Organisation & Function Of The Nervous System

Front 1

State and explain the 3 basic functions of the nervous system.

Back 1

1. Sensory Input - NS collects info from millions of receptors which detect changes within and outside the body.

2. Integration - NS interprets and integrates the sensory info (inputs), makes decisions and sends instructions to alter tissue/organ behavior appropriately.

3. Motor output - effector organs respond to instructions.

Front 2

What higher functions is the brain responsible for?

Back 2

- Cognition

- Learning

- Formation/storage and recall of memories

- Emotions

-Control of PNS function

Front 3

Describe the formation of the NS - neuroectoderm and the neural crest.

Back 3

1. The NS is formed during embryonic development.

2. Rapid proliferation of the conceptus results in the formation of a flat sheet of cells.

3. NS is formed as the blastocyst transforms into a gastrula.

Front 4

State the complex organs included in The Central Nervous System, what they are made up of and what they do.

Back 4

-The CNS includes the brain and spinal cord which are complex organs consisting of neural tissue, blood vessels and protective connective tissue.

- These organs interpret and integrate different types of sensory info and initiate appropriate motor commands in response to sensory input.

Front 5

State what the Peripheral Nervous System is made up of, what it does and include examples.

Back 5

It contains all neural tissue outside of the CNS including different types of neuronal populations such as the Dorsal Root Ganglia and it also contains nerves which extend from these neuronal populations near the brain (cranial nerves) and spinal cord (spinal nerves).

Nerves carry sensory info to the CNS and convey motor commands to peripheral (effector) tissue such as skeletal muscle.

Front 6

Explain what the afferent and the efferent divisions of the PNS are.

Back 6

- The afferent division carries sensory info from receptors in the body to constantly inform the CNS of changes in the external and internal environment.

- The efferent division enables the CNS to adjust the activity of the effector organs in response to changes in the external or internal environment to maintain homeostasis.

Front 7

State the 2 sub-divisions of the efferent division and what they do.

Back 7

- Somatic Nervous System (SNS) which is comprised of somatic nerve fibres which carry impulses from the CNS to the skeletal muscle (under voluntary control, degenerates in motor neuron disease).

- Autonomic Nervous System (ANS) which consists of neurons which control the function of internal structures such as sweat glands or organs such as the heart (involuntary control).

Front 8

State the functional divisions of the ANS and what they do.

Back 8

- Sympathetic Nervous System; primary process to stimulate the body's 'fight or flight' response.

- Parasympathetic Nervous System; responsible for the stimulation of 'rest and digest' or 'feed and breed'.

- Enteric Nervous Systsem; mesh-like system of neurons that governs the function f the gastrointestinal system. It is derived from neural crest cells.

Front 9

State the 2 types of cells which the NS is built up from and their numbers.

Back 9

- Neurons (about 10 billion in the human brain)

- Glia cells (up to 50 times more of these cells than neurons in the CNS)

Front 10

Characteristics of neurons.

Back 10

- Neurones are the basic structural and functional unit of the nervous system.

- Highly specialized excitable cells that transmit info in the form of electrical impulses (APs) rapidly from one part of the body to another.

- With the exception of the hippocampus and olfactory epithelium, neurons cannot be replaced once lost from the NS.

- They show remarkable longevity. They can function optimally over a lifetime (>100 yrs).

- They have extremely high metabolic rates (die within minutes without O2).

Front 11

What occurs during a stroke?

Back 11

Oxygen deprivation causes motor neuron death in the brain cortex, hence limb paralysis as seen in stroke patients.

Front 12

Describe the general structure of a neuron.

Back 12

A typical neuron has 4 morphologically distinct part:

1.Neuronal cell body (perikaryon or soma)

2.Dendrites

3.Axons

4.Presynaptic terminal

- The cell body contains the usual complement of organelles except centrioles, hence why neurons cannot replicate.

- They have highly developed clusters of RER and ribosomes, termed Nissl bodies, which synthesize the cells proteins and membrane components.

- During embryonic development, outgrowth of axons occurs at specific points on the cell body.

- In the CNS, most neuron cell bodies are located in the nuclei e.g. the Dorsal-Motor nucleus.

- The cell body and processes are supported by a cytoskeleton comprised of: Actin filaments (microfilaments), Neurofilament proteins (3 types) and microtubules which regulate axon growth during development and also provide a track for axonal transport.

Front 13

State the functions of axonal transport

Back 13

- Recycling materials

- Movement of organelles and substances e.g. mitochondria

- Conveys materials from axon to cell body

- Transfers info of axonal status + terminal environment; anterograde & retrogradev (both directions)

Front 14

Describe and state the functions of:

a. Dendrites and b. Axons

Back 14

a. Short, thin, slender. Info is received here from other neurons.

b.Each neuron has one axon, a tubular process, that generates and transmits nerve impulses. Diameters range from 0.2-20um. Axons can be extremely long e.g. motor neurons.

Front 15

State how neurotransmission occurs.

Back 15

In one direction only, away from the cell body towards the axon presynaptic terminal.

Front 16

How are neurons classified?

Back 16

They are generally classified according to structure or function:

-Structural Classification: 3 major groups of neurons are classified according to the number of processes (axons, dendrites) extended from the cell body.

-Functional Classification: where neurons are identified by their functions.

Front 17

Explain hat unipolar, bipolar and multipolar means in terms of neurons.

Back 17

-Unipolar: Initially bipolar, but during development the two processes converge and form a single short process that extends from the cell body.

-Bipolar: Neurons have 2 processes, axon and dendrite extending from opposite sides of the cell body (rare, found only in some special sense organs e.g. retina - the thin layer of tissue lining the inner surface of the eye)

-Multipolar: 3 or more processes that extend from the cell bodies (99% of neurons in humans are multipolar).

Front 18

State the 3 types of neurons.

Back 18

-Sensory neurons

-Motor neurons

-Interneurons

Front 19

Sensory neurons:

-What do they form?

-What do they do?

-Where are they located?

-What type of polar?

-Where do the fibres extend between?

Back 19

-The Afferent division of the PNS

-They transmit info (impulses) from sensory receptors in the skin and viscera to the CNS

-The cell bodies of the neurons are located in the peripheral ganglia e.g. Dorsal Root Ganglia (located outside the brain or spinal cord)

-Typically unipolar

-Between a sensory receptor and the CNS

Front 20

Interneurons:

- How many?

- Where are they located?

- What do they do

-What are they involved in?

-What are they responsible for?

-What do they coordinate?

Back 20

- Approx 20 billion in human CNS

- Spinal cord and brain

- They connect the sensory neurons (afferent) with the motor neurones (efferent).

-They are responsible for interpreting and integrating sensory info from the periphery.

-They coordinate motor activity

-Are involved in all higher functions such as the laying down of memory and cognition

Front 21

Motor Neurones:

-What do they form?

-What do they do?

Back 21

- They form the efferent division of the PNS

- They convey impulses from the CNS to peripheral effectors, muscle, glands and individual cells.

Front 22

State the types of Neuroglia (glial cells) in:

a. CNS and b.PNS

Back 22

a. In the CNS there are 4 types; astrocytes, oligodendrocytes, microglia and ependymal cells.

b. In the PNS there are 2 types: Schwann cells and satellite cells.

Front 23

State the functions of glial cells.

Back 23

-Generally they provide support for neurons

-Astrocytes have numerous processes that cling to neurons and synapses, thus holding them in place.

-Control chemical environments around the neurons e.g. clearance of glutamate neurotransmitters by astrocytes in the CNS.