Nerves, Hormones & Homeostasis Stephen Taylor i-Biology.net

Assessment StatementsObj State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that carry rapid electrical impulses Draw and label a diagram of the structure of a motor neuron 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 Define resting potential and action potential (depolarisation and repolarisation) Explain how a nerve impulse passes along a non-myelinated neuron Explain the principles of synaptic transmission State that the endocrine system consists of glands that release hormones that are transported in the blood State that homeostasis involves maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and water balance Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms Explain the control of body temperature, including the transfer of heat in the blood, and the roles of the hypothalamus, sweat glands, skin arterioles and shivering Explain the control of blood glucose concentration, including the roles of insulin, glucagon and α and β cells Distinguish between type I and type II diabetes. 2 Assessment statements from: Online IB Biology Subject GuideOnline IB Biology Subject GuideCommand terms:

Diagram from: The Motor Neuron nerve impulse

In a neuron K + is highest inside the cell Na + is highest outside the cell This gradient is maintained by Na + /K + pump. It pumps 3 Na + out for every 2 K + it pumps in. ATP required.

Selective Ion channels allow diffusion of ions When a neuron is resting more K + ion channels are open allowing K + to travel out. This creates a negative charge inside the cell. 140 mM K + inside the cell & 5 mM K + outside the cell

Gated ion channels open and close in response to a stimuli This changes the membranes permeability to certain ions like Na + causing Na + to flow into the cell Any net movement of positive or negative charge across the membrane will result in a membrane potential (voltage across the membrane) Depolarization = Reduction of the magnitude of the membrane potential

to -80 mV

From McGraw Hill: Click here to play video

click here to see an animation of synapse transmission

The Endocrine System A stimulus is received and processed. Hormones are secreted directly into the blood. They are carried to the target tissues (the place of intended action). The action of the hormone changes the condition of the tissue. This change in monitored through feedback. Most hormonal change results in negative feedback. Key endocrine glands: 1.Pineal glandPineal gland 2.Pituitary glandPituitary gland 3.Thyroid glandThyroid gland 4.ThymusThymus 5.Adrenal glandAdrenal gland 6.PancreasPancreas 7.Ovary (female)Ovary (female) 8.Testes (male)Testes (male) Endocrine glands from:

The Endocrine System A stimulus is received and processed. Hormones are secreted directly into the blood. They are carried to the target tissues (the place of intended action). The action of the hormone changes the condition of the tissue. This change in monitored through feedback. Most hormonal change results in negative feedback. Key endocrine glands: Endocrine glands from:

Temperature Regulation Warm Blooded – can regulate internal body temperature regardless of environmental temperature. Cold Blooded - can not regulate body temperature internally. Must use environment to regulate temperature Hibernation- a time when metabolic activity is greatly decreased

4 Ways to Exchange Heat with the Environment 1.Conduction: direct transfer heat between molecules of the environment and the body surface. Ex. Sit in a pool 2. Convection: transfer of heat by air movement or liquid past a surface Ex. Fan 3. Radiation: emit electromagnetic waves produced by all objects warmer than absolute zero. No direct contact.

4 Ways to Exchange Heat with the Environment 4. Evaporation: loss of heat from surface of a liquid that is losing some molecules as gas. ex. sweating

Ways of Maintaining Body temperature 1.Adjust rate of heat exchange between animal and surrounding. a. insulation ex. Hair, feathers or fat b. adaption of circulation ex. Vasoconstriction – decrease in diameter the blood vessel decreasing the amount of blood flow Vasodilation - increase in diameter of the blood vessel increasing the amount of blood flow

Ways of Maintaining Body temperature c.arrangement of arteries and veins ex. Opening and closing of capillaries near to skin surface 2. Cooling and evaporative heat loss Activation of sweat glands to release more sweat Evaporation of perspiration will take heat with it.

Ways of Maintaining Body temperature 3. Behavioral Response a. Putting on warmer clothes b. Ingesting hot liquids c. Changing posture to decrease surface area d. Increasing physical activity 4. Change in rate of metabolic heat production a. When temperature is low hypothalamus will trigger release of thyroxine which will increase the metabolic rate

How does the body maintain temperature homeostasis?

How does the body maintain glucose homeostasis?

GLUCOSE REGULATION The endocrine gland involved in glucose regulation is the pancreas The specific part is the Islets of Langerhan. It is composed of two different types of cells. β cells (beta) that secrete the hormone insulin α cells (alpha) that secrete the hormone glucagon

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