Unit 1 - Nervous System (Structures and Processes)

Question 1

What is the purpose of the nervous system for the body?

Answer 1

Along with endocrine system, it coordinates action of the body and to maintain homeostasis.

Question 2

What is the nervous system made up of?

Answer 2

1) Brain
2) Spinal Cord
3) Nerves that come out (of spinal cord) that connects them to the rest of the body.

Question 3

What is the two major divisions of the nervous system?

Answer 3

1) Central Nervous System
2) Peripheral Nervous System

Question 4

Central Nervous System

Answer 4

Coordinates center for incoming and outgoing information.
–> Brain and Spinal Cord

Question 5

Peripheral Nervous System

Answer 5

Neurons coming out of spinal cord.
1) Sensory Pathways
2) Motor Pathways

Question 6

Somatic

Answer 6

Voluntary control (ex. skeletal muscles, bones, skin)

Question 7

Autonomic

Answer 7

Involuntary control (ex. internal organs and glands)

Question 8

Sympathetic

Answer 8

“Fight or Flight” –> Prepares body for stress

Question 9

Parasympathetic

Answer 9

“Rest and Digest” –> Returns body to normal resting levels after adjustments to stress

Question 10

Cells of Nervous System

Answer 10

1) Glial Cells
2) Neurons

Question 11

Sensory Pathways

Answer 11

Carry sensory information to Central Nervous System.

Question 12

Motor Pathways

Answer 12

Carry information from Central Nervous System to the rest of the body.

Question 13

Glial Cells

Answer 13

Non-conducting cells. They support structure and metabolism of nerve cells. They nourish neurons, remove their wastes, defend them against infection.

Question 14

Neurons

Answer 14

Functional unit of the nervous system. Hundreds if individual neurons group intro bundles to form nerves. They carry signals/impulses (from point A to point B).

Question 15

Types of Neurons

Answer 15

1) Sensory Neurons
2) Interneurons
3) Motor Neurons

Question 16

Sensory Neurons

Answer 16

Carries information to central nervous system.
–> Cell bodies are in clusters of ganglia located outside the spinal cord.

Question 17

Interneurons

Answer 17

Links sensory neuron to motor neuron.
–> Found only in the brain and spinal cord (central nervous system), tend to be shorter in comparison to motor and sensory neurons.

Question 18

Motor Neurons

Answer 18

Carries information out of Central Nervous System.
–> Delivers signal to effector (muscle, gland, tissue)
–> Cell body located in the spinal cord and axon projects outside the spinal cord

Question 19

(N) Dendrites

Answer 19

Receive information from either sensory neurons or motor neutrons and relay the nerve impulse towards the cell body.

Question 20

(N) Cell Body

Answer 20

Contains the nucleus.

Question 21

(N) Axon

Answer 21

Extension of the cytoplasm, projects from the cell body. Range in length from 1 mm to 1 m.
–>Carries nerve impulses to effector or other neurons.

Question 22

(N) Axon Terminal/ Synaptic Knob/ Synaptic Terminal

Answer 22

The expanded distal end of a neuron.
–>Passes signal to another neuron or effector.

Question 23

Myelin Sheath

Answer 23

Fatty white protein that covers some axons, insulator preventing the lost of charged ions, speeds up nerve transmission.

Question 24

Schwann Cells

Answer 24

A type of glial cell that forms the myelin sheath.

Question 25

Nodes of Ranvier

Answer 25

Area/gaps between the sections of myelin sheath.

Question 26

Neurilemma

Answer 26

A thin membrane produced by Schwann cells that promotes the regeneration of damaged axons.
–> Not all cells with a myelin sheath have a neurilemma. Therefore damage to the central nervous system is often permanent. (Which is why there are many other mechanisms to protect it.)

Question 27

White Matter

Answer 27

Nerves within the brain that have myelinated fibers.

Question 28

Grey Matter

Answer 28

Nerves within brain and spinal cord without a myelin sheath.

Question 29

Reflex Arcs

Answer 29

Simplest neutral pathways that occur within our bodies. Involves very few neurons therefore allow us to respond to particular (potentially dangerous) stimuli very rapidly. (50ms!)

Question 30

Reflex Arc Pathway

Answer 30

1) Stimulus
2) Sensory Receptor (detects the stimulus)
3) Sensory Neuron (starts a nerve impulse and transmits to Spinal Cord)
4) Interneuron (In Spinal Cord. Splits signal, one going to brain, one to motor neuron.)
5) Motor Neuron (carries nerve impulse to effector)
6) Effector (Muscle)
7) Response

(Response by the Effector occurs BEFORE brain receives and processes information.)

Question 30

Nerve Impulse

Answer 30

Neurons can have a voltage difference between the inside and outside of the cell membrane.
–> The difference in voltage can produce a nerve impulse
–> Conduction of an impulse depends on movement of ions across the cell membrane of an axon

Question 31

Polarization

Answer 31

-Negatively charged proteins that can’t get through membrane. –The membrane is impermeable to Cl- ions on the inside.
-Na+/K+ exchange pump (3Na+ out, 2K+ in, creates overall negative charge inside.) It uses ATP because it has to go against the concentration gradient.

Question 31

Resting Membrane Potential

Answer 31

When a neuron is at rest, the cytoplasmic side of the membrane (inside the neuron) is negative relative to the extracellular side (outside) which is positive.
–> The difference in charge forms a membrane potential (has potential energy)
–> Resting membrane potential = -70mV

Question 32

Sodium-Potassium Exchange Pump

Answer 32

–>3Na+ actively transported out of cell, 2K+ released into cell.
–> Na+ and K+ can diffuse through the cell membrane, but K+ diffuses out of the cell faster than Na+ diffuses into the cell, therefore -70mV is achieved.

At -70mV, there are no nerve impulses transmitted down the axon.

Question 33

Action Potential Steps

Answer 33

1) At Rest/Polarized: Maintained by Na+/K+ exchange pump. Inside is negatively charged compared to outside of membrane (-70 mV)
2) Depolarization: When threshold potential (-55 mV) is reached, voltage-gated Na+ channels open. Na+ rushes in and membrane potential increases until maximum depolarization.
3) Repolarization: Na+ channels close, voltage gated K+ channels open, K+ rushes out of cell. Membrane potential decreases past initial resting potential (-90mV)
4) Hyperpolarization: Na+ and K+ channels are closed which means Na+/K+ exchange pump restores resting membrane potential b taking 3Na+ out and 2K+ in.

Question 34

Action Potential Characteristics

Answer 34

-Action Potentials are ALL OR NOTHING!!
-During Repolarization and Hyperpolarization, the membrane cannot undergo another membrane potential (Refractory Period)
-Strength of AP cannot change, signal strength usually depends on frequency of AP or number of neurons stimulated.

Question 35

Nerve Impulse

Answer 35

–> A series of Action Potentials
–> When an Action Potential Occurs at a node of Ranvier, Na+ flow into the axon, then the Na+ pumps close, so Na+ must diffuse along the axon in both directions.
–> The node of Ranvier becomes depolarized by the increased positive charge inside the cell, and another AP begins

–> AP can’t travel backwards because previous node is in refracting period.
–>In myelinated cells, action potential jump over myelinated sheath: SALTATORY CONDUCTION.

Question 36

Synapse

Answer 36

Connection between two neurons / neuron and an effector.
–>As a nerve impulse travels down axon, eventually reaches axon/synaptic terminal.

Question 37

Synaptic Cleft

Answer 37

Gap between two cells at the synapse.
–>Nerve impulse jumps across synaptic cleft via neurotransmitters.

Question 38

Neurotransmitters Steps

Answer 38

1) AP arrives at the end of presynaptic neuron.
2) Vesicles containing neurotransmitters migrate to the terminal, fuse with cell membrane, release neurotransmitters into synaptic cleft (EXOCYTOSIS).
3) Neurotransmitters diffuse across cleft, bind to receptors on postsynaptic cell.
4) Neurotransmitters cause AP or prevent AP in postsynaptic cell by causing depolarization or hyperpolarization.

Question 39

Types of Neurotransmitters

Answer 39

1) Excitatory: cause Na+ channels to open, Na+ enters cell, causing depolarization (AP) eg. acetylcholine, epinephrine
2) Inhibitory: cause K+ channels to open, K+ leaves cell, causing hyperpolarization (no AP) eg. glycine, GABA

Question 40

Acetylcholine (Ach)

Answer 40

Excitatory, causes depolarization in postsynaptic cell.
–>After Ach has stimulated postsynaptic cell, it’s removed from the cleft by the enzyme acetylcholinesterase (Achase).
–>Achase binds to Ach & breaks it down.
–> Ach no longer available to bind to postsynaptic receptors, postsynaptic cell can now repolarize.

Question 41

Dopamine

Answer 41

–> Dopamine is neurotransmitter that has both excitatory and inhibitory effects, depending on the types of receptors are on the target.
–> Stimulates pleasure/reward centers of the brain, but inhibits movement.

Question 42

Summation ★

Answer 42

When postsynaptic neuron receives multiple signals (excitatory & inhibitory), cell body adds them together to decide if resulting signal is enough to reach threshold.