Lectures on Neurobiology, Muscle, Digestion, and Immunity

Presynaptic Cell

Signal comes from this cell

Synaptic cleft

Gap (~20nm) where chemicals cross

Postsynaptic cell

Starts action potential in this cell

Action Potential (AP)

Depolarizes membrane of the presynaptic neuron

Voltage gated Ca2+ channels

Open in response to AP in presynaptic neuron

Neurotransmitter

Chemical that diffuses across the synaptic cleft

Ligand-gated ion channels

Channels that open when neurotransmitter binds to them

Postsynaptic potential

Generated when neurotransmitter binds to receptors

Excitatory Postsynaptic Potential (EPSP)

Depolarizes the postsynaptic membrane

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarizes the postsynaptic membrane

Axon hillock

Integrates EPSPs and IPSPs

Threshold

If sum of EPSPs minus IPSPs is greater than this, an AP occurs

Long Term Memory

Permanent connections in the cerebral cortex

Short Term Memory

Held for a short time and accessed by temporary links in hippocampus

Neuronal Plasticity

Brain's ability to change and adapt after birth

Long-term Potentiation (LTP)

Strengthening of synaptic transmission over time

Conditions for LTP in presynaptic neuron

High frequency of AP's and depolarization from a second stimulus

AMPA receptors

One type of ligand-gated channel involved in LTP

NMDA receptors

Another type of ligand-gated channel involved in LTP, blocked by Mg2+

Glutamate

Neurotransmitter that activates NMDA receptors

Sleep

Consolidates memories

NMDA

Releases Mg2+

Na+ & Ca2+

Some flow in

AMPA receptors

Upregulate

Sensory Reception

Detect Stimulus

Sense Organs

Organs that detect stimuli

Sensory Transduction

Converts stimulus to receptor potential

Receptor potential

Change in membrane potential

Sensory receptor

Depolarizes → AP triggered

Higher receptor potential

More frequent AP's

Perception

Brain processes information

Chemo receptors

Taste and smell

Mechano receptors

Touch, hearing

Photo receptors

Light, seeing

Hearing

Sense changes in external vibrations

Equilibrium

Balance controlled by sensing movement of fluid in ears

Mechanoreceptors

Used in both hearing and equilibrium

Sound

Waves of air or water pressure

Pinna

Collects sound waves

Auditory Canal

Channels waves to tympanic membranes

Tympanic Membrane

Thin membrane - vibrates → transmits to middle ear

Middle Ear

Air-filled cavity

Ossicles

3 small bones - Malleus → Incus → Stapes

Cochlea

Spiral tube, where sound is detected

Hair cells

Mechanoreceptors with cilia

Skeletal Muscle

Movement

Muscle fiber

Muscle cell

Myofibrils

Bundles within muscle fibers

Sarcomere

Basic unit of contraction

Thin filaments

Have 3 types of proteins including actin

Thick filaments

Made of 350 myosin molecules

Sliding Filament Model

Describes muscle contraction mechanism

Cross bridge

Formed when myosin binds to actin

Power Stroke

ADP + Pi released - myosin head bends & pulls thin filament to center of sarcomere

Myosin

A protein that binds to ATP and breaks cross-bridge.

ATP hydrolysis

The process where ATP is broken down, allowing the myosin head to return to a high-energy position.

Creatine phosphate

A molecule that transfers its phosphate to ADP, providing energy for muscle contraction.

Glycogen

A stored form of glucose in muscle fibers, consisting of hundreds of glucose units.

Rigor mortis

The stiffening of muscles after death due to no ATP production, preventing new bridges from forming.

Cardiac Muscle

Muscle found in the heart walls that must contract together and has high Na+ permeability.

Intercalated discs

Specialized junctions in cardiac muscle that permit ions to move between cells and allow action potentials to pass quickly.

Smooth Muscle

Muscle found in the digestive tract, bladder, and blood vessels, characterized by slow and sustained contractions.

Heterotrophy

The characteristic of all animals being heterotrophs, meaning they must consume food.

Ingestion

The first stage of food processing where food enters the body.

Digestion

The process of breaking down complex organics into smaller pieces, increasing surface area for enzymes.

Mechanical digestion

The physical process of breaking down food into smaller pieces.

Chemical digestion

The process where enzymes break down food through hydrolysis.

Absorption

The stage where cells take up molecules from digested food, often into the bloodstream.

Elimination

The final stage of food processing where undigested material passes out of the system.

Compartments

Structures that help avoid self-digestion by separating digestive processes.

Single Cell Digestion

Digestion occurs within food vacuoles and lysosomes.

Multicellular Digestion

Involves extracellular digestion in compartments.

Gastrovascular Cavity

A digestive cavity with one opening found in thin/tiny animals.

Alimentary Canal

A digestive system with two openings, allowing one-way food movement.

Accessory Glands

Include 3 pairs of salivary glands, pancreas, liver, and gall bladder.

Peristalsis

Smooth muscle contractions that move food through the digestive tract.

Sphincters

Ring-like muscular valves that control the passage of food.

Pre-indigestion

Digestive processes triggered by salivary secretion before ingestion.

Mechanical Digestion

Involves teeth chewing food in the oral cavity.

Bolus

A mass of chewed food formed by the tongue.

Epiglottis

Prevents food from entering the airway during swallowing.

Esophagus

Muscular tube connecting the pharynx to the stomach.

Stomach

An elastic organ that can hold about 2 liters and digests proteins.

Gastric Glands

Cells in the stomach lining that secrete mucus, HCl, and pepsinogen.

Pepsin

An enzyme that breaks down proteins into smaller polypeptides.

Chyme

The mixture of food and digestive juices in the stomach.

Small Intestines

About 6 meters long, with a high surface area for nutrient absorption.

Villi and Microvilli

Structures in the small intestine that increase surface area for absorption.

Pancreatic Juice

Contains bicarbonate and enzymes for digestion in the small intestine.

Bile

Produced in the liver and stored in the gallbladder, aids in fat digestion.

Duodenum

The first section of the small intestine where most chemical digestion occurs.

Monosaccharides

The end product of carbohydrate digestion from polysaccharides and disaccharides.

Amino Acids

The end product of protein digestion from polypeptides.

Nucleic Acids

DNA and RNA, only digested in the small intestine.

Lipids

Ingested as triacylglycerols; emulsified by bile salts for digestion.

Chylomicrons

Particles that transport triglycerides after absorption in the small intestine.

Large Intestines

Mainly absorbs water and has four divisions: ascending, transverse, descending, sigmoid.

Hepatic Portal Vein

Carries nutrients absorbed by the intestine to the liver for processing.

Opportunistic Feeders

Animals that can feed on a variety of food sources.

Chemical Energy

Used for ATP