Week 2 - The nervous systems: 2.1 Concept of the Synapse

Question 1

neurons - also called nerve cells

Answer 1

first and most basic way to describe behaviour at celullar level.

100 - 150 billion

do not regenerate once dead

Question 2

Neuron doctrine by Cajal

Answer 2

not continuous but contiguous - meaning the neurons are not part of each other, they are independant of each other, but communicate with each other

Question 3

Types of neurons

Answer 3

Over 200 different types of Neurons, in diff shapes and sizes 
but all have 
- a cell body 
- dendrites 
- an axon

Question 4

Classification of neurons by shape

Answer 4

• multipolar
• bipolar
• monopolar

Question 5

Classification of Neuron via function

Answer 5

• motor neurons
• sensory neurons
• interneurons

Question 6

Neuron via shape - multipolar

Answer 6

• has many dendrites, 1 x axon and located in the brain

Question 7

Neuron via shape - Bipolar

Answer 7

• has a single dendrite, single axon and is part of the sensory system

Question 8

Neuron via shape - Monopolar

Answer 8

• Single branch, 1 x input and 1 x output

Question 9

Neuron via function - Motor Neuron

Answer 9

• muscles & glands

Question 10

Neuron via function - Sensory Neuron

Answer 10

• respond to changes in the environment (light, smell etc)

Question 11

Neuron via function - interneurons

Answer 11

• are in the brain, and if the neuron is not a motor or sensory neuron then it is an interneuron

Question 12

Synapses

Answer 12

The point of communication between two neurons, the gap between.

Question 13

presynaptic neuron (bouton)

Answer 13

the neuron that delivers the transmission (prior)

Question 14

postsynaptic neuron

Answer 14

neuron that receives the transmission

Question 15

action potential produced by

Answer 15

the excitation threshold of the post synaptic neuron

- are always depolarizations

Question 16

graded potentials

Answer 16

may be depolarizations or hyperpolarizations

Question 17

Depolarizations are

Answer 17

Excitatory - becomes less negative (eg more positive)

Question 18

Hyperpolarizations are

Answer 18

Inhibitory - becomes more negative (eg less positive)

Question 19

Graded depolarisation is EPSP which is

Answer 19

Excitatory Postsynaptic Potential, this is a result from a flow of sodium ions into the neuron.

Question 20

Vertebrate Sensory Neuron - shape?

Answer 20

is a bipolar neuron

Question 21

Vertebrate motor neuron - shape

Answer 21

Multipolar neuron

Question 22

Synpatic Cleft

Answer 22

the gap between one neuron and another

Question 23

Axon points/description

Answer 23

• one per neuron
• myelin covering
• joins cell at the axon hillock
• extremely short to extremley long lengths

Question 24

Dendrites points/description

Answer 24

• many per neuron
• unmyelinated
• much shorter than axons

Question 25

Myelin - sheath coverings points/description

Answer 25

- affects speed of conduction of neural impulses - Within the CNS (oligodendrocytes - a type of glial cell) - Outside of the CNS (Schwann Cells - a type of Gilal cell) - Nodes of Ranvier

Question 26

Types of Glia cells

Answer 26

Astrocytes Oligodendrocytes Schwann Cells Radial glia - all can be regenerated - a 10:1 ratio of glia cells to neurons exist in the brain

Question 27

Temporal Summation

Answer 27

summation over time, - repeated stimuli within a brief time have a cumulative effcet eg one light pinch vs rapid repeated pinches. the single pinch does not reach the threshold of excitation for the next neuron.

Question 28

EPSP stands for

Answer 28

EXCITatory POSTsynaptic POTENTIAL - a graded depolarization It results from a flow of sodium ions into the neuron. It is a graded potential

Question 29

Spatial Summation

Answer 29

summation over space ( a property of the synapse) Synaptic inputs from seperate locations combine their effects on a neuron. eg pinching two seperate points. critical to brain functioning - sensory input at a single synapse produces a weak effect - if multiple messages are received from many axons, this excites the neuron enough to activate it (action potential)

Question 30

IPSP stands for

Answer 30

Inhibitory Postsynaptic Potential, meaning the temporary hyperpolarization of a membrane. Occurs when synaptic input opens the gates for potassium ions to leaqve the cell (carrying a positive charge) or for chloride ions to enter the cell - which carry a negative charge. inhibiting an impulse Hyperpolarization = Inhibitory it is a graded potential

Question 31

What Ion gates in the membrane open during an EPSP (Excitatory PostSynaptic Potential)

Answer 31

Sodium Gates open

Question 32

What Ion gates in the membrane open during an IPSP (Inhibitory PostSynaptic Potential)

Answer 32

Potassium or Chloride Gates open

Question 33

What is spontaneous firing rate

Answer 33

Something most neurons have - which is a periodic production of action potentials even without synaptic input.

Question 34

What is the reflex arc

Answer 34

the circuit from sensory neuron to muscle response is

Question 35

What does it mean by reflexes

Answer 35

automatic muscular responses to stimuli.