Bio 2 Test 3 Nervous System - Exoskeletons

Central Nervous System (CNS)

brain and nerve cord; brain and spinal cord in vertebrates

Peripheral Nervous System (PNS)

All neurons and their projections that are outside of the CNS

Nerve systems that have classes of cells

Neurons (nerve cells) and glia (neural glial cells)

Neurons

cells that send and receive electrical and chemical signals to form each other and other cells throughout the body

Neurons are present in all animals except ?

Sponges

What varies widely as a function of size and behavioral complexity?

Neurons

Cell Body or Soma

Contains nucleus and organelles

Dendrites

extension of cell body, single or branching; receive incoming signals

Axon

extension of cell body; carries signals to other cells (away from cell body); typically single, varies widely in length

What has branches and may be wrapped in myelin?

Axon

Glia

Surround neurons and perform numerous functions; 1000x more numerous than neurons

Astrocytes

Metabolic support; maintain stable concentration in ions in extracellular fluid

Microglia

Participate in immune functions; remove cellular debris

Myelin Sheath

Sheath is interrupted in non-insulated nodes of ranvier

Types of Glia

Astorcytes, Microglia, Myelin Sheath, Oligodendrocytes (CNS); Schwann cells (PNS), radical glial cells

3 Main Types of Neurons

Sensory neurons, motor neurons, interneurons

Sensory Neurons

Detect information from the outside world or internal

Sensory Neurons are also called?

Afferent neurons

Motor Neurons

Send signals away from CNS (efferent neurons) to elicit response

Interneurons

Form interconnections between other neurons; critical interpretation of information and elicited response

Reflex Arc

Stimulus from sensory neurons sent to CNS, little or no interpretation ( few or no interneurons), signals transmitted to motors neurons to elicit response;

Is reflex arc a quick and automatic response?

Yes

Membrane Potential

Gatekeeper

What generates electrical signals?

Neurons and Muscle Cells

Why is the cell polarized?

Due to membrane’s permeability

What causes both chemical and electrical differences (imbalances)?

Differences in ions between inside/outside of neuron

Inside is what?

Negative

Outside is what?

Positive

When a neuron is NOT sending a signal, it is selectively permeable to what?

Cations (+) and Anions (-)

Where are most ions located?

Most ions are near the edge of the membrane because anions on the inside are drawn to the cations on the outside.

Electro-chemical gradient

Imbalance due to differences inside/outside of neuron

Chemicals

K+, Na+, Cl -

3 Factors contributing to resting potential

Sodium Potassium Pump, Polarity, Ion Specific channels allow pass ion movement

Sodium-Potassium Pump

Requires ATP expenditure; Pump 3 Na+ for every 2 K+

Ion Specific channels allow passive ion movement

Membrane is more permeable to K; K channels more frequently open at resting potential

Polarity

More (-) inside neuron

Gated Ion Channels

Voltage-gated and Chemical-gated

Voltage-gated

Open/close in response to voltage changes

Chemical-gated

Open/close in response to chemical

Frequency

Language of the message; higher the frequency, the greater the excitation level

Resting Potential

Imbalance between K+ and Na+ inside/outside; Membrane selectively permeable to K, but channels closed for Na and Cl

Outside Neuron of Resting Potential

10x more Na, 5x more Cl

Inside Neuron of Resting Potential

30x more K

Action Potential

Rapid/brief change of a nerve fiber; electrical potential of the impulsive; “Self propagating”; After a passing given point, membrane returns to resting

At give impulse point what happens in Action Potential?

Channels for Na open and Na diffuses in, K is already diffusing out, but increased at impulse

Sodium/Potassium Pump

Complex of proteins in membrane; Pump out Na and carry in K; Returns the imbalance “normally”, movement is from low concentration to a high concentration