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