Exam 1 (Endocrine, ear and eye)

Macula Lutea

"Yellow spot" an oval shaped area located lateral to the optic disk, in the exact center of the retina. It has mostly cones and within the macula lutea is a small pit called the fovea centralis. -the fovea centralis has only cones and is therefore the center of visual acuity

What are steroid based hormones?

Steroid hormones are made from cholesterol, meaning they are lipid soluble. This allows the hormone to diffuse through the cell membrane unaided. It will then travel through the cytosol and enter the nucleus of the cell through the nuclear pores of the nuclear envelope. Once inside the nucleus, it binds with the receptor-chaperonin complex. This allows binding to DNA to initiate transcription to the mRNA = protein synthesis

CN IV: Trochlear nerve innervation

Superior Oblique

Adrenocorticotrophic hormone (ACTH)

Target cells in the outer portion of the adrenal gland, specifically the adrenal cortex. Hormones that are secreted by the adrenal cortex serve many functions

Testes and Ovaries

Testes produce testosterone which stimulates sperm production and facilitates the growth of male secondary sex characteristics such as axiallary and public hair, deepened voice. Ovaries produce estrogen and progesterone

What are the three sections of the adrenal cortex?

The adrenal cortex secretes a group of hormones called corticosteroids. It is divided into three sections called the zona glomerulosa, zona fasiculata, and the zona reticularis.

What is the anterior pitutary gland and what hormones does it produce?

The anterior pituitary is called the adnohypophysis. It produces and secretes hGH, TSH, FSH, PRL, ACTH and LH

Refraction

The bending of light, it occurs 4 times between the time it reaches the cornea to the photoreceptors 1) between the air and the cornea 2) between the cornea and aqueous humor 3) between the aqueous humor and the lens 4) between the lens and the vitreous humor

Cochlea

The cochlea looks like a snail. It coils about 2 1/2 times and has three chambers: 1) scala vestibuli- superior chamber 2) scala media - below vestibuli 3) scala tympani- below the media

Zona Reticularis

The deepest layer that secretes gonadocorticoids, which include androgens (testerone) and estrogen

What is the hypothalamus?

The hypothalamus is considered a neuroendocrine organ because it is also part of the central nervous system. The hypothalamus is connected to the pituitary gland by a stalk-like structure called the infandibulum

What is a Negative feedback system?

The levels of most hormones are regulated by a negative feedback system. An example would be testosterone. The hypothalamus produces a hormone called Gonadrotropic releasing hormone (GnRH). GnRH goes to the anterior pituitary gland and directs it to produce a hormone ICSH. ICSH travels to the testes, which results in the production of testosterone in the testes. Low levels of testerone is the stimulus to turn on the production of GnRH in the hypothalmus, which in turn stimulates the prodution of ICSH from the anterior pituitary gland. This stimulates the production of testosterone at the testes. When the proper amount of testosterone has been produced, this shuts off the production of GnRH from the hypothalamus. Therefore, proper levels of a particular hormone turn off the production of the hormone that caused its production. This is the definition of a negative feedback system.

Vestibule (middle portion of ear)

The membranous labyrinth in the vestibule is made up of two sacs connected to each other by a duct. The sacs are called the utricle and the saccule. The utricle and the saccule contain receptors called maculae. The macula in the utricle respond to horizontal movement of the head. The macula of the saccule respond to vertical movements. The utricle is continuous with the semicircular ducts. The saccule is continuous with the cochlear duct.

Semicircular Canals (there are three)

The membranous labyrinth of the semicircular canals are referred to as semicircular ducts. Each duct was a widened section called an ampulla. Within each ampulla are receptors called crista ampullaris. These receptors respond to rotational movements of the head. The endolymph within the ducts flows over these receptors, stimulating them, providing information about our balance. Neurons in the brain then properly initiate impulses to the cerebellum, which communicates with the cerebral cortex. The cerebral cortex then sends impulses to the skeletal muscles that must contract in order for us to maintain our balance and equilibrium

Middle ear (Tympanic Cavity)

The middle ear is a small cavity that houses the three smallest bones in the body, collectively the ossicles. They are from lateral to medial: the malleus, incus and stapes. These bones form synovial joints with each other and are crucial for normal hearing. The malleus is attached to the medial aspect of the tympanic membrane.

Zona Fasiculata

The middle layer that secretes glucocorticoids. These increase blood glucose levels in the body under prolonged stress. This provides us a source of energy. Glucocorticoids include cortisol, cortisone, and cortiocosterone

Zona Glomerulosa

The outermost layer that secretes mineralocorticoids. THe most common is aldosterone which stimulates the retention (reabsorption) of sodium at the kidney. This is crucial because if we did not reabsorb sodium, we would be unable to reabsorb water because water follows salt

Prolactin (PRL)

The target cells for PRL are cells that produce milk (mammary glands)

Thyroid stimulating hormone (TSH)

The target cells for TSH are the thyroid gland

What is the anatomical composition of the thyroid gland?

The thyroid gland is made up of two lobes that are connected to each other by the isthmus. It has spherical openings called follicles. Follicle cells produce thyroglobulin which is composed of iodine and tyrosine, stored inside colloids. This is what makes up T4 and T3. The other types of cells that surround the follicle are called parafollicular cells (C cells) which produce calcitonin

Optic Disc (BLind spot)

This is where the optic nerve exits the eye. It is located in the fundus (posterior wall) of the eye. It is called the blind spot because no photoreceptors are located there.

What are the parathyroid glands?

Tiny structures located on the posterior aspect of the thyroid gland. Usually there are four, but it varies from person to person. It secretes parathyroid hormone (PTH) which causes an increase in blood calcium.

Pineal Gland

hangs from the third venticle in the brain. It produces melatonin which promotes drowsiness. Production of melatonin increases in darkness

Growth Hormone Inhibiting Hormone (GHIH or somatostatin)

inhibits the secretion of human Growth Hormone from the anterior pituitary gland

Prolactin inhibiting hormone (PIH)

inhibits the secretion of prolactin. This hormone is actually the same substance we call dopamine. Dopamine is a NT and a precursor to noepinephrine

Triiodothyronine (T3)

made up of 3 iodide ions and 2 molecules of tyrosine. Most t3 is produced at the target cell by removing one iodide ion from T4

Thyroxine (T4)

made up of 4 iodide ions and two molecules of tyrosine. It is the major hormone secreted by the thyroid gland

Auricle (pinna)

part of the ear that we normally think of as the "ear". The superior portion of the pinna is made up of elastic cartilage and is called the helix. The inferior portion is called the lobule

Leutinizing hormone (LH) (gonadotropic)

plays a role during the menstrual cycle in females. High levels of it precede ovulation. In males, LH stimulates the production of testosterone by cells called interstitial cells. Therefore, LH in males is sometimes referred to as Insterstitial cell stimulating hormone (ICSH)

Calcitonin (CT)

responsible for moving calcium and phosphate from the blood and putting it into the bone. The movement of calcium from the blood to the bone is called deposition, which lowers blood calcium levels. Also from thyroid gland

Tympanic membrane

separates the outer ear and middle ear

Corticotropic Releasing Hormone (CRH)

stimulates the secretion of adrenocorticotropic hormone (ACTH) from the anterior. ACTH is sometimes simply called corticotropic hormone

Gonadotropic releasing hormone (GnRH)

stimulates the secretion of gonadotropins from the anterior pituitary glands. The two gonadotropins are follicule stimulating hormone (FSH) and luteinizing hormone (LH)

Growth Hormone Releasing Hormone (GHRH)

stimulates the secretion of human Growth hormone from the anterior pituitary gland

Prolactin releasing hormone (PRH)

stimulates the secretion of prolactin from the anterior pituitary gland

Thyrotropin Releasing Hormone (TRH)

stimulates the secretion of thyroid stimulating hormone from the anterior pituitary gland

Human Growth Hormone (hGH)

targets muscle cells and bone during growth. This is also called somatotrophic hormone (STH). Oversecretion during childhood leads to giganism, whereas undersecretion leads to pituitary dwarfism. Oversecretion in adulthood is called acromegaly, which leads only certain body parts such as the nose and jaw to grow

What is the function of the endocrine system?

to maintain proper levels of substances in the body. It works with the nervous system to maintain homeostasis

Three chambers of the cochlea

1) Scala Vestibuli- the superior chamber. It is located on the other side of the oval window. The fluid that is in the scala vestibule is perilymph 2) scala media, or cochlear duct- chamber below the scala vestibule. The fluid within the scala media is endolymph. The membrane that separates the scala vestibule from the scala media is called the vestibular membrane 3) Scala Tympani- below the scala media. The perilympth in the scala vestibuli is continous with the perilymph of the scala tympani because these two chambers meet at the apex of the cochlear, which is called the heliotrema. -The scala tympani ends at the round window -the scala media and scala tympani are separated by the basilar membrane. On the basilar membrane rests the receptor organ for hearing ,the Spiral Organ of Corti. Over the organ of corti is a membrane called the tectorial membrane. The organ of corti contains hair cells that are long enough to make contact with the tectorial membrane. -sensory nerve receptors of CN VIII are wrapped around the base of the hair cells. Movement of the fluids in the inner ear causes tweaking or movement of the hair cells. This movement is the stimulus that initiates impulses for hearing

How does parathyroid hormone increase blood calcium?

1) causes the release of calcium from the bone to enter the blood (resorption) 2) increases the absorption of calicum from our food 3) At the kidneys, it converts an inactive form of vitamin D into the active form of vitamin D, which is necessary in order for us to absorb calcium 4) causes us to reabsorb calcium at the kidney so calcium does not exit from the urine

Inner Ear (labyrinth)

1) semicircular canals 2) vestibule 3) cochlea

What is diabetes insipidus?

A condition where the hypothalamus is unable to produce enough ADH. This causes increased urination and increased thirst. Due to the thirst center being located in the hypothalamus, a severe blow to the head could result in this inability to produce sufficient ADH

What is Oxytocin?

A hormone that is produced by the hypothalmus and is stored in the posterior pituitary gland. It is released during childbirth to cause uterine contractions. It also causes the "let down" reflex, which allows milk to be ejected during nursing. Suckling is the stimulus that causes this reflex

What are amino acid based hormones?

Amino acid based hormones must bind to a receptor on the cell membrane of the target cell. Binding of the hormone (called the first messenger) sets into motion activation of G protein which activates adenylate cyclase molecule. During this process, ATP is converted to cAMP. cAMP is referred to as the second messenger. cAMP activates an inactive protein kinase. This activated protein kinase stimulates the cell to either secrete a substance, make an enzyme, or open ion channels.

Fibrous Tunic

-The outermost layer. Avascular and consists of 2 regions: 1) Sclera: posteriorly. The sclera is white. In the most anterior aspect of the sclera are openings called the sclera venous sinuses. These openins drain fluid (aqueous humor) from the eye. An inability to drain aqueous humor from these canals leads to glaucoma 2) Cornea- anteriorly. The cornea is transparent. Light passes through the cornea to get to other areas of the eye. Within the cornea are many nerve endings, many of which are pain receptors.

Physiology (pathway) of hearing

-These sound waves enter the external acoustic meatus and hit the tympanic membrane. Once this happens: -the malleus vibrates, which causes the incus to vibrate, and this causes the stapes to vibrate -the stapes then pushes on the oval window -this causes movement of the perilymph in the scala vestibule

Wavelength range and conscious perception of sound

-Wavelengths shorter than 20,000 Hz cause movement of the perilymph in the scala vestibule -This will put pressure on the vestibular membrane, which causes the movement of the basilar membrane -movement of the basilar membrane causes movement of the hair cells ofthe organ of corti, which is the stimulus necessary to excite the receptors that are wrapped around the hair cells. This initiates the impulse for hearing -From the thalamus, impulses travel to the primary auditory cortex of the cerebrum in the temporal lobe, where the conscious perception of sound occurs

Detached retina

-caused by the separation of the pigmented and neural layers of the retina. This causes vitreous humor to seep between the layers and deprive cells of nutrients. It can be caused by a blow to the head or whiplash type action. Symptoms include seeing spots or light flashes

3 steps to focus close up

1) Accomodation- occurs when the ciliary muscles contract. This pulls the ciliary bodies anteriorly and inward toward the pupil. This releases the tension on the suspensory ligaments which allows the lens to bulge 2) Constriction- occurs when the circular muscles of the iris contract- controlled by the parasympathic system 3) Convergence- occurs when the medial rectus muscles contract bilaterally

Three layers (tunics) of the eye

1) Fibrous tunic 2) Vascular tunic (uvea) 3) Sensory tunic (retina)

What are the three different sections of the ear?

1) Outer or external ear 2) Middle ear or tympanic cavity 3) Inner ear, internal ear, or labyrinth The outer, middle, and internal ear are all involved with hearing. Only the inner ear is involved with both hearing and equilibrium.

External Auditory Canal (External acoustic meatus)

Canal through which sound waves travel to the ear drum (tympanic membrane). It is located in the temporal bone. The skin that lines this canal has hairs in it, sebaceous oil glands, and modified sweat glands called ceruminous glands that secrete ear wax, or cerumen. Cerumen is a yellow-brown waxy substance that protects the ear by trapping foreign matter, including insects

Outer or External ear

Consists of the auricle, or pinna and the external auditory canal or external acoustic meatus

Normal Vision

Emmetropic Vision. The lens does not have to change shape when looking at something 20 feet away from the eye

Neural control

Epinephrine (adrenaline) is a NT when it is secreted by neurons. It is a hormone wen it is secreted by the cells of the adrenal glands. Neurons from the ANS stimulate the adrenal gland to secrete epinephrine during times of stress. Another example is when ADH and ocytocin are released from the posterior pituitary gland when neurons from the hypothalamus signal it to do so.

Follicle stimulating hormone (gonadotropic)

FSH targets the ovaries in females. In males, FSH plays a role in sperm production. Secretion begins at puberty, same with LH.

What happens when you focus on an object?

Focusing on an object causes the image to hit the retina upside down. Light rays from the left side of an object hit the right side of the retina, light from the right side of an object hits the left side of the retina. The brain learns early in life to process visual information so we understand where things are

Humoral control

Hormones are released in response to levels of certain chemicals, such as nutrients or ions. For example, a high level of glucose (nutrient) stimulates the secretion of insulin from cells of the pancreas. Insulin lowers blood glucose levels. High levels of calcium in the blood stimulate the secretion of a hormone called calcitonin from the thyroid gland. Calcitonin lowers blood calcium levels. Low levels of calcium in the blood stimulate the secretion of parathyroid hormone from the parathyroid gland. PTH increases the blood calcium levels. Humoral control does not include levels of other hormones

What are the three methods the body uses to control the amount of hormone an endocrine gland secretes?

Humoral, Neural and Hormonal

How can you tell what hormones are made by the hypothalamus?

If it contains releasing or inhibiting, it is made by the hypothalmus

Myopia (near sightedness)

In this condition, all light rays meet in front of the retina. This is usually caused by an eyeball that is too long. Correction for this is concave lens

Presbyopia

In this condition, the lens has lost its elasticity. This prevents it from being able to bend to focus close up

Hyperopia (far-sightedness)

In this condition, the light rays intersect behind the retina. This often happens because the eyeball is too short. Correction for this is a convex lens

Sensory Tunic (Retina)

Inner most tunic with 2 layers 1) Pigmented layer (outer) - made up of a single layer of epithelial cells. Like the choroid, these cells absorb light to keep light from scattering in the eye. Vitamin A is stored in these cells and is needed by photoreceptors in order for the impulse for sight to be initiated. These cells also act as phagocytes, destroying old, dead or damaged parts of photoreceptors 2) Neural (Nervous) layer (inner) - contains the cells which will conduct impulses that eventually lead us to see. Anteriorly, this layer abuts the ciliary body. Where this occurs is called the ora serrata.

Astygmatism

Irregulary shaped cornea or lens

What is the pituitary gland?

It can be divided into the anterior pituitary gland and the posterior. The entire gland is called the hypophysis. It sits in the sella turcica of the sphenoid bone. The posterior pituitary gland stores ADH and oxytocin which is produced by the hypothalmus.

What is the hypothalamus/how many hormones does it produce?

It is a neuroendocrine organ which produces 9 hormones, 7 of which go to the anterior pituitary gland. It is named the master gland since it controls so many functions of the body through secretions of these hormones. The hypothalmus is connected to the pituitary gland via a stalk-like structure called the infundibulum.

What is the thyroid gland?

It is located on the anterior aspect of the neck on the trachea (windpipe) One of the hormones it produces is called thyroid hormone, which is the body's major metabolic hormone. Thyroid hormone increases the metabolic rate of virtually all cells of the body. It consists of two hormones containing iodide and the amino acid tryosine. These are Thyroxine (T4) and triiodothyronine (T3). Both T3 and T4 target bone and muscle cells.

What is the neural layer of the retina made up of?

It is made up of photoreceptors (rods and cones) -Photoreceptors form a synapse with bipolar cells. Bipolar cells form and synapse with ganglion cells. The axons of ganglion cells turn toward the posterior aspect of the eye and exit the eye at the optic disc, or blind spot. Once these axons leave the eye, the structure is called the optic nerve. Within the neural layer are horizontal cells and amacrine cells. Horizontal cells connect rods to cones. Amacrine cells connect ganglion cells to each other

CN VI: Abducens nerve innervation

Lateral Rectus

Lens

Lies behind the pupil, is biconvex and is held in place by the suspensory ligaments. It can change shape by contraction of the ciliary muscles and has no blood supply. Cataracts is a condition which the lens gets cloudy. It is believed that increased exposure to sunlight and heavy smoking increase the risk of getting cataracts. Vitamin C seems to decrease the risk, but supplements increase the risk.

Thymus Gland

Located in the mediastinum just deep to the sternum. It is most active in fetal development and childhood. Among the many immune system cells we have in the body are white blood cells called T-lymphocytes. They are crucial for proper immune system function. T- lymphocytes differentiate in the thymus gland. This gland diminishes in size beginning in late adolescence, becoming fatty, fibrous nonfunctional tissue in adults

Lacrimal Apparatus

Located in the superior lateral aspect of the eye

What are the adrenal glands?

Located just above each kidney (renal = kidney). The adrenal glands are divided into an outer portion called the adrenal cortex, and an inner portion called the adrenal medulla. The adrenal cortex is further divided into three separate sections, each secreting different hormones

Vascular Tunic (Uvea)

Middle layer. This layer is pigmented (light absorbing substance) 1) Choroid- the posterior aspect of the uvea and lies deep to the sclera. It absorbs light and is highly vascularized 2) cililary bodies- continous with the choroid and are located in the anterior aspect of the eye. The ciliary bodies are made up of ciliary muscles and folded structures called ciliary processes. The ciliary processes secret aqeous humor. This liquid provides nutrients and oxygen to the lens, the cornea and some of the cells of the retina. It also carries away metabolic waste. Attached to the ciliary pocesses are ligaments called zonoules or suspensory ligaments. These ligaments attach from the ciliary processes to the lens of the eye. When the ciliary muscles contract, they cause the lens to bulge pulling it slightly forward. This is necssary to allow the eye to focus close up. 3) Iris- colored portion of the eye. It surrounds the pupil, which is the opening through which light passes. Within the iris are two layers of smooth muscle: the circular muscles and radial muscles. When the circular muscles contract, they narrow the diameter of the pupil. When the radial muscles contract, they widen the diameter of the pupil (dilate). The circular muscles are controlled by the parasympathetic NS and the radial muscles are controlled by the sympathetic (fight or flight)

What is the pancreas?

Most of the cells of the pancreas perform exocrine functions ; secreting their digestive enzymes into a duct which travels to the duodenum. Scattered among those cells are clusters of cells called islets of langerhans. The Islets of Langerhans have two different types of cells ; alpha and beta cells. These cells secrete their hormones directly into the blood stream. They respond to glucose levels in the blood. If there is too much glucose in the blood, the beta cells secrete insulin. Insulin lowers blood glucose levels by allowing glucose to enter the appropriate cells. If glucose levels are too low, the alpha cells secrete glucagon, which increases blood glucose levels.

What is a positive feedback system?

Most positive feedback systems only last temporarily. An example would be childbirth, where the fetus gets big enough to stretch the wall of the uterus. The reflex of the uterus is to contract, which produces oxytocin (stored in the posterior pitutiary gland) to travel down the uterus. Oxytocin further stimulates uterine contraction, which causes the release of more oxytocin. The whole cycle ends when the baby is born. Therefore, in a positive feedback system the secretion of a hormone is stimulated by an event which further increases its secretion. An external stimulus must occur in order for the whole cycle to be turned off

Rods and Cones

Rods have receptors for dim light, peripheral vision, shapes, and movement. Cones have receptors for bright light, color, and allow us to focus (provide high acuity vision)

Endocrine Glands

Secrete hormones directly into the blood stream. When an endocrine gland secretes a hormone, it travels through the blood stream to ultimately reach the destination, or target cell

Exocrine Glands

Secrete their hormones into ducts

What is the adrenal medulla?

Secretes epinephrine and norepinephrine. These hormones fall into a category of hormones called catacholamines. They are secreted in high amounts in times of immediate or short term stressors

Hormonal control

Some hormones are secreted into the blood when another hormone stimulates its production. An example is a women giving birth with oxytocin

Aqueous vs Vitreous humor

-The entire anterior segment is filled with aqueous humor -the posterior segment (or vitreous chamber) is behind the posterior chamber and is filled with vitreous humor

Visual Pathway to the Brain

-In the lateral geniculate body, neurons synapse with neurons that form the optic radiation of fibers. These fibers travel to the occipital lobe of the cerebral cortex, where conscious perception of vision occurs

CN III: Oculomotor nerve innervation

-Medial rectus -Superior rectus -Inferior rectus -Inferior oblique

What two hormones are produced by the hypothalamus and stored in the posterior pituitary gland?

ADH and Oxytocin

What is antidiuretic hormone (ADH)?

ADH is produced by the hypothalmus and stored in the posterior pituitary gland. It increases water retention at the kidneys. As blood travels through the hypothalamus, it determines whether or not the sodium to water ratios in the body are correct. If there is too much sodium relative to water, it will cause the release of ADH which will travel to the kidneys. The kidneys will have the body reabsorb water, allowing less water in the urine. Alcohol and caffeine inhibit the production of ADH. This causes you to urinate out more than you drank which can cause dehydration