From Nerves to Nervous Systems Flashcards
What are the functions of the nervous system?
- maintain homeostatic control-body temp ph
- process integration-require kidney and respiratory system to maintain ph equilibrium
- receive and transduce environmental stimuli-change from one energy form to another-ex light energy coming into eye is transducer
- process info various ways
- Control motor response
What is the nervous system?
excitable nerve groups providing an interface between sensory and motor responses
What three parts is the Sensory-Motor Circuit made up of?
- neuron receptor-neuron or epithelial receptor aka secondary receptor
- motor neuron
- effector cell
What does the neuron receptor do?
primary receptor. report filter and send info to the nervous system
What does the motor neuron do in the Sensory-Motor Circuit do?
Takes the information from the receptor and sends it to another point in the body aka effector cell
What is the effector cell in the Sensory-Motor Circuit?
Muscle or gland
Interneurons
In the circuit between the receptor and motor neuron. Allows for complex integration and interpretation.
Divergence
A single nerve has many coaxons that branch off to different nerve tracks with each a different function,
Example: when you touch a hot stove you pull your hand away, yell, scream, jump, etc
Convergence
Many different neurons directed to a single neuron. Amplify Signal. Pick up the signals and lead to a unified single response. ex the signal neuron will require a threshold to make an action potential-skin little stimuli to make integrative response
Feedback Loops
Neurons begin the process and sustain it over time and example is autonomic processes digestion.
Are the nervous system necessary to support highly integrated and coordinated life?
No.
What are independent effector cells?
A single cell that contains all three components of the sensory-motor circuit. Does not require a sensory or neural innervation to function.
Advantages of the independent effector cell?
Responses are immediate. No cellular organization. Effectors are specific they have one job and do it really well.
Disadvantages of the independent effector cell?
Only have one simple, stereotyped responses to specific kinds of stimuli. No plasticity.
Three Examples of independent effector cells?
- Complex movement patterns of ciliates: Paramecium- control speed and direction hyperpolarized membrane-poke at posterior end K channels open cilia beat faster more frequently
depolarized membrane-poke at anterior end ca channels open back away stimulus - Poriferians- porocytes-allow water to come through-respond to changes in environment
- Cniderian cnidocytes-stingy cells when stimulus brushes up against them release harpoon and take prey only work once work independent of animal
How do radiates show an evolution of true effector/motor nervous systems?
First group to evolve sensory/motor units.
Radial symmetry gives no option for a CNS. Developed sophisticated nerve nets.
What are nerve nets and what do nerve nets do?
Diffused interneuron net between the sensory and motor neurons.
Motor Reflex responses: Like the ones seen in humans cannot control bypass the higher neural centers of control. Stimulus + response
Two types of semi independent nerve nets?
- Fast specific Nerve Net: Bipolar Neurons. Have a preferred direction of transmission. High rates of speed 1-2m/s. Contain some ganglionic masses-pulse makers regions-pulse of bell.
- Slow Diffuse Nerve Net: Multipolar Nuerons. Slower. Regulates the slow local movements of tentacles and mouth and slow contractions that pass away from stimulation net.
What evolutionary changes occurred in bilateral animals?
- reduction in reflex motor units-fewer reflexes allows for higher control centers to take control
- Cephalization-concentration of sensory organs in the cephalic region
- Centralization of nervous control- give control to the neuronal clusters-fast and can implement effector control
- Neuronal Aggregation-large clusters of nerves with specialized functions
ganglia-neuronal cluster outside CNS
nuclei-neuronal clusters inside CNS - Fusion/reduction of nerve cords-spinal cords
Primitive forms of flatworms and nervous development?
Exhibit a Radiate like arrangement of nerve nets, however, they have 5 pairs of nerve cords that aggregate together. Also start to see the aggregation of neuronal tissue up toward cephalic region.
Moderately advanced forms of flatworms and nervous development?
More clusters of nerve found in commissures (link left and right side nerve cords) or nerve ladders
Advanced forms of flatworms and nervous development?
2 pair of Nerve cords. Brain or endow-is not essential for normal daily function. Can remove the brain as it is not required for actions such as swallow food, phototaxic movement, and locomotion. Flatworms can be trained.
What is the nervous development of mollusks?
Highly cephalized (most cephalized of invertebrates with exception of bivalves) with ganglia fused into a few large central masses. More highly developed nerve cords 2 pairs.
What is the circumesophageal ganglia and what is it found in?
Large mass neuronal tissue that encircles the esophagus. Found in the mollusks. It is the brain of the mollusks.
What are the two pairs of nerve cords in mollusks called and what do they do?
- Ventral Pedal Nerve Cord: Innervates the foot.
2. Visceral Nerve cord: Innervate the internal organs and modify/interpret signals coming into the visceral mass.
How are cephalopod circumesophageal ganglia unique from the other mollusks circumesophageal ganglia?
They are the octopus etc…It contains the entire central nervous system. Most advanced. Evolutionary dead end cannot become more highly cephalized.
What is the nervous development in the Annelids?
Bilobate brains: two halves and pair of nerve cords and contain a single ganglionic swelling of each nerve cord per body segment.
Ganglionic Swellings: A swelling is present in each segment and controls the function in each segment. The function is decentralized. Each segment takes care of itself.
Giant neurons: withdrawal response
What is the nervous development in Arthropods?
Refines the basic annelid plan to the highest level of integration seen in the Protosome line.
What type of diet do arthropods have?
Low Sodium diet. Insects highly specialized feeders feed typically on plant sap which is low in sodium. Perineurium-thin layer of impermeable layers around neurons to sequester all the sodium they collect here so their neurons function.
What are the three distinct brain regions of the arthropod and what is its function?
- Protocerebrum - integrates all visual sensory that comes from the compound eyes
- Deutocerebrum- receives and processes all sensory information from the antenna
- Tritocerebrum- receives and processes all the sensory info from the minor antenna and the mouth
What are the segmental ganglia in arthropods?
Arthropods advanced the nervous plan seen in the annelids and the rest of the sensory information is received and processed throughout the body.
The segmental ganglia have clusters of neurons that do a specific variety of jobs called central pattern generators.
What do arthropod central pattern generators do?
Group of neurons organized in nerve cord ganglia that produce a complex series of neural activity patterns responsible for specific motor actions.
Example: the legs and flying with insects like wont stop flying till legs hit ground.
Also open up spiracles for more Co2 oxygen. a bursting neuron in metathoracic ganglia acts as pacemaker
How is the nervous system of vertebrates different form invertebrates?
- Highly centralized
- CNS is in bony chambers for protection
- Large number of neurons
What three regions are vertebrate brains divided into and what is the function of each?
- Rhombencephalon-hindbrain largest region contains autonomic functions.
Pons medulla-where the spinal cord comes into brain stem and expands
cerebellum-proprioreception-pressure, angular momentum, stress, deformation joint/muscles ex learn how to walk - Mesencephalon-midbrain most primative
fish/amphibians-most complex behavior
Submammalian- processing and some relay
Human- relay station little processing - Prosencephalon-forebrain 2 parts
1. diencephalon-thalamus hypothalamus posterior pituitary send to cerebrum for processing and signals to right motor response
2. telecephalon-varied bc of evolution. in fish and amphibians least developed and it causes smell. In reptiles and birds it has no obvious purpose. And in mammals lobes greatly developed it is our area of greatest dominance and processing sensory and motor function measure intelligence.
How to measure Intelligence?
- Brain Size-no
- Cephalic Index- weight of brain over weight of body-no
- Cephalic Volume-number of neurons-no
- Cortical Surface area- folded area-no
- Cortical volume ratio- thickness- yes!
