pons

• Forms a bulge on anterior surface of brain stem

• The link (bridge) that connects various parts of the brain

Pons Visual

Medulla Oblongata• Most anterior portion of the brain stem• Vital centers of medulla

– Cardiac center: control heart rate– Vasomotor center: helps regulate blood pressure– Respiratory center: initiate and regulate breathing– Center for reflex actions: (vomiting, sneezzing,

coughing, and swallowing)

IFA• List the four centers of the Medulla Oblongata.

Provide a description of each center.•

The Brain Part IINeurophysiology-Chemical Events at the

Synapse• Each structure and each chemical produced and used by the

brain has a specific function. Disease may cause alteration in the function of the brain. An understanding of the chemical events occurring at the synapse is fundamental to biological psychology.

• Objective:– Student will identify the neurotransmitters

and name disorders that can result when there is neurotransmitter dysfunction.

Neurons

• Nerve cells that make up the brain and peripheral nerves– Communicate with each other at the synapses

• Synapse is a functional (not physical) contact between to neurons

• About 100 billion neurons in human brain– Each neuron has about 10,00 synaptic contacts

with other neurons.

Parts of a Neuron• Cell body or soma

– Contains the nucleus of the cell (DNA)– Soma constitutes “receiving” surface of the

neuron – If the soma is damages, a neuron will not recover

Parts of a Neuron

• Dendrite– Multiple branches come off the coma– Branches receive nerve impulses from other neurons– Dendrite branching is influences by environment during

development, both pre and post natal• The more branches, the more receiving sites for a neuron• Dendrites are few and sparsely branched in certain conditions

such as Downs Syndrome and Fetal Alcohol Syndrome• Lab animals who have received stimulations as infants shoe more

dendritic branching

Axon

• Single fiber that is thicker and longer than dendrites• Axon may have many branches at it end• Axons may be very short (1 micron) to very long (1

meter) depending on their destinations in the nervous system

• Damaged neurons may show sprouting of new terminals to fill in spaces vacated by damaged axons

• Mature neurons may not have an axon• Axon terminals in brain may be represented by these

organizations

Myelin Sheath

• The lipid and protein sheath surrounding the axon• Purpose to insulate neuron• The more heavily mylinated the neuron the faster the

electrical pulse can travel down the axon to other neurons

• Multiple Sclerosis (MS) condition where the myelin of the brain and spinal cord degenerate– Nerve impulses unable to travel smoothly and efficiently

The Synapse

• A dynamic region between neurons consisting of:– Axon terminal (carries electrical impulses away

from soma)– Synaptic cleft (a space between terminal axon and

receiving neuron)– Dendrite (or adjacent neuron body)

• REMEMBER that both SOMA and DENDRITES constitutes the RECEIVING surface of a neuron

– Synapse Graphic

Neurotransmitters: The Chemical Messengers

• Chemicals (hormones) that are made in soma and stored in small synaptic vesicles (“packages”) at the tip of the axon

• As electrical pulses travel from soma to axon, neurotransmitters are released into synapse

• Neurotransmitters stick to receptors proteins in neighboring dendrite and trigger nerve impulse that travel down dendrite, across soma, down axon, etc.

• Our behavior is consequence of millions of cells “talking” to each other via these electrochemical processes

Neurotransmitter Graphic

Inactivation of Neurotransmitters

• The action of neurotransmitters can be stopped by four different mechanisms: – Diffusion: the neurotransmitter drifts away, out of the

synaptic cleft where it can no longer act on a receptor. – Enzymatic degradation (deactivation): a specific enzyme

changes the structure of the neurotransmitter so it is not recognized by the receptor. For example, acetylcholinesterase is the enzyme that breaks acetylcholine into choline and acetate.

Neurotransmitter Graphic

Inactivation of Neurotransmitters

– Glial cells: astrocytes remove neurotransmitters from the synaptic cleft

– Reuptake: the whole neurotransmitter molecule is taken back into the axon terminal that released it. This is a common way the action of norepinephrine, dopamine and serotonin is stopped...these neurotransmitters are removed from the synaptic cleft so they cannot bind to receptors

Some of the Well Known Neurotransmitters

• Acetylcholine (Ach)• Dopamine (DA)• Serotonin and Norepinephrine• Gamma Aminobutyric Acid (GABA)\• Endorphines (“endegenous morphine)

Acetylcholine (Ach)

• Contributes to movement, learning, memory processes and REM sleep

• Only transmitter between motor neurons and voluntary muscles

• EXCESS: muscle paralysis or convulsions, sometimes death

• DEFICIT: memory impairment (Alzheimer’s disease)

Dopamine (DA)

• Used by neurons control voluntary movement• Also used by neurons that are important for

learning, attention, thought, and emotion• EXCESS: irrational thought, delusion, and/or

hallucinations (Schizophrenia)• DEFICIT: tremors, muscular rigidity

(Parkinson’s disease)•

Serotonin and Norepinephrine

• Serotonin play prominent role in regulation of mood, sleep impulsivity, aggression, and appetite.

• Norepinephrine plays role in eating, sleep, and mood• Lower level of activity in serotonin and

norephinephrine is related to depression• DEFICIT serotonin: may lead to increased aggressive

behavior and suicide• Some antidepressants drugs act to block reuptake of

serotonin or norepinephrine

IFA

• What is the synapse composed of?

Gamma-Aminobutyric Acid (GABA)

– i. Appears to have inhibitory effects at synapses

– ii. contributes to regulation of anxiety

– iii. lower levels of activity related to anxiety

– iv. antianxiety drugs (tranquilizers such as Valium) facilitate GABA synapses and thereby reduce anxiety

– v. abnormality in GABA neurons may cause epilepsy

Endorphins (“endogenous morphine”)

– opiate-like substances produced in the body

– provide relief from pain and produce feelings of pleasure and well-being

– drugs such as opium, morphine, and heroin bind with receptors for endorphins

– endorphins may explain “runners-high” experienced by long-distance runners

Imaging of the Brain

• I. Key Terms

– A. neuro – root for brain and/or nervous system

– B. imaging – procedure which records a picture or “image” of a body part

– C. tome – Greek word that means “slice” sometimes referred to as a “cut” of body tissue

• a. in neuroimaging, tome refers to cross-sectional images that demonstrate multiple “slices” of human anatomy

• b. orientation of cross-sectional images depends on the body plane along which the image was recorded

• D. –graphy – suffix that means a process of recording (an image)

Imaging of the Brain

• II. Body Planes – imaginary planes that pass through the body dividing it into sections; these planes provide the orientation for cross-sectional images in neuroimaging

– A. transverse plane – imaginary plane that cuts across the body or body part and divides body or its part into upper and lower parts.

– B. sagittal plane – imaginary plane that cuts the body into right and left sections

• a. midsagittal plane (also called median plane) – imaginary plane that cuts body into equal right and left halves

– C. coronal plane (also called frontal plane) – imaginary plane that divides the body or its parts into front and back sections

Traditional Types of Neuroimaging

• A. Skull Radiograph (takes about 5 to 10 minutes)

– a. description: one-dimensional x-ray of skull

• i. generally requires at least three separate x-ray images from different angles to better determine tissue abnormality

– 1. image from the front (AP x-ray)

– 2. image from the side (lateral x-ray)

– 3. image with head turned 45 degrees (oblique x-ray)

Skull Radiograph: Advantages/Disadvantages

– b. advantages:

• i. relative inexpensive

• ii. fast

• iii. demonstrates bony structures and fractures

– c. disadvantages:

• i. radiographic projections are one-dimensional and cannot accurately demonstrate depth and location of lesion

• ii. does not image soft-tissue as well as bone

Lateral Projection

Traditional Types of Neuroimaging

• Cerebral Angiography (takes about 60+ minutes)

– a. description: traditional skull radiographs taken during injection of radiopaque contrast medium (“dye”) into the carotid arteries

• i. visualization of blood flow via the carotid arteries to the brain

• ii. helps diagnose patency of vessels, intracranial aneurysms, & tumor masses, which are shown by displacement of normal vessels

Cerebral Angiography: Disadvantages/Advantages

– disadvantage:

• i. uses bolus of iodine-based dye for visualization of vessels

– 1. may produce allergic reaction in some patients

– 2. could dislodge vascular plaque and cause a stroke

Cerebral Angiography

QUIZ

Neuroimaging of the Late 20th-Century

• Computerized Axial Tomography –CAT scan (also called CT Scan) (takes 10 to 30 minutes)

• c. description: involves passing a narrow beam of traditional x-rays through brain of a person lying in a large, donut-shaped x-ray machine called a scanner; provides transverse slices of the head

– i. beam of x-rays sent out by x-ray tube that rotates around patient’s head

– ii. whole series of x-rays are taken at every angle around the head and then combined in a computer to reconstruct an image of transaxial slice of the head

Computerized Axial Tomography –CAT scan: Disadvantages/Advantages

• advantages:

– i. imaging method of choice for examining skull fractures

– ii. one of the least expensive modalities (other than skull x-rays)

• e. disadvantages:

– i. difficult to see brain tissue, therefore, does not serve as specific test for mental disorders

– ii. sometimes dye (called contrast media) must be given as a shot in a vein to help get a clear picture; some people are allergic to this dye

– iii. underestimation of brain atrophy

– iv. inability to image in sagittal and coronal planes

– v. one CT scan delivers radiation equivalent to many traditional x-rays (this limits the total number of scans that can be performed safely within an individual)

CT scan images

Magnetic Resonance Imaging (MRI) (takes 30 to 90 minutes)

– a. description: uses magnetic fields and radio waves to obtain a mathematically reconstructed image

– b. how it works:

• i. certain nuclei in the body are magnetic (those having odd numbers of protons or neutrons)

• ii. when under the influence of a magnetic field, those nuclei oscillate and reemit radio waves that are picked up by MRI receiver and sent to a computer

• iii. radio waves are then reconstructed by the computer into an image of the brain

Magnetic Resonance Imaging (MRI)• advantages:

– i. allows for clear distinctions between cerebrospinal fluid and gray and white matter

– ii. can show minor brain injuries and close-up pictures of base of brain

– iii. intrinsically 3-dimensional, acquiring multiple images in any plane (transverse, sagittal, and/or coronal)

– iv. does not involve radiation

• d. disadvantages:

– i. noisy (patient ‘s usually given pair of headphones or earplugs

– ii. must lie flat on back inside small “tunnel” of scanner (makes many patients feel claustrophobic)

– iii. must remove all metal objects & jewelry

– iv. tests often take a long time (30 to 90 minutes)

– v. more expensive than CT scans

Positron Emission Tomography (PET) & Single Photon Emission Computed

Tomography (SPECT)

• a. description: both are noninvasive imaging techniques that scan radioactive material that was injected into a peripheral vessel of the patient

• b. advantages:

– i. unlike conventional radiography which demonstrates the structure (anatomy) of organs, PET & SPECT are able to measure particular aspects of human physiology (which is determined from scanner’s measurement of neurotransmitter radioactivity)

– ii. unlike other studies that use toxic contrast medium (“dye”) to visualize vessels, the small amount of radioactive pharmaceuticals used in PET & SPECT studies are similar to body’s own biochemical constituents

• c. note that SPECT studies are much more cost effective than PET exams

Clinical Applications of PET & SPECT

• Alzheimer’s Disease and Dementia

– a. SPECT studies have shown decreased size of hippocampus and metabolic disturbances in early stages of Alzheimer’s

• B. Mood Disorders

– a. SPECT & PET studies consistently found reduced global cerebral blood flow—particularly in unipolar patients

• i. decreased activity in prefrontal cortex seen in depressed patients

• C. Schizophrenia

– a. PET studies demonstrate a decrease of activity in frontal lobe and an increase of activity in the subcortical regions

Clinical Applications of PET & SPECT

• Anxiety Disorders

– a. panic attacks: PET scans demonstrate area of hyperactivity in right parahippocampal gyrus

– b. general anxiety disorder: PET studies show increase in glucose metabolism in thalamus

– c. obsessive-compulsive disorder: SPECT studies show increased metabolic activity in frontal lobes and basal ganglia

• E. Personality and Eating Disorders

– a. bulimia: PET images show cortical asymmetry in metabolic rate for glucose

– b. schizotypal personality disorder: abnormalities found in frontal and temporal