Coordination & Responses

Chapter 13.1: The Nervous System

Prepared By, Mrs Yap-Wong Fui Yen 2014Prepared By, Mrs Yap-Wong Fui Yen 2014

Learning Outcomes: state the relationship between receptors, the

central nervous system and the effectors.

state that the nervous system - brain, spinal cord and nerves, serves to co-ordinate and regulate bodily functions.

outline the functions of sensory neurons, relay neurones and motor neurons.

discuss the function of the brain and spinal cord in producing a co-ordinated response as a result of a specific stimulus in a reflex action.

13.1

Prepared By, Ms Wong

What do these celebrities have in common?

Muhammad Ali & Michael J.Fox suffered from Parkinson’s disease, which affected their CNS

Christopher Reeve suffered from spinal cord injury when he fell off from a horse.

13.1

NERVOUS SYSTEM

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

Cranial Nerves(from brain)

Spinal nerves(from spinal cord)

Sense organs with receptors

( receive stimuli)Brain Spinal Cord

13.1

Prepared By, Ms Wong

Terms: Functions:Central Nervous System Consists of the brain and the spinal cord. Stimulus : A sudden change in the environment.

Receptor : Sense organ which receive stimulus and produce nerve

impulses to be transmitted to the CNS.

Nerve impulse : Electrical messages transmitted by nerves.

Types of neurones

(a) Sensory neurone (b) Relay(intermediate) neurone

(c) Motor neurone

: Transmits nerve impulses from receptor to CNS

: Transmits nerve impulses from sensory neurons to the motor neurons across junctions called synapse

: Transmits nerve impulses from CNS to effector

Effector : The effect of a response (e.g muscles , glands)

Reflex action : Immediate response to a specific stimulus without conscious control

13.1

What is “receptor”?

Sudden changes in the environment is known as stimulus.

Sense organs (e.g eyes, nose, skin) has receptors sensitive to particular kinds of stimulus.

Receptors help to detect the stimulus and turn them into nerve impulses.

13.1

Sense organs with receptors to detect Stimulus

skin

tongue

nose

touch, pressure,pain,temperature

chemicals in food

chemicals in air

13.1

Sense organs with receptors to detect Stimulus

eye

ear

light

sound

13.1

Sensory (receptor) neurons: Transmit nerve impulses from receptors towards the central

nervous system.

Relay (Intermediate) neurons: Transmit nerve impulses between sensory neurons and motor

neurons.

Motor (or effector) neurons: Transmit nerve impulses away from the central nervous system to

the effectors (muscles or glands).

1

2

3

1

2

3

13.1

Nerve cell is known as neurone.

They transmit information as nerve impulses (signals).

There are three different types of neurones, each with a slightly different function.

(a) Sensory (receptor) neurone (b) Relay (intermediate) neurone

(c) Motor (effector) neurone

Nerve Cell13.1

Nervous System Pathway:

Receptors (in sense organs)

Stimulus

Central Nervous System

(e.g brain or spinal cord)

Effector(e.g muscles,

glands)

detected by

13.1

Nervous System Pathway:

Receptors (in sense organs)

Stimulus

Central Nervous System

(e.g brain or spinal cord)

Effector(e.g muscles,

glands)

detected by

(i) Sensory neurone

(ii) Relay neurone

(iii) Motor neurone

Involuntary actions: automatic actions Not under control of

the will E.g. heartbeat,

peristalsis, breathing, blinking

13.1

Voluntary actions: under conscious control

(may or may not involve sensory neurone) Intelligent responses Involve processing of information and

conscious decisions E.g. get up in morning, have breakfast, go

out or stay indoors etc......

13.1

Coordination & Responses

Chapter 13.2: Reflex Action

Prepared By, Mrs Yap-Wong Fui Yen 2014Prepared By, Mrs Yap-Wong Fui Yen 2014

A direct and immediate response to a specific stimulus without conscious control.

Inherited, do not need to learn; protect body from harm. Simplest form of response

Reflex arc – shortest pathway by which nerve impulses travel from receptor to effector during a reflex action.

What is a Reflex Action?13.2

What is a Reflex Action?

S : Specific stimulus

I : Immediate response

S : Shortest path

I : Involuntary action

13.2

Prepared By, Ms Wong

“ Stimulus “ (sudden

tapping)

CNS (spinal cord)

Effectors(muscles)

(i) sensory neurone

(iii) motor neurone

(ii) relay neurone

Receptors (stretch receptors)

13.2

2 types : Spinal reflex - nerve impulses pass through spinal cord

and do not involve the brain

Examples: knee-jerk, sudden withdrawal of hand touching a hot object, sharp

pain

Cranial reflex - nerve impulses pass through the brain

Examples: pupil reflex, sudden blinking of eyes when object moves past them

yawning secretion of saliva, tearing , sneezing, coughing, breathing

13.2

Knee Jerk Type - Spinal reflex Stimulus - Extension of knee tendon

e.g. knee bends; knock on knee cap.

Response - Contraction of thigh muscle causing leg to straighten

Survival value - Ensure leg will support body when standing or walking

13.2

Pupil Reflex Type - Cranial reflex

Stimulus - Bright light falling on eyes

Response - Contraction of circular muscles of iris to reduce pupil size

Survival Value - To protect eyes from damage due to excessive exposure to light

13.2

microQuestion 1.Describe the similarities and

differences between a voluntary action and a reflex action.

Prepared By, Mrs Yap

13.2

Coordination & Responses

Chapter 13.3: Nervous Pathway in Reflex Action

Prepared By, Mrs Yap-Wong Fui Yen 2014Prepared By, Mrs Yap-Wong Fui Yen 2014

Prepared By, Ms Wong

What are the sequence of events which take place during a reflex action?

13.3

Sequence of events :

1. The heat on the object stimulates the nerve endings (receptor) in the skin.

2. Impulses are produced and travel along the sensory neurone to the spinal cord.

3. In the spinal cord, the impulses are transmitted first across a synapse to a relay neurone, and then across another synapse to the motor neurone.

4. Nerve impulses leave the spinal cord along the motor neurone to the effector.

5. The effector (the muscles) then contracts, causing a sudden withdrawal of the hand.

13.3

Prepared By, Ms Wong

Prepared By, Ms Wong

What happens when your eye is suddenly exposed to a bright surrounding?

13.3

Sequence of events :

1. Light stimulates the nerve endings of the light-sensitive cells in the eye retina.

2. Nerve impulses stimulated and travel along sensory neurone in optic nerve.

3. The nerve impulse transmit from sensory neurone to the relay neurone in the brain.

4. Nerve impulses then transmit across the synapse from relay neurone to the motor neurone.

5. Effector ( iris muscle) contract to control to the pupil size.

13.3

Have you ever felt dazed after bumping your arm, leg or after smashing a finger or toe?

Would you like to know what causes these types of sudden feelings in your body?

microQuestion

2. The diagram shows a nerve pathway involved in a reflex action

13.3

Which structure is a motor neurone?

microQuestion

3. A finger that touches a hot object is quickly taken away from the source of heat.

What is the role of relay neurones in this response?

A) To carry nerve impulses within the spinal cord. B) To generate impulses in the receptors of the finger. C) To link the sense organs to the sensory neurones. D) To pass nerve impulses out to the neurones.

Prepared By, Mrs Yap

13.3

Answer :