Nervous System The Neuron is the basic unit of the nervous system. Commonly referred to as a “nerve.” **Nucleus **Cell body **Schwann cells **Nodes of Ranvier **Dendrites Bonus: label all parts with asterisk **axon **Axon terminals

The neurons connect the brain to the entire body and its parts The neurons connect the brain to the entire body and its parts. But the neurons do not touch each other! **Synaptic cleft or gap is the gap between neurons

Messages are sent from one neuron to the next via chemicals called Neurotransmitters. In this case, the message of pain is being transmitted by a neurotransmitter called “Substance P” **A Neurotransmitter is a chemical released by 1 neuron that has an effect on another neuron Substance P Pain Receptor

Each Neuron has specific receptors for each neurotransmitter, which then relay the message through the axon of the neuron toward the axon terminal.

*During a nerve impulse, there is a reversal of polarity in the axon

Hmwk: p 1009 #1, 4

The Dendrites are the receiving end of the neuron and the axon terminal is the sending end Receives information, carries to cell body Cell body contains nucleus ***Axon is cell extension (conducts action potential) Transmits information away from cell body to the axon terminal Cell has only 1 axon

If the message is being sent to a muscle to contract, the last axon terminal will end at a motor end plate of the target muscle/muscles. That message will stimulate the muscle to contract… This happens in a millisecond. That’s fast!

*Axons are covered with a lipid layer called the myelin sheath ***Myelin sheath increases the speed of nerve impulses or action potential

**Resting Potential Resting cell membrane is more permeable to potassium ions than sodium ions More positive charges leave the cell than enter it ***Sodium ions are more concentrated outside the cell *Potassium ions are more concentrated inside the cell *The inside of the cell is negatively charged The outside of the cell is positively charged

***Brain *Visual information is processed by the occipital lobe in the brain **Cerebral cortex is the outer layer of the cerebrum *Cerebellum smoothes and coordinates movements like walking and running *The brain stem connects the cerebral hemisphere with the cerebellum

**Diencephalon *Contain important relay centers Made up of the thalamus and hypothalamus

**Spinal Cord Like an interstate, it carries information back and forth The outer Composed of a white matter (insulates) The inner Composed of **gray matter made up of Dendrites, axons, cell bodies but **does not include motor neurons

There are three parts to the nervous system: 1. The Central Nervous System (CNS) a) Brain (includes cranial neurons-so that lobes of the brain can talk to each other) b) Spinal Cord (includes spinal neurons, which relay messages from the body’s extremities and internal organs to the spinal cord)

There are three parts to the nervous system *The Central Nervous System (CNS) *Is made up of the Brain and the spinal cord

2. ***The Peripheral Nervous System (PNS) *This connects the brain and spinal cord to the rest of the body **Sensory receptor is a neuron that detects stimuli * Two principal components of the peripheral nervous system are : *Sensory *Motor **Includes Spinal Nerves (spinal cord = CNS)

*Somatic Nervous system part of the PNS *Contains neurons that control skeletal muscle **Afferent Neurons Collect information from the body and transmit it toward the CNS Includes neurons in the ear, **eyes (optic nerve) Efferent Neurons Transmit information away from the CNS. **Included in the PNS: Somatic system Autonomic system Sensory system

3. **Autonomic Nervous System Involuntary muscle contractions in digestive and cardiovascular systems. This happens ”automatically!” You do not have to think about it. **A spinal reflex is an example of an involuntary movement

Autonomic nervous system has two parts: *Sympathetic division *In times of stress it is the sympathetic nervous system is activated Parasympathetic division

Hmwk Pg 1015 #1,3, 4, 5

Sensory system Sense organs Eyes, ears, nose, mouth, and skin

**Hearing and Balance Auditory canal Connect to external ear with tympanic membrane (eardrum) **Tympanic membrane **Vibrates in response to sound waves Eustachian tube Opening to throat Equalizes pressure on both sides of the tympanic membrane

*Cochlea Inner ear *Coiled tube essential to hearing **Contain hair cells are important for hearing and balance *Semicircular canals *Essential for balance

**Auditory information **Travels to the brain stem  thalamus  cerebral cortex

Vision Retina Pupil Iris Lens Rods Cones Light sensitive inner layer of eye Receives image formed by lens Transmits them through optic nerve to the brain Pupil Opening at center of iris Controls amount of light that enters the eye Iris Colored circular part of eye Lens Convex transparent structure in the eye that focuses light on retina Rods Detects dim light Plays major role in non-color and night vision Cones Distinguishes color Sensitive to bright light Bonus: Rods detect dim light. Impt for night vision Cones distinguishes color, sensitive to bright light

*Photoreceptors in the retina convert light energy to electrical signals

Taste and Smell Pressure and Temperature