BIO 141 Flashcards
Receptors:
structure specialized to detect a stimulus
Sense Organs:
nerve endings combined with connective, epithelial, or muscular tissues that respond to a stimulus
General flow of sensory information:
Receptor - sensory neuron - CNS thalamus - sensory cortex perception of the sensation
Labeled-line principle:
based on the fact that each nerve fiber to the brain leads from a receptor that specifically recognizes a particular stimulus type. (Ex: optic nerve)
phasic receptor -
burst of activity and quickly adapt (smell and hair receptors)
tonic receptor -
adapt slowly, generate impulses continually (proprioceptor)
- Adaptation:
a sensory receptors stops firing or adjusts its sensitivity during a prolonged stimulus
By origin of stimuli
interoceptors -
detect internal stimuli
proprioceptors - sense body position and movements
By origin of stimuli
exteroceptors -
detect external stimuli
Chemical Senses: Gustation (taste):
a sensation resulting from the action of chemicals on the taste buds in the mouth
Lingual papillae:
bumps on the surface of the tongue, most of which contain taste buds on their sides
Taste (gustatory) cells:
receptor cells with single microvilli that projects thru a taste pore and interfaces with the chemical in the saliva; modified epithelial cells with lifespan of 7-10 days
Basal cells:
give rise to taste cells
Support cells:
provide structure to the taste bud
- Sweet
- Salty
- Sour
- Bitter
- Umami (taste of amino acids (MSG))
- concentrated on tip
- lateral margins
- lateral margins
- posterior
Olfaction (smell):
a sensation resulting from odorant molecules acting on receptors
in the nasal epithelium of the nose.
Olfactory cells
- olfactory hairs neurons with 20 cilia bind odor molecules in thin layer of mucus axons pass through cribriform plate survive 60 days - Supporting cells - Basal cells
Physiology of Smell
- Molecules bind to receptor on olfactory hair
= hydrophilic - diffuse through mucus
= hydrophobic - transport by odorant-binding protein - Activate G protein and cAMP system
- Opens ion channels for Na+ or Ca2+
= creates a receptor potential
Action potential travels to brain - Receptors adapt quickly
= due to synaptic inhibition in olfactory bulbs
Hormone
chemical messenger secreted into bloodstream, stimulates response in another tissue or organ /// a chemical that is secreted from an endocrine gland/tissue/cell into the body fluids (typically the bloodstream) which has an effect on some target cell or effector.
Target cells
have receptors for hormone ///will respond to the hormone only if it has a receptor specific for that hormone (ie. insulin binds to insulin receptors). It is an analogous system to neurotransmitters and their specific receptors.
Endocrine glands
produce hormones
Endocrine system
endocrine organs (thyroid, pineal, etc) hormone producing cells in organs (brain, heart and small intestine)
True endocrine glands
- Pineal gland
- Thyroid gland
- Thymus gland
- Parathyroid gland
- Adrenal glands
- Pituitary Gland (Hypophysis)
Secondary endocrine structures
- Hypothalamus
- GI tract
- Heart
- Pancreas
- Ovaries
- Testes
- Placenta
- Liver
- kidney
Exocrine glands
- ducts carry secretion to a surface or organ cavity
- extracellular effects (food digestion)
Endocrine glands
- no ducts, release hormones into tissue fluids, have dense capillary networks to distribute hormones
- intracellular effects, alter target cell metabolism
Actions of the anterior pituitary hormones:
GH:
released by somatotroph cells; non-specific effects on cartilage, bone, muscle and fat; causes the liver to release somatomedins (insulin-like growth factors) that stimulate bone and cartilage growth
Actions of the anterior pituitary hormones:
PRL:
released by lactotroph cells; stimulates mammary gland growth and milk production; in males, makes testes more sensitive to LH.
Actions of the anterior pituitary hormones:
FSH:
released by gonadotrope cells; in males, helps regulate spermatogenesis; in females, helps regulate oogenesis
Actions of the anterior pituitary hormones:
LH:
released by gonadotrope cells; in males, regulates the secretion of testosterone by the testes; in females, induces ovulation and the secretion of estrogen and progesterone
Actions of the anterior pituitary hormones:
ACTH:
released by corticotroph cells; causes the secretion of glucocorticoids from the adrenal cortex during times of stress
Actions of the anterior pituitary hormones:
TSH:
released by thyrotroph cells; causes the secretion of the thyroid hormones by the thyroid gland
Features of the posterior pituitary gland:
- Made of neuroendocrine cells that originate in the hypothalamus and terminate in the posterior pituitary gland. Axon terminals release their hormones into the bloodstream surrounding the posterior pituitary gland.
- Connected to the hypothalamus via the hypothalamic-hypophyseal tract
- Two different hormones secreted from the neuroendocrine cells: oxytocin OT (from paraventricular nucleus) and anti-diuretic hormone ADH (from supraoptic nucleus).
Features of the posterior pituitary gland:
Action of ADH:
increases water reabsorption at the collecting duct of the nephrons in response to an increase in blood osmolarity (the blood is too salty, dehydration, etc.)
Features of the posterior pituitary gland:
Action of OT:
induces uterine contractions during childbirth; milk ejection during breastfeeding.
Pineal gland: ENDOCRINE GLAND
- Found in the midbrain
- Secretes hormone, melatonin (at night) and serotonin (during the day); probably involved in circadian rhythms (‘biological clock’); timing of puberty in humans
Thyroid Gland: ENDOCRINE GLAND
- Found on the ventral trachea
- In response to TSH, two thyroid hormones are secreted: T3 triidothyronine and T4 thyroxine from follicular cells
- Action of T3 and T4: maintenance of basal metabolic rate (BMR); increases oxygen consumption and cellular metabolism
- Secretes hormone, calcitonin from parafollicular cells: Lowers blood Ca2+ by mineralizing bone. Moves Ca2+ from the blood and lies it down on bone. Calcitonin is the antagonistic hormone to parathormone.
Parathyroid glands: ENDOCRINE GLAND
- Typically four small glands embedded in the surface of the thyroid glands
- Secretes the hormone, parathyroid hormone PTH or parathormone in response to hypocalcemia (low blood calcium)
- Antagonistic action to calcitonin: Rises blood Ca2+ by demineralizing bone, increasing intestinal Ca2+ absorption, and inhibiting urinary Ca2+ excretion.
Thymus gland: ENDOCRINE GLAND
- Located in the mediastinum
- Secretes a family of thymic hormones that controls
= the development of T lymphocytes
ADRENAL GLANDS;
Adrenal Medulla
- Secretes hormones called catecholamines (epinephrine, norepinephrine) from chromaffin cells
- Catecholamines are released during a ‘fight-or-flight’response; released in response to neuronal signals from the sympathetic nervous system
- Catecholamines increase blood flow to the heart, brain and skeletal muscle and increase metabolic rate.
- Catecholamines released during short-term stress to the body
ADRENAL GLANDS;
Adrenal Cortex
Produces a family of steroid-based hormones called the corticosteroids: glucocorticoids, mineralocorticoids, androgens
glucocorticoids, released during long-term stress to the body
Main effect is on glucose metabolism
Stimulates glycogen breakdown and glucose release from the liver
Stimulates gluconeogenesis: the synthesis of ‘new’ glucose from non-carbohydrate sources (like proteins and fats)
More glucose is moved to the blood for fuel during stress
Suppresses inflammatory response and immune response
Glucocorticoids are released in response to ACTH from the anterior pituitary
mineralocorticoids
Main effect is sodium reabsorption at the distal convoluted tubules in the nephrons (also potassium excretion)
Systemic effect is increased blood volume and pressure
androgens (male sex hormones) and small amounts of estrogens and progesterone:
Maintenance of secondary sexual characteristics
Sex drive?
The Gonads: the testes and ovaries
ENDOCRINE GLANDS
Produce steroid-based sex hormones
Gonadal hormones released in response to FSH and LH from the anterior pituitary gland
Ovaries produce two types of ovarian hormones: estrogens and progesterone
Testes produce a testicular hormone: testosterone.
Sex hormones regulate primary (specific to the genitalia) and secondary (changes to other body parts) sexual characteristics
