1. Nerves, Hormones, and Homeostasis
Topic 6.5

2. Topic Assessment Statements-Nerves
6.5.1-State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses.
6.5.2-Draw and label the structure of a motor neuron.
6.5.3-State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.
6.5.4-Define resting potential and action potential (depolarization and repolarization)
6.5.5-Explain how a nerve impulse passes along a non-myelinated neuron
6.5.6-Explain the principles of synaptic transmission.

3. 6.5.1
State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses.
Neurone=Neuron

4. What Does This Mean?
Central Nervous System (CNS)-the brain and the spinal cord
Peripheral Nervous System (PNS)-outlying nerves conducting impulses to and from the CNS
Neuron-nerve cell; three types

5. 6.5.2-Draw and label the structure of a motor neuron
(Soma)

6. 6.5.3
State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.
No difference in structure of the three types

7. 6.5.4-Define resting potential and action potential
Resting Potential-the usual state of a nerve, when it is ready to send an impulse
Called potential because it refers to the electric potential of the neuron membrane
This resting state has Sodium ions (Na+) outside the membrane and Potassium ions (K+) inside.
The Resting Potential for a human neuron is about -70 millivolts
This means the inside of the membrane is more negatively charged than the outside

8. 6.5.4
Action Potential-the state of the nerve when its polarity has been switched. The nerve has been depolarized.
At the Action Potential, Na+ and K+ are both on the inside of the neuron.
The intervals during which the neuron is at the action potential form the impulses that travel along the nerves

9. WARNING!!! Dense Topic!!!

10. 6.5.5-Explain how a nerve impulse travels along a non-myelinated neuron
In its resting state, a neuron is at resting potential.
If a sensor is stimulated, this causes the nerve connected to it to change.
Chemically-controlled channel proteins in the main neuron body open, letting Na+ ions in.
This makes the membrane potential of the neuron increase.
If the potential voltage increases to a “threshold level,” then further changes take place.

11. 6.5.5
Once the voltage reaches the threshold, voltage-controlled channel proteins open, allowing even more Na+ into the neuron
This increases the charge of the inside of the neuron, depolarizing it and bringing it to its action potential
There are now Na+ and K+ ions in the neuron, so the inside is relatively more positive than the outside
This higher voltage causes more channel proteins to open, so the action potential moves down the neuron

12. 6.5.5
At the Action Potential, the Na+ channel proteins close, so Na+ ions stop coming in to the neuron
K+ channels open, and K+ starts to flow out of the neuron
The neuron starts to be repolarized by this flow, and the membrane potential voltage drops
Once the voltage is low enough, the K+ channels close, and the neuron is once again at resting potential
Sodium-potassium pumps move the Na+ and K+ back to their original locations: Na+ outside and K+ inside

13. 6.5.5

14. 6.5.5 Animation

15. What if the threshold isn’t reached?
If the voltage does not increase enough to trigger an action potential, the Na+ ions are simply pumped back out, and the neuron returns to resting potential
To be felt, a stimulus must be great enough to trigger an impulse

16. Leaving the IB Path-What does Myelin do?
Myelin is a fatty compound that surrounds the axon, except in the Nodes of Ranvier
There are no channel proteins where myelin sheaths surround the axon
Instead of the whole axon moving to action potential, only the area around the node does so
This greatly speeds and eases the process of moving an impulse down the nerve

17. 6.5.6-Explain the principles of synapse transmission
When the opening of channel proteins reaches the end of the axon, Ca2+ diffuses into the neuron
Vesicles containing a neurotransmitter chemical already exist at the axon tail, in swollen areas known as “terminal buttons”
Calcium ions cause the vesicles to merge with the membrane of the axon, releasing the chemical into the “synaptic cleft”, between the button and another neuron

18. 6.5.6
The neurotransmitter bonds to a protein channel on the next neuron, opening it and allowing Na+ ions in, continuing the impulse
The neurotransmitter is broken down by enzymes

19. 6.5.6 Diagram

20. Review
6.5.1-State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses.
6.5.2-Draw and label the structure of a motor neuron.
6.5.3-State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons.
6.5.4-Define resting potential and action potential (depolarization and repolarization)
6.5.5-Explain how a nerve impulse passes along a non-myelinated neuron
6.5.6-Explain the principles of synaptic transmission.

21. Define resting potential and action potential. (2 marks)
-Resting potential is the membrane potential of a neuron membrane when not conducting an impulse.
-Action potential is the state of the cell membrane while conducting an impulse

22. In a nerve impulse, what happens at the site following the highest point of the action potential? (1 mark)
A. Voltage-gated sodium ion channels open and Na+ is pumped in.
B. Voltage-gated sodium ion channels open and Na+ diffuses out.
C. Voltage-gated potassium ion channels open and K+ is pumped out.
D. Voltage-gated potassium ion channels open and K+ diffuses out.
- Correct answer: D

23. What is the role of active transport in the transmission of nerve impulses by neurons? (1 mark)
A. Propagates an action potential by pumping sodium ions across the membrane out of the neuron.
B. Propagates an action potential by pumping sodium ions across the membrane into the neuron.
C. Initiates the action potential needed for the transmission of an impulse by pumping calcium ions out of the endoplasmic reticulum.
D. Establishes the resting potential needed for the transmission of an impulse by pumping sodium and potassium ions across the membrane.
-Correct answer: D

24. The Endocrine System (6.5.7)
Hormone are molecules secreted by certain glands that have a direct affect on your body.
State that the endocrine system consists of glands that release hormones that are transported in the blood.

25. Exocrine Glands
Exocrine Glands are glands that secret their product and is lead into an external environment (not hormone producing yet still apart of the endocrine system).
ex) Salivary Glands, Sweat Glands, Stomach

26. Three Types of Hormones
Steroids
Peptides
Amines
Difference between the three is based on their structure.
When the hormone is releases it travels to target cell with correct receptor for that hormone.

27. Steroids
These hormones are lipids derived from cholesterol (hydrophobic)
Ex) Testosterone

28. Peptides
These are short chains of amino acids (most hormones are these)
Ex) Amylin (secreted by beta cells in the pancreas)

29. Amines These are smaller structures with amine groups.
Ex) Histamine (controls immune responses to allergies)

31. The Homeostasis Commandments
Maintaining internal environment between limits
Importance of blood pH
Carbon dioxide concentration
Blood glucose concentration
Maintaining levels of variables, Body temperature and water balance
Negative feedback mechanisms
Roles of heat in blood, hypothalamus, sweat glands, skin arterioles and shivering

32. Break it Down Now Normal Limits Blood pH: 7.35
Carbon dioxide concentration: 390ppm per V
Blood glucose concentration: 90mg/dl
Body temperature: 37oC
Water balance

33. Important Vocabulary
Homeostasis: The process of maintaining the internal conditions of an organism between acceptable limits.
Hypothalamus: A part in the brain that controls many automatic functions in the body, most important is the body’s “internal thermostat”.
Negative feedback mechanisms: are self-regulating responses to changes experienced by a system or organism, usually due to external influences.
Normal limits: The forms the body takes when its regulated such as temperature (37oC).

34. How your body warms itself

35. How your body cools itself

36. Controlling Blood Glucose Levels (6.5.11)
This is a type of homeostasis
Controlled by the pancreas (pancreatic islet)
Constantly Being regulated (see-saw)

37. Hepatic Portal Vein
Once blood has taken the nutrients (glucose) from the digestive system, it travels through the hepatic portal vein.
This takes all blood to the liver before anywhere else in the body.
Liver cells called hepatocytes must act on the blood first to control the level of glucose in your blood.
The liver is the “Control Center” when deciding if there is too much or too little glucose in your blood.

38. Some Pictures...

39. Pancreas Beta (β) Cells (Blood Glucose levels too high)
These produce insulin (hormone) when liver decides there is too much glucose in the blood.
Insulin allows protein channels in your cell membranes to open and allow the glucose to enter your cells through facilitated diffusion (in your muscle cells).
Insulin also makes the hepatocytes cells take in glucose (monosaccharide) and turn it into glycogen (a polysaccharide) to be stored in their cytoplasm.

40. Pancreas Alpha (α) Cells (Blood Glucose levels too low)
Produces hormone called glucagon.
This allows the body to break down the glycogen in your liver and muscle cells back into glucose.
This increases your blood glucose levels.

41. Diabetes (6.5.12)
A disease characterized by hyperglycaemia (high blood sugar).
Your body's β cells can't produce a sufficient amount of insulin.

42. Type 1 Diabetes Insulin - Dependant disease
Autoimmune disease, the body's immune system attacks the β cells and destroying them.
Most often developed in children, but can develop at any age.
Must take insulin shots externally.

43. Type 2 Diabetes
Non-Insulin-Dependant Disease, Where the body's cells no longer respond to insulin (they were overused).
This is the most common type of Diabetes (90% of diabetics).
Linked to genetic history, obesity, lack of exercise, age, and certain ethnic groups.
If you family has a past with Diabetes, you are more susceptible to it.
Controlled by diet.

44. Serious Affects of Diabetes w/ some Facts
Kidney failure, nerve damage, increases of cardiovascular disease, poor wound healing, damage to retinas leading to blindness.
Ethnic groups affected by type 2 diabetes the most are African Americans, Hispanic/Latino Americans, American Indians, Asian Americans, and Pacific Islander Americans