Biology 3201 Emily V. Walsh

Unit 1: Maintaining Dynamic

Equilibrium

PART A: The Nervous System

1. Nervous System: The network of nerve cells and fibres that transmits nerve impulses between parts of the body.

Nerve Net: a simple nervous system found in simple organisms.

Ganglia: a clump of nerve cells that developed in slightly more complex organisms (like a primitive brain).

Central and Peripheral Nervous Systems: Vocab #8 & 9.

Neurons: nerve cells of the most complex organisms. Neurons make up the brain. There are different types of neurons (Vocab #2-4). A neuron consists of:

o Cell Body: contains the nucleus and all the usual organelles of the cytoplasm. o Dendrites: short extensions of the cell body that receives electrical stimuli. o Axon: long, slender extension that transmits impulses to be sent throughout the body. o Schwann’s Cells: cells that attach to the axon and develop an insulating layer called the

myelin sheath. These cells are spaced out over the axon, separated by nodes of Ranvier. This allows impulses so jump through the axon faster from node to node by conduction – this kind of conduction is called salutatory conduction.

2. Sensory Neurons: receive impulses from the environment (ex. a touch on skin) and sends messages back through the body. They are stimulated by the sense of touch. 3. Motor (Effector) Neurons: receive impulses from sensory neurons and produce a response in a muscle or a gland (ex. feel a bee sting in sensory neuron, motor neuron makes your muscles contract to pull away). 4. Interneurons: neurons that link motor neurons to sensory neurons. 5. Resting Potential: when the inside of the plasma membrane of the axon has a negative charge, while there is a positive charge outside. This is caused by a sodium-

potassium pump which is working backwards from most other sodium-potassium pumps. They are transporting sodium ions out, and potassium ions in. Many potassium ions can leave through open channels, while sodium cannot. Channels that would allow the movement of sodium are closed during resting, and opened during action potential. This is why neurons can carry electrical impulses as those impulses are attracted to their negative charge. 6. Action Potential: the build up of a charge in the cell body of a neuron that sends an impulse down an axon. Channels that allow the flow of ions over the membrane (other than potassium) open up, allowing sodium to pass inside the cell, making the inside more positive and the outside more negative (depolarization). This moment only lasts a split second and causes movement of cells. After this moment, the sodium channel closes, the potassium reopens and the original state of resting potential returns (re-polarization); this time period is called the refractory period. Because the action of one sodium channel reacts the next, which reacts the next, etc., an impulse wave is formed that carries impulses through axons on the other neurons.

Impulse Wave moving to the right.

Think of the salty banana

analogy!

When a neuron is at resting

potential, it is a salty banana –

sodium outside and

potassium inside!

7. Synapse: a junction between the axon bulb (end of an axon that contains many vesicles with neurotransmitters) and the dendrite of another neuron. The narrow gap between these two is called the synaptic cleft.

When the action potential reaches the axon bulb, channels open that allow the passage of calcium ions into the axon.

The calcium ions bind to vesicles containing neurotransmitters (chemicals that carry information across the synaptic cleft), causing them to fuse with the axons plasma membrane, releasing the neurotransmitters across the synaptic cleft.

These transmitters bind to receptor proteins to open channels that allow the passage of ions into the receiving cell. This changes the charge of the receiving cell, causing an action potential that will then travel down its axon.

The type of neurotransmitter used in this reaction is called acetylcholine. They are broken down by the enzyme acetylcholinesterase after the reaction.

Multiple Synapses: when a neuron receives an excitatory action potential (impulses to create movement and more action potentials) and an inhibitory action potential (impulse to cease movement and stop action potentials) at the same time, they cancel each other out and nothing happens.

GABA & Norepinephrine: other types of neurotransmitters that work in the central areas of the human body.

8. Central Nervous System: neurons of the brain and spinal chord.

Spinal Cord: The cylindrical bundle of nerve fibres and associated tissue that is enclosed in the

spine and connects nearly all parts of the body to the brain, with which it forms the central nervous system.

Brain: An organ of soft nervous tissue contained in the skull of vertebrates, functioning as the coordinating center of sensation and intellectual and nervous activity. The brain has the following major divisions:

o Cerebrum: largest part of the human brain that controls thoughts, coordination and voluntary activities. The cerebrum is made up of 4 lobes:

Frontal Lobe: the front of the brain Temporal Lobe: below the frontal lobe. Occipital Lobe: lower back of the brain. Parietal Lobe: upper back of the brain.

o Cerebellum: coordinates muscle activity, balance and refinement of movement. o Brain Stem: the part of the brain continuous with the spinal cord. Consists of the

medulla oblongata, Pons, midbrain and parts of the hypothalamus. Hypothalamus: regulates homeostasis and hormones (pituitary gland, growth,

sexual, etc). Medulla (oblongata): controls involuntary actions needed for survival

(breathing, heart, etc.). Pons: Controls part of the respiratory system and attaches parts of the brain

together. Midbrain: controls visual and auditory reflexes (blinking, jumping at loud noises,

etc.).

Thalamus: controls sensory relay that connects impulses between the spinal cord and cerebrum.

9. Peripheral Nervous System: The nervous system outside the brain and spinal cord. This system can be

broken down into the following:

Somatic Nervous System: the part that controls voluntary activities, such as the movement of

your eyes to read this sentence.

Autonomic Nervous System: the part that controls involuntary activities, just as your heart

beating right now. In some cases, this can overlap with the somatic nervous system. For

example, you can control your breathing if you think about it (somatic) even though you will -

involuntary when you do not think about it (autonomic). The autonomic system can be broken

down even further into the following:

o Sympathetic Nervous System: system with the purpose to mobilize the body's

resources under stress; to induce the fight-or-flight response.

o Enteric Nervous System: a subdivision of the peripheral nervous system (PNS), that

directly controls the gastrointestinal system.

o Parasympathetic Nervous System: opposes physiological effects of the sympathetic

nervous system. It returns the body to homeostasis (stimulates digestive secretions;

slows the heart; constricts the pupils; dilates blood vessels).

10. Sensory Systems: systems that input information to the nervous system in the form of touch, vision,

hearing, smell and taste. Touch (feeling of pain, temperature, pressure, etc.) is a somatic senses,

whereas the others are all defined as special senses.

Hearing: the ability to sense sound, using the ears in humans. Ears are structures in the human

head that detect sound and detect orientation and gravity. The ear has the following structures:

o Pinna: the external portion of the human ear. The ridges are important in determining

the direction sound comes from.

o Auditory Canal: passage that allows the travel of sound into the mechanisms of the ear.

o Tympanic Membrane (Eardrum): membrane of the middle ear (at the end of the

auditory canal) that vibrates in response to sound waves. This vibration activates the

hammer.

o Malleus (Hammer): small bone in the middle ear that transmits vibrations of the

eardrum to the incus.

o Incus (Anvil): small bone in the middle ear, transmitting vibrations between the malleus

and stapes.

o Stirrup (stapes): small bone in the middle ear, transmitting vibrations from the incus to

the inner ear.

o Oval (Vestibular) Window: membrane-covered opening which leads from the middle

ear to the vestibule of the inner ear.

o Vestibule: bony cavity of the inner ear.

o Vestibular Nerve: nerve attached to the semicircular canals that brings positional

information to the brain.

o Semicircular Canals: fluid-filled bony channels in the inner ear. They are situated at right

angles to each other and provide information about orientation to the brain to help

maintain balance.

o Round (Cochlear) Window: opening in the cochlea that allows pressure from sound

waves to be released.

o Auditory (Eustachian) Tube: tube that links the pharynx to the middle ear.

o Cochlea: spiral cavity of the inner ear which produces nerve impulses in response to

sound vibrations.

o Cochlear Nerve: a nerve in the head that carries signals from the cochlea of the inner

ear to the brain.

Sight: the ability to sense and interpret light, using the eyes. The human eyes are a pair of

globular organs in the head through which people see. The eye consists of:

o Cornea: transparent layer forming the front of the eye.

o Iris: flat, colored, ring-shaped membrane behind the cornea of the eye, with an

adjustable circular opening (pupil) in the center.

o Pupil: dark circular opening in the center of the iris of the eye, varying in size to regulate

the amount of light reaching the retina.

o Anterior Compartment: open space between the lens and the iris.

o Ciliary Body: part of the eye that connects the iris to the choroid.

o Lens: transparent substance with curved sides for concentrating or dispersing light rays.

o Posterior Compartment: large open space in the middle and back of the eye.

o Sclera: white outer layer of the eyeball.

o Choroid: pigmented vascular layer of the eyeball between the retina and the sclera.

o Retina: layer at the back of the eyeball containing cells that are sensitive to light and

that trigger nerve impulses that pass via the optic nerve to the brain, where a visual

image is formed.

o Retinal Blood Vessels: blood vessels at the back of the eye.

o Fovea Centralis: area consisting of a small depression in the retina containing cones and

where vision is most acute. These cones are sensitive to different colors of light (red,

blue or green), which is controlled by opsins, chemicals that bind cones to the fovea

centralis. Opsins are coded on the X chromosome.

o Optic Nerve: nerve that carries impulses from the retina to the brain.

Light Fovea Centralis

Sensory Disorders: there are multiple disorders of the eye and ear.

o Color Blindness: when opsins are not coded correctly off the X chromosome, the cones

can no longer receive the correct colors.

o Near-sightedness [Myopia]: a refractive defect of the eye in which light produces an

image in front of the retina, rather than on the retina. This can be corrected with a

concave lens.

o Far-sightedness [Hyperopia]: a refractive defect of the eye in which light produces an

image behind the retina, rather than on the retina. This can be corrected with a convex

lens.

o Astigmatism: defect in the eye or in a lens caused by a deviation from spherical

curvature, which results in distorted images, as light rays are prevented from meeting at

a common focus. This can be corrected with a specialized lens for the individual.

o Glaucoma: condition of increased pressure within the eyeball, causing gradual loss of

sight.

o Cataracts: condition in which the lens of the eye becomes progressively opaque,

resulting in blurred vision and potentially blindness (inability to see) if not treated.

o Deafness: the inability or difficulty to hear. There are two types of deafness, and they

can be treated by hearing aids, or dealt with using sign language:

Nerve Deafness: hearing loss due to damage to auditory receptors or auditory

pathways of the central nervous system.

Conduction Deadness: hearing loss usually caused by blockage of the auditory

canal, damage to the eardrum, or deterioration of the middle ear.

Hearing Aids: small device that fits in or on the ear, worn by a partially deaf

person to amplify sound.

Conventional: basic hearing aid that uses analog circuitry. This circuitry

processes sound as a voltage. These aids tend to be relatively

unsophisticated and usually require the user to adjust the volume as

needed.

Digital Aids: most advanced hearing aid technology available to date.

Digital hearing aids convert sound into numeric code and adjust

automatically in order to detect and amplify speech while turning down

background noise.

Programmable: an aid that is a hybrid of both conventional and digital

aids.

Sign Language: system of communication using visual gestures and signs, as

used by deaf people.

o Fluid Build Up: many children get chronic middle ear infections due to fluid build up

behind the eardrum. This may go away with age, or they may have to implant

semicircular tubes through surgery.

11. MRI [Magnetic Resonance Imaging]: a non-invasive medical imaging technique that uses magnets;

used in radiology to visualize detailed internal structure and limited function of the body.

12. CT (CAT) Scan [Computed tomography]: method of body imaging where the x-ray beam rotates

around you. Small detectors measure the amount of x-rays that make it through the body area of

interest.

13. PET [Positron emission t omography]: a computerized radiographic technique to examine the

metabolic activity in various tissues (especially in the brain).

14. EEG [Electroencephalogram]: graphical record of electrical activity of the brain.

15. Fight or Flight Response: the way the body responds to a sudden unexpected stressful stimulus such

as a physical threat or emergency situation.

PART B: The Endocrine System

1. Endocrine System: system of glands that produce endocrine secretions that help to control bodily metabolic activity. 2. Hormones: chemical messengers that can be produced in one region of the body to act on target cells in another part of the body.

Thyroxin:

o Gland: Anterior Pituitary

o Effect: Thyroxin increases basal metabolic rate and oxygen consumption, especially in

the heart, liver, skeletal muscle, and kidney.

Calcitonin:

o Gland: Thyroid

o Effect: Calcitonin regulates calcium levels in the blood.

Insulin:

o Gland: Pancreas

o Effect: Referred to as the hormone of abundance because it forces our body to store

nutrients. It increases the intake of fatty acid, and amino acids by adipose and muscle

cells and activates enzyme systems that convert glucose to glycogen in liver and muscle

cells. Insulin also stimulates protein synthesis and tissue growth throughout the body.

Glucagon:

o Gland: Pancreas

o Effect: Triggers the cellular release of

glucose, fatty acids, and amino acids

into the bloodstream.

Melatonin:

o Gland: Pineal

o Effect: Melatonin production is highest

during night time hours and diminishes

during the day. Melatonin is the gland

that makes you sleepy.

Thymosin:

o Gland: Thymus

o Effect: Thymosin stimulates the

production and maturation of

lymphocytes into T cells.

Aldosterone:

o Gland: Adrenal

o Effect: Two primary functions are

osmoregulation (the process of regulating the amounts of water and mineral salts in the

blood) and regulation of blood pressure.

Cortisol:

o Gland: Adrenal

o Effect: Cortisol secretion causes a dramatic rise in the process of gluconeogenesis, the

synthesis of carbohydrates from amino acids and other substances in the liver. It

decreases build-up of fluids and any other inflammation, and suppresses the production

of T cells.

Adrenaline and Noradrenaline:

o Gland: Adrenal Medulla

o Effect: Increases heart rate and blood pressure, causing widening of the blood vessels in

the heart and respiratory system.

Oxytocin:

o Gland: Posterior Pituitary

o Effect: Oxytocin plays an important role during and after childbirth by triggering muscle

contractions during birth, and releasing milk from the breasts. It also stimulates

contractions to be more forceful, and this effect creates a positive feedback loop as

seen on page 431.

Anti-diuretic Hormone (ADH):

o Gland: produced by the hypothalamus and released by the posterior pituitary

o Effect: ADH regulates sodium levels in the bloodstream. It is also released in response

to decreased blood pressure.

Thyroid Stimulation Hormone (TSH):

o Gland: Thyroid

o Effect: TSH stimulates an increase in iodine uptake from the blood and the synthesis and

secretion of the thyroxin hormone.

Adrenocortocotropin (ACTH):

o Gland: Anterior Pituitary

o Effect: ACTH regulates the production of cortisol and aldosterone.

Prolactin:

o Gland: Anterior Pituitary

o Effect: Prolactin stimulates the development of mammary gland tissue and milk

production.

Human Growth Hormone (HGH):

o Gland: Anterior Pituitary

o Effect: HGH spurs body growth by increasing absorption of calcium, increasing cell

division and development, and stimulation protein synthesis and lipid metabolism. HGH

acts as a tropic hormone by triggering the production of growth factors in the liver and

other tissues.

Gonadotropins:

o Gland: Ovaries and Testes

o Effect: The effect is different varying on gender. For males, the testes produce sperm

and testosterone. For females, the ovaries produce eggs and estrogen.

Estrogen:

o Gland: Ovaries

o Effect: steroid hormones that promote the development and maintenance of female

characteristics of the body.

Progesterone:

o Gland: Ovaries

o Effect: steroid hormone that stimulates the uterus to prepare for pregnancy.

Luteinizing Hormone (LH):

o Gland: Anterior Pituitary

o Effect: stimulates ovulation in females and the synthesis of male hormones in males.

Follicle Stimulating Hormone (FSH):

o Gland: Anterior Pituitary

o Effect: stimulates growth of follicles in female mammals, and activates the cells in male

mammals that form sperm.

Testosterone:

o Gland: Testes

o Effect: steroid hormone that stimulates development of male secondary sexual

characteristics.

3. Diseases of the Endocrine System:

Diabetes: disorder of the metabolism causing excessive thirst and the production of large

amounts of urine.

o Type 1:

Gland: Pancreas

Nature of imbalance: The body’s own immune system mounts an attack on the

parts of the body. Ex: An attack on the pancreas causes elevated blood sugar,

and the body therefore would not make enough insulin.

Symptoms and treatment: Symptoms include blurred vision, decreased mental

sharpness, extreme thirst and hunger, fatigue, frequent urination, weight loss,

slow healing wounds, fruity smelling breath, pain in abdomen, and nausea.

Treatment includes proper nutrition, exercise, and an insulin pump/ injections.

o Type 2:

Gland: Pancreas;

Nature of imbalance: Body produces insulin either insufficient quantities or the

body can’t recognize/ respond to it.

Symptoms and treatment: Symptoms include rapid weight loss, blindness,

sudden increase in blood pressure, and breathing rate increase. Treatment

includes a change in diet, medication, exercise, and insulin shots.

Dwarfism: disease cause by a problem with the pituitary

gland.

o Gland: Pituitary

o Nature of imbalance: Results in abnormally short

stature. Puberty may be delayed, or not at all. It may

result in a tumor.

o Symptoms and treatment: Symptoms include a short

stature, tumor in pituitary, and absence of growth

hormone levels in the blood. Dwarfism can be

treated through procedures involving inserting

sections of DNA that code for HGH into certain

strains of bacteria. The altered bacteria end up

producing GHG as a waste product.

Gigantism

o Gland: Pituitary

o Nature of imbalance: Excess of HGH production prior to puberty

o Symptoms and treatment: Symptoms are the result of abnormal growth of long bones in

the skeleton. Treatment includes using microsurgical removal of tumor from the

pituitary gland.

Acromegaly

o Gland: Pituitary

o Nature of imbalance: Excess HGH production during adult years. People with this

condition tend to have abnormal heads, hands, and feet.

o Symptoms and treatment: Symptoms include excessive thickening of bone tissue, and

spinal deformities. Treatments include surgical removal of tumor, radiation therapy, or

injections.

Hyperthyroidism

o Gland: Thyroid

o Nature of imbalance: Thyroid makes too much thyroid hormone.

o Symptoms and treatment: Symptoms include difficulty concentrating, fatigue, frequent

bowel movements, increased appetite/ sweating, irregular periods (girls), weight loss.

Treatment includes surgery, anti-thyroid medication, and radioactive iodine.

Hypothyroidism

o Gland: Thyroid

o Nature of imbalance: Thyroid does not make enough thyroid hormone.

o Symptoms and treatment: Symptoms include sensitivity, constipation, depression,

fatigue, heavy periods (girls), joint pain, weakness, and weight gain. Treatment includes

medication to maintain levels.

Rickets

o Gland: Thyroid

o Nature of imbalance: Lack of vitamin D.

o Symptoms and treatment: Symptoms include bone tenderness, dental deformities,

impaired growth, and skeletal deformities. Treatment includes medication and a vitamin

D supplement.

Osteomalacia

o Gland: Thyroid

o Nature of imbalance: Softening of bones due to lack of vitamin D/ calcium.

o Symptoms and treatment: Symptoms include bone weakness, muscle weakness, and

bone pain. Treatments include a vitamin D and calcium supplements, as well as

monitoring general health.

Seasonal Affective Disorder (SAD)

o Gland: Thyroid

o Nature of imbalance: Mood change with seasons.

o Symptoms and treatment: Symptoms include difficulty waking up, morning sickness,

oversleeping, over eating, weight gain, and lack of energy. Treatment includes light

therapy, medication, and behavioural therapy.

Cushing’s Syndrome

o Gland : Thyroid

o Nature of imbalance: It is a disorder when your body is exposed to the levels of

hormone cortisol.

o Symptoms and treatment: Symptoms include upper body obesity, bone pain, backache,

acne, round faces, and easily bruised skin.

Addison’s Disease

o Gland: Adrenal

o Nature of imbalance: Decreased cortisol and aldosterone.

o Symptoms and treatment: Symptoms include weight loss, nausea, and low sex drive.

Treatment includes replacing those hormones through medication.

4. Goiter: swelling of the neck resulting from enlargement of the thyroid gland.