(I)GCSE Topic 2.85

Describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

Receptor: Heat sensor in the skin
- The impulse travels to the spinal cord along the sensory nerve.
- In the spinal cord the impulse is passes on to the relay nerve.
- This passes the impulse on to the MOTOR NERVE. 

Effector: Arm muscles
- The motor nerve carries the impulse to the muscle in the arm.

Response: Muscles 

- Contract to remove the hand from the hot surface.  

(I)GCSE Topic 2.84

Understand that Stimulation of Receptors in the sense organs sends electrical impulses along nerves into and out of the Central Nervous System(CNS), resulting in rapid responses.

- Nervous system sends electrical messages along nerves to and from different parts of your body and they tell your body what to do.

- Sense Organs act as Receptors to detect change. They send messages to the CNS along the sensory nerves. 

- Nerve cels are different from other cells. They both have cell membranes; cytoplasms and nucleus but they are of a different shape. 

- Part of the cell is stretched out to form the AXON which can be over a metre long. 

- The messages that nerves carry are called NERVE IMPULSES which are electrical signals that pass very quickly along the axon of the nerves. 

- 

(I)GCSE Topic 2.83

Recall that the Central Nervous System consists of the Brain and Spinal Cord and is linked to sense organs by nerves.

- The main parts of the Nervous System consist of the Brain and Spinal Cord; forming the Central Nervous System (CNS). 

- Both are made of delicate nervous tissues. 

- The Brain is protected by the skull. 

- The Spinal Cord is protected by you back bone. 

- The CNS is connected to difference parts of the body by nerves; each nerve is made up of lots of Nerve Cells/ Neurons. 

(I)GCSE Topic 2.82

How responses can be controlled by Nervous or by Hormonal Communication and the differences between the two systems

The Nervous System 

- Controls your actions and co-ordinates the different parts of your body so that they are able to bring around the correct responses. 

- Co-ordinates our muscles so we able to do things such as blink, breath, or swallow. 

The Hormonal System 

- Chemicals produced by glands in the body and are carried around by the blood.

- They also tell the body how to respond. 

Differences

- Nervous System passes along information as electrical impulses. 

- Hormonal System passes information as chemical messengers in the blood.

- Nervous System effects are rapid and short-lived. 

- Hormonal System effects are usually slow and long-lasting. 

- Nervous System effects particular organs. 

- Hormonal Systems effects the whole of the body.

- Nervous Systems often involve reflexes. 

- Hormonal Systems involve the control of growth, development, metabolism and reproduction.

(I)GCSE 2.77 c) Osmoregulation

- Regulation of body water content = Homeostasis

 - Homeostasis is maintaining constant conditions

- Regulation is of body water content, largely making up Plasma and Tissue Fluids

- Homeostasis of water body content = OSMOREGULATION

- Major receptor in water body content = hypothalamus of the brain

- Stimulus to Hypothalamus = blood

- Effector = kidney

- Output of kidney = filtered blood

(I)GCSE 2.77 b) Thermoregulation

- Negative feedback loop = control and maintaining constant conditions

- Co-ordinator = body temp of 37 - 38 d.c.

- Receptor of body temperature = Hypothalamus of the brain

- Hypothalamus responds to temperature of the body/ blood

- Change in temperature brought about by receptor = skin

- Response = increase/ decrease in body temperature

(I)GCSE 2.76 Sensitivity

- Organisms are able to respond to changes in the environment. 

- MRS. NERG S = Sensitivity

- Sensitivity = characteristic when organisms respond to changes in the environment.

Types of changes in the environment: 

: light level 

: temperature 

: pressure level 

:chemicals 

- Organisms are required to have receptors in order to detect the changes.

- Organisms have effecters such as muscles or glands to respond.

- Response show that organisms are able to survive the changes in the environment.