Cell Signaling

Quorum Sensing

Communication based on the quantity of bacteria in a location

Juxtacrine Signaling

Communication between adjacent cells requiring cell junctions to connect cytoplasms.

Gap Junction

The membrane-bound molecule in animal cells that allows for juxtacrine signaling

Plasmodesmata

The membrane-bound molecule in plant cells that allow for juxtacrine signaling

Paracrine Signaling

Communication between nearby cells by secreting signalling molecules into extracellular fluid.

Autocrine Signaling

Paracrine signaling where the signal is both secreted and received by the same cell

Synaptic Signaling

Paracrine signaling occurring between neurotransmitters sending signals over synapses.

Endocrine Signaling

Communications involving the use of hormones that move through an entire organism.

Epinephrine glycogen phosphorylase pathway

Adrenal glands secrete epinephrine

Epinephrine activates a g-protein coupled receptor and a secondary messenger

This activates the glycogen phosphorylase enzyme

This enzyme produces glucose from glycogen

Reception

Ligand interacts with a receptor. Only certain molecules interact with each receptor

Transduction

Step or series of steps that converts a signal molecule to a form that can make a specific cellular response. Signal transduction pathways can amplify signals and allow for more control over the pathway.

Response

A specific cellular process being activated:

• Activation of an enzyme

• Activation of a gene

Termination is when a ligand bind is reversed. Many ligands do different things for different cells called specificity.

G Protein Linked Receptor Mechanism

Membrane bound receptor that when activated transfers a phosphate group from a molecule of GTP which activates the G protein causing a response.

Tyrosine Kinase Mechanism

Membrane bound receptor that when activated, forms a dimer, becomes phosphorylated, and allows a response to occur. Stay active until ligand unbinds.

Kinase

A molecule that takes phosphate groups from ATP or GTP and transfers it to a new molecule

Ligand Gated Ion Channel

Membrane bound receptor that changes shape once a ligand binds, allowing ions to flow.

Phosphatase

Enzyme that removes a phosphate group from a protein. Opposite of kinases.

Cholera Toxin Mechanism

Activates a g-protein receptor involved in water homeostasis causing chloride ions to be released into the intestines creating an osmotic pull causing diarrhea.

Intracellular Receptors

Receptors within the cytoplasm. Ligand must be small and nonpolar to cross the lipid bilayer.

Aldosterone Mechanism

Aldosterone (a mineralcorticoid) binds to intracellular receptors which binds to DNA stimulating transcription. This activates protein production and active transport of Na into the cell via a pump.

Renin Angiotensin Aldosterone Pathway

Cells that are sensitive to kidney blood flow creates renin with less flow. Liver produces angiotensinogen which reacts with renin in the bloodstream to form angiotensin 1. In the lungs, angiotensin 1 becomes angiotensin 2 which stimulates aldosterone production in the adrenal cortex. Aldosterone acts on kidneys to increase Na retention, increasing water retention, increasing blood pressure causing a negative feedback loop.

IP₃ and Ca²⁺ Regulation

IP3 is a secondary messenger that regulates Ca. 1st messenger binds to g-protein coupled receptor. Phosphorylase splits PIP into DAG and IP3. IP3 binds to a ligand gated ion channel in the endoplasmic reticulum allowing Ca to flow into the cytoplasm.

Physiology

Function of the body and how each part works

Anatomy

Structure of the body

CRH, ACTH, and Adrenal Axis Pathway

Hypothalamus produces CRH. Stimulates production of POMC in the anterior pituitary. POMC is processed into ACTH which stimulates the adrenal cortex. Adrenal cortex produces mineralcorticoids (regulate Na), glucocorticoids (influence metabolism of carbs, fat, and proteins), and androgens (forming secondary sexual characteristics)

ACE Inhibitors

ACE (angiotensin converting enzyme). Inhibit production of angiotensin 2 from 1. Decreases aldosterone production, decreases Na retention, decreases blood pressure.

Glucocorticoids

Influence the metabolism of carbs, fat, and protein. Derived from cholesterol: hydrophobic. Produced in adrenal cortex. Activates intracellular cytosolic glucocorticoid receptors stimulating DNA transcription. In muscles: inhibit glucose uptake, increase blood glucose, In immune system: decrease inflamation, breakdown of fat, incraese cardiac output.

Cushing Syndrome

Hypercortisolism (cortisol is a glucocorticoid). Leads to hyperglycemia, diabetes, and adrenal overgrowth

Addison’s Disease

Hypocortisolism (cortisol is a glucocorticoid). Leads to hypoglycemia from decreased gluconeogenesis, decreased ability to release energy (fatigue).

Androgens

Produced in the adrenal cortex. Effect masculinizing: hair growth, muscle growth, libido, clitoral growth. DHEA (produced by testicles) and androstenedione can be converted into testosterone and dihydrotestosterone.

TRH, TSH, T3, and T4 Axis Pathway

Hypothalamus releases TRH (Thyrotropin releasing hormone) which causes the anterior pituitary to release TSH (Thyrotropin stimulating hormone) which causes the thyroid gland to grow and release T3 and T4 (thyroid hormones). Negative feedback on TRH and TSH

T3 and T4 Function

Iodine is in the T3 and T4 molecule. T3 has one less and is more active. Stimulate DNA transcription. Increase in metabolism, heat production, growth, heart rate, alertness.

Hyperthyroidism

Hypothalamic: Increased TRH production.

Pituitary: increased TSH production.

Thyroid: Auto-antibodies that stimulate TSH receptors

Fever, sweating, weight loss, increased heart rate and bp, tremor, irritable, restless

Hypothyroidism

Hypothalamic: decreased TRH

Pituitary: decreased TSH

Thyroid: autoimune destruction, damage, iodine deficiency

Shortness, mental issues, depression, slowed thinking, slow heart rate, cold intolerance, lethargy, dry skin hair nails.

GnRH, LH and FSH Axis Pathway

Hypothalamus produces GnRH causing the pituitary to release FSH and LH going to the ovaries and testes.

LH and FSH Effects

Ovaries: converted to estrogen and progesterone (negative feedback on hypothalamus and pituitary), stimulation of ovarian follicle,

Testes: Testosterone production (can pass through membranes stimulating transcription), sperm production, fluid production

Oxytocin

Hormone that plays a role in smooth muscle contraction, specifically uterine.

Vassopresin/ADH

Helps with osmolarity regulation: hyperosmolarity triggers hypothalamus causing thirst. Triggers pituitary to release vasopressin triggering increased channels in the kidney increasing retention. ADH causes vasoconstriction increasing BP.

SSRI Antidepressants

Work by inhibiting reuptake of serotonin after being released by neurotransmitters