Human Responses

1. Human Responses Nervous system Endocrine System (hormones)

2. The Nervous System • Organisms must be aware of what is happening around them,as this affects their survival chances. • Co-ordination of an organism’s activities is carried out by thenervous system and the endocrine system. • A nervous system allows an organism to detect and respondto stimuli in its internal or external environment. • A stimulus is any change in your internal or external environment e.g. a flash of light, a noise, increase in blood concentration.

3. The nervous system relies on electrical signals, carried byspecialised cells [neurons], and is involved in fastresponses. • The central nervous system(CNS) is your brain and spinalcord. • The brain keeps a check on internal organs and activities, such as the level of carbon dioxide orwater in theblood. • The peripheral nervous system (PNS) is the nerves branching outfrom the CNS to all parts of the body.

4. NS ----- Co-ordination & Response • A stimulus is any change in your .....environment…. • A receptoris a nerve cell that detects the stimulus • A neuron is a specialised cell that carries electrical messages(impulses) around the body. • An impulse is an electrical message that is carried along aneuron.

5. The Brain • The brain is composed of over 100 billion neurons, eachreceiving messages simultaneously from thousands of otherneurons. • The brain is protected by the skull bones, meninges (threemembranes) and cerebrospinal fluid.

6. The cerebrum is our conscious brain, with different parts havingdifferent jobs to do – memory, emotion, learning…. cerebrum hypothalamus • The hypothalmus controls homeostasis – osmoregulation pituitary • The pituitary ‘[master] gland secretes hormones that stimulateother glands to release their hormones.

8. Medulla oblongata • The cerebellum = co-ordination, movement, balance cerebellum • The medulla oblongata co-ordinates involuntary, automaticprocesses—such as breathing, heartbeat.

9. 4) The brain decides to move away the hand 3) Here another sensory neuron carries the signal to the brain 5) This impulse is sent by MOTOR NEURONS to the hand muscles (the effectors) via the spinal chord… 2) The impulse is carried by SENSORY NEURONS to the spinal chord 1) Receptors in your skin detect a stimulus 6) Which then moves the hand away Stimulus Receptor Sensory NeuronCoordinator Motor Neuron Effector Response Conscious actions A conscious action is one where the brain makes a considered response. Here’s what happens:

10. There are three types of Neuron : • Sensory neuron –carries messages from the sense organ tothe central nervous system (CNS). • Interneuron –connects sensory and motor neurons and socarries messages within the CNS. • Motor neuron –carries impulses from the CNS to muscles andglands.

13. Cell body location within CNS or not Where are the synaptic knobs? Cell body position Direction of impulse Where are the synaptic knobs?

14. Differences between Motor and Sensory Neuron • Direction of impulse – to or away from CNS • Position of cell body – at start or along length • Location of cell body - within CNS or outside CNS in ganglion

15. Neuron structure • The cell body contains the nucleus and other organelles andproduces neurotransmitter chemicals. • A dendrite is a short fibre that receives impulse (information) and carries ittowards the cell body. • The axon is a very long fibre that conducts impulses away from the cell body.

16. Many Schwann cells wrap their fatty cell membranes around an axon, forming a myelin sheath. • The myelin sheath insulates the neuron from electrical impulses flowing in other neurons. • Synaptic Knobs (containing neurotransmitter vesicles) – produce, store and release neurotransmitter chemicals e.g acetylcholine

17. LEARNING CHECK • Name the 5 main parts of the brain and one function of each. • How is the brain protected? • What is meant by “conscious action”? • What does the term “involuntary” mean? • Distinguish between the cerebrum and the cerebellum.