CHAPTER 3The Physiological Basis of Behavior

THE HUMAN NERVOUS SYSTEM

The Nervous system--is the complex

arrangement throughout the body of highly specialized cells, the neurons, which acts as a communication system, enabling the organism to respond to external and internal stimuli.

THE RECEIVING MECHANISM

Sense organs are sensitive nerve endings located in certain body parts. Its attributes are:A.) Sensitivity and Irritability: The Power to

react to stimulusB.) Conductivity: The power to conduct

nerve impulsesC.) Specificity: the attribute of reacting to

particular stimulusD.) Adaptability: the power to become used

to a particular stimulus.

TYPES OF SENSE ORGANS ACCORDING TO LOCATION:

A.)Extroceptors-found in the eyes, ears, nose, mouth, skin and are sensitive to external stimulus.

B.) Interoceptors- sense organs in the respiratory tract, digestive and genito-urinary tract.

C.) Proprieoceptors- are embeded in muscles, tendons and joints.

THE REACTING MECHANISM

A.Muscles of three kinds:

VoluntaryInvoluntaryCardiac or heart

Voluntary muscles: Muscles that move and

work when we want them to

Examples:Arm musclesLeg musclesNeck muscles

Voluntary Muscles

Involuntary muscles: Muscles that keep

working whether we think about them or not

Examples:StomachLungsMuscles in the heart

Involuntary Muscles

The Nervous system along with other chemicals in the body controls our involuntary muscles

Attached to bones by strong fibers called tendons

Muscles work in pairs to move the bones:

Example: biceps (relaxes and stretches) and triceps (contract and pull up the elbow)

Muscle is long, round, and cross striped

Skeletal Muscles

Cardiac Muscles Can be found only in the HEART

Muscle contracts and relaxes about 70 times a minute without stopping or getting tired

Muscle is strained both crossways and longways

Smooth Muscles Found in many different organs throughout the body

Examples: esophagus, stomach, and intestines

Muscle is slender and smooth without cross stripes.

Fun Facts

The main purpose of the Muscular System is for all the muscles to work together to create

movement!

Muscles make up almost 50% of our body weight

There are more than 600 muscles in the human body

MUSCLE CHARACTERISTICS Contractility-power of muscles to

shorten.

Tonicity- power to be in partial

contraction.

Extensibility-power to stretch

Elasticity-power to resume to its

original shape.

MUSCLE FUNCTIONS Functions 1.      To lend shape to the body as the

skeletal or voluntary muscles of the arms and legs do

2.      To propel food and waste product along the intestinal pathway as smooth muscles in the digestive tract do

3.      For movement as when the arms and legs move or when we move the mouth to form the sounds of speech

4.      To control the flow of blood, automatically opening and closing the blood vessels in response to body needs.

5.      To convert mechanical energy to mechanical work

DUCT GLANDS

B.Glands- are special secreting organs which pour their secretions either directly or indirectly to the bloodstream.

-have ducts or canals thru which they pour out their secretions. These includes lachrymal(tear) glands, sebaceous (sweat);salivary, gastric, sex and mammary glands.

ENDOCRINE GLANDS AND THEIR FUNCTIONS

PITUITARY GLAND Pituitary gland is located beneath hypothalamus

Hypothalamus

Neurosecretorycells of thehypothalamus

Axon

Anteriorpituitary

Posteriorpituitary

HORMONE ADH Oxytocin

TARGET Kidney tubules Mammary glands,uterine muscles

POSTERIOR PITUITARY

Stores & releases 2 hormones produced in hypothalamus:Antidiuretic hormone

(ADH/vasopressin) which promotes H20 conservation by kidneys

Oxytocin which stimulates contractions of uterus during parturition & contractions of mammary gland alveoli for milk-ejection reflex

ANTERIOR PITUITARY Secretes 6

trophic hormones that maintain size of targets High blood

levels cause target to hypertrophy Low levels

cause atrophy

ANTERIOR PITUITARY

Growth hormone (GH) promotes growth, protein synthesis, & movement of amino acids into cells

Thyroid stimulating hormone (TSH) stimulates thyroid to produce & secrete T4 & T3

Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete cortisol, aldosterone

ANTERIOR PITUITARY

Follicle stimulating hormone (FSH) stimulates growth of ovarian follicles & sperm production

Luteinizing hormone (LH) causes ovulation & secretion of testosterone in testes

Prolactin (PRL) stimulates milk production by mammary glands

ANTERIOR PITUITARY Other hormones/products of the

pituitary gland include: MSH - influences skin pigmentation in

some vertebrates and fat metabolism in mammals

Endorphins - inhibit the sensation of pain

ANTERIOR PITUITARY CONTINUED

Releasing & inhibiting hormones from hypothalamus are released from axon endings into capillary bed in median eminence Carried by

hypothalamo-hypophyseal portal system directly to another capillary bed in A. Pit. Diffuse into A. Pit. &

regulate secretion of its hormones

FEEDBACK CONTROL OF ANTERIOR PITUITARY

Target glands produce hormones that feedback to regulate the anterior pituitary and the hypothalamus

HIGHER BRAIN FUNCTION & ANTERIOR PITUITARY SECRETION

Hypothalamus receives input from higher brain centers that can affect Pituitary secretionE.g. psychological stress affects circadian rhythms,

menstrual cycle, & adrenal hormones

ADRENAL GLAND

ADRENAL GLANDS

Sit on top of kidneys

outer cortex inner medulla

ADRENAL GLANDS

Adrenal CortexMineralocorticoids

Aldosterone which stimulate kidneys to reabsorb Na+ and secrete K

GlucocorticoidsCortisol which inhibits glucose utilization &

stimulates gluconeogenesis. Inhibits inflammation, Supresses the immune system

ADRENAL MEDULLA

Secretes Epinephrine and Norepinephrine

"fight or flight" response causes:

Increased respiratory rate Increased HR & cardiac outputGeneral vasoconstriction which increases venous returnGlycogenolysis & lipolysisEtc, etc, etc

DISEASES ASSOCIATED WITH ADRENAL HORMONE LEVELS Cushing’s disease

Hyperadrenocorticism widened face with acne and flushing fatty deposits over back of neck stretch marks, easy bruising, hair overgrowth diabetes mellitus muscle loss and fatigue depression and psychosis moon-like face, 

Addison’s disease Hypoadrenocorticism

Hyperpigmentation, weight loss

THYROID GLAND

THYROID GLAND

Is located just below the larynx

Secretes T4 & T3 which set BMR & are needed for growth, development

Also secretes Calcitonin which lowers blood calcium levels

Hypothyroidism People with inadequate T4 & T3 levels

are hypothyroid Have low BMR, weight gain, lethargy,

cold intolerance Hyperthyroidism

Autoimmune disease where antibodies act like TSH & stimulate thyroid gland to grow & oversecrete = hyperthyroidism Characterized by exopthalmos, weight

loss, heat intolerance, irritability/anxiety, high BMR, rapid heart rate

DISEASES OF THE THYROID

GRAVES’ DISEASE Graves disease

is a form of hyperthyroidism that often presents with exopthalmos

PARATHYROID GLAND

PARATHYROID GLANDS

On the surface of thyroid gland

Secrete Parathyroid hormone (PTH) Elevates

blood Ca2+ levels

PARATHYROID HORMONE AND CALCITONIN: CONTROL OF BLOOD CALCIUM Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin play the major role in calcium (Ca2+) homeostasis in mammals

CalcitoninThyroid glandreleasescalcitonin.

StimulatesCa2+ depositionin bones

ReducesCa2+ uptakein kidneys

STIMULUS:Rising bloodCa2+ level

Blood Ca2+

level declinesto set point

Homeostasis:Blood Ca2+ level

(about 10 mg/100 mL)

Blood Ca2+

level risesto set point

STIMULUS:Falling bloodCa2+ level

StimulatesCa2+ releasefrom bones

Parathyroidgland

IncreasesCa2+ uptakein intestines

Activevitamin D

Stimulates Ca2+

uptake in kidneys

PTH

PANCREASISLETS OF

LANGERHANS

ISLETS OF LANGERHANS

Glugacon raises blood sugar (a cells) Insulin secreted

Which lowers blood sugar (b cells)

DIABETES MELLITUS Diabetes mellitus is the best-known endocrine

disorder Is caused by a deficiency of insulin or a

decreased response to insulin in target tissues Is marked by elevated blood glucose levels

Type I diabetes mellitus (insulin-dependent diabetes) Is an autoimmune disorder in which the

immune system destroys the beta cells of the pancreas

Type II diabetes mellitus (non-insulin-dependent diabetes) Is characterized either by a deficiency of

insulin or, more commonly, by reduced responsiveness of target cells due to some change in insulin receptors

Alphas secrete glucagon in response to low blood glucose during periods of fastingStimulates glycogenolysis & lipolysis Increases blood glucose

ISLETS OF LANGERHANS CONTINUED

GONADS: SEX & REPRODUCTIVE HORMONES

Gonads (testes & ovaries) secrete steroid hormones

The testes primarily synthesize androgens, the main one being testosterone Which stimulate the development and maintenance

of the male reproductive system Estrogens, the most important of which is

estradiol Are responsible for the maintenance of the female

reproductive system and the development of female secondary sex characteristics

Progestins, which include progesterone Are primarily involved in preparing and maintaining

the uterus in mammals

TESTOSTERONE Testosterone causes an increase in muscle and

bone mass and is often taken as a supplement to cause muscle growth

PLACENTA

PLACENTA Placenta

secretes estrogen, progesterone, hCG which maintains pregnancy,prevents eggs from ripening in the ovary, and numerous polypeptide hormones

THE CONNECTING MECHANISM-THE NERVOUS SYSTEM

A. The Neuron is the basic conducting unit of the nervous system. It has 3 principal parts: Dendrites-are specialized signal-receiving structures where the impulse (input)enters ; the cell body (central region) which integrates input and output and the axon where the output is discharged.

TYPES OF NEURONS According to speed According to basic function

a. Sensory Neurons (afferent fibers)-conduct impulses to the nervous system.

b. Association Neurons-central and connecting conduct impulses with in the nervous system.

c. Motor Neurons (efferent fibers)-conduct impulses away from the nervous system

 

THE HUMAN BRAIN

THE HUMAN BRAIN:

ANATOMY AND

FUNCTIONS

SKULL ANATOMYThe skull is a rounded layer of bone designed to protect the brain from penetrating injuries.

INTERIOR SKULL SURFACEThe base of the skull is rough, with many bony protuberances.

These ridges can result in injury to the temporal lobe of the brain during rapid acceleration.

Bony ridges

Injury from contact with skull

BLOOD VESSELS OF THE SKULL

The brain requires a rich blood supply, and the space between the skull and cerebrum contains many blood vessels.

These blood vessels can be ruptured during trauma, resulting in bleeding.

Groove for middle meningeal artery

ARTERIES OF THE BRAINThe human brain requires a constant supply of oxygen. A lack of oxygen of just a few minutes results in irreversible damage to the brain.

THE NEURON

Dendrites:Collects information from other neurons.

Cell Body

Axon:Transmits information to other neurons.

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THE MENINGES

The meninges are layers of tissue that separate the skull and the brain.

Skull

Dura mater

Arachnoid Layer

Pia Mater

Brain

EXTERNAL BRAIN STRUCTURES

THE CEREBRUMThe largest portion of the brain is the cerebrum. It consists of two hemispheres that are connected together at the corpus callosum.

The cerebrum is often divided into five lobes that are responsible for different brain functions.

Corpus callosum

THE CEREBRUM

The cerebrum’s surface—the neocortex—is convoluted into hundreds of folds.

The neocortex is where all the higher brain functions take place.

Neocortex

THE NEOCORTEXThe cerebral cortex is a thin layer of cells about 1.5 to 4 mm thick.

The cortex provides the connections and pathways for the highest cognitive functions, such as language and abstract thinking.

The cerebral cortex contains about 25 billion neurons, more than 62,000 miles of axons, and 300,000,000,000,000 synapses.

Neocortex layer

The thin layer of the neocortex is dense with neurons.

LOBES OF THE CEREBRUM

Parietal Lobe

Temporal Lobe

Frontal Lobe

Limbic Lobe

Occipital Lobe

FRONTAL LOBEThe frontal lobe is the area of the brain responsible for higher cognitive functions.

These include:

• Problem solving• Spontaneity• Memory• Language• Motivation• Judgment• Impulse control• Social and sexual behavior.

TEMPORAL LOBEThe temporal lobe plays a role in emotions, and is also responsible for smelling, tasting, perception, memory, understanding music, aggressiveness, and sexual behavior.

The temporal lobe also contains the language area of the brain.

PARIETAL LOBEThe parietal lobe plays a role in our sensations of touch, smell, and taste. It also processes sensory and spatial awareness, and is a key component in eye-hand co-ordination and arm movement.

The parietal lobe also contains a specialized area called Wernicke’s area that is responsible for matching written words with the sound of spoken speech.

OCCIPITAL LOBE

The occipital lobe is at the rear of the brain and controls vision and recognition.

LIMBIC LOBE

The limbic lobe is located deep in the brain, and makes up the limbic system.

THE LIMBIC SYSTEM

A. Cingulate gyrusB. FornixC. Anterior thalamic

nucleiD. HypothalamusE. Amygdaloid nucleusF. Hippocampus

The limbic system is the area of the brain that regulates emotion and memory. It directly connects the lower and higher brain functions.

CEREBELLUMThe cerebellum is connected to the brainstem, and is the center for body movement and balance.

THALAMUSThalamus means “inner room” in Greek, as it sits deep in the brain at the top of the brainstem.

The thalamus is called the gateway to the cerebral cortex, as nearly all sensory inputs pass through it to the higher levels of the brain.

HYPOTHALAMUSThe hypothalamus sits under the thalamus at the top of the brainstem. Although the hypothalamus is small, it controls many critical bodily functions:

• Controls autonomic nervous system

• Center for emotional response and behavior

• Regulates body temperature

• Regulates food intake

• Regulates water balance and thirst

• Controls sleep-wake cycles

• Controls endocrine system

The hypothalamus is shaded blue. The pituitary gland extends from the hypothalamus.

THE MEDULLA OBLONGATA

The medulla oblongata merges seamlessly with the spinal cord and creates the base of the brainstem.

The medulla is primarily a control center for vital involuntary reflexes such as swallowing, vomiting, sneezing, coughing, and regulation of cardiovascular and respiratory activity.

The medulla is also the origin of many cranial nerves.

THE PONSThe pons is the rounded brainstem region between the midbrain and the medulla oblongata. In fact, pons means “bridge” in Latin.

The main function of the pons is to connect the cerebellum to the rest of the brain and to modify the respiratory output of the medulla.

The pons is the origin of several cranial nerves.

THE VENTRICLES

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The ventricles are a complex series of spaces and tunnels through the center of the brain.

The ventricles secrete cerebrospinal fluid, which suspends the brain in the skull.

The ventricles also provide a route for chemical messengers that are widely distributed through the central nervous system.

CEREBROSPINAL FLUIDCerebrospinal fluid is a colorless liquid that bathes the brain and spine.

It is formed within the ventricles of the brain, and it circulates throughout the central nervous system.

Cerebrospinal fluid fills the ventricles and meninges, allowing the brain to “float” within the skull.

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THE BRAINSTEMThe brainstem is the most primitive part of the brain and controls the basic functions of life: breathing, heart rate, swallowing, reflexes to sight or sound, sweating, blood pressure, sleep, and balance.

The brainstem can be divided into three major sections.

Detailed brainstem anatomy.

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BRAINSTEM COMPONENTS

Front

RearMore Information:MedullaThalamusPons

BRAINSTEM DIVISIONS

Midbrain

Pons

Medulla Oblongata

THE CRANIAL NERVESI. Olfactory nerveII. Optic nerveIII. Oculomotor nerveIV. Trochlear nerveV. Trigeminal nerveVI. Abducens nerveVII. Facial nerveVIII. Vestibulocochlear nerveIX. Glossopharyngeal nerveX. Vagus nerveXI. Accessory nerveXII. Hypoglossal nerve

BRAIN FUNCTIONS• Vision• Taste• Cognition• Emotion• Speech• Language• Hearing• Motor Cortex• Sensory Cortex• Autonomic Functions

VISIONThe visual cortex resides in the occipital lobe of the brain.

Sensory impulses travel from the eyes via the optic nerve to the visual cortex.

Damage to the visual cortex can result in blindness.

TASTEThe gustatory complex (green circle) is the part of the sensory cortex (purple area) that is responsible for taste.

COGNITIONThe prefrontal cortex is involved with intellect, complex learning, and personality.

Injuries to the front lobe can cause mental and personality changes.

EMOTIONEmotions are an extremely complex brain function. The emotional core of the brain is the limbic system. This is where senses and awareness are first processed in the brain.

Mood and personality are mediated through the prefrontal cortex. This part of the brain is the center of higher cognitive and emotional functions.

Prefrontal cortex

Limbic system

SPEECHBroca’s area is where we formulate speech and the area of the brain that sends motor instructions to the motor cortex.

Injury to Broca’s area can cause difficulty in speaking. The individual may know what words he or she wishes to speak, but will be unable to do so.

Broca’s Area

LANGUAGEWernicke’s area is a specialized portion of the parietal lobe that recognizes and understands written and spoken language.

Wernicke’s area surrounds the auditory association area.

Damage to this part of the brain can result in someone hearing speech, but not understanding it. Wernicke’s Area

Auditory Association Area

HEARINGThere are two auditory areas of the brain:

• The primary auditory area (brown circle) is what detects sounds that are transmitted from the ear. It is located in the sensory cortex.

• The auditory association area (purple circle) is the part of the brain that is used to recognize the sounds as speech, music, or noise.

MOTOR CORTEXThe motor portion of the cerebrum is illustrated here. The light red area is the premotor cortex, which is responsible for repetitive motions of learned motor skills. The dark red area is the primary motor area, and is responsible for control of skeletal muscles.

Different areas of the brain are associated with different parts of the body.

Injury to the motor cortex can result in motor disturbance in the associated body part.

SENSORY CORTEXThe sensory portion of the cerebrum is illustrated here.

Different areas of the brain are associated with different parts of the body, as can be seen below.

Injury to the sensory cortex can result in sensory disturbance in the associated body part.

AUTONOMIC FUNCTIONS

The brainstem controls the basic functions of life. Damage to these areas of the brain are usually fatal:

•The pons plays a critical role in respiration.

•The medulla oblongata is responsible for respiration and cardiovascular functions.

Pons

Medulla Oblongata