Nervous System Neurons – composed of dendrites, axons, and cell bodies Synapse



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Exploring Creation through General Science

Module 16: The Human Nervous System

Nervous System

Neurons – composed of dendrites, axons, and cell bodies

Synapse – gap between the axon of a neuron and the receiving cell

Neuroglia – support neurons by preforming various tasks so neurons can do their job



**Know Figure 16.3 for test** (see Neuron handout)

Parts of the Neuron:

  • Dendrites – conduct electrical signals towards the neuron’s cell body

  • Axons – direct electrical signals away from the neuron’s cell body

Tasks of Neurons:

  1. Neurons pass signals to other neurons

  2. Neurons pass signals to muscle or gland cells

  3. Neurons receive signals, process the information, and send out new signals to other neurons

Neurotransmitter – chemicals that travel across the synapse, transmitting a signal from the end of an axon to the receiving cell

Two parts of the Nervous System:

  • Central Nervous System (CNS) – includes the brain and spinal cord

  • Peripheral Nervous System (PNS) – includes all nerves that run off of the spinal cord and go to the body

Cerebrospinal fluid:

  • Surrounds brain and spinal cord

  • Colorless fluid that contains chemicals that have many functions

  • Includes lymphocytes to fight infection

  • Main function is to protect brain and spinal cord

***Know Figure 16.5 (see Brain handout to study)***

Functions of some parts of the brain:

  • Cerebrum – deals with “higher-level” brain functions

  • Gray matter – composed almost exclusively of the cell bodies of neurons

  • White matter – found under gray matter, lighter color is from myelin which covers axons

  • Corpus callosum – allows the two hemispheres of the brain to communicate with each other

  • Brain stem – controls basic functions like breathing, heart rate and the pressure which is used to pump blood

  • Hypothalamus – (in addition to controlling pituitary gland) regulates thirst, hunger and body temperature

Blood – Brain barrier:

  • Capillaries in brain are different than the rest of the bodies

  • No gaps between the cells

  • Keeps blood from exposing the brain cells to many harmful chemicals

  • Not ALL toxins are held back by this barrier

Deeper look at the Peripheral Nervous System

Nerve groups:

Three main divisions of the PNS (NEED TO KNOW FULL definitions of these:

  • Autonomic nervous system – the system of nerves which carries instructions from the CNS to the body’s smooth muscles, cardiac muscle and glands

  • Sensory nervous system – the system of nerves which carries information from the body’s receptors to the CNS

  • Motor nervous system – the system of nerves which carries instructions from the CNS to the skeletal muscles

Two parts of the autonomic nervous system:

  • Sympathetic division – increases the rate and strength of the heartbeat and raises the blood pressure

  • Parasympathetic division – slows the heart rate and lowers the blood pressure

Sense of Taste

***know handout with tongue and taste areas to study***



Papillae – bumps on tongue

Taste buds – found at base of papillae and are sensitive to certain chemicals, making us sensitive to: sweet, sour, salty, bitter and umami (savory or meaty taste)

Sense of Vision

***Know Figure 16.7 (or human eye handout to study)***



Ciliary muscle – deforms the lens in the eye to adjust focus

Optic nerve – transmits the information from your eye to your brain

Sense of Hearing

***Know Figure 16.9 (see ear handout and study)***



Cochlea – converts the rocking motion of the ossicles into electrical signals that the brain interprets as sound

Ossicles – 3 bones found in the middle ear

Overall

Many say “we use less than 10% of our brains” – clearly this is NOT true. If a small portion of your brain was removed it would effect the person GREATLY


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