Bio Test 3

Homeostasis

maintaining relative constant internal environment
Set Point - Sensor signals the Control Center - Triggers response - Effector (cell) performs response

Parameters in the Body that would be good to regulate

body temperature, blood pH, blood pressure, blood glucose, water balance

Negative Feedback Loop

change in variable triggers response that counteracts that change and maintains homeostasis

Positive Feedback Loop

Change in variable triggers response that amplifies that change.

Endotherms

Regulators
Metabolism, body response, behaviorally
Mammals and birds

Ectotherms

Conformers
MOSTLY through behavior
Amphibians, fish, reptiles, invertebrates

Ectotherm 4 Processes

Radiation - heat transfer from warm object (sun)
Evaporation - vaporization of water from a surface (sweat)
Conduction - heat transfer between two objects by direct contact
Convection - heat transfer through movement of air or liquid (fan)

Endocrine System

signaling molecules travel directly via blood
acts throughout body
slower, long-lasting

Nervous System

electrochemical signaling travels to a specific location affecting neurons, muscle, or gland cells
faster, fleeting
specifically along dedicated routes

Neurotransmitters

Act on other neurons, muscles, or glands
Short distance across a synapse

Neurohormones

Released by neurosecretory cells
travel in the bloodstream

Peptide Hormones

Water soluble
cannot travel through plasma membrane
bind to receptor in membrane of target cell
triggers signal transduction (second messenger, kinases, etc.)

Steroid Hormones (lipids)

Lipid soluble
travel through the plasma membrane into the target cell
bind to the receptors in the cytoplasm or inside nucleus
acts as transcription factor
in blood escorted by carrier protein

Factors Affecting Hormone Response

Receptor
Relay proteins in the signaling pathway

Glucose Regulation

Controlled by 2 different hormones produced by pancreas
Beta cells make insulin
Alpha cells make glucagon

When blood sugar rises ____ release _____
When glucose goes down, _____ make _____ to break down Liver ______

Beta Cells
Insulin
Alpha Cells
Glucagon
Glycogen

Location of Alpha and Beta Cells

Pancreas as “islets” (small endocrine organs)

Diabetes mellitus

Blood glucose levels too high

Type 1 Diabetes

Loss of insulin-producing beat cells (autoimmune or viral)

Type 2 Diabetes

Cells resist the influence of insulin and do not take up glucose
Pancreas overproduces insulin and becomes
Body eventually stops making insulin
Can be reversed
7th most common cause of death in US

Ingestion

eating or feeding

Digestion

when food is broken down into small molecules (mechanical and chemical)

Absorption (Transport)

Cells take up small molecules (and deliver to body cells)

Elimination

passing of undigested material

Mechanical Digestion

breaks food into smaller pieces, increasing surface area exposes surfaces to chemical digestion.

Chemical Digestion

cleaves large molecules into smaller molecules (protein to amino acids)

Extracellular Digestion + Body Plans

Most have Alimentary canal with compartments continuous with the body
Simple Body Plan: Gastrovascular cavity single opening (take in food OR dispel waste)
Complex Body Plan: Alimentary canal with two separate openings (mouth and anus)

Digestion Overview

Mouth: amylases break down polysaccharides
Stomach: pepsin breaks down proteins
Small intestine: further breakdown ALL molecules

Where does most digestion occur?

the duodenum of the small intestine

Large Intestine Digestive Role

Mechanical Digestion (propulsion, segmental mixing)
No Chemical Digestion
Absorption of ions, water, minerals, vitamins, and small organic molecules produced by bacteria

Small Intestine Digestive Role

Mechanical Digestion (mixing and propulsion)
Chemical Digestion of carbs, lipids, proteins, and nucleic acids.
Absorption of peptides, amino acids, glucose, fructose, lipids, water, minerals, and vitamins

Stomach Digestive Role

Mechanical Digestion (peristaltic mixing and propulsion)
Chemical digestion of proteins
Absorption of lipid-soluble substances, such as aspirin

jejunum and ileum

second and third parts of the small intestine
Huge surface area (absorption) of folds with villi, microvilli

What happens to nutrients immediately after absorption in the small intestine?

Water soluble nutrients enter blood and are carried to liver through the hepatic portal vein
liver filters toxins and drugs
Fatty acids bypass the portal and enter lymphatic system

Why must nutrient rich blood pass through the liver before reaching the heart

Detoxification of harmful substances
allows liver to regulate nutrient distribution
prevents unregulated glucose, amino acids
acts as body’s metabolic gatekeeper

Hypoosmotic

Lower solute concentration in solution, H2O into cell

Hyperosmotic

Higher solute concentration in solution. H2O moves out of cell

Animal Cells in: Hypo, Iso, Hyper

Lysed, normal, shriveled

Plant Cells in: Hypo, Iso, Hyper

Turgid, Flaccid, Plasmolyzed

Osmoconformer

Isoosmotic with its surrounding
Many marine animals
Less energy expended

Osmoregulator

controls internal osmolarity independent of the environment
freshwater animals and mammals
energy intensive

Nitrogenous Waste

Breakdown of proteins and nucleic acids
3 types: ammonia, urea, and uric acid

Ammonia

Nitrogenous waste
High toxicity, requires losing a lot of water to remove it
Aquatic fish

Urea

Nitrogenous waste
Lower toxicity but requires energy to convert ammonia to urea in liver
Amphibians, mammals, humans

Uric Acid

Non-toxic, requires most energy to make, loses least water
Birds, reptiles, insects, land snails

Transport Epithelia

Specialized epithelial cells that move solutes in controlled amounts
Osmoregulation, nitrogenous waste disposal
Complex tubular networks
Large surface area

What are the 4 excretory functions?

Filtration: water, small solutes, sugars, amino acids, nitrogenous waste filtered out of blood by BOWman’s capsule in nephron

Reabsorption: water and useful solutes are returned to blood ACTIVE TRANSPORT

Secretion: Nonessential solutes or waste are secreted out of the blood ACTIVE TRANSPORT

Excretion: Filtrate is released from the body (elimination)

How do complex body plans deal with the issue of large diffusion distance?

Circulatory systems (fluid, interconnecting vessels, and muscular pumps) are dedicated to transporting materials throughout the body

Hemolymph

Open systems like in insects have fluids ejected over certain areas and then sucked back up into the vessels. Those fluids are mixed with the interstitial fluid outside the cells and it is called hemolymph.

Arteries

Carry blood (usually oxygenated) away from the heart

Veins

Carry blood (usually deoxygenated) towards the heart to the lungs to get oxygen and get rid of carbon dioxide

Transpiration

Loss of water vapor from leaves and other aerial parts of the plant (one direction)
often through stomata
water moves high pressure to low pressure

Cohesion-Tension Hypothesis

The way water makes it all the way up the plant: transpiration provides the pull for the ascent and cohesion/adhesion transmits this pull along the entire length of the xylem

Translocation

movement of sugars inside the phloem that requires active transport (multidirectional)

Sensory Neurons

Receptors transmit information set in motion by external stimuli (touch) or internal conditions (blood pressure)

Interneurons

Integration- connect neurons in the brain or simple ganglia
Many dendrites and synaptic terminals

Ganglia

cluster of nerve cell bodies

Motor Neurons

Transmit signals to muscle cells to contract
Can trigger glandular activity
Many dendrites but few synaptic terminals
Long axons

Composition of Central Nervous System

Brain and Spinal Cord for processing and integration with interneurons

Composition of Peripheral Nervous System

Cranial Nerves
Spinal Nerves
Peripheral Nerves
Afferent/sensory neurons transmit information to CNS
Efferent/motor neurons transmit information away from CNS

Dendrites

Branched projections that receive signals

Axons

Long extension that transmit signals, electric signals originating from Axon Hillock

Synapse

junction between sending and receiving cells; chemical signals

Where is electrical signal converted into chemical signal?

the synapse

Autonomic Nervous System

regulates internal body and controls involuntary and automatic behaviors like breathing and heartbeat
comprised of Sympathetic, Parasympathetic and Enteric Divisions

Sympathetic Nervous System

1/3 of Autonomic NS
flight or flight, stimulates body during stress

Parasympathetic Nervous System

1/3 of Autonomic NS
rest and digest, relaxes after the stress has passed

Enteric Nervous System

1/3 of Autonomic NS
controls digestive system and intestinal tract

Motor System

Skeletal Motor Control

Resting Potential

Membrane potential of resting neuron
around -70mV
Sodium Potassium pump goes against the gradient, pumping 3 Na+ out and 2 K+ in
There are more K + ion channels, which helps keep resting potential

What transport mechanism maintains the resting potential (nothing stimulating the neuron)?

Primary active transport in the Sodium Potassium ATPase pump
ATP is used to move ions against the gradient, 3 Sodium Out, 2 Potassium In

What ion channel states exist at resting potential

Na + channels closed (prevents Na+ leakage and accidental firing of action potential)
K + channels closed
Sodium Potassium Pump maintains resting potential (potential energy for the action potential)

What causes depolarization during an action potential

signal occurs and voltage gated Na+ channels open
Na + flows into cell
membrane becomes less negative
threshold reached, action potential fires

What causes repolarization and the undershoot phase?

Na+ channels inactivate
K+ channels open (resets resting potential)
K+ flows out of the cell
Membrane becomes negative again
Continued K+ efflux causes undershoot (hyperpolarization)

Why can’t another action potential occur immediately after one?

Na + channels are inactivated
Membrane resets after refractory period
Undershoot makes the neuron temporarily resistant to firing
Na

What does it mean to reach threshold, why does it cause an action potential to fire

Depolarization means inside of neuron becomes less negative
stimulus opens some sodium channels, letting sodium enter
if enough sodium enters, the membrane reaches a threshold potential difference where the sodium influx triggers even more sodium channels to open, automatically firing an action potential

Myelin Sheath

allow narrow diameters of axons with high speed of action potential.
Vertebrate axons are mainly myelinated, while invertebrate axons are not.

Factors Affecting Conduction Speed

Axon Diameter: large diameter means low internal resistance and faster conduction

Myelination: provides insulation preventing leak of ions and allow for action potentials to jump between Nodes of Ranvier.

Nodes of Ranvier

small, uninsulated gaps in the myelin sheath and have a high concentration of voltage-gated ion channels which allow action potentials to jump (saltatory conduction)

Chemical Synapses

flexible in function
require chemical neurotransmitters
most common
play role in memory and learning

Electrical Synapses

electrical current flows directly from neuron to neuron (gap junction)
faster, instantaneous
rare

Types of Sensory Receptors

Mechanoreceptors: hearing, balance, pressure, touch
Electromagnetic Receptors: electromagnetic energy, light
Thermoreceptors: heat and cold
Pain Receptors: sense extreme pressure/temperature, damaging chemicals
Chemoreceptors: solute concentration, specific molecules

Photoreceptor Cells

Rods: sensitive to light, enables night vision
Cones: provide color vision
Found in Retina

What is the relationship between Loop of Henle length and an animal’s water‑conservation needs?

Species in arid environments evolve longer Loops of Henle, which create a steeper medullary osmotic gradient that enables greater water reabsorption and therefore more concentrated urine to minimize water loss.

Glial Cell

Nourish and support health of neurons

What cells are the myelin sheath comprised of?

Glial Cells: Oligodendrocytes (CNS) and Schwann Cells (PNS)

Microglia

Glial Cells in the central nervous system that function as scavengers, removing dead cells and harmful pathogens

Ependymal Cells

Glial Cell which produces cerebrospinal fluid that cushions the brain and circulates nutrients

Astrocytes

Glial Cells with many functions, maintain chemical composition of fluid that surrounds neurons, replace neurons, provide nutrients to neurons, and form blood-brain barrier

Iris

Controls the amount of light entering the eye