The Senses & Endocrine system

lectures 16, 17

General senses

have receptor cells within multiple organs

–touch, pain, body movement, etc.

Special senses

have receptor cells within specialized sensory organs

– taste, smell, hearing, balance,

and vision

Chemoreceptors

respond to chemicals to

detect taste, smell, and blood pH

Photoreceptors

respond to light

Mechanoreceptors

respond to physical forces to detect hearing, motion, touch, etc.

hermoreceptors

detect changes in temp

Nociceptors

respond to tissue damage (pain)

Receptive field: gs

is area of body supplied by a single sensory neuron. precision determined by size of field

First-order neuron - gs

carries signal from sensory receptor to CNS

Second-order neuron - gs

crosses over and carries signal to thalamus

Third-order neuron - gs

carries signal to primary somatosensory cortex

Lingual papillae

are bumps on tongue surface to grip and position food

Taste buds

contain gustatory receptor cells for detecting taste stimuli

– most are found in lingual papillae

Five primary taste sensations

salty, sweet, sour, bitter, and umami

– influenced by aroma, temp, etc.

Olfactory neurons

have receptors that bind chemicals in air

Olfactory nerves

are bundles of axons from olfactory neurons

Olfactory bulb

is structure where olfactory neurons synapse

Olfactory tracts

are bilateral bundles of nerve fibers that connect to brain

Auricle

is visible part of ear that collects sound waves

– determines direction of sound

External acoustic meatus

is passage for sound through temporal bone

Tympanic membrane

is membrane that transmits sound to middle ear

Auditory ossicles

are three small bones that transmit sound to inner ear

malleus

is hammer-shaped ossicle attached to the tympanic membrane

incus

is middle, anvil-shaped ossicle

stapes

is stirrup-shaped ossicle attached to the oval window

Auditory tube

is passage that connects from middle ear to throat

─ opens to equalize air pressure

Oval window - IE

is membrane in vestibule where stapes attaches

Vestibule - IE

is central chamber that is involved in equilibrium

Semicircular canals - IE

are three tubes that detect rotation of head

Cochlea - IE

is snail-shaped cavity involved in hearing

Round window - IE

is membrane at end of cochlea

Vestibular duct

is a perilymph-filled cavity behind oval window, in cochlea

Vestibular membrane

separates the vestibular and cochlear duct

Cochlear duct

is endolymph-filled cavity that contains the spiral organ, in the cochlea

Basilar membrane

separates the cochlear and tympanic ducts

Tympanic duct

is a perilymph-filled cavity behind round window, in cochlea

Spiral organ

is the receptor organ for hearing in the cochlear duct

Hair cells

convert fluid movements to nerve signals

Stereocilia

are extensions of hair cell that send signals when bent

Tectorial membrane

lays over stereocilia of hair cells

Nerve signals transmitted

via CN VIII

Sclera

is the white, fibrous outer layer of the eye

Cornea

is clear covering that allows light to pass through anterior eye

Choroid

is the highly vascular middle layer of the eye

Ciliary body

is smooth muscle that controls the shape of the lens

Iris

is colored portion of the anterior eye that surrounds the pupil

Pupil

is open hole at center of iris that light passes through into eye

Retina

is inner, light-sensitive layer that contains photoreceptors

Optic disc

is spot on the retina where axons leave and blood vessels enter

─ no photoreceptors present

Macula

is oval-shaped pigmented area for high-resolution, color vision

Aqueous humor

is clear, watery fluid that fills space anterior to lens

Lens

is transparent structure that focuses light on retina

Vitreous body

is clear gel that fills the space posterior to lens

Rod cells

are specialized for low-light vision

─ use rhodopsin as photopigment

Cone cells

are specialized for color vision

─ use photopsins as photopigments

Bipolar cells

connect rod and cone cells to retinal ganglion cell

Retinal ganglion cells

transmit image-forming and non-image information to the brain

Endocrine system

produces hormones to change activity of other organ systems

Hormone

is a signaling molecule that induces a response in a target cell

─ travel via bloodstream

─ bind to hormone receptor

Feedback loops

occurs when outputs are routed back as inputs to form a loop

─ may be positive or negative

Two types of hormones?

1. derived from amino acids

2. derived from steroids

What are the two ways hormones bind?

• Hormone may cross cell membrane to bind to target genes on DNA

• Hormone may bind at cell surface and use secondary messenger

Hypothalamus

is brain region that regulates the pituitary gland

Pituitary gland

is gland attached to inferior aspect of hypothalamus

Anterior pituitary

is glandular anterior region

Posterior pituitary

is posterior region made up of nervous tissue

Follicle-stimulating hormone (FSH)

stimulates gamete production

Luteinizing hormone (LH)

stimulates production of sex hormones

─ triggers ovulation in females

Thyroid-stimulating hormone (TSH)

stimulates thyroid hormone release

Adrenocorticotropic hormone (ACTH)

causes ↑ secretion from adrenal cortex

Growth hormone (GH)

promotes growth of body tissues

Prolactin (PRL)

promotes milk production

Posterior pituitary

stores and secretes hormones produced by hypothalamus

Antidiuretic hormone (ADH)

Antidiuretic hormone (ADH) stimulates water reabsorption by kidneys

Oxytocin (OT)

stimulates uterine contractions during labor

─ bonding and sexual response

Pineal gland

is a pine-cone shaped gland attached to epithalamus

Melatonin

regulates sleep cycles

─ ↑ production in darkness

Thyroid gland

is large gland in anterior neck

Calcitonin

reduces blood calcium levels

Thyroid hormone

increases basal metabolic rate and heat production

─ triiodothyronine (T3) and thyroxine (T4)

─ requires iodine

Parathyroid glands

are small glands on posterior side of thyroid gland

Parathyroid hormone (PTH)

increases blood calcium levels

Pancreas

is organ located posterior to the stomach

Pancreatic islets

are specialized clusters cells that have endocrine functions

Glucagon

increases blood glucose

─ secreted by alpha cells

Insulin

decreases blood glucose

─ secreted by beta cells

Adrenal glands

are glands located at top of each kidney

Adrenal cortex

is outer layer of adrenal gland

Adrenal medulla

is inner layer of adrenal gland

Aldosterone

increases blood sodium and decreases blood potassium levels

─ ↑ blood volume and BP

─ renin-angiotensin-aldosterone system, part of adrenal cortex

Cortisol

increases blood glucose and inhibits inflammation

─ released due to long-term stress, part of adrenal cortex

Androgens

to supplement sex hormones produced by gonads, part of adrenal cortex

Epinephrine

promotes fight-or-flight response to acute stress, part of adrenal medulla

Norepinephrine

promotes fight-or- flight response to acute stress

─ released in small amounts, part of adrenal medulla

What are secretions from adrenal medulla mediated by?

sympathetic neuro

Ovaries

are female gonads that release ova and produce sex hormones

Estrogens

regulates menstrual cycle and develops female sex characteristics

Progesterone

prepares body for and helps maintain a pregnancy

Testes

are male gonads that produce sperm and sex hormones

Testosterone

stimulates male secondary sex characteristics and sperm production