Unit 5 Biology Aqa

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Unit 5 Biology notes


Section 9.1 – Sensory Reception3
Section 9.2 – Nervous Control4
Section 9.3 – Control of heart rate5
Section 9.4 – Role of receptors6
Section 10.1 – Coordination8
Section 10.2 – Neurons10
Section 10.3 – The nerve impulse11
Section 10.5 – The speed of a nerve impulse12
Section 10.6/10.7 – Structure and function of the synapse / Transmission across a synapse13 Section 11.1 – Structure of skeletal muscle15
Section 11.2 - contraction of skeletal muscle17
Section 12.1 – Principle of homeostasis19
Section 12.2 - Thermoregulation20
Section 12.3/12/4 – Hormones and the regulations of blood glucose/Diabetes and its control22 Section 13.1 – The principles of feedback mechanisms24
Section 13.2 – The oestrous cycle25
Section 14.1 – Structure of ribonucleic acid26
Section 14.2 – Polypeptide synthesis – transcription and splicing27 Section 14.3 – Polypeptide synthesis – translation28
Section 14.4 – Gene mutation29
Section 15.1 – Totipotency and cells specialisation31
Section 15.2 – Regulation of transcription and translation32 Section 16.1 – Producing DNA fragments33
Section 16.2 – In vivo gene cloning – the use of vectors34 Section 16.3 – In vitro gene cloning – the polymerase chain reaction36 Section 16.4 – Use of recombinant DNA technology37
Section 16.5 - Gene therapy38
Section 16.6 – Locating and sequencing genes40
Section 16.7 - Screening for clinically important genes42
Section 16.8 – Genetic fingerprinting43

Section 9.1 – Sensory Reception

• A stimulus is a detectable change in the internal or external environment of an organism that produces a response. • The ability to respond to a stimulus increases an organism’s chances of survival. • Receptors transfer the energy of a stimulus into a form that can be processed by the organism and leads to a response. • The response is carried out by “effectors” which can include cells, tissues, organs and systems.

Taxis – A simple response that’s direction is determined by the direction of the stimulus

An organism can respond directly to a change in the environment by moving its body either:

1. Toward the stimulus (positive taxis)
2. Away from the stimulus (negative taxis)

Kinesis – Results in an increase of random movements

• Organism does not move towards/away from the stimulus • The more intense the stimulus the more rapid the movements • Kinesis is important when the stimulus is less directional such as heat or humidity

Tropism – a growth movement of part of a plant in response to a directional stimulus

Positive phototropism – shoots/leaves
Positive Geotropism – roots

Section 9.2 – Nervous Control

Nervous organisation

The nervous system can be thought of as having two main divisions:

1. The central nervous system (CNS) – brain and spinal cord 2. The peripheral nervous system (PNS) – Made up of pairs of nerves that originate either from the brain or the spinal cord

The peripheral nervous system

This is divided into:
• Sensory neurons which carry impulses away from receptors to the CNS • Motor neurons which carry nervous impulses from the CNS to effectors

The spinal cord is a column of nervous tissue

A reflex – involuntary response to a stimulus (you do stop to consider an alternative)

The pathway of neurons involved in a reflex is called a reflex arc.

Reflex arcs contain just 3 neurons:
1. A sensory neuron
2. An intermediate neuron
3. A motor neuron

There are several stages of a reflex arc:
1. Stimulus
2. Receptor
3. Sensory neuron
4. Synapse
5. Coordinator (intermediate neuron)
6. Synapse
7. Motor neuron
8. Effecter
9. Response

Importance of the...
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