Nerves & Hormones

Nervous System:

1. Central Nervous System:(The center of integration and

control)1. The brain 2. The spinal cord

2. Peripheral Nervous System:

The nervous system outside of the brain and spinal cord

Basic Nerve cell Structure: Neurons

1. Dendrites

2. Cell body

3. Axon4. Axon

terminal

sensory neuron

relay neuron

motor neuron

3 main types of Neurons:

Conduction of Nerve Impulses: Online animation

Nerve impulses are conducted along the neuron

Online animation

Online video

Resting Potential: Na/K Pump

+

-

The Action Potential

Both Na+ & K+ channels are closed, and the membrane’s resting potential is maintained.

A stimulus opens some Na+ channels. If the Na+ influx achieves threshold potential, then additional Na+ gates open, triggering an 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.

Na+ channels are closed, but the slower K+ remain open. Within a millisecond, the resting state is restored.

Nerve impulse along a non-myelinated neuron

animation

http://www.blackwellpublishing.com/matthews/nmj.html

Synaptic Transmission animation

Synaptic Transmission animation

• 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]

Explain how a nerve impulse passes along the membrane of a neuron

Endocrine System:

Major endocrine glands. (Male on the left, female on the right.) 1. Pineal gland2. Pituitary gland 3. Thyroid gland 4. Thymus 5. Adrenal gland 6. Pancreas 7. Ovary 8. Testes

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

Hormones:

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

Homeostasis:

Homeostasis: Thermoregulation

Thermoregulation is an example of homeostatic mechanism.

Homeostasis: Thermoregulation in endotherms

The body must balance its heat budget

by conduction from warm air surrounding the bodyby 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:

Homeostasis: Thermoregulation in endotherms

epidermis

animation

Homeostasis: Thermoregulation in endotherms

Homeostasis: Thermoregulation in endotherms

Homeostasis: Thermoregulation in endotherms

animation

animation animation

Glucose Homeostasis:

animation