Coordination and regulation:nervous system 1

EXPECTED LEARNING

To explore the role of the nervous system in detecting and responding

The nervous system

This communication system controls and coordinates functions throughout the body and responds to internal and external stimuli.

Maintains homeostasis by detecting change and coordinating action of effector organs

Responsible for unidirectional, fast communication

brain

Spinal Cord

Cerebellum

Cerebrum

Medulla Oblongata

The Central Nervous System (CNS)

Consists of the brain and spinal cord

CerebrumCerebrum Voluntary or conscious activities of Voluntary or conscious activities of the body-learning, judgmentthe body-learning, judgment

CerebellumCerebellum Coordinates and balances the Coordinates and balances the actions of the musclesactions of the muscles

Medulla Oblongata Medulla Oblongata

(Brain Stem)(Brain Stem)

Controls involuntary actions like Controls involuntary actions like blood pressure, heart rate, blood pressure, heart rate, breathing, and swallowing breathing, and swallowing

Spinal CordSpinal Cord

The main communications link The main communications link between the brain and the rest of between the brain and the rest of

the bodythe body

The Central Nervous System (CNS)

Sheep brain dissection

Use the handout to dissect and label a sheeps brain

http://www.biologycorner.com/anatomy/sheepbrain/sheep_brain_dissection_guide.html

The peripheral nervous system (PNS)

Nerves extending out to the rest of the body from the CNS

Includes all sensory neurons, motor neurons, and sense organs

Nerve cells: Neurons

The basic functional unit of the nervous system.

Send impulses to and from the CNS and PNS and the effectors (muscles/glands)

Neuron structureStructure Description Function

Soma/cell body The control center of the neuron

Directs impulses from the dendrites to the axon

Nucleus Control centre of the soma

Tells soma what to do

Dendrites Highly branched extensions of the cell body

Receive and then carry information towards the cell body

Axon Extension of the cell body

Carries information away from the cell body

Myelin sheath Insulating layer around axon made of Schwann cells

Increases speed of impulse

Nodes of Ranvier

Gaps between Schwann cells.

Saltatory conduction – i.e. speed of an impulse is greatly increased by the message ‘jumping’ the gaps

Synapse Gap between axon or one neuron and dendrite of another

Communication between nerve cells

Types of Neurons

There are three basic kinds of neurons found in the nervous system, namely:

affector neurons, also known as sensory neurons

effector neurons, also known as motor neurons

connecting neurons, also known as interneurons

Types of Neurons – page 173

Types of Neurons

Type of neuron Description Function

Sensory Neurons located near receptor organs (skin, eyes, ears).

Receive incoming stimuli from the environment to CNS

Motor Neurons located near effector (muscles and glands)

Carry impulses from CNS to effectors to initiate a response

Interneurons Found most often in brain and spinal cord

Relay messages between other neurons such as sensory and motor neurons.

Fun Fact:

Where can the largest cells in the world be

found?

The giraffe’s sensory and motor neurons! Some must

bring impulses from the bottom of their legs to their spinal cord several meters

away!!http://www.dailymotion.com/video/xdm5he_richard-dawkins-demonstrates-laryng_tech/

Questions

Quick check qu 3&4, 12-15

Biochallenge qu 1

Chapter review qu 8&9

ReflectionStart to complete the nervous system concept map from

what you learnt today

Coordination and regulation:nervous system 2

EXPECTED LEARNING

To learn how signals are transported in the nervous system

Nerve impulses

Information is transferred in the form of an electrical impulse

The cell membrane of a nerve cell is polarised

i.e. there is a difference in charge between the inside and outside of the cell

Neuron at rest: Resting potential

A condition where the outside of the membrane is positively (+) charged compared to the inside which is negatively (-) charged.

Neuron is said to be polarized.

How is resting potential maintained?

Ion Distribution

Nerve impulses: Action potential

As an impulse moves along an axon, the permeability of the membrane changes

Positive sodium ions move into the neuron

Potassium ions move out of the neuron

The inside of the membrane is positively (+) charged compared to the outside which is negatively (-) charged.

This is called an ACTION POTENTIAL

Nerve impulses

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

http://www.youtube.com/watch?v=YP_P6bYvEjE&feature=relmfu

Activity

As a class, work out a way of demonstrating a neuron moving from resting potential to action potential

Neuron Communication: Synapses

A synapse is the junction between two nerve cells (e.g. axon bulb of one neuron and the dendrite or cell body of a second neuron).

A very small gap, called the synaptic cleft, lies between the two neurons.

Molecules called neurotransmitters relay messages across the synaptic cleft between the two neurons. The communication between neurons is chemical in nature.

Neuron Communication: Synapses

Neuron Communication: Synapses

Communication across the synapse involves:

Release of neurotransmitters (e.g. actylcholine) from secretory vesicles of presynaptic neuron

Exocytosis of neurotransmitter across the presynaptic membrane and release into the synaptic cleft

Attachment of transmitter to protein receptors on the postsynaptic membrane, opening protein channels, leading to stimulation of the neuron or effector cell

Deactivation of neurotransmitter by enzymes and reabsorption into presynaptic neuron

http://www.youtube.com/watch?v=LT3VKAr4roo

Reflex arc

An involuntary response that is processed in the spinal cord not the brain.

Reflexes protect the body before the brain knows what is going on

Reflex arc

Activity/Questions/Homework

Complete activity 6.1

Quick check questions 5-11, 16-18

Biochallenge qu 2&3

Quick check qu 3,6 & 7

ReflectionFinish the nervous system concept map using the

information you learnt today