Download Nervous System and Hormones

Study Guide Nervous System and Hormones Chap 29-30
Nervous System:
1. The nervous system is the main system to communicate and coordinate body activities by
sending electrical impulses. Nervous system forms a communication network in whole body.
2. Central nervous system CNS consists of Brain and Spinal Cord.
3. Peripheral nervous system PNS consists of nerves bringing information into or out of Central
nervous System.
4. Specialized nerve cells are called Neurons.
5. Sensory neurons bring information from sense organs like eyes to CNS.
6. Motor neurons take information from CNS to effectors like muscles or glands.
7. Inter-neurons receive information from sensory neurons and integrate it, interpret the meaning
and pass instructions to motor neurons to act.
8. A neuron has a cell body. Many smaller branched appendages are called Dendrites. Dendrites
bring in information (nerve impulse) to the cell body. A single longer appendage is called Axon. It
takes information away from cell body. It branches at the end into terminal knobs. A terminal
knob secretes a chemical called Neurotransmitter in the gap to the next neuron or muscle
membrane.
9. Resting Potential: is when a nerve fiber has more positive ions outside and more negative ions
inside. It is not conducting any electrical impulse. It is Polarisation.
10. Action Potential: is the sudden change on stimulation. Na+ ions move in. Now nerve fiber has
more + ions inside. Action potential or nerve impulse travels from cell body side to terminal
knob side of neuron. When the impulse reaches a part it becomes + inside and the part just
behind it, returns to resting potential, Repolarisation, due to outward movement of K+ ions.
11. Brain: has 3 main parts. Cerebrum is the largest part of brain. It is divided into 2 cerebral
hemispheres. It is the seat of intelligence, imagination, calculations or processing, emotions and
memories. Most of the times we use word brain to mean cerebrum. Cerebellum is the 2nd
largest part of brain and is responsible for maintaining body posture and balance = equilibrium
of body. The remaining part of brain is called Brain Stem. It has Pons and Medulla parts which
have the cardiac and breathing centers to regulate heart beat and rate of breathing.
12. Sensory System: Human body has 5 main sensory organs which collect information about
surroundings. Some receptors also collect internal information like hunger, joint movement etc.
13. Skin: It gives us information about Touch, Pressure, Heat, Cold and Pain. Most receptors in skin
are present inside dermis just below epidermis.
14. Nose: It has special sensory cells which collect information about smells of vapors.
15. Tongue: It has groups of sensory cells called taste-buds. Taste-buds detect 4 main types of taste
salt, sweet, sour and bitter.
16. Eyes: Eyes collect visual information. Front of the eye is transparent to allow light to enter inside
eye. It has to pass through a diaphragm called Iris, the colored part of eye. Iris has an opening at
center called Pupil. If we get out in bright sunlight pupil quickly gets small to reduce the light
entering eye. If we enter a dark room the pupil gets bigger to increase the light entering the eye.
Eyes focus on far and near objects by changing the thickness of lens in the eye. The image is
focused on Retina, the photo-sensitive layer. Retina has cone cells – give us colored vision in
bright light and Rod Cells – give us black and white vision in dim light.
17. Ears: are the sensory organs for hearing and equilibrium. The external ear collect sound waves.
After passing a duct sound wave hit Ear Drum. Ear drum passes vibrations to small bones in
middle ear. These small bones pass vibrations to internal ear. Cochlea a coiled duct has sensory
cells that send impulses to brain. Brain interprets the meaning of sounds. Upper part of internal
ear detects changes in body position and sends impulses to Cerebellum of brain. Cerebellum
with the help of ears maintains balance = equilibrium of the body at rest or during motion.
Hormones:
18. Hormones are chemical messengers secreted by endocrine glands. Hormones travel through
blood to target cells in body.
19. Hypothalamus, Pineal body and Pituitary gland are endocrine glands associated with brain.
20. Thyroid endocrine gland lies in neck region.
21. Adrenal glands lie just above kidneys.
22. Pancreas secretes insulin and glucagon hormones to regulate blood glucose level.
23. 3 hormone control involves Hypothalamus in brain  Pituitary gland below it  thyroid gland
secretes thyroxin hormone. Thyroxin regulates basal metabolic rate of body.
24. Ovaries secrete female hormones and testes secrete male hormones.