Download 6.5 Nerves, Hormones and Homeostasis

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.
2.
3.
4.
Dendrites
Cell body
Axon
Axon
terminal
3 main types of Neurons:
sensory
neuron
relay
neuron
motor
neuron
Conduction of Nerve Impulses:
Online animation
Nerve impulses are conducted along the neuron
Online video
Online animation
Resting Potential: Na/K Pump
+
-
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.
Both Na+ & K+ channels are closed, and the
membrane’s resting potential is maintained.
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
Synaptic Transmission
animation
http://www.blackwellpublishing.com/matthews/nmj.html
Synaptic Transmission
animation
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]
Endocrine System:
Major endocrine glands.
(Male on the left, female on the right.)
1. Pineal gland
2. Pituitary gland
3. Thyroid gland
4. Thymus
5. Adrenal gland
6. Pancreas
7. Ovary
8. Testes
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
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
Homeostasis: Thermoregulation
Thermoregulation is an example of homeostatic mechanism.
Homeostasis: Thermoregulation in endotherms
The body must balance its heat budget
Heat is gained:
 by conduction from warm air surrounding the body
 by the body’s metabolic activity which generates heat e.g. when
muscle move
Heat is lost:
 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
behaviour
e.g. wearing different clothes, seeking shade
Homeostasis: Thermoregulation in endotherms
animation
epidermis
Homeostasis: Thermoregulation in endotherms
Homeostasis: Thermoregulation in endotherms
Homeostasis: Thermoregulation in endotherms
animation
animation
animation
Glucose Homeostasis:
animation