Chapter 14 Coordination (part 1)

Cambridge IGCSE Biology 0610 Syllabus

Focus on Coordination and Response (Topic 14).
Core Topics:
- Electrical impulses travel along neurones.
- Mammalian nervous system:
- Central Nervous System (CNS): Brain and spinal cord.
- Peripheral Nervous System (PNS): Nerves outside the brain and spinal cord.
- Nervous system's role in coordination and regulation of body functions.
- Identify sensory, relay, and motor neurones in diagrams.
- Simple reflex arc: receptor, sensory neurone, relay neurone, motor neurone, and effector.
Supplement Topics:
- Reflex action: integrates and coordinates stimuli with effectors (muscles and glands).
- Synapse: junction between two neurones.
- Synapse structure: vesicles, synaptic gap, receptor proteins.
- Events at a synapse:
- Impulse stimulates neurotransmitter release into the synaptic gap.
- Neurotransmitter molecules diffuse across the gap.
- Neurotransmitter molecules bind with receptor proteins on the next neurone.
- An impulse is stimulated in the next neurone.
- Synapses ensure impulses travel in one direction only.

Coordination

Coordination: Organs and systems work together efficiently.
Animals and plants respond to stimuli.
Achieved through the nervous and endocrine systems.

Mammalian Nervous System

Central Nervous System (CNS): Brain and spinal cord.
Peripheral Nervous System (PNS): Nerves outside the brain and spinal cord.

Central Nervous System (CNS)

Brain
Spinal cord

Peripheral Nervous System (PNS)

Cranial nerves
Spinal nerves
Sensory organs

Nerves

Cranial Nerves

Olfactory nerve (CNI)
Optic nerve (CNII)
Oculomotor nerve (CNIII)
Trochlear nerve (CNIV)
Trigeminal nerve (CNV)
Abducens nerve (CNVI)
Facial nerve (CNVII)
Vestibulocochlear nerve (CNVIII)
Glossopharyngeal nerve (CNIX)
Vagus nerve (CNX)
Accessory nerve (CNXI)
Hypoglossal nerve (CNXII)

Spinal Nerves

Cervical
Thoracic
Lumbar
Sacral

Spinal Cord Structure

Long tube of nervous tissue
Brain stem
Spinal cord
Vertebra
Cauda equina
Disk
Sensory (posterior) root
Motor (anterior) root
Spinal nerve

Role of the Nervous System

Coordination and regulation of body functions
Sensitivity to internal and external environment
Coordinate response

Nervous Control

Information as nerve impulses.
Nerve impulses are electrical impulses along neurones.
Millions of neurones.

Neurones (Nerve Cells)

Adapted to carry electrical impulses.
Act as a wire.
A bundle of neurones is called a nerve.

Structure of a Neuron

Dendrites
Cell body
Axon
Myelin sheath
Schwann cell
Synaptic knob

Neuron Structure

Dendron: Receives information.
Dendrites: Branches of a dendron.
Schwann cells: Form myelin sheath.
Myelin sheath: Insulates the neuron.

Nerve Impulses

Messages are sent through nerve impulses.

Nerve

A bundle of neurones.

Types of Neurones

Sensory Neurone

Cell body is near the end.
Dendrites are present at the end.
No axon/very short
Long dendron

Motor Neurone

Cell body is at the start.
Dendrites are attached to cell body.
Motor end plates are at the end.
Long axon
No dendron.

Neurone Structure Review

Feature	Sensory Neurone	Motor Neurone
Cell body	Near end, in a ganglion	At start, inside spinal cord
Dendrites	Present at end	Attached to cell body
Axon	Very short	Very long
Dendron	Very long	None

Neurone Types

A. Sensory neuron
B. Interneuron (Relay)
C. Motor Neuron

Receptor

Protein molecule in a cell to which a substance can bind, causing a change in the activity of that particular cell.
Detect a change in the environment and stimulate electrical impulses in response.
Sense organs contain groups of receptors that respond to specific stimuli.
Electrical impulse passed on to a sensory neurone to the central nervous system, triggering a response via motor neurone to the effector.

Receptor location

Cell membrane or cytoplasmic receptor proteins
Central receptors
Peripheral receptors

Receptor examples:

Eyes (vision)
Ears (hearing, equilibrium)
Nose (smell)
Tongue (taste)

Receptor detection

Chemoreceptor (pH, gases, chemicals)
Osmoreceptor (osmolarity)
Thermoreceptor (temperature)
Baroreceptor (pressure)
Proprioceptor (body position)
Other mechanoreceptors (pain, vibration, touch)

Sense Organ Receptors

Vision: Rod, Cone
Hearing
Smell
Taste
Touch: Free nerve ending, Meissner corpuscle

Effectors

Muscles or glands that respond to impulses from motor neurones.
Examples: muscle contracting, gland releasing a hormone.

Glands

A group of cells that excretes a chemical substance: hormones, sweat, saliva, mucus, or acids (HCl).
Two main glands:
- Endocrine glands: release hormone directly into the bloodstream.
- Exocrine gland: release substance through a duct.

Endocrine System

Pituitary gland
Thyroid gland
Parathyroid gland
Pancreas
Adrenal gland
Ovary in woman
Testicle in man

Gland difference

	Exocrine (Glands with Duct system)	Endocrine (Ductless glands)
Release of	Secretion	Secretion

Response

The way an organism reacts after a stimulus is detected.

Neurones Function

Sensory neurones: receptor to the CNS
Relay neurone: connector inside the CNS
Motor neurones: CNS to effectors

Neurone Impulse

Sensory Neurone: carries nerve impulse to the spinal cord
Connecting (relay) neurone: carries impulse from the sensory to the motor neurone
Motor Neurone: carries impulses from the spinal cord to the muscle

Relay Neurones

Order of neurones

Review: Functions of Neurons

NEURON TYPE	FUNCTION
Sensory	Bring impulses from the sense organs or receptors into the CNS
Relay (Interneuron)	Receive impulses from sensory neurones and relay them to motor neurones
Motor	Carry impulses from the CNS to the effector organs

Review: Relay Neurones

Relay neurones connect sensory neurones to motor neurones in the spinal cord.

Review: Control Systems

Include:
1. Receptors detect stimuli
2. Coordination centre processes information
3. Effectors bring about responses
Effectors include muscles and glands.

Review: Receptors and Effectors

	Receptors	Effectors
Main point	Detect the stimulus	Produce the response
Where	Present in the sense organs	Present in any part of the body
Control	Send information to the control centre	Follow commands of central control
How	Follow the stimulus	Connected to the motor neurone

Review: Simple Reflex Arc

Reflect action

Types of Action

Voluntary & Involuntary action

Voluntary Action

A conscious decision (awareness)
Involves brain - walking, running, smiling

Involuntary (or Reflex) Action

Does not involve the brain
Essential to basic survival (knee jerk, heart beat, breathing, peristalsis)
Rapid

Spinal Reflex Arc

Brain involved at all

Reflex Actions

Automatically, rapidly integrates and coordinates a stimuli with effectors.
Mediated by the spinal cord and peripheral nerves, without conscious control.
They are quick because there is a direct link in the CNS between the sensory and motor nerves.
To minimize damage to the body
Involuntary/sudden action/spontaneous

Review: Reflex Action

Signa

Reflex Action Explanation

A reflex action follows pathway and does not involve the conscious part of the brain, which makes it much quicker.

Simple Reflex Arc

A reflex arc describes the nerve PATHWAY of a nerve impulse in response to a stimulus followed by reflex action.

Review: Impulse Pathway

Stimulus is detected by receptor sensory cell.
Passes down sensory neurone.
Passes impulse to relay neuron.
Motor neurone passes impulse to effector cells, e.g. muscle or gland.

Review: Defining Reflex Action

The nerve pathway followed by a reflex action is called a reflex arc.
This creates an automatic and rapid response to a stimulus, which minimises any damage to the body.

Rapid Reflex Summary

The nerve pathway followed by a reflex action is reflex arc.
This creates an automatic and rapid response to a stimulus.

Review: Comparing Voluntary and Involuntary Actions

Feature	Voluntary Action	Involuntary Action
Thinking	Requires thinking	Takes place without thinking
Speed	Slower	Faster
Control	Controlled mainly by the brain	Controlled mainly by the spinal cord
Purpose	For everyday actions	Usually life saving actions

Synapse

Synapse Function

Neurones do not connect directly; there is a gap called a synapse.
Synapses control that impulses only travel one direction.
Avoid confusion within nervous system
Slow down the speed of nerve impulses slightly
Messages are chemical (not electrical).
Many drugs act upon synapses.

Synapse Neurone Components

X neurone location

Synapse Diagram

the \"gap\"
PRE-synaptic neuron
POST-synaptic neuron

Synapse Action Potential

Presynaptic axon terminal
Synaptic cleft
Postsynaptic dendrite

Synapse Structure

Presence of vesicles, synaptic gap, receptor proteins.

Synapse Structure Components

Sending neurone
Receiving neuron
Electrical Impulse
Neurotransmitter
Post-Synaptic Neuron
Pre-Synaptic Neuron
Synaptic vesicles
Receptor
Synaptic gap/cleft

Synaptic Gap

Space between the axon of one neurone and the dendrites of another
Where electrical impulses translate to chemical transmission
Synaptic cleft - Gap at the junction where two neurons meet

Synapse Membrane

Presynaptic neuron
Terminal
Vesicle
Mitochondrion
Postsynaptic membrane containing receptors
Postsynaptic neuron
Released neurotransmitter molecules
Approaching nerve impulse

Impulse Synapse Transmission

Chemical called acetylcholine- neurotransmitters

Synaptic Transmission

Presynaptic neuron

Axon terminal
Neurotransmitter
Nerve impulse
Postsynaptic neuron
Neurotransmitter receptor
Nerve impulse
Synaptic gap

Electric Impulse in Synapse Transmission

Electrical impulse travels along an axon.
Neurotransmitters released into synaptic gap.
Neurotransmitter diffuses across the synaptic gap
Neurotranmitter molecules bind with receptor protein in the post synaptic membrane neurone
Stimulates the post synaptic neurone to transmit the electrical impulses.
Impulse Continue to the axon
Neurotransmitters are then recycled /destroyed

Neurotransmitter Travel review

Impulse Arrives
Vesicles move toward end of neuron
Neurotransmitters releasing/attaching toward Receptors
Synaptic Cleft triggered by an impulse.

Electric Signal review

Action potential at axon terminal
Messenger Transfer from Electric-Chemical
Chemical Messenger converts by synapse

Sense Organ

Missing part one

Sense Organs

Receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
Structures of the eye: cornea, iris, pupil, lens, retina, optic nerve and blind spot
Function of each part of the eye:
- (a) cornea-refracts light
- (b) iris-controls light entering the pupil
- (c) lens - focuses light on to the retina
- (d) retina- contains light receptors
- (e) optic nerve-carries impulses to the brain
Pupil reflex, changes in light intensity and pupil diameter
Pupil reflex: antagonistic action of circular and radial muscles in the iris
Accommodation to view near and distant objects: ciliary muscles, suspensory ligaments, shape of the lens and refraction of light
Distribution of rods and cones in the retina
Function of rods and cones:
- (a) greater sensitivity of rods for night vision
- (b) cones absorb light of different colours for colour vision

Identify position of the fovea

Sense Organ Groups

Receptor cells responding to stimuli.
Linked to the peripheral nervous system.
Generate an electrical impulse which passes along peripheral nerves to the CNS, triggering a response.

The Eye

Receptor cells sensitive to light (rod cells) and colour (cone cells)

Eye structure

cornea, iris, pupil, lens, retina, optic nerve, ciliary muscles, suspensory ligaments and blind spot, fovea.

Eye Function

Cornea: refracts light into the eye.
Iris: Amount of light entering the eye.

Eye Functions Continued

Lens: Focus light onto the retina.
Pupil: Hole that allows light to enter.
Ciliary body: Muscle attached to the lens with suspensory ligaments.

Eye Function Detail

Retina: Photoreceptor(light receptor cells): rods and cones.
Optic nerve: Transmits nerve impulses from retina to the brain
Fovea: High concentration of cones(colour cells).
Blind spot: Where optic nerve leaves/connects to retina.

Reflex Review

1. refracts light
2. controls light
3. focuses light onto retina
4. contains light receptors
5. carries impulses to the brain

How Eyes Work

Light rays to the cornea - refracts (bends) light - Light passes through the pupils- The lens refracts light further to focus it onto the fovea(retina) - Fovea contains light receptors and electrical impulses to optic nerve to the brain- The brain interprets these impulses and gives us what we call ‘vision’

Pupil Reflex Summary

Rapid unconscious response to change in light intensity
Changes the pupil diameter(size).
Control light intensity.
Reflex action.

Eye Muscle types

Circular muscles and radial muscles.
Antagonistic

Pupil Reflex Explanation

In bright light:

The photoreceptor detect changes (high light intensity)
The radial muscles relax
The circular muscles contract
Pupil constricted-------reduce, narrow
Less light can enter the eye.

Low Light Reflex

In low light

The photoreceptor detect changes (dark)
Radial muscles contract
The circular muscles relax,
Pupil dilates, widen
More light can enter the eye.

Pupil Reflex Pathway

Intensity of light hitting-photoreceptors
Impulse transmit along sensory neurone -muscles of the iris-contracs or relax
Triggering a response

Review: Muscle Light Bright situation

Circular muscles = 1
Radial muscles = 2
Pupil 3- or becomes smaller
4 light

Fill in Muscle Light Diagram

	Radial Muscles	Circular Muscles	Pupil Size	Amount of Light
Dark light	Contracted	relaxed	Wide	More
Bright light	Relaxed	Contracted	Narrow	Less

Lens Focus

Accommodation

Ability of the eyes to change focus from far distant to near objects and vice versa
It is how the lens changes shape in order to fine focus the light directly onto the fovea(retina).

Details

The shape of the lens needed to accommodate the image is controlled by:

The ciliary body
Ciliary muscle) Change the shape of the lens so the eyes can focus.
Suspensory ligament- attaches ciliary muscle to the lens

Accommodation Details

Distant and Incoming Light Comparison

Distant objects

Incoming light is parallel
The ciliary muscles relax
Pulls on the suspensory ligaments
Pull on the lens
Lens thinner
Light refracted less
Focus on distant object