physiology chaoter 2

Tonic receptors

Slowly adapting receptor that fires throughout the stimulation. Provides information on duration to keep brain informed of stimulus.

Types of tonic receptors

Muscle spindles, golgi tendon, chemoreceptors, baroreceptors

Phasic receptors

Rapidly adapting and only responds to change, gives information regarding onset and offset, like vestibule

Examples of phasic receptors

Pacinian corpuscle, semicircular canals

Type A

Myelinated nerve fiber, has fast transmission speed. Subdivided into alpha, beta, delta (Slower), gamma

Types of Ab receptors

Meissner’s corpuscles, hair receptors, pacinian corpuscle, Ruffini end organs

Type Ad

Fast pain, transmits using neospinothalamic tract

Type C

Unmyelinated fibers, small with slow transmission speed of pain. Transmits using paleospinothalamic tract

Neospinothalamic Tract

Senses pain. Ad fibers travel up tract and decussates on dorsal horn of spinal cord. Some terminate in reticular substance but some go to ventrobasal complex of thalamus

Paleospinothalamic Tract

Senses pain. C fibers terminates in laminae II and III of spinal cord, decussates there, and travels through anterolateral columns. Terminate in medulla, pons, and uncommonly the thalamus

Periaqueductal gray area

Has neurons that send axons to the nucleus raphe and raphe magnus then to dorsal horn of spinal cord to inhibit pain

Enkephalin

Secreted by PVN and pariaqueductal gray and respond to serotonin to inhibit type C and type Ad pain fibers

Pain sensitive structures of brain

Dura, blood vessels, venous sinuses, middle menigeal artery

What causes migraine

Abnormal vascular spasms and vasodilation stretching for long periods

Types of taste buds

Circumvallate (Posterior), foliate, (Lateral) fungiform (Center)

Locations of taste buds

Sweet at anterior, salty at anterolateral, posterolateral, bitter at posterior, umami at center

Lateral inhibition

Receptor gets influenced by input from other receptor cells, inhibits closest neighbors first

Weber Fechner Relationship

2.5% is the smallest change in stimulus intensity we can perceive

Ruffini End Organ

Slowly adapting and responds to continued deformation of skin and joints

Pacinian Corpuscle

Rapidly adapting tactile receptor by rapid movement and deep pressure

Anterolateral System

Senses pain, temperature, crude touch, pressure, tickle, itch, sexual sensation. Contains smaller myelinated and unmyelinated fibers and decussates in spinal cord

Layers of the cortex

Layers 1 & 2 receive diffuse input from lower brain centers

Layer 2 & 3 neurons send axons to closely related areas of cortex

Layer 4 receives incoming signals

Layer 5 (brainstem) & 6 (thalamus) send axons to distant locations

Somatic area 1

Senses discrete localization, judge degree of pressure, determine weight of object

Somatic association areas

Located behind somatic sensory cortex and receive inputs from somaticsensory cortex, ventrobasal nuclei of thalamus, visual and auditory cortex to decipher meaning

Astereognosia

Inability to determine shape or form of an object

Bradykinin

Pain chemical from tissue damage

Labeled line

A direct dedicated pathway for each chemical receptor and its tract. A bitter receptor activates its bitter neuron, which enters the bitter medulla, thalamus, then the gustatory complex

Population Coding

Allows you to focus on a primary taste sensation, where receptors of taste are stimulated more frequently in a syncryonous pattern. The brain interprets the patters to identify the taste

Perceiving odor

Oderant binds to Gprotein and creates cAMP to open ion channels on receptor.

The small receptor and its local graded potential sends to the olfactory nerve and the unmyelinated axons pass through cribiform plate of ethmoid bone through pyriform cortex. No thalamus relay

Muscles on ossicles

Stapedius, tensor tympani

Tubes in cochlea

Scala tympani, scala media, scala vestibuli

Organ of Corti

Receptor organ that generates nerve impulses. Lies on basilar membrane and lined with stereocilia with tectorial membrane on top

Kinocilium

Stereocilia protrusion that when bent causes depolarization, and bent the other way causes hyperpolarization. Directionally sensitive

Role of outer hair cells

Contains motor proteins that amplify sound towards inner ear

Signal transduction of sound

As stretch gated potassium channel filaments are stretched, the channel opens and potassium moves INTO cell. Voltage gated calcium channels open which exocytose neurotransmitter

Place principle

Different frequencies of sound will cause basilar membrane to vibrate at different positions, which determines pitch

Auditory pathway

Cochlear n, medulla, pons, corpa quadrigemina, inferior colliculi, thalamus, auditory cortex

Lateral nuclei

Detect direction by difference in sound intensity between the two ears

Medial nuclei

Detects direction by the time lag between the two ears

Utricle

Sensory organs in vestibule that detect orientation of head with respect to gravity

Crista Ampullaris

Sensory structure inside ampulla that when bent excites the hair cells

Semicircular duct

Detect angular acceleration, each one contains a crista ampullaris. They predict dysequilibrium

Presbyopia

Inability to visually accommodate via denaturation of lens proteins

Myopia

Near sightedness. Corrected by concave lens

Layers of retina

Outer nuclear layer (Photoreceptor)

Outer plexiform layer (PR Synapses on B Cell)

Inner nuclear layer (Horizontal, amacrine, bipolar cells)

Inner plexiform layer (Bipolar cell synapse on ganglion cell)

Ganglion cell layer (Axons of G cells form optic nerve)

Horizontal cells

Connect laterally between rods and cones and bipolar cells, cause lateral inhibition for visual acuity

Amacrine cells

Lateral inhibition

W Cells

Ganglion cell that determines directional movement in visual field

X Cells

Ganglion cells that determine color

Y Cells

Ganglion cells with a large receptive field that look for major changes in visual field

How does rhodopsin open sodium channels

Opsin is in c retinal position, and light isomerizes to trans retinal. Light activated rhodopsin activates a gprotein transducin, then activates cGMP phosphodiesterase to destroy cGMP, rhodopsin kinase deactivates rhodopsin and cGMP is regenerated, reopening sodium channels

Sodium Conductance in light

Light activated rhodopsin activates transducin

Transducin activates cGMPase which destroys cGMP

cGMP levels decrease and close sodium channels

Photoreceptors hyperpolarize

Classes of hormones

Steroids, peptides, modified amino acids, modified fatty acids

Steroidogenesis

Cholesterol 27C is converted into pregnenolone 21 C by desmolase. Pathway to cortisol. Pregnolone is converted into progresterone by 3 beta HSD. Pathway to aldosterone. Progeserone converted into Androgen 19C by C17, 20 lyase. Androgen converted into estrogen 18C by aromatase.

Types of binding transport proteins

Plasma transport proteins, Sex hormone binding globulins, albumin

Mechanism of steroid action

Dissociate from binding protein

diffusion of steroid into cell

ligand binding to nuclear receptor

activation of R hinge model & dimerizartion

translocation

binding DNA

increase/decrease gene transcription

translation of RNA into protein

alter cell function

What is the BC domain

DNA binding domain for steroid receptors. Zinc fingers bind to HRE

What is the D domain

Region on steroid receptor where it conforms to a hinge shape upon ligand binding. It dissociates with HSP, dimerizes, and interacts with DNA

Post translation modification for protein

Protein is synthesized as a pre-pro hormone, enters endoplasmic reticulum, turned into pro-hormone, enters goli to be packaged and modified, and releases as a hormone within a vesicle

Aminopeptidase

Cleaves at N terminus of protein hormone to catabolize

Components of G protein

Alpha stimulatory, alpha inhibitory that interact with effector, beta, gamma

Carboxypeptidase

Cleaves at C terminus of protein hormone to catabolize

G protein linked receptor mechanism

Hormone binds to receptor to increase affinity of R to G protein

G protein binds to receptor and causes conformational change

GDP dissociates due to activation and GTP binds to alpha subunit

alpha dissociates from beta and gamma, so alpha-GTP binds to adenylate cyclase effector

effector is activated which generates cAMP to activate signal

GTP breaks into GDP + Pi, alpha GDP dissociates from effector and alpha GTP reassociates with Beta and gamma

Where does the pituitary receive blood supply

Superior hypophysial, inferior hypophysial

Type of corticotroph

ACTH

Types of gonadotroph

LH, FSH

Type of thyrotropin

TSH

Type of somatotroph

GH

Type of lactotroph

PRL

What endocrine hormones does the hypothalamus produce

GnRH, GHRH, SS, TRH, DA, CRH

Role of CRH

Stimulates ACTH

Role of ACTH

Stimulates adrenal cortex to secrete cortisol

Role of dopaminergic

Inhibit prolactin

Role of prolactin

Stimulates breast development and milk production

Role of TRH

Stimulate TSH

Role of TSH

Stimulates thyroid to secrete T3 & T4

Role of Somatostatin

Inhibit growth hormone

Role of growth hormone

Stimulate protein synthesis, carbohydrate, and lipid metabolism in many organs and tissues. Stimulates IGF1 in liver

Role of GHRH

Stimulates growth hormone

Role of GNRH

Stimulates FSH and LH

Role of FSH and LH

Stimulates germ cell development, estradiol and progesterone in females, testosterone in males

What does the supraoptic nucleus produce

Vasopressin

What does the paraventricular nucleus produce

Oxytocin

Axoplasmic transport

Transportation from cell body to synaptic knob

Herring bodies

Clusters of granules in the posterior hypothalamus, stored in synaptic knob

Mechanism of oxytocin secretion

Random but continuous firing patterns from suckling excites neurotransmitter release and depolarizes neurosecretory neurons.

Functions of oxytocin

Milk letdown, smooth muscle myometrium contraction, umbilical artery and vein contraction increased sensitivity to E2 estrogen and desensitization to P4 progesteron

Mechanism of ADH secretion

A hemorragic rhythmic burse firing pattern depolarizes neurosecretory neurons

Function of ADH

When osmolarity increases with excess salt (280mOsm/kg), ADH increases to conserve H2O, resulting in urine being hypertonic

Barorceptors send change in pressure through CN IX and X to brainstem, increasing BP via arteriole smooth muscle contraction

Functions of GH

Anti insulin effects. Lipolysis, protein synthesis, carbohydrate breakdown, linear bone growth

Somatomedins

Secreted by liver in response to GH

Role of small follicular cells

Synthesize T3 & T4

Role of large follicular cells

Synthesize calcitonin

Role of colloid space

Storage of hormone

Thyroid Hormone Synthesis

NIS System actively transports iodide into small follicular cell. TPO converts iodide into iodine and attaches it to tyrosinase. Coupling reaction in follicular cavity, thyroglobulin breakdown into T3 T4. Deiodinase removes iodines. Diffusion from follicle to capillary, then released and carried via binding proteins to peripheral tissues

Role of thiocyanates and perchlorates

Inhibit iodine transport

Role of thionamides and sulfonamides

Block iodine attachment to tyrosine

What are goitrogens

Ingested compounds that cause endemic goiter and treat excess thyroid hormone

Role of thyroid hormone

Increased synethsis and breakdown of thyroid hormone, lipogenesis/lipolysis, glycolosis, glycogenolysis, gluconeogenesis