Animal Phys. Midterm Study Flashcards
Complex Multicellular Features
- Highly developed mechanisms for adhesion
- Specialized structures for cell communication
- 3-D organization (not all cells in direct contact w/ environment)
- Require mechanisms for transferrring signals
Surface Area & Volume
As organisms get bigger, surface area and volume both grow
Surface / volume ratio shrinks
As SA decreases, more limited by diffusion
Diffusion Limits
- Size must be small for diffusion to meet needs
- Not a lot of storage space for NRG
- Small range of environments
- Reproduce quickly and often
Evolve Multicellularity Pros
- Longer life span
- Cells specialize and are more efficient
- Bigger is better
- Injuries can be sustained
- Harder to prey upon
- Sexual reproduction: increased genetic diversity
Evolve Multicellularity Cons
- Increased energy requirements.
- Can no longer rely on osmosis and simple diffusion
- Longer time to reach adulthood/reproduce
- Infections
- Variety of challenges to overcome…
Ganglia
Groups of nerve cell bodies that process sensory information
Properties of Simple Multicellular Organisms
- Adhesion molecules that cause adjacent cells to stick together
- Little communication or transfer of resources between cells and little differentiation of specialized cell types.
- Most or all of the cells retain a full range of functions including reproduction.
- Every cell is in contact with the external environment.
Cephalization
Concentrating sensory organs and nervous system components at the front of the body
Neurons
Basic functional unit of nervous system
Nervous System
- Network of many interconnected nerve cells
- Sense and respond to the environment
- Coordinate action of muscles
- Control internal function of body
Sensory Neurons
- Send and receive information about an animal’s environment or its internal physiological state
- Respond to physical features such as temperature, light, and touch or to chemical signals such as odor and taste.
Interneurons
- Process the information received by sensory neurons and transmit it to different body regions, communicating with motor neurons at the end of a pathway
Motor Neurons
Produce suitable responses by stimulating muscles.
Axon Terminal
Communicates with neighboring cell through junction (synapse)
Synaptic Cleft
Separates end of axon of presynaptic cell and neighboring postsynaptic cell
Neurotransmitters
Convey the signal from the end of the axon to the postsynaptic target cell.
Signal Transmission
- Stimuli Received by Dendrites and Cell body
- Stimuli summoned at axon hillock (Action Potential triggered if signal is strong enough)
- Action potential conducted to axon terminal –> release of neurotransmitters
- Bind to receptors on postsynaptic cell –> new signal in postsynaptic neuron
Threshold
Input depolarizes cell above threshold potential
Sends Action potential
Depolarization
Increase in membrane potential
Na+ ions enter the cell (voltage-gated channels)
Causes positive charge, and membrane potential rises
Action potential fired at axon hillock
Repolarization
Caused by Na+ channels closing and K+ channels opening
Membrane potential rapidly falls as K+ ions leave the cell
Falls below the resting potential
Refractory Period
Can’t fire action potential
The K+ channels are still closing
Returns to resting as K+ ions are returned via pumps
Myelin Sheath
Insulates axon’s membrane
Spreads charge a greater distance on the axon
Glial Cell
Surround neurons and provide them with nutrition and physical support
Orient neurons as they develop their connections
Astrocytes
Type of Glial Cell
Contribute to blood-brain barrier
Clear neurotransmitters btwn synapses
Glial scar and repair damage
Component of Central Nervous System