transmission within a neuron

Question 1

what is it meant by specialised cells?

Answer 1

cells are specialized according to their function

designed to carry out particular role in the body

Question 2

define diffusion

Answer 2

movement of particles from an area of high concentration to an area of low concentration

Question 3

what makes up the CNS?

Answer 3

brain and spinal cord

Question 4

what makes up the PNS?

Answer 4

all other nerves

Question 5

what is the role of sensory neurons?

Answer 5

carry information from body to interneurons

information includes:
light
sounds
smell

Question 6

what is the role of interneurons?

Answer 6

link the sensory neurons to the motor neurons

process information from sensory neuron

Question 7

what is the role of motor neurons?

Answer 7

carry information to the body from the CNS

important in controlling contraction of muscles

Question 8

how many neurons are there in the brain?

Answer 8

86 billion

Question 9

outline the structure of a (motor) neuron

Answer 9

• soma
• dendrites
• axon
• myelin sheath
• terminal buttons

Question 10

what is the soma of a neuron?

Answer 10

cell body

contains the nucleus of neuron

Question 11

what are dendrites?

Answer 11

• branches that connect to other neurons
• receive messages from neurons

Question 12

what are axons?

Answer 12

• these carry information along action potential
• from soma to terminal buttons

Question 13

what is the myelin sheath?

Answer 13

• wraps around the axon
• allows electrical impulses to transmit quickly and efficiently

Question 14

what are terminal buttons?

Answer 14

• at the end of axon branches
• responsible for sending the signal on to other neurons

Question 15

what are the two types of cells?

Answer 15

• neurons
• supporting cells (glia)

Question 16

identify types of glia

Answer 16

• astrocytes
• oligodendrocytes
• microglia

Question 17

explain the role of astrocytes

Answer 17

• provide structural support to neurons
• supply nutrients to neuron

Question 18

explain the role of oligodendrocytes

Answer 18

• produce myelin sheath
• this insulates axons

Question 19

explain the role of microglia

Answer 19

• smallest supporting cells
• important role in immune system of brain
• attacks foreign tissue

Question 20

identify features of the process of transmission within a neuron

Answer 20

• electrical process
• aim is to get message from soma down to terminal button
• involves the movement of ions across the cell membrane
• cells are more negative on the inside than on the outside
• this causes a resting potential

Question 21

describe the cell membrane

Answer 21

• made up of two layers of phospholipid molecules
• head of phospholipid is hydrophilic
• tail of phospholipid is hydrophobic
• contains an ion channel which spans the membrane
• ion channel allows ions to move in and out of cell

Question 22

what is the name of the fluid outside of the cell membrane?

Answer 22

extracellular fluid

Question 23

what is the name of the fluid inside of the cell membrane?

Answer 23

intracellular fluid

Question 24

what are ions?

Answer 24

charged molecules

Question 25

identify the two types of ions

Answer 25

cations anions

Question 26

what are cations?

Answer 26

positively charged ions

Question 27

what are anions?

Answer 27

negatively charged ions

Question 28

what molecules does intracellular fluid contain?

Answer 28

potassium (K+) anions (A-)

Question 29

what molecules does extracellular fluid contain?

Answer 29

sodium (Na+) chloride (Cl-)

Question 30

what is the membrane potential?

Answer 30

the difference in electrical potential inside and outside the cell

Question 31

how is the membrane potential balanced?

Answer 31

- diffusion - electrostatic pressure (attraction of particles that are opposite and repulsion of particles that are the same charge)

Question 32

explain how the membrane potential is balanced

Answer 32

ANIONS - anions are inside the cell and cannot leave - results in negative inside of cell POTASSIUM - potassium ions are more concentrated inside cell - potassium ions want to move out of cell membrane by diffusion - potassium is attracted to inside due to electrostatic pressure therefore forces balance and K+ doesn't move CHLORIDE - more concentrated outside cell - wants to move inside by diffusion - repelled from inside due to electrostatic pressure therefore doesn't move SODIUM - more concentrated outside the cell - wants to move in by diffusion - attracted to inside due to electrostatic pressure - both processes force Na+ into cell - kept under control by sodium-potassium pumps in cell membrane - 3 sodium ions pumped out and 2 potassium ions pumped in

Question 33

what is a resting potential?

Answer 33

the electrical potential difference across plasma membrane when in a non-excited state resting potential of neuron is =70 mV

Question 34

why is it important for resting potential to be maintained?

Answer 34

so that neuron can respond rapidly to stimulus

Question 35

what is an action potential?

Answer 35

a rapid change in membrane potential it is an 'all or nothing' process

Question 36

define depolarization

Answer 36

a decrease from normal resting potential (brings membrane closer to 0)

Question 37

define hyperpolarization

Answer 37

an increase relative to resting potential (more negative)

Question 38

describe the process of the action potential

Answer 38

- threshold of excitation met - voltage-gated sodium channels open - sodium enters - inside membrane becomes MORE positive than outside - voltage-gated potassium channels open - potassium leaves the cell - membrane potential reaches +40 mV - sodium channels become refractory and no more sodium enters - potassium continues to leave cell - membrane potential returns to resting level - potassium channels close and sodium channels reset - extra potassium outside cell diffuses away

Question 39

define propagation

Answer 39

- refers to the way the action potential is transmitted down an axon - action potential can only go in one direction - action potential doesn't move but rather causes new action potential

Question 40

define saltatory conduction

Answer 40

- refers to the way action potential is regenerated along the axon at nodes of Ranvier

Question 41

what are the benefits of saltatory conduction

Answer 41

fast conduction more energy efficient