Animal Form and Function Flashcards
Tissue
A group of similar cells performing a common function
Organ
A group of different tissues functioning together to do a particular activity
Organ System
Two or more organs working together to accomplish a particular activity
Negative Feedback Loops
Something happens, and the response brings the body back to homeostasis
Positive Feedback Loops
Something happens and serves only to intensify the thing thats happening. Ex: childbirth (contractions)
Describe the parts of a neuron
- The cell body
- The dendrite, which receives stimuli
- The axon, which sends neurotransmitters
What are the three types of neuron?
Sensory/afferent neuron, motor/efferent neurons, inter/association neurons
Sensory/afferent neurons
These receive the initial stimuli (ex: neurons in retina)
Motor/efferent neurons
These stimulate effectors, target cells that produce a response. Ex: muscle cells, sweat glands
Inter/association neurons
These are located in spinal cord and brain, and reroute signals that they receive from sensory neurons to motor neurons.
What is the resting potential of a neuron and how is it maintained?
About -70 millivolts, and it’s maintained since there are unequal amounts of sodium (out) and potassium (in). Less potassium, which makes the inside of the cell negative since there are also negatively charged proteins there.
How do neurons start working?
A ligand-gated ion channel opens, causing a change in the polarity of the neuron
How do action potentials start?
In response to a ligand that binds to a ligand-gated ion channel, voltage-gated ion channels open, allowing a sudden flood of sodium to rush into the cell. If the depolarization gets the polarity of the cell high enough (threshold potential), it triggers the opening of more voltage-gated ion channels, causing an action potential.
Describe the repolarization of neurons after an action potential.
In response to the action potential, voltage-gated ion channels open un, allowing the potassium inside the cell to leave. This causes repolarization (but, different from the resting potential, the K are outside and the Na are inside.)
Describe hyperpolarization of a neuron
Too many K ions leave during repolarization, causing the membrane to be hyperpolarized @ about -90 millivolts
Refractory period
When the neuron rights itself after having an action potential. Can’t react to any other stimuli during this period.
Myelin sheath
The glial cells that wrap around axons of neurons
Nodes of ranvier
The gaps of unsheathed axon in a neuron that has a myelin sheath. These cause the action potential to jump from nodes to node, causing it to move faster
Electrical synapse
A synapse across a gap junction, which doesn’t require neurotransmitters
Chemical synapse
A synapse that must be bridged with neurotransmitters
How does a signal get sent across a synapse?
- Ca gates open, letting Ca in
- The influx of Ca causes synaptic vesicles to merge with the cell membrane, releasing neurotransmitters into the synapse
- The neurotransmitters bind with receptors on another cell’s dendrites
- Two options: excitatory postsynaptic potential (transmitters start an action potential) or inhibitory pp (transmitters polarize the other cell more, making it harder to action potential-ify it)
Reflex arc
A very fast response involved only a few cells, which isn’t completely synthesized by the brain/spinal cord
What are common neurotransmitters in the CNS?
Epinephrine, norepinephrine, dopamine, seratonin
What are some nonspecific first lines of defense in humans?
- Skin (acidic, oily)
- Antimicrobial proteins in mucous membranes
- Cilia in lungs and nose
- Gastric juice
- Symbiotic bacteria that outcompete everyone
Phagocytes
White bloods cells that engulf pathogens by phagocytosis
Inflammatory response (2nd line)
Histamine is secreted by mast cells, which attracts phagocytes
Immune response
The 3rd line of defense. It is special because it is specific!
What is an antigen?
A molecule that can be identified as foreign
How does the immune system tell what is foreign?
The major histocompatibility complex (MHC). It is a collection of glycoproteins that exists on every cell in a person’s body. It originates from 20 genes, each w. about 50 alleles. Thus, it’s almost impossible that two random people could have the same one.
B cells / humoral response
Lymphocytes that originate and mature in the bone marrow. They respond to antigens. Their membrane surface has antibodies on it. When they encounter an antigen that binds to their antibodies, they proliferate, producing plasma cells and memory cells as daughter cells.
Antibody
A protein that is specific to a kind of antigen.
Plasma cells
B cells that release their specific antibodies, which then tag a bunch of bad antigens
Memory cells
B cells that circulate after an invasion is over, giving immunity to a disease after one has had it once.
T cells/ Cell-mediated response
Lymphocytes that originate in the bone marrow but mature in the thymus gland. T cells have antigen receptors, but they’re not antibodies. They;re used to recognize non-self cells. When they encounter such cells, they divide and produce Cytotoxic T cells and Helper T cells, which kill the nonself things.
What classifies as non-self?
A virus, a self cell that has been invaded and thus displays weird MHC, cancer or tissue transplant cells
Cytotoxic/killer T cells
Recognize and destroy nonself cells
Helper T cells
Stimulate proliferation of B cells and killer T cells
What are the two kinds of immune response?
Humoral (B cells) or cell-mediated (T cells)
Antibiotics
Chemicals derived from bacteria or fungi that are harmful to other microorganisms
Vaccines
Used to stimulate the production of memory cells
Passive Immunity
Obtained by transferring antibodies from an individual who previously had a disease to a newly infected individual. Not effective in the long run, but buys the infected person some time.
Characteristics of hormones
Transported in the blood
V effective
Steroids peptides, modified amino acids
Neurosecretory cells
Cells that link the hypothalamus and the pituitary gland. Structured like neurons, but secrete hormones.
Pituitary gland
- Posterior pituitary stores hormones produced by the neurosecretory cells.
- Anterior pituitary releases tropic hormones when influenced to o so by neurosecretory cells. Tropic hormones regulate hormone production by other glands
Insalin
When the concentration of blood sugar rises, beta cells secrete insulin. Insulin stimulates the liver and other body cells to absorb glucose. Liver and muscle cells convert it to glycogen, adipose cells convert it to fat. Thus, blood sugar goes down.
Glucagon
When blood sugar drops, alpha cells secrete glucagon into the blood. It stimulates the liver to release glucose. This stops when blood sugar reaches normal levels.
Epinephrine and norepinephrine
Stimulate increased blood pressure, heartbeat, cellular metabolic rate.
Thyroxin
An iodine containing hormone produced by the thyroid gland. It governs the metabolic rate of the cells in one’s body. When its levels are low, the hypothalamus secretes thyrotropin-releasing hormone (TRH) which stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH). TSH stimulates the thyroid gland to secrete thyroxin.
Describe some issues one can have if you have thyroid problems
- Goiter occurs when one doesn’t have enough iodine. Thus, the thyroid gland tries really hard to stimulate the release of thyroxin, but fails. This causes and enlargement of the thyroid gland.
- Graves’s disease is caused by antibodies binding to TSH receptors, causing over-production/release of thyroxin, and super high metabolic activity, insomnia, hyperactivity.
Human Growth Hormone
Secreted in the anterior pituitary. Stimulates the liver to secrete growth factors into the blood which stimulate growth (No way!)
Ectotherms
Animals that obtain body heat from their environment.
Endotherms
Animals that generate their own body heat
What mechanisms do animals use to regulate temperature?
- Cooling by evaporation
- Warming by metabolism
- Adjusting surface area (elephants/ears, penguins/groups)
- Countercurrent exchange(blood vessels headed in and out are next to each other)
What are the different mechanisms used by animals to exchange gas with environmental O2?
- Direct w/ environment
- Gills
- Trachae: chitin-lined tubed that permeate their bodies.
- Lungs
What are the steps of gas exchange in humans?
- Nose, pharynx, larynx (voice box)
- Trachea
- Bronchi (2) which branch into bronchioles (many)
- Alveolus
- Diffusion between blood in capillaries and alveoli.
- Bulk flow of O2 through blood
- Diffusion between blood and cells
- CO2 flow back to lungs
- Air out of lungs
How is respiration controlled?
When the body is active, CO2 production is increased. When CO2 enters the plasma, it converts the cerebrospinal fluid into HCO3, which makes the pH drop. This drop causes chemoreceptors in the brain to tell the diaphragm and intercostal muscles to increase the respiratory rate.
Open circulatory systems
These pump hemolymph into a cavity which bathes tissues with nutrient rich fluid, which then goes back to the heart. Ex: insects, mollusks
Closed circulatory systems
Exactly what they sound like. Blood is confined to vessels.
Arteries
Blood vessels moving away from the heart. Split into arterioles, then capillaries
Veins
Blood vessels moving towards the heart. Venules are the mini version of them that merge to form the larger veins.
Right atrium
Deoxygenated blood enters this chamber on the right side of the heart through two veins, the superior and inferior vena cavas
Right ventricle
Blood moves through the tricuspid valve from the right atrium. The ventricle contracts, forcing the blood out into the pulmonary artery to the lungs.
Left atrium
Oxygenated blood comes back to the left atrium
Left ventricle
Oxygenated blood passes through the bicuspid valve from the left atrium. The ventricle contracts, forcing the blood into the body to distribute oxygen.
Autorhythmic cells
Cells in heart tissue that are self excitable and initiate contractions in the heart
What does blood contain?
- RBCs/ erythrocytes
- WBCs/ leukocytes
- Platelets: fragments involved in clotting
- Plasma: liquid portion of blood w/ lots of random stuff in it
