Lecture 15 - Cells and organisation of the nervous system

Question 1

Integrating and coordinating …meaning for our nervous system?

Answer 1

The nervous system senses the environment and then produces the appropriate response. It matches the sensory environment with our bodies needs

Question 2

Maintaining homeostasis - integration, coordination and response

Answer 2

Integration often happens with you knowing it for example am I hungry? Do I want that kind of food?

Coordination e.g. preparation for eating, craving another type of food

Response e.g. order some food, go for Indian instead or walk away

Question 3

Central nervous system

Answer 3

Central Nervous System (CNS) consist of the brain and spinal cord and is made out of neurons and glia

Question 4

2 general cell classes that make up the CNS

Answer 4

Neurons

Glia

Question 5

2 general cell classes that make up the PNS

Answer 5

Neurons

Glia

Question 6

Peripheral nervous system (including the ENS)

Answer 6

Peripheral Nervous System (PNS) consists of the peripheral nerves (that come out of the brain and the spinal cord) and are made out of neurons and glia

Question 7

CNS

Answer 7

Central nervous system

Question 8

PNS

Answer 8

Peripheral nervous system

Question 9

Neurons

Answer 9

The basic nerve cell of the nervous system containing a nucleus within a cell body and extending one or more processes. Nerve cells conduct information along the lengths of these processes.

Different shapes and sizes because they have different functions

These cells are specialised for transmission of information and there are 4 morphological types

Question 10

Glia

Answer 10

Glia are non-neuronal cells in the CNS and PNS that do not produce electrical impulses. They maintain homeostasis, form myelin, and provide support and protection for neurons.

These are the support cells for neurons

There are 5 basic types - 4 in the CNS and 1 in the PNS. Each type has a special function

Question 11

Structural components of a neuron

Answer 11

Dendrites - receive input and send info to the cell body
Cell body - contains nucleus and organelles and sums input (collects the input from the dendrites)
Axon (long structure that extends from the cell body) - carries electrical impulses (it carries information by transfusing electrical impulses) and may or may not be myelinated
Axon terminal(s) - Ends of the axon and this is where neurotransmitter release occurs (this is the last point where the signal goes)

Question 12

In the CNS a group of cell bodies is called

Answer 12

Nucleus (plural is nuclei)

Question 13

In the CNS a bundle of axons is called

Answer 13

Tract

Question 14

In the CNS a group of cell bodies in the cerebral cortex or spinal cord is called

Answer 14

grey matter

Question 15

In the CNS a bundle of axons in the cerebral cortex or spinal cord is called

Answer 15

White matter

Question 16

In the PNS a group of cell bodies is called

Answer 16

Ganglion (plural is ganglia)

Question 17

In the PNS a bundle of axons is called

Answer 17

Nerve

Question 18

Functional components of a neuron

Answer 18

Input zone - composed of the dendrites and the cell body. Receives chemical signals from other neurons (receives neurotransmitters being released by other neurons)

Summation zone - axon hillock. Decision to transmit signal further is made here

Conduction zone - Signal is tranmitted along the axon, may be quite long, if the decision is made at the axon hillock that the signal should be transmitted further. Carry electrical signals between brain areas, to and from spinal cord, or to and from peripheral sensory receptors (an axon’s job is to conduct an electrical signal down its length)

Output zone - axon terminals. Contact with input zone of other neurons (can connect with other neurons or effector cells). Release of neurotransmitter = chemical signal

Question 19

Axon hillock

Answer 19

The axon hillock is a specialised part of the cell body of a neuron that connects to the axon. It is here where the decision is made about whether to pass on the information

The axon hillock is where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon.

Question 20

What is a process?

Answer 20

Refers to any projection from the cell body of a neuron

Question 21

Multipolar neuron

Answer 21

Multiple processes emanate from the cell body (has an obvious axon and the rest of the processes are dendrites)

Question 22

Bipolar neuron

Answer 22

Two processes emanate from the cell body (one dendrite and one axon)

Question 23

Unipolar neuron

Answer 23

One process emanates from the cells body, then branches into dendrite and axon

Question 24

Anaxonic neuron

Answer 24

No distinct axon, all process look alike

Question 25

4 morphological types of neurons

Answer 25

Multipolar, bipolar, unipolar and anaxonic neurons

Question 26

CNS glia cell names

Answer 26

Astrocytes, microglia, ependymal cells and oligodendrocytes

Question 27

Astrocytes

Answer 27

Starshaped cell and they are the most abundant glial cells in the brain
Supply nutrients to neurons
Ensheath blood capillaries
Transmit information

Question 28

Microglia

Answer 28

Immune cells of the CNS

Engulf microorganisms and debris

Question 29

Ependymal cells

Answer 29

Line fluid filled space of the brain and spinal cord 
Have cilia (hair like processes) to circulated cerebrospinal fluid (the cilia wave which causes the CSF to circulate in a particular direction)

Question 30

Oligodendrocytes

Answer 30

Support nerve fibres

Ensheath them with myelin (myelinates the axons)

Question 31

PNS glia

Answer 31

Schwann cells

Support peripheral nerve fibres
Ensheath them with myelin (axon of the neuron is wrapped in Schwann cells which wrap their plasma membranes around the axon)
Similar to oligodendrocytes in the CNS

Question 32

Myelin sheath

Answer 32

Fatty covering/ Lipid (fat wrapped around an axon

CNS comes from oligodendrocytes and in the PNS comes from Schwann cells

The myelin sheath increases conduction velocity (increases the velocity of the conduction of n electrical signal down an axon)

Question 33

Where does the myelin sheath come from in the CNS?

Answer 33

oligodendrocytes

Question 34

Where does the myelin sheath come from in the PNS?

Answer 34

Schwann cells

Question 35

Nodes of ranvier

Answer 35

These are gaps between myelin

Increase conduction

Question 36

Synapse

Answer 36

Communication between neurons occurs through a junction called a synapse

Junction between the cell sending the signal (axon terminal) and the cell that is receiving the signal (dendrites)

Chemical signal occurs in the synapse to bridge the gap between electrical signals

Question 37

Simplified synapse process of transmitting a nerve impulse

Answer 37

Steps involved….

Nerve impulse depolarises terminal

Voltage gated Ca2+ channels open

Ca2+ influx causes vesicles to bind to the membrane and release neurotransmitter across the synaptic cleft

Neurotransmitter binds to the post synaptic receptors which open and depolarisation occurs

Nerve impulse is transmitted

Question 38

How does the presynaptic neuron communicate with the post-synaptic neuron ?

Answer 38

The presynaptic neuron is before the synapse and is the neuron that is passing on the information. It contains synaptic vesicles, which are little packets that contain vesicles). This neuron releases neurotransmitters (chemical signal) from the axon terminal

These neurotransmitters go across the synaptic cleft and to the post-synaptic neuron.

The post-synaptic neuron is after the synapse and it is the neuron that is receiving the signal. This neuron contains receptors for the neurotransmitters

Question 39

Afferent

Answer 39

Information that does into the brain
Sometimes known as ascending
e.g. sensing something in the environment

Question 40

Efferent

Answer 40

Response that comes out of the brain
Sometimes known as descending
E.g. responding with an appropriate action