Nervous System

Nervous System

Ch 28, Sections 28.1-28.9

• Which type of immune response is always disadvantageous to a person?

• A) cell-mediated • B) inflammatory • C) humoral-mediated • D) autoimmune • E) All immune responses are advantageous.

The Nervous system controls the entire body

• It is the interface between stimulus and response

• Allows animals to interact with their environment

• Brain and spinal cord: central nervous system (CNS)

• Other nerves: peripheral nervous system (PNS)

The nervous system is the interface between stimulus and response

Neurons come in 3 basic types: Sensory neuron, Interneuron, Motor

The Neuron is the base unit of the nervous system

Neurons are large cells supported by a variety of glial cells

• Human neurons can be 1m in length

• Potentially thousands of glial cells support a single neuron

• Provide nutrition, support, insulation

• Schwann cells are an example

The synapse is the connection point between neurons

Many synapses make complex information processing possible

• Cell interactions form logic circuits

• AND, NOT, etc. gates are formable

• Human Brain: 100 billion neurons

• Up to 10,000 synaptic connections/neuron

The nervous system runs on electricity

• Current- The movement of charge (electrons or ions)

• Voltage- potential energy stored in a charge disparity over distance

• Nervous system uses ions (Na+, K+, Cl-, Ca++) to send signals from one neuron to another

Ion channels in synapses generate electric current

At rest, neurons are low in sodium, high in potassium

Neurotransmitters are the chemical signals with which neurons

communicate across a synapse• Neurotransmitters bind

to gated ion channels in the cell membrane of the next neuron

• Binding opens the ion channel

• Hydrolysis or reuptake removes the neurotransmitter

Many Drugs copy the action of neurotransmitters

• Methamphetamine is structurally similar to dopamine

• Dopamine involved in learning and reward systems

Dopamine

Methamphetamine

Some important neurotransmitters

• Acetylcholine- Neuromuscular

• Dopamine-Exitatory• Norepinephrine • GABA- Inhibitory• Serotonin-Regulatory

Which one of the following statements is false? A) Sensory neurons convey signals from the CNS to

sensory receptors. B) Motor neurons convey signals from the CNS to

effector cells. C) Interneurons integrate data and relay

appropriate signals to other interneurons or to motor neurons.

D) The PNS includes nerves and ganglia. E) The CNS consists of the brain and spinal cord.

• What is the functional unit of the nervous system?

• A) dendrite • B) cell body • C) neuron • D) axon • E) synapse

Neurons have a resting membrane potential

• Negatively charged• Keeps the neuron

poised for instant action• -70mV• Maintained by constant

active transport of ions•

When depolarized, neurons respond in milliseconds

• Depolarization is the activation event

• Depolarization is caused by opening of gated sodium channels

Nerve impulse Synopsis:1. Neuron at rest, -70mV

2. Opening of gated sodium channels depolarizes the cell

• Action potentials normally travel along an axon

• A) toward the cell body. • B) away from the cell body. • C) in either direction, depending on the needs

of the animal. • D) away from the synapse. • E) from axons into dendrites.

4-5. Potassium (K+) channels hyperpolarize the cell behind the

action potential

3.5: The impulse is propagated down the axon

• In between the Schwann cell ,myelin, Na+ channels open

• The action potential moves cown the cell rapidly

6. Depolarization at the axon terminal causes vesicle fusion with membrane • Vesicles contain

neurotransmitter• Neurotransmitter is

released into the synapse, stimulating the receiving neuron

• Stiumuls is terminated by ruptake or destruction of the neurotransmitter

0.5: Vesicles were marched down the axon previously by kinesin

Antidepressants can block reuptake of neurotransmitters

• SSRI- “Selective Serotonin Reuptake Inhibitors”

• Prozac, Paxil, Zoloft, etc.- all SSRI’s

Sarin nerve gas is an Acetylcholinesterase Inhibitor

• How does it work?• How does it kill people?

The reflex arc is the most basic neural circuit

The Ganglion splits the signal to notify the brain

What causes the signal that crosses a synapse to stop?

A) A second action potential traveling down the signaling cell sounds a sort of "retreat," and the ions reverse direction.

B) The responding cell runs out of sodium and is no longer able to respond to the stimulus.

C) The responding cell runs out of potassium and is no longer able to respond to the stimulus.

D) The chemically gated ion channels of the receiving cell's membrane can only transport for a short period of time before they close.

E) The neurotransmitter is broken down or transported back to the signaling cell.

• Once the threshold potential is reached • A) the membrane potential is positive. • B) K+ channels open. • C) Na+ channels close. • D) an action potential is inevitable. • E) None of the choices are correct.

The human brain has 3 major regions

Higher thought is compartmentalized to the cerebrum

Regions of the cerebral cortex are themselves compartmentalized

A homonculus shows the area of the brain devoted to regions of the body

• Which of the following statements about the sodium-potassium pump is false?

• A) It is a membrane protein. • B) It keeps the concentration of sodium low

inside the cell. • C) It moves sodium across the membrane and

into the cell. • D) It helps maintain the resting membrane

potential. • E) It actively transports potassium into the cell

• Which of the following neurotransmitters is associated neuromuscular junctions?

• A) acetylcholine • B) GABA • C) epinephrine • D) serotonin • E) endorphins