EXAMS Flashcards
Ingestion
When food enters the mouth or oral cavity, the salivary glands release saliva, containing mucin, lysozymes, buffers, and amylase. Mucin makes things slippery; buffers neutralize the pH level which protects your teeth; the amylase breaks down carbohydrates; and the lysozymes kill bacteria and micro-organisms. Teeth mechanically break up the food. The chewed up and digested food is pushed to the back of the throat or the pharnyx as a bolus (a ball of food). The epiglottus covers the trachea, so the food doesn’t go into the lungs. Food is pushed into the esophagus which is covered in smooth muscle. Involuntary contractions push the food down the esophagus into the stomach.
Digestion
The food passes through the esophagial or cardiac sphincter that closes off the stomach to keep the food in. The stomach mechanically digests the food by churning itself because of the smooth muscle on it. It chemically digests proteins by denaturing them by acidic juices. Pepsinogin resides in the stomach. Hydrocholoric acid is secreted into it and activates pepsinogin as pepsin. Because of these acids, the stomach has a pH of 2. The mucus lining of the stomach protects it from the gastric juices. The food stays in here for 2-6 hours then exits through the pyloric sphincter into the duodenum. The chyme mixes with digestive juices from the pancreas, the gall bladder, and the liver. The pancreas makes enzymes, trypson and chymotrypsin, and an alcoline solution rich in bicarbonate. The enzymes break down the proteins, and the solution buffers the acidic chyme. These are secreted into the duodenum through the pancreatic duct. The liver makes bile which is stored in the gall bladder and secreted into the duodenum through the bile duct.
Absorption
The rest of the small intestine includes the jejunum and the ileum. They contain many folds containing villi and microvilli. These villi absorb nutrients from the food and spread them through the blood stream because the villi are connected to capillaries. The cecum then ferments plant cells like cellulose. The colon absorbs 90% of the water we intake and contains bacteria that live off of the food we eat. But they also produce Vitamin B and K as a biproduct.
Elimination
This begins in the rectum where feces or wastes are stored until they are ready to exit through the anus. There are 2 sphincters in between the anus and the rectum. One is involuntary; one is voluntary. This regulates the release of the feces.
Tissues
Muscle (cardiac- heart, inv. smooth- lines organs, inv. skeletal- large body muscles, vol.), epithelial tissue (outer layer), connective (connects things like bones), nervous (neurons, spinal cord, brain).
4 stages of cell cycle
Interphase
- G1- growth of cell, all normal organelles are made
- S- synthesis or copying of DNA
- G2- duplication of organelles and molecules need for cell division
Mitotic Phase
- cell division
5 stages of mitosis
- interphase- centrioles and other organelles are duplicated, chromatin copied, mainly for growth
- prophase- mitotic spindle begins to form, chromatin coiled into chromosomes, nucleus disappears, centrosomes move toward poles
- metaphase, prometaphase- microtubules from centrosomes cont. to form the mitotic spindle and attach themselves to chromosomes at the kinetachore, nuclear envelope dissolves, sister chromatids pushed by spindle fibers to center of cell, lineup along metaphase plate
- anaphase- sister chromatids separate and move toward the poles of the centrosomes
- telophase/cytokinesis- chromosomes begin to unravel. mitotic spindle, microtubules, and centrosomes disappear, nucleus appears again, cytoplasm pinches off to form 2 new cells
components of blood
platelets: fragments of cells used for clotting
RBS (erythrocytes)- can transport both CO2 and O2, what makes blood red
WBS- fight infection, 5 types: basophils, lymphocytes, eosinophils, neutrophils, monocytes)
plasma: 90% water, gas is sometimes carried, ions, proteins, hormones, waste, and nutrients
Response to cut
- platelets attracted to collagen fibers of ECM
- in contact, sticky substance that attracts more platelets
- clotting factors: prothrombrin to thrombrin and fibrinogen to fibrin
- releases net of fibers stopping blood flow, creating scab/clot called thrmobris
generation of heartbeat
-SA node generates action potential
-travels through gap junctions to other cells
-travels to AV node and purkinje fibers
causes valves to open and close
neuron communication
When a neuron has resting potential, is it waiting for an electric impulse to activate it. An electrical impulse cannot travel across the space between the neurons called the synapse, so a chemical message has to be generated. When an action potential hits the axon terminal, it opens the calcium-gated ion channels. Calcium rushes into the cell. This causes the vesicles containing neurotransmitters to bind with the membrane on the pre-synaptic cell and release the neurotransmitters into the synapse through exocytosis. The neurotransmitters then bind to receptor proteins on the post-synaptic cell. A ligand then also binds to the cell, causing the ligand-gated channels to open. Na rushes into the cell and starts an action potential again. The neurotransmitters are then pushed back by proteins on the pre-synaptic cell and are repackaged in vesicles. However, the neurotransmitters that do not make it back are eaten by enzymes.
action potential
Na rushes in. Na channels close, and the K channels open, pumping K with its gradient out of the cell. The cell is then slowly changed back into its old state with more K ions inside the cell and more Na ions outside the cell by the Na/K pumps resetting the concentration gradient. The changing of the ion position across a membrane is an action potential. This action potential then jumps from node to node if neuron has myelin. The Na still inside the cell on the past node triggers the action potential to continue on the next node by making the Na channels open again.
