Nerves & Hormones

1. Nerves & Hormones

2. Nervous System: • Central Nervous System: • (The center of integration and control) • 1. The brain • 2. The spinal cord • Peripheral Nervous System: • The nervous system outside of the brain and spinal cord

3. Basic Nerve cell Structure: Neurons • Dendrites • Cell body • Axon • Axon terminal

4. 3 main types of Neurons: sensory neuron motor neuron relay neuron

5. Conduction of Nerve Impulses: Online animation

6. Nerve impulses are conducted along the neuron

7. Online video Online animation

8. Resting Potential: Na/K Pump + -

10. The Action Potential Activation gates of the Na+ channels are open, but the K+ channels remain closed. Na+ ions rush into the cell, and the interior of the cell becomes more positive. Na+ close and potassium channels open. K+ ions leave the cell and the loss of positive charge causes the inside of the cell to become more negative than the outside. A stimulus opens some Na+ channels. If the Na+ influx achieves threshold potential, then additional Na+ gates open, triggering an action potential. Na+ channels are closed, but the slower K+ remain open. Within a millisecond, the resting state is restored. Both Na+ & K+ channels are closed, and the membrane’s resting potential is maintained.

11. Nerve impulse along a non-myelinated neuron animation

12. Synaptic Transmission animation http://www.blackwellpublishing.com/matthews/nmj.html

13. Synaptic Transmission animation

14. Explain how a nerve impulse passes along the membrane of a neuron • resting membrane is polarized; • interior is –70 mV/negative relative to outside; • more sodium ions outside than inside; • more potassium ions inside than outside; • disturbance of membrane opens sodium ion channels; • sodium ions rush to inside of cell; • causing depolarization; • sodium ion channels shut; • potassium ion channels open; • potassium ions rush out; • helping to restore polarized state of membrane; • sodium-potassium pumps maintain polarity; • process repeated along the length of neuron / sodium ions diffuse between region with an action potential and the region at resting potential; [8 max]

15. Endocrine System: • Major endocrine glands. • (Male on the left, female on the right.) • Pineal gland • Pituitary gland • Thyroid gland • Thymus • Adrenal gland • Pancreas • Ovary • Testes

16. Hormones: • Organic substances • Produced in small quantities • Produced in one part of an organism (an endocrine gland) • Transported by the blood system • To a target organ or tissue where it has a profound effect

17. Homeostasis: • Homeostasis involves maintaining the internal environment • (tissue fluid, blood) between limits. • Examples: • Blood pH • Blood carbon dioxide levels • blood glucose concentration • body temperature • water balance

18. Homeostasis: Thermoregulation Thermoregulation is an example of homeostatic mechanism.

19. Homeostasis: Thermoregulation in endotherms The body must balance its heat budget • by conduction from warm air surrounding the body • by the body’s metabolic activity which generates heat e.g. when muscle move • by conduction and radiation to cold air (or water) • by evaporation of sweat from the body surface (c.f. properties of water) • Humans can also affect their body temperature by changing their behavioure.g. wearing different clothes, seeking shade Heat is gained: Heat is lost:

20. Homeostasis: Thermoregulation in endotherms animation epidermis

21. Homeostasis: Thermoregulation in endotherms

22. Homeostasis: Thermoregulation in endotherms

23. Homeostasis: Thermoregulation in endotherms

25. animation

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27. Glucose Homeostasis:

28. animation