transmission within a neuron Flashcards
what is it meant by specialised cells?
cells are specialized according to their function
designed to carry out particular role in the body
define diffusion
movement of particles from an area of high concentration to an area of low concentration
what makes up the CNS?
brain and spinal cord
what makes up the PNS?
all other nerves
what is the role of sensory neurons?
carry information from body to interneurons
information includes:
light
sounds
smell
what is the role of interneurons?
link the sensory neurons to the motor neurons
process information from sensory neuron
what is the role of motor neurons?
carry information to the body from the CNS
important in controlling contraction of muscles
how many neurons are there in the brain?
86 billion
outline the structure of a (motor) neuron
- soma
- dendrites
- axon
- myelin sheath
- terminal buttons
what is the soma of a neuron?
cell body
contains the nucleus of neuron
what are dendrites?
- branches that connect to other neurons
- receive messages from neurons
what are axons?
- these carry information along action potential
- from soma to terminal buttons
what is the myelin sheath?
- wraps around the axon
- allows electrical impulses to transmit quickly and efficiently
what are terminal buttons?
- at the end of axon branches
- responsible for sending the signal on to other neurons
what are the two types of cells?
- neurons
- supporting cells (glia)
identify types of glia
- astrocytes
- oligodendrocytes
- microglia
explain the role of astrocytes
- provide structural support to neurons
- supply nutrients to neuron
explain the role of oligodendrocytes
- produce myelin sheath
- this insulates axons
explain the role of microglia
- smallest supporting cells
- important role in immune system of brain
- attacks foreign tissue
identify features of the process of transmission within a neuron
- 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
describe the cell membrane
- 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
what is the name of the fluid outside of the cell membrane?
extracellular fluid
what is the name of the fluid inside of the cell membrane?
intracellular fluid
what are ions?
charged molecules
identify the two types of ions
cations
anions
what are cations?
positively charged ions
what are anions?
negatively charged ions
what molecules does intracellular fluid contain?
potassium (K+)
anions (A-)
what molecules does extracellular fluid contain?
sodium (Na+)
chloride (Cl-)
what is the membrane potential?
the difference in electrical potential inside and outside the cell
how is the membrane potential balanced?
- diffusion
- electrostatic pressure
(attraction of particles that are opposite and repulsion of particles that are the same charge)
explain how the membrane potential is balanced
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
what is a resting potential?
the electrical potential difference across plasma membrane when in a non-excited state
resting potential of neuron is =70 mV
why is it important for resting potential to be maintained?
so that neuron can respond rapidly to stimulus
what is an action potential?
a rapid change in membrane potential
it is an ‘all or nothing’ process
define depolarization
a decrease from normal resting potential (brings membrane closer to 0)
define hyperpolarization
an increase relative to resting potential (more negative)
describe the process of the action potential
- 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
define propagation
- 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
define saltatory conduction
- refers to the way action potential is regenerated along the axon at nodes of Ranvier
what are the benefits of saltatory conduction
fast conduction
more energy efficient
