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• Homeostasis is the maintenance of optimal internal physical and biochemical conditions for survival, achieved through physiological systems and processes.
• Physiology studies the physical and biochemical processes and functions of living organisms.
• The receptor detects changes and sends input to a control center. The control center sends output to an effector, which corrects the balance.
• Large size provides advantages such as improved predation and reduced vulnerability.
• Multicellularity allows organisms to attain larger sizes and to evolve specialized tissue types.
• Single cells are constrained in size due to the surface area to volume ratio.
• To increase size, the number of cells increases, and cells become specialized.

Levels of Organization and Tissue Types:

• Tissues consist of groups of cells performing a similar function.
• Epithelial, muscle, connective, and nervous tissues are the four broad types.

Epithelial Tissues

• Epithelial tissues are used for compartmentalization and allow separation between internal and external parts of an organ.
• Stratified squamous epithelium separates internal and external parts of the organ.
• Columnar epithelium lines internal organs and has secretory and absorptive functions, enabling substance movements.
• Cuboidal epithelium makes up tubules and ducts and has secretory and absorptive functions.
• Secretory cells, such as those in the stomach lining, secrete digestive juices and acids, and can be found in other glands.

Muscle Tissues:

• Muscle tissues generate force.
• Cardiac muscle causes heart contractions.
• Smooth muscle provides motility to internal organs and controls blood vessel diameter.
• Skeletal muscle is responsible for voluntary movements of the body.

Connective Tissue

• Provides support.
• Bone tissue provides structural support for muscles to move.
• Adipose tissue cushions and supports organs, provides thermal insulation, and stores energy.
• Blood cells include RBCs for carrying gases and WBCs for protecting against foreign substances.
• Ligaments and tendons connect bones to bones and muscles to bones.

Nervous Tissue:

• Nervous tissues process information.
• Sensors/cells in the retina encode information about the external environment.
• Glia support neurons and modulate signaling, providing insulation and immune functions.
• Neurons communicate information from sensors, store and integrate information, and communicate commands.
• Organs consist of multiple tissue types.

Homeostasis in Detail:

• Multicellular organisms require a stable internal environment.
• Cells face variations in temperature, nutrient availability, and metabolic wastes.
• General physiological mechanisms to maintain homeostasis include negative and positive feedback.
• Negative feedback reverses deviations from a set point, regulating many hormones.
• Positive feedback increases deviation but culminates in an event that resets the system.
• Feedforward information anticipates changes, as seen in the stress response.
• An analogy for homeostasis is a house's heating/cooling system.

Temperature and Animals

• Animals exchange heat with the environment through conduction, radiation, convection, and evaporation.
• Environmental temperatures can fluctuate and pose problems for organisms, raising concerns about survival and Q10 values.
• Animals are classified based on thermoregulatory characteristics as homeotherms, poikilotherms, endotherms, ectotherms, and heterotherms.
• Thermoneutral zone exists in endotherms and endotherms alter metabolic rate to regulate temperature when too cold or hot

Adaptation and Regulation

• Thermoregulatory adaptations include antifreeze, heat shock proteins, isozymes, blood shunts, sweating/panting, shivering, and behavioral changes.
• Acclimatization refers to alterations in physiological processes to environmental changes.
• Brown fat and non-shivering heat production.
• Thermogenin uncouples proton movement from ATP production.
• Brown fat produces heat and is found mainly in newborn infants that use it to keep heat.
• Ectotherms regulate body temperature through behavioral adaptations, blood flow to skin (marine iguanas).
• Heart rate and temperature quickly decreases in marine iguanas when diving into the ocean to preserve heat and smooth muscles are cut off when diving.
• Countercurrent heat exchange mechanism includes fluids exchanging heat in tubes and equilibrate parallel and touching.

Hot and Cold Fish

• Hot fish maintain higher temperatures and include tuna and great whites.
• Blood oxygenated in gills goes through arteries just under the skin.
• Hot fish tubes are arranged countercurrently.
• Overall these hot fish cannot maintain body temps
• Cold fish reflect the temperature of water
• Blood is oxygenated and cooled to water temp in the gills

Size and Shape

• Larger animals are subject to overheating so they have lower metabolic rate.
• Body size, metabolism, and heat
• Larger animals are subject to overheating so they have lower metabolic rate
• Animals tend to be larger in colder climates, and have shorter, thicker limbs.
• Regulation occurs largely in the base of the brain with the hypothalamus acts as the primary control center, and to some extent the sensors.
• Hypothalamus acts as a thermostat when cooled metabolic heat production and body temp will rise.
• If the hypothalamus is heated, the squirrels metabolic rate and temperature fall

Hypothermia

• Torpor, hibernation, and heterothermy are forms of regulated hypothermia and can last a day or hours.

Animal Hormones:

• Hormones involves sending out a chemical message to any part of the body to instruct what to do, chemical messengers that affect the function of some target cell
• Hormones are the only cells that respond to the hormone and target cells possess a sensory receptors.
• Endocrine mediation secretes chemicals into the bloodstream to target distant cells.
• Autocrine mediation/autocrine substances feed back to influence the same cells that secreted them.
• Paracrine mediation secretes chemicals that affect adjacent cells.
• Ectocrine mediation releases substances such as pheromones to communicate with others.

Types of Hormones

• Protein hormones have peptide bonds forming a complex protein.
• Steroid hormones are formed from cholesterol.
• Amine hormones have can have multiple copies of one amino acid (ex adrenaline aka epinephrine)
• Steroids are nonpolar molecules, protein hormones are polar and water soluble, and amine hormones may be either.
• Extracellular signals signal transduction into intracellular responses.
• A nonpolar signal diffuses directly across the lipid bilayer to encounter its cytoplasm or nucleus receptor and a polar/large signal cannot diffuse through the cell membrane and needs a membrane-embedded receptor.

Mechanism of Hormones

• Steroid receptor acts as a transcription factor.
• Cortisol enters the cytoplasm and binds to the receptor and ligand to enter the nucleus.
• Three units of a g protein coupled receptor, receptor, inactive effector protein must actitvate a the g protein.
• Activation of the effector protein/activated g subunit activates an effector protein causing changes in cell function.
• Cellular responses to hormones involves "fight or flight” response.

Endocrine and Nerve System

• Hypothalamic neurons produce antidiuretic hormone, transport them to the posterior pituitary, and work with the endocrine system.
• The Pituitary gland (anterior and posterior) and the Posterior pituitary produces neurohormones
• ADH is present: collecting duct is highly permeable to water and results in a small volume of concentrated water and releases more of these neurohormones.
• When there is no ADH, the collecting duct is not permeable to water.
• Inducing labor for birth via oxytocin includes positive feedback
• Breastfeeding involves two hormones:
• Oxytocin comes from the posterior pituitary and is described as a milk letdown
• Prolactin comes from the anterior pituitary with sucking stimulates nerves in the nipple and areola to travel to the hypothalamus.
• In response, the hypothalamus stimulates the posterior pituitary to release oxytocin and the anterior pituitary to release prolactin
• Overall, Negative feedback loops typically regulate hormone secretion

Hormonal Effects and Diseases

• External/internal conditions trigger a "Stress" response involves epinephrine/norepinephrine release.
• Elevated cortisol inhibits the release of CRH/corticotropin and stimulates the release of corticotropin by anterior pituitary corticotrophs.
• Adrenal glands produce epinephrine and steroids.
• Cross section of a thyroid gland: requires iodine in diet and Follicle cells take up iodide by Na cotransport
• Elevated cortisol inhibits release of CRH by hypothalamic neurosecretory cells Elevated cortisol inhibits release of corticotropin by anterior pituitary corticotrophs
• Goiters include overproduction of thyroid hormones (Graves disease).

Pancreas and Hormones

• Acina cells in the pancreas handle digestion and exocrine processes, while the Islets of Langerhans secrete pancreatic cells.
• Diabetes includes not enough insulin and a type 2, cells lacking receptos.
• The control of insulin and glucagon is not hypothalamic.
• Gonadal hormones play a role in gamete production/reproduction and actication.

The Nervous System

• Cells include the cell body, nucleus, dendrites, axon and axon terminals.
• The nervous system encodes, processes, and stores information to regulate physiology and behavior.
• The Neuron's electrical charge is due to distribution of ions ( voltage of the cell established w membrane of the cell).
• Now imagine that the cell membrane is leaky (more permeable) to Na w equilibrium potential for Na
• Neurons leaky to K+ and the resting membrane potential is closely related to the equilibrium potential of K+ w negative ions
• K+ leaves the cell once it becomes “leaky” causing the cell to be negative.
• Neurons communicate via electric potentials and action potentials are sudden, large, transient changes in the membrane potential

Action Potentials

• Let's dissect an action potential to understand how they work
• Ion channels act as gates and the Sodium ions entering depolaroizes the cell
• Additional voltage gated Na channel activation games open, causing a rapid spike of depolarization- an action potential
• The refractory period makes it so the action potential doesn't spread
• Conduction: Voltage gated na channels open in response to spreading membrane depolarization, myelin insulates, a depolarization current spreads to adjacent areas of the membranes and the cell travels quick via upstream Na
• Myelin protects from loss of electricity and there is Saltatory conduction with Nodes of ranvier
• synapse: junction between pre synaptic neuron &.. and synapse: junction between pre synaptic

Synapses

• There is the presynaptic vs postsynaptic cell.
• Electrical synapses allow action potentials to spread directly.
• Type of chemical synapse includes neurotransmitter molecules released from a presynaptic cell induce changes in a postsynaptic cell
• Presynaptic input allows voltage gated calcium channels
• ACh is involved in the post synaptic cell
• There are different neurotransmitters and the ions are different
• An injury to the lining of a blood vessel exposes collagen fibers, where the platelets adhere and become sticky The structure of capillaries and Arteries
• Capillary walls consist of a single layer of endothelial cells and Arteries have more elastin/connective tissue.
• Most fish have a heart with four chambers and gills.
• The lungfish heart has a partially divided atrium and has a a dual circuit.
• The human heart and circulation occurs with the superior and inferior vena cava bringing deoxygenated blood into the heart from capillaries in the body
• The heart beats at a regular rate from pacemaker cells and not neurons.

Electrocardiograms

Electrocardiograms use graphs to map electrical currents. The Cardiac cycle involves a systole, diastole, and “lub-dup" and a valve will open when it reaches the diastole.

• The period of diastole with ventricle is relaxing and Pressure in the cuff measures from heart rate.
• An ECG typical electrical recording is used with corresponding arterial pressures and heart sounds
• Electrical changes occurring within heart musculature radiates over the skin on an ECG.
• Q, R and S correspond to contraction of the ventricles
• The Cardiovascular disease is related to ¼ of all deaths in the US and is often due to hardening of arteries.
• Damaged endothelial cells attract WBCS, create fatty Plaque and a build up causes platelets in a blood vessel causing a throumbus.